Science.gov

Sample records for aircraft noise sources

  1. Temporal Characterization of Aircraft Noise Sources

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.; Sullivan, Brenda M.; Rizzi, Stephen A.

    2004-01-01

    Current aircraft source noise prediction tools yield time-independent frequency spectra as functions of directivity angle. Realistic evaluation and human assessment of aircraft fly-over noise require the temporal characteristics of the noise signature. The purpose of the current study is to analyze empirical data from broadband jet and tonal fan noise sources and to provide the temporal information required for prediction-based synthesis. Noise sources included a one-tenth-scale engine exhaust nozzle and a one-fifth scale scale turbofan engine. A methodology was developed to characterize the low frequency fluctuations employing the Short Time Fourier Transform in a MATLAB computing environment. It was shown that a trade-off is necessary between frequency and time resolution in the acoustic spectrogram. The procedure requires careful evaluation and selection of the data analysis parameters, including the data sampling frequency, Fourier Transform window size, associated time period and frequency resolution, and time period window overlap. Low frequency fluctuations were applied to the synthesis of broadband noise with the resulting records sounding virtually indistinguishable from the measured data in initial subjective evaluations. Amplitude fluctuations of blade passage frequency (BPF) harmonics were successfully characterized for conditions equivalent to take-off and approach. Data demonstrated that the fifth harmonic of the BPF varied more in frequency than the BPF itself and exhibited larger amplitude fluctuations over the duration of the time record. Frequency fluctuations were found to be not perceptible in the current characterization of tonal components.

  2. En route noise: NASA propfan test aircraft (calculated source noise

    NASA Technical Reports Server (NTRS)

    Rickley, E. J.

    1990-01-01

    The second phase of a joint National Aeronautics and Space Administration (NASA) and Federal Aviation Administration (FAA) program to study the high-altitude, low-frequency acoustic noise propagation characteristics of the Advanced Turboprop (propfan) Aircraft was conducted on April 3-13, 1989 at the White Sands Missile Range (WSMR), New Mexico. The first phase was conducted on October 26-31, 1987 in Huntsville, Alabama. NASA (Lewis) measured the source noise of the test aircraft during both phases while NASA (Langley) measured surface noise only during the second phase. FAA/NASA designed a program to obtain noise level data from the propfan test bed aircraft, both in the near field and at ground level, during simulated en route flights (35,000 and 20,000 feet ASL), and to test low frequency atmospheric absorption algorithms and prediction technology to provide insight into the necessity for regulatory measures. The curves of calculated source noise versus emission angle are based on a second order best-fit curve of the peak envelope of the adjusted ground data. Centerline and sideline derived source noise levels are shown to be in good agreement. A comparison of the Alabama chase plane source data and the calculated source noise at centerline for both the Alabama and New Mexico data shows good agreement for the 35,000 and the 20,000 feet (ASL) overflights. With the availability of the New Mexico in-flight data, further in depth comparisons will be made.

  3. Aircraft noise source and contour estimation

    NASA Technical Reports Server (NTRS)

    Dunn, D. G.; Peart, N. A.

    1973-01-01

    Calculation procedures are presented for predicting the noise-time histories and noise contours (footprints) of five basic types of aircraft; turbojet, turofan, turboprop, V/STOL, and helicopter. The procedures have been computerized to facilitate prediction of the noise characteristics during takeoffs, flyovers, and/or landing operations.

  4. An improved source model for aircraft interior noise studies

    NASA Technical Reports Server (NTRS)

    Mahan, J. R.; Fuller, C. R.

    1985-01-01

    There is concern that advanced turboprop engines currently being developed may produce excessive aircraft cabin noise level. This concern has stimulated renewed interest in developing aircraft interior noise reduction methods that do not significnatly increase take off weight. An existing analytical model for noise transmission into aircraft cabins was utilized to investigate the behavior of an improved propeller source model for use in aircraft interior noise studies. The new source model, a virtually rotating dipole, is shown to adequately match measured fuselage sound pressure distributions, including the correct phase relationships, for published data. The virtually rotating dipole is used to study the sensitivity of synchrophasing effectiveness to the fuselage sound pressure trace velocity distribution. Results of calculations are presented which reveal the importance of correctly modeling the surface pressure phase relations in synchrophasing and other aircraft interior noise studies.

  5. An improved source model for aircraft interior noise studies

    NASA Technical Reports Server (NTRS)

    Mahan, J. R.; Fuller, C. R.

    1985-01-01

    There is concern that advanced turboprop engines currently being developed may produce excessive aircraft cabin noise levels. This concern has stimulated renewed interest in developing aircraft interior noise reduction methods that do not significantly increase take off weight. An existing analytical model for noise transmission into aircraft cabins was utilized to investigate the behavior of an improved propeller source model for use in aircraft interior noise studies. The new source model, a virtually rotating dipole, is shown to adequately match measured fuselage sound pressure distributions, including the correct phase relationships, for published data. The virtually rotating dipole is used to study the sensitivity of synchrophasing effectiveness to the fuselage sound pressure trace velocity distribution. Results of calculations are presented which reveal the importance of correctly modeling the surface pressure phase relations in synchrophasing and other aircraft interior noise studies.

  6. Analysis and Synthesis of Tonal Aircraft Noise Sources

    NASA Technical Reports Server (NTRS)

    Allen, Matthew P.; Rizzi, Stephen A.; Burdisso, Ricardo; Okcu, Selen

    2012-01-01

    Fixed and rotary wing aircraft operations can have a significant impact on communities in proximity to airports. Simulation of predicted aircraft flyover noise, paired with listening tests, is useful to noise reduction efforts since it allows direct annoyance evaluation of aircraft or operations currently in the design phase. This paper describes efforts to improve the realism of synthesized source noise by including short term fluctuations, specifically for inlet-radiated tones resulting from the fan stage of turbomachinery. It details analysis performed on an existing set of recorded turbofan data to isolate inlet-radiated tonal fan noise, then extract and model short term tonal fluctuations using the analytic signal. Methodologies for synthesizing time-variant tonal and broadband turbofan noise sources using measured fluctuations are also described. Finally, subjective listening test results are discussed which indicate that time-variant synthesized source noise is perceived to be very similar to recordings.

  7. Aircraft noise reduction technology. [to show impact on individuals and communities, component noise sources, and operational procedures to reduce impact

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Aircraft and airport noise reduction technology programs conducted by NASA are presented. The subjects discussed are: (1) effects of aircraft noise on individuals and communities, (2) status of aircraft source noise technology, (3) operational procedures to reduce the impact of aircraft noise, and (4) NASA relations with military services in aircraft noise problems. References to more detailed technical literature on the subjects discussed are included.

  8. A study of interior noise levels, noise sources and transmission paths in light aircraft

    NASA Technical Reports Server (NTRS)

    Hayden, R. E.; Murray, B. S.; Theobald, M. A.

    1983-01-01

    The interior noise levels and spectral characteristics of 18 single-and twin-engine propeller-driven light aircraft, and source-path diagnosis of a single-engine aircraft which was considered representative of a large part of the fleet were studied. The purpose of the flight surveys was to measure internal noise levels and identify principal noise sources and paths under a carefully controlled and standardized set of flight procedures. The diagnostic tests consisted of flights and ground tests in which various parts of the aircraft, such as engine mounts, the engine compartment, exhaust pipe, individual panels, and the wing strut were instrumented to determine source levels and transmission path strengths using the transfer function technique. Predominant source and path combinations are identified. Experimental techniques are described. Data, transfer function calculations to derive source-path contributions to the cabin acoustic environment, and implications of the findings for noise control design are analyzed.

  9. Aircraft noise source and computer programs - User's guide

    NASA Technical Reports Server (NTRS)

    Crowley, K. C.; Jaeger, M. A.; Meldrum, D. F.

    1973-01-01

    The application of computer programs for predicting the noise-time histories and noise contours for five types of aircraft is reported. The aircraft considered are: (1) turbojet, (2) turbofan, (3) turboprop, (4) V/STOL, and (5) helicopter. Three principle considerations incorporated in the design of the noise prediction program are core effectiveness, limited input, and variable output reporting.

  10. A simple-source model of military jet aircraft noise

    NASA Astrophysics Data System (ADS)

    Morgan, Jessica; Gee, Kent L.; Neilsen, Tracianne; Wall, Alan T.

    2010-10-01

    The jet plumes produced by military jet aircraft radiate significant amounts of noise. A need to better understand the characteristics of the turbulence-induced aeroacoustic sources has motivated the present study. The purpose of the study is to develop a simple-source model of jet noise that can be compared to the measured data. The study is based off of acoustic data collected near a tied-down F-22 Raptor. The simplest model consisted of adjusting the origin of a monopole above a rigid planar reflector until the locations of the predicted and measured interference nulls matched. The model has developed into an extended Rayleigh distribution of partially correlated monopoles which fits the measured data from the F-22 significantly better. The results and basis for the model match the current prevailing theory that jet noise consists of both correlated and uncorrelated sources. In addition, this simple-source model conforms to the theory that the peak source location moves upstream with increasing frequency and lower engine conditions.

  11. A brief review of the source noise technology applicable to fixed-wing military aircraft

    NASA Astrophysics Data System (ADS)

    Pinker, R. A.

    1992-04-01

    Although the last two decades have seen major reductions in the noise from civil aircraft, noise from military operations, both around airfields and from low-flying aircraft, continues to be a source of irritation and a potential health hazard. Because of the continuing concern about the noise levels produced by combat aircraft, the following paper is intended to provide some of the background to the main conclusions and recommendations reached in the final report of the NATO/Committee on the Challenges of a Modern Society (CCMS) Pilot Study on aircraft noise. Although biased towards fixed wing combat aircraft noise, the paper also considers other fixed wing military aircraft, but specifically excludes sonic booms and rotary wing aircraft as they both have their own particular noise sources and problems.

  12. Duct liner optimization for turbomachinery noise sources. [aircraft noise/engine noise - numerical analysis

    NASA Technical Reports Server (NTRS)

    Lester, H. C.; Posey, J. W.

    1975-01-01

    An acoustical field theory for axisymmetric, multisectioned lined ducts with uniform flow profiles was combined with a numerical minimization algorithm to predict optimal liner configurations having one, two, and three sections. Source models studied include a point source located on the axis of the duct and rotor/outlet-stator viscous wake interaction effects for a typical research compressor operating at an axial flow Mach number of about 0.4. For this latter source, optimal liners for equipartition-of energy, zero-phase, and least-attenuated-mode source variations were also calculated and compared with exact results. It is found that the potential benefits of liner segmentation for the attenuation of turbomachinery noise is greater than would be predicted from point source results. Furthermore, effective liner design requires precise knowledge of the circumferential and radial modal distributions.

  13. Commercial aircraft noise

    NASA Astrophysics Data System (ADS)

    Smith, M. J.

    The history of aircraft noise control development is traced with an eye to forecasting the future. Noise control became imperative with the advent of the first generation of commercial jet aircraft, which were extremely loud. The steady increases in the size of turbofans have nearly matched the progress in noise reduction capabilities in recent years. Only 5 dB of reduction in fleet noise has been achieved since early standards were met. Current engine design is concentrated on increasing fuel efficiency rather than lowering noise emissions. Further difficulties exist because of continued flights with older aircraft. Gains in noise reduction have been made mainly by decreasing exhaust velocities from 600-700 m/sec to 300-400 m/sec. New techniques being explored comprise mixing the core and bypass flows, interaction tone control, reduction of broadband sources, development of acoustic liner technology and alterations in the number of fan blades and stage spacing.

  14. Sources, control, and effects of noise from aircraft propellers and rotors

    NASA Technical Reports Server (NTRS)

    Mixson, J. S.; Greene, G. C.; Dempsey, T. K.

    1981-01-01

    Recent NASA and NASA sponsored research on the prediction and control of propeller and rotor source noise, on the analysis and design of fuselage sidewall noise control treatments, and on the measurement and quantification of the response of passengers to aircraft noise is described. Source noise predictions are compared with measurements for conventional low speed propellers, for new high speed propellers (propfans), and for a helicopter. Results from a light aircraft demonstration program are considered which indicates that about 5 dB reduction of flyover noise can be obtained without significant performance penalty. Sidewall design studies are examined for interior noise control in light general aviation aircraft and in large transports using propfan propulsion. The weight of the added acoustic treatment is estimated and tradeoffs between weight and noise reduction are discussed. A laboratory study of passenger response to combined broadband and tonal propeller-like noise is described. Subject discomfort ratings of combined tone broadband noises are compared with ratings of broadband (boundary layer) noise alone and the relative importance of the propeller tones is examined.

  15. Fourth Aircraft Interior Noise Workshop

    NASA Technical Reports Server (NTRS)

    Stephens, David G. (Compiler)

    1992-01-01

    The fourth in a series of NASA/SAE Interior Noise Workshops was held on May 19 and 20, 1992. The theme of the workshop was new technology and applications for aircraft noise with emphasis on source noise prediction; cabin noise prediction; cabin noise control, including active and passive methods; and cabin interior noise procedures. This report is a compilation of the presentations made at the meeting which addressed the above issues.

  16. Aircraft turbofan noise

    NASA Technical Reports Server (NTRS)

    Groeneweg, J. F.; Rice, E. J.

    1983-01-01

    Turbofan noise generation and suppression in aircraft engines are reviewed. The chain of physical processes which connect unsteady flow interactions with fan blades to far field noise is addressed. Mechanism identification and description, duct propagation, radiation and acoustic suppression are discussed. The experimental technique of fan inflow static tests are discussed. Rotor blade surface pressure and wake velocity measurements aid in the determination of the types and strengths of the generation mechanisms. Approaches to predicting or measuring acoustic mode content, optimizing treatment impedance to maximize attenuation, translating impedance into porous wall structure and interpreting far field directivity patterns are illustrated by comparisons of analytical and experimental results. The interdependence of source and acoustic treatment design to minimize far field noise is emphasized. Area requiring further research are discussed and the relevance of aircraft turbofan results to quieting other turbomachinery installations is addressed.

  17. Aircraft noise prediction

    NASA Astrophysics Data System (ADS)

    Filippone, Antonio

    2014-07-01

    This contribution addresses the state-of-the-art in the field of aircraft noise prediction, simulation and minimisation. The point of view taken in this context is that of comprehensive models that couple the various aircraft systems with the acoustic sources, the propagation and the flight trajectories. After an exhaustive review of the present predictive technologies in the relevant fields (airframe, propulsion, propagation, aircraft operations, trajectory optimisation), the paper addresses items for further research and development. Examples are shown for several airplanes, including the Airbus A319-100 (CFM engines), the Bombardier Dash8-Q400 (PW150 engines, Dowty R408 propellers) and the Boeing B737-800 (CFM engines). Predictions are done with the flight mechanics code FLIGHT. The transfer function between flight mechanics and the noise prediction is discussed in some details, along with the numerical procedures for validation and verification. Some code-to-code comparisons are shown. It is contended that the field of aircraft noise prediction has not yet reached a sufficient level of maturity. In particular, some parametric effects cannot be investigated, issues of accuracy are not currently addressed, and validation standards are still lacking.

  18. Structureborne noise in aircraft

    NASA Technical Reports Server (NTRS)

    Clevenson, S. A.; Metcalf, V. L.

    1987-01-01

    The amount of noise reaching an aircraft's interior by structureborne paths, when high levels of other noises are present, involves the measurement of transfer functions between vibrating levels on the wing and interior noise. The magnitude of the structureborne noise transfer function is established by exciting the aircraft with an electrodynamic shaker; a second transfer function is measured using the same sensor locations with the aircraft engines operating. Attention is given to the case of a twin-turboprop OV-10A aircraft; the resulting transfer function values at the discrete frequencies corresponding to the propeller blade passage frequency and its first four harmonics are tabulated and illustrated.

  19. Active control of aircraft engine inlet noise using compact sound sources and distributed error sensors

    NASA Technical Reports Server (NTRS)

    Burdisso, Ricardo (Inventor); Fuller, Chris R. (Inventor); O'Brien, Walter F. (Inventor); Thomas, Russell H. (Inventor); Dungan, Mary E. (Inventor)

    1994-01-01

    An active noise control system using a compact sound source is effective to reduce aircraft engine duct noise. The fan noise from a turbofan engine is controlled using an adaptive filtered-x LMS algorithm. Single multi channel control systems are used to control the fan blade passage frequency (BPF) tone and the BPF tone and the first harmonic of the BPF tone for a plane wave excitation. A multi channel control system is used to control any spinning mode. The multi channel control system to control both fan tones and a high pressure compressor BPF tone simultaneously. In order to make active control of turbofan inlet noise a viable technology, a compact sound source is employed to generate the control field. This control field sound source consists of an array of identical thin, cylindrically curved panels with an inner radius of curvature corresponding to that of the engine inlet. These panels are flush mounted inside the inlet duct and sealed on all edges to prevent leakage around the panel and to minimize the aerodynamic losses created by the addition of the panels. Each panel is driven by one or more piezoelectric force transducers mounted on the surface of the panel. The response of the panel to excitation is maximized when it is driven at its resonance; therefore, the panel is designed such that its fundamental frequency is near the tone to be canceled, typically 2000-4000 Hz.

  20. Active control of aircraft engine inlet noise using compact sound sources and distributed error sensors

    NASA Technical Reports Server (NTRS)

    Burdisso, Ricardo (Inventor); Fuller, Chris R. (Inventor); O'Brien, Walter F. (Inventor); Thomas, Russell H. (Inventor); Dungan, Mary E. (Inventor)

    1996-01-01

    An active noise control system using a compact sound source is effective to reduce aircraft engine duct noise. The fan noise from a turbofan engine is controlled using an adaptive filtered-x LMS algorithm. Single multi channel control systems are used to control the fan blade passage frequency (BPF) tone and the BPF tone and the first harmonic of the BPF tone for a plane wave excitation. A multi channel control system is used to control any spinning mode. The multi channel control system to control both fan tones and a high pressure compressor BPF tone simultaneously. In order to make active control of turbofan inlet noise a viable technology, a compact sound source is employed to generate the control field. This control field sound source consists of an array of identical thin, cylindrically curved panels with an inner radius of curvature corresponding to that of the engine inlet. These panels are flush mounted inside the inlet duct and sealed on all edges to prevent leakage around the panel and to minimize the aerodynamic losses created by the addition of the panels. Each panel is driven by one or more piezoelectric force transducers mounted on the surface of the panel. The response of the panel to excitation is maximized when it is driven at its resonance; therefore, the panel is designed such that its fundamental frequency is near the tone to be canceled, typically 2000-4000 Hz.

  1. Combat aircraft noise

    NASA Astrophysics Data System (ADS)

    Sgarbozza, M.; Depitre, A.

    1992-04-01

    A discussion of the characteristics and the noise levels of combat aircraft and of a transport aircraft in taking off and landing are presented. Some methods of noise reduction are discussed, including the following: operational anti-noise procedures; and concepts of future engines (silent post-combustion and variable cycle). Some measurement results concerning the noise generated in flight at great speeds and low altitude will also be examined. Finally, the protection of the environment of French air bases against noise will be described and the possibilities of regulation examined.

  2. NASA progress in aircraft noise prediction

    NASA Technical Reports Server (NTRS)

    Raney, J. P.; Padula, S. L.; Zorumski, W. E.

    1981-01-01

    Langley Research Center efforts to develop a methodology for predicting the effective perceived noise level (EPNL) produced by jet-powered CTOL aircraft to an accuracy of + or - 1.5 dB are summarized with emphasis on the aircraft noise prediction program (ANOPP) which contains a complete set of prediction methods for CTOL aircraft including propulsion system noise sources, aerodynamic or airframe noise sources, forward speed effects, a layered atmospheric model with molecular absorption, ground impedance effects including excess ground attenuation, and a received noise contouring capability. The present state of ANOPP is described and its accuracy and applicability to the preliminary aircraft design process is assessed. Areas are indicated where further theoretical and experimental research on noise prediction are needed. Topics covered include the elements of the noise prediction problem which are incorporated in ANOPP, results of comparisons of ANOPP calculations with measured noise levels, and progress toward treating noise as a design constraint in aircraft system studies.

  3. Aircraft noise synthesis system

    NASA Astrophysics Data System (ADS)

    McCurdy, David A.; Grandle, Robert E.

    1987-02-01

    A second-generation Aircraft Noise Synthesis System has been developed to provide test stimuli for studies of community annoyance to aircraft flyover noise. The computer-based system generates realistic, time-varying, audio simulations of aircraft flyover noise at a specified observer location on the ground. The synthesis takes into account the time-varying aircraft position relative to the observer; specified reference spectra consisting of broadband, narrowband, and pure-tone components; directivity patterns; Doppler shift; atmospheric effects; and ground effects. These parameters can be specified and controlled in such a way as to generate stimuli in which certain noise characteristics, such as duration or tonal content, are independently varied, while the remaining characteristics, such as broadband content, are held constant. The system can also generate simulations of the predicted noise characteristics of future aircraft. A description of the synthesis system and a discussion of the algorithms and methods used to generate the simulations are provided. An appendix describing the input data and providing user instructions is also included.

  4. Aircraft noise synthesis system

    NASA Technical Reports Server (NTRS)

    Mccurdy, David A.; Grandle, Robert E.

    1987-01-01

    A second-generation Aircraft Noise Synthesis System has been developed to provide test stimuli for studies of community annoyance to aircraft flyover noise. The computer-based system generates realistic, time-varying, audio simulations of aircraft flyover noise at a specified observer location on the ground. The synthesis takes into account the time-varying aircraft position relative to the observer; specified reference spectra consisting of broadband, narrowband, and pure-tone components; directivity patterns; Doppler shift; atmospheric effects; and ground effects. These parameters can be specified and controlled in such a way as to generate stimuli in which certain noise characteristics, such as duration or tonal content, are independently varied, while the remaining characteristics, such as broadband content, are held constant. The system can also generate simulations of the predicted noise characteristics of future aircraft. A description of the synthesis system and a discussion of the algorithms and methods used to generate the simulations are provided. An appendix describing the input data and providing user instructions is also included.

  5. Aircraft noise prediction program theoretical manual, part 2

    NASA Technical Reports Server (NTRS)

    Zorumski, W. E.

    1982-01-01

    Detailed prediction methods for specific aircraft noise sources are given. These sources are airframe noise, combustion noise, fan noise, single and dual stream jet noise, and turbine noise. Modifications to the NASA methods which comply with the International Civil Aviation Organization standard method for aircraft noise prediction are given.

  6. Aircraft noise prediction program theoretical manual, part 1

    NASA Technical Reports Server (NTRS)

    Zorumski, W. E.

    1982-01-01

    Aircraft noise prediction theoretical methods are given. The prediction of data which affect noise generation and propagation is addressed. These data include the aircraft flight dynamics, the source noise parameters, and the propagation effects.

  7. Methods for designing treatments to reduce interior noise of predominant sources and paths in a single engine light aircraft

    NASA Technical Reports Server (NTRS)

    Hayden, Richard E.; Remington, Paul J.; Theobald, Mark A.; Wilby, John F.

    1985-01-01

    The sources and paths by which noise enters the cabin of a small single engine aircraft were determined through a combination of flight and laboratory tests. The primary sources of noise were found to be airborne noise from the propeller and engine casing, airborne noise from the engine exhaust, structureborne noise from the engine/propeller combination and noise associated with air flow over the fuselage. For the propeller, the primary airborne paths were through the firewall, windshield and roof. For the engine, the most important airborne path was through the firewall. Exhaust noise was found to enter the cabin primarily through the panels in the vicinity of the exhaust outlet although exhaust noise entering the cabin through the firewall is a distinct possibility. A number of noise control techniques were tried, including firewall stiffening to reduce engine and propeller airborne noise, to stage isolators and engine mounting spider stiffening to reduce structure-borne noise, and wheel well covers to reduce air flow noise.

  8. Methods for designing treatments to reduce interior noise of predominant sources and paths in a single engine light aircraft

    NASA Astrophysics Data System (ADS)

    Hayden, Richard E.; Remington, Paul J.; Theobald, Mark A.; Wilby, John F.

    1985-03-01

    The sources and paths by which noise enters the cabin of a small single engine aircraft were determined through a combination of flight and laboratory tests. The primary sources of noise were found to be airborne noise from the propeller and engine casing, airborne noise from the engine exhaust, structureborne noise from the engine/propeller combination and noise associated with air flow over the fuselage. For the propeller, the primary airborne paths were through the firewall, windshield and roof. For the engine, the most important airborne path was through the firewall. Exhaust noise was found to enter the cabin primarily through the panels in the vicinity of the exhaust outlet although exhaust noise entering the cabin through the firewall is a distinct possibility. A number of noise control techniques were tried, including firewall stiffening to reduce engine and propeller airborne noise, to stage isolators and engine mounting spider stiffening to reduce structure-borne noise, and wheel well covers to reduce air flow noise.

  9. Aircraft community noise impact studies

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The objectives of the study are to: (1) conduct a program to determine the community noise impact of advanced technology engines when installed in a supersonic aircraft, (2) determine the potential reduction of community noise by flight operational techniques for the study aircraft, (3) estimate the community noise impact of the study aircraft powered by suppressed turbojet engines and by advanced duct heating turbofan engines, and (4) compare the impact of the two supersonic designs with that of conventional commercial DC-8 aircraft.

  10. Computer program to predict aircraft noise levels

    NASA Technical Reports Server (NTRS)

    Clark, B. J.

    1981-01-01

    Methods developed at the NASA Lewis Research Center for predicting the noise contributions from various aircraft noise sources were programmed to predict aircraft noise levels either in flight or in ground tests. The noise sources include fan inlet and exhaust, jet, flap (for powered lift), core (combustor), turbine, and airframe. Noise propagation corrections are available for atmospheric attenuation, ground reflections, extra ground attenuation, and shielding. Outputs can include spectra, overall sound pressure level, perceived noise level, tone-weighted perceived noise level, and effective perceived noise level at locations specified by the user. Footprint contour coordinates and approximate footprint areas can also be calculated. Inputs and outputs can be in either System International or U.S. customary units. The subroutines for each noise source and propagation correction are described. A complete listing is given.

  11. Field and laboratory studies of moving and temporally variable noise sources (aircraft); perception of location, movement, and direction.

    PubMed

    Gunn, W J; Shigehisa, T; Shepherd, W T

    1979-10-01

    The conditions were examined under which more valid and reliable estimates could be made of the effects of aircraft noise on people. In Exper. 1, 12 Ss in 2 different houses directly under the flight path of a major airport (JFK) indicated 1 of 12 possible flight paths (4 directly overhead and 8 to one side) for each of 3 jet aircraft flyovers: 3% of cases in House A and 56% in House B (which had open windows) were correctly identified. Despite judgment inaccuracy, Ss were more than moderately certain of the correctness of their judgments. In Exper. II. Ss either inside or outside of 2 houses in Wallops Station, Virginia, indicated on diagrams the direction of flyovers. Each of 4 aircraft (Boeing 737, C-54, UE-1 helicopter, Queenaire) made 8 flyovers directly over the houses and 8 to one side. Windows were either open or closed. All flyovers and conditions were counterbalanced. All sound sources under all conditions were usually judged to be overhead and moving, but for Ss indoors with windows closed the to-the-side flyovers were judged to be off to the side in 24% of cases. Outdoor Ss reported correct direction in 75% of cases while indoor Ss were correct in only 25% (windows open) or 18% (windows closed). Judgments "to the side" were significantly better (p = less than .02) with windows open vs closed, while with windows closed judgments were significantly better (p = less than .05) for flyovers overhead vs to the side. In Exper. III, Ss localized in azimuth and in the vertical plane recorded noises (10 1-oct noise bands of CF = 28.12 c/s - 14.4kc/s, spoken voice, and jet aircraft takeoffs and landings), presented through 1, 2, or 4 floor-level loudspeakers at each corner of a simulated living room (4.2 x 5.4m)built inside an IAC soundproof room. Aircraft noises presented by 4 loudspeakers were localized as "directly" overhead 80% of the time and "generally overhead" about 90% of the time; other sounds were so localized about 50% and 75% of the time respectively

  12. Review of aircraft noise propagation

    NASA Technical Reports Server (NTRS)

    Putnam, T. W.

    1975-01-01

    The current state of knowledge about the propagation of aircraft noise was reviewed. The literature on the subject is surveyed and methods for predicting the most important and best understood propagation effects are presented. Available empirical data are examined and the data's general validity is assessed. The methods used to determine the loss of acoustic energy due to uniform spherical spreading, absorption in a homogeneous atmosphere, and absorption due to ground cover are presented. A procedure for determining ground induced absorption as a function of elevation angle between source and receiver is recommended. Other factors that affect propagation, such as refraction and scattering due to turbulence, which were found to be less important for predicting the propagation of aircraft noise, are also evaluated.

  13. Disturbance caused by aircraft noise

    NASA Technical Reports Server (NTRS)

    Josse, R.

    1980-01-01

    Noise pollution caused by the presence of airfields adjacent to residential areas is studied. Noise effects on the sleep of residents near airports and the degree of the residents noise tolerance are evaluated. What aircraft noises are annoying and to what extent the annoyance varies with sound level are discussed.

  14. Directional monitoring terminal for aircraft noise

    NASA Astrophysics Data System (ADS)

    Genescà, M.

    2016-07-01

    This paper presents a concept of an aircraft noise monitoring terminal (NMT) that reduces background noise and the influence of ground reflection, in comparison with a single microphone. Also, it automatically identifies aircraft sound events based on the direction of arrival of the sound rather than on the sound pressure level (or radar data). And moreover, it provides an indicator of the quality of the sound pressure level measurement, i.e. if it is possibly disturbed by extraneous sources. The performance of this NMT is experimentally tested under real conditions in a measurement site close to Zurich airport. The results show that the NMT unambiguously identifies the noise events generated by the target aircraft, correctly detects those aircraft noise events that may be disturbed by the presence of other sources, and offers a substantial reduction in background and ground reflected sound.

  15. Comparison of two propeller source models for aircraft interior noise studies

    NASA Technical Reports Server (NTRS)

    Mahan, J. R.; Fuller, C. R.

    1986-01-01

    The sensitivity of the predicted synchrophasing (SP) effectiveness trends to the propeller source model issued is investigated with reference to the development of advanced turboprop engines for transport aircraft. SP effectiveness is shown to be sensitive to the type of source model used. For the virtually rotating dipole source model, the SP effectiveness is sensitive to the direction of rotation at some frequencies but not at others. The SP effectiveness obtained from the virtually rotating dipole model is not very sensitive to the radial location of the source distribution within reasonable limits. Finally, the predicted SP effectiveness is shown to be more sensitive to the details of the source model used for the case of corotation than for the case of counterrotation.

  16. Aircraft Noise and Quality of Life around Frankfurt Airport

    PubMed Central

    Schreckenberg, Dirk; Meis, Markus; Kahl, Cara; Peschel, Christin; Eikmann, Thomas

    2010-01-01

    In a survey of 2,312 residents living near Frankfurt Airport aircraft noise annoyance and disturbances as well as environmental (EQoL) and health-related quality of life (HQoL) were assessed and compared with data on exposure due to aircraft, road traffic, and railway noise. Results indicate higher noise annoyance than predicted from general exposure-response curves. Beside aircraft sound levels source-related attitudes were associated with reactions to aircraft noise. Furthermore, aircraft noise affected EQoL in general, although to a much smaller extent. HQoL was associated with aircraft noise annoyance, noise sensitivity and partly with aircraft noise exposure, in particular in the subgroup of multimorbid residents. The results suggest a recursive relationship between noise and health, yet this cannot be tested in cross-sectional studies. Longitudinal studies would be recommendable to get more insight in the causal paths underlying the noise-health relationship. PMID:20948931

  17. Aircraft noise and quality of life around Frankfurt Airport.

    PubMed

    Schreckenberg, Dirk; Meis, Markus; Kahl, Cara; Peschel, Christin; Eikmann, Thomas

    2010-09-01

    In a survey of 2,312 residents living near Frankfurt Airport aircraft noise annoyance and disturbances as well as environmental (EQoL) and health-related quality of life (HQoL) were assessed and compared with data on exposure due to aircraft, road traffic, and railway noise. Results indicate higher noise annoyance than predicted from general exposure-response curves. Beside aircraft sound levels source-related attitudes were associated with reactions to aircraft noise. Furthermore, aircraft noise affected EQoL in general, although to a much smaller extent. HQoL was associated with aircraft noise annoyance, noise sensitivity and partly with aircraft noise exposure, in particular in the subgroup of multimorbid residents. The results suggest a recursive relationship between noise and health, yet this cannot be tested in cross-sectional studies. Longitudinal studies would be recommendable to get more insight in the causal paths underlying the noise-health relationship.

  18. Technologies for Aircraft Noise Reduction

    NASA Technical Reports Server (NTRS)

    Huff, Dennis L.

    2006-01-01

    Technologies for aircraft noise reduction have been developed by NASA over the past 15 years through the Advanced Subsonic Technology (AST) Noise Reduction Program and the Quiet Aircraft Technology (QAT) project. This presentation summarizes highlights from these programs and anticipated noise reduction benefits for communities surrounding airports. Historical progress in noise reduction and technologies available for future aircraft/engine development are identified. Technologies address aircraft/engine components including fans, exhaust nozzles, landing gear, and flap systems. New "chevron" nozzles have been developed and implemented on several aircraft in production today that provide significant jet noise reduction. New engines using Ultra-High Bypass (UHB) ratios are projected to provide about 10 EPNdB (Effective Perceived Noise Level in decibels) engine noise reduction relative to the average fleet that was flying in 1997. Audio files are embedded in the presentation that estimate the sound levels for a 35,000 pound thrust engine for takeoff and approach power conditions. The predictions are based on actual model scale data that was obtained by NASA. Finally, conceptual pictures are shown that look toward future aircraft/propulsion systems that might be used to obtain further noise reduction.

  19. Requirements for the protection against aircraft noise.

    PubMed

    Wende, H; Ortscheid, J

    2004-01-01

    In preparation of the revised edition of the Air Traffic Noise Act the Federal Environmental Agency formulated targets for aircraft noise control. They were prepared oriented to the Federal Immission Control Act. The assessment periods were chosen analogously to the regulations on other traffic noise sources (rail traffic, road traffic). The control targets cover the following affected areas * aural, extra-aural health * night's sleep * annoyance * communication * recreation Considerable nuisance can be avoided by limiting the exposure to aircraft noise(outside) to equivalent levels below 55 dB(A) by day and 45 dB(A) at night, and impairment of health can be avoided by limiting the exposure to aircraft noise (outside) to equivalent levels below 60 dB(A) by day and 50 dB(A) at night.

  20. The commercial aircraft noise problem

    NASA Astrophysics Data System (ADS)

    Smith, M. J. T.

    1989-01-01

    The history and future developments of commercial aircraft noise are discussed. The use of the turbofan engine to replace the louder turbojet engine is identified as a step forward in reducing noise. The increasing use of two engine planes for medium and even long hauls is seen as a positive trend. An increase in the number of aircraft movements is predicted. An upturn in noise exposure around the end of the century is predicted. The development goals of Rolls Royce in meeting the noise reduction challenges of the next decades are discussed.

  1. Model of aircraft noise adaptation

    NASA Technical Reports Server (NTRS)

    Dempsey, T. K.; Coates, G. D.; Cawthorn, J. M.

    1977-01-01

    Development of an aircraft noise adaptation model, which would account for much of the variability in the responses of subjects participating in human response to noise experiments, was studied. A description of the model development is presented. The principal concept of the model, was the determination of an aircraft adaptation level which represents an annoyance calibration for each individual. Results showed a direct correlation between noise level of the stimuli and annoyance reactions. Attitude-personality variables were found to account for varying annoyance judgements.

  2. Judgments of aircraft noise in a traffic noise background

    NASA Technical Reports Server (NTRS)

    Powell, C. A.; Rice, C. G.

    1975-01-01

    An investigation was conducted to determine subjective response to aircraft noise in different road traffic backgrounds. In addition, two laboratory techniques for presenting the aircraft noise with the background noise were evaluated. For one technique, the background noise was continuous over an entire test session; for the other, the background noise level was changed with each aircraft noise during a session. Subjective response to aircraft noise was found to decrease with increasing background noise level, for a range of typical indoor noise levels. Subjective response was found to be highly correlated with the Noise Pollution Level (NPL) measurement scale.

  3. Aircraft noise propagation. [sound diffraction by wings

    NASA Technical Reports Server (NTRS)

    Hadden, W. J.; Pierce, A. D.

    1978-01-01

    Sound diffraction experiments conducted at NASA Langley Research Center to study the acoustical implications of the engine over wing configuration (noise-shielding by wing) and to provide a data base for assessing various theoretical approaches to the problem of aircraft noise reduction are described. Topics explored include the theory of sound diffraction around screens and wedges; the scattering of spherical waves by rectangular patches; plane wave diffraction by a wedge with finite impedence; and the effects of ambient flow and distribution sources.

  4. Human response to aircraft noise

    NASA Technical Reports Server (NTRS)

    Powell, Clemans A.; Fields, James M.

    1991-01-01

    The human auditory system and the perception of sound are discussed. The major concentration is on the annnoyance response and methods for relating the physical characteristics of sound to those psychosociological attributes associated with human response. Results selected from the extensive laboratory and field research conducted on human response to aircraft noise over the past several decades are presented along with discussions of the methodology commonly used in conducting that research. Finally, some of the more common criteria, regulations, and recommended practices for the control or limitation of aircraft noise are examined in light of the research findings on human response.

  5. Fan Noise Prediction with Applications to Aircraft System Noise Assessment

    NASA Technical Reports Server (NTRS)

    Nark, Douglas M.; Envia, Edmane; Burley, Casey L.

    2009-01-01

    This paper describes an assessment of current fan noise prediction tools by comparing measured and predicted sideline acoustic levels from a benchmark fan noise wind tunnel test. Specifically, an empirical method and newly developed coupled computational approach are utilized to predict aft fan noise for a benchmark test configuration. Comparisons with sideline noise measurements are performed to assess the relative merits of the two approaches. The study identifies issues entailed in coupling the source and propagation codes, as well as provides insight into the capabilities of the tools in predicting the fan noise source and subsequent propagation and radiation. In contrast to the empirical method, the new coupled computational approach provides the ability to investigate acoustic near-field effects. The potential benefits/costs of these new methods are also compared with the existing capabilities in a current aircraft noise system prediction tool. The knowledge gained in this work provides a basis for improved fan source specification in overall aircraft system noise studies.

  6. Handbook of aircraft noise metrics

    NASA Technical Reports Server (NTRS)

    Bennett, R. L.; Pearsons, K. S.

    1981-01-01

    Information is presented on 22 noise metrics that are associated with the measurement and prediction of the effects of aircraft noise. Some of the instantaneous frequency weighted sound level measures, such as A-weighted sound level, are used to provide multiple assessment of the aircraft noise level. Other multiple event metrics, such as day-night average sound level, were designed to relate sound levels measured over a period of time to subjective responses in an effort to determine compatible land uses and aid in community planning. The various measures are divided into: (1) instantaneous sound level metrics; (2) duration corrected single event metrics; (3) multiple event metrics; and (4) speech communication metrics. The scope of each measure is examined in terms of its: definition, purpose, background, relationship to other measures, calculation method, example, equipment, references, and standards.

  7. Effect of at-the-source noise reduction on performance and weights of a tilt-rotor aircraft

    NASA Technical Reports Server (NTRS)

    Gibs, J.; Stepniewski, W. Z.; Spencer, R.

    1975-01-01

    Reduction of far-field acoustic signature through modification of basic design parameters (tip speed, number of blades, disc loading and rotor blade area) was examined, using a tilt-rotor flight research aircraft as a baseline configuration. Of those design parameters, tip speed appeared as the most important. Next, preliminary design of two aircraft was performed, postulating the following reduction of noise level from that of the baseline machine, at 500 feet from the spot of OGE hover. In one aircraft, the PNL was lowered by 10 PNdB and in the other, OASPL decreased by 10 dB. The resulting weight and performance penalties were examined. Then, PNL and EPNL aspects of terminal operation were compared for the baseline and quieter aircraft.

  8. Minimum noise impact aircraft trajectories

    NASA Technical Reports Server (NTRS)

    Jacobson, I. D.; Melton, R. G.

    1981-01-01

    Numerical optimization is used to compute the optimum flight paths, based upon a parametric form that implicitly includes some of the problem restrictions. The other constraints are formulated as penalties in the cost function. Various aircraft on multiple trajectores (landing and takeoff) can be considered. The modular design employed allows for the substitution of alternate models of the population distribution, aircraft noise, flight paths, and annoyance, or for the addition of other features (e.g., fuel consumption) in the cost function. A reduction in the required amount of searching over local minima was achieved through use of the presence of statistical lateral dispersion in the flight paths.

  9. Acceptance and control of aircraft interior noise and vibration

    NASA Technical Reports Server (NTRS)

    Stephens, D. G.; Leatherwood, J. D.

    1980-01-01

    Ride quality criteria for noise, vibration, and their combination in the helicopter cabin environment are discussed. Results are presented of laboratory and field studies of passenger responses to interior noise and vibration during the performance of a listening task and during reverie, as well as to the interaction of noise with multi-frequency and multi-axis vibration. A study of means for reducing helicopter interior noise based on analytical, experimental and flight studies of the near-field noise source characteristics of the aircraft, the transmission of noise through aircraft structures and the attenuation of noise by various noise control treatments is then presented which has resulted in a reduction of 3 dB in helicopter cabin noise. Finally, a model under development to evaluate passenger acceptance of a helicopter noise and vibration environment is indicated which incorporates the observed noise and vibration effects on comfort and is expected to provide insights for more effective noise and vibration control.

  10. An Assessment of Commuter Aircraft Noise Impact

    NASA Technical Reports Server (NTRS)

    Fidell, Sanford; Pearsons, Karl S.; Silvati, Laura; Sneddon, Matthew

    1996-01-01

    This report examines several approaches to understanding 'the commuter aircraft noise problem.' The commuter aircraft noise problem in the sense addressed in this report is the belief that some aspect(s) of community response to noise produced by commuter aircraft operations may not be fully assessed by conventional environmental noise metrics and methods. The report offers alternate perspectives and approaches for understanding this issue. The report also develops a set of diagnostic screening questions; describes commuter aircraft noise situations at several airports; and makes recommendations for increasing understanding of the practical consequences of greater heterogeneity in the air transport fleet serving larger airports.

  11. Program in acoustics. [aeroacoustics, aircraft noise, and noise suppression

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Relevant research projects conducted by faculty and graduate students in the general area of aeroacoustics to further the understanding of noise generation by aircraft and to aid in the development of practical methods for noise suppression are listed. Special activities summarized relate to the nonlinear acoustic wave theory and its application to several cases including that of the acoustic source located at the throat of a near-sonic duct, a computer program developed to compute the nonlinear wave theory, and a parabolic approximation for propagation of sounding in moving stratified media.

  12. Noise control mechanisms of inside aircraft

    NASA Astrophysics Data System (ADS)

    Zverev, A. Ya.

    2016-07-01

    World trends in the development of methods and approaches to noise reduction in aircraft cabins are reviewed. The paper discusses the mechanisms of passive and active noise and vibration control, application of "smart" and innovative materials, new approaches to creating all fuselage-design elements, and other promising directions of noise control inside aircraft.

  13. Noise Control in Propeller-Driven Aircraft

    NASA Technical Reports Server (NTRS)

    Rennison, D. C.; Wilby, J. F.

    1983-01-01

    Analytical model predicts noise levels inside propeller-driven aircraft during cruise at mach 0.8. Double wall sidewalls minimize interior noise and weight. Model applied to three aircraft with fuselages of different size (wide-body, narrow-body, and small-diameter) to determine noise reductions required to achieve A-weighted sound level not to exceed 80 dB.

  14. En route noise of two turboprop aircraft

    NASA Technical Reports Server (NTRS)

    Dobrzynski, Werner

    1990-01-01

    In order to weigh en route noise emissions originating from future propfan powered aircraft, a data base of emission levels from conventional turboprop aircraft is needed. For this reason flyover noise measurements on two twin-engine turboprop aircraft were conducted at flight heights between 17,000 and 21,000 ft. Acoustic data are presented together with propeller operational parameters and environmental meteorological data. Narrowband spectral analyses demonstrate the characteristic features of the measured propeller noise signatures: Noise spectra are dominated by the propeller rotational noise fundamental frequency and pronounced noise beats occur as a consequence of different rotational speeds of the propellers.

  15. Technical Seminar: "Progress in Aircraft Noise Research"""

    NASA Video Gallery

    Advances in aircraft noise research can be attributed to the development of new technologies and sustained collaboration with industry, universities and government organizations. Emphasis has been ...

  16. Propeller aircraft interior noise model

    NASA Technical Reports Server (NTRS)

    Pope, L. D.; Wilby, E. G.; Wilby, J. F.

    1984-01-01

    An analytical model was developed to predict the interior noise of propeller-driven aircraft. The fuselage model is that of a cylinder with a structurally-integral floor. The cabin sidewall is stiffened by stringers and ring frames, and the floor by longitudinal beams. The cabin interior is covered with a sidewall treatments consisting of layers of porous material and an impervious trim septum. Representation of the propeller pressure field is utilized as input data in the form of the propeller noise signature at a series of locations on a grid over the fuselage structure. Results obtained from the analytical model are compared with test data measured by NASA in a scale model cylindrical fuselage excited by a model propeller.

  17. Interior noise considerations for powered-lift STOL aircraft

    NASA Technical Reports Server (NTRS)

    Barton, C. K.

    1975-01-01

    Powered-lift configurations which are currently under development for future use on STOL aircraft involve impingement of the jet engine exhaust onto wing and flap surfaces. Previous studies have suggested that the impinging jet produces higher noise levels at lower frequencies than does the jet alone. These higher levels, together with the close proximity of the engine and flap noise sources to the fuselage sidewall, suggest that the noise levels in these aircraft may be high enough to interfere with passenger comfort. To investigate this possibility, interior noise levels were estimated for both an upper surface blown (USB) and an externally blown flap (EBF) configuration. This paper describes the procedure used to estimate the interior noise levels and compares these levels with levels on existing jet aircraft and on ground transportation vehicles. These estimates indicate high levels in the STOL aircraft; therefore, areas of possible improvements in technology for control of STOL interior noise are also discussed.

  18. Recent Progress in Engine Noise Reduction for Commercial Aircraft Applications

    NASA Technical Reports Server (NTRS)

    Huff, Dennis L.

    2003-01-01

    Considerable progress has been made over the past ten years developing technologies for reducing aircraft noise. Engine noise continues to be a dominate source, particularly for aircraft departing from airports. Research efforts have concentrated on developing noise prediction methods, experimental validation, and developing noise reduction concepts that have been verified through model scale and static engine tests. Most of the work has concentrated on fan and jet components for commercial turbofan engines. In this seminar, an overview of the engine noise reduction work that was sponsored by NASA s Advanced Subsonic Technology Noise Reduction Program will be given, along with background information on turbofan noise sources and certification procedures. Concepts like "chevron" nozzles for jet noise reduction and swept stators for fan noise reduction will be highlighted. A preliminary assessment on how the new technologies will impact future engines will be given.

  19. NASA's Aeroacoustic Tools and Methods for Analysis of Aircraft Noise

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Lopes, Leonard V.; Burley, Casey L.

    2015-01-01

    Aircraft community noise is a significant concern due to continued growth in air traffic, increasingly stringent environmental goals, and operational limitations imposed by airport authorities. The ability to quantify aircraft noise at the source and ultimately at observers is required to develop low noise aircraft designs and flight procedures. Predicting noise at the source, accounting for scattering and propagation through the atmosphere to the observer, and assessing the perception and impact on a community requires physics-based aeroacoustics tools. Along with the analyses for aero-performance, weights and fuel burn, these tools can provide the acoustic component for aircraft MDAO (Multidisciplinary Design Analysis and Optimization). Over the last decade significant progress has been made in advancing the aeroacoustic tools such that acoustic analyses can now be performed during the design process. One major and enabling advance has been the development of the system noise framework known as Aircraft NOise Prediction Program2 (ANOPP2). ANOPP2 is NASA's aeroacoustic toolset and is designed to facilitate the combination of acoustic approaches of varying fidelity for the analysis of noise from conventional and unconventional aircraft. The toolset includes a framework that integrates noise prediction and propagation methods into a unified system for use within general aircraft analysis software. This includes acoustic analyses, signal processing and interfaces that allow for the assessment of perception of noise on a community. ANOPP2's capability to incorporate medium fidelity shielding predictions and wind tunnel experiments into a design environment is presented. An assessment of noise from a conventional and Hybrid Wing Body (HWB) aircraft using medium fidelity scattering methods combined with noise measurements from a model-scale HWB recently placed in NASA's 14x22 wind tunnel are presented. The results are in the form of community noise metrics and

  20. Annoyance caused by light aircraft noise

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The correlation between objective and noise stresses and subjectively perceived disturbance from general aviation aircraft was studied at 6 Swiss airports. Noise levels calculated for these airports are given. Survey results are analyzed.

  1. A trade-off analysis design tool. Aircraft interior noise-motion/passenger satisfaction model

    NASA Technical Reports Server (NTRS)

    Jacobson, I. D.

    1977-01-01

    A design tool was developed to enhance aircraft passenger satisfaction. The effect of aircraft interior motion and noise on passenger comfort and satisfaction was modelled. Effects of individual aircraft noise sources were accounted for, and the impact of noise on passenger activities and noise levels to safeguard passenger hearing were investigated. The motion noise effect models provide a means for tradeoff analyses between noise and motion variables, and also provide a framework for optimizing noise reduction among noise sources. Data for the models were collected onboard commercial aircraft flights and specially scheduled tests.

  2. Laboratory study of the effects of sidewall treatment, source directivity and temperature on the interior noise of a light aircraft fuselage

    NASA Technical Reports Server (NTRS)

    Heitman, K. E.; Mixson, J. S.

    1986-01-01

    This paper describes a laboratory study of add-on {coustic treatments for a twin-engine, propeller-driven aircraft fuselage. The sound source was a pneumatic-driver, with attached horn to simulate propeller noise distribution, powered by a white noise signal. Treatments included a double-wall, production-line treatment and various fiberglass and lead-vinyl treatments. Insertion losses, space-averaged across six interior microphone positions, were used to evaluate the treatments. In addition, the effects of sound source angle and ambient temperature on interior sound pressure level are presented. The sound source angle is shown to have a significant effect on one-third octave band localized sound pressure level. While changes in ambient temperature are shown to have little effect on one-third octave band localized sound pressure level, the change in narrowband localized sound pressure level may be dramatic.

  3. Noise Reduction of Aircraft Flap

    NASA Technical Reports Server (NTRS)

    Hutcheson, Florence V. (Inventor); Brooks, Thomas F. (Inventor)

    2009-01-01

    A reduction in noise radiating from a side of a deployed aircraft flap is achieved by locating a slot adjacent the side of the flap, and then forcing air out through the slot with a suitable mechanism. One, two or even three or more slots are possible, where the slot is located at one;or more locations selected from a group of locations comprising a top surface of the flap, a bottom surface of the flap, an intersection of the top and side surface of the flap, an intersection of the bottom and side surfaces of the flap, and a side surface of the flap. In at least one embodiment the slot is substantially rectangular. A device for adjusting a rate of the air forced out through the slot can also be provided.

  4. Aircraft noise, hearing ability, and annoyance

    SciTech Connect

    Wu, Trong-Neng; Jim Shoung Lai; Chen-Yang Shen

    1995-11-01

    The relationship between aircraft noise, loss of hearing, and annoyance was explored in a study in two schools located near an international airport in Taiwan. Sixth-grade students (N = 242) were recruited from two schools and were classified into high-and low-noise-exposure groups, based on environmental noise measurements. Person-equivalent 24-h noise exposure was measured to determine noise exposure at the individual level, and it was compared with hearing threshold level and with aircraft noise measured at the environmental level. Individual hearing threshold levels did not differ between environmental high- and low-noise-exposure groups, as evidenced by the lack of difference between the two groups for noise exposure measured at the individual level. However, the proportion of students who were annoyed by aircraft noise was higher in the environmental high-noise-exposure group, although personal 24-h noise exposure was not a factor for annoyance. The results indicated that environmental noise measurement was not an appropriate criterion for assessment of auditory damage (or noise-induced hearing loss) in Taiwan. As well, aircraft-noise exposure in Taiwan did not appear to affect the hearing threshold but nonetheless annoyed school children near the airport. 21 refs., 3 tabs.

  5. Annoyance caused by aircraft en route noise

    NASA Technical Reports Server (NTRS)

    Mccurdy, David A.

    1992-01-01

    A laboratory experiment was conducted to quantify the annoyance response of people on the ground to enroute noise generated by aircraft at cruise conditions. The en route noises were ground level recordings of eight advanced turboprop aircraft flyovers and six conventional turbofan flyovers. The eight advanced turboprop enroute noises represented the NASA Propfan Test Assessment aircraft operating at different combinations of altitude, aircraft Mach number, and propeller tip speed. The conventional turbofan en route noises represented six different commercial airliners. The overall durations of the en route noises varied from approximately 40 to 160 sec. In the experiment, 32 subjects judged the annoyance of the en route noises as well as recordings of the takeoff and landing noises of each of 5 conventional turboprop and 5 conventional turbofan aircraft. Each of the noises was presented at three sound pressure levels to the subjects in an anechoic listening room. Analysis of the judgments found small differences in annoyance between three combinations of aircraft type and operation. Current tone and corrections did not significantly improve en route annoyance prediction. The optimum duration-correction magnitude for en route noise was approximately 1 dB per doubling of effective duration.

  6. Aircraft interior noise reduction by alternate resonance tuning

    NASA Technical Reports Server (NTRS)

    Bliss, Donald B.; Gottwald, James A.; Srinivasan, Ramakrishna; Gustaveson, Mark B.

    1990-01-01

    Existing interior noise reduction techniques for aircraft fuselages perform reasonably well at higher frequencies, but are inadequate at lower frequencies, particularly with respect to the low blade passage harmonics with high forcing levels found in propeller aircraft. A method is being studied which considers aircraft fuselage lined with panels alternately tuned to frequencies above and below the frequency that must be attenuated. Adjacent panels would oscillate at equal amplitude, to give equal source strength, but with opposite phase. Provided these adjacent panels are acoustically compact, the resulting cancellation causes the interior acoustic modes to become cutoff, and therefore be non-propagating and evanescent. This interior noise reduction method, called Alternate Resonance Tuning (ART), is currently being investigated both theoretically and experimentally. This new concept has potential application to reducing interior noise due to the propellers in advanced turboprop aircraft as well as for existing aircraft configurations.

  7. Recent advances in active control of aircraft cabin noise

    NASA Astrophysics Data System (ADS)

    Mathur, Gopal; Fuller, Christopher

    2002-11-01

    Active noise control techniques can provide significant reductions in aircraft interior noise levels without the structural modifications or weight penalties usually associated with passive techniques, particularly for low frequency noise. Our main objective in this presentation is to give a review of active control methods and their applications to aircraft cabin noise reduction with an emphasis on recent advances and challenges facing the noise control engineer in the practical application of these techniques. The active noise control method using secondary acoustic sources, e.g., loudspeakers, as control sources for tonal noise reduction is first discussed with results from an active noise control flight test demonstration. An innovative approach of applying control forces directly to the fuselage structure using piezoelectric actuators, known as active structural acoustic control (ASAC), to control cabin noise is then presented. Experimental results from laboratory ASAC tests conducted on a full-scale fuselage and from flight tests on a helicopter will be discussed. Finally, a hybrid active/passive noise control approach for achieving significant broadband noise reduction will be discussed. Experimental results of control of broadband noise transmission through an aircraft structure will be presented.

  8. An Overview of Virtual Acoustic Simulation of Aircraft Flyover Noise

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.

    2013-01-01

    Methods for testing human subject response to aircraft flyover noise have greatly advanced in recent years as a result of advances in simulation technology. Capabilities have been developed which now allow subjects to be immersed both visually and aurally in a three-dimensional, virtual environment. While suitable for displaying recorded aircraft noise, the true potential is found when synthesizing aircraft flyover noise because it allows the flexibility and freedom to study sounds from aircraft not yet flown. A virtual acoustic simulation method is described which is built upon prediction-based source noise synthesis, engineering-based propagation modeling, and empirically-based receiver modeling. This source-path-receiver paradigm allows complete control over all aspects of flyover auralization. With this capability, it is now possible to assess human response to flyover noise by systematically evaluating source noise reductions within the context of a system level simulation. Examples of auralized flyover noise and movie clips representative of an immersive aircraft flyover environment are made in the presentation.

  9. The prediction of en route noise levels for a DC-9 aircraft

    NASA Technical Reports Server (NTRS)

    Weir, Donald S.

    1988-01-01

    En route noise for advanced propfan powered aircraft has become an issue of concern for the Federal Aviation Administration. The NASA Aircraft Noise Prediction Program (ANOPP) is used to demonstrate the source noise and propagation effects for an aircraft in level flight up to 35,000 feet altitude. One-third octave band spectra of the source noise, atmospheric absorption loss, and received noise are presented. The predicted maximum A-weighted sound pressure level is compared to measured data from the Aeronautical Research Institute of Sweden. ANOPP is shown to be an effective tool in evaluating the en route noise characteristics of a DC-9 aircraft.

  10. Residents' annoyance responses to aircraft noise events

    NASA Technical Reports Server (NTRS)

    Dempsey, T. K.; Stephens, D. G.; Fields, J. M.; Shepherd, K. P.

    1983-01-01

    In a study conducted in the vicinity of Salt Lake City International Airport, community residents reported their annoyance with individual aircraft flyovers during rating sessions conducted in their homes. Annoyance ratings were obtained at different times of the day. Aircraft noise levels were measured, and other characteristics of the aircraft were noted by trained observers. Metrics commonly used for assessing aircraft noise were compared, but none performed significantly better than A-weighted sound pressure level. A significant difference was found between the ratings of commercial jet aircraft and general aviation propeller aircraft, with the latter being judged less annoying. After the effects of noise level were accounted for, no significant differences were found between the ratings of landings and takeoffs. Aircraft noise annoyance reactions are stronger in lowered ambient noise conditions. This is consistent with the theory that reduced nighttime and evening ambient levels could create different reactions at different times of day. After controlling for ambient noise in a multiple regression analysis, no significant differences were found between the ratings of single events obtained during the three time periods: morning, afternoon, and evenings.

  11. Combat aircraft noise: The operator's perspective

    NASA Astrophysics Data System (ADS)

    Bogg, R.

    1992-04-01

    Combat aircraft are not subject to the same noise reduction regulations as civil aircraft. Additionally, combat aircraft are operated closer to their performance limits and at high power settings for extended periods. There is general pressure to reduce noise of all kinds, but particularly noise from low flying aircraft. Although there is little that can be done to quiet in-service engines, operational palliatives, such as noise abatement procedures and restrictions on low flying, have been introduced. Moreover, there has been a concerted education and public relations campaign, and numerous airspace management changes have been introduced to reduce the impact of low flying on the population. These subjects were considered during a Pilot Study into aircraft noise under the auspices of the NATO Committee on the Challenges of Modern Society; the findings of the Study are discussed, giving both the international viewpoint and the UK perspective in particular. Some options for the reduction of low flying are also considered, but so long as military aircraft need to fly low to evade enemy air defences, low flying will remain a principal tactic of NATO air forces, and peacetime training will remain an essential military requirement. Thus, noise from low flying combat aircraft will remain a sensitive issue, and ways of reducing it will continue to be of importance for many years to come.

  12. Interior noise levels of two propeller-driven light aircraft

    NASA Technical Reports Server (NTRS)

    Catherines, J. J.; Mayes, W. H.

    1975-01-01

    The relationships between aircraft operating conditions and interior noise and the degree to which ground testing can be used in lieu of flight testing for performing interior noise research were studied. The results show that the noise inside light aircraft is strongly influenced by the rotational speed of the engine and propeller. Both the overall noise and low frequency spectra levels were observed to decrease with increasing high speed rpm operations during flight. This phenomenon and its significance is not presently understood. Comparison of spectra obtained in flight with spectra obtained on the ground suggests that identification of frequency components and relative amplitude of propeller and engine noise sources may be evaluated on stationary aircraft.

  13. An aircraft noise study in Norway

    NASA Technical Reports Server (NTRS)

    Gjestland, Truls T.; Liasjo, Kare H.; Bohn, Hans Einar

    1990-01-01

    An extensive study of aircraft noise is currently being conducted in Oslo, Norway. The traffic at Oslo Airport Fornebu that includes both national and international flights, totals approximately 350 movements per day: 250 of these are regular scheduled flights with intermediate and large size aircraft, the bulk being DC9 and Boeing 737. The total traffic during the summer of 1989 was expected to resemble the maximum level to which the regular traffic will increase before the new airport can be put into operation. The situation therefore represented a possibility to study the noise impact on the communities around Fornebu. A comprehensive social survey was designed, including questions on both aircraft and road traffic noise. A random sample of 1650 respondents in 15 study areas were contacted for an interview. These areas represent different noise levels and different locations relative to the flight paths. The interviews were conducted in a 2 week period just prior to the transfer of charter traffic from Gardemoen to Fornebu. In the same period the aircraft noise was monitored in all 15 areas. In addition the airport is equipped with a permanent flight track and noise monitoring system. The noise situation both in the study period and on an average basis can therefore be accurately described. In August a group of 1800 new respondents were subjected to identical interviews in the same 15 areas, and the noise measurement program was repeated. Results of the study are discussed.

  14. Potential for Landing Gear Noise Reduction on Advanced Aircraft Configurations

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H.; Nickol, Craig L.; Burley, Casey L.; Guo, Yueping

    2016-01-01

    The potential of significantly reducing aircraft landing gear noise is explored for aircraft configurations with engines installed above the wings or the fuselage. An innovative concept is studied that does not alter the main gear assembly itself but does shorten the main strut and integrates the gear in pods whose interior surfaces are treated with acoustic liner. The concept is meant to achieve maximum noise reduction so that main landing gears can be eliminated as a major source of airframe noise. By applying this concept to an aircraft configuration with 2025 entry-into-service technology levels, it is shown that compared to noise levels of current technology, the main gear noise can be reduced by 10 EPNL dB, bringing the main gear noise close to a floor established by other components such as the nose gear. The assessment of the noise reduction potential accounts for design features for the advanced aircraft configuration and includes the effects of local flow velocity in and around the pods, gear noise reflection from the airframe, and reflection and attenuation from acoustic liner treatment on pod surfaces and doors. A technical roadmap for maturing this concept is discussed, and the possible drag increase at cruise due to the addition of the pods is identified as a challenge, which needs to be quantified and minimized possibly with the combination of detailed design and application of drag reduction technologies.

  15. Community noise sources and noise control issues

    NASA Technical Reports Server (NTRS)

    Nihart, Gene L.

    1992-01-01

    The topics covered include the following: community noise sources and noise control issues; noise components for turbine bypass turbojet engine (TBE) turbojet; engine cycle selection and noise; nozzle development schedule; NACA nozzle design; NACA nozzle test results; nearly fully mixed (NFM) nozzle design; noise versus aspiration rate; peak noise test results; nozzle test in the Low Speed Aeroacoustic Facility (LSAF); and Schlieren pictures of NACA nozzle.

  16. Aircraft noise descriptor and its application

    NASA Astrophysics Data System (ADS)

    Igarashi, Juichi

    The methods and indices used in Japan to evaluate aircraft noise and the government-enforced countermeasures are discussed. The ECPNL descriptor was modified so as to make the new descriptor, WECPNL', approximately equivalent to Lden, and the noise contours were calculated for each airport in Japan. The government enforced the policy of land purchase within the WECPNL' of 85, and the houses within the value of 75 were declared as needing insulation. The noise descriptor Leq or Ldn has been used to describe human responses to various kinds of noises. However, a single value descriptor was found to have a limit of applicability, because the human response is not a linear function of a sound level. Another defect of the descriptor is a failure to represent the human response adequately for a small number of flights. It is noted that the house vibration caused by low-frequency components of aircraft noise cannot yet be evaluated.

  17. A path model of aircraft noise annoyance

    NASA Astrophysics Data System (ADS)

    Taylor, S. M.

    1984-09-01

    This paper describes the development and testing of a path model of aircraft noise annoyance by using noise and social survey data collected in the vicinity of Toronto International Airport. Path analysis is used to estimate the direct and indirect effects of seventeen independent variables on individual annoyance. The results show that the strongest direct effects are for speech interference, attitudes toward aircraft operations, sleep interruption and personal sensitivity to noise. The strongest indirect effects are for aircraft Leq(24) and sensitivity. Overall the model explains 41 percent of the variation in the annoyance reported by the 673 survey respondents. The findings both support and extend existing statements in the literature on the antecedents of annoyance.

  18. Review of Aircraft Engine Fan Noise Reduction

    NASA Technical Reports Server (NTRS)

    VanZante, Dale

    2008-01-01

    Aircraft turbofan engines incorporate multiple technologies to enhance performance and durability while reducing noise emissions. Both careful aerodynamic design of the fan and proper installation of the fan into the system are requirements for achieving the performance and acoustic objectives. The design and installation characteristics of high performance aircraft engine fans will be discussed along with some lessons learned that may be applicable to spaceflight fan applications.

  19. Recent Progress in Aircraft Noise Research

    NASA Technical Reports Server (NTRS)

    Envia, Edmane; Thomas, Russell

    2007-01-01

    An overview of the acoustics research at NASA under the Subsonic Fixed Wing project is given. The presentation describes the rationale behind the noise reduction goals of the project in the context of the next generation air transportation system, and the emphasis placed on achieving these goals through a combination of the in-house and collaborative efforts with industry, universities and other government agencies. The presentation also describes the in-house research plan which is focused on the development of advanced noise and flow diagnostic techniques, next generation noise prediction tools, and novel noise reduction techniques that are applicable across a wide range of aircraft.

  20. Comparison of predicted engine core noise with current and proposed aircraft noise certification requirements

    NASA Technical Reports Server (NTRS)

    Vonglahn, U. H.; Groesbeck, D. E.

    1981-01-01

    Predicted engine core noise levels are compared with measured total aircraft noise levels and with current and proposed federal noise certification requirements. Comparisons are made at the FAR-36 measuring stations and include consideration of both full- and cutback-power operation at takeoff. In general, core noise provides a barrier to achieving proposed EPA stage 5 noise levels for all types of aircraft. More specifically, core noise levels will limit further reductions in aircraft noise levels for current widebody commercial aircraft.

  1. Assessment of NASA's Aircraft Noise Prediction Capability

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D. (Editor)

    2012-01-01

    A goal of NASA s Fundamental Aeronautics Program is the improvement of aircraft noise prediction. This document provides an assessment, conducted from 2006 to 2009, on the current state of the art for aircraft noise prediction by carefully analyzing the results from prediction tools and from the experimental databases to determine errors and uncertainties and compare results to validate the predictions. The error analysis is included for both the predictions and the experimental data and helps identify where improvements are required. This study is restricted to prediction methods and databases developed or sponsored by NASA, although in many cases they represent the current state of the art for industry. The present document begins with an introduction giving a general background for and a discussion on the process of this assessment followed by eight chapters covering topics at both the system and the component levels. The topic areas, each with multiple contributors, are aircraft system noise, engine system noise, airframe noise, fan noise, liner physics, duct acoustics, jet noise, and propulsion airframe aeroacoustics.

  2. Aircraft noise prediction program user's manual

    NASA Technical Reports Server (NTRS)

    Gillian, R. E.

    1982-01-01

    The Aircraft Noise Prediction Program (ANOPP) predicts aircraft noise with the best methods available. This manual is designed to give the user an understanding of the capabilities of ANOPP and to show how to formulate problems and obtain solutions by using these capabilities. Sections within the manual document basic ANOPP concepts, ANOPP usage, ANOPP functional modules, ANOPP control statement procedure library, and ANOPP permanent data base. appendixes to the manual include information on preparing job decks for the operating systems in use, error diagnostics and recovery techniques, and a glossary of ANOPP terms.

  3. Aircraft cabin noise prediction and optimization

    NASA Technical Reports Server (NTRS)

    Vaicaitis, R.

    1985-01-01

    Theoretical and experimental studies were conducted to determine the noise transmission into acoustic enclosures ranging from simple rectangular box models to full scale light aircraft in flight. The structural models include simple, stiffened, curved stiffened, and orthotropic panels and double wall windows. The theoretical solutions were obtained by model analysis. Transfer matrix and finite element procedures were utilized. Good agreement between theory and experiment has been achieved. An efficient acoustic add-on treatment was developed for interior noise control in a twin engine light aircraft.

  4. Aircraft propeller induced structure-borne noise

    NASA Technical Reports Server (NTRS)

    Unruh, James F.

    1989-01-01

    A laboratory-based test apparatus employing components typical of aircraft construction was developed that would allow the study of structure-borne noise transmission due to propeller induced wake/vortex excitation of in-wake structural appendages. The test apparatus was employed to evaluate several aircraft installation effects (power plant placement, engine/nacelle mass loading, and wing/fuselage attachment methods) and several structural response modifications for structure-borne noise control (the use of wing blocking mass/fuel, wing damping treaments, and tuned mechanical dampers). Most important was the development of in-flight structure-borne noise transmission detection techniques using a combination of ground-based frequency response function testing and in-flight structural response measurement. Propeller wake/vortex excitation simulation techniques for improved ground-based testing were also developed to support the in-flight structure-borne noise transmission detection development.

  5. Noise Scaling and Community Noise Metrics for the Hybrid Wing Body Aircraft

    NASA Technical Reports Server (NTRS)

    Burley, Casey L.; Brooks, Thomas F.; Hutcheson, Florence V.; Doty, Michael J.; Lopes, Leonard V.; Nickol, Craig L.; Vicroy, Dan D.; Pope, D. Stuart

    2014-01-01

    An aircraft system noise assessment was performed for the hybrid wing body aircraft concept, known as the N2A-EXTE. This assessment is a result of an effort by NASA to explore a realistic HWB design that has the potential to substantially reduce noise and fuel burn. Under contract to NASA, Boeing designed the aircraft using practical aircraft design princip0les with incorporation of noise technologies projected to be available in the 2020 timeframe. NASA tested 5.8% scale-mode of the design in the NASA Langley 14- by 22-Foot Subsonic Tunnel to provide source noise directivity and installation effects for aircraft engine and airframe configurations. Analysis permitted direct scaling of the model-scale jet, airframe, and engine shielding effect measurements to full-scale. Use of these in combination with ANOPP predictions enabled computations of the cumulative (CUM) noise margins relative to FAA Stage 4 limits. The CUM margins were computed for a baseline N2A-EXTE configuration and for configurations with added noise reduction strategies. The strategies include reduced approach speed, over-the-rotor line and soft-vane fan technologies, vertical tail placement and orientation, and modified landing gear designs with fairings. Combining the inherent HWB engine shielding by the airframe with added noise technologies, the cumulative noise was assessed at 38.7 dB below FAA Stage 4 certification level, just 3.3 dB short of the NASA N+2 goal of 42 dB. This new result shows that the NASA N+2 goal is approachable and that significant reduction in overall aircraft noise is possible through configurations with noise reduction technologies and operational changes.

  6. Effects of aircraft noise on human activities

    NASA Technical Reports Server (NTRS)

    Arnoult, M. D.; Gilfillan, L. G.

    1983-01-01

    The effects of aircrft noise on human activities was investigated by developing a battery of tasks (1) representative of a range of human activities and (2) sensitive to the disruptive effects of noise. The noise used were recordings of jet aircraft and helicopter sounds at three lvels of loudness--60, 70, and 80 dB(A). Experiment 1 investigated 12 different cognitive tasks, along with two intelligibility tasks included to validate that the noises were being effective. Interference with intelligibility was essentially the same as found in the research literature, but only inconsistent effects were found on either accuracy or latency of performance on the cognitive tasks. When the tasks were grouped into four categories (Intelligibility, Matching, Verbal, and Arithmetic), reliable differences in rated annoyingness of the noises were related to the task category and to the type of noise (jet or helicopter).

  7. Empirical Prediction of Aircraft Landing Gear Noise

    NASA Technical Reports Server (NTRS)

    Golub, Robert A. (Technical Monitor); Guo, Yue-Ping

    2005-01-01

    This report documents a semi-empirical/semi-analytical method for landing gear noise prediction. The method is based on scaling laws of the theory of aerodynamic noise generation and correlation of these scaling laws with current available test data. The former gives the method a sound theoretical foundation and the latter quantitatively determines the relations between the parameters of the landing gear assembly and the far field noise, enabling practical predictions of aircraft landing gear noise, both for parametric trends and for absolute noise levels. The prediction model is validated by wind tunnel test data for an isolated Boeing 737 landing gear and by flight data for the Boeing 777 airplane. In both cases, the predictions agree well with data, both in parametric trends and in absolute noise levels.

  8. Structureborne noise control in advanced turboprop aircraft

    NASA Astrophysics Data System (ADS)

    Loeffler, Irvin J.

    1987-01-01

    Structureborne noise is discussed as a contributor to propeller aircraft interior noise levels that are nonresponsive to the application of a generous amount of cabin sidewall acoustic treatment. High structureborne noise levels may jeopardize passenger acceptance of the fuel-efficient high-speed propeller transport aircraft designed for cruise at Mach 0.65 to 0.85. These single-rotation tractor and counter-rotation tractor and pusher propulsion systems will consume 15 to 30 percent less fuel than advanced turbofan systems. Structureborne noise detection methodologies and the importance of development of a structureborne noise sensor are discussed. A structureborne noise generation mechanism is described in which the periodic components or propeller swirl produce periodic torques and forces on downstream wings and airfoils that are propagated to the cabin interior as noise. Three concepts for controlling structureborne noise are presented: (1) a stator row swirl remover, (2) selection of a proper combination of blade numbers in the rotor/stator system of a single-rotation propeller, and the rotor/rotor system of a counter-rotation propeller, and (3) a tuned mechanical absorber.

  9. Effects of a traffic noise background on judgements of aircraft noise

    NASA Technical Reports Server (NTRS)

    Powell, C. A.; Rice, C. G.

    1974-01-01

    A study was conducted in which subjects judged aircraft noises in the presence of road traffic background noise. Two different techniques for presenting the background noises were evaluated. For one technique, the background noise was continuous over the whole of a test session. For the other, the background noise was changed with each aircraft noise. A range of aircraft noise levels and traffic noise levels were presented to simulate typical indoor levels.

  10. Advanced Study for Active Noise Control in Aircraft (ASANCA)

    NASA Technical Reports Server (NTRS)

    Borchers, Ingo U.; Emborg, Urban; Sollo, Antonio; Waterman, Elly H.; Paillard, Jacques; Larsen, Peter N.; Venet, Gerard; Goeransson, Peter; Martin, Vincent

    1992-01-01

    Aircraft interior noise and vibration measurements are included in this paper from ground and flight tests. In addition, related initial noise calculations with and without active noise control are conducted. The results obtained to date indicate that active noise control may be an effective means for reducing the critical low frequency aircraft noise.

  11. Synthesis of Virtual Environments for Aircraft Community Noise Impact Studies

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Sullivan, Brenda M.

    2005-01-01

    A new capability has been developed for the creation of virtual environments for the study of aircraft community noise. It is applicable for use with both recorded and synthesized aircraft noise. When using synthesized noise, a three-stage process is adopted involving non-real-time prediction and synthesis stages followed by a real-time rendering stage. Included in the prediction-based source noise synthesis are temporal variations associated with changes in operational state, and low frequency fluctuations that are present under all operating conditions. Included in the rendering stage are the effects of spreading loss, absolute delay, atmospheric absorption, ground reflections, and binaural filtering. Results of prediction, synthesis and rendering stages are presented.

  12. Preliminary Work for Modeling the Propellers of an Aircraft as a Noise Source in an Acoustic Boundary Element Analysis

    NASA Technical Reports Server (NTRS)

    Vlahopoulos, Nickolas; Lyle, Karen H.; Burley, Casey L.

    1998-01-01

    An algorithm for generating appropriate velocity boundary conditions for an acoustic boundary element analysis from the kinematics of an operating propeller is presented. It constitutes the initial phase of Integrating sophisticated rotorcraft models into a conventional boundary element analysis. Currently, the pressure field is computed by a linear approximation. An initial validation of the developed process was performed by comparing numerical results to test data for the external acoustic pressure on the surface of a tilt-rotor aircraft for one flight condition.

  13. Active Control of Aerodynamic Noise Sources

    NASA Technical Reports Server (NTRS)

    Reynolds, Gregory A.

    2001-01-01

    Aerodynamic noise sources become important when propulsion noise is relatively low, as during aircraft landing. Under these conditions, aerodynamic noise from high-lift systems can be significant. The research program and accomplishments described here are directed toward reduction of this aerodynamic noise. Progress toward this objective include correction of flow quality in the Low Turbulence Water Channel flow facility, development of a test model and traversing mechanism, and improvement of the data acquisition and flow visualization capabilities in the Aero. & Fluid Dynamics Laboratory. These developments are described in this report.

  14. Aircraft and airport noise control prospective outlook

    SciTech Connect

    Shapiro, N.

    1982-01-01

    In a perspective look at aircraft and airport noise control over the past ten years or more - or more is added here because the Federal Aviation Regulation Part 36 of 1969 is a more significant milestone for the air transportation system than is the Noise Control Act of 1972 - we see an appreciable reduction in the noise emitted by newly designed and newly produced airplanes, particularly those powered by the new high bypass engines, but only, at best, a moderate alleviation of airport noise. The change in airport noise exposure was the consequence of the introduction of some new, quieter airplanes into the airlines fleets and some operational modifications or restrictions at the airports.

  15. Auralization of Hybrid Wing Body Aircraft Flyover Noise from System Noise Predictions

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Aumann, Aric R.; Lopes, Leonvard V.; Burley, Casey L.

    2013-01-01

    System noise assessments of a state-of-the-art reference aircraft (similar to a Boeing 777-200ER with GE90-like turbofan engines) and several hybrid wing body (HWB) aircraft configurations were recently performed using NASA engine and aircraft system analysis tools. The HWB aircraft were sized to an equivalent mission as the reference aircraft and assessments were performed using measurements of airframe shielding from a series of propulsion airframe aeroacoustic experiments. The focus of this work is to auralize flyover noise from the reference aircraft and the best HWB configuration using source noise predictions and shielding data based largely on the earlier assessments. For each aircraft, three flyover conditions are auralized. These correspond to approach, sideline, and cutback operating states, but flown in straight and level flight trajectories. The auralizations are performed using synthesis and simulation tools developed at NASA. Audio and visual presentations are provided to allow the reader to experience the flyover from the perspective of a listener in the simulated environment.

  16. Effects on sleep of noise from two proposed STOL aircraft

    NASA Technical Reports Server (NTRS)

    Lukas, J. S.; Peeler, D. J.; Davis, J. E.

    1975-01-01

    Responses, both overt behavior and those measured by electroencephalograph, to noise by eight male subjects were studied for sixteen consecutive nights. Test stimuli were: (1) The simulated sideline noise of a short takeoff and landing aircraft with blown flaps; (2) the simulated sideline noise of a STOL aircraft of turbofan design; (3) the simulated takeoff noise of the blown flap STOL aircraft; and (4) a four second burst of simulated pink noise. Responses to each noise were tested at three noise intensities selected to represent levels expected indoors from operational aircraft. The results indicate that the blown flap STOL aircraft noise resulted in 8 to 10 percent fewer sleep disturbance responses than did the turbofan STOL aircraft when noises of comparable intensities from similar maneuvers were used.

  17. Further studies of methods for reducing community noise around airports. [aircraft noise - aircraft engines

    NASA Technical Reports Server (NTRS)

    Petersen, R. H.; Barry, D. J.; Kline, D. M.

    1975-01-01

    A simplified method of analysis was used in which all flights at a 'simulated' airport were assumed to operate from one runway in a single direction. For this simulated airport, contours of noise exposure forecast were obtained and evaluated. A flight schedule of the simulated airport which is representative of the 23 major U. S. airports was used. The effect of banning night-time operations by four-engine, narrow-body aircraft in combination with other noise reduction options was studied. The reductions in noise which would occur of two- and three-engine, narrow-body aircraft equipped with a refanned engine was examined. A detailed comparison of the effects of engine cutback on takeoff versus the effects of retrofitting quiet nacelles for narrow-body aircraft was also examined. A method of presenting the effects of various noise reduction options was treated.

  18. Recommendations for field measurements of aircraft noise

    NASA Technical Reports Server (NTRS)

    Marsh, A. H.

    1982-01-01

    Specific recommendations for environmental test criteria, data acquisition procedures, and instrument performance requirements for measurement of noise levels produced by aircraft in flight are provided. Recommendations are also given for measurement of associated airplane and engine parameters and atmospheric conditions. Recommendations are based on capabilities which were available commercially in 1981; they are applicable to field tests of aircraft flying subsonically past microphones located near the surface of the ground either directly under or to the side of a flight path. Aircraft types covered by the recommendations include fixed-wing airplanes powered by turbojet or turbofan engines or by propellers. The recommended field-measurement procedures are consistent with assumed requirements for data processing and analysis.

  19. Modeling aircraft noise induced sleep disturbance

    NASA Astrophysics Data System (ADS)

    McGuire, Sarah M.

    One of the primary impacts of aircraft noise on a community is its disruption of sleep. Aircraft noise increases the time to fall asleep, the number of awakenings, and decreases the amount of rapid eye movement and slow wave sleep. Understanding these changes in sleep may be important as they could increase the risk for developing next-day effects such as sleepiness and reduced performance and long-term health effects such as cardiovascular disease. There are models that have been developed to predict the effect of aircraft noise on sleep. However, most of these models only predict the percentage of the population that is awakened. Markov and nonlinear dynamic models have been developed to predict an individual's sleep structure during the night. However, both of these models have limitations. The Markov model only accounts for whether an aircraft event occurred not the noise level or other sound characteristics of the event that may affect the degree of disturbance. The nonlinear dynamic models were developed to describe normal sleep regulation and do not have a noise effects component. In addition, the nonlinear dynamic models have slow dynamics which make it difficult to predict short duration awakenings which occur both spontaneously and as a result of nighttime noise exposure. The purpose of this research was to examine these sleep structure models to determine how they could be altered to predict the effect of aircraft noise on sleep. Different approaches for adding a noise level dependence to the Markov Model was explored and the modified model was validated by comparing predictions to behavioral awakening data. In order to determine how to add faster dynamics to the nonlinear dynamic sleep models it was necessary to have a more detailed sleep stage classification than was available from visual scoring of sleep data. An automatic sleep stage classification algorithm was developed which extracts different features of polysomnography data including the

  20. Status of noise technology for advanced supersonic cruise aircraft

    NASA Technical Reports Server (NTRS)

    Stone, J. R.; Gutierrez, O. A.

    1980-01-01

    Developments in acoustic technology applicable to advanced supersonic cruise aircraft, particularly those which relate to jet noise and its suppression are reviewed. The noise reducing potential of high radius ratio, inverted velocity profile coannular jets is demonstrated by model scale results from a wide range of nozzle geometries, including some simulated flight cases. These results were verified statistically at large scale on a variable cycle engine (VCE) testbed. A preliminary assessment of potential VCE noise sources such as fan and core noise is made, based on the testbed data. Recent advances in the understanding of flight effects are reviewed. The status of component noise prediction methods is assessed on the basis of recent test data, and the remaining problem areas are outlined.

  1. Effects of aircraft noise on human sleep.

    NASA Technical Reports Server (NTRS)

    Lukas, J. S.

    1972-01-01

    Under controlled conditions in two test rooms, studies were made of the response of sleeping subjects to the stimuli of simulated sonic booms and subsonic jet aircraft noise. Children were relatively nonresponsive to the stimuli. In general, the older the subject, the more likely is behavioral awakening. The response rates to the two types of stimuli were essentially the same. The stimulus intensity had little, if any, effect on frequency of arousal, although other degrees of response did increase.

  2. An Analysis of Aircraft Flyover Noise

    DTIC Science & Technology

    1978-04-01

    characteristics of other aircraft and revised noise level versus distance curves calculated. Comparison of these revised curves with available measured data and...with levels predicted using the current NOISEMAP procedures should be made. The possible impact of a revision to the present prediction procedures...study, it is recommended that revisions be considered for the relationship currently used in the NOISEMAP procedure to relate A-level and SEL as a

  3. Acoustic guide for noise-transmission testing of aircraft

    NASA Technical Reports Server (NTRS)

    Vaicaitis, Rimas (Inventor)

    1987-01-01

    Selective testing of aircraft or other vehicular components without requiring disassembly of the vehicle or components was accomplished by using a portable guide apparatus. The device consists of a broadband noise source, a guide to direct the acoustic energy, soft sealing insulation to seal the guide to the noise source and to the vehicle component, and noise measurement microphones, both outside the vehicle at the acoustic guide output and inside the vehicle to receive attenuated sound. By directing acoustic energy only to selected components of a vehicle via the acoustic guide, it is possible to test a specific component, such as a door or window, without picking up extraneous noise which may be transmitted to the vehicle interior through other components or structure. This effect is achieved because no acoustic energy strikes the vehicle exterior except at the selected component. Also, since the test component remains attached to the vehicle, component dynamics with vehicle frame are not altered.

  4. Airport take-off noise assessment aimed at identify responsible aircraft classes.

    PubMed

    Sanchez-Perez, Luis A; Sanchez-Fernandez, Luis P; Shaout, Adnan; Suarez-Guerra, Sergio

    2016-01-15

    Assessment of aircraft noise is an important task of nowadays airports in order to fight environmental noise pollution given the recent discoveries on the exposure negative effects on human health. Noise monitoring and estimation around airports mostly use aircraft noise signals only for computing statistical indicators and depends on additional data sources so as to determine required inputs such as the aircraft class responsible for noise pollution. In this sense, the noise monitoring and estimation systems have been tried to improve by creating methods for obtaining more information from aircraft noise signals, especially real-time aircraft class recognition. Consequently, this paper proposes a multilayer neural-fuzzy model for aircraft class recognition based on take-off noise signal segmentation. It uses a fuzzy inference system to build a final response for each class p based on the aggregation of K parallel neural networks outputs Op(k) with respect to Linear Predictive Coding (LPC) features extracted from K adjacent signal segments. Based on extensive experiments over two databases with real-time take-off noise measurements, the proposed model performs better than other methods in literature, particularly when aircraft classes are strongly correlated to each other. A new strictly cross-checked database is introduced including more complex classes and real-time take-off noise measurements from modern aircrafts. The new model is at least 5% more accurate with respect to previous database and successfully classifies 87% of measurements in the new database.

  5. Airframe Noise from a Hybrid Wing Body Aircraft Configuration

    NASA Technical Reports Server (NTRS)

    Hutcheson, Florence V.; Spalt, Taylor B.; Brooks, Thomas F.; Plassman, Gerald E.

    2016-01-01

    A high fidelity aeroacoustic test was conducted in the NASA Langley 14- by 22-Foot Subsonic Tunnel to establish a detailed database of component noise for a 5.8% scale HWB aircraft configuration. The model has a modular design, which includes a drooped and a stowed wing leading edge, deflectable elevons, twin verticals, and a landing gear system with geometrically scaled wheel-wells. The model is mounted inverted in the test section and noise measurements are acquired at different streamwise stations from an overhead microphone phased array and from overhead and sideline microphones. Noise source distribution maps and component noise spectra are presented for airframe configurations representing two different approach flight conditions. Array measurements performed along the aircraft flyover line show the main landing gear to be the dominant contributor to the total airframe noise, followed by the nose gear, the inboard side-edges of the LE droop, the wing tip/LE droop outboard side-edges, and the side-edges of deployed elevons. Velocity dependence and flyover directivity are presented for the main noise components. Decorrelation effects from turbulence scattering on spectral levels measured with the microphone phased array are discussed. Finally, noise directivity maps obtained from the overhead and sideline microphone measurements for the landing gear system are provided for a broad range of observer locations.

  6. An aircraft noise pollution model for trajectory optimization

    NASA Technical Reports Server (NTRS)

    Barkana, A.; Cook, G.

    1976-01-01

    A mathematical model describing the generation of aircraft noise is developed with the ultimate purpose of reducing noise (noise-optimizing landing trajectories) in terminal areas. While the model is for a specific aircraft (Boeing 737), the methodology would be applicable to a wide variety of aircraft. The model is used to obtain a footprint on the ground inside of which the noise level is at or above 70 dB.

  7. Annoyance by aircraft noise and fear of overflying aircraft in relation to attitudes toward the environment and community

    NASA Technical Reports Server (NTRS)

    Loeb, M.; Moran, S. V.

    1977-01-01

    It has been suggested that expressions of annoyance attributable to aircraft noise may reflect in part fear of aircraft overflights and possible crashes. If this is true, then residents of areas where crashes have occurred should express more annoyance. To test this hypothesis, 50 residents of an Albany, New York area where an aircraft crash producing fatalities recently occurred and 50 residents of a comparable nearby area without such a history, were asked to respond to a 'Quality of Life Questionnaire.' Among the items were some designed to test annoyance by noise and fear of aircraft overflights. It was predicted that those in the crash area would express more fear and would more often identify aircraft as a noise source. These hypotheses were sustained. A near-replication was carried out in Louisville, Kentucky; results were much the same. Analyses indicated that for the crash-area groups, there was associating of aircraft fear and noise annoyance responses; this was true to an apparently lesser extent for non-crash groups. The greater annoyance of crash groups by aircraft community noise apparently does not carry over to situations in which aircraft noise is assessed in the laboratory.

  8. Relationship between Aircraft Noise Contour Area and Noise Levels at Certification Points

    NASA Technical Reports Server (NTRS)

    Powell, Clemans A.

    2003-01-01

    The use of sound exposure level contour area reduction has been proposed as an alternative or supplemental metric of progress and success for the NASA Quiet Aircraft Technology program, which currently uses the average of predicted noise reductions at three community locations. As the program has expanded to include reductions in airframe noise as well as reduction due to optimization of operating procedures for lower noise, there is concern that the three-point methodology may not represent a fair measure of benefit to airport communities. This paper addresses several topics related to this proposal: (1) an analytical basis for a relationship between certification noise levels and noise contour areas for departure operations is developed, (2) the relationship between predicted noise contour area and the noise levels measured or predicted at the certification measurement points is examined for a wide range of commercial and business aircraft, and (3) reductions in contour area for low-noise approach scenarios are predicted and equivalent reductions in source noise are determined.

  9. Aircraft Noise Prediction Program theoretical manual: Propeller aerodynamics and noise

    NASA Technical Reports Server (NTRS)

    Zorumski, W. E. (Editor); Weir, D. S. (Editor)

    1986-01-01

    The prediction sequence used in the aircraft noise prediction program (ANOPP) is described. The elements of the sequence are called program modules. The first group of modules analyzes the propeller geometry, the aerodynamics, including both potential and boundary-layer flow, the propeller performance, and the surface loading distribution. This group of modules is based entirely on aerodynamic strip theory. The next group of modules deals with the first group. Predictions of periodic thickness and loading noise are determined with time-domain methods. Broadband noise is predicted by a semiempirical method. Near-field predictions of fuselage surface pressrues include the effects of boundary layer refraction and scattering. Far-field predictions include atmospheric and ground effects.

  10. Jet engine noise source and noise footprint computer programs

    NASA Technical Reports Server (NTRS)

    Dunn, D. G.; Peart, N. A.; Miller, D. L.; Crowley, K. C.

    1972-01-01

    Calculation procedures are presented for predicting maximum passby noise levels and contours (footprints) of conventional jet aircraft with or without noise suppression devices. The procedures have been computerized and a user's guide is presented for the computer programs to be used in predicting the noise characteristics during aircraft takeoffs, fly-over, and/or landing operations.

  11. Effects of motion on jet exhaust noise from aircraft

    NASA Technical Reports Server (NTRS)

    Chun, K. S.; Berman, C. H.; Cowan, S. J.

    1976-01-01

    The various problems involved in the evaluation of the jet noise field prevailing between an observer on the ground and an aircraft in flight in a typical takeoff or landing approach pattern were studied. Areas examined include: (1) literature survey and preliminary investigation, (2) propagation effects, (3) source alteration effects, and (4) investigation of verification techniques. Sixteen problem areas were identified and studied. Six follow-up programs were recommended for further work. The results and the proposed follow-on programs provide a practical general technique for predicting flyover jet noise for conventional jet nozzles.

  12. Teaching Doppler Effect with a passing noise source

    NASA Astrophysics Data System (ADS)

    Costa, Ivan F.; Mocellin, Alexandra

    2010-07-01

    The noise pitch variation of a passing noise source allows a low cost experimental approach to calculate speed and, for the first time, distance. We adjusted the recorded noise pitch variation to the Doppler shift equation for sound. We did this by taking into account the frequency delay due to the sound source displacement and performing a Fast Fourier Transform (FFT) of the noise signal using free software. This experimental method was successfully applied to aircraft and automobiles.

  13. Lightweight sidewalls for aircraft interior noise control

    NASA Technical Reports Server (NTRS)

    May, D. N.; Plotkin, K. J.; Selden, R. G.; Sharp, B. H.

    1985-01-01

    A theoretical and experimental study was performed to devise lightweight sidewalls for turboprop aircraft. Seven concepts for new sidewalls were analyzed and tested for noise reduction using flat panels of 1.2 m x 1.8 m (4 ft x 6 ft), some of which were aircraft-type constructions and some of which were simpler, easier-to-construct panels to test the functioning of an acoustic principle. Aircraft-application sidewalls were then conceived for each of the seven concepts, and were subjectively evaluated for their ability to meet aircraft nonacoustic design requirements. As a result of the above, the following sidewall concepts were recommended for further investigation: a sidewall in which the interior cavity is vented to ceiling and underfloor areas; sidewalls with wall-mounted resonators, one having a conventional trim panel and one a limp one; and a sidewall with a stiff outer wall and a limp trim panel. These sidewalls appear to promise lower weights than conventional sidewalls adjusted to meet similar acoustic requirements, and further development may prove them to be practical.

  14. Noise transmission loss of aircraft panels using acoustic intensity methods

    NASA Technical Reports Server (NTRS)

    Mcgary, M. C.

    1982-01-01

    The two-microphone, cross-spectral, acoustic intensity measurement technique was used to determine the acoustic transmission loss of three different aircraft panels. The study was conducted in the transmission loss apparatus in the Langley aircraft noise reduction laboratory.

  15. Active Aircraft Pylon Noise Control System

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H. (Inventor); Czech, Michael J (Inventor); Elmiligui, Alaa A. (Inventor)

    2015-01-01

    An active pylon noise control system for an aircraft includes a pylon structure connecting an engine system with an airframe surface of the aircraft and having at least one aperture to supply a gas or fluid therethrough, an intake portion attached to the pylon structure to intake a gas or fluid, a regulator connected with the intake portion via a plurality of pipes, to regulate a pressure of the gas or fluid, a plenum chamber formed within the pylon structure and connected with the regulator, and configured to receive the gas or fluid as regulated by the regulator, and a plurality of injectors in communication with the plenum chamber to actively inject the gas or fluid through the plurality of apertures of the pylon structure.

  16. Aircraft noise-induced building vibrations. [human annoyance responses

    NASA Technical Reports Server (NTRS)

    Stephens, D. G.; Mayes, W. H.

    1979-01-01

    The outdoor/indoor noise levels and associated vibration levels resulting from aircraft and nonaircraft events are recorded at 11 homesites, a historic building, and a school. In addition, limited subjective tests are conducted to examine the human detection/annoyance thresholds for building vibration and rattle caused by aircraft noise. Results include relationships between aircraft noise and building vibration and between vibration and human response. Comparisons of building vibration data with existing criteria for building damage and human response are also considered.

  17. Engine-induced structural-borne noise in a general aviation aircraft

    NASA Technical Reports Server (NTRS)

    Unruh, J. F.; Scheidt, D. C.; Pomerening, D. J.

    1979-01-01

    Structural borne interior noise in a single engine general aviation aircraft was studied to determine the importance of engine induced structural borne noise and to determine the necessary modeling requirements for the prediction of structural borne interior noise. Engine attached/detached ground test data show that engine induced structural borne noise is a primary interior noise source for the single engine test aircraft, cabin noise is highly influenced by responses at the propeller tone, and cabin acoustic resonances can influence overall noise levels. Results from structural and acoustic finite element coupled models of the test aircraft show that wall flexibility has a strong influence on fundamental cabin acoustic resonances, the lightweight fuselage structure has a high modal density, and finite element analysis procedures are appropriate for the prediction of structural borne noise.

  18. Structureborne noise in aircraft: Modal tests

    NASA Technical Reports Server (NTRS)

    Clevenson, S. A.; Metcalf, V. L.

    1986-01-01

    As part of an investigation to develop measurement techniques for structureborne noise, three modal surveys have been conducted on an OV-10A aircraft and the results have been presented. The purpose of the modal surveys was to identify suitable locations for mounting accelerometer and strain gages in subsequent tests in which transfer functions relating wing vibration to interior noise were to be determined. These surveys are as follows:(1) wing/fuselage modal survey utilizing one shaker under the right wing; (2) complete wing modal survey utilizing two shakers, one under each wing; and (3) fuselage side panel modal survey utilizing a small instrumented hammer. The predominant frequencies and damping ratios for each analysis were listed in tables. The primary mode shapes at the lower frequencies and at frequencies near the expected engine driving frequencies have been shown for each survey.

  19. System Noise Assessment and the Potential for a Low Noise Hybrid Wing Body Aircraft with Open Rotor Propulsion

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H.; Burley, Casey L.; Lopes, Leonard V.; Bahr, Christopher J.; Gern, Frank H.; VanZante, Dale E.

    2014-01-01

    An aircraft system noise assessment was conducted for a hybrid wing body freighter aircraft concept configured with three open rotor engines. The primary objective of the study was to determine the aircraft system level noise given the significant impact of installation effects including shielding the open rotor noise by the airframe. The aircraft was designed to carry a payload of 100,000 lbs on a 6,500 nautical mile mission. An experimental database was used to establish the propulsion airframe aeroacoustic installation effects including those from shielding by the airframe planform, interactions with the control surfaces, and additional noise reduction technologies. A second objective of the study applied the impacts of projected low noise airframe technology and a projection of advanced low noise rotors appropriate for the NASA N+2 2025 timeframe. With the projection of low noise rotors and installation effects, the aircraft system level was 26.0 EPNLdB below Stage 4 level with the engine installed at 1.0 rotor diameters upstream of the trailing edge. Moving the engine to 1.5 rotor diameters brought the system level noise to 30.8 EPNLdB below Stage 4. At these locations on the airframe, the integrated level of installation effects including shielding can be as much as 20 EPNLdB cumulative in addition to lower engine source noise from advanced low noise rotors. And finally, an additional set of technology effects were identified and the potential impact at the system level was estimated for noise only without assessing the impact on aircraft performance. If these additional effects were to be included it is estimated that the potential aircraft system noise could reach as low as 38.0 EPNLdB cumulative below Stage 4.

  20. Auralization Architectures for NASA?s Next Generation Aircraft Noise Prediction Program

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Lopes, Leonard V.; Burley, Casey L.; Aumann, Aric R.

    2013-01-01

    Aircraft community noise is a significant concern due to continued growth in air traffic, increasingly stringent environmental goals, and operational limitations imposed by airport authorities. The assessment of human response to noise from future aircraft can only be afforded through laboratory testing using simulated flyover noise. Recent work by the authors demonstrated the ability to auralize predicted flyover noise for a state-of-the-art reference aircraft and a future hybrid wing body aircraft concept. This auralization used source noise predictions from NASA's Aircraft NOise Prediction Program (ANOPP) as input. The results from this process demonstrated that auralization based upon system noise predictions is consistent with, and complementary to, system noise predictions alone. To further develop and validate the auralization process, improvements to the interfaces between the synthesis capability and the system noise tools are required. This paper describes the key elements required for accurate noise synthesis and introduces auralization architectures for use with the next-generation ANOPP (ANOPP2). The architectures are built around a new auralization library and its associated Application Programming Interface (API) that utilize ANOPP2 APIs to access data required for auralization. The architectures are designed to make the process of auralizing flyover noise a common element of system noise prediction.

  1. The community response to aircraft noise around six Spanish airports

    NASA Astrophysics Data System (ADS)

    Garcia, A.; Faus, L. J.; Garcia, A. M.

    1993-06-01

    The community response to aircraft noise has been studied through a social survey. A total of 1800 persons living in the vicinity of six major Spanish airports have been interviewed at their homes concerning the environmental quality of the area, dissatisfaction with road traffic noise and aircraft noise, activities interfered with by noise, most disturbing aircraft types, and subjective evaluation of airport impact. All the responses obtained in this survey have been compared with aircraft noise levels corresponding to the residence locations of the people interviewed (values of NEF levels were calculated with the INM model). The results obtained in this work allow one to evaluate the impact of aircraft noise under a wide range of different situations.

  2. Analytical model for investigation of interior noise characteristics in aircraft with multiple propellers including synchrophasing

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.

    1986-01-01

    A simplified analytical model of transmission of noise into the interior of propeller-driven aircraft has been developed. The analysis includes directivity and relative phase effects of the propeller noise sources, and leads to a closed form solution for the coupled motion between the interior and exterior fields via the shell (fuselage) vibrational response. Various situations commonly encountered in considering sound transmission into aircraft fuselages are investigated analytically and the results obtained are compared to measurements in real aircraft. In general the model has proved successful in identifying basic mechanisms behind noise transmission phenomena.

  3. Review of subjective measures of human response to aircraft noise

    NASA Technical Reports Server (NTRS)

    Cawthorn, J. M.; Mayes, W. H.

    1976-01-01

    The development of aircraft noise rating scales and indexes is reviewed up to the present time. Single event scales, multiple event indexes, and their interrelation with each other, are considered. Research requirements for further refinement and development of aircraft noise rating quantification factors are discussed.

  4. Open Rotor Noise Shielding by Blended-Wing-Body Aircraft

    NASA Technical Reports Server (NTRS)

    Guo, Yueping; Czech, Michael J.; Thomas, Russell H.

    2015-01-01

    This paper presents an analysis of open rotor noise shielding by Blended Wing Body (BWB) aircraft by using model scale test data acquired in the Boeing Low Speed Aeroacoustic Facility (LSAF) with a legacy F7/A7 rotor model and a simplified BWB platform. The objective of the analysis is the understanding of the shielding features of the BWB and the method of application of the shielding data for noise studies of BWB aircraft with open rotor propulsion. By studying the directivity patterns of individual tones, it is shown that though the tonal energy distribution and the spectral content of the wind tunnel test model, and thus its total noise, may differ from those of more advanced rotor designs, the individual tones follow directivity patterns that characterize far field radiations of modern open rotors, ensuring the validity of the use of this shielding data. Thus, open rotor tonal noise shielding should be categorized into front rotor tones, aft rotor tones and interaction tones, not only because of the different directivities of the three groups of tones, but also due to the differences in their source locations and coherence features, which make the respective shielding characteristics of the three groups of tones distinctly different from each other. To reveal the parametric trends of the BWB shielding effects, results are presented with variations in frequency, far field emission angle, rotor operational condition, engine installation geometry, and local airframe features. These results prepare the way for the development of parametric models for the shielding effects in prediction tools.

  5. General Aviation Interior Noise. Part 1; Source/Path Identification

    NASA Technical Reports Server (NTRS)

    Unruh, James F.; Till, Paul D.; Palumbo, Daniel L. (Technical Monitor)

    2002-01-01

    There were two primary objectives of the research effort reported herein. The first objective was to identify and evaluate noise source/path identification technology applicable to single engine propeller driven aircraft that can be used to identify interior noise sources originating from structure-borne engine/propeller vibration, airborne propeller transmission, airborne engine exhaust noise, and engine case radiation. The approach taken to identify the contributions of each of these possible sources was first to conduct a Principal Component Analysis (PCA) of an in-flight noise and vibration database acquired on a Cessna Model 182E aircraft. The second objective was to develop and evaluate advanced technology for noise source ranking of interior panel groups such as the aircraft windshield, instrument panel, firewall, and door/window panels within the cabin of a single engine propeller driven aircraft. The technology employed was that of Acoustic Holography (AH). AH was applied to the test aircraft by acquiring a series of in-flight microphone array measurements within the aircraft cabin and correlating the measurements via PCA. The source contributions of the various panel groups leading to the array measurements were then synthesized by solving the inverse problem using the boundary element model.

  6. Community sensitivity to changes in aircraft noise exposure

    NASA Technical Reports Server (NTRS)

    Fidell, S.; Horonjeff, R.; Teffeteller, S.; Pearsons, K.

    1981-01-01

    Interviews were conducted in the vicinity of Burbank Airport during a four month period during which a counterbalanced series of changes in aircraft noise exposure occurred due to runway repairs. Another interview was undertaken approximately one year after completion of the initial runway repairs. Noise measurements were made in conjunction with administration of a brief questionnaire to a near exhaustive sample of residents in four airport neighborhoods. The magnitude and direction of change of annoyance with aircraft noise exposure corresponded closely to the actual changes in physical exposure. Estimates were made of time constants for the rate of change of attitudes toward aircraft noise.

  7. Aircraft noise in the region of the Bucharest-Otopeni Airport. [noise pollution in airport environment

    NASA Technical Reports Server (NTRS)

    Costescu, M.; Gherghel, C.; Curtoglu, A.

    1974-01-01

    Aircraft noise, especially in the region adjoining airports, constitutes a problem that will be aggravated in the near future because of increasing aircraft traffic and the appearance of new types of large tonnage aircraft with continuously increasing powers and speeds. Criteria for the evaluation of aircraft noise are reported and some results of studies carried out in the region of Bucharest-Otopeni Airport are detailed.

  8. Variability of annoyance response due to aircraft noise

    NASA Technical Reports Server (NTRS)

    Dempsey, T. K.; Cawthorn, J. M.

    1979-01-01

    An investigation was conducted to study the variability in the response of subjects participating in noise experiments. This paper presents a description of a model developed to include this variability which incorporates an aircraft-noise adaptation level or an annoyance calibration for each individual. The results indicate that the use of an aircraft-noise adaption level improved prediction accuracy of annoyance responses (and simultaneously reduced response variation).

  9. Night time aircraft noise exposure and children's cognitive performance.

    PubMed

    Stansfeld, Stephen; Hygge, Staffan; Clark, Charlotte; Alfred, Tamuno

    2010-01-01

    Chronic aircraft noise exposure in children is associated with impairment of reading and long-term memory. Most studies have not differentiated between day or nighttime noise exposure. It has been hypothesized that sleep disturbance might mediate the association of aircraft noise exposure and cognitive impairment in children. This study involves secondary analysis of data from the Munich Study and the UK Road Traffic and Aircraft Noise Exposure and Children's Cognition and Health (RANCH) Study sample to test this. In the Munich study, 330 children were assessed on cognitive measures in three measurement waves a year apart, before and after the switchover of airports. Self-reports of sleep quality were analyzed across airports, aircraft noise exposure and measurement wave to test whether changes in nighttime noise exposure had any effect on reported sleep quality, and whether this showed the same pattern as for changes in cognitive performance. For the UK sample of the RANCH study, night noise contour information was linked to the children's home and related to sleep disturbance and cognitive performance. In the Munich study, analysis of sleep quality questions showed no consistent interactions between airport, noise, and measurement wave, suggesting that poor sleep quality does not mediate the association between noise exposure and cognition. Daytime and nighttime aircraft noise exposure was highly correlated in the RANCH study. Although night noise exposure was significantly associated with impaired reading and recognition memory, once home night noise exposure was centered on daytime school noise exposure, night noise had no additional effect to daytime noise exposure. These analyses took advantage of secondary data available from two studies of aircraft noise and cognition. They were not initially designed to examine sleep disturbance and cognition, and thus, there are methodological limitations which make it less than ideal in giving definitive answers to these

  10. Towards Full Aircraft Airframe Noise Prediction: Lattice Boltzmann Simulations

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Fares, Ehab; Casalino, Damiano

    2014-01-01

    Computational results for an 18%-scale, semi-span Gulfstream aircraft model are presented. Exa Corporation's lattice Boltzmann PowerFLOW(trademark) solver was used to perform time-dependent simulations of the flow field associated with this high-fidelity aircraft model. The simulations were obtained for free-air at a Mach number of 0.2 with the flap deflected at 39 deg (landing configuration). We focused on accurately predicting the prominent noise sources at the flap tips and main landing gear for the two baseline configurations, namely, landing flap setting without and with gear deployed. Capitalizing on the inherently transient nature of the lattice Boltzmann formulation, the complex time-dependent flow features associated with the flap were resolved very accurately and efficiently. To properly simulate the noise sources over a broad frequency range, the tailored grid was very dense near the flap inboard and outboard tips. Extensive comparison of the computed time-averaged and unsteady surface pressures with wind tunnel measurements showed excellent agreement for the global aerodynamic characteristics and the local flow field at the flap inboard and outboard tips and the main landing gear. In particular, the computed fluctuating surface pressure field for the flap agreed well with the measurements in both amplitude and frequency content, indicating that the prominent airframe noise sources at the tips were captured successfully. Gear-flap interaction effects were remarkably well predicted and were shown to affect only the inboard flap tip, altering the steady and unsteady pressure fields in that region. The simulated farfield noise spectra for both baseline configurations, obtained using a Ffowcs-Williams and Hawkings acoustic analogy approach, were shown to be in close agreement with measured values.

  11. Supporting statement for community study of human response to aircraft noise

    NASA Technical Reports Server (NTRS)

    Dempsey, T. K.; Deloach, R.; Stephens, D. G.

    1980-01-01

    A study plan for quantifying the relationship between human annoyance and the noise level of individual aircraft events is studied. The validity of various noise descriptors or noise metrics for quantifying aircraft noise levels are assessed.

  12. Perceived Noise Analysis for Offset Jets Applied to Commercial Supersonic Aircraft

    NASA Technical Reports Server (NTRS)

    Huff, Dennis L.; Henderson, Brenda S.; Berton, Jeffrey J.; Seidel, Jonathan A.

    2016-01-01

    A systems analysis was performed with experimental jet noise data, engine/aircraft performance codes and aircraft noise prediction codes to assess takeoff noise levels and mission range for conceptual supersonic commercial aircraft. A parametric study was done to identify viable engine cycles that meet NASA's N+2 goals for noise and performance. Model scale data from offset jets were used as input to the aircraft noise prediction code to determine the expected sound levels for the lateral certification point where jet noise dominates over all other noise sources. The noise predictions were used to determine the optimal orientation of the offset nozzles to minimize the noise at the lateral microphone location. An alternative takeoff procedure called "programmed lapse rate" was evaluated for noise reduction benefits. Results show there are two types of engines that provide acceptable mission range performance; one is a conventional mixed-flow turbofan and the other is a three-stream variable-cycle engine. Separate flow offset nozzles reduce the noise directed toward the thicker side of the outer flow stream, but have less benefit as the core nozzle pressure ratio is reduced. At the systems level for a three-engine N+2 aircraft with full throttle takeoff, there is a 1.4 EPNdB margin to Chapter 3 noise regulations predicted for the lateral certification point (assuming jet noise dominates). With a 10% reduction in thrust just after clearing the runway, the margin increases to 5.5 EPNdB. Margins to Chapter 4 and Chapter 14 levels will depend on the cumulative split between the three certification points, but it appears that low specific thrust engines with a 10% reduction in thrust (programmed lapse rate) can come close to meeting Chapter 14 noise levels. Further noise reduction is possible with engine oversizing and derated takeoff, but more detailed mission studies are needed to investigate the range impacts as well as the practical limits for safety and takeoff

  13. The Low-Noise Potential of Distributed Propulsion on a Catamaran Aircraft

    NASA Technical Reports Server (NTRS)

    Posey, Joe W.; Tinetti, A. F.; Dunn, M. H.

    2006-01-01

    The noise shielding potential of an inboard-wing catamaran aircraft when coupled with distributed propulsion is examined. Here, only low-frequency jet noise from mid-wing-mounted engines is considered. Because low frequencies are the most difficult to shield, these calculations put a lower bound on the potential shielding benefit. In this proof-of-concept study, simple physical models are used to describe the 3-D scattering of jet noise by conceptualized catamaran aircraft. The Fast Scattering Code is used to predict noise levels on and about the aircraft. Shielding results are presented for several catamaran type geometries and simple noise source configurations representative of distributed propulsion radiation. Computational analyses are presented that demonstrate the shielding benefits of distributed propulsion and of increasing the width of the inboard wing. Also, sample calculations using the FSC are presented that demonstrate additional noise reduction on the aircraft fuselage by the use of acoustic liners on the inboard wing trailing edge. A full conceptual aircraft design would have to be analyzed over a complete mission to more accurately quantify community noise levels and aircraft performance, but the present shielding calculations show that a large acoustic benefit could be achieved by combining distributed propulsion and liner technology with a twin-fuselage planform.

  14. Hybrid Wing Body Aircraft System Noise Assessment with Propulsion Airframe Aeroacoustic Experiments

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H.; Burley, Casey L.; Olson, Erik D.

    2010-01-01

    A system noise assessment of a hybrid wing body configuration was performed using NASA s best available aircraft models, engine model, and system noise assessment method. A propulsion airframe aeroacoustic effects experimental database for key noise sources and interaction effects was used to provide data directly in the noise assessment where prediction methods are inadequate. NASA engine and aircraft system models were created to define the hybrid wing body aircraft concept as a twin engine aircraft with a 7500 nautical mile mission. The engines were modeled as existing technology high bypass ratio turbofans. The baseline hybrid wing body aircraft was assessed at 22 dB cumulative below the FAA Stage 4 certification level. To determine the potential for noise reduction with relatively near term technologies, seven other configurations were assessed beginning with moving the engines two fan nozzle diameters upstream of the trailing edge and then adding technologies for reduction of the highest noise sources. Aft radiated noise was expected to be the most challenging to reduce and, therefore, the experimental database focused on jet nozzle and pylon configurations that could reduce jet noise through a combination of source reduction and shielding effectiveness. The best configuration for reduction of jet noise used state-of-the-art technology chevrons with a pylon above the engine in the crown position. This configuration resulted in jet source noise reduction, favorable azimuthal directivity, and noise source relocation upstream where it is more effectively shielded by the limited airframe surface, and additional fan noise attenuation from acoustic liner on the crown pylon internal surfaces. Vertical and elevon surfaces were also assessed to add shielding area. The elevon deflection above the trailing edge showed some small additional noise reduction whereas vertical surfaces resulted in a slight noise increase. With the effects of the configurations from the

  15. General Aviation Interior Noise. Part 2; In-Flight Source/Verification

    NASA Technical Reports Server (NTRS)

    Unruh, James F.; Till, Paul D.; Palumbo, Daniel L. (Technical Monitor)

    2002-01-01

    The technical approach made use of the Cessna Model 182E aircraft used in the previous effort as a test bed for noise control application. The present phase of the project reports on flight test results during application of various passive noise treatments in an attempt to verify the noise sources and paths for the aircraft. The data presented establishes the level of interior noise control that can be expected for various passive noise control applications within the aircraft cabin. Subsequent testing will address specific testing to demonstrate the technology available to meet a specified level of noise control by application of passive and/or active noise control technology.

  16. Auralization of NASA N+2 Aircraft Concepts from System Noise Predictions

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Burley, Casey L.; Thomas, Russel H.

    2016-01-01

    Auralization of aircraft flyover noise provides an auditory experience that complements integrated metrics obtained from system noise predictions. Recent efforts have focused on auralization methods development, specifically the process by which source noise information obtained from semi-empirical models, computational aeroacoustic analyses, and wind tunnel and flight test data, are used for simulated flyover noise at a receiver on the ground. The primary focus of this work, however, is to develop full vehicle auralizations in order to explore the distinguishing features of NASA's N+2 aircraft vis-à-vis current fleet reference vehicles for single-aisle and large twin-aisle classes. Some features can be seen in metric time histories associated with aircraft noise certification, e.g., tone-corrected perceived noise level used in the calculation of effective perceived noise level. Other features can be observed in sound quality metrics, e.g., loudness, sharpness, roughness, fluctuation strength and tone-to-noise ratio. A psychoacoustic annoyance model is employed to establish the relationship between sound quality metrics and noise certification metrics. Finally, the auralizations will serve as the basis for a separate psychoacoustic study aimed at assessing how well aircraft noise certification metrics predict human annoyance for these advanced vehicle concepts.

  17. NASA Glenn's Contributions to Aircraft Engine Noise Research

    NASA Technical Reports Server (NTRS)

    Huff, Dennis L.

    2013-01-01

    This report reviews all engine noise research conducted at the NASA Glenn Research Center over the past 70 years. This report includes a historical perspective of the Center and the facilities used to conduct the research. Major noise research programs are highlighted to show their impact on industry and on the development of aircraft noise reduction technology. Noise reduction trends are discussed, and future aircraft concepts are presented. Since the 1960s, research results show that the average perceived noise level has been reduced by about 20 decibels (dB). Studies also show that, depending on the size of the airport, the aircraft fleet mix, and the actual growth in air travel, another 15 to 17 dB reduction will be required to achieve NASA's long-term goal of providing technologies to limit objectionable noise to the boundaries of an average airport.

  18. NASA Glenn's Contributions to Aircraft Engine Noise Research

    NASA Technical Reports Server (NTRS)

    Huff, Dennis L.

    2014-01-01

    This presentation reviews engine noise research conducted at the NASA Glenn Research Center over the past 70 years. This report includes a historical perspective of the Center and the facilities used to conduct the research. Major noise research programs are highlighted to show their impact on industry and on the development of aircraft noise reduction technology. Noise reduction trends are discussed, and future aircraft concepts are presented. Since the 1960s, research results show that the average perceived noise level has been reduced by about 20 decibels (dB). Studies also show that, depending on the size of the airport, the aircraft fleet mix, and the actual growth in air travel, another 15 to 17 dB reduction will be required to achieve NASAs long-term goal of providing technologies to limit objectionable noise to the boundaries of an average airport.

  19. The effects of road traffic and aircraft noise exposure on children's episodic memory: the RANCH project.

    PubMed

    Matheson, Mark; Clark, Charlotte; Martin, Rocio; van Kempen, Elise; Haines, Mary; Barrio, Isabel Lopez; Hygge, Staffan; Stansfeld, Stephen

    2010-01-01

    Previous studies have found that chronic exposure to aircraft noise has a negative effect on children's performance on tests of episodic memory. The present study extended the design of earlier studies in three ways: firstly, by examining the effects of two noise sources, aircraft and road traffic, secondly, by examining exposure-effect relationships, and thirdly, by carrying out parallel field studies in three European countries, allowing cross-country comparisons to be made. A total of 2844 children aged between 8 years 10 months and 12 years 10 months (mean age 10 years 6 months) completed classroom-based tests of cued recall, recognition memory and prospective memory. Questionnaires were also completed by the children and their parents in order to provide information about socioeconomic context. Multilevel modeling analysis revealed aircraft noise to be associated with an impairment of recognition memory in a linear exposure-effect relationship. The analysis also found road traffic noise to be associated with improved performance on cued recall in a linear exposure-effect relationship. No significant association was found between exposure to aircraft noise and cued recall or prospective memory. Likewise, no significant association was found between road traffic noise and recognition or prospective memory. Taken together, these findings indicate that exposure to aircraft noise and road traffic noise can impact on certain aspects of children's episodic memory.

  20. Cabin Noise Control for Twin Engine General Aviation Aircraft

    NASA Technical Reports Server (NTRS)

    Vaicaitis, R.; Slazak, M.

    1982-01-01

    An analytical model based on modal analysis was developed to predict the noise transmission into a twin-engine light aircraft. The model was applied to optimize the interior noise to an A-weighted level of 85 dBA. To achieve the required noise attenuation, add-on treatments in the form of honeycomb panels, damping tapes, acoustic blankets, septum barriers and limp trim panels were added to the existing structure. The added weight of the noise control treatment is about 1.1 percent of the total gross take-off weight of the aircraft.

  1. General aviation aircraft interior noise problem: Some suggested solutions

    NASA Technical Reports Server (NTRS)

    Roskam, J.; Navaneethan, R.

    1984-01-01

    Laboratory investigation of sound transmission through panels and the use of modern data analysis techniques applied to actual aircraft is used to determine methods to reduce general aviation interior noise. The experimental noise reduction characteristics of stiffened flat and curved panels with damping treatment are discussed. The experimental results of double-wall panels used in the general aviation industry are given. The effects of skin panel material, fiberglass insulation and trim panel material on the noise reduction characteristics of double-wall panels are investigated. With few modifications, the classical sound transmission theory can be used to design the interior noise control treatment of aircraft. Acoustic intensity and analysis procedures are included.

  2. Recommended procedures for measuring aircraft noise and associated parameters

    NASA Technical Reports Server (NTRS)

    Marsh, A. H.

    1977-01-01

    Procedures are recommended for obtaining experimental values of aircraft flyover noise levels (and associated parameters). Specific recommendations are made for test criteria, instrumentation performance requirements, data-acquisition procedures, and test operations. The recommendations are based on state-of-the-art measurement capabilities available in 1976 and are consistent with the measurement objectives of the NASA Aircraft Noise Prediction Program. The recommendations are applicable to measurements of the noise produced by an airplane flying subsonically over (or past) microphones located near the surface of the ground. Aircraft types covered by the recommendations are fixed-wing airplanes powered by turbojet or turbofan engines and using conventional aerodynamic means for takeoff and landing. Various assumptions with respect to subsequent data processing and analysis were made (and are described) and the recommended measurement procedures are compatible with the assumptions. Some areas where additional research is needed relative to aircraft flyover noise measurement techniques are also discussed.

  3. Aircraft noise effects on sleep: mechanisms, mitigation and research needs.

    PubMed

    Basner, Mathias; Griefahn, Barbara; Berg, Martin van den

    2010-01-01

    There is an ample number of laboratory and field studies which provide sufficient evidence that aircraft noise disturbs sleep and, depending on traffic volume and noise levels, may impair behavior and well-being during the day. Although clinical sleep disorders have been shown to be associated with increased risk of cardiovascular diseases, only little is known about the long-term effects of aircraft noise disturbed sleep on health. National and international laws and guidelines try to limit aircraft noise exposure facilitating active and passive noise control to prevent relevant sleep disturbances and its consequences. Adopting the harmonized indicator of the European Union Directive 2002/49/EC, the WHO Night Noise Guideline for Europe (NNG) defines four Lnight , outside ranges associated with different risk levels of sleep disturbance and other health effects ( < 30, 30-40, 40-55, and> 55 dBA). Although traffic patterns differing in number and noise levels of events that lead to varying degrees of sleep disturbance may result in the same Lnight , simulations of nights with up to 200 aircraft noise events per night nicely corroborate expert opinion guidelines formulated in WHO's NNG. In the future, large scale field studies on the effects of nocturnal (aircraft) noise on sleep are needed. They should involve representative samples of the population including vulnerable groups like children and chronically ill subjects. Optimally, these studies are prospective in nature and examine the long-term consequences of noise-induced sleep disturbances. Furthermore, epidemiological case-control studies on the association of nocturnal (aircraft) noise exposure and cardiovascular disease are needed. Despite the existing gaps in knowledge on long-term health effects, sufficient data are available for defining limit values, guidelines and protection concepts, which should be updated with the availability of new data.

  4. On Noise Assessment for Blended Wing Body Aircraft

    NASA Technical Reports Server (NTRS)

    Guo, Yueping; Burley, Casey L; Thomas, Russell H.

    2014-01-01

    A system noise study is presented for the blended-wing-body (BWB) aircraft configured with advanced technologies that are projected to be available in the 2025 timeframe of the NASA N+2 definition. This system noise assessment shows that the noise levels of the baseline configuration, measured by the cumulative Effective Perceived Noise Level (EPNL), have a large margin of 34 dB to the aircraft noise regulation of Stage 4. This confirms the acoustic benefits of the BWB shielding of engine noise, as well as other projected noise reduction technologies, but the noise margins are less than previously published assessments and are short of meeting the NASA N+2 noise goal. In establishing the relevance of the acoustic assessment framework, the design of the BWB configuration, the technical approach of the noise analysis, the databases and prediction tools used in the assessment are first described and discussed. The predicted noise levels and the component decomposition are then analyzed to identify the ranking order of importance of various noise components, revealing the prominence of airframe noise, which holds up the levels at all three noise certification locations and renders engine noise reduction technologies less effective. When projected airframe component noise reduction is added to the HWB configuration, it is shown that the cumulative noise margin to Stage 4 can reach 41.6 dB, nearly at the NASA goal. These results are compared with a previous NASA assessment with a different study framework. The approaches that yield projections of such low noise levels are discussed including aggressive assumptions on future technologies, assumptions on flight profile management, engine installation, and component noise reduction technologies. It is shown that reliable predictions of component noise also play an important role in the system noise assessment. The comparisons and discussions illustrate the importance of practical feasibilities and constraints in aircraft

  5. Noise reduction of a tilt-rotor aircraft including effects on weight and performance

    NASA Technical Reports Server (NTRS)

    Gibs, J.; Stepniewski, W. Z.; Spencer, R.; Kohler, G.

    1973-01-01

    Various methods for far-field noise reduction of a tilt-rotor acoustic signature and the performance and weight tradeoffs which result from modification of the noise sources are considered in this report. In order to provide a realistic approach for the investigation, the Boeing tilt-rotor flight research aircraft (Model 222), was selected as the baseline. This aircraft has undergone considerable engineering development. Its rotor has been manufactured and tested in the Ames full-scale wind tunnel. The study reflects the current state-of-the-art of aircraft design for far-field acoustic signature reduction and is not based solely on an engineering feasibility aircraft. This report supplements a previous study investigating reduction of noise signature through the management of the terminal flight trajectory.

  6. Comparing the relationships between noise level and annoyance in different surveys - A railway noise vs. aircraft and road traffic comparison

    NASA Technical Reports Server (NTRS)

    Fields, J. M.; Walker, J. G.

    1982-01-01

    Annoyance expressed in a railway noise survey is compared with that from two road traffic and three aircraft surveys in order to determine whether responses to various types of environmental noise are source-specific. Railway noise is found to be less annoying than other noises at any given high noise level. Railway noise annoyance rises less rapidly with increasing noise level. At high levels, this gap in reactions averages about 10 dB; it ranges from 4 dB to more than 20 dB. The methods used for comparing the surveys are examined. It is found that methodological uncertainties lead to imprecise comparisons and that different annoyance scales yield different estimates of intersurvey differences.

  7. Potential reduction of en route noise from an advanced turboprop aircraft

    NASA Technical Reports Server (NTRS)

    Dittmar, James H.

    1990-01-01

    When the en route noise of a representative aircraft powered by an eight-blade SR-7 propeller was previously calculated, the noise level was cited as a possible concern associated with the acceptance of advanced turboprop aircraft. Some potential methods for reducing the en route noise were then investigated and are reported. Source noise reductions from increasing the blade number and from operating at higher rotative speed to reach a local minimum noise point were investigated. Greater atmospheric attenuations for higher blade passing frequencies were also indicated. Potential en route noise reductions from these methods were calculated as 9.5 dB (6.5 dB(A)) for a 10-blade redesigned propeller and 15.5 dB (11 dB(A)) for a 12-blade redesigned propeller.

  8. The Insulation of Houses against Noise from Aircraft in Flight.

    ERIC Educational Resources Information Center

    Scholes, W. E.; Parkin, P. H.

    Three groups of traditional houses were insulated against aircraft noise by double glazing and installing sound attenuating ventilator units. For upper floor rooms of two story houses, overall insulations of 35-40 dB were obtainable, providing transmission through the roofs and down flues were also reduced. The noise levels caused by ventilator…

  9. Prediction and reduction of aircraft noise in outdoor environments

    NASA Astrophysics Data System (ADS)

    Tong, Bao N.

    This dissertation investigates the noise due to an en-route aircraft cruising at high altitudes. It offers an improved understanding into the combined effects of atmospheric propagation, ground reflection, and source motion on the impact of en-route aircraft noise. A numerical model has been developed to compute pressure time-histories due to a uniformly moving source above a flat ground surface in the presence of a horizontally stratified atmosphere. For a moving source at high elevations, contributions from a direct and specularly reflected wave are sufficient in predicting the sound field close to the ground. In the absence of wind effects, the predicted sound field from a single overhead flight trajectory can be used to interpolate pressure time histories at all other receiver locations via a simplified ray model for the incoherent sound field. This approach provides an efficient method for generating pressure time histories in a three-dimensional space for noise impact studies. A variety of different noise propagation methods are adapted to a uniformly moving source to evaluate the accuracy and efficiency of their predictions. The techniques include: analytical methods, the Fast Field Program (FFP), and asymptotic analysis methods (e.g., ray tracing and more advanced formulations). Source motion effects are introduced via either a retarded time analysis or a Lorentz transform approach depending on the complexity of the problem. The noise spectrum from a single emission frequency, moving source has broadband characteristics. This is a consequence of the Doppler shift which continuously modifies the perceived frequency of the source as it moves relative to a stationary observer on the ground. Thus, the instantaneous wavefronts must be considered in both the frequency dependent ground impedance model and the atmospheric absorption model. It can be shown that the Doppler factor is invariant along each ray path. This gives rise to a path dependent atmospheric

  10. Propeller aircraft interior noise model utilization study and validation

    NASA Technical Reports Server (NTRS)

    Pope, L. D.

    1984-01-01

    Utilization and validation of a computer program designed for aircraft interior noise prediction is considered. The program, entitled PAIN (an acronym for Propeller Aircraft Interior Noise), permits (in theory) predictions of sound levels inside propeller driven aircraft arising from sidewall transmission. The objective of the work reported was to determine the practicality of making predictions for various airplanes and the extent of the program's capabilities. The ultimate purpose was to discern the quality of predictions for tonal levels inside an aircraft occurring at the propeller blade passage frequency and its harmonics. The effort involved three tasks: (1) program validation through comparisons of predictions with scale-model test results; (2) development of utilization schemes for large (full scale) fuselages; and (3) validation through comparisons of predictions with measurements taken in flight tests on a turboprop aircraft. Findings should enable future users of the program to efficiently undertake and correctly interpret predictions.

  11. Practical ranges of loudness levels of various types of environmental noise, including traffic noise, aircraft noise, and industrial noise.

    PubMed

    Salomons, Erik M; Janssen, Sabine A

    2011-06-01

    In environmental noise control one commonly employs the A-weighted sound level as an approximate measure of the effect of noise on people. A measure that is more closely related to direct human perception of noise is the loudness level. At constant A-weighted sound level, the loudness level of a noise signal varies considerably with the shape of the frequency spectrum of the noise signal. In particular the bandwidth of the spectrum has a large effect on the loudness level, due to the effect of critical bands in the human hearing system. The low-frequency content of the spectrum also has an effect on the loudness level. In this note the relation between loudness level and A-weighted sound level is analyzed for various environmental noise spectra, including spectra of traffic noise, aircraft noise, and industrial noise. From loudness levels calculated for these environmental noise spectra, diagrams are constructed that show the relation between loudness level, A-weighted sound level, and shape of the spectrum. The diagrams show that the upper limits of the loudness level for broadband environmental noise spectra are about 20 to 40 phon higher than the lower limits for narrowband spectra, which correspond to the loudness levels of pure tones. The diagrams are useful for assessing limitations and potential improvements of environmental noise control methods and policy based on A-weighted sound levels.

  12. Practical Ranges of Loudness Levels of Various Types of Environmental Noise, Including Traffic Noise, Aircraft Noise, and Industrial Noise

    PubMed Central

    Salomons, Erik M.; Janssen, Sabine A.

    2011-01-01

    In environmental noise control one commonly employs the A-weighted sound level as an approximate measure of the effect of noise on people. A measure that is more closely related to direct human perception of noise is the loudness level. At constant A-weighted sound level, the loudness level of a noise signal varies considerably with the shape of the frequency spectrum of the noise signal. In particular the bandwidth of the spectrum has a large effect on the loudness level, due to the effect of critical bands in the human hearing system. The low-frequency content of the spectrum also has an effect on the loudness level. In this note the relation between loudness level and A-weighted sound level is analyzed for various environmental noise spectra, including spectra of traffic noise, aircraft noise, and industrial noise. From loudness levels calculated for these environmental noise spectra, diagrams are constructed that show the relation between loudness level, A-weighted sound level, and shape of the spectrum. The diagrams show that the upper limits of the loudness level for broadband environmental noise spectra are about 20 to 40 phon higher than the lower limits for narrowband spectra, which correspond to the loudness levels of pure tones. The diagrams are useful for assessing limitations and potential improvements of environmental noise control methods and policy based on A-weighted sound levels. PMID:21776205

  13. Noise Annoyance Is Associated with Depression and Anxiety in the General Population- The Contribution of Aircraft Noise

    PubMed Central

    Beutel, Manfred E.; Jünger, Claus; Klein, Eva M.; Wild, Philipp; Lackner, Karl; Blettner, Maria; Binder, Harald; Michal, Matthias; Wiltink, Jörg; Brähler, Elmar; Münzel, Thomas

    2016-01-01

    Background While noise annoyance has become recognized as an important environmental stressor, its association to mental health has hardly been studied. We therefore determined the association of noise annoyance to anxiety and depression and explored the contribution of diverse environmental sources to overall noise annoyance. Patients and Methods We investigated cross-sectional data of n = 15.010 participants of the Gutenberg Health Study (GHS), a population-based, prospective, single-center cohort study in Mid-Germany (age 35 to 74 years). Noise annoyance was assessed separately for road traffic, aircraft, railways, industrial, neighborhood indoor and outdoor noise (“during the day”; “in your sleep”) on 5-point scales (“not at all” to “extremely”); depression and anxiety were assessed by the PHQ-9, resp. GAD-2. Results Depression and anxiety increased with the degree of overall noise annoyance. Compared to no annoyance, prevalence ratios for depression, respectively anxiety increased from moderate (PR depression 1.20; 95%CI 1.00 to 1.45; PR anxiety 1.42; 95% CI 1.15 to 1.74) to extreme annoyance (PR depression 1.97; 95%CI 1.62 to 2.39; PR anxiety 2.14; 95% CI 1.71 to 2.67). Compared to other sources, aircraft noise annoyance was prominent affecting almost 60% of the population. Interpretation Strong noise annoyance was associated with a two-fold higher prevalence of depression and anxiety in the general population. While we could not relate annoyance due to aircraft noise directly to depression and anxiety, we established that it was the major source of annoyance in the sample, exceeding the other sources in those strongly annoyed. Prospective follow-up data will address the issue of causal relationships between annoyance and mental health. PMID:27195894

  14. Aircraft noise and speech intelligibility in an outdoor living space.

    PubMed

    Alvarsson, Jesper J; Nordström, Henrik; Lundén, Peter; Nilsson, Mats E

    2014-06-01

    Studies of effects on speech intelligibility from aircraft noise in outdoor places are currently lacking. To explore these effects, first-order ambisonic recordings of aircraft noise were reproduced outdoors in a pergola. The average background level was 47 dB LA eq. Lists of phonetically balanced words (LAS max,word = 54 dB) were reproduced simultaneously with aircraft passage noise (LAS max,noise = 72-84 dB). Twenty individually tested listeners wrote down each presented word while seated in the pergola. The main results were (i) aircraft noise negatively affects speech intelligibility at sound pressure levels that exceed those of the speech sound (signal-to-noise ratio, S/N < 0), and (ii) the simple A-weighted S/N ratio was nearly as good an indicator of speech intelligibility as were two more advanced models, the Speech Intelligibility Index and Glasberg and Moore's [J. Audio Eng. Soc. 53, 906-918 (2005)] partial loudness model. This suggests that any of these indicators is applicable for predicting effects of aircraft noise on speech intelligibility outdoors.

  15. Selected methods for quantification of community exposure to aircraft noise

    NASA Technical Reports Server (NTRS)

    Edge, P. M., Jr.; Cawthorn, J. M.

    1976-01-01

    A review of the state-of-the-art for the quantification of community exposure to aircraft noise is presented. Physical aspects, people response considerations, and practicalities of useful application of scales of measure are included. Historical background up through the current technology is briefly presented. The developments of both single-event and multiple-event scales are covered. Selective choice is made of scales currently in the forefront of interest and recommended methodology is presented for use in computer programing to translate aircraft noise data into predictions of community noise exposure. Brief consideration is given to future programing developments and to supportive research needs.

  16. Re-engining - The sound case for aircraft noise reduction

    NASA Astrophysics Data System (ADS)

    Goddard, K.

    1991-06-01

    The paper reviews the history of legislation to reduce jet-powered aircraft noise, particularly in the U.S.A. Recently introduced legislation is discussed and the paper goes on to explain the fundamental advantage of re-engining as a means of reducing aircraft noise. Th Rolls-Royce Tay engine is introduced and the two re-engine programs already launched are described. The expected large reductions in noise level which result from re-engining are illustrated. The paper concludes with a discussion on new programs, on the current airline business scene and on some aspects of the economics of re-engining.

  17. Community reaction to aircraft noise around smaller city airports

    NASA Technical Reports Server (NTRS)

    Connor, W. K.; Patterson, H. P.

    1972-01-01

    The results are presented of a study of community reaction to jet aircraft noise in the vicinity of airports in Chattanooga, Tennessee, and Reno, Nevada. These cities were surveyed in order to obtain data for comparison with that obtained in larger cities during a previous study. (The cities studied earlier were Boston, Chicago, Dallas, Denver, Los Angeles, Miami, and New York.) The purpose of the present effort was to observe the relative reaction under conditions of lower noise exposure and in less highly urbanized areas, and to test the previously developed predictive equation for annoyance under such circumstances. In Chattanooga and Reno a total of 1960 personal interviews based upon questionnaires were obtained. Aircraft noise measurements were made concurrently and aircraft operations logs were maintained for several weeks in each city to permit computation of noise exposures. The survey respondents were chosen randomly from various exposure zones.

  18. The cost of noise reduction in commercial tilt rotor aircraft

    NASA Technical Reports Server (NTRS)

    Faulkner, H. B.

    1974-01-01

    The relationship between direct operating cost (DOC) and departure noise annoyance was developed for commercial tilt rotor aircraft. This was accomplished by generating a series of tilt rotor aircraft designs to meet various noise goals at minimum DOC. These vehicles were spaced across the spectrum of possible noise levels from completely unconstrained to the quietest vehicle that could be designed within the study ground rules. A group of optimization parameters were varied to find the minimum DOC while other inputs were held constant and some external constraints were met. This basic variation was then extended to different aircraft sizes and technology time frames. It was concluded that reducing noise annoyance by designing for lower rotor tip speeds is a very promising avenue for future research and development. It appears that the cost of halving the annoyance compared to an unconstrained design is insignificant and the cost of halving the annoyance again is small.

  19. Diagnostics and Active Control of Aircraft Interior Noise

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.

    1998-01-01

    This project deals with developing advanced methods for investigating and controlling interior noise in aircraft. The work concentrates on developing and applying the techniques of Near Field Acoustic Holography (NAH) and Principal Component Analysis (PCA) to the aircraft interior noise dynamic problem. This involves investigating the current state of the art, developing new techniques and then applying them to the particular problem being studied. The knowledge gained under the first part of the project was then used to develop and apply new, advanced noise control techniques for reducing interior noise. A new fully active control approach based on the PCA was developed and implemented on a test cylinder. Finally an active-passive approach based on tunable vibration absorbers was to be developed and analytically applied to a range of test structures from simple plates to aircraft fuselages.

  20. Propeller aircraft noise legislation—A comprehensive review

    NASA Astrophysics Data System (ADS)

    Heller, Hanno H.

    After a brief historical review of the development of propeller aircraft noise certification by the International Civil Aviation Organization (ICAO), this paper describes in detail the pertinent ICAO-document-the ‘ANNEX 16’-which contains ‘Standards and Recommended Practices’ for the noise certification of propeller-driven aeorplanes either above, or not exceeding, a certificated take-off mass of 5700 kg. Direct experience in the ‘day to day’ practice of conducting aircraft flyover noise measurements for purposes of noise certification is revealed, potential pit-falls, ‘loop-holes’, and present uncertainties in the various procedures are described, and the efforts of the ICAO-Committee on Aircraft Noise (CAN), and its successor organization, the ICAO-Committee on Aviation Environmental Protection (CAEP) to resolve ensuing problems, are given extensive space. The continuing development, as well as the frequently necessary consolidations, of noise certification methods and procedures requires substantial research effort, both in terms of actual dedicated flight testing and wind tunnel testing. This work is dealt with in fair detail and where necessary explained with illustrations, often directly out of research reports. This should give the reader an impression of the enormous complexity of noise certificating propeller aircraft, which after all entails not only legislative aspects, but also basic and applied aerocoustic research. However, in addition to discussing the current state of propeller-aeroplane noise certification, there are sections which go back in time to elaborate on the thoughts and the sometimes dead-end streets which were penetrated in the numerous attempts to improve noise certification. Other sections still look into the future to present changes in propeller aircraft noise legislation that are expected to be agreed upon either in the near- or medium-term.

  1. Design of the Next Generation Aircraft Noise Prediction Program: ANOPP2

    NASA Technical Reports Server (NTRS)

    Lopes, Leonard V., Dr.; Burley, Casey L.

    2011-01-01

    The requirements, constraints, and design of NASA's next generation Aircraft NOise Prediction Program (ANOPP2) are introduced. Similar to its predecessor (ANOPP), ANOPP2 provides the U.S. Government with an independent aircraft system noise prediction capability that can be used as a stand-alone program or within larger trade studies that include performance, emissions, and fuel burn. The ANOPP2 framework is designed to facilitate the combination of acoustic approaches of varying fidelity for the analysis of noise from conventional and unconventional aircraft. ANOPP2 integrates noise prediction and propagation methods, including those found in ANOPP, into a unified system that is compatible for use within general aircraft analysis software. The design of the system is described in terms of its functionality and capability to perform predictions accounting for distributed sources, installation effects, and propagation through a non-uniform atmosphere including refraction and the influence of terrain. The philosophy of mixed fidelity noise prediction through the use of nested Ffowcs Williams and Hawkings surfaces is presented and specific issues associated with its implementation are identified. Demonstrations for a conventional twin-aisle and an unconventional hybrid wing body aircraft configuration are presented to show the feasibility and capabilities of the system. Isolated model-scale jet noise predictions are also presented using high-fidelity and reduced order models, further demonstrating ANOPP2's ability to provide predictions for model-scale test configurations.

  2. Noise Hazard Evaluation Sound Level Data on Noise Sources

    DTIC Science & Technology

    1975-01-01

    AD-A021 465 NOISE HAZARD EfALUATION SOUND LEVEL DATA ON NOISE SOURCES Jeffrey Goldstein Army Environmental Hygiene Agency Prepared for: Army Health ...A. Noise Hazard Evaluation. B. Engineering Noise Control. C. Health Education. D. Audiometry. E. Hearing Protection. This technical guide concerns the...SOUND LEVEL DATA OF NOISE SOURCES Approved for public release, distribution unlimited. jGI4A C4C SENTINEL HEALTH I 5 US ARMY ENVIROIN.MENTAL HYGIENE

  3. Aircraft noise effects: An inter-disciplinary study of the effect of aircraft noise on man. Part 3: Supplementary analyses of the social-scientific portion of the study on aircraft noise conducted by the DFG

    NASA Technical Reports Server (NTRS)

    Schumer, R.

    1980-01-01

    Variables in a study of noise perception near the Munich-Reims airport are explained. The interactive effect of the stimulus (aircraft noise) and moderator (noise sensitivity) on the aircraft noise reaction (disturbance or annoyance) is considered. Methods employed to demonstrate that the moderator has a differencing effect on various stimulus levels are described. Results of the social-scientific portion of the aircraft noise project are compared with those of other survey studies on the problem of aircraft noise. Procedures for contrast group analysis and multiple classification analysis are examined with focus on some difficulties in their application.

  4. Towards Full Aircraft Airframe Noise Prediction: Detached Eddy Simulations

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Mineck, Raymond E.

    2014-01-01

    Results from a computational study on the aeroacoustic characteristics of an 18%-scale, semi-span Gulf-stream aircraft model are presented in this paper. NASA's FUN3D unstructured compressible Navier-Stokes solver was used to perform steady and unsteady simulations of the flow field associated with this high-fidelity aircraft model. Solutions were obtained for free-air at a Mach number of 0.2 with the flap deflected at 39 deg, with the main gear off and on (the two baseline configurations). Initially, the study focused on accurately predicting the prominent noise sources at both flap tips for the baseline configuration with deployed flap only. Building upon the experience gained from this initial effort, subsequent work involved the full landing configuration with both flap and main landing gear deployed. For the unsteady computations, we capitalized on the Detached Eddy Simulation capability of FUN3D to capture the complex time-dependent flow features associated with the flap and main gear. To resolve the noise sources over a broad frequency range, the tailored grid was very dense near the flap inboard and outboard tips and the region surrounding the gear. Extensive comparison of the computed steady and unsteady surface pressures with wind tunnel measurements showed good agreement for the global aerodynamic characteristics and the local flow field at the flap inboard tip. However, the computed pressure coefficients indicated that a zone of separated flow that forms in the vicinity of the outboard tip is larger in extent along the flap span and chord than measurements suggest. Computed farfield acoustic characteristics from a FW-H integral approach that used the simulated pressures on the model solid surface were in excellent agreement with corresponding measurements.

  5. Aircraft noise prediction program theoretical manual: Rotorcraft System Noise Prediction System (ROTONET), part 4

    NASA Technical Reports Server (NTRS)

    Weir, Donald S.; Jumper, Stephen J.; Burley, Casey L.; Golub, Robert A.

    1995-01-01

    This document describes the theoretical methods used in the rotorcraft noise prediction system (ROTONET), which is a part of the NASA Aircraft Noise Prediction Program (ANOPP). The ANOPP code consists of an executive, database manager, and prediction modules for jet engine, propeller, and rotor noise. The ROTONET subsystem contains modules for the prediction of rotor airloads and performance with momentum theory and prescribed wake aerodynamics, rotor tone noise with compact chordwise and full-surface solutions to the Ffowcs-Williams-Hawkings equations, semiempirical airfoil broadband noise, and turbulence ingestion broadband noise. Flight dynamics, atmosphere propagation, and noise metric calculations are covered in NASA TM-83199, Parts 1, 2, and 3.

  6. NASA Auralization Tool Reveals Aircraft Noise Differences

    NASA Video Gallery

    How can we *know* that a future aircraft will be less noisy than the ones we fly in today? NASA builds computer-based tools to predict those things, with certainty. This video is an "auralization" ...

  7. Use of Airport Noise Complaint Files to Improve Understanding of Community Response to Aircraft Noise

    NASA Technical Reports Server (NTRS)

    Fidell, Sanford; Howe, Richard

    1998-01-01

    This study assessed the feasibility of using complaint information archived by modem airport monitoring systems to conduct quantitative analyses of the causes of aircraft noise complaints and their relationship to noise- induced annoyance. It was found that all computer-based airport monitoring systems provide at least rudimentary tools for performing data base searches by complainant name, address, date, time of day, and types of aircraft and complaints. Analyses of such information can provide useful information about longstanding concerns, such as the extent to which complaint rates are driven by objectively measurable aspects of aircraft operations; the degree to which changes in complaint rates can be predicted prior to implementation of noise mitigation measures; and the degree to which aircraft complaint information can be used to simplify and otherwise improve prediction of the prevalence of noise-induced annoyance in communities.

  8. Aircraft noise and incidence of hypertension--gender specific effects.

    PubMed

    Eriksson, Charlotta; Bluhm, Gösta; Hilding, Agneta; Ostenson, Claes-Göran; Pershagen, Göran

    2010-11-01

    Recent studies show associations between aircraft noise and cardiovascular outcomes such as hypertension. However, these studies were mostly cross-sectional and there are uncertainties regarding potential gender differences as well as sensitive subgroups. In this study, we investigated the cumulative incidence of hypertension in relation to aircraft noise exposure among Swedish men and women living in Stockholm County. A total of 4721 subjects, aged 35-56 at baseline, were followed for 8-10 years. The population was selected according to family history of diabetes, which was present for half of the subjects. The exposure assessment was performed by geographical information systems and based on residential history during the period of follow-up. Blood pressure was measured at baseline and at the end of follow-up. Additional information regarding diagnosis and treatment of hypertension as well as various lifestyle factors was provided by questionnaires. In the overall population, no increased risk for hypertension was found among subjects exposed to aircraft noise ≥ 50 dB(A) L(den); relative risk (RR) 1.02 (95% CI 0.90-1.15). When restricting the cohort to those not using tobacco at the blood pressure measurements, a significant risk increase per 5 dB(A) of aircraft noise exposure was found in men; RR 1.21 (1.05-1.39), but not in women; RR 0.97 (0.83-1.13). In both sexes combined, an increased risk of hypertension related to aircraft noise exposure was indicated primarily among those reporting annoyance to aircraft noise; RR 1.42 (1.11-1.82). No consistent effect modification was detected for any of the cardiovascular risk factors under investigation although a family history of diabetes appeared to modify the risk in women. In conclusion, the results suggest an increased risk of hypertension following long-term aircraft noise exposure in men, and that subjects annoyed by aircraft noise may be particularly sensitive to noise related hypertension.

  9. Study of noise transmission through double wall aircraft windows

    NASA Technical Reports Server (NTRS)

    Vaicaitis, R.

    1983-01-01

    Analytical and experimental procedures were used to predict the noise transmitted through double wall windows into the cabin of a twin-engine G/A aircraft. The analytical model was applied to optimize cabin noise through parametric variation of the structural and acoustic parameters. The parametric study includes mass addition, increase in plexiglass thickness, decrease in window size, increase in window cavity depth, depressurization of the space between the two window plates, replacement of the air cavity with a transparent viscoelastic material, change in stiffness of the plexiglass material, and different absorptive materials for the interior walls of the cabin. It was found that increasing the exterior plexiglass thickness and/or decreasing the total window size could achieve the proper amount of noise reduction for this aircraft. The total added weight to the aircraft is then about 25 lbs.

  10. Sound transmission through ducts and aircraft noise prediction, volume 1

    NASA Astrophysics Data System (ADS)

    Schauer, J. J.; Datko, J. T.; Guyton, R. W.

    1982-01-01

    Aircraft engine acoustical lining impedance models, ray acoustics, hydrodynamic modes, and transient analysis of sound propagation in variable area duct studies were applied to aircraft noise prediction. The effects of several duct lining configurations in a TF33 P5 and a CFM56 engined KC-135B aircraft were predicted. The prediction was based on a model corrected to fit flight noise data and modified by including theoretical duct noise attenuation predictions. The transient solution of variable area ducts permitted the prediction of sound propgation in bullet nose inlets for no low and was moderately successful when a potential flow was included with low Mach numbers. Volume 1 contains the technical report and analysis. Volume 2 contains the user's manuals and listings of the computer codes developed.

  11. Effectiveness of combined aircraft engine noise suppressors

    NASA Astrophysics Data System (ADS)

    Khaletskiy, Yu. D.

    2012-07-01

    We consider the design features of fan noise suppressors in application to air intakes and the bypass duct of a turbofan engine. A combined liner is developed that has increased acoustic efficiency in comparison to conventional honeycomb liner. We demonstrate the important role of the area of the sound-absorbing liner between fan Rotor and Stator ensuring significant noise reduction.

  12. Evaluating and minimizing noise impact due to aircraft flyover

    NASA Technical Reports Server (NTRS)

    Jacobson, I. D.; Cook, G.

    1979-01-01

    Existing techniques were used to assess the noise impact on a community due to aircraft operation and to optimize the flight paths of an approaching aircraft with respect to the annoyance produced. Major achievements are: (1) the development of a population model suitable for determining the noise impact, (2) generation of a numerical computer code which uses this population model along with the steepest descent algorithm to optimize approach/landing trajectories, (3) implementation of this optimization code in several fictitious cases as well as for the community surrounding Patrick Henry International Airport, Virginia.

  13. The effect of interior aircraft noise on pilot performance.

    PubMed

    Lindvall, Johan; Västfjall, Daniel

    2013-04-01

    This study examined the effect of the interior sounds of an aircraft cockpit on ratings of affect and expected performance decrement. While exposed to 12 interior aircraft sounds, of which half were modified to correspond to what is experienced with an active noise reduction (ANR) headset, 23 participants rated their affective reactions and how they believed their performance on various tasks would be affected. The results suggest that implementation of ANR-technique has a positive effect on ratings of expected performance. In addition, affective reactions to the noise are related to ratings of expected performance. The implications of these findings for both research and pilot performance are discussed.

  14. Aircraft noise synthesis system: Version 4 user instructions

    NASA Technical Reports Server (NTRS)

    Mccurdy, David A.; Sullivan, Brenda M.; Grandle, Robert E.

    1987-01-01

    A modified version of the Aircraft Noise Synthesis System with improved directivity and tonal content modeling has been developed. The synthesis system is used to provide test stimuli for studies of community annoyance to aircraft flyover noise. The computer-based system generates realistic, time-varying audio simulations of aircraft flyover noise at a specified observer location on the ground. The synthesis takes into account the time-varying aircraft position relative to the observer; specified reference spectra consisting of broadband, narrowband, and pure tone components; directivity patterns; Doppler shift; atmospheric effects; and ground effects. These parameters can be specified and controlled in such a way as to generate stimuli in which certain noise characteristics such as duration or tonal content are independently varied while the remaining characteristics such as broadband content are held constant. The modified version of the system provides improved modeling of noise directivity patterns and an increased number of pure tone components. User instructions for the modified version of the synthesis system are provided.

  15. Combat aircraft jet engine noise studies

    NASA Astrophysics Data System (ADS)

    Lewy, S.; Fournier, G.; Pianko, M.

    Methods of noise prediction and attenuation, based on results obtained in civil applications are presented. Input data for directivity and radiation forecasts are given by measurements of vane and blade pressure fluctuations, and by modal analysis of the spinning waves propagating in the inlet duct. Attention is given to sound generation mechanisms for subsonic and supersonic single jets and bypass jets. Prediction methods, based on Lighthill's equation (tensor due to the turbulence), are discussed, and the various means of jet noise reduction are reviewed. The CEPRA 19 anechoic wind tunnel, which is primarily designed for studying the jet noise radiated in the far field with flight effects is described.

  16. Noise of High Performance Aircraft at Afterburner

    DTIC Science & Technology

    2016-05-04

    shows a plot of the autocorrelation function computed using noise data measured by the same microphone at 80N2 power. This function has two distinct...better idea of the intrinsic noise, an enlarged plot of figure 3 is provided in figure 4. The intrinsic noise appears to be quasi-periodic with an...Comparison of narrow band and 1/3 octave band spectra. 1410 at MaxAB power. 4. Spectra with frequency plotted in a linear scale All the

  17. Aircraft Noise Definition. Individual Aircraft Technical Data-Model 707

    DTIC Science & Technology

    1973-12-01

    Department of Tranportation in the interest of information exchange. The United States Government assumes no liability for Its contents or we threof...Performance Computer Program". !4 - I;I ;I § I! |I’ i I ~~~I PAG& .....¶ - 2.0 SUMMARY The purpose of this document is to provide the necessary information...bleeds off. The "Intermediate Stage Boeing Proprietary Computer • Program" operates on the certified parameters for each of the above aircraft/engine

  18. Future developments in transport aircraft noise reduction technology

    SciTech Connect

    Pendley, R.E.

    1982-01-01

    During the past 13 years, important advances in the technology of aircraft noise control have resulted from industry and government research programs. Quieter commercial transport airplanes have entered the fleet and additional new designs now committed to production will begin service in a few years. This paper indicates the noise reductions that will be achieved by the quieter transports that will replace the older designs and remarks on the outlook for still quieter designs.

  19. Perceived Noise Analysis for Offset Jets Applied to Commercial Supersonic Aircraft

    NASA Technical Reports Server (NTRS)

    Huff, Dennis L.; Henderson, Brenda S.; Berton, Jeffrey J.; Seidel, Jonathan A.

    2016-01-01

    A systems analysis was performed with experimental jet noise data, engine/aircraft performance codes and aircraft noise prediction codes to assess takeoff noise levels and mission range for conceptual supersonic commercial aircraft. A parametric study was done to identify viable engine cycles that meet NASAs N+2 goals for noise and performance. Model scale data from offset jets was used as input to the aircraft noise prediction code to determine the expected sound levels for the lateral certification point where jet noise dominates over all other noise sources. The noise predictions were used to determine the optimal orientation of the offset nozzles to minimize the noise at the lateral microphone location. An alternative takeoff procedure called programmed lapse rate was evaluated for noise reduction benefits. Results show there are two types of engines that provide acceptable range performance; one is a standard mixed-flow turbofan with a single-stage fan, and the other is a three-stream variable-cycle engine with a multi-stage fan. The engine with a single-stage fan has a lower specific thrust and is 8 to 10 EPNdB quieter for takeoff. Offset nozzles reduce the noise directed toward the thicker side of the outer flow stream, but have less benefit as the core nozzle pressure ratio is reduced and the bypass-to-core area ratio increases. At the systems level for a three-engine N+2 aircraft with full throttle takeoff, there is a 1.4 EPNdB margin to Chapter 3 noise regulations predicted for the lateral certification point (assuming jet noise dominates). With a 10 reduction in thrust just after takeoff rotation, the margin increases to 5.5 EPNdB. Margins to Chapter 4 and Chapter 14 levels will depend on the cumulative split between the three certification points, but it appears that low specific thrust engines with a 10 reduction in thrust (programmed lapse rate) can come close to meeting Chapter 14 noise levels. Further noise reduction is possible with additional

  20. Quelling Cabin Noise in Turboprop Aircraft via Active Control

    NASA Technical Reports Server (NTRS)

    Kincaid, Rex K.; Laba, Keith E.; Padula, Sharon L.

    1997-01-01

    Cabin noise in turboprop aircraft causes passenger discomfort, airframe fatigue, and employee scheduling constraints due to OSHA standards for exposure to high levels of noise. The noise levels in the cabins of turboprop aircraft are typically 10 to 30 decibels louder than commercial jet noise levels. However. unlike jet noise the turboprop noise spectrum is dominated by a few low frequency tones. Active structural acoustic control is a method in which the control inputs (used to reduce interior noise) are applied directly to a vibrating structural acoustic system. The control concept modeled in this work is the application of in-plane force inputs to piezoceramic patches bonded to the wall of a vibrating cylinder. The goal is to determine the force inputs and locations for the piezoceramic actuators so that: (1) the interior noise is effectively damped; (2) the level of vibration of the cylinder shell is not increased; and (3) the power requirements needed to drive the actuators are not excessive. Computational experiments for data taken from a computer generated model and from a laboratory test article at NASA Langley Research Center are provided.

  1. Physical and subjective studies of aircraft interior noise and vibration

    NASA Technical Reports Server (NTRS)

    Stephens, D. G.; Leatherwood, J. D.

    1979-01-01

    Measurements to define and quantify the interior noise and vibration stimuli of aircraft are reviewed as well as field and simulation studies to determine the subjective response to such stimuli, and theoretical and experimental studies to predict and control the interior environment. In addition, ride quality criteria/standards for noise, vibration, and combinations of these stimuli are discussed in relation to the helicopter cabin environment. Data on passenger response are presented to illustrate the effects of interior noise and vibration on speech intelligibility and comfort of crew and passengers. The interactive effects of noise with multifrequency and multiaxis vibration are illustrated by data from LaRC ride quality simulator. Constant comfort contours for various combinations of noise and vibration are presented and the incorporation of these results into a user-oriented model are discussed. With respect to aircraft interior noise and vibration control, ongoing studies to define the near-field noise, the transmission of noise through the structure, and the effectiveness of control treatments are described.

  2. Jet Noise Source Localization Using Linear Phased Array

    NASA Technical Reports Server (NTRS)

    Agboola, Ferni A.; Bridges, James

    2004-01-01

    A study was conducted to further clarify the interpretation and application of linear phased array microphone results, for localizing aeroacoustics sources in aircraft exhaust jet. Two model engine nozzles were tested at varying power cycles with the array setup parallel to the jet axis. The array position was varied as well to determine best location for the array. The results showed that it is possible to resolve jet noise sources with bypass and other components separation. The results also showed that a focused near field image provides more realistic noise source localization at low to mid frequencies.

  3. The effect of the duration of jet aircraft flyover sounds on judged annoyance. [noise predictions and noise measurements of jet aircrafts and human reactions to the noise intensity

    NASA Technical Reports Server (NTRS)

    Shepherd, K. P.

    1979-01-01

    The effect of the duration of jet aircraft flyover sounds on humans and the annoyance factor are examined. A nine point numerical category scaling technique is utilized for the study. Changes in the spectral characteristics of aircraft sounds caused by atmospheric attenuation are discussed. The effect of Doppler shifts using aircraft noises with minimal pure tone content is reported. The spectral content of sounds independent of duration and Doppler shift are examined by analysis of variance.

  4. Should helicopter noise be measured differently from other aircraft noise? A review of the psychoacoustic literature

    NASA Technical Reports Server (NTRS)

    Molino, J. A.

    1982-01-01

    A review of 34 studies indicates that several factors or variables might be important in providing a psychoacoustic foundation for measurements of the noise from helicopters. These factors are phase relations, tail rotor noise, repetition rate, crest level, and generic differences between conventional aircraft and helicopters. Particular attention was given to the impulsive noise known as blade slap. Analysis of the evidence for and against each factor reveals that, for the present state of scientific knowledge, none of these factors should be regarded as the basis for a significant noise measurement correction due to impulsive blade slap. The current method of measuring effective perceived noise level for conventional aircraft appears to be adequate for measuring helicopter noise as well.

  5. Simulation-Based Airframe Noise Prediction of a Full-Scale, Full Aircraft

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Fares, Ehab

    2016-01-01

    A previously validated computational approach applied to an 18%-scale, semi-span Gulfstream aircraft model was extended to the full-scale, full-span aircraft in the present investigation. The full-scale flap and main landing gear geometries used in the simulations are nearly identical to those flown on the actual aircraft. The lattice Boltzmann solver PowerFLOW® was used to perform time-accurate predictions of the flow field associated with this aircraft. The simulations were performed at a Mach number of 0.2 with the flap deflected 39 deg. and main landing gear deployed (landing configuration). Special attention was paid to the accurate prediction of major sources of flap tip and main landing gear noise. Computed farfield noise spectra for three selected baseline configurations (flap deflected 39 deg. with and without main gear extended, and flap deflected 0 deg. with gear deployed) are presented. The flap brackets are shown to be important contributors to the farfield noise spectra in the mid- to high-frequency range. Simulated farfield noise spectra for the baseline configurations, obtained using a Ffowcs Williams and Hawkings acoustic analogy approach, were found to be in close agreement with acoustic measurements acquired during the 2006 NASA-Gulfstream joint flight test of the same aircraft.

  6. NASTRAN application for the prediction of aircraft interior noise

    NASA Technical Reports Server (NTRS)

    Marulo, Francesco; Beyer, Todd B.

    1987-01-01

    The application of a structural-acoustic analogy within the NASTRAN finite element program for the prediction of aircraft interior noise is presented. Some refinements of the method, which reduce the amount of computation required for large, complex structures, are discussed. Also, further improvements are proposed and preliminary comparisons with structural and acoustic modal data obtained for a large, composite cylinder are presented.

  7. An Analysis of USAF Aircraft Noise and Hedonic Property Values

    DTIC Science & Technology

    2006-03-01

    the hedonic pricing method of non-market valuation. The results of this research show that current methods of noise mitigation may not be...25 Hedonic Pricing Method...is with a hedonic pricing method of non-market valuation of housing values. This research seeks to determine the effect that USAF aircraft and

  8. QCGAT aircraft/engine design for reduced noise and emissions

    NASA Technical Reports Server (NTRS)

    Lanson, L.; Terrill, K. M.

    1980-01-01

    The high bypass ratio QCGAT engine played an important role in shaping the aircraft design. The aircraft which evolved is a sleek, advanced design, six-place aircraft with 3538 kg (7,800 lb) maximum gross weight. It offers a 2778 kilometer (1500 nautical mile) range with cruise speed of 0.5 Mach number and will take-off and land on the vast majority of general aviation airfields. Advanced features include broad application of composite materials and a supercritical wing design with winglets. Full-span fowler flaps were introduced to improve landing capability. Engines are fuselage-mounted with inlets over the wing to provide shielding of fan noise by the wing surfaces. The design objectives, noise, and emission considerations, engine cycle and engine description are discussed as well as specific design features.

  9. Application of FEM/SEA for prediction of aircraft cockpit noise

    NASA Astrophysics Data System (ADS)

    Engelstad, S. P.

    Interior noise restrictions in commercial and military aircraft has led to the need for accurate noise transmission prediction capabilities. Predictions are needed in the later aircraft design stages, so that the structural and acoustic changes and/or active control methods can be optimized with a minimal impact on weight and other considerations. The objective of the proposed paper is to investigate the use of the finite element method (FEM) and statistical energy analysis (SEA) method for the prediction of interior noise in an aircraft cockpit. For the cockpit configuration under study, the internal noise is dominated by low-frequency discrete resonant peaks (less than 500 Hz). After examining the available flight test cockpit internal noise data in conjunction with the canopy vibration data, it was concluded that the principal noise source is due to the external turbulent flow exciting the canopy and radiating into the cockpit. Thus the study focused on the resonant noise transmission of the canopy into the small enclosed cockpit air space. The frequency range of primary interest is well below the critical frequency range.

  10. Modal analysis of an aircraft engine fan noise

    NASA Astrophysics Data System (ADS)

    Gorodkova, Natalia; Chursin, Valeriy; Bersenev, Yuliy; Burdakov, Ruslan; Siner, Aleksandr; Viskova, Tatiana

    2016-10-01

    The fan is one of the main noise sources of an aircraft engine. To reduce fan noise and provide liner optimization in the inlet it is necessary to research modal structure of the fan noise. The present paper contains results of acoustic tests on installation for mode generation that consists of 34-channel generator and the inlet updated for mounting of 100 microphones, the experiments were provided in new anechoic chamber of Perm National Research Polytechnic University, the engine with the same inlet was also tested in the open test bench conditions, and results of the fan noise modal structure are presented. For modal structure educting, all 100 channels were synchronously registered in a given frequency range. The measured data were analyzed with PULSE analyzer using fast Fourier transform with a frequency resolution 8..16 Hz. Single modes with numbers from 0 to 35 at frequencies 500; 630; 800; 1000; 1250; 1600 Hz and different combinations of modes at frequencies 1000, 1600, 2000, 2500 Hz were set during tests. Modes with small enough numbers are generated well on the laboratory installation, high-number modes generate additional modes caused by a complicated interference pattern of sound field in the inlet. Open test bench results showed that there are also a lot of harmonic components at frequencies lower than fan BPF. Under 0.65 of cut off there is only one distinct mode, other modes with close and less numbers appear from 0.7 of cut off and above. At power regimes 0.76 and 0.94 of cut off the highest mode also changes from positive to negative mode number area. Numbers of the highest modes change smoothly enough with the growth of power regime. At power regimes with Mach>1 (0.7 of cut off and above) on circumference of blade wheel there is a well-defined noise of shock waves at rotor frequency harmonics that appears at the range between the first rotor frequency and fan blade passing frequency (BPF). It is planned to continue researching of sound field

  11. An assessment of propeller aircraft noise reduction technology

    NASA Technical Reports Server (NTRS)

    Metzger, F. Bruce

    1995-01-01

    This report is a review of the literature regarding propeller airplane far-field noise reduction. Near-field and cabin noise reduction are not specifically addressed. However, some of the approaches used to reduce far-field noise produce beneficial effects in the near-field and in the cabin. The emphasis is on propeller noise reduction but engine exhaust noise reduction by muffling is also addressed since the engine noise becomes a significant part of the aircraft noise signature when propeller noise is reduced. It is concluded that there is a substantial body of information available that can be used as the basis to reduce propeller airplane noise. The reason that this information is not often used in airplane design is the associated weight, cost, and performance penalties. It is recommended that the highest priority be given to research for reducing the penalties associated with lower operating RPM and propeller diameter while increasing the number of blades. Research to reduce engine noise and explore innovative propeller concepts is also recommended.

  12. Aircraft noise effects: An interdisciplinary study of the effect of aircraft noise on man. Part 2: Appendix

    NASA Technical Reports Server (NTRS)

    1980-01-01

    A survey used to obtain data of a sociological nature regarding subjects used in a study of aircraft noise perception and tolerance near the Munich-Reims airport is presented. Statistics compiled on occupational, physiological, and medical aspects of the subjects are tabulated.

  13. Near-field acoustical holography of military jet aircraft noise

    NASA Astrophysics Data System (ADS)

    Wall, Alan T.; Gee, Kent L.; Neilsen, Tracianne; Krueger, David W.; Sommerfeldt, Scott D.; James, Michael M.

    2010-10-01

    Noise radiated from high-performance military jet aircraft poses a hearing-loss risk to personnel. Accurate characterization of jet noise can assist in noise prediction and noise reduction techniques. In this work, sound pressure measurements were made in the near field of an F-22 Raptor. With more than 6000 measurement points, this is the most extensive near-field measurement of a high-performance jet to date. A technique called near-field acoustical holography has been used to propagate the complex pressure from a two- dimensional plane to a three-dimensional region in the jet vicinity. Results will be shown and what they reveal about jet noise characteristics will be discussed.

  14. Review of recent research of interior noise of propeller aircraft

    NASA Technical Reports Server (NTRS)

    Mixson, J. S.; Powell, C. A.

    1984-01-01

    Publications on the topics of propeller source noise, airborne noise transmission, and passenger comfort response to noise and vibration are reviewed. Of the 187 publications referenced, 140 have appeared since 1978. Examples of research accomplishments are presented to illustrate the state of the art. Emphasis is on comparisons of theoretical and measured results, but the description of the theories is left to the references. This review shows that substantial progress has been made in understanding the characteristics of propeller noise, airborne noise, and passenger response, and in the development of prediction methods. Application of the technology to cabin noise control and possible future research directions are discussed.

  15. Noise of High Performance Aircraft at Afterburner

    DTIC Science & Technology

    2016-02-10

    any major differences between the dominant noise components of these jets and those of a standard high temperature laboratory supersonic jet. It is... temperature . In the literature, these characteristic spectra are referred to as similarity spectra. In the present project, these two similarity spectra...and a spectrum of temperature fluctuations together with a characteristic size of the blobs. Development of such a stochastic numerical boundary

  16. Effects of aircraft noise on the equilibrium of airport residents: Testing and utilization of a new methodology

    NASA Technical Reports Server (NTRS)

    Francois, J.

    1981-01-01

    The focus of the investigation is centered around two main themes: an analysis of the effects of aircraft noise on the psychological and physiological equilibrium of airport residents; and an analysis of the sources of variability of sensitivity to noise. The methodology used is presented. Nine statistical tables are included, along with a set of conclusions.

  17. Twin jet shielding. [for aircraft noise reduction

    NASA Technical Reports Server (NTRS)

    Parthasarathy, S. P.; Cuffel, R. F.; Massier, P. F.

    1979-01-01

    For an over-the-wing/under-the-wing engine configuration on an airplane, the noise produced by the upper jet flow is partially reflected by the lower jet. An analysis has been performed which can be used to predict the distribution of perceived noise levels along the ground plane at take-off for an airplane which is designed to take advantage of the over/under shielding concept. Typical contours of PNL, the shielding benefit in the shadow zone, and the EPNL values at 3.5 nautical miles from brake release as well as EPNL values at sideline at 0.35 nautical miles have been calculated. This has been done for a range of flow parameters characteristic of engines producing inverted velocity profile jets suitable for use in a supersonic cruise vehicle. Reductions up to 6.0 EPNdB in community noise levels can be realized when the over engines are operated at higher thrust and the lower engines simultaneously operated with reduced thrust keeping the total thrust constant.

  18. Transport jet aircraft noise abatement in foreign countries: Growth, structure, impact. Volume 2: Pacific basin, August 1980

    NASA Technical Reports Server (NTRS)

    Spencer, F. A.

    1980-01-01

    Noise control measures at the international airports of Hawaii, New Zealand, Australia, Hong Kong, Japan, and Singapore were studied. Factors in noise control, such as government structure are examined. The increasing power of environmental agencies vis-a-vis aviation departments is noted. The following methods of dealing with aircraft noise are examined by type of control: noise at the source control; noise emmission controls, zoning, building codes, subsidies for relocation, insulation, loss in property values, and for TV, radio and telephone interference; and noise-related landing charges.

  19. Validation of Aircraft Noise Models at Lower Levels of Exposure

    NASA Technical Reports Server (NTRS)

    Page, Juliet A.; Plotkin, Kenneth J.; Carey, Jeffrey N.; Bradley, Kevin A.

    1996-01-01

    Noise levels around airports and airbases in the United States arc computed via the FAA's Integrated Noise Model (INM) or the Air Force's NOISEMAP (NMAP) program. These models were originally developed for use in the vicinity of airports, at distances which encompass a day night average sound level in decibels (Ldn) of 65 dB or higher. There is increasing interest in aircraft noise at larger distances from the airport. including en-route noise. To evaluate the applicability of INM and NMAP at larger distances, a measurement program was conducted at a major air carrier airport with monitoring sites located in areas exposed to an Ldn of 55 dB and higher. Automated Radar Terminal System (ARTS) radar tracking data were obtained to provide actual flight parameters and positive identification of aircraft. Flight operations were grouped according to aircraft type. stage length, straight versus curved flight tracks, and arrival versus departure. Sound exposure levels (SEL) were computed at monitoring locations, using the INM, and compared with measured values. While individual overflight SEL data was characterized by a high variance, analysis performed on an energy-averaging basis indicates that INM and similar models can be applied to regions exposed to an Ldn of 55 dB with no loss of reliability.

  20. Active noise control using noise source having adaptive resonant frequency tuning through stiffness variation

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by a plurality of force transmitting mechanisms which contact the noise radiating element. Each one of the force transmitting mechanisms includes an expandable element and a spring in contact with the noise radiating element so that excitation of the element varies the spring force applied to the noise radiating element. The elements are actuated by a controller which receives input of a signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the elements and causes the spring force applied to the noise radiating element to be varied. The force transmitting mechanisms can be arranged to either produce bending or linear stiffness variations in the noise radiating element.

  1. Aircraft wing trailing-edge noise

    NASA Technical Reports Server (NTRS)

    Underwood, R. L.; Hodgson, T. H.

    1981-01-01

    The mechanism and sound pressure level of the trailing-edge noise for two-dimensional turbulent boundary layer flow was examined. Experiment is compared with current theory. A NACA 0012 airfoil of 0.61 m chord and 0.46 m span was immersed in the laminar flow of a low turbulence open jet. A 2.54 cm width roughness strip was placed at 15 percent chord from the leading edge on both sides of the airfoil as a boundary layer trip so that two separate but statistically equivalent turbulent boundary layers were formed. Tests were performed with several trailing-edge geometries with the upstream velocity U sub infinity ranging from a value of 30.9 m/s up to 73.4 m/s. Properties of the boundary layer for the airfoil and pressure fluctuations in the vicinity of the trailing-edge were examined. A scattered pressure field due to the presence of the trailing-edge was observed and is suggested as a possible sound producing mechanism for the trailing-edge noise.

  2. On INM's Use of Corrected Net Thrust for the Prediction of Jet Aircraft Noise

    NASA Technical Reports Server (NTRS)

    McAninch, Gerry L.; Shepherd, Kevin P.

    2011-01-01

    The Federal Aviation Administration s (FAA) Integrated Noise Model (INM) employs a prediction methodology that relies on corrected net thrust as the sole correlating parameter between aircraft and engine operating states and aircraft noise. Thus aircraft noise measured for one set of atmospheric and aircraft operating conditions is assumed to be applicable to all other conditions as long as the corrected net thrust remains constant. This hypothesis is investigated under two primary assumptions: (1) the sound field generated by the aircraft is dominated by jet noise, and (2) the sound field generated by the jet flow is adequately described by Lighthill s theory of noise generated by turbulence.

  3. Computer program to predict noise of general aviation aircraft: User's guide

    NASA Technical Reports Server (NTRS)

    Mitchell, J. A.; Barton, C. K.; Kisner, L. S.; Lyon, C. A.

    1982-01-01

    Program NOISE predicts General Aviation Aircraft far-field noise levels at FAA FAR Part 36 certification conditions. It will also predict near-field and cabin noise levels for turboprop aircraft and static engine component far-field noise levels.

  4. Swirling-flow jet noise suppressors for aircraft engines

    NASA Technical Reports Server (NTRS)

    Schwartz, I. R.

    1976-01-01

    Experimental investigations of the effects of swirling the jet exhausts of small turbofan and turbojet engines have indicated significant progress towards predicting and attaining substantial jet noise abatement with minimum thrust losses in large aircraft engines. Systematic variations of the important swirl vane and swirling flow parameters were conducted to determine their effects on jet noise reduction and engine performance. Since swirling flow becomes more effective in reducing jet noise as the density and temperature gradients increase, the significant trends in noise reduction and engine performance that were established by these parametric studies could be projected into potentially greater reductions of sound pressure levels with minimum thrust losses by controlled swirling of the jets of high thrust engines. The density and temperature gradients in the jet exhausts of high thrust engines are larger by comparison with gradients in small engines.

  5. Atmospheric turbulence effects on aircraft noise propagation

    NASA Technical Reports Server (NTRS)

    Chapkis, R. L.

    1979-01-01

    The Brown and Clifford model for the apparent sound attenuation cuased by atmospheric turbulence was reviewed and extended. Calculations, based on the model, were made for the predicted sound attenuation for a tower-mounted loudspeaker-type sound source and for an airplane sound source. The important parameters in the model are identified and discussed. A model for sound fluctuations is also presented and a practical experimental program to validate the models described.

  6. Computation of Engine Noise Propagation and Scattering Off an Aircraft

    NASA Technical Reports Server (NTRS)

    Xu, J.; Stanescu, D.; Hussaini, M. Y.; Farassat, F.

    2003-01-01

    The paper presents a comparison of experimental noise data measured in flight on a two-engine business jet aircraft with Kulite microphones placed on the suction surface of the wing with computational results. Both a time-domain discontinuous Galerkin spectral method and a frequency-domain spectral element method are used to simulate the radiation of the dominant spinning mode from the engine and its reflection and scattering by the fuselage and the wing. Both methods are implemented in computer codes that use the distributed memory model to make use of large parallel architectures. The results show that trends of the noise field are well predicted by both methods.

  7. Structureborne noise measurements on a small twin-engine aircraft

    NASA Technical Reports Server (NTRS)

    Cole, J. E., III; Martini, K. F.

    1988-01-01

    Structureborne noise measurements performed on a twin-engine aircraft (Beechcraft Baron) are reported. There are two overall objectives of the test program. The first is to obtain data to support the development of analytical models of the wing and fuselage, while the second is to evaluate effects of structural parameters on cabin noise. Measurements performed include structural and acoustic responses to impact excitation, structural and acoustic loss factors, and modal parameters of the wing. Path alterations include added mass to simulate fuel, variations in torque of bolts joining wing and fuselage, and increased acoustic absorption. Conclusions drawn regarding these measurements are presented.

  8. Structureborne noise measurements on a small twin-engine aircraft

    NASA Astrophysics Data System (ADS)

    Cole, J. E., III; Martini, K. F.

    1988-06-01

    Structureborne noise measurements performed on a twin-engine aircraft (Beechcraft Baron) are reported. There are two overall objectives of the test program. The first is to obtain data to support the development of analytical models of the wing and fuselage, while the second is to evaluate effects of structural parameters on cabin noise. Measurements performed include structural and acoustic responses to impact excitation, structural and acoustic loss factors, and modal parameters of the wing. Path alterations include added mass to simulate fuel, variations in torque of bolts joining wing and fuselage, and increased acoustic absorption. Conclusions drawn regarding these measurements are presented.

  9. Canada's first fixed-site aircraft noise monitoring system

    SciTech Connect

    Standen, N.M.

    1982-01-01

    The nature of aircraft noise management in Canada as it is presently evolving is discussed. The population of aircraft operating in Canada is similar to most western nations with regard to aircraft type. Canada's airport system includes major airports owned and operated by the federal Department of Transport (Transport Canada), airports owned and operated by provinces, municipalities or local commissions, and privately owned and operated airports, largely catering to general aviation. In addition, there are airports which are owned by Transport Canada, but operated by another agency. The consequence of this arrangement is that the major jet transport traffic is handled by airports which are owned and operated by either Transport Canada or another government agency.

  10. New technique for the direct measurement of core noise from aircraft engines

    NASA Technical Reports Server (NTRS)

    Krejsa, E. A.

    1981-01-01

    A new technique is presented for directly measuring the core noise levels from gas turbine aircraft engines. The technique requires that fluctuating pressures be measured in the far-field and at two locations within the engine core. The cross-spectra of these measurements are used to determine the levels of the far-field noise that propagated from the engine core. The technique makes it possible to measure core noise levels even when other noise sources dominate. The technique was applied to signals measured from an AVCO Lycoming YF102 turbofan engine. Core noise levels as a function of frequency and radiation angle were measured and are presented over a range of power settings.

  11. Examination of the Lateral Attenuation of Aircraft Noise

    NASA Technical Reports Server (NTRS)

    Plotkin, Kenneth J.; Hobbs, Christopher M.; Bradley, Kevin A.; Shepherd, Kevin P. (Technical Monitor)

    2000-01-01

    Measurements of the lateral attenuation of noise from aircraft operations at Denver International Airport were made at distances up to 2000 feet and elevation angles up to 27 degrees. Attenuation Calculated from modem ground impedance theory agrees well with average measured attenuation. The large variability between measured and predicted levels observed at small elevation angles is demonstrated to be due to refraction by wind and temperature gradients.

  12. Active noise control using noise source having adaptive resonant frequency tuning through stress variation

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by an expandable ring embedded in the noise radiating element. Excitation of the ring causes expansion or contraction of the ring, thereby varying the stress in the noise radiating element. The ring is actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the ring, causing the ring to expand or contract. Instead of a single ring embedded in the noise radiating panel, a first expandable ring can be bonded to one side of the noise radiating element, and a second expandable ring can be bonded to the other side.

  13. Relationship between low-frequency aircraft noise and annoyance due to rattle and vibration.

    PubMed

    Fidell, Sanford; Pearsons, Karl; Silvati, Laura; Sneddon, Matthew

    2002-04-01

    A near-replication of a study of the annoyance of rattle and vibration attributable to aircraft noise [Fidell et al., J. Acoust. Soc. Am. 106, 1408-1415 (1999)] was conducted in the vicinity of Minneapolis-St. Paul International Airport (MSP). The findings of the current study were similar to those reported earlier with respect to the types of objects cited as sources of rattle in homes, frequencies of notice of rattle, and the prevalence of annoyance due to aircraft noise-induced rattle. A reliably lower prevalence rate of annoyance (but not of complaints) with rattle and vibration was noted among respondents living in homes that had been treated to achieve a 5-dB improvement in A-weighted noise reduction than among respondents living in untreated homes. This difference is not due to any substantive increase in low-frequency noise reduction of acoustically treated homes, but may be associated with installation of nonrattling windows. Common interpretations of the prevalence of a consequential degree of annoyance attributable to low-frequency aircraft noise may be developed from the combined results of the present and prior studies.

  14. The relationship between civil aircraft noise and community annoyance in Korea

    NASA Astrophysics Data System (ADS)

    Lim, Changwoo; Kim, Jaehwan; Hong, Jiyoung; Lee, Soogab; Lee, Soojoo

    2007-01-01

    Studies of community annoyance caused by civil aircraft noise exposure were carried out in 18 areas around Gimpo and Gimhae international airports in order to accumulate social survey data and assess the relationship between aircraft noise levels and annoyance responses in Korea. WECPNL, adopted as the aircraft noise index in Korea, and the percentage of respondents who felt highly annoyed (%HA) have been used to assess the dose-response of aircraft noise. Aircraft noise levels were measured automatically by airport noise monitoring system, B&K type 3597. Social surveys were carried out to people living within 100 m of noise measurement points. The Questionnaire used in the survey contained demographic factors, noise annoyance, interference with daily activities and health-related symptoms. The question relating to the aircraft noise annoyance was answered on an 11-point numerical scale. The randomly selected respondents who were aged between 18 and 70 years completed the questionnaire by themselves. In total, 705 respondents participated in the questionnaire. The results show that WECPNL, noise metric considering characteristics of event and intrusive noise, is more reasonable than L dn, noise metric considering total sound, to assess the effects of aircraft noise on health. It is also shown that the annoyance responses caused by aircraft noise in Korea seems higher than those reported in other countries.

  15. The Influences of Lamination Angles on the Interior Noise Levels of an Aircraft

    NASA Technical Reports Server (NTRS)

    Fernholz, Christian M.; Robinson, Jay H.

    1996-01-01

    The feasibility of reducing the interior noise levels of an aircraft passenger cabin through optimization of the composite lay up of the fuselage is investigated. MSC/NASTRAN, a commercially available finite element code, is used to perform the dynamic analysis and subsequent optimization of the fuselage. The numerical calculation of sensitivity of acoustic pressure to lamination angle is verified using a simple thin, cylindrical shell with point force excitations as noise sources. The thin shell used represents a geometry similar to the fuselage and analytic solutions are available for the cylindrical thin shell equations of motion. Optimization of lamination angle for the reduction of interior noise is performed using a finite element model of an actual aircraft fuselage. The aircraft modeled for this study is the Beech Starship. Point forces simulate the structure borne noise produced by the engines and are applied to the fuselage at the wing mounting locations. These forces are the noise source for the optimization problem. The acoustic pressure response is reduced at a number of points in the fuselage and over a number of frequencies. The objective function is minimized with the constraint that it be larger than the maximum sound pressure level at the response points in the passenger cabin for all excitation frequencies in the range of interest. Results from the study of the fuselage model indicate that a reduction in interior noise levels is possible over a finite frequency range through optimal configuration of the lamination angles in the fuselage. Noise reductions of roughly 4 dB were attained. For frequencies outside the optimization range, the acoustic pressure response may increase after optimization. The effects of changing lamination angle on the overall structural integrity of the airframe are not considered in this study.

  16. Simple method for prediction of aircraft noise contours

    NASA Technical Reports Server (NTRS)

    Stewart, E. C.; Carson, T. M.

    1980-01-01

    A method for generating noise contours more rapidly and more simply than previously used programs is discussed. The method gives the area, the noise contour, and its extremities for an arbitrarily complex flight path for both takeoffs and landings with relative ease. The analysis reveals the fundamental nature of the contours and how the various factors that influence its size and shape enter into the analysis. It is noted that the effects of ground attenuation and shielding are omitted as they are important only on the initial portion of flight and are highly dependent upon aircraft configuration. However, the analysis shows that these effects could be included. It is emphasized the the single-event contour is an obvious choice for purposes of minimizing noise impact.

  17. An evaluation of methods for scaling aircraft noise perception

    NASA Technical Reports Server (NTRS)

    Ollerhead, J. B.

    1971-01-01

    One hundred and twenty recorded sounds, including jets, turboprops, piston engined aircraft and helicopters were rated by a panel of subjects in a paired comparison test. The results were analyzed to evaluate a number of noise rating procedures in terms of their ability to accurately estimate both relative and absolute perceived noise levels. It was found that the complex procedures developed by Stevens, Zwicker and Kryter are superior to other scales. The main advantage of these methods over the more convenient weighted sound pressure level scales lies in their ability to cope with signals over a wide range of bandwidth. However, Stevens' loudness level scale and the perceived noise level scale both overestimate the growth of perceived level with intensity because of an apparent deficiency in the band level summation rule. A simple correction is proposed which will enable these scales to properly account for the experimental observations.

  18. Investigation of the relationship between aircraft noise and community annoyance in China.

    PubMed

    Guoqing, Di; Xiaoyi, Liu; Xiang, Shi; Zhengguang, Li; Qili, Lin

    2012-01-01

    A survey of community annoyance induced by aircraft noise exposure was carried out around Hangzhou Xiaoshan International Airport. To investigate the relationship curves between aircraft noise and the percentage of "highly annoyed" persons in China and also to get annoyance threshold of aircraft noise in China. Noise annoyance induced by aircraft noise exposure was assessed by 764 local residents around the airport using the International Commission on Biological Effect of Noise (ICBEN) scale. The status quo of aircraft noise pollution was measured by setting up 39 monitoring points. The interpolation was used to estimate the weighted effective continuous perceived noise levels (LWECPN) in different areas around the airport, and the graph of equal noise level contour was drawn. The membership function was used to calculate the annoyance threshold of aircraft noise. Data were analyzed using SPSS 16.0 and Origin 8.0. The results showed that if LWECPN was 64.3 dB (Ldn was 51.4 dB), then 15% respondents were highly annoyed. If LWECPN was 68.1 dB (Ldn was 55.0 dB), then 25% respondents were highly annoyed. The annoyance threshold of aircraft noise (LWECPN) was 73.7 dB, while the annoyance threshold of a single flight incident instantaneous noise level (LAmax) was 72.9 dB. People around the airport had felt annoyed before the aircraft noise LWECPN reached the standard limit.

  19. Effects of duration and other noise characteristics on the annoyance caused by aircraft-flyover noise

    NASA Technical Reports Server (NTRS)

    Mccurdy, D. A.; Powell, C. A.

    1979-01-01

    A laboratory experiment was conducted to determine the effects of duration and other noise characteristics on the annoyance caused by aircraft-flyover noise. Duration, doppler shift, and spectra were individually controlled by specifying aircraft operational factors, such as velocity, altitude, and spectrum, in a computer synthesis of the aircraft-noise stimuli. This control allowed the separation of the effects of duration from the other main factors in the experimental design: velocity, tonal content, and sound pressure level. The annoyance of a set of noise stimuli which were comprised of factorial combinations of a 3 durations, 3 velocities, 3 sound pressure levels, and 2 tone conditions were judged. The judgements were made by using a graphical scale procedure similar to numerical category scaling. Each of the main factors except velocity was found to affect the judged annoyance significantly. The interaction of tonal content with sound pressure level was also found to be significant. The duration correction used in the effective-perceived-noise-level procedure, 3 dB per doubling of effective duration, was found to account most accurately for the effect of duration. No significant effect doppler shift was found.

  20. Active noise control using noise source having adaptive resonant frequency tuning through variable ring loading

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of noise radiating structure is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating structure is tuned by a plurality of drivers arranged to contact the noise radiating structure. Excitation of the drivers causes expansion or contraction of the drivers, thereby varying the edge loading applied to the noise radiating structure. The drivers are actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the drivers, causing them to expand or contract. The noise radiating structure may be either the outer shroud of the engine or a ring mounted flush with an inner wall of the shroud or disposed in the interior of the shroud.

  1. Measuring subjective response to aircraft noise: the effects of survey context.

    PubMed

    Kroesen, Maarten; Molin, Eric J E; van Wee, Bert

    2013-01-01

    In applied research, noise annoyance is often used as indicator of subjective reaction to aircraft noise in residential areas. The present study aims to show that the meaning which respondents attach to the concept of aircraft noise annoyance is partly a function of survey context. To this purpose a survey is conducted among residents living near Schiphol Airport, the largest airport in the Netherlands. In line with the formulated hypotheses it is shown that different sets of preceding questionnaire items influence the response distribution of aircraft noise annoyance as well as the correlational patterns between aircraft noise annoyance and other relevant scales.

  2. Federal Interagency Committee on Aviation Noise (FICAN) Position on Research into Effects of Aircraft Noise on Classroom Learning.

    ERIC Educational Resources Information Center

    2000

    This symposium report presents a summary of research on the affect of aircraft noise on the classroom environment revealing that aircraft noise can interfere with learning in the following areas: reading, motivation, language and speech acquisition, and memory. The strongest findings are in the area of reading, where more than 20 studies have…

  3. Jet Noise Shielding Provided by a Hybrid Wing Body Aircraft

    NASA Technical Reports Server (NTRS)

    Doty, Michael J.; Brooks, Thomas F.; Burley, Casey L.; Bahr, Christopher J.; Pope, Dennis S.

    2014-01-01

    One approach toward achieving NASA's aggressive N+2 noise goal of 42 EPNdB cumulative margin below Stage 4 is through the use of novel vehicle configurations like the Hybrid Wing Body (HWB). Jet noise measurements from an HWB acoustic test in NASA Langley's 14- by 22-Foot Subsonic Tunnel are described. Two dual-stream, heated Compact Jet Engine Simulator (CJES) units are mounted underneath the inverted HWB model on a traversable support to permit measurement of varying levels of shielding provided by the fuselage. Both an axisymmetric and low noise chevron nozzle set are investigated in the context of shielding. The unshielded chevron nozzle set shows 1 to 2 dB of source noise reduction (relative to the unshielded axisymmetric nozzle set) with some penalties at higher frequencies. Shielding of the axisymmetric nozzles shows up to 6.5 dB of reduction at high frequency. The combination of shielding and low noise chevrons shows benefits beyond the expected additive benefits of the two, up to 10 dB, due to the effective migration of the jet source peak noise location upstream for increased shielding effectiveness. Jet noise source maps from phased array results processed with the Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS) algorithm reinforce these observations.

  4. The NASA aircraft noise prediction program improved propeller analysis system

    NASA Technical Reports Server (NTRS)

    Nguyen, L. Cathy

    1991-01-01

    The improvements and the modifications of the NASA Aircraft Noise Prediction Program (ANOPP) and the Propeller Analysis System (PAS) are described. Comparisons of the predictions and the test data are included in the case studies for the flat plate model in the Boundary Layer Module, for the effects of applying compressibility corrections to the lift and pressure coefficients, for the use of different weight factors in the Propeller Performance Module, for the use of the improved retarded time equation solution, and for the effect of the number grids in the Transonic Propeller Noise Module. The DNW tunnel test data of a propeller at different angles of attack and the Dowty Rotol data are compared with ANOPP predictions. The effect of the number of grids on the Transonic Propeller Noise Module predictions and the comparison of ANOPP TPN and DFP-ATP codes are studied. In addition to the above impact studies, the transonic propeller noise predictions for the SR-7, the UDF front rotor, and the support of the enroute noise test program are included.

  5. Investigation of hydraulic transmission noise sources

    NASA Astrophysics Data System (ADS)

    Klop, Richard J.

    Advanced hydrostatic transmissions and hydraulic hybrids show potential in new market segments such as commercial vehicles and passenger cars. Such new applications regard low noise generation as a high priority, thus, demanding new quiet hydrostatic transmission designs. In this thesis, the aim is to investigate noise sources of hydrostatic transmissions to discover strategies for designing compact and quiet solutions. A model has been developed to capture the interaction of a pump and motor working in a hydrostatic transmission and to predict overall noise sources. This model allows a designer to compare noise sources for various configurations and to design compact and inherently quiet solutions. The model describes dynamics of the system by coupling lumped parameter pump and motor models with a one-dimensional unsteady compressible transmission line model. The model has been verified with dynamic pressure measurements in the line over a wide operating range for several system structures. Simulation studies were performed illustrating sensitivities of several design variables and the potential of the model to design transmissions with minimal noise sources. A semi-anechoic chamber has been designed and constructed suitable for sound intensity measurements that can be used to derive sound power. Measurements proved the potential to reduce audible noise by predicting and reducing both noise sources. Sound power measurements were conducted on a series hybrid transmission test bench to validate the model and compare predicted noise sources with sound power.

  6. A Framework for Simulation of Aircraft Flyover Noise Through a Non-Standard Atmosphere

    NASA Technical Reports Server (NTRS)

    Arntzen, Michael; Rizzi, Stephen A.; Visser, Hendrikus G.; Simons, Dick G.

    2012-01-01

    This paper describes a new framework for the simulation of aircraft flyover noise through a non-standard atmosphere. Central to the framework is a ray-tracing algorithm which defines multiple curved propagation paths, if the atmosphere allows, between the moving source and listener. Because each path has a different emission angle, synthesis of the sound at the source must be performed independently for each path. The time delay, spreading loss and absorption (ground and atmosphere) are integrated along each path, and applied to each synthesized aircraft noise source to simulate a flyover. A final step assigns each resulting signal to its corresponding receiver angle for the simulation of a flyover in a virtual reality environment. Spectrograms of the results from a straight path and a curved path modeling assumption are shown. When the aircraft is at close range, the straight path results are valid. Differences appear especially when the source is relatively far away at shallow elevation angles. These differences, however, are not significant in common sound metrics. While the framework used in this work performs off-line processing, it is conducive to real-time implementation.

  7. A new approach to complete aircraft landing gear noise prediction

    NASA Astrophysics Data System (ADS)

    Lopes, Leonard V.

    This thesis describes a new landing gear noise prediction system developed at The Pennsylvania State University, called Landing Gear Model and Acoustic Prediction code (LGMAP). LGMAP is used to predict the noise of an isolated or installed landing gear geometry. The predictions include several techniques to approximate the aeroacoustic and aerodynamic interactions of landing gear noise generation. These include (1) a method for approximating the shielding of noise caused by the landing gear geometry, (2) accounting for local flow variations due to the wing geometry, (3) the interaction of the landing gear wake with high-lift devices, and (4) a method for estimating the effect of gross landing gear design changes on local flow and acoustic radiation. The LGMAP aeroacoustic prediction system has been created to predict the noise generated by a given landing gear. The landing gear is modeled as a set of simple components that represent individual parts of the structure. Each component, ranging from large to small, is represented by a simple geometric shape and the unsteady flow on the component is modeled based on an individual characteristic length, local flow velocity, and the turbulent flow environment. A small set of universal models is developed and applied to a large range of similar components. These universal models, combined with the actual component geometry and local environment, give a unique loading spectrum and acoustic field for each component. Then, the sum of all the individual components in the complete configuration is used to model the high level of geometric complexity typical of current aircraft undercarriage designs. A line of sight shielding algorithm based on scattering by a two-dimensional cylinder approximates the effect of acoustic shielding caused by the landing gear. Using the scattering from a cylinder in two-dimensions at an observer position directly behind the cylinder, LGMAP is able to estimate the reduction in noise due to shielding

  8. A Lightweight Loudspeaker for Aircraft Communications and Active Noise Control

    NASA Technical Reports Server (NTRS)

    Warnaka, Glenn E.; Kleinle, Mark; Tsangaris, Parry; Oslac, Michael J.; Moskow, Harry J.

    1992-01-01

    A series of new, lightweight loudspeakers for use on commercial aircraft has been developed. The loudspeakers use NdFeB magnets and aluminum alloy frames to reduce the weight. The NdFeB magnet is virtually encapsulated by steel in the new speaker designs. Active noise reduction using internal loudspeakers was demonstrated to be effective in 1983. A weight, space, and cost efficient method for creating the active sound attenuating fields is to use the existing cabin loudspeakers for both communication and sound attenuation. This will require some additional loudspeaker design considerations.

  9. Duct Liner Optimization for Turbomachinery Noise Sources

    DTIC Science & Technology

    1975-11-01

    AD-A279 441lIIIflhIh* NASA TECHNICAL NASA TMA X-72789 MEMORANDUM oo £ 00 r-:. DUCT LINER OPTIMIZATION FOR TURBOMACHINERY w NOISE SOURCES By Harold C...Recipient’s r.atalog No. NASA TM X-72789! 4 Title diid Subtitle 5. Rewrt Date Duct Liner Optimization for Turbomachinery Noise Sources November 1975...profiles is combined wit., a numerical minimization algorithm to predict optimal liner configurations having one, two, and three sections. Source models

  10. Applications of Response Surface-Based Methods to Noise Analysis in the Conceptual Design of Revolutionary Aircraft

    NASA Technical Reports Server (NTRS)

    Hill, Geoffrey A.; Olson, Erik D.

    2004-01-01

    Due to the growing problem of noise in today's air transportation system, there have arisen needs to incorporate noise considerations in the conceptual design of revolutionary aircraft. Through the use of response surfaces, complex noise models may be converted into polynomial equations for rapid and simplified evaluation. This conversion allows many of the commonly used response surface-based trade space exploration methods to be applied to noise analysis. This methodology is demonstrated using a noise model of a notional 300 passenger Blended-Wing-Body (BWB) transport. Response surfaces are created relating source noise levels of the BWB vehicle to its corresponding FAR-36 certification noise levels and the resulting trade space is explored. Methods demonstrated include: single point analysis, parametric study, an optimization technique for inverse analysis, sensitivity studies, and probabilistic analysis. Extended applications of response surface-based methods in noise analysis are also discussed.

  11. Effects of activity interference on annoyance due to aircraft noise

    NASA Technical Reports Server (NTRS)

    Willshire, K. F.; Powell, C. A.

    1981-01-01

    The effects of aircraft flyover noise on annoyance were compared for face to face conversation, reverie, and television viewing. Eighteen 5 minute sessions, each composed of three flyovers, were presented on each of 2 days to subjects in a simulated living room. Twelve pairs of females and 12 pairs of males were tested, once before and once after work. Flyovers varied in peak noise level from 53 to 83 dB, A weighted. On each day, subjects engaged in 18 sessions, six of conversation, six of television viewing, and six of reverie. The subjects completed subjective ratings of annoyance and acceptability following every session. Annoyance and unacceptability rating scores were significantly higher for the activity of television viewing compared to conversation or reverie. There was no difference between judgments during the latter two activities. No differences were found in the judgments when compared on the basis of "fatigue" (before/after work) or sex of the subject.

  12. Near-field noise predictions of an aircraft in cruise

    NASA Technical Reports Server (NTRS)

    Rawls, John W., Jr.

    1987-01-01

    The physics of the coupling of sound waves with the boundary layer is not yet well understood. It is believed, however, that for effective coupling of the sound waves and instability waves in the boundary layer, a matching of both frequency and wave number must occur. This requires that the sound field be accurately defined in both space and time. Currently analytical prediction methods lack sufficient accuracy to predict the noise levels from components of a turbofan engine. Although empirical methods do not yield the detail required for an analysis of the receptivity of sound by a boundary layer, valuable insight can be gained as to the changes in noise levels that might be expected under various operating conditions and aircraft configurations.

  13. Updating working memory in aircraft noise and speech noise causes different fMRI activations.

    PubMed

    Saetrevik, Bjørn; Sörqvist, Patrik

    2015-02-01

    The present study used fMRI/BOLD neuroimaging to investigate how visual-verbal working memory is updated when exposed to three different background-noise conditions: speech noise, aircraft noise and silence. The number-updating task that was used can distinguish between "substitution processes," which involve adding new items to the working memory representation and suppressing old items, and "exclusion processes," which involve rejecting new items and maintaining an intact memory set. The current findings supported the findings of a previous study by showing that substitution activated the dorsolateral prefrontal cortex, the posterior medial frontal cortex and the parietal lobes, whereas exclusion activated the anterior medial frontal cortex. Moreover, the prefrontal cortex was activated more by substitution processes when exposed to background speech than when exposed to aircraft noise. These results indicate that (a) the prefrontal cortex plays a special role when task-irrelevant materials should be denied access to working memory and (b) that, when compensating for different types of noise, either different cognitive mechanisms are involved or those cognitive mechanisms that are involved are involved to different degrees.

  14. Updating working memory in aircraft noise and speech noise causes different fMRI activations

    PubMed Central

    Sætrevik, Bjørn; Sörqvist, Patrik

    2015-01-01

    The present study used fMRI/BOLD neuroimaging to investigate how visual-verbal working memory is updated when exposed to three different background-noise conditions: speech noise, aircraft noise and silence. The number-updating task that was used can distinguish between “substitution processes,” which involve adding new items to the working memory representation and suppressing old items, and “exclusion processes,” which involve rejecting new items and maintaining an intact memory set. The current findings supported the findings of a previous study by showing that substitution activated the dorsolateral prefrontal cortex, the posterior medial frontal cortex and the parietal lobes, whereas exclusion activated the anterior medial frontal cortex. Moreover, the prefrontal cortex was activated more by substitution processes when exposed to background speech than when exposed to aircraft noise. These results indicate that (a) the prefrontal cortex plays a special role when task-irrelevant materials should be denied access to working memory and (b) that, when compensating for different types of noise, either different cognitive mechanisms are involved or those cognitive mechanisms that are involved are involved to different degrees. PMID:25352319

  15. Propeller aircraft interior noise model: User's manual for computer program

    NASA Technical Reports Server (NTRS)

    Wilby, E. G.; Pope, L. D.

    1985-01-01

    A computer program entitled PAIN (Propeller Aircraft Interior Noise) has been developed to permit calculation of the sound levels in the cabin of a propeller-driven airplane. The fuselage is modeled as a cylinder with a structurally integral floor, the cabin sidewall and floor being stiffened by ring frames, stringers and floor beams of arbitrary configurations. The cabin interior is covered with acoustic treatment and trim. The propeller noise consists of a series of tones at harmonics of the blade passage frequency. Input data required by the program include the mechanical and acoustical properties of the fuselage structure and sidewall trim. Also, the precise propeller noise signature must be defined on a grid that lies in the fuselage skin. The propeller data are generated with a propeller noise prediction program such as the NASA Langley ANOPP program. The program PAIN permits the calculation of the space-average interior sound levels for the first ten harmonics of a propeller rotating alongside the fuselage. User instructions for PAIN are given in the report. Development of the analytical model is presented in NASA CR 3813.

  16. Noise and vibration reduction technology in aircraft internal cabin

    NASA Astrophysics Data System (ADS)

    Takahashi, Kosaku; Monzen, Hirotaka; Yamaoka, Toshihiro; Kusumoto, Koji; Bansaku, Kazuhiro; Kimoto, Junichi; Isoe, Akira; Hirose, Yasuo; Sanda, Tomio; Matsuzaki, Yuji

    2003-08-01

    The study to reduce noise and vibration in aircraft cabin through PZT was implemented, using a semi-monocoque structure, 1.5m in diameter and 3.0m long with 2.3mm skin, which stimulates an aircraft body. We utilized PZT of 480 pieces bonded on inner surface of the structure as sensor and actuator. We applied random noise of low frequency range between 0~500Hz to the test model. We tried to reduce the vibration level of structure and internal air due to the external load by controlling the PZTs. Two control methods, gain control and feed-forward control, were tried. We measured internal sound pressure on 150 spots and compared overall values of sound pressure with gain control to them without control and evaluated its reduction capability. The tests showed 4.0dB O.A. reduction at maximum in gain control and 3.5dB O.A. reduction at maximum in feed forward control.

  17. Noise Reduction in an Aircraft Fuselage Model Using Active Trim Panels

    NASA Technical Reports Server (NTRS)

    Silcox, Richard J.; Lyle, Karen H.

    1996-01-01

    An experiment was conducted to evaluate the use of force actuators on a model aircraft interior trim panel as the control element for active control of interior noise. The trim panel, designed specifically for this study, was constructed in three large identical sections and hard mounted to the ring frames of the primary structure. Piezoceramic actuators were bonded to the outer surface of the trim panels. Studies of the interior pressure response due to both the primary source alone and control sources alone were conducted as well as the control cases. A single acoustic loudspeaker, centered at the axial midpoint, generated the acoustic field to be controlled.

  18. Advanced turboprop aircraft flyover noise annoyance - Comparison of different propeller configurations

    NASA Technical Reports Server (NTRS)

    Mccurdy, David A.

    1989-01-01

    A laboratory experiment was conducted to compare the annoyance of flyover noise from advanced turboprop aircraft having different propeller configurations with the annoyance of conventional turboprop and jet aircraft flyover noise. It was found that advanced turboprops with single-rotating propellers were, on average, slightly less annoying than the other aircraft. Fundamental frequency and tone-to-broadband noise ratio affected annoyance response to advanced turboprops but the effects varied with propeller configuration and noise metric. The addition of duration corrections and corrections for tones above 500 Hz to the noise measurement procedures improved prediction ability.

  19. A LOW NOISE RF SOURCE FOR RHIC.

    SciTech Connect

    HAYES,T.

    2004-07-05

    The Relativistic Heavy Ion Collider (RHIC) requires a low noise rf source to ensure that beam lifetime during a store is not limited by the rf system. The beam is particularly sensitive to noise from power line harmonics. Additionally, the rf source must be flexible enough to handle the frequency jump required for rebucketing (transferring bunches from the acceleration to the storage rf systems). This paper will describe the design of a Direct Digital Synthesizer (DDS) based system that provides both the noise performance and the flexibility required.

  20. Radiant Energy Power Source for Jet Aircraft

    SciTech Connect

    Doellner, O.L.

    1992-02-01

    This report beings with a historical overview on the origin and early beginnings of Radiant Energy Power Source for Jet Aircraft. The report reviews the work done in Phase I (Grant DE-FG01-82CE-15144) and then gives a discussion of Phase II (Grant DE-FG01-86CE-15301). Included is a reasonably detailed discussion of photovoltaic cells and the research and development needed in this area. The report closes with a historical perspective and summary related to situations historically encountered on projects of this nature. 15 refs.

  1. Aircraft interior noise reduction by alternate resonance tuning

    NASA Technical Reports Server (NTRS)

    Gottwald, James A.; Bliss, Donald B.

    1990-01-01

    The focus is on a noise control method which considers aircraft fuselages lined with panels alternately tuned to frequencies above and below the frequency that must be attenuated. An interior noise reduction called alternate resonance tuning (ART) is described both theoretically and experimentally. Problems dealing with tuning single paneled wall structures for optimum noise reduction using the ART methodology are presented, and three theoretical problems are analyzed. The first analysis is a three dimensional, full acoustic solution for tuning a panel wall composed of repeating sections with four different panel tunings within that section, where the panels are modeled as idealized spring-mass-damper systems. The second analysis is a two dimensional, full acoustic solution for a panel geometry influenced by the effect of a propagating external pressure field such as that which might be associated with propeller passage by a fuselage. To reduce the analysis complexity, idealized spring-mass-damper panels are again employed. The final theoretical analysis presents the general four panel problem with real panel sections, where the effect of higher structural modes is discussed. Results from an experimental program highlight real applications of the ART concept and show the effectiveness of the tuning on real structures.

  2. Noise-induced annoyance from transportation noise: short-term responses to a single noise source in a laboratory.

    PubMed

    Kim, Jaehwan; Lim, Changwoo; Hong, Jiyoung; Lee, Soogab

    2010-02-01

    An experimental study was performed to compare the annoyances from civil-aircraft noise, military-aircraft noise, railway noise, and road-traffic noise. Two-way within-subjects designs were applied in this research. Fifty-two subjects, who were naive listeners, were given various stimuli with varying levels through a headphone in an anechoic chamber. Regardless of the frequency weighting network, even under the same average energy level, civil-aircraft noise was the most annoying, followed by military-aircraft noise, railway noise, and road-traffic noise. In particular, penalties in the time-averaged, A-weighted sound level (TAL) of about 8, 5, and 5 dB, respectively, were found in the civil-aircraft, military-aircraft, and railway noises. The reason could be clarified through the high-frequency component and the variability in the level. When people were exposed to sounds with the same maximum A-weighted level, a railway bonus of about 3 dB was found. However, transportation noise has been evaluated by the time-averaged A-weighted level in most countries. Therefore, in the present situation, the railway bonus is not acceptable for railway vehicles with diesel-electric engines.

  3. AVIATION AND THE ENVIRONMENT: Transition to Quieter Aircraft Occurred as Planned, but Concerns About Noise Persist

    DTIC Science & Technology

    2001-09-01

    International Civil Aviation Organization ( ICAO ) to develop a more stringent aircraft noise standard for subsonic jets and large propeller-driven aircraft...On June 27, 2001, the ICAO Council approved the adoption of a new noise certification standard called Chapter 4.

  4. A pilot study of human response to general aviation aircraft noise

    NASA Technical Reports Server (NTRS)

    Stearns, J.; Brown, R.; Neiswander, P.

    1983-01-01

    A pilot study, conducted to evaluate procedures for measuring the noise impact and community response to general aviation aircraft around Torrance Municipal Airport, a typical large GA airport, employed Torrance Airport's computer-based aircraft noise monitoring system, which includes nine permanent monitor stations surrounding the airport. Some 18 residences near these monitor stations were equipped with digital noise level recorders to measure indoor noise levels. Residents were instructed to fill out annoyance diaries for periods of 5-6 days, logging the time of each annoying aircraft overflight noise event and judging its degree of annoyance on a seven-point scale. Among the noise metrics studied, the differential between outdoor maximum A-weighted noise level of the aircraft and the outdoor background level showed the best correlation with annoyance; this correlation was clearly seen at only high noise levels, And was only slightly better than that using outdoor aircraft noise level alone. The results indicate that, on a national basis, a telephone survey coupled with outdoor noise measurements would provide an efficient and practical means of assessing the noise impact of general aviation aircraft.

  5. Determining the direction of causality between psychological factors and aircraft noise annoyance.

    PubMed

    Kroesen, Maarten; Molin, Eric J E; van Wee, Bert

    2010-01-01

    In this paper, an attempt is made to establish the direction of causality between a range of psychological factors and aircraft noise annoyance. For this purpose, a panel model was estimated within a structural equation modeling approach. Data were gathered from two surveys conducted in April 2006 and April 2008, respectively, among the same residents living within the 45 Level day-evening-night contour of Amsterdam Airport Schiphol, the largest airport in the Netherlands (n=250). A surprising result is that none of the paths from the psychological factors to aircraft noise annoyance were found to be significant. Yet 2 effects were significant the other way around: (1) from 'aircraft noise annoyance' to 'concern about the negative health effects of noise' and (2) from 'aircraft noise annoyance' to 'belief that noise can be prevented.' Hence aircraft noise annoyance measured at time 1 contained information that can effectively explain changes in these 2 variables at time 2, while controlling for their previous values. Secondary results show that (1) aircraft noise annoyance is very stable through time and (2) that changes in aircraft noise annoyance and the identified psychological factors are correlated.

  6. Policy discourse, people's internal frames, and declared aircraft noise annoyance: an application of Q-methodology.

    PubMed

    Kroesen, Maarten; Bröer, Christian

    2009-07-01

    Aircraft noise annoyance is studied extensively, but often without an explicit theoretical framework. In this article, a social approach for noise annoyance is proposed. The idea that aircraft noise is meaningful to people within a socially produced discourse is assumed and tested. More particularly, it is expected that the noise policy discourse influences people's assessment of aircraft noise. To this end, Q-methodology is used, which, to the best of the authors' knowledge, has not been used for aircraft noise annoyance so far. Through factor analysis five distinct frames are revealed: "Long live aviation!," "aviation: an ecological threat," "aviation and the environment: a solvable problem," "aircraft noise: not a problem," and "aviation: a local problem." It is shown that the former three frames are clearly related to the policy discourse. Based on this observation it is argued that policy making is a possible mechanism through which the sound of aircraft is turned into annoyance. In addition, it is concluded that the experience of aircraft noise and, in particular, noise annoyance is part of coherent frames of mind, which consist of mutually reinforcing positions and include non-acoustical factors.

  7. Aircraft Engine Noise Scattering - A Discontinuous Spectral Element Approach

    NASA Technical Reports Server (NTRS)

    Stanescu, D.; Hussaini, M. Y.; Farassat, F.

    2002-01-01

    The paper presents a time-domain method for computation of sound radiation from aircraft engine sources to the far-field. The effects of nonuniform flow around the aircraft and scattering of sound by fuselage and wings are accounted for in the formulation. Our approach is based on the discretization of the inviscid flow equations through a collocation form of the Discontinuous Galerkin spectral element method. An isoparametric representation of the underlying geometry is used in order to take full advantage of the spectral accuracy of the method. Largescale computations are made possible by a parallel implementation based on message passing. Results obtained for radiation from an axisymmetric nacelle alone are compared with those obtained when the same nacelle is installed in a generic con.guration, with and without a wing.

  8. Community Response to Noise

    NASA Astrophysics Data System (ADS)

    Fidell, Sandy

    The primary effects of community noise on residential populations are speech interference, sleep disturbance, and annoyance. This chapter focuses on transportation noise in general and on aircraft noise in particular because aircraft noise is one of the most prominent community noise sources, because airport/community controversies are often the most contentious and widespread, and because industrial and other specialized formsofcommunitynoise generally posemorelocalized problems.

  9. Workshop on Jet Exhaust Noise Reduction for Tactical Aircraft - NASA Perspective

    NASA Technical Reports Server (NTRS)

    Huff, Dennis L.; Henderson, Brenda S.

    2007-01-01

    Jet noise from supersonic, high performance aircraft is a significant problem for takeoff and landing operations near air bases and aircraft carriers. As newer aircraft with higher thrust and performance are introduced, the noise tends to increase due to higher jet exhaust velocities. Jet noise has been a subject of research for over 55 years. Commercial subsonic aircraft benefit from changes to the engine cycle that reduce the exhaust velocities and result in significant noise reduction. Most of the research programs over the past few decades have concentrated on commercial aircraft. Progress has been made by introducing new engines with design features that reduce the noise. NASA has recently started a new program called "Fundamental Aeronautics" where three projects (subsonic fixed wing, subsonic rotary wing, and supersonics) address aircraft noise. For the supersonics project, a primary goal is to understand the underlying physics associated with jet noise so that improved noise prediction tools and noise reduction methods can be developed for a wide range of applications. Highlights from the supersonics project are presented including prediction methods for broadband shock noise, flow measurement methods, and noise reduction methods. Realistic expectations are presented based on past history that indicates significant jet noise reduction cannot be achieved without major changes to the engine cycle. NASA s past experience shows a few EPNdB (effective perceived noise level in decibels) can be achieved using low noise design features such as chevron nozzles. Minimal thrust loss can be expected with these nozzles (< 0.5%) and they may be retrofitted on existing engines. In the long term, it is desirable to use variable cycle engines that can be optimized for lower jet noise during takeoff operations and higher thrust for operational performance. It is also suggested that noise experts be included early in the design process for engine nozzle systems to participate

  10. Interior noise control ground test studies for advanced turboprop aircraft applications

    NASA Technical Reports Server (NTRS)

    Simpson, Myles A.; Cannon, Mark R.; Burge, Paul L.; Boyd, Robert P.

    1989-01-01

    The measurement and analysis procedures are documented, and the results of interior noise control ground tests conducted on a DC-9 aircraft test section are summarized. The objectives of these tests were to study the fuselage response characteristics of treated and untreated aircraft with aft-mount advanced turboprop engines and to analyze the effectiveness of selected noise control treatments in reducing passenger cabin noise on these aircraft. The results of fuselage structural mode surveys, cabin cavity surveys and sound intensity surveys are presented. The performance of various structural and cabin sidewall treatments is assessed, based on measurements of the resulting interior noise levels under simulated advanced turboprop excitation.

  11. Locating industrial VOC sources with aircraft observations.

    PubMed

    Toscano, P; Gioli, B; Dugheri, S; Salvini, A; Matese, A; Bonacchi, A; Zaldei, A; Cupelli, V; Miglietta, F

    2011-05-01

    Observation and characterization of environmental pollution, focussing on Volatile Organic Compounds (VOCs), in a high-risk industrial area, are particularly important in order to provide indications on a safe level of exposure, indicate eventual priorities and advise on policy interventions. The aim of this study is to use the Solid Phase Micro Extraction (SPME) method to measure VOCs, directly coupled with atmospheric measurements taken on a small aircraft environmental platform, to evaluate and locate the presence of VOC emission sources in the Marghera industrial area. Lab analysis of collected SPME fibres and subsequent analysis of mass spectrum and chromatograms in Scan Mode allowed the detection of a wide range of VOCs. The combination of this information during the monitoring campaign allowed a model (Gaussian Plume) to be implemented that estimates the localization of emission sources on the ground.

  12. Experimental investigation of outdoor propagation of finite-amplitude noise. [aircraft noise

    NASA Technical Reports Server (NTRS)

    Webster, D. A.; Blackstock, D. T.

    1978-01-01

    The outdoor propagation of finite amplitude acoustic waves was investigated using a conventional electroacoustic transmitter which was mounted on the ground and pointed upward in order to avoid ground reflection effects. The propagation path was parallel to a radio tower 85 m tall, whose elevator carried the receiving microphone. The observations and conclusions are as follows: (1) At the higher source levels nonlinear propagation distortion caused a strong generation of high frequency noise over the propagation path. For example, at 70 m for a frequency 2-3 octaves above the source noise band, the measured noise was up to 30 dB higher than the linear theory prediction. (2) The generation occurred in both the nearfield and the farfield of the transmitter. (3) At no measurement point was small-signal behavior established for the high requency noise. Calculations support the contention that the nonlinearity generated high frequency noise never becomes small-signal in its behavior, regardless of distance. (4) When measured spectra are scaled in frequency and level to make them comparable with spectra of actual jet noise, they are found to be well within the jet noise range. It is therefore entirely possible that nonlinear distortion affects jet noise.

  13. Aerodynamic Measurements of a Gulfstream Aircraft Model With and Without Noise Reduction Concepts

    NASA Technical Reports Server (NTRS)

    Neuhart, Dan H.; Hannon, Judith A.; Khorrami, Mehdi R.

    2014-01-01

    Steady and unsteady aerodynamic measurements of a high-fidelity, semi-span 18% scale Gulfstream aircraft model are presented. The aerodynamic data were collected concurrently with acoustic measurements as part of a larger aeroacoustic study targeting airframe noise associated with main landing gear/flap components, gear-flap interaction noise, and the viability of related noise mitigation technologies. The aeroacoustic tests were conducted in the NASA Langley Research Center 14- by 22-Foot Subsonic Wind Tunnel with the facility in the acoustically treated open-wall (jet) mode. Most of the measurements were obtained with the model in landing configuration with the flap deflected at 39º and the main landing gear on and off. Data were acquired at Mach numbers of 0.16, 0.20, and 0.24. Global forces (lift and drag) and extensive steady and unsteady surface pressure measurements were obtained. Comparison of the present results with those acquired during a previous test shows a significant reduction in the lift experienced by the model. The underlying cause was traced to the likely presence of a much thicker boundary layer on the tunnel floor, which was acoustically treated for the present test. The steady and unsteady pressure fields on the flap, particularly in the regions of predominant noise sources such as the inboard and outboard tips, remained unaffected. It is shown that the changes in lift and drag coefficients for model configurations fitted with gear/flap noise abatement technologies fall within the repeatability of the baseline configuration. Therefore, the noise abatement technologies evaluated in this experiment have no detrimental impact on the aerodynamic performance of the aircraft model.

  14. Noise characteristics of an electromagnetic sea-ice thickness sounder on a fixed wing aircraft

    NASA Astrophysics Data System (ADS)

    Rabenstein, Lasse; Hendricks, Stefan; Lobach, John; Haas, Christian

    2011-09-01

    In this paper, the noise sources of an airborne electromagnetic frequency domain instrument used to measure sea-ice thickness are studied. The antennas are mounted on the wings of an aircraft. The paper presents real data examples showing that strong noise limited the accuracy of the thickness measurement to ± 0.5 m in the best case. Even drift cor­rection and frequency filtering did not reduce the noise to a level necessary for sea ice thickness measurements with an accuracy of 0.1 m. We show results of 3D finite element modeling of the coupling between transmitter and receiver coils and the aircraft, which indicate that wing flexure is the primary cause of the strong noise. Wing deflection angles below 5° relative to the fuselage are large enough to cause changes higher than the wanted signal from the seawater under the ice. Wing flexure noise can be divided into an inductive and geometric contribution, both of the same order. Most of the wing flexure signal appears on the inphase component only, hence the quadrature component should be taken for sea ice thickness retrievals when wing flexure is present even when the inphase produces a larger ocean sig­nal. Results also show that pitch and roll movements of the aircraft and electromagnetic coupling between seawater and aircraft can contribute significantly to the total noise. For flight heights of 30 m over the ocean these effects can change the sig­nal by about 10% or more. For highly quantitative measurements like sea-ice thickness all these effects must be taken into account. We conclude that a fixed wing electromagnetic instrument for the purpose of measure­ments in a centimeter scale must include instrumentation to measure the relative position of the antenna coils with an accuracy of 1/10 mm. Furthermore the antenna separation distance should be as large as possible in order to increase the measured ratio of secondary to primary magnetic field strength.

  15. Analytical Studies of Boundary Layer Generated Aircraft Interior Noise

    NASA Technical Reports Server (NTRS)

    Howe, M. S.; Shah, P. L.

    1997-01-01

    An analysis is made of the "interior noise" produced by high, subsonic turbulent flow over a thin elastic plate partitioned into "panels" by straight edges transverse to the mean flow direction. This configuration models a section of an aircraft fuselage that may be regarded as locally flat. The analytical problem can be solved in closed form to represent the acoustic radiation in terms of prescribed turbulent boundary layer pressure fluctuations. Two cases are considered: (i) the production of sound at an isolated panel edge (i.e., in the approximation in which the correlation between sound and vibrations generated at neighboring edges is neglected), and (ii) the sound generated by a periodic arrangement of identical panels. The latter problem is amenable to exact analytical treatment provided the panel edge conditions are the same for all panels. Detailed predictions of the interior noise depend on a knowledge of the turbulent boundary layer wall pressure spectrum, and are given here in terms of an empirical spectrum proposed by Laganelli and Wolfe. It is expected that these analytical representations of the sound generated by simplified models of fluid-structure interactions can used to validate more general numerical schemes.

  16. AGARD flight test techniques series. Volume 9: Aircraft exterior noise measurement and analysis techniques

    NASA Astrophysics Data System (ADS)

    Heller, H.

    1991-04-01

    Testing and analysis techniques to measure aircraft noise primarily for purposes of noise certification as specified by the 'International Civil Aviation Organization', ICAO are described. The relevant aircraft noise certification standards and recommended practices are presented in detail for subsonic jet aircraft, for heavy and light propeller-driven aircraft, and for helicopters. The practical execution of conducting noise certification tests is treated in depth. The characteristics and requirements of the acoustic and non-acoustic instrumentation for data acquisition and data processing are discussed, as are the procedures to determine the special noise measures - effective perceived noise level (EPNL) and maximum overall A-weighted noise level (L sub pA,max) - that are required for the noise certification of different types of aircraft. The AGARDograph also contains an extensive, although selective, discussion of test and analysis techniques for more detailed aircraft noise studies by means of either flight experiments or full-scale and model-scale wind tunnel experiments. Appendices provide supplementary information.

  17. Annoyance caused by advanced turboprop aircraft flyover noise: Comparison of different propeller configurations

    NASA Technical Reports Server (NTRS)

    Mccurdy, David A.

    1991-01-01

    A laboratory experiment was conducted to compare the annoyance of flyover noise from advanced turboprop aircraft having different propeller configurations with the annoyance of conventional turboprop and turbofan aircraft flyover noise. A computer synthesis system was used to generate 40 realistic, time varying simulations of advanced turboprop takeoff noise. Of the 40 noises, single-rotating propeller configurations (8) and counter-rotating propeller configurations with an equal (12) and unequal (20) number of blades on each rotor were represented. Analyses found that advanced turboprops with single-rotating propellers were, on average, slightly less annoying than the other aircraft. Fundamental frequency and tone-to-broadband noise ratio affected annoyance response to advanced turboprops, but the effects varied with propeller configuration and noise metric. The addition of duration corrections and corrections for tones above 500 Hz to the noise measurement procedures improved annoyance prediction ability.

  18. 75 FR 9327 - Aircraft Noise Certification Documents for International Operations

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-02

    ... the aircraft flight manual and approved as part of the aircraft's airworthiness certification, and... Airplane Flight Manual (AFM) or Rotorcraft Flight Manual (RFM) as part of an aircraft's certification... operating under part 121, a carrier is allowed to create an Aircraft Operations Manual (AOM) or a...

  19. System Noise Assessment of Blended-Wing-Body Aircraft With Open Rotor Propulsion

    NASA Technical Reports Server (NTRS)

    Guo, Yueping; Thomas, Russell H.

    2015-01-01

    An aircraft system noise study is presented for the Blended-Wing-Body (BWB) aircraft concept with three open rotor engines mounted on the upper surface of the airframe. It is shown that for such an aircraft, the cumulative Effective Perceived Noise Level (EPNL) is about 24 dB below the current aircraft noise regulations of Stage 4. While this makes the design acoustically viable in meeting the regulatory requirements, even with the consideration of more stringent noise regulations of a possible Stage 5 in the next decade or so, the design will likely meet stiff competitions from aircraft with turbofan engines. It is shown that the noise levels of the BWB design are held up by the inherently high noise levels of the open rotor engines and the limitation on the shielding benefit due to the practical design constraint on the engine location. Furthermore, it is shown that the BWB design has high levels of noise from the main landing gear, due to their exposure to high speed flow at the junction between the center body and outer wing. These are also the reasons why this baseline BWB design does not meet the NASA N+2 noise goal of 42 dB below Stage 4. To identify approaches that may further reduce noise, parametric studies are also presented, including variations in engine location, vertical tail and elevon variations, and airframe surface acoustic liner treatment effect. These have the potential to further reduce noise but they are only at the conceptual stage.

  20. Transport jet aircraft noise abatement in foreign countries: Growth, structure, impact. Volume 1: Europe, July 1980

    NASA Technical Reports Server (NTRS)

    Spencer, F. A.

    1980-01-01

    The development and implementation of aircraft noise control regulations in various European states are described. The countries include the United Kingdom, France, Switzerland, Federal Republic of Germany, Sweden, Denmark, and the Netherlands. Topics discussed include noise monitoring, airport curfews, land use planning, and the government structure for noise regulation.

  1. Some effects of the atmosphere and microphone placement on aircraft flyover noise measurements

    NASA Technical Reports Server (NTRS)

    Hosier, R. N.; Hilton, D. A.

    1975-01-01

    The effects of varying atmospheric conditions on certification-type noise measurements were studied. Tests were made under various atmospheric conditions at two test sites, Fresno, California, and Yuma, Arizona, using the same test aircraft, noise, and weather measuring equipment, and operating personnel. Measurements were made to determine the effects of the atmosphere and of microphone placement on aircraft flyover noise. The measurements were obtained for characterization of not only the acoustic signature of the test aircraft, but also specific atmospheric characteristics. Data are presented in the form of charts and tables which indicate that for a wide range of weather conditions, at both site locations, noise data were repeatable for similar aircraft operating conditions. The placement of microphones at ground level and at 1.2 m over both spaded sand and concrete illustrate the effects of ground reflections and surface impedance on the noise measurements.

  2. Preliminary noise tradeoff study of a Mach 2.7 cruise aircraft

    NASA Technical Reports Server (NTRS)

    Mascitti, V. R.; Maglieri, D. J. (Editor); Raney, J. P. (Editor)

    1979-01-01

    NASA computer codes in the areas of preliminary sizing and enroute performance, takeoff and landing performance, aircraft noise prediction, and economics were used in a preliminary noise tradeoff study for a Mach 2.7 design supersonic cruise concept. Aerodynamic configuration data were based on wind-tunnel model tests and related analyses. Aircraft structural characteristics and weight were based on advanced structural design methodologies, assuming conventional titanium technology. The most advanced noise prediction techniques available were used, and aircraft operating costs were estimated using accepted industry methods. The 4-engines cycles included in the study were based on assumed 1985 technology levels. Propulsion data was provided by aircraft manufacturers. Additional empirical data is needed to define both noise reduction features and other operating characteristics of all engine cycles under study. Data on VCE design parameters, coannular nozzle inverted flow noise reduction and advanced mechanical suppressors are urgently needed to reduce the present uncertainties in studies of this type.

  3. An acoustic range for the measurement of the noise signature of aircraft during flyby operations

    NASA Technical Reports Server (NTRS)

    Hilton, D. A.; Henderson, H. R.

    1978-01-01

    The remotely operated multiple array acoustic range (ROMAAR), which has been developed to give direct measurement and display of aircraft noise in several measurement units during takeoff, landing, and flyby operations, is described. The ROMAAR, which provides information on the ground noise signature of aircraft, represents a unique combination of state-of-the-art digital and analog noise-recording methods, computer-controlled digital communication methods, radar tracking facilities, quick-look weather (profile) capabilities, and sophisticated data handling routines and facilities. The ROMAAR, which is operated by NASA, allows direct data feedback to the NASA Aircraft Noise Prediction Office. As many as 38 simultaneous noise measurements can be made for each aircraft overflight.

  4. Definition of 1992 Technology Aircraft Noise Levels and the Methodology for Assessing Airplane Noise Impact of Component Noise Reduction Concepts

    NASA Technical Reports Server (NTRS)

    Kumasaka, Henry A.; Martinez, Michael M.; Weir, Donald S.

    1996-01-01

    This report describes the methodology for assessing the impact of component noise reduction on total airplane system noise. The methodology is intended to be applied to the results of individual study elements of the NASA-Advanced Subsonic Technology (AST) Noise Reduction Program, which will address the development of noise reduction concepts for specific components. Program progress will be assessed in terms of noise reduction achieved, relative to baseline levels representative of 1992 technology airplane/engine design and performance. In this report, the 1992 technology reference levels are defined for assessment models based on four airplane sizes - an average business jet and three commercial transports: a small twin, a medium sized twin, and a large quad. Study results indicate that component changes defined as program final goals for nacelle treatment and engine/airframe source noise reduction would achieve from 6-7 EPNdB reduction of total airplane noise at FAR 36 Stage 3 noise certification conditions for all of the airplane noise assessment models.

  5. Recent Developments in Aircraft Flyover Noise Simulation at NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Sullivan, Brenda M.; Aumann, Aric R.

    2008-01-01

    The NASA Langley Research Center is involved in the development of a new generation of synthesis and simulation tools for creation of virtual environments used in the study of aircraft community noise. The original emphasis was on simulation of flyover noise associated with subsonic fixed wing aircraft. Recently, the focus has shifted to rotary wing aircraft. Many aspects of the simulation are applicable to both vehicle classes. Other aspects, particularly those associated with synthesis, are more vehicle specific. This paper discusses the capabilities of the current suite of tools, their application to fixed and rotary wing aircraft, and some directions for the future.

  6. Optimizing an Actuator Array for the Control of Multi-Frequency Noise in Aircraft Interiors

    NASA Technical Reports Server (NTRS)

    Palumbo, D. L.; Padula, S. L.

    1997-01-01

    Techniques developed for selecting an optimized actuator array for interior noise reduction at a single frequency are extended to the multi-frequency case. Transfer functions for 64 actuators were obtained at 5 frequencies from ground testing the rear section of a fully trimmed DC-9 fuselage. A single loudspeaker facing the left side of the aircraft was the primary source. A combinatorial search procedure (tabu search) was employed to find optimum actuator subsets of from 2 to 16 actuators. Noise reduction predictions derived from the transfer functions were used as a basis for evaluating actuator subsets during optimization. Results indicate that it is necessary to constrain actuator forces during optimization. Unconstrained optimizations selected actuators which require unrealistically large forces. Two methods of constraint are evaluated. It is shown that a fast, but approximate, method yields results equivalent to an accurate, but computationally expensive, method.

  7. MPT Prediction of Aircraft-Engine Fan Noise

    NASA Technical Reports Server (NTRS)

    Connell, Stuart D.

    2004-01-01

    A collection of computer programs has been developed that implements a procedure for predicting multiple-pure-tone (MPT) noise generated by fan blades of an aircraft engine (e.g., a turbofan engine). MPT noise arises when the fan is operating with supersonic relative tip Mach No. Under this flow condition, there is a strong upstream running shock. The strength and position of this shock are very sensitive to blade geometry variations. For a fan where all the blades are identical, the primary tone observed upstream of the fan will be the blade passing frequency. If there are small variations in geometry between blades, then tones below the blade passing frequency arise MPTs. Stagger angle differences as small as 0.1 can give rise to significant MPT. It is also noted that MPT noise is more pronounced when the fan is operating in an unstarted mode. Computational results using a three-dimensional flow solver to compute the complete annulus flow with non-uniform fans indicate that MPT noise can be estimated in a relatively simple way. Hence, once the effect of a typical geometry variation of one blade in an otherwise uniform blade row is known, the effect of all the blades being different can be quickly computed via superposition. Two computer programs that were developed as part of this work are used in conjunction with a user s computational fluid dynamics (CFD) code to predict MPT spectra for a fan with a specified set of geometric variations: (1) The first program ROTBLD reads the users CFD solution files for a single blade passage via an API (Application Program Interface). There are options to replicate and perturb the geometry with typical variations stagger, camber, thickness, and pitch. The multi-passage CFD solution files are then written in the user s file format using the API. (2) The second program SUPERPOSE requires two input files: the first is the circumferential upstream pressure distribution extracted from the CFD solution on the multi-passage mesh

  8. Agenda toward the development of a rational noise descriptor system relevant to human annoyance by en route aircraft noise

    NASA Technical Reports Server (NTRS)

    Garbell, Maurice A.

    1990-01-01

    A rational, internationally consistent, noise descriptor system is needed to express existing and predicted en route aircraft noise levels in terms closely correlated to the annoyance perceived by people and physiologically identifiable in people, to provide guidance for aircraft and powerplant design, flight management, land-use planning, and building codes. Expanding on previous discussions, a new comprehensive statement of the specific questions that must be resolved by needed research, and the nature and quality of proof that must be adduced to justify further steps toward the drafting and adoption of new international en route aircraft-noise standards is sought. The single noise-descriptor system envisioned must be valid for widely varying aircraft-noise frequency spectra, including time-variant components and agreeable and disagreeable discrete tones and combinations of tones. The measures and criteria established by the system must be valid at high and low immission levels, at high and low ambient noise levels, for great and small number of noise events, and outdoors and indoors.

  9. Saliva Cortisol and Exposure to Aircraft Noise in Six European Countries

    PubMed Central

    Selander, Jenny; Bluhm, Gösta; Theorell, Töres; Pershagen, Göran; Babisch, Wolfgang; Seiffert, Ingeburg; Houthuijs, Danny; Breugelmans, Oscar; Vigna-Taglianti, Federica; Antoniotti, Maria Chiara; Velonakis, Emmanuel; Davou, Elli; Dudley, Marie-Louise; Järup, Lars

    2009-01-01

    Background Several studies show an association between exposure to aircraft or road traffic noise and cardiovascular effects, which may be mediated by a noise-induced release of stress hormones. Objective Our objective was to assess saliva cortisol concentration in relation to exposure to aircraft noise. Method A multicenter cross-sectional study, HYENA (Hypertension and Exposure to Noise near Airports), comprising 4,861 persons was carried out in six European countries. In a subgroup of 439 study participants, selected to enhance the contrast in exposure to aircraft noise, saliva cortisol was assessed three times (morning, lunch, and evening) during 1 day. Results We observed an elevation of 6.07 nmol/L [95% confidence interval (CI), 2.32–9.81 nmol/L] in morning saliva cortisol level in women exposed to aircraft noise at an average 24-hr sound level (LAeq,24h) > 60 dB, compared with women exposed to LAeq,24h ≤ 50 dB, corresponding to an increase of 34%. Employment status appeared to modify the response. We found no association between noise exposure and saliva cortisol levels in men. Conclusions Our results suggest that exposure to aircraft noise increases morning saliva cortisol levels in women, which could be of relevance for noise-related cardiovascular effects. PMID:20049122

  10. Interior noise control prediction study for high-speed propeller-driven aircraft

    NASA Technical Reports Server (NTRS)

    Rennison, D. C.; Wilby, J. F.; Marsh, A. H.; Wilby, E. G.

    1979-01-01

    An analytical model was developed to predict the noise levels inside propeller-driven aircraft during cruise at M = 0.8. The model was applied to three study aircraft with fuselages of different size (wide body, narrow body and small diameter) in order to determine the noise reductions required to achieve the goal of an A-weighted sound level which does not exceed 80 dB. The model was then used to determine noise control methods which could achieve the required noise reductions. Two classes of noise control treatments were investigated: add-on treatments which can be added to existing structures, and advanced concepts which would require changes to the fuselage primary structure. Only one treatment, a double wall with limp panel, provided the required noise reductions. Weight penalties associated with the treatment were estimated for the three study aircraft.

  11. A new diagnostic method for separating airborne and structureborne noise radiated by plates with applications for propeller driven aircraft

    NASA Technical Reports Server (NTRS)

    Mcgary, Michael C.

    1988-01-01

    The anticipated application of advanced turboprop propulsion systems is expected to increase the interior noise of future aircraft to unacceptably high levels. The absence of technically and economically feasible noise source-path diagnostic tools has been a prime obstacle in the development of efficient noise control treatments for propeller-driven aircraft. A new diagnostic method that permits the separation and prediction of the fully coherent airborne and structureborne components of the sound radiated by plates or thin shells has been developed. Analytical and experimental studies of the proposed method were performed on an aluminum plate. The results of the study indicate that the proposed method could be used in flight, and has fewer encumbrances than the other diagnostic tools currently available.

  12. Advanced turboprop aircraft noise annoyance - A review of recent NASA research

    NASA Technical Reports Server (NTRS)

    Mccurdy, D. A.; Leatherwood, J. D.; Shepherd, K. P.

    1986-01-01

    Passenger and community response to advanced turboprop aircraft noise are studied. Four experiments were conducted utilizing an aircraft noise synthesis system, an exterior effects room, an anechoic listening room, and a Space Station/aircraft acoustic apparatus; the experimental conditions and procedures for the psychoacoustic studies are described. The community noise studies involved evaluating the effects of various tonal characteristics on annoyance. It was observed that the frequency envelope shape did not effect annoyance; however, the interaction of the fundamental frequency with tone-to-broadband noise ratio did have a large effect on annoyance. The effects of low frequency tones, turbulent boundary layer noise, and tonal beats on passenger annoyance are investigated. The data reveal that passenger annoyance is greater for a given level of boundary layer noise when tones are at levels sufficient to increase the overall sound pressure level within the cabin. The annoyance response of an advanced turboprop and a conventional aircraft are compared. It is determined that the flyover noise level for the turboprop aircraft is not more annoying than that of a conventional aircraft.

  13. Progress of Aircraft System Noise Assessment with Uncertainty Quantification for the Environmentally Responsible Aviation Project

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H.; Burley, Casey L.; Guo, Yueping

    2016-01-01

    Aircraft system noise predictions have been performed for NASA modeled hybrid wing body aircraft advanced concepts with 2025 entry-into-service technology assumptions. The system noise predictions developed over a period from 2009 to 2016 as a result of improved modeling of the aircraft concepts, design changes, technology development, flight path modeling, and the use of extensive integrated system level experimental data. In addition, the system noise prediction models and process have been improved in many ways. An additional process is developed here for quantifying the uncertainty with a 95% confidence level. This uncertainty applies only to the aircraft system noise prediction process. For three points in time during this period, the vehicle designs, technologies, and noise prediction process are documented. For each of the three predictions, and with the information available at each of those points in time, the uncertainty is quantified using the direct Monte Carlo method with 10,000 simulations. For the prediction of cumulative noise of an advanced aircraft at the conceptual level of design, the total uncertainty band has been reduced from 12.2 to 9.6 EPNL dB. A value of 3.6 EPNL dB is proposed as the lower limit of uncertainty possible for the cumulative system noise prediction of an advanced aircraft concept.

  14. Aeroacoustic sources of motorcycle helmet noise.

    PubMed

    Kennedy, J; Adetifa, O; Carley, M; Holt, N; Walker, I

    2011-09-01

    The prevalence of noise in the riding of motorcycles has been a source of concern to both riders and researchers in recent times. Detailed flow field information will allow insight into the flow mechanisms responsible for the production of sound within motorcycle helmets. Flow field surveys of this nature are not found in the available literature which has tended to focus on sound pressure levels at ear as these are of interest for noise exposure legislation. A detailed flow survey of a commercial motorcycle helmet has been carried out in combination with surface pressure measurements and at ear acoustics. Three potential noise source regions are investigated, namely, the helmet wake, the surface boundary layer and the cavity under the helmet at the chin bar. Extensive information is provided on the structure of the helmet wake including its frequency content. While the wake and boundary layer flows showed negligible contributions to at-ear sound the cavity region around the chin bar was identified as a key noise source. The contribution of the cavity region was investigated as a function of flow speed and helmet angle both of which are shown to be key factors governing the sound produced by this region.

  15. An introduction to high speed aircraft noise prediction

    NASA Technical Reports Server (NTRS)

    Wilson, Mark R.

    1992-01-01

    The Aircraft Noise Prediction Program's High Speed Research prediction system (ANOPP-HSR) is introduced. This mini-manual is an introduction which gives a brief overview of the ANOPP system and the components of the HSR prediction method. ANOPP information resources are given. Twelve of the most common ANOPP-HSR control statements are described. Each control statement's purpose and format are stated and relevant examples are provided. More detailed examples of the use of the control statements are presented in the manual along with ten ANOPP-HSR templates. The purpose of the templates is to provide the user with working ANOPP-HSR programs which can be modified to serve particular prediction requirements. Also included in this manual is a brief discussion of common errors and how to solve these problems. The appendices include the following useful information: a summary of all ANOPP-HSR functional research modules, a data unit directory, a discussion of one of the more complex control statements, and input data unit and table examples.

  16. Effects of changed aircraft noise exposure on experiential qualities of outdoor recreational areas.

    PubMed

    Krog, Norun Hjertager; Engdahl, Bo; Tambs, Kristian

    2010-10-01

    The literature indicates that sound and visual stimuli interact in the impression of landscapes. This paper examines the relationship between annoyance with sound from aircraft and annoyance with other area problems (e.g., careless bicycle riding, crowding, etc.), and how changes in noise exposure influence the perceived overall recreational quality of outdoor recreational areas. A panel study (telephone interviews) conducted before and after the relocation of Norway's main airport in 1998 examined effects of decreased or increased noise exposure in nearby recreational areas (n = 591/455). Sound from aircraft annoyed the largest proportion of recreationists, except near the old airport after the change. The decrease in annoyance with sound from aircraft was accompanied by significant decreases in annoyance with most of the other area problems. Near the new airport annoyance with most factors beside sound from aircraft increased slightly, but not significantly. A relationship between aircraft noise annoyance and perceived overall recreational quality of the areas was found.

  17. Embedded Acoustic Sensor Array for Engine Fan Noise Source Diagnostic Test: Feasibility of Noise Telemetry via Wireless Smart Sensors

    NASA Technical Reports Server (NTRS)

    Zaman, Afroz; Bauch, Matthew; Raible, Daniel

    2011-01-01

    Aircraft engines have evolved into a highly complex system to meet ever-increasing demands. The evolution of engine technologies has primarily been driven by fuel efficiency, reliability, as well as engine noise concerns. One of the sources of engine noise is pressure fluctuations that are induced on the stator vanes. These local pressure fluctuations, once produced, propagate and coalesce with the pressure waves originating elsewhere on the stator to form a spinning pressure pattern. Depending on the duct geometry, air flow, and frequency of fluctuations, these spinning pressure patterns are self-sustaining and result in noise which eventually radiate to the far-field from engine. To investigate the nature of vane pressure fluctuations and the resulting engine noise, unsteady pressure signatures from an array of embedded acoustic sensors are recorded as a part of vane noise source diagnostics. Output time signatures from these sensors are routed to a control and data processing station adding complexity to the system and cable loss to the measured signal. "Smart" wireless sensors have data processing capability at the sensor locations which further increases the potential of wireless sensors. Smart sensors can process measured data locally and transmit only the important information through wireless communication. The aim of this wireless noise telemetry task was to demonstrate a single acoustic sensor wireless link for unsteady pressure measurement, and thus, establish the feasibility of distributed smart sensors scheme for aircraft engine vane surface unsteady pressure data transmission and characterization.

  18. Full-Scale Turbofan Engine Noise-Source Separation Using a Four-Signal Method

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Arechiga, Rene O.

    2016-01-01

    Contributions from the combustor to the overall propulsion noise of civilian transport aircraft are starting to become important due to turbofan design trends and expected advances in mitigation of other noise sources. During on-ground, static-engine acoustic tests, combustor noise is generally sub-dominant to other engine noise sources because of the absence of in-flight effects. Consequently, noise-source separation techniques are needed to extract combustor-noise information from the total noise signature in order to further progress. A novel four-signal source-separation method is applied to data from a static, full-scale engine test and compared to previous methods. The new method is, in a sense, a combination of two- and three-signal techniques and represents an attempt to alleviate some of the weaknesses of each of those approaches. This work is supported by the NASA Advanced Air Vehicles Program, Advanced Air Transport Technology Project, Aircraft Noise Reduction Subproject and the NASA Glenn Faculty Fellowship Program.

  19. Children's cognition and aircraft noise exposure at home--the West London Schools Study.

    PubMed

    Matsui, T; Stansfeld, S; Haines, M; Head, J

    2004-01-01

    The association of aircraft noise exposure with cognitive performance was examined by means of a cross-sectional field survey. Two hundred thirty six children attending 10 primary schools around Heathrow Airport in west London were tested on reading comprehension, immediate/delayed recall and sustained attention. In order to obtain the information about their background, a questionnaire was delivered to the parents and 163 answers were collected. Logistic regression models were used to assess performance on the cognitive tests in relation to aircraft noise exposure at home and possible individual and school level confounding factors. A significant dose-response relationship was found between aircraft noise exposure at home and performance on memory tests of immediate/delayed recall. However there was no strong association with the other cognitive outcomes. These results suggest that aircraft noise exposure at home may affect children's memory.

  20. Evaluation of the disturbance caused by aircraft noise by opinion surveys

    NASA Technical Reports Server (NTRS)

    Bremond, J.

    1981-01-01

    A survey on the disturbance caused by aircraft noise was evaluated. The use of a questionnaire as a scale rather than considering isolated question responses is seen as more objective. A standardized structure for questionnaires of the opinion surveys on aircraft noise, which includes a set of questions permitting the analysis of the disturbance caused by different daily activities is recommended. The statistical processing of the answers, to achieve the most reliable evaluation of disturbance felt are discussed.

  1. Comparison of flight and wind tunnel measurements of jet noise for the XV-5B aircraft

    NASA Technical Reports Server (NTRS)

    Atencio, A., Jr.; Kirk, J. V.; Soderman, P. T.; Hall, L. P.

    1972-01-01

    Wind tunnel tests to determine noise data from scale model research aircraft are discussed. Comparisons are made between data obtained in wind tunnels and results of full scale flight tests. The acoustic measurements for the XV-5B V/STOL fan research aircraft are presented.

  2. Supersonic and Subsonic Aircraft Noise Effects on Animals: A Literature Survey.

    DTIC Science & Technology

    1986-12-01

    overflights (95-138 dB). Rylander also observed solitary birds ( Grey Plovers, oystercatchers, and ruffs) displaying a variety of behaviors during...in Alaska, Klein noted that Grissly Bears reacted very strongly to aircraft noise, while moose and wolves reacted much less than Caribou to aircraft

  3. Determination and Applications of Environmental Costs at Different Sized Airports: Aircraft Noise and Engine Emissions

    NASA Technical Reports Server (NTRS)

    Lu, Cherie; Lierens, Abigail

    2003-01-01

    With the increasing trend of charging for externalities and the aim of encouraging the sustainable development of the air transport industry, there is a need to evaluate the social costs of these undesirable side effects, mainly aircraft noise and engine emissions, for different airports. The aircraft noise and engine emissions social costs are calculated in monetary terms for five different airports, ranging from hub airports to small regional airports. The number of residences within different levels of airport noise contours and the aircraft noise classifications are the main determinants for accessing aircraft noise social costs. Whist, based on the damages of different engine pollutants on the human health, vegetation, materials, aquatic ecosystem and climate, the aircraft engine emissions social costs vary from engine types to aircraft categories. The results indicate that the relationship appears to be curvilinear between environmental costs and the traffic volume of an airport. The results and methodology of environmental cost calculation could input for to the proposed European wide harmonized noise charges as well as the social cost benefit analysis of airports.

  4. Aircraft Engine Noise Research and Testing at the NASA Glenn Research Center

    NASA Technical Reports Server (NTRS)

    Elliott, Dave

    2015-01-01

    The presentation will begin with a brief introduction to the NASA Glenn Research Center as well as an overview of how aircraft engine noise research fits within the organization. Some of the NASA programs and projects with noise content will be covered along with the associated goals of aircraft noise reduction. Topics covered within the noise research being presented will include noise prediction versus experimental results, along with engine fan, jet, and core noise. Details of the acoustic research conducted at NASA Glenn will include the test facilities available, recent test hardware, and data acquisition and analysis methods. Lastly some of the actual noise reduction methods investigated along with their results will be shown.

  5. Aircraft Engine Exhaust Nozzle System for Jet Noise Reduction

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H. (Inventor); Czech, Michael J. (Inventor); Elkoby, Ronen (Inventor)

    2014-01-01

    The aircraft exhaust engine nozzle system includes a fan nozzle to receive a fan flow from a fan disposed adjacent to an engine disposed above an airframe surface of the aircraft, a core nozzle disposed within the fan nozzle and receiving an engine core flow, and a pylon structure connected to the core nozzle and structurally attached with the airframe surface to secure the engine to the aircraft.

  6. Aircraft noise exposure affects rat behavior, plasma norepinephrine levels, and cell morphology of the temporal lobe.

    PubMed

    Di, Guo-Qing; Zhou, Bing; Li, Zheng-Guang; Lin, Qi-Li

    2011-12-01

    In order to investigate the physiological effects of airport noise exposure on organisms, in this study, we exposed Sprague-Dawley rats in soundproof chambers to previously recorded aircraft-related noise for 65 d. For comparison, we also used unexposed control rats. Noise was arranged according to aircraft flight schedules and was adjusted to its weighted equivalent continuous perceived noise levels (L(WECPN)) of 75 and 80 dB for the two experimental groups. We examined rat behaviors through an open field test and measured the concentrations of plasma norepinephrine (NE) by high performance liquid chromatography-fluorimetric detection (HPLC-FLD). We also examined the morphologies of neurons and synapses in the temporal lobe by transmission electron microscopy (TEM). Our results showed that rats exposed to airport noise of 80 dB had significantly lower line crossing number (P<0.05) and significantly longer center area duration (P<0.05) than control animals. After 29 d of airport noise exposure, the concentration of plasma NE of exposed rats was significantly higher than that of the control group (P<0.05). We also determined that the neuron and synapsis of the temporal lobe of rats showed signs of damage after aircraft noise of 80 dB exposure for 65 d. In conclusion, exposing rats to long-term aircraft noise affects their behaviors, plasma NE levels, and cell morphology of the temporal lobe.

  7. Aircraft noise exposure affects rat behavior, plasma norepinephrine levels, and cell morphology of the temporal lobe*

    PubMed Central

    Di, Guo-qing; Zhou, Bing; Li, Zheng-guang; Lin, Qi-li

    2011-01-01

    In order to investigate the physiological effects of airport noise exposure on organisms, in this study, we exposed Sprague-Dawley rats in soundproof chambers to previously recorded aircraft-related noise for 65 d. For comparison, we also used unexposed control rats. Noise was arranged according to aircraft flight schedules and was adjusted to its weighted equivalent continuous perceived noise levels (L WECPN) of 75 and 80 dB for the two experimental groups. We examined rat behaviors through an open field test and measured the concentrations of plasma norepinephrine (NE) by high performance liquid chromatography-fluorimetric detection (HPLC-FLD). We also examined the morphologies of neurons and synapses in the temporal lobe by transmission electron microscopy (TEM). Our results showed that rats exposed to airport noise of 80 dB had significantly lower line crossing number (P<0.05) and significantly longer center area duration (P<0.05) than control animals. After 29 d of airport noise exposure, the concentration of plasma NE of exposed rats was significantly higher than that of the control group (P<0.05). We also determined that the neuron and synapsis of the temporal lobe of rats showed signs of damage after aircraft noise of 80 dB exposure for 65 d. In conclusion, exposing rats to long-term aircraft noise affects their behaviors, plasma NE levels, and cell morphology of the temporal lobe. PMID:22135145

  8. Optimum Noise Reduction Methods for the Interior of Vehicles and Aircraft Cabins

    NASA Astrophysics Data System (ADS)

    Tavossi, Ph. D., Hasson M.

    The most effective methods of noise reduction in vehicles and Aircraft cabins are investigated. The first goal is to determine the optimal means of noise mitigation without change in external shape of the vehicle, or aircraft cabin exterior such as jet engine or fuselage design, with no significant added weight. The second goal is to arrive at interior designs that can be retrofitted to the existing interiors, to reduce overall noise level for the passengers. The physical phenomena considered are; relaxation oscillations, forced vibrations with non-linear damping and sub-harmonic resonances. The negative and positive damping coefficients and active noise cancelations methods are discussed. From noise power-spectrum for a prototype experimental setup, the most energetic vibration modes are determined, that require the highest damping. The proposed technique will utilize the arrangement of uniformly distributed open Helmholtz resonators, with sound absorbing surface. They are tuned to the frequencies that correspond to the most energetic noise levels. The resonators dissipate noise energy inside the vehicle, or aircraft cabin, at the peak frequencies of the noise spectrum, determined for different vehicle or aircraft cabin, interior design models.

  9. Aircraft noise effects on sleep: application of the results of a large polysomnographic field study.

    PubMed

    Basner, Mathias; Samel, Alexander; Isermann, Ullrich

    2006-05-01

    The Institute of Aerospace Medicine at the German Aerospace Center (DLR) investigated the influence of nocturnal aircraft noise on sleep in polysomnographic laboratory and field studies between 1999 and 2004. The results of the field studies were used by the Regional Council of Leipzig (Germany) for the establishment of a noise protection plan in the official approval process for the expansion of Leipzig/Halle airport. Methods and results of the DLR field study are described in detail. Special attention is given to the dose-response relationship between the maximum sound pressure level of an aircraft noise event and the probability to wake up, which was used to establish noise protection zones directly related to the effects of noise on sleep. These protection zones differ qualitatively and quantitatively from zones that are solely based on acoustical criteria. The noise protection plan for Leipzig/Halle airport is presented and substantiated: (1) on average, there should be less than one additional awakening induced by aircraft noise, (2) awakenings recalled in the morning should be avoided as much as possible, and (3) aircraft noise should interfere as little as possible with the process of falling asleep again. Issues concerned with the representativeness of the study sample are discussed.

  10. Validation of Aircraft Noise Prediction Models at Low Levels of Exposure

    NASA Technical Reports Server (NTRS)

    Page, Juliet A.; Hobbs, Christopher M.; Plotkin, Kenneth J.; Stusnick, Eric; Shepherd, Kevin P. (Technical Monitor)

    2000-01-01

    Aircraft noise measurements were made at Denver International Airport for a period of four weeks. Detailed operational information was provided by airline operators which enabled noise levels to be predicted using the FAA's Integrated Noise Model. Several thrust prediction techniques were evaluated. Measured sound exposure levels for departure operations were found to be 4 to 10 dB higher than predicted, depending on the thrust prediction technique employed. Differences between measured and predicted levels are shown to be related to atmospheric conditions present at the aircraft altitude.

  11. Effects of aircraft noise and sonic booms on domestic animals and wildlife: bibliographic abstracts

    USGS Publications Warehouse

    Gladwin, Douglas N.; Manci, Karen M.; Villella, Rita

    1988-01-01

    The purpose of this document is to provide an information base on the effects of aircraft noise and sonic booms on various animal species. Such information is necessary to assess potential impacts to wildlife populations from proposed military and other flight operations. To develop this document the National Ecology Center conducted a literature search of information pertaining to animals and wildlife. Information concerning other types of noise was also gathered to supplement the lack of knowledge on the effects of aircraft noise. The bibliographic abstracts in this report provide a compilation of current knowledge. No attempt was made to evaluate the appropriateness or adequacy of the scientific approach of each study.

  12. Noise control prediction for high-speed, propeller-driven aircraft

    NASA Technical Reports Server (NTRS)

    Wilby, J. F.; Rennison, D. C.; Wilby, E. G.; Marsh, A. H.

    1980-01-01

    An analytical study is described which explores add-on treatments and advanced concepts for the reduction of noise levels in three high-speed aircraft driven by propellers. Noise reductions of 25 to 28 dB are required to achieve a goal of an A-weighted sound level not greater than 80 dB. It is found that only a double-wall system, with a limp inner wall or trim panel, can achieve the required noise reductions. Weight penalties are estimated for the double-wall treatments. These penalties are 0.75% to 1.51% of the aircraft takeoff weight for the particular baseline designs selected.

  13. Analysis of interior noise ground and flight test data for advanced turboprop aircraft applications

    NASA Technical Reports Server (NTRS)

    Simpson, M. A.; Tran, B. N.

    1991-01-01

    Interior noise ground tests conducted on a DC-9 aircraft test section are described. The objectives were to study ground test and analysis techniques for evaluating the effectiveness of interior noise control treatments for advanced turboprop aircraft, and to study the sensitivity of the ground test results to changes in various test conditions. Noise and vibration measurements were conducted under simulated advanced turboprop excitation, for two interior noise control treatment configurations. These ground measurement results were compared with results of earlier UHB (Ultra High Bypass) Demonstrator flight tests with comparable interior treatment configurations. The Demonstrator is an MD-80 test aircraft with the left JT8D engine replaced with a prototype UHB advanced turboprop engine.

  14. A review and update of the NASA aircraft noise prediction program propeller analysis system

    NASA Technical Reports Server (NTRS)

    Golub, Robert A.; Nguyen, L. Cathy

    1989-01-01

    The National Aeronautics and Space Administration (NASA) Aircraft Noise Prediction Program (ANOPP) Propeller Analysis System (PAS) is a set of computational modules for predicting the aerodynamics, performance, and noise of propellers. The ANOPP PAS has the capability to predict noise levels for propeller aircraft certification and produce parametric scaling laws for the adjustment of measured data to reference conditions. A technical overview of the prediction techniques incorporated into the system is presented. The prediction system has been applied to predict the noise signature of a variety of propeller configurations including the effects of propeller angle of attack. A summary of these validation studies is discussed with emphasis being placed on the wind tunnel and flight test programs sponsored by the Federal Aviation Administration (FAA) for the Piper Cherokee Lance aircraft. A number of modifications and improvements have been made to the system and both DEC VAX and IBM-PC versions of the system have been added to the original CDC NOS version.

  15. Ground effects on aircraft noise. [near grazing incidence

    NASA Technical Reports Server (NTRS)

    Willshire, W. L., Jr.; Hilton, D. A.

    1979-01-01

    A flight experiment was conducted to investigate air-to-ground propagation of sound near grazing incidence. A turbojet-powered aircraft was flown at low altitudes over the ends of two microphone arrays. An eight-microphone array was positioned along a 1850 m concrete runway. The second array consisted of 12 microphones positioned parallel to the runway over grass. Twenty-eight flights were flown at altitudes ranging from 10 m to 160 m. The acoustic data recorded in the field reduced to one-third-octave band spectra and time correlated with the flight and weather information. A small portion of the data was further reduced to values of ground attenuation as a function of frequency and incidence angle by two different methods. In both methods, the acoustic signals compared originated from identical sources. Attenuation results obtained by using the two methods were in general agreement. The measured ground attenuation was largest in the frequency range of 200 to 400 Hz. A strong dependence was found between ground attenuation and incidence angle with little attenuation measured for angles of incidence greater than 10 to 15 degrees.

  16. The fallacy of using NII in analyzing aircraft operations. [Noise Impact Index

    NASA Technical Reports Server (NTRS)

    Melton, R. G.; Jacobson, I. D.

    1984-01-01

    Three measures of noise annoyance (Noise Impact Index, Level-Weighted Population, and Annoyed Population Number) are compared, regarding their utility in assessing noise reduction schemes for aircraft operations. While NII is intended to measure the average annoyance per person in a community, it is found that the method of averaging can lead to erroneous conclusions, particularly if the population does not have uniform spatial distribution. Level-Weighted Population and Annoyed Population Number are shown to be better indicators of noise annoyance when rating different strategies for noise reduction in a given community.

  17. How Common are Noise Sources on the Crash Arc of Malaysian Flight 370

    SciTech Connect

    Fenimore, Edward E.; Kunkle, Thomas David; Stead, Richard J.

    2014-10-21

    Malaysian Flight 370 disappeared nearly without a trace. Besides some communication handshakes to the INMASAT satellite, the Comprehensive Test Ban Treaty monitoring system could have heard the aircraft crash into the southern Indian Ocean. One noise event from Cape Leeuwin has been suggested by Stead as the crash and occurs within the crash location suggested by Kunkle at el. We analyze the hydrophone data from Cape Leeuwin to understand how common such noise events are on the arc of possible locations where Malaysian Flight 370 might have crashed. Few other noise sources were found on the arc. The noise event found by Stead is the strongest. No noise events are seen within the Australian Transportation Safety Board (ATSB) new search location until the 10th strongest event, an event which is very close to the noise level.

  18. Noise Certification Predictions for FJX-2-Powered Aircraft Using Analytic Methods

    NASA Technical Reports Server (NTRS)

    Berton, Jeffrey J.

    1999-01-01

    Williams International Co. is currently developing the 700-pound thrust class FJX-2 turbofan engine for the general Aviation Propulsion Program's Turbine Engine Element. As part of the 1996 NASA-Williams cooperative working agreement, NASA agreed to analytically calculate the noise certification levels of the FJX-2-powered V-Jet II test bed aircraft. Although the V-Jet II is a demonstration aircraft that is unlikely to be produced and certified, the noise results presented here may be considered to be representative of the noise levels of small, general aviation jet aircraft that the FJX-2 would power. A single engine variant of the V-Jet II, the V-Jet I concept airplane, is also considered. Reported in this paper are the analytically predicted FJX-2/V-Jet noise levels appropriate for Federal Aviation Regulation certification. Also reported are FJX-2/V-Jet noise levels using noise metrics appropriate for the propeller-driven aircraft that will be its major market competition, as well as a sensitivity analysis of the certification noise levels to major system uncertainties.

  19. USAF Bioenvironmental Noise Data Handbook. Volume 123. F-100D Aircraft, Near and Far-Field Noise.

    DTIC Science & Technology

    1979-08-01

    AD-A783 934 AIR FORCE AEROSPACE MEDICAL RESEARCH LAB WRIGHT;PATT--ETC OF/ G12C USAF BIOENVIRONMENTAL NOISE DATA HANDBOOK. VOLUME 123 F- 10 A -ETC(U...AUG 79 R S POWELL UNCLASSIFIED AMRL-TR75-50-VOL- 123 NL mmmmmmmmmmu Ellllll~llEEEEE EEEuihEEE-EuiE, -EhhhE EI AMRL-TR-75-50 Volume 123 CIO: SUSAF...BIOENVIRONMENTAL NOISE DATA HANDBOOK ’ Volume 123 SF-100D Aircraft, Near and Far-Field Noise D TIC " .. MAYD AUGUST 1979 Approved for public release

  20. USAF Bioenvironmental Noise Data Handbook. Volume 124. F-104D Aircraft, Near and Far-Field Noise.

    DTIC Science & Technology

    1979-08-01

    20-22 4. A coustic Pow er Level ................................................................ 23-25 5. Overall Sound...7 AD-AB" 845 AEROSPACE MEDICAL RESEARCH LAB WRIGHT-PATTERSON AFB OH F/B 1/2 USAF IENVIRONM4ENTAL NOISE DATA HANDBOOK. VOLUME 121t. 010D A -ETClU...COVERED *0- NVIRONMENTALUOISE TA Volume 124 of a Series D FK -1𔃾D Aircraft, ear and r-Field Noise.s4 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(< S

  1. Effects of interior aircraft noise on speech intelligibility and annoyance

    NASA Technical Reports Server (NTRS)

    Pearsons, K. S.; Bennett, R. L.

    1977-01-01

    Recordings of the aircraft ambiance from ten different types of aircraft were used in conjunction with four distinct speech interference tests as stimuli to determine the effects of interior aircraft background levels and speech intelligibility on perceived annoyance in 36 subjects. Both speech intelligibility and background level significantly affected judged annoyance. However, the interaction between the two variables showed that above an 85 db background level the speech intelligibility results had a minimal effect on annoyance ratings. Below this level, people rated the background as less annoying if there was adequate speech intelligibility.

  2. Optimal guidance and control for investigating aircraft noise-impact reduction

    NASA Technical Reports Server (NTRS)

    Stewart, E. C.; Carson, T. M.

    1978-01-01

    A methodology for investigating the reduction of community noise impact is reported. This report is concerned with the development of two models to provide data: a guidance generator and an aircraft control generator suitable for various current and advanced types of aircraft. The guidance generator produces the commanded path information from inputs chosen by an operator from a graphic scope display of a land-use map of the terminal area. The guidance generator also produces smoothing at the junctions of straight-line paths.The aircraft control generator determines the optimal set of the available controls such that the aircraft will follow the commanded path. The solutions for the control functions are given and shown to be dependent on the class of aircraft to be considered, that is, whether the thrust vector is rotatable and whether the thrust vector affects the aerodynamic forces. For the class of aircraft possessing a rotatable thrust vector, the solution is redundant; this redundancy is removed by the additional condition that the noise inpact be minimized. Information from both the guidance generator and the aircraft control generator is used by the footprint program to construct the noise footprint.

  3. Annoyance and acceptability judgements of noise produced by three types of aircraft by residents living near JFK Airport

    NASA Technical Reports Server (NTRS)

    Borsky, P. N.

    1974-01-01

    A random sample of selected communities near JFK Airport were interviewed. Subsamples, with differing feelings of fear of aircraft crashes and different locations of residence were invited to participate in a laboratory experiment. The subjects were exposed to tape recordings of simulated flyovers of aircraft in approach and departure operations at nominal distances from the airport. The subjects judged the extent of noise annoyance and acceptability of the aircraft noises. Results indicate that level of noise is most significant in affecting annoyance judgements. Subjects with feelings of high fear report significantly more annoyance and less acceptability of aircraft noise than subjects with feelings of low fear.

  4. Multilevel modelling of aircraft noise on performance tests in schools around Heathrow Airport London

    PubMed Central

    Haines, M; Stansfeld, S; Head, J; Job, R

    2002-01-01

    Design: This is a cross sectional study using the National Standardised Scores (SATs) in mathematics, science, and English (11 000 scores from children aged 11 years). The analyses used multilevel modelling to determine the effects of chronic aircraft noise exposure on childrens' school performance adjusting for demographic, socioeconomic and school factors in 123 primary schools around Heathrow Airport. Schools were assigned aircraft noise exposure level from the 1994 Civil Aviation Authority aircraft noise contour maps. Setting: Primary schools. Participants: The sample were approximately 11 000 children in year 6 (approximately 11 years old) from 123 schools in the three boroughs surrounding Heathrow Airport. Main results: Chronic exposure to aircraft noise was significantly related to poorer reading and mathematics performance. After adjustment for the average socioeconomic status of the school intake (measured by percentage of pupils eligible for free school meals) these associations were no longer statistically significant. Conclusions: Chronic exposure to aircraft noise is associated with school performance in reading and mathematics in a dose-response function but this association is confounded by socioeconomic factors. PMID:11812814

  5. Prewhitening of Colored Noise Fields for Detection of Threshold Sources

    DTIC Science & Technology

    1993-11-07

    determines the noise covariance matrix, prewhitening techniques allow detection of threshold sources. The multiple signal classification ( MUSIC ...SUBJECT TERMS 1S. NUMBER OF PAGES AR Model, Colored Noise Field, Mixed Spectra Model, MUSIC , Noise Field, 52 Prewhitening, SNR, Standardized Test...EXAMPLE 2: COMPLEX AR COEFFICIENT .............................................. 5 EXAMPLE 3: MUSIC IN A COLORED BACKGROUND NOISE ...................... 6

  6. Sources of noise in magneto-optical readout

    NASA Technical Reports Server (NTRS)

    Mansuripur, M.

    1991-01-01

    The various sources of noise which are often encountered in magneto-optical readout systems are analyzed. Although the focus is on magneto-optics, most sources of noise are common among the various optical recording systems and one can easily adapt the results to other media and systems. A description of the magneto-optical readout system under consideration is given, and the standard methods and the relevant terminology of signal and noise measurement are described. The characteristics of thermal noise, which originates in the electronic circuitry of the readout system, are described. The most fundamental of all sources of noise, the shot noise, is considered, and a detailed account of its statistical properties is given. Shot noise, which is due to random fluctuations in photon arrival times, is an ever-present noise in optical detection. Since the performance of magneto-optical recording devices in use today is approaching the limit imposed by the shot noise, it is important that the reader have a good grasp of this particular source of noise. A model for the laser noise is described, and measurement results which yield numerical values for the strength of the laser power fluctuations are presented. Spatial variations of the disk reflectivity and random depolarization phenomena also contribute to the overall level of noise in readout; these and related issues are treated. Numerical simulation results describing some of the more frequently encountered sources of noise which accompany the recorded waveform itself, namely, jitter noise and signal-amplitude fluctuation noise are presented.

  7. Design of sidewall treatment of cabin noise control of a twin engine turboprop aircraft

    NASA Technical Reports Server (NTRS)

    Vaicaitis, R.; Slazak, M.

    1983-01-01

    An analytical procedure was used to predict the noise transmission into the cabin of a twin engine general aviation aircraft. This model was then used to optimize the interior A weighted noise levels to an average value of about 85 dBA. The surface pressure noise spectral levels were selected utilizing experimental flight data and empirical predictions. The add on treatments considered in this optimization study include aluminum honeycomb panels, constrained layer damping tape, porous acoustic blankets, acoustic foams, septum barriers and limp trim panels which are isolated from the vibration of the main sidewall structure. To reduce the average noise level in the cabin from about 102 kBA (baseline) to 85 dBA (optimized), the added weight of the noise control treatment is about 2% of the total gross takeoff weight of the aircraft.

  8. A Process for Assessing NASA's Capability in Aircraft Noise Prediction Technology

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.

    2008-01-01

    An acoustic assessment is being conducted by NASA that has been designed to assess the current state of the art in NASA s capability to predict aircraft related noise and to establish baselines for gauging future progress in the field. The process for determining NASA s current capabilities includes quantifying the differences between noise predictions and measurements of noise from experimental tests. The computed noise predictions are being obtained from semi-empirical, analytical, statistical, and numerical codes. In addition, errors and uncertainties are being identified and quantified both in the predictions and in the measured data to further enhance the credibility of the assessment. The content of this paper contains preliminary results, since the assessment project has not been fully completed, based on the contributions of many researchers and shows a select sample of the types of results obtained regarding the prediction of aircraft noise at both the system and component levels. The system level results are for engines and aircraft. The component level results are for fan broadband noise, for jet noise from a variety of nozzles, and for airframe noise from flaps and landing gear parts. There are also sample results for sound attenuation in lined ducts with flow and the behavior of acoustic lining in ducts.

  9. Assessing noise sources at synchrotron infrared ports

    PubMed Central

    Lerch, Ph.; Dumas, P.; Schilcher, T.; Nadji, A.; Luedeke, A.; Hubert, N.; Cassinari, L.; Boege, M.; Denard, J.-C.; Stingelin, L.; Nadolski, L.; Garvey, T.; Albert, S.; Gough, Ch.; Quack, M.; Wambach, J.; Dehler, M.; Filhol, J.-M.

    2012-01-01

    Today, the vast majority of electron storage rings delivering synchrotron radiation for general user operation offer a dedicated infrared port. There is growing interest expressed by various scientific communities to exploit the mid-IR emission in microspectroscopy, as well as the far infrared (also called THz) range for spectroscopy. Compared with a thermal (laboratory-based source), IR synchrotron radiation sources offer enhanced brilliance of about two to three orders of magnitude in the mid-IR energy range, and enhanced flux and brilliance in the far-IR energy range. Synchrotron radiation also has a unique combination of a broad wavelength band together with a well defined time structure. Thermal sources (globar, mercury filament) have excellent stability. Because the sampling rate of a typical IR Fourier-transform spectroscopy experiment is in the kHz range (depending on the bandwidth of the detector), instabilities of various origins present in synchrotron radiation sources play a crucial role. Noise recordings at two different IR ports located at the Swiss Light Source and SOLEIL (France), under conditions relevant to real experiments, are discussed. The lowest electron beam fluctuations detectable in IR spectra have been quantified and are shown to be much smaller than what is routinely recorded by beam-position monitors. PMID:22186638

  10. Comparison of advanced turboprop and conventional jet and propeller aircraft flyover noise annoyance: Preliminary results

    NASA Technical Reports Server (NTRS)

    Mccurdy, D. A.

    1985-01-01

    A laboratory experiment was conducted to compare the flyover noise annoyance of proposed advanced turboprop aircraft with that of conventional turboprop and jet aircraft. The effects of fundamental frequency and tone-to-broadband noise ratio on advanced turboprop annoyance were also examined. A computer synthesis system is used to generate 18 realistic, time varying simulations of propeller aircraft takeoff noise in which the harmonic content is systematically varied to represent the factorial combinations of six fundamental frequencies ranging from 67.5 Hz to 292.5 Hz and three tone-to-broadband noise ratios of 0, 15, and 30 dB. These advanced turboprop simulations along with recordings of five conventional turboprop takeoffs and five conventional jet takeoffs are presented at D-weighted sound pressure levels of 70, 80, and 90 dB to 32 subjects in an anechoic chamber. Analyses of the subjects' annoyance judgments compare the three categories of aircraft and examine the effects of the differences in harmonic content among the advanced turboprop noises. The annoyance prediction ability of various noise measurement procedures and corrections is also examined.

  11. Comparison of advanced turboprop and conventional jet and propeller aircraft flyover noise annoyance - Preliminary results

    NASA Technical Reports Server (NTRS)

    Mccurdy, D. A.

    1985-01-01

    A laboratory experiment was conducted to compare the flyover noise annoyance of proposed advanced turboprop aircraft with that of conventional turboprop and jet aircraft. The effects of fundamental frequency and tone-to-broadband noise ratio on advanced turboprop annoyance were also examined. A computer synthesis system was used to generate 18 realistic, time varyring simulations of propeller aircraft takeoff noise in which the harmonic content was systematically varied to represent the factorial combinations of six fundamental frequencies ranging from 67.5 Hz to 292.5 Hz and three tone-to-broadband noise ratios of 0, 15, and 30 dB. These advanced turboprop simulations along with recordings of five conventional turboprop takeoffs and five conventional jet takeoffs were presented at D-weighted sound pressure levels of 70, 80, and 90 dB to 32 subjects in an anechoic chamber. Analyses of the subjects' annoyance judgments compare the three categories of aircraft and examine the effects of the differences in harmonic content among the advanced turboprop noises. The annoyance prediction ability of various noise measurement procedures and corrections is also examined.

  12. Review of the effect of aircraft noise on sleep disturbance in adults.

    PubMed

    Perron, Stéphane; Tétreault, Louis-François; King, Norman; Plante, Céline; Smargiassi, Audrey

    2012-01-01

    Noise exposure generated by air traffic has been linked with sleep disturbances. The purpose of this systematic review is to clarify whether there is a causal link between aircraft noise exposure and sleep disturbances. Only complete, peer-reviewed articles published in scientific journals were examined. Papers published until December 2010 were considered. To be included, articles had to focus on subjects aged 18 or over and include an objective evaluation of noise levels. Studies were classified according to quality. Given the paucity of studies with comparable outcome measures, we performed a narrative synthesis using a best-evidence synthesis approach. The primary study findings were tabulated. Similarities and differences between studies were investigated. Of the 12 studies surveyed that dealt with sleep disturbances, four were considered to be of high quality, five were considered to be of moderate quality and three were considered to be of low quality. All moderate- to high-quality studies showed a link between aircraft noise events and sleep disturbances such as awakenings, decreased slow wave sleep time or the use of sleep medication. This review suggests that there is a causal relation between exposure to aircraft noise and sleep disturbances. However, the evidence comes mostly from experimental studies focusing on healthy adults. Further studies are necessary to determine the impact of aircraft noise on sleep disturbance for individuals more than 65 years old and for those with chronic diseases.

  13. A Robust Waveguide Millimeter-Wave Noise Source

    NASA Technical Reports Server (NTRS)

    Ehsan, Negar; Piepmeier, Jeffrey R.; Solly, Michael; Macmurphy, Shawn; Lucey, Jared; Wollack, Edward

    2015-01-01

    This paper presents the design, fabrication, and characterization of a millimeter-wave noise source for the 160- 210 GHz frequency range. The noise source has been implemented in an E-split-block waveguide package and the internal circuitry was developed on a quartz substrate. The measured excess noise ratio at 200 GHz is 9.6 dB.

  14. Role of structural noise in aircraft pressure cockpit from vibration action of new-generation engines

    NASA Astrophysics Data System (ADS)

    Baklanov, V. S.

    2016-07-01

    The evolution of new-generation aircraft engines is transitioning from a bypass ratio of 4-6 to an increased ratio of 8-12. This is leading to substantial broadening of the vibration spectrum of engines with a shift to the low-frequency range due to decreased rotation speed of the fan rotor, in turn requiring new solutions to decrease structural noise from engine vibrations to ensure comfort in the cockpits and cabins of aircraft.

  15. En route noise of turboprop aircraft and their acceptability: Report of tests

    NASA Technical Reports Server (NTRS)

    Held, Wolf

    1990-01-01

    The development of propfan-powered aircraft has been observed with great interest. It is obvious that during cruising flight, the aircraft powerplant (propellers) cause a noise clearly perceivable on the ground. It is the audible frequency spectrum of the propfan powerplants relative to the high tip speeds that presents the problem. A flight test was conducted on 30 April, 1989 at the Frankfurt Airport. Results of the test flight are present.

  16. Noise-Source Separation Using Internal and Far-Field Sensors for a Full-Scale Turbofan Engine

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Miles, Jeffrey H.

    2009-01-01

    Noise-source separation techniques for the extraction of the sub-dominant combustion noise from the total noise signatures obtained in static-engine tests are described. Three methods are applied to data from a static, full-scale engine test. Both 1/3-octave and narrow-band results are discussed. The results are used to assess the combustion-noise prediction capability of the Aircraft Noise Prediction Program (ANOPP). A new additional phase-angle-based discriminator for the three-signal method is also introduced.

  17. The way to decrease efficiently the noises generated by the jets of passenger aircrafts

    NASA Astrophysics Data System (ADS)

    Kuznetsov, V. M.

    2010-01-01

    The modern state of the problem of how to decrease aviation noise is examined. It is pointed out that in order to meet the tightened standards on noise for passenger aircrafts it is necessary to use efficient ways to decrease the noise generated by turbojet engines. The experimental results permitting us to decrease the noise generated by the jets are presented. The results have been obtained at the TsAGI dead chamber. The acoustic efficiency of the ways decreasing the noise generated by the jets is determined. The noise is decreased by using the nozzles with chevron cuts made in the lateral walls by varying parameters of the bypass nozzle via varying the nozzle’s disposition of primary and outer flows, by placing the ejector’s noise-suppressing nozzle and by organizing the gas “thermal-acoustical” screen near the jet exhaust.

  18. Upper surface blowing noise of the NASA-Ames quiet short-haul research aircraft

    NASA Technical Reports Server (NTRS)

    Bohn, A. J.; Shovlin, M. D.

    1980-01-01

    An experimental study of the propulsive-lift noise of the NASA-Ames quiet short-haul research aircraft (QSRA) is described. Comparisons are made of measured QSRA flyover noise and model propulsive-lift noise data available in references. Developmental tests of trailing-edge treatments were conducted using sawtooth-shaped and porous USB flap trailing-edge extensions. Small scale parametric tests were conducted to determine noise reduction/design relationships. Full-scale static tests were conducted with the QSRA preparatory to the selection of edge treatment designs for flight testing. QSRA flight and published model propulsive-lift noise data have similar characteristics. Noise reductions of 2 to 3 dB were achieved over a wide range of frequency and directivity angles in static tests of the QSRA. These noise reductions are expected to be achieved or surpassed in flight tests planned by NASA in 1980.

  19. Human noise exposure criteria for combat aircraft training areas

    NASA Astrophysics Data System (ADS)

    Lee, Robert A.; Harris, C. Stanley; Vongierke, Henning E.

    1992-04-01

    An overview of interpretive criteria for the noise exposure conditions associated with low altitude flying operations in the United States is presented. It includes description of single event and cumulative noise characteristics unique to such flying activity and a discussion of rationale for using the measure, onset rated adjusted Day-Night Average Sound Level, for predicting population annoyance.

  20. Toward Reduced Aircraft Community Noise Impact Via a Perception-Influenced Design Approach

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.

    2016-01-01

    This is an exciting time for aircraft design. New configurations, including small multi-rotor uncrewed aerial systems, fixed- and tilt-wing distributed electric propulsion aircraft, high-speed rotorcraft, hybrid-electric commercial transports, and low-boom supersonic transports, are being made possible through a host of propulsion and airframe technology developments. The resulting noise signatures may be radically different, both spectrally and temporally, than those of the current fleet. Noise certification metrics currently used in aircraft design do not necessarily reflect these characteristics and therefore may not correlate well with human response. Further, as operations and missions become less airport-centric, e.g., those associated with on-demand mobility or package delivery, vehicles may operate in closer proximity to the population than ever before. Fortunately, a new set of tools are available for assessing human perception during the design process in order to affect the final design in a positive manner. The tool chain utilizes system noise prediction methods coupled with auralization and psychoacoustic testing, making possible the inclusion of human response to noise, along with performance criteria and certification requirements, into the aircraft design process. Several case studies are considered to illustrate how this approach could be used to influence the design of future aircraft.

  1. Association of aircraft noise stress to periodontal disease in aircrew members.

    PubMed

    Haskell, B S

    1975-08-01

    A review of the literature reveals a multitude of effects that noise may contribute to periodontal disease, including cardiovascular disease, angiospasm of peripheral vessels, hypertension, and an increase in inflammatory cells with concurrent inhibition of healing. Three groups of 25 men were selected from the Pennsylvania Air National Guard for study. Group 1 consisted of F-102 jet fighter pilots; Group 2, pilots and crew of a four-engine, propeller-driven C-121 aircraft; and Group 3, enlisted men not exposed to aircraft noise, as a control. The degree of alveolar, intraceptal bone loss for each subject was measured from full-mouth radiographs of all groups. The greatest amount of bone loss occurred in crew members of propeller-driven aircraft. Jet pilots had considerably less bone loss while the average number of millimeters of bone lost per tooth revealed a difference between the three groups to the 0.01 significance level (F=24.7). The data suggests there is a degree of alveolar bone loss over a period of years associated with exposure to propeller aircraft noise and vibration, and negligible loss for jet aircraft noise.

  2. Procedure for Separating Noise Sources in Measurements of Turbofan Engine Core Noise

    NASA Technical Reports Server (NTRS)

    Miles, Jeffrey Hilton

    2006-01-01

    The study of core noise from turbofan engines has become more important as noise from other sources like the fan and jet have been reduced. A multiple microphone and acoustic source modeling method to separate correlated and uncorrelated sources has been developed. The auto and cross spectrum in the frequency range below 1000 Hz is fitted with a noise propagation model based on a source couplet consisting of a single incoherent source with a single coherent source or a source triplet consisting of a single incoherent source with two coherent point sources. Examples are presented using data from a Pratt & Whitney PW4098 turbofan engine. The method works well.

  3. Effects of sound level fluctuations on annoyance caused by aircraft-flyover noise

    NASA Technical Reports Server (NTRS)

    Mccurdy, D. A.

    1979-01-01

    A laboratory experiment was conducted to determine the effects of variations in the rate and magnitude of sound level fluctuations on the annoyance caused by aircraft-flyover noise. The effects of tonal content, noise duration, and sound pressure level on annoyance were also studied. An aircraft-noise synthesis system was used to synthesize 32 aircraft-flyover noise stimuli representing the factorial combinations of 2 tone conditions, 2 noise durations, 2 sound pressure levels, 2 level fluctuation rates, and 2 level fluctuation magnitudes. Thirty-two test subjects made annoyance judgements on a total of 64 stimuli in a subjective listening test facility simulating an outdoor acoustic environment. Variations in the rate and magnitude of level fluctuations were found to have little, if any, effect on annoyance. Tonal content, noise duration, sound pressure level, and the interaction of tonal content with sound pressure level were found to affect the judged annoyance significantly. The addition of tone corrections and/or duration corrections significantly improved the annoyance prediction ability of noise rating scales.

  4. Design and test of aircraft engine isolators for reduced interior noise

    NASA Technical Reports Server (NTRS)

    Unruh, J. F.; Scheidt, D. C.

    1982-01-01

    Improved engine vibration isolation was proposed to be the most weight and cost efficient retrofit structure-borne noise control measure for single engine general aviation aircraft. A study was carried out the objectives: (1) to develop an engine isolator design specification for reduced interior noise transmission, (2) select/design candidate isolators to meet a 15 dB noise reduction design goal, and (3) carry out a proof of concept evaluation test. Analytical model of the engine, vibration isolators and engine mount structure were coupled to an empirical model of the fuselage for noise transmission evaluation. The model was used to develop engine isolator dynamic properties design specification for reduced noise transmission. Candidate isolators ere chosen from available product literature and retrofit to a test aircraft. A laboratory based test procedure was then developed to simulate engine induced noise transmission in the aircraft for a proof of concept evaluation test. Three candidate isolator configurations were evaluated for reduced structure-borne noise transmission relative to the original equipment isolators.

  5. ANOPP programmer's reference manual for the executive System. [aircraft noise prediction program

    NASA Technical Reports Server (NTRS)

    Gillian, R. E.; Brown, C. G.; Bartlett, R. W.; Baucom, P. H.

    1977-01-01

    Documentation for the Aircraft Noise Prediction Program as of release level 01/00/00 is presented in a manual designed for programmers having a need for understanding the internal design and logical concepts of the executive system software. Emphasis is placed on providing sufficient information to modify the system for enhancements or error correction. The ANOPP executive system includes software related to operating system interface, executive control, and data base management for the Aircraft Noise Prediction Program. It is written in Fortran IV for use on CDC Cyber series of computers.

  6. Aircraft Noise Perception Study in Brazil: A Perspective on Airport Sustainable Growth and Environmental Awareness

    NASA Technical Reports Server (NTRS)

    deArantesGomesEller, Rogerio; Urbina, Ligia Maria Soto; Porto, Protogenes Pires

    2003-01-01

    Aircraft noise perception is related to several variables that are tangible and objective, such as the number of operations, flight schedules. Other variables, instead, are more subjective, such as preferences. However, although their elusiveness, they contribute to determine the individuals' perception of this type of externality. Despite the fact that the complaints related to aeronautical noise have been registered since the decade of 50, it has been observed that the perception of noise seems to have grown, especially since the 80's. It has been argued that this change in noise perception has its roots on the accelerated expansion of air traffic. But, it is necessary to point out the important role played on modeling preferences, by the growing environmental conscience and the higher welfare and quality of life standards and expectations. In that context, the main objective of this paper is to study the aeronautical noise perception in the neighborhoods of the Aeroporto Internacional de Sao Paulo - AISP (the biggest airport of South America). Specifically, it analyzes the relationship between aircraft noise perception and social class, which is expected to be positive. Since noise perception is an intangible variable, this study chose as a proxy the value losses of residential properties, caused by aeronautical noise. The variable social class has been measured utilizing average per capita income of the population who live nearby the airport. The comparison of both, the lowest and the highest social class suggests that the relationship between social class and noise perception is positive in the AISP region. Moreover, it was observed that all social classes are very susceptible to aircraft noise annoyance. In fact, the magnitude of the noise perception proxy for both social classes -the residential value losses- was found to be comparable to levels encountered in developed countries.

  7. Effect of nighttime aircraft noise exposure on endothelial function and stress hormone release in healthy adults

    PubMed Central

    Schmidt, Frank P.; Basner, Mathias; Kröger, Gunnar; Weck, Stefanie; Schnorbus, Boris; Muttray, Axel; Sariyar, Murat; Binder, Harald; Gori, Tommaso; Warnholtz, Ascan; Münzel, Thomas

    2013-01-01

    Aims Aircraft noise disturbs sleep, and long-term exposure has been shown to be associated with increases in the prevalence of hypertension and an overall increased risk for myocardial infarction. The exact mechanisms responsible for these cardiovascular effects remain unclear. Methods and results We performed a blinded field study in 75 healthy volunteers (mean age 26 years), who were exposed at home, in random order, to one control pattern (no noise) and two different noise scenarios [30 or 60 aircraft noise events per night with an average maximum sound pressure level (SPL) of 60 dB(A)] for one night each. We performed polygraphy during each study night. Noise caused a worsening in sleep quality (P < 0.0001). Noise60, corresponding to equivalent continuous SPLs of 46.3 dB (Leq) and representing environmental noise levels associated with increased cardiovascular events, caused a blunting in FMD (P = 0.016). As well, although a direct comparison among the FMD values in the noise groups (control: 10.4 ± 3.8%; Noise30: 9.7 ± 4.1%; Noise60: 9.5 ± 4.3%, P = 0.052) did not reach significance, a monotone dose-dependent effect of noise level on FMD was shown (P = 0.020). Finally, there was a priming effect of noise, i.e. the blunting in FMD was particularly evident when subjects were exposed first to 30 and then to 60 noise events (P = 0.006). Noise-induced endothelial dysfunction (ED) was reversed by the administration of Vitamin C (P = 0.0171). Morning adrenaline concentration increased from 28.3 ± 10.9 to 33.2 ± 16.6 and 34.1 ± 19.3 ng/L (P = 0.0099). Pulse transit time, reflecting arterial stiffness, was also shorter after exposure to noise (P = 0.003). Conclusion In healthy adults, acute nighttime aircraft noise exposure dose-dependently impairs endothelial function and stimulates adrenaline release. Noise-induced ED may be in part due to increased production in reactive oxygen species and may thus be one mechanism contributing to the observed association of

  8. Advanced subsonic transport approach noise: The relative contribution of airframe noise

    NASA Technical Reports Server (NTRS)

    Willshire, William L., Jr.; Garber, Donald P.

    1992-01-01

    With current engine technology, airframe noise is a contributing source for large commercial aircraft on approach, but not the major contributor. With the promise of much quieter jet engines with the planned new generation of high-by-pass turbofan engines, airframe noise has become a topic of interest in the advanced subsonic transport research program. The objective of this paper is to assess the contribution of airframe noise relative to the other aircraft noise sources on approach. The assessment will be made for a current technology large commercial transport aircraft and for an envisioned advanced technology aircraft. NASA's Aircraft Noise Prediction Program (ANOPP) will be used to make total aircraft noise predictions for these two aircraft types. Predicted noise levels and areas of noise contours will be used to determine the relative importance of the contributing approach noise sources. The actual set-up decks used to make the ANOPP runs for the two aircraft types are included in appendixes.

  9. Exposure-effect relations between aircraft and road traffic noise exposure at school and reading comprehension: the RANCH project.

    PubMed

    Clark, Charlotte; Martin, Rocio; van Kempen, Elise; Alfred, Tamuno; Head, Jenny; Davies, Hugh W; Haines, Mary M; Lopez Barrio, Isabel; Matheson, Mark; Stansfeld, Stephen A

    2006-01-01

    Transport noise is an increasingly prominent feature of the urban environment, making noise pollution an important environmental public health issue. This paper reports on the 2001-2003 RANCH project, the first cross-national epidemiologic study known to examine exposure-effect relations between aircraft and road traffic noise exposure and reading comprehension. Participants were 2,010 children aged 9-10 years from 89 schools around Amsterdam Schiphol, Madrid Barajas, and London Heathrow airports. Data from The Netherlands, Spain, and the United Kingdom were pooled and analyzed using multilevel modeling. Aircraft noise exposure at school was linearly associated with impaired reading comprehension; the association was maintained after adjustment for socioeconomic variables (beta = -0.008, p = 0.012), aircraft noise annoyance, and other cognitive abilities (episodic memory, working memory, and sustained attention). Aircraft noise exposure at home was highly correlated with aircraft noise exposure at school and demonstrated a similar linear association with impaired reading comprehension. Road traffic noise exposure at school was not associated with reading comprehension in either the absence or the presence of aircraft noise (beta = 0.003, p = 0.509; beta = 0.002, p = 0.540, respectively). Findings were consistent across the three countries, which varied with respect to a range of socioeconomic and environmental variables, thus offering robust evidence of a direct exposure-effect relation between aircraft noise and reading comprehension.

  10. Arousal from sleep by noises from aircraft with and without acoustically treated nacelles

    NASA Technical Reports Server (NTRS)

    Lukas, J. S.; Peeler, D. J.; Dobbs, M. E.

    1973-01-01

    The electroencephalographic and behavioral responses during sleep of four subjects, aged 46 to 58 years, to three types of noises were tested over 14 consecutive nights. The stimuli were two DC-8 jet landing noises (each 30 seconds in duration and coming from DC-8 aircraft with and without acoustical treatment on the engine nacelles) and a 4-second burst of pink noise. Each of the noises was tested at nominal intensities of 61 and 79 dBA. Other physical descriptors of the noises were measured or computed. The results indicate that for an equivalent degree of sleep disruption, noise form the jet aircraft with untreated nacelles must be about 6 dBA less intense than the jet with acoustically treated nacelles. Predictions of the effects of noise on sleep appear, tentatively, to attain the highest accuracy when the physical descriptor of noise intensity includes information about the impulsive characteristics of that noise as well as its long-term spectral content.

  11. Identification of Noise Sources and Design of Noise Reduction Measures for a Pneumatic Nail Gun.

    PubMed

    Jayakumar, Vignesh; Kim, Jay; Zechmann, Edward

    An experimental-analytical procedure was implemented to reduce the operating noise level of a nail gun, a commonly found power tool in a construction site. The procedure is comprised of preliminary measurements, identification and ranking of major noise sources and application of noise controls. Preliminary measurements show that the impact noise transmitted through the structure and the exhaust related noise were found to be the first and second major contributors. Applying a noise absorbing foam on the outside of the nail gun body was found to be an effective noise reduction technique. One and two-volume small mufflers were designed and applied to the exhaust side of the nail gun which reduced not only the exhaust noise but also the impact noise. It was shown that the overall noise level could be reduced by as much as 3.5 dB, suggesting that significant noise reduction is possible in construction power tools without any significant increase of the cost.

  12. Structure-borne noise control for propeller aircraft

    NASA Technical Reports Server (NTRS)

    Unruh, James F.

    1987-01-01

    A laboratory test apparatus was developed which would allow the study and development of propeller wake/vortex-induced structure-borne interior noise control measures. Various methods of wing structural modification, including blocking masses, surface damping treatments, and tuned mechanical absorbers, were evaluated relative to reduced interior noise levels. Inboard wing fuel was found to act as an effective blocking mass. Wing panel add-on damping treatment in the form of a single, constrained layer was not an effective control measure, except in the area of the propeller wake. However, highly damped, tuned mechanical absorbers were found to be the most efficient structure-borne noise (SBN) control measure.

  13. Noise of High-Performance Aircraft at Afterburner

    DTIC Science & Technology

    2015-07-11

    next progress report. Through the advocacy of Dr. John Spyropulos and the excellent cooperation of Mr. Allan Aubert, we received a set of F -18E jet...noise data for study. The principal objective of our study is to find out if the dominant noise components of the F -18E, especially at high power...setting, are the same as those of a high temperature supersonic laboratory jet. Previously, we have performed a similar study of the noise of a F -22A

  14. A Psychoacoustic Evaluation of Noise Signatures from Advanced Civil Transport Aircraft

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Christian, Andrew

    2016-01-01

    The NASA Environmentally Responsible Aviation project has been successful in developing and demonstrating technologies for integrated aircraft systems that can simultaneously meet aggressive goals for fuel burn, noise and emissions. Some of the resulting systems substantially differ from the familiar tube and wing designs constituting the current civil transport fleet. This study attempts to explore whether or not the effective perceived noise level metric used in the NASA noise goal accurately reflects human subject response across the range of vehicles considered. Further, it seeks to determine, in a quantitative manner, if the sounds associated with the advanced aircraft are more or less preferable to the reference vehicles beyond any differences revealed by the metric. These explorations are made through psychoacoustic tests in a controlled laboratory environment using simulated stimuli developed from auralizations of selected vehicles based on systems noise assessments.

  15. Aircraft noise, health, and residential sorting: evidence from two quasi-experiments.

    PubMed

    Boes, Stefan; Nüesch, Stephan; Stillman, Steven

    2013-09-01

    We explore two unexpected changes in flight regulations to estimate the causal effect of aircraft noise on health. Detailed measures of noise are linked with longitudinal data on individual health outcomes based on the exact address information. Controlling for individual heterogeneity and spatial sorting into different neighborhoods, we find that aircraft noise significantly increases sleeping problems and headaches. Models that do not control for such heterogeneity and sorting substantially underestimate the negative health effects, which suggests that individuals self-select into residence based on their unobserved sensitivity to noise. Our study demonstrates that the combination of quasi-experimental variation and panel data is very powerful for identifying causal effects in epidemiological field studies.

  16. Effects of Changed Aircraft Noise Exposure on the Use of Outdoor Recreational Areas

    PubMed Central

    Krog, Norun Hjertager; Engdahl, Bo; Tambs, Kristian

    2010-01-01

    This paper examines behavioural responses to changes in aircraft noise exposure in local outdoor recreational areas near airports. Results from a panel study conducted in conjunction with the relocation of Norway’s main airport in 1998 are presented. One recreational area was studied at each airport site. The samples (n = 1,264/1,370) were telephone interviewed about their use of the area before and after the change. Results indicate that changed aircraft noise exposure may influence individual choices to use local outdoor recreational areas, suggesting that careful considerations are needed in the planning of air routes over local outdoor recreational areas. However, considerable stability in use, and also fluctuations in use unrelated to the changes in noise conditions were found. Future studies of noise impacts should examine a broader set of coping mechanisms, like intra- and temporal displacement. Also, the role of place attachment, and the substitutability of local areas should be studied. PMID:21139867

  17. Building vibrations induced by noise from rotorcraft and propeller aircraft flyovers

    NASA Technical Reports Server (NTRS)

    Shepherd, Kevin P.; Hubbard, Harvey H.

    1992-01-01

    Noise and building vibrations were measured for a series of helicopter and propeller-driven aircraft flyovers at WFF during May 1978. The building response data are compared with similar data acquired earlier at sites near Dulles and Kennedy Airports for operation of commercial jet transports, including the Concorde supersonic transport. Results show that noise-induced vibration levels in windows and walls are directly proportional to sound pressure level and that for a given noise level, the acceleration levels induced by a helicopter or a propeller-driven aircraft flyover cannot be distinguished from the acceleration levels induced by a commercial jet transport flyover. Noise-induced building acceleration levels were found to be lower than those levels which might be expected to cause structural damage and were also lower than some acceleration levels induced by such common domestic events as closing windows and doors.

  18. Effects of changed aircraft noise exposure on the use of outdoor recreational areas.

    PubMed

    Krog, Norun Hjertager; Engdahl, Bo; Tambs, Kristian

    2010-11-01

    This paper examines behavioural responses to changes in aircraft noise exposure in local outdoor recreational areas near airports. Results from a panel study conducted in conjunction with the relocation of Norway's main airport in 1998 are presented. One recreational area was studied at each airport site. The samples (n = 1,264/1,370) were telephone interviewed about their use of the area before and after the change. Results indicate that changed aircraft noise exposure may influence individual choices to use local outdoor recreational areas, suggesting that careful considerations are needed in the planning of air routes over local outdoor recreational areas. However, considerable stability in use, and also fluctuations in use unrelated to the changes in noise conditions were found. Future studies of noise impacts should examine a broader set of coping mechanisms, like intra- and temporal displacement. Also, the role of place attachment, and the substitutability of local areas should be studied.

  19. Community reactions to aircraft noise in the vicinity of airport: A comparative study of the social surveys using interview method

    NASA Technical Reports Server (NTRS)

    Osada, Y.

    1980-01-01

    A comparative study was performed on the reports of community reactions to aircraft noise. The direct and immediate reactions to aircraft noise such as perceived noisiness, interference with conversations, etc. and various emotional influences were most remarkable; indirect and long term influences such as disturbance of mental work and physical symptoms were less remarkable.

  20. Residential exposure to aircraft noise and hospital admissions for cardiovascular diseases: multi-airport retrospective study

    PubMed Central

    Correia, Andrew W; Peters, Junenette L; Levy, Jonathan I; Melly, Steven

    2013-01-01

    Objective To investigate whether exposure to aircraft noise increases the risk of hospitalization for cardiovascular diseases in older people (≥65 years) residing near airports. Design Multi-airport retrospective study of approximately 6 million older people residing near airports in the United States. We superimposed contours of aircraft noise levels (in decibels, dB) for 89 airports for 2009 provided by the US Federal Aviation Administration on census block resolution population data to construct two exposure metrics applicable to zip code resolution health insurance data: population weighted noise within each zip code, and 90th centile of noise among populated census blocks within each zip code. Setting 2218 zip codes surrounding 89 airports in the contiguous states. Participants 6 027 363 people eligible to participate in the national medical insurance (Medicare) program (aged ≥65 years) residing near airports in 2009. Main outcome measures Percentage increase in the hospitalization admission rate for cardiovascular disease associated with a 10 dB increase in aircraft noise, for each airport and on average across airports adjusted by individual level characteristics (age, sex, race), zip code level socioeconomic status and demographics, zip code level air pollution (fine particulate matter and ozone), and roadway density. Results Averaged across all airports and using the 90th centile noise exposure metric, a zip code with 10 dB higher noise exposure had a 3.5% higher (95% confidence interval 0.2% to 7.0%) cardiovascular hospital admission rate, after controlling for covariates. Conclusions Despite limitations related to potential misclassification of exposure, we found a statistically significant association between exposure to aircraft noise and risk of hospitalization for cardiovascular diseases among older people living near airports. PMID:24103538

  1. Inflight source noise of an advanced full-scale single-rotation propeller

    NASA Technical Reports Server (NTRS)

    Woodward, Richard P.; Loeffler, Irvin J.

    1991-01-01

    Flight tests to define the far field tone source at cruise conditions were completed on the full scale SR-7L advanced turboprop which was installed on the left wing of a Gulfstream II aircraft. This program, designated Propfan Test Assessment (PTA), involved aeroacoustic testing of the propeller over a range of test conditions. These measurements defined source levels for input into long distance propagation models to predict en route noise. Inflight data were taken for 7 test cases. The sideline directivities measured by the Learjet showed expected maximum levels near 105 degrees from the propeller upstream axis. However, azimuthal directivities based on the maximum observed sideline tone levels showed highest levels below the aircraft. An investigation of the effect of propeller tip speed showed that the tone level of reduction associated with reductions in propeller tip speed is more significant in the horizontal plane than below the aircraft.

  2. Annoyance caused by advanced turboprop aircraft flyover noise: Counter-rotating-propeller configuration

    NASA Technical Reports Server (NTRS)

    Mccurdy, David A.

    1990-01-01

    Two experiments were conducted to quantify the annoyance of people to flyover noise of advanced turboprop aircraft with counter rotating propellers. The first experiment examined configurations having an equal number of blades on each rotor and the second experiment examined configurations having an unequal number of blades on each rotor. The objectives were to determine the effects on annoyance of various tonal characteristics, and to compare annoyance to advanced turboprops with annoyance to conventional turboprops and turbofans. A computer was used to synthesize realistic, time-varying simulations of advanced turboprop aircraft takeoff noise. The simulations represented different combinations fundamental frequency and tone-to-broadband noise ratio. Also included in each experiment were recordings of 10 conventional turboprop and turbofan takeoffs. Each noise was presented at three sound pressure levels in an anechoic chamber. In each experiment, 64 subjects judged the annoyance of each noise stimulus. Analyses indicated that annoyance was significantly affected by the interaction of fundamental frequency with tone-to-broadband noise ratio. No significant differences in annoyance between the advanced turboprop aircraft and the conventional turbofans were found. The use of a duration correction and a modified tone correction improved the annoyance prediction for the stimuli.

  3. A systematic rationale for defining the significance of aircraft noise impacts.

    PubMed

    Fidell, Sanford; Mestre, Vincent; Schomer, Paul; Horonjeff, Richard; Reid, Tim

    2014-09-01

    Regulatory agencies often define strict, decibel-denominated thresholds of significance of noise impacts to protect some fraction of the residential population from exposure to highly annoying noise. Definitions of the "significance" of aircraft noise impacts and recommendations of land use "compatibility," however, typically lack detailed, systematic rationales. Instead, the definitions are justified by reference to decades-old policies that were adopted without benefit of modern understandings of noise-induced annoyance, by appeals to authority, and by generic citations of non-peer reviewed documents. Although regulatory policy decisions may properly take into consideration political and economic consequences, aspects of them are amenable to logical formalization. In particular, advances in understanding of community reaction to transportation noise now permit a systematic rationale for aircraft noise regulation. The current analyses show how regulatory policy positions can be derived from two parameters: (1) the minimal percentage of the population of a nominally average community to be protected from exposure to highly annoying noise; and (2) the percentage of all communities to which this degree of protection is intended to apply. Together with a reliable dosage-response relationship, these two parameters permit quantitatively justifiable definitions of significant noise impact.

  4. Effects of Changed Aircraft Noise Exposure on Experiential Qualities of Outdoor Recreational Areas

    PubMed Central

    Krog, Norun Hjertager; Engdahl, Bo; Tambs, Kristian

    2010-01-01

    The literature indicates that sound and visual stimuli interact in the impression of landscapes. This paper examines the relationship between annoyance with sound from aircraft and annoyance with other area problems (e.g., careless bicycle riding, crowding, etc.), and how changes in noise exposure influence the perceived overall recreational quality of outdoor recreational areas. A panel study (telephone interviews) conducted before and after the relocation of Norway’s main airport in 1998 examined effects of decreased or increased noise exposure in nearby recreational areas (n = 591/455). Sound from aircraft annoyed the largest proportion of recreationists, except near the old airport after the change. The decrease in annoyance with sound from aircraft was accompanied by significant decreases in annoyance with most of the other area problems. Near the new airport annoyance with most factors beside sound from aircraft increased slightly, but not significantly. A relationship between aircraft noise annoyance and perceived overall recreational quality of the areas was found. PMID:21139858

  5. Noise-Induced Building Vibrations Caused by Concorde and Conventional Aircraft Operations at Dulles and Kennedy International Airports

    NASA Technical Reports Server (NTRS)

    Mayes, W. H.; Stephens, D. G.; Holmes, H. K.; Lewis, R. B.; Holliday, B. G.; Ward, D. W.; Deloach, R.; Cawthorn, J. M.; Finley, T. D.; Lynch, J. W.

    1978-01-01

    Outdoor and indoor noise levels resulting from aircraft flyovers and certain nonaircraft events were recorded, as were the associated vibration levels in the walls, windows, and floors at building test sites. In addition, limited subjective tests were conducted to examine the human detection and annoyance thresholds for building vibration and rattle caused by aircraft noise. Representative peak levels of aircraft noise-induced building vibrations are reported and comparisons are made with structural damage criteria and with vibration levels induced by common domestic events. In addition, results of a pilot study are reported which indicate the human detection threshold for noise-induced floor vibrations.

  6. A research program to reduce the interior noise in general aviation aircraft, index and summary

    NASA Technical Reports Server (NTRS)

    Morgan, L.; Jackson, K.; Roskam, J.

    1985-01-01

    This report is an index of the published works from NASA Grant NSG 1301, entitled A Research Program to Reduce the Interior Noise in General Aviation Aircraft. Included are a list of all published reports and papers, a compilation of test specimen characteristics, and summaries of each published work.

  7. Community reaction to aircraft noise: time-of-day penalty and tradeoff between levels of overflights.

    PubMed

    Miedema, H M; Vos, H; de Jong, R G

    2000-06-01

    A decrease in the level of sound events can compensate for an increase in the level of other events, but noise metrics assume different tradeoffs. Noise metrics also differ in the penalty applied to noise in the evening and to noise in the night, and in the definition of these periods. These two aspects of noise metrics, i.e., the tradeoff and the penalty for the nighttime (23-7h), are investigated. A general model of the relation between SELs of sound events (aircraft overflights) and noise annoyance is presented which allows for a wide range of tradeoffs and time-of-day penalties. The (tradeoff and time-of-day penalty) parameters of the model are fitted to the data from an aircraft noise study conducted around Amsterdam Airport Schiphol, which is especially suited for investigating the tradeoff and time-of-day penalties. It was found that in this study the tradeoff between the levels of events in metrics based on L(Aeq)'s, such as L(Aeq)(24 h), DNL, and DENL, is approximately correct for the prediction of noise annoyance. Furthermore, it was found that the strongest correlation with annoyance is obtained with a nighttime penalty of circa 10 dB. No suitable data were available for further tests of the tradeoff. The result with respect to the nighttime penalty was weakly further supported by the outcome of analyses of the original data from four other aircraft noise surveys (one survey conducted around British airports, and three coordinated surveys carried out around Paris Orly, Amsterdam Schiphol, and Glasgow Abbotsinch).

  8. Noise transmission through an acoustically treated and honeycomb stiffened aircraft sidewall

    NASA Astrophysics Data System (ADS)

    Grosveld, F. W.; Mixson, J. S.

    1984-10-01

    The noise transmission characteristics of test panels and acoustic treatments representative of an aircraft sidewall are experimentally investigated in the NASA Langley Research Center transmission loss apparatus. The test panels were built to represent a segment sidewall in the propeller plane of a twin-engine, turboprop light aircraft. It is shown that an advanced treatment, which uses honeycomb for structural stiffening of skin panels, has better noise transmission loss characteristics than a conventional treatment. An alternative treatment, using the concept of limp mass and vibration isolation, provides more transmission loss than the advanced treatment for the same total surface mass. Effects on transmission loss of a variety of acoustic treatment materials (acoustic blankets, septa, damping tape, and trim panels) are presented. Damping tape does not provide additional benefit when the other treatment provides a high level of damping. Window units representative of aircraft installations are shown to have low transmission loss relative to a completely treated sidewall.

  9. Active control of aircraft cabin noise and vibration using a physical model

    NASA Astrophysics Data System (ADS)

    Li, Desheng

    In this thesis, active noise and vibration control of aircraft cabins is investigated, in which aircraft cabins are modeled as a cylindrical shell with a floor partition. As the first step toward a successful control strategy, a structural acoustic coupling analysis of the investigated structure is carried out. A new method called "Radiation Efficiency Analysis of Structural Modes (REASM)", suitable for enclosures with irregular shapes, is proposed and applied in the current analysis. Then, the optimal design of control systems consisting of PZT actuators and PVDF error sensors is discussed. A novel design method for PVDF error sensors called "GA-based method" is introduced and shown to be very effective when complex structures are involved. Finally, an active control system is implemented on a scaled laboratory aircraft-cabin model. Both the simulation and experimental results show the great potential of using piezoelectric transducers in noise control and the significant performance improvement achieved through optimal design.

  10. The role of nonlinear effects in the propagation of noise from high-power jet aircraft.

    PubMed

    Gee, Kent L; Sparrow, Victor W; James, Michael M; Downing, J Micah; Hobbs, Christopher M; Gabrielson, Thomas B; Atchley, Anthony A

    2008-06-01

    To address the question of the role of nonlinear effects in the propagation of noise radiated by high-power jet aircraft, extensive measurements were made of the F-22A Raptor during static engine run-ups. Data were acquired at low-, intermediate-, and high-thrust engine settings with microphones located 23-305 m from the aircraft along several angles. Comparisons between the results of a generalized-Burgers-equation-based nonlinear propagation model and the measurements yield favorable agreement, whereas application of a linear propagation model results in spectral predictions that are much too low at high frequencies. The results and analysis show that significant nonlinear propagation effects occur for even intermediate-thrust engine conditions and at angles well away from the peak radiation angle. This suggests that these effects are likely to be common in the propagation of noise radiated by high-power aircraft.

  11. Effects of three activities on annoyance responses to recorded flyovers. [human tolerance of jet aircraft noise

    NASA Technical Reports Server (NTRS)

    Gunn, W. J.; Shepherd, W. T.; Fletcher, J. L.

    1975-01-01

    Human subjects participated in an experiment in which they were engaged in TV viewing, telephone listening, or reverie (no activity) for a 1/2-hour session. During the session, they were exposed to a series of recorded aircraft sounds at the rate of one flight every 2 minutes. At each session, four levels of flyover noise, separated by 5 db increments were presented several times in a Latin Square balanced sequence. The peak levels of the noisiest flyover in any session was fixed at 95, 90, 85, 75, or 70 db. At the end of the test session, subjects recorded their responses to the aircraft sounds, using a bipolar scale which covered the range from very pleasant to extremely annoying. Responses to aircraft noises are found to be significantly affected by the particular activity in which the subjects are engaged.

  12. Advances in automated noise data acquisition and noise source modeling for power reactors

    SciTech Connect

    Clapp, N.E. Jr.; Kryter, R.C.; Sweeney, F.J.; Renier, J.A.

    1981-01-01

    A newly expanded program, directed toward achieving a better appreciation of both the strengths and limitations of on-line, noise-based, long-term surveillance programs for nuclear reactors, is described. Initial results in the complementary experimental (acquisition and automated screening of noise signatures) and theoretical (stochastic modeling of likely noise sources) areas of investigation are given.

  13. A prediction procedure for propeller aircraft flyover noise based on empirical data

    NASA Astrophysics Data System (ADS)

    Smith, M. H.

    1981-04-01

    Forty-eight different flyover noise certification tests are analyzed using multiple linear regression methods. A prediction model is presented based on this analysis, and the results compared with the test data and two other prediction methods. The aircraft analyzed include 30 single engine aircraft, 16 twin engine piston aircraft, and two twin engine turboprops. The importance of helical tip Mach number is verified and the relationship of several other aircraft, engine, and propeller parameters is developed. The model shows good agreement with the test data and is at least as accurate as the other prediction methods. It has the advantage of being somewhat easier to use since it is in the form of a single equation.

  14. Noise optimization of the source follower of a CMOS pixel using BSIM3 noise model

    NASA Astrophysics Data System (ADS)

    Mahato, Swaraj; Meynants, Guy; Raskin, Gert; De Ridder, J.; Van Winckel, H.

    2016-07-01

    CMOS imagers are becoming increasingly popular in astronomy. A very low noise level is required to observe extremely faint targets and to get high-precision flux measurements. Although CMOS technology offers many advantages over CCDs, a major bottleneck is still the read noise. To move from an industrial CMOS sensor to one suitable for scientific applications, an improved design that optimizes the noise level is essential. Here, we study the 1/f and thermal noise performance of the source follower (SF) of a CMOS pixel in detail. We identify the relevant design parameters, and analytically study their impact on the noise level using the BSIM3v3 noise model with an enhanced model of gate capacitance. Our detailed analysis shows that the dependence of the 1/f noise on the geometrical size of the source follower is not limited to minimum channel length, compared to the classical approach to achieve the minimum 1/f noise. We derive the optimal gate dimensions (the width and the length) of the source follower that minimize the 1/f noise, and validate our results using numerical simulations. By considering the thermal noise or white noise along with 1/f noise, the total input noise of the source follower depends on the capacitor ratio CG/CFD and the drain current (Id). Here, CG is the total gate capacitance of the source follower and CFD is the total floating diffusion capacitor at the input of the source follower. We demonstrate that the optimum gate capacitance (CG) depends on the chosen bias current but ranges from CFD/3 to CFD to achieve the minimum total noise of the source follower. Numerical calculation and circuit simulation with 180nm CMOS technology are performed to validate our results.

  15. Separation of airborne and structureborne noise radiated by plates constructed of conventional and composite materials with applications for prediction of interior noise paths in propeller driven aircraft. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Mcgary, M. C.

    1986-01-01

    The anticipated application of advanced turboprop propulsion systems and use of composite materials in primary structure is expected to increase the interior noise of future aircraft to unacceptability high levels. The absence of technically and economically feasible noise source-path diagnostic tools has been a primer obstacle in the development of efficient noise control treatments for propeller driven aircraft. A new diagnostic method which permits the separation and prediction of the fully coherent airborne and structureborne components of the sound radiated by plates or thin shells has been developed. Analytical and experimental studies of the proposed method were performed on plates constructed of both conventional and composite materials. The results of the study indicate that the proposed method can be applied to a variety of aircraft materials, could be used in flight, and has fewer encumbrances than the other diagnostic tools currently available. The study has also revealed that the noise radiation of vibrating plates in the low frequency regime due to combined airborne and structureborne inputs possesses a strong synergistic nature. The large influence of the interaction between the airborne and structureborne terms has been hitherto ignored by researchers of aircraft interior noise problems.

  16. A model and plan for a longitudinal study of community response to aircraft noise

    NASA Technical Reports Server (NTRS)

    Gunn, W. J.; Patterson, H. P.; Cornog, J.; Klaus, P.; Connor, W. K.

    1975-01-01

    A new approach is discussed for the study of the effects of aircraft noise on people who live near large airports. The approach was an outgrowth of a planned study of the reactions of individuals exposed to changing aircraft noise conditions around the Dallas-Ft. Worth (DFW) regional airport. The rationale, concepts, and methods employed in the study are discussed. A critical review of major past studies traces the history of community response research in an effort to identify strengths and limitations of the various approaches and methodologies. A stress-reduction model is presented to provide a framework for studying the dynamics of human response to a changing noise environment. The development of the survey instrument is detailed, and preliminary results of pretest data are discussed.

  17. The propeller tip vortex. A possible contributor to aircraft cabin noise

    NASA Technical Reports Server (NTRS)

    Miller, B. A.; Dittmar, J. H.; Jeracki, R. J.

    1981-01-01

    Although the assumption is generally made that cabin noise levels are governed by the transmission of propeller generated noise through the fuselage sidewall, it was postulated that the propeller wake striking the wing, in particular pressure disturbances generated downstream of the propeller by the action of the propeller tip vortex, could be strong enough to excite the aircraft structure and contribute to the cabin noise level. Tests conducted to measure the strength of the propeller tip vortex support this hypothesis. It was found that the propeller tip vortex can produce a fluctuation pressure on a simulated wing surface in the wake of a propeller that exceeds by more than 15 dB the maximum direct noise that would strike the fuselage. Wing surface response to propeller tip vortex induced excitations, and the effectiveness of this response in radiating noise to the cabin interior, must be established to assess the full significance of these results.

  18. Review of Subcritical Source-Driven Noise Analysis Measurements

    SciTech Connect

    Valentine, T.E.

    1999-11-01

    Subcritical source-driven noise measurements are simultaneous Rossia and randomly pulsed neutron measurements that provide measured quantities that can be related to the subcritical neutron multiplication factor. In fact, subcritical source-driven noise measurements should be performed in lieu of Rossia measurements because of the additional information that is obtained from noise measurements such as the spectral ratio and the coherence functions. The basic understanding of source-driven noise analysis measurements can be developed from a point reactor kinetics model to demonstrate how the measured quantities relate to the subcritical neutron multiplication factor.

  19. Sources of noise in Brillouin optical time-domain analyzers

    NASA Astrophysics Data System (ADS)

    Urricelqui, Javier; Soto, Marcelo A.; Thévenaz, Luc

    2015-09-01

    This paper presents a thorough study of the different sources of noise affecting Brillouin optical time-domain analyzers (BOTDA), providing a deep insight into the understanding of the fundamental limitations of this kind of sensors. Analytical and experimental results indicate that the noise source ultimately fixing the sensor performance depends basically on the fiber length and the input pump-probe powers. Thus, while the phase-to-intensity noise conversion induced by stimulated Brillouin scattering can have a dominating effect at short distances, a combination of sources determines the noise in longrange sensing, basically dominated by probe double Rayleigh scattering.

  20. Collection and evaluation of propeller aircraft noise certification data

    NASA Astrophysics Data System (ADS)

    Ahlswede, M.; Anders, K. P.

    1981-08-01

    More than 300 individual noise certification levels were measured for propeller driven airplanes up to 5700 kg takeoff weight and for powered gliders in accordance with the rules and regulations as set forth in International Civil Aviation Organization Annex 16. Information on the airplanes, the engines and the propellers is provided as well as on the prevailing meteorological parameters and the operational parameters together with acoustic data. Of the latter, the measured A-weighted levels with their 90% confidence limit are listed, the performance correction is given and the certification level as well as the noise-limit are provided. Data are evaluated by plotting the measured A-weighted levels versus the helical blade tip Mach number.

  1. Evaluation of piezoceramic actuators for control of aircraft interior noise

    NASA Technical Reports Server (NTRS)

    Silcox, Richard J.; Lefebvre, Sylvie; Metcalf, Vern L.; Beyer, Todd B.; Fuller, Chris R.

    1992-01-01

    Results of an experiment to evaluate piezoceramic actuators as the control actuator for active control of interior noise in a large-scale fuselage model are presented. Control was demonstrated for tonal excitation using a time domain least mean squares algorithm. A maximum of four actuator channels and six error signals were used. The actuators were employed for control of noise at frequencies where interior cavity modes were the dominant response and for driven acoustic responses where a structure resonance was dominant. Global reductions of 9 to 12 dB were obtained for the cases examined. The most effective configuration of skin-mounted actuators was found to be a pure in-plane forcing function as opposed to a bending excitation. The frame-mounted actuators were found to be equally effective as the skin-mounted actuators. However, both configurations resulted in local regions of unacceptably high vibration response in the structure.

  2. Relation Between Inflammables and Ignition Sources in Aircraft Environments

    NASA Technical Reports Server (NTRS)

    Scull, Wilfred E

    1950-01-01

    A literature survey was conducted to determine the relation between aircraft ignition sources and inflammables. Available literature applicable to the problem of aircraft fire hazards is analyzed and, discussed herein. Data pertaining to the effect of many variables on ignition temperatures, minimum ignition pressures, and minimum spark-ignition energies of inflammables, quenching distances of electrode configurations, and size of openings incapable of flame propagation are presented and discussed. The ignition temperatures and the limits of inflammability of gasoline in air in different test environments, and the minimum ignition pressure and the minimum size of openings for flame propagation of gasoline - air mixtures are included. Inerting of gasoline - air mixtures is discussed.

  3. Relation between inflammables and ignition sources in aircraft environments

    NASA Technical Reports Server (NTRS)

    Scull, Wilfred E

    1951-01-01

    A literature survey was conducted to determine the relation between aircraft ignition sources and inflammables. Available literature applicable to the problem of aircraft fire hazards is analyzed and discussed. Data pertaining to the effect of many variables on ignition temperatures, minimum ignition pressures, minimum spark-ignition energies of inflammables, quenching distances of electrode configurations, and size of openings through which flame will not propagate are presented and discussed. Ignition temperatures and limits of inflammability of gasoline in air in different test environments, and the minimum ignition pressures and minimum size of opening for flame propagation in gasoline-air mixtures are included; inerting of gasoline-air mixtures is discussed.

  4. Microwave holographic imaging of aircraft with spaceborne illuminating source

    NASA Technical Reports Server (NTRS)

    Berkowitz, R. S.; Dzekov, T. A.

    1976-01-01

    The conceptual development of a method for the high angular resolution and accurate angular position estimates for the surveillance and traffic control of aircraft is considered. A target volume several hundred kilometers in diameter is illuminated by a CW microwave source located on a satellite in geosynchronous orbit. Signals are received by a large array of random, conformally located receiving elements. Each element receives the direct signal from the satellite plus signals reflected from aircraft in the illuminated volume. Coherent combination of the signals received from the individual elements permits the equivalent of holographic imaging or multiple beam formation from which the useful target data can be obtained.

  5. Commercial Aircraft Noise Definition - L1011 Tristar. Volume 1

    DTIC Science & Technology

    1974-09-01

    eat tao twaice dwtatiozws betueen the In db dwna pulntt of t$* tosvai~ rv pereied noise Ivu tit* histars e ah*~n cnii~ta~ n~ 4kcrojtonc,- %vivenr~ie a...apu ~t zmf tltittsk. tz vaw rozten *, plin 4ov-, trsv .*Lgai* ie P04Sed to �w AOý- prtht rOutt tar %=e izý4 clcttatlre tiate alaft’ the f~lwe.t jatt

  6. Aircraft Geared Architecture Reduces Fuel Cost and Noise

    NASA Technical Reports Server (NTRS)

    2015-01-01

    In an effort to increase fuel efficiency and reduce noise in commercial airplanes, NASA aeronautics teamed up with East Hartford, Connecticut-based Pratt & Whitney through a Space Act Agreement to help the company increase the efficiency of its turbofan engine. The company's new PurePower line of engines is 15 percent more fuel-efficient and up to 75 percent quieter than its competitors.

  7. Noise of High-Performance Aircraft at Afterburner

    DTIC Science & Technology

    2015-03-30

    passage of entropy waves through the nozzle of the jet. To obtain a good understanding of the noise generation processes through numerical simulation, it...development of a one-dimensional computational model capable of generating a broadband entropy wave field with a prescribed intensity and frequency...produced by the passage of entropy waves through the velocity gradients inside the nozzle of the jet. The entropy waves are hot spots created in the

  8. Noise of High-Performance Aircraft at Afterburner

    DTIC Science & Technology

    2015-10-07

    for an investigation of indirect combustion noise generation in a military styled supersonic nozzle by numerical simulation. 2. Analyze NAVAIR F ...condition. In addition, our model allows the user to specify the spectrum, S f ( ) , of temperature fluctuations at any point on the y-z plane. Thus...the model boundary condition we have developed allows one to specify single-point statistics ′T 2 and S f ( ) . Figure 2. The y-z plane

  9. Continuous-variable quantum key distribution with Gaussian source noise

    SciTech Connect

    Shen Yujie; Peng Xiang; Yang Jian; Guo Hong

    2011-05-15

    Source noise affects the security of continuous-variable quantum key distribution (CV QKD) and is difficult to analyze. We propose a model to characterize Gaussian source noise through introducing a neutral party (Fred) who induces the noise with a general unitary transformation. Without knowing Fred's exact state, we derive the security bounds for both reverse and direct reconciliations and show that the bound for reverse reconciliation is tight.

  10. Investigation of comfort related aspects of noise in an aircraft cabin simulator

    NASA Astrophysics Data System (ADS)

    Weber, Reinhard; Baumann, Ingo; Freese, Nils; Mellert, Volker

    2004-05-01

    In the frame of the multinational European project HEACE Health effects of aircraft cabin environment [www.heace.org] experiments have been carried out to investigate the effects of different environmental factors in an aircraft on performance, comfort and health of flight and cabin crew. Tests were run in aircraft cabin simulators where temperature, humidity and sound could be adjusted in a controlled manner because only limited possibility exists of systematically changing these factors in-flight. In a multi-factorial 3×3×3 design these tests simulated real flights with real cabin crew that was hired for the test and passenger. The research on passengers responses was done in cooperation with the European FACE Technology Platform (FACE Friendly aircraft cabin environment). This paper focuses on the effects of noise on the comfort on the cabin crew. It presents unexpected order effects of noise assessments and reports on the dependency of the ratings of noise and of other environmental factors on the assessed comfort. [The investigation is granted by the EU-Commission under HEACE G4RC-CT-2001-00611.

  11. Aircraft noise effects: An interdisciplinary study of the effects of aircraft noise on man. Part 1: Basic report

    NASA Technical Reports Server (NTRS)

    1980-01-01

    An area around the Munich-Riem airport was divided into 32 clusters of different noise exposure and subjects were drawn from each cluster for a social survey and for psychological, medical, and physiological testing. Extensive acoustical measurements were also carried out in each cluster. The results were then subjected to detailed statistical analysis.

  12. Noise Characterization of Supercontinuum Sources for Low Coherence Interferometry Applications

    PubMed Central

    Brown, William J.; Kim, Sanghoon; Wax, Adam

    2015-01-01

    We examine the noise properties of supercontinuum light sources when used in low coherence interferometry applications. The first application is a multiple-scattering low-coherence interferometry (ms2/LCI) system where high power and long image acquisition times are required to image deep into tissue. For this system we compare the noise characteristics of two supercontinuum sources from different suppliers. Both sources have long term drift that limits the amount of time over which signal averaging is advantageous for reducing noise. The second application is a high resolution optical coherence tomography system where broadband light is needed for high axial resolution. For this system we compare the noise performance of the two supercontinuum sources and a light source based on four superluminescent diodes (SLDs) using imaging contrast as a comparative metric. We find that the NKT SuperK has superior noise performance compared to the Fianium SC-450-4 but neither meets the performance of the SLDs. PMID:25606759

  13. Annoyance caused by advanced turboprop aircraft flyover noise: Single-rotating propeller configuration

    NASA Technical Reports Server (NTRS)

    Mccurdy, David A.

    1988-01-01

    Two experiments were conducted to quantify the annoyance of people to advanced turboprop (propfan) aircraft flyover noise. The objectives were to: (1) determine the effects on annoyance of various tonal characteristics; and (2) compare annoyance to advanced turboprops with annoyance to conventional turboprops and jets. A computer was used to produce realistic, time-varying simulations of advanced turboprop aircraft takeoff noise. In the first experiment, subjects judged the annoyance of 45 advanced turboprop noises in which the tonal content was systematically varied to represent the factorial combinations of five fundamental frequencies, three frequency envelope shapes, and three tone-to-broadband noise ratios. Each noise was presented at three sound levels. In the second experiment, 18 advanced turboprop takeoffs, 5 conventional turboprop takeoffs, and 5 conventional jet takeoffs were presented at three sound pressure levels to subjects. Analysis indicated that frequency envelope shape did not significantly affect annoyance. The interaction of fundamental frequency with tone-to-broadband noise ratio did have a large and complex effect on annoyance. The advanced turboprop stimuli were slightly less annoying than the conventional stimuli.

  14. Effects of background noise on total noise annoyance

    NASA Technical Reports Server (NTRS)

    Willshire, K. F.

    1987-01-01

    Two experiments were conducted to assess the effects of combined community noise sources on annoyance. The first experiment baseline relationships between annoyance and noise level for three community noise sources (jet aircraft flyovers, traffic and air conditioners) presented individually. Forty eight subjects evaluated the annoyance of each noise source presented at four different noise levels. Results indicated the slope of the linear relationship between annoyance and noise level for the traffic noise was significantly different from that of aircraft and of air conditioner noise, which had equal slopes. The second experiment investigated annoyance response to combined noise sources, with aircraft noise defined as the major noise source and traffic and air conditioner noise as background noise sources. Effects on annoyance of noise level differences between aircraft and background noise for three total noise levels and for both background noise sources were determined. A total of 216 subjects were required to make either total or source specific annoyance judgements, or a combination of the two, for a wide range of combined noise conditions.

  15. USAF bioenvironmental noise data handbook. Volume 168: MB-3 tester, pressurized cabin leakage, aircraft

    NASA Astrophysics Data System (ADS)

    Rau, T. H.

    1982-06-01

    The MB-3 Tester is an electric motor-driven cabin leakage tester designed to furnish pressurized air to the aircraft at controlled pressures and temperatures during ground pressurization of aircraft cockpits and pressurized compartments. This report provides measured data defining the bioacoustic environments produced by this unit operating at a normal rated/load condition. Near-field data are reported for 37 locations in a wide variety of physical and psychoacoustic measures: overall and band sound pressure levels, C-weighted and A-weighted sound levels, preferred speech interference level, perceived noise level, and limiting times for total daily exposure of personnel with and without standard Air Force ear protectors.

  16. Noise sources in laser radar systems.

    PubMed

    Letalick, D; Renhorn, I; Steinvall, O; Shapiro, J H

    1989-07-01

    To understand the fundamental limit of performance with a given laser radar system, the phase noise of a testbed laser radar has been investigated. Apart from the phase noise in the transmitter laser and the local oscillator laser, additional phase noise was introduced by vibrations caused by fans in power supplies and cooling systems. The stability of the mechanical structure of the platform was also found to be of great importance. Furthermore, a model for the signal variations from diffuse targets has been developed. This model takes into account the stray light, the speckle decorrelation, and Doppler shift due to moving targets.

  17. Assessing the environmental impacts of aircraft noise and emissions

    NASA Astrophysics Data System (ADS)

    Mahashabde, Anuja; Wolfe, Philip; Ashok, Akshay; Dorbian, Christopher; He, Qinxian; Fan, Alice; Lukachko, Stephen; Mozdzanowska, Aleksandra; Wollersheim, Christoph; Barrett, Steven R. H.; Locke, Maryalice; Waitz, Ian A.

    2011-01-01

    With the projected growth in demand for commercial aviation, many anticipate increased environmental impacts associated with noise, air quality, and climate change. Therefore, decision-makers and stakeholders are seeking policies, technologies, and operational procedures that balance environmental and economic interests. The main objective of this paper is to address shortcomings in current decision-making practices for aviation environmental policies. We review knowledge of the noise, air quality, and climate impacts of aviation, and demonstrate how including environmental impact assessment and quantifying uncertainties can enable a more comprehensive evaluation of aviation environmental policies. A comparison is presented between the cost-effectiveness analysis currently used for aviation environmental policy decision-making and an illustrative cost-benefit analysis. We focus on assessing a subset of the engine NO X emissions certification stringency options considered at the eighth meeting of the International Civil Aviation Organization’s Committee on Aviation Environmental Protection. The FAA Aviation environmental Portfolio Management Tool (APMT) is employed to conduct the policy assessments. We show that different conclusions may be drawn about the same policy options depending on whether benefits and interdependencies are estimated in terms of health and welfare impacts versus changes in NO X emissions inventories as is the typical practice. We also show that these conclusions are sensitive to a variety of modeling uncertainties. While our more comprehensive analysis makes the best policy option less clear, it represents a more accurate characterization of the scientific and economic uncertainties underlying impacts and the policy choices.

  18. Similarity spectra analysis of high-performance jet aircraft noise.

    PubMed

    Neilsen, Tracianne B; Gee, Kent L; Wall, Alan T; James, Michael M

    2013-04-01

    Noise measured in the vicinity of an F-22A Raptor has been compared to similarity spectra found previously to represent mixing noise from large-scale and fine-scale turbulent structures in laboratory-scale jet plumes. Comparisons have been made for three engine conditions using ground-based sideline microphones, which covered a large angular aperture. Even though the nozzle geometry is complex and the jet is nonideally expanded, the similarity spectra do agree with large portions of the measured spectra. Toward the sideline, the fine-scale similarity spectrum is used, while the large-scale similarity spectrum provides a good fit to the area of maximum radiation. Combinations of the two similarity spectra are shown to match the data in between those regions. Surprisingly, a combination of the two is also shown to match the data at the farthest aft angle. However, at high frequencies the degree of congruity between the similarity and the measured spectra changes with engine condition and angle. At the higher engine conditions, there is a systematically shallower measured high-frequency slope, with the largest discrepancy occurring in the regions of maximum radiation.

  19. Cumulative annoyance due to multiple aircraft flyover with differing peak noise levels

    NASA Technical Reports Server (NTRS)

    Shepherd, K. P.

    1981-01-01

    A laboratory study in which 160 subjects judged the annoyance of 30 minute sessions of aircraft noise is described. Each session contained nine flyovers consisting of various combinations of three takeoff recordings of Boeing 727. The subjects were asked to judge their annoyance in the simulated living room environment of the laboratory and also to assess how annoyed they would be if they heard the noise in their home during the day, evening, and night periods. The standard deviation of the sound level did not improve the predictive ability of L sub eq (equivalent continuous sound level) which performed as well or better than other noise measured. Differences were found between the projected home responses for the day, evening, and nighttime periods. Time of day penalties derived from these results showed reasonable agreement with those currently used in community noise indices.

  20. Acoustic Source Localization in Aircraft Interiors Using Microphone Array Technologies

    NASA Technical Reports Server (NTRS)

    Sklanka, Bernard J.; Tuss, Joel R.; Buehrle, Ralph D.; Klos, Jacob; Williams, Earl G.; Valdivia, Nicolas

    2006-01-01

    Using three microphone array configurations at two aircraft body stations on a Boeing 777-300ER flight test, the acoustic radiation characteristics of the sidewall and outboard floor system are investigated by experimental measurement. Analysis of the experimental data is performed using sound intensity calculations for closely spaced microphones, PATCH Inverse Boundary Element Nearfield Acoustic Holography, and Spherical Nearfield Acoustic Holography. Each method is compared assessing strengths and weaknesses, evaluating source identification capability for both broadband and narrowband sources, evaluating sources during transient and steady-state conditions, and quantifying field reconstruction continuity using multiple array positions.

  1. Robust active noise control in the loadmaster area of a military transport aircraft.

    PubMed

    Kochan, Kay; Sachau, Delf; Breitbach, Harald

    2011-05-01

    The active noise control (ANC) method is based on the superposition of a disturbance noise field with a second anti-noise field using loudspeakers and error microphones. This method can be used to reduce the noise level inside the cabin of a propeller aircraft. However, during the design process of the ANC system, extensive measurements of transfer functions are necessary to optimize the loudspeaker and microphone positions. Sometimes, the transducer positions have to be tailored according to the optimization results to achieve a sufficient noise reduction. The purpose of this paper is to introduce a controller design method for such narrow band ANC systems. The method can be seen as an extension of common transducer placement optimization procedures. In the presented method, individual weighting parameters for the loudspeakers and microphones are used. With this procedure, the tailoring of the transducer positions is replaced by adjustment of controller parameters. Moreover, the ANC system will be robust because of the fact that the uncertainties are considered during the optimization of the controller parameters. The paper describes the necessary theoretic background for the method and demonstrates the efficiency in an acoustical mock-up of a military transport aircraft.

  2. Prediction of noise levels and annoyance from aircraft run-ups at Vancouver International Airport.

    PubMed

    Scherebnyj, Katrina; Hodgson, Murray

    2007-10-01

    Annoyance complaints resulting from engine run-ups have been increasing at Vancouver International Airport for several years. To assist the Airport in managing run-up noise levels, a prediction tool based on a Green's function parabolic equation (GFPE) model has been consolidated, evaluated, and applied. It was extended to include more realistic atmospheric and ground input parameters. Measurements were made of the noise-radiation characteristics of a CRJ200 jet aircraft. The GFPE model was validated by comparing predictions with results in the literature. A sensitivity analysis showed that predicted levels are relatively insensitive to small variations in geometry and ground impedance, but relatively sensitive to variations in wind speed, atmosphere type, and aircraft heading and power setting. Predicted noise levels were compared with levels measured at noise monitoring terminals. For the four cases for which all input information was available, agreement was within 10 dBA. For events for which some information had to be estimated, predictions were within 20 dBA. The predicted annoyance corresponding to the run-up events considered ranged from 1.8% to 9.5% of people awoken, suggesting that noise complaints can be expected.

  3. Nonlinear acoustic propagation of launch vehicle and military jet aircraft noise

    NASA Astrophysics Data System (ADS)

    Gee, Kent L.

    2010-10-01

    The noise from launch vehicles and high-performance military jet aircraft has been shown to travel nonlinearly as a result of an amplitude-dependent speed of sound. Because acoustic pressure compressions travel faster than rarefactions, the waveform steepens and shocks form. This process results in a very different (and readily audible) noise signature and spectrum than predicted by linear models. On-going efforts to characterize the nonlinearity using statistical and spectral measures are described with examples from recent static tests of solid rocket boosters and the F-22 Raptor.

  4. Aircraft interior noise models - Sidewall trim, stiffened structures, and cabin acoustics with floor partition

    NASA Technical Reports Server (NTRS)

    Pope, L. D.; Wilby, E. G.; Willis, C. M.; Mayes, W. H.

    1983-01-01

    As part of the continuing development of an aircraft interior noise prediction model, in which a discrete modal representation and power flow analysis are used, theoretical results are considered for inclusion of sidewall trim, stiffened structures, and cabin acoustics with floor partition. For validation purposes, predictions of the noise reductions for three test articles (a bare ring-stringer stiffened cylinder, an unstiffened cylinder with floor and insulation, and a ring-stringer stiffened cylinder with floor and sidewall trim) are compared with measurements.

  5. Anticipated Effectiveness of Active Noise Control in Propeller Aircraft Interiors as Determined by Sound Quality Tests

    NASA Technical Reports Server (NTRS)

    Powell, Clemans A.; Sullivan, Brenda M.

    2004-01-01

    Two experiments were conducted, using sound quality engineering practices, to determine the subjective effectiveness of hypothetical active noise control systems in a range of propeller aircraft. The two tests differed by the type of judgments made by the subjects: pair comparisons in the first test and numerical category scaling in the second. Although the results of the two tests were in general agreement that the hypothetical active control measures improved the interior noise environments, the pair comparison method appears to be more sensitive to subtle changes in the characteristics of the sounds which are related to passenger preference.

  6. Investigation of acoustic properties of a rigid foam with application to noise reduction in light aircraft

    NASA Technical Reports Server (NTRS)

    Holmer, C. I.

    1972-01-01

    A analytic model of sound transmission into an aircraft cabin was developed as well as test procedures which appropriately rank order properties which affect sound transmission. The proposed model agrees well with available data, and reveals that the pertinent properties of an aircraft cabin for sound transmission include: stiffness of cabin walls at low frequencies (as this reflects on impedance of the walls) and cabin wall transmission loss and interior absorption at mid and high frequencies. Below 315 Hz the foam contributes substantially to wall stiffness and sound transmission loss of typical light aircraft cabin construction, and could potentially reduce cabin noise levels by 3-5 db in this frequency range at a cost of about 0:2 lb/sq. ft. of treated cabin area. The foam was found not to have significant sound absorbing properties.

  7. Lateral noise attenuation of the advanced propeller of the propfan test assessment aircraft

    NASA Technical Reports Server (NTRS)

    Chambers, F. W.; Reddy, N. N.; Bartel, H. W.

    1989-01-01

    Lateral noise attenuation characteristics of the advanced propeller are determined using the flight test results of the testbed aircraft, Propfan Test Assessment (PTA), with a single, large-scale propfan. The acoustic data were obtained with an array of ground-mounted microphones positioned at distances up to 2.47 km (8100 feet) to the side of the flight path. The aircraft was flown at a Mach number of 0.31 for a variety of operating conditions. The lateral noise attenuation in a frequency range containing the blade passage frequency of the propeller was found to have positive magnitudes on the propfan side and negative magnitudes on the opposite side. The measured attenuation exhibits a strong dependence upon the elevation angle. The results also display a clear dependence upon the angle at which the propeller and nacelle are mounted on the wing (inflow angle).

  8. Lateral noise-attenuation results from flyovers of three transport aircraft

    NASA Technical Reports Server (NTRS)

    Mashita, E. M.; Bauer, A. B.

    1979-01-01

    Lateral noise-attenuation data have been compiled in a one-third-octave-band analysis from an available set of flyover tests using DC-8, DC-9, and DC-10 aircraft. For an intermediate frequency range of 400 through 2000 Hertz the lateral noise has been approximately separated into its two components - the excess ground attenuation and the aircraft shielding attenuation. Both attenuation factors varied from a maximum at small elevation angles to zero at an elevation angle of approximately 40 degrees. The lateral attenuation in this range generally did not vary with frequency. For frequencies of 80 Hertz and lower, negative lateral attenuation values were obtained. For high frequencies, the data were not complete enough to generate definitive lateral attenuation curves.

  9. A new measurement method for separating airborne and structureborne noise radiated by aircraft type panels

    NASA Technical Reports Server (NTRS)

    Mcgary, M. C.

    1982-01-01

    The theoretical basis for and experimental validation of a measurement method for separating airborne and structure borne noise radiated by aircraft type panels are presented. An extension of the two microphone, cross spectral, acoustic intensity method combined with existing theory of sound radiation of thin shell structures of various designs, is restricted to the frequency range below the coincidence frequency of the structure. Consequently, the method lends itself to low frequency noise problems such as propeller harmonics. Both an aluminum sheet and two built up aircraft panel designs (two aluminum panels with frames and stringers) with and without added damping were measured. Results indicate that the method is quick, reliable, inexpensive, and can be applied to thin shell structures of various designs.

  10. Analysis of Acoustic Modeling and Sound Propagation in Aircraft Noise Prediction

    NASA Technical Reports Server (NTRS)

    Plotkin, Kenneth J.; Shepherd, Kevin P. (Technical Monitor)

    2006-01-01

    An analysis has been performed of measured and predicted aircraft noise levels around Denver International Airport. A detailed examination was made of 90 straight-out departures that yielded good measurements on multiple monitors. Predictions were made with INM 5, INM 6 and the simulation model NMSIM. Predictions were consistently lower than measurements, less so for the simulation model than for the integrated models. Lateral directivity ("installation effect") patterns were seen which are consistent with other recent measurements. Atmospheric absorption was determined to be a significant factor in the underprediction. Calculations of atmospheric attenuation were made over a full year of upper air data at seven locations across the United States. It was found that temperature/humidity effects could cause variations of up to +/-4 dB, depending on season, for the sites examined. It was concluded that local temperature and humidity should be accounted for in aircraft noise modeling.

  11. Inverting seismic noise cross-correlations for noise source distribution: A step towards reducing source-induced bias in seismic noise interferometry

    NASA Astrophysics Data System (ADS)

    Ermert, Laura; Afanasiev, Michael; Sager, Korbinian; Gokhberg, Alexey; Fichtner, Andreas

    2016-04-01

    We report on the ongoing development of a new inversion method for the space- and time-dependent power spectral density distribution of ambient seismic noise sources. The method, once complete, will mainly serve two purposes: First, it will allow us to construct more realistic forward models for noise cross-correlation waveforms, thereby opening new possibilities for waveform imaging by ambient noise tomography. Second, it may provide new insights about the properties of ambient noise sources, complementing studies based on beamforming or numerical modeling of noise based on oceanographic observations. To invert for noise sources, we consider surface wave signal energy measurements on the 'causal' (station A to B) and on the 'acausal' (station B to A) correlation branch, and the ratio between them. These and similar measurements have proven useful for locating noise sources using cross-correlations in several past studies. The inversion procedure is the following: We construct correlation forward models based on Green's functions from a spectral element wave propagation code. To construct these models efficiently, we use source-receiver reciprocity and assume spatial uncorrelation of noise sources. In such a setting, correlations can be calculated from a pre-computed set of Green's functions between the seismic receivers and sources located at the Earth's surface. We then calculate spatial sensitivity kernels for the noise source distribution with respect to the correlation signal energy measurements. These in turn allow us to construct a misfit gradient and optimize the source distribution model to fit our observed cross-correlation signal energies or energy ratios. We will present the workflow for calculation of the forward model and sensitivity kernels, as well as results for both forward modeling and kernels for an example data set of long-period noise or 'hum' at a global scale. We will also provide an outlook on the noise source inversion considering the

  12. Evaluation of a Hydrogen Fuel Cell Powered Blended-Wing-Body Aircraft Concept for Reduced Noise and Emissions

    NASA Technical Reports Server (NTRS)

    Guynn, Mark D.; Freh, Joshua E.; Olson, Erik D.

    2004-01-01

    This report describes the analytical modeling and evaluation of an unconventional commercial transport aircraft concept designed to address aircraft noise and emission issues. A blended-wing-body configuration with advanced technology hydrogen fuel cell electric propulsion is considered. Predicted noise and emission characteristics are compared to a current technology conventional configuration designed for the same mission. The significant technology issues which have to be addressed to make this concept a viable alternative to current aircraft designs are discussed. This concept is one of the "Quiet Green Transport" aircraft concepts studied as part of NASA's Revolutionary Aerospace Systems Concepts (RASC) Program. The RASC Program was initiated to develop revolutionary concepts that address strategic objectives of the NASA Enterprises, such as reducing aircraft noise and emissions, and to identify advanced technology requirements for the concepts.

  13. Evaluation of an Aircraft Concept With Over-Wing, Hydrogen-Fueled Engines for Reduced Noise and Emissions

    NASA Technical Reports Server (NTRS)

    Guynn, Mark D.; Olson, Erik D.

    2002-01-01

    This report describes the analytical modeling and evaluation of an unconventional commercial transport aircraft concept designed to address aircraft noise and emission issues. A strut-braced wing configuration with overwing, ultra-high bypass ratio, hydrogen fueled turbofan engines is considered. Estimated noise and emission characteristics are compared to a conventional configuration designed for the same mission and significant benefits are identified. The design challenges and technology issues which would have to be addressed to make the concept a viable alternative to current aircraft designs are discussed. This concept is one of the "Quiet Green Transport" aircraft concepts studied as part of NASA's Revolutionary Aerospace Systems Concepts (RASC) Program. The RASC Program seeks to develop revolutionary concepts that address strategic objectives of the NASA Enterprises, such as reducing aircraft noise and emissions, and to identify enabling advanced technology requirements for the concepts.

  14. Aircraft

    DTIC Science & Technology

    2002-01-01

    Company, Washington, DC Boeing Commercial Aircraft Division, Seattle, WA and Long Beach, CA Boeing Military Aircraft and Missile Division, St. Louis, MO and... aircraft ; military fixed-wing aircraft ; rotorcraft (helicopters and tiltrotor aircraft ); and aircraft jet engines. Two companies dominate the commercial... aircraft business, Boeing and Airbus. Four companies dominate the military fixed-wing market, Boeing, Lockheed Martin, BAE Systems, and European

  15. Executive Summary of Systems Analysis to Develop Future Civil Aircraft Noise Reduction Alternatives.

    DTIC Science & Technology

    1982-05-01

    AD-AIIB 4 PEER CONSULTANTS INC ROCKVILLE NO F/6 1/3 EXECUTIVE SUMMARY OF SYSTEMS ANALYSIS TO DEVELOP FUTURE CIVIL A-ETC(U) MAY B2 L A ROBINSON DTFAOI...Energy Washington, D.C. 20591 Develop Future Civil Aircraft Noise Reduction Alternatives Lilia Abron Robinson, Ph. D. PEER Consultants, Inc. 1160...ORGANIZATION CODE 7. AUTHOR(S) B. PERFORMING ORGANIZATION REPORT NO. PEER Consultants, Inc. 9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM

  16. a Survey on Health Effects due to Aircraft Noise on Residents Living around Kadena Air Base in the Ryukyus

    NASA Astrophysics Data System (ADS)

    Hiramatsu, K.; Yamamoto, T.; Taira, K.; Ito, A.; Nakasone, T.

    1997-08-01

    Results are reported of a questionnaire survey relating to a scale for general health, the Todai Health Index, in a town, bordering on a large U.S. airbase in the Ryukyus. The level of aircraft noise exposure, in the town, expressed by WECPNL, ranges from 75 to 95 or more. The sample size was 1200, including a 200 person “control” group. Results of the analysis of the responses in terms of the noise exposure suggest that the exposed residents suffer psychosomatic effects, especially perceived psychological disorders, due to the noise exposure to military aircraft, and that such responses increase with the level of noise exposure.

  17. Effects of low intensity noise from aircraft or from neighbourhood on cognitive learning and electrophysiological stress responses.

    PubMed

    Trimmel, Michael; Atzlsdorfer, Jürgen; Tupy, Nina; Trimmel, Karin

    2012-11-01

    The effects of low intensity noise on cognitive learning and autonomous physiological processes are of high practical relevance but are rarely addressed in empirical investigations. This study investigated the impact of neighbourhood noise (of 45 dB[A], n=20) and of noise coming from passing aircraft (of 48 dB[A] peak amplitude presented once per minute; n=19) during computer based learning of different texts (with three types of text structure, i.e. linear text, hierarchic hypertext, and network hypertext) in relation to a control group (35 dB[A], n=20). Using a between subjects design, reproduction scores, heart rate, and spontaneous skin conductance fluctuations were compared. Results showed impairments of reproduction in both noise conditions. Additionally, whereas in the control group and the neighbourhood noise group scores were better for network hypertext structure than for hierarchic hypertext, no effect of text structure on reproduction appeared in the aircraft noise group. Compared to the control group, for most of the learning period the number of spontaneous skin conductance fluctuations was higher for the aircraft noise group. For the neighbourhood noise group, fluctuations were higher during pre- and post task periods when noise stimulation was still present. Additionally, during the last 5 min of the 15 min learning period, an increased heart rate was found in the aircraft noise group. Data indicate remarkable cognitive and physiological effects of low intensity background noise. Some aspects of reproduction were impaired in the two noise groups. Cognitive learning, as indicated by reproduction scores, was changed structurally in the aircraft noise group and was accompanied by higher sympathetic activity. An additional cardiovascular load appeared for aircraft noise when combined with time pressure as indicated by heart rate for the announced last 5 min of the learning period during aircraft noise with a peak SPL of even 48 dB(A). Attentional

  18. Aircraft Conceptual Design and Risk Analysis Using Physics-Based Noise Prediction

    NASA Technical Reports Server (NTRS)

    Olson, Erik D.; Mavris, Dimitri N.

    2006-01-01

    An approach was developed which allows for design studies of commercial aircraft using physics-based noise analysis methods while retaining the ability to perform the rapid trade-off and risk analysis studies needed at the conceptual design stage. A prototype integrated analysis process was created for computing the total aircraft EPNL at the Federal Aviation Regulations Part 36 certification measurement locations using physics-based methods for fan rotor-stator interaction tones and jet mixing noise. The methodology was then used in combination with design of experiments to create response surface equations (RSEs) for the engine and aircraft performance metrics, geometric constraints and take-off and landing noise levels. In addition, Monte Carlo analysis was used to assess the expected variability of the metrics under the influence of uncertainty, and to determine how the variability is affected by the choice of engine cycle. Finally, the RSEs were used to conduct a series of proof-of-concept conceptual-level design studies demonstrating the utility of the approach. The study found that a key advantage to using physics-based analysis during conceptual design lies in the ability to assess the benefits of new technologies as a function of the design to which they are applied. The greatest difficulty in implementing physics-based analysis proved to be the generation of design geometry at a sufficient level of detail for high-fidelity analysis.

  19. Strategic planning for aircraft noise route impact analysis: A three dimensional approach

    NASA Technical Reports Server (NTRS)

    Bragdon, C. R.; Rowan, M. J.; Ahuja, K. K.

    1993-01-01

    The strategic routing of aircraft through navigable and controlled airspace to minimize adverse noise impact over sensitive areas is critical in the proper management and planning of the U.S. based airport system. A major objective of this phase of research is to identify, inventory, characterize, and analyze the various environmental, land planning, and regulatory data bases, along with potential three dimensional software and hardware systems that can be potentially applied for an impact assessment of any existing or planned air route. There are eight data bases that have to be assembled and developed in order to develop three dimensional aircraft route impact methodology. These data bases which cover geographical information systems, sound metrics, land use, airspace operational control measures, federal regulations and advisories, census data, and environmental attributes have been examined and aggregated. A three dimensional format is necessary for planning, analyzing space and possible noise impact, and formulating potential resolutions. The need to develop this three dimensional approach is essential due to the finite capacity of airspace for managing and planning a route system, including airport facilities. It appears that these data bases can be integrated effectively into a strategic aircraft noise routing system which should be developed as soon as possible, as part of a proactive plan applied to our FAA controlled navigable airspace for the United States.

  20. Optical linear algebra processors - Noise and error-source modeling

    NASA Technical Reports Server (NTRS)

    Casasent, D.; Ghosh, A.

    1985-01-01

    The modeling of system and component noise and error sources in optical linear algebra processors (OLAPs) are considered, with attention to the frequency-multiplexed OLAP. General expressions are obtained for the output produced as a function of various component errors and noise. A digital simulator for this model is discussed.

  1. Optical linear algebra processors: noise and error-source modeling.

    PubMed

    Casasent, D; Ghosh, A

    1985-06-01

    The modeling of system and component noise and error sources in optical linear algebra processors (OLAP's) are considered, with attention to the frequency-multiplexed OLAP. General expressions are obtained for the output produced as a function of various component errors and noise. A digital simulator for this model is discussed.

  2. Shielding of Turbomachinery Broadband Noise from a Hybrid Wing Body Aircraft Configuration

    NASA Technical Reports Server (NTRS)

    Hutcheson, Florence V.; Brooks, Thomas F.; Burley, Casey L.; Bahr, Christopher J.; Stead, Daniel J.; Pope, D. Stuart

    2014-01-01

    The results of an experimental study on the effects of engine placement and vertical tail configuration on shielding of exhaust broadband noise radiation are presented. This study is part of the high fidelity aeroacoustic test of a 5.8% scale Hybrid Wing Body (HWB) aircraft configuration performed in the 14- by 22-Foot Subsonic Tunnel at NASA Langley Research Center. Broadband Engine Noise Simulators (BENS) were used to determine insertion loss due to shielding by the HWB airframe of the broadband component of turbomachinery noise for different airframe configurations and flight conditions. Acoustics data were obtained from flyover and sideline microphones traversed to predefined streamwise stations. Noise measurements performed for different engine locations clearly show the noise benefit associated with positioning the engine nacelles further upstream on the HWB centerbody. Positioning the engine exhaust 2.5 nozzle diameters upstream (compared to 0.5 nozzle diameters downstream) of the HWB trailing edge was found of particular benefit in this study. Analysis of the shielding performance obtained with and without tunnel flow show that the effectiveness of the fuselage shielding of the exhaust noise, although still significant, is greatly reduced by the presence of the free stream flow compared to static conditions. This loss of shielding is due to the turbulence in the model near-wake/boundary layer flow. A comparison of shielding obtained with alternate vertical tail configurations shows limited differences in level; nevertheless, overall trends regarding the effect of cant angle and vertical location are revealed. Finally, it is shown that the vertical tails provide a clear shielding benefit towards the sideline while causing a slight increase in noise below the aircraft.

  3. Intrinsic Noise Level of Noise Cross-Correlation Functions and its Implication to Source Population of Ambient noises

    NASA Astrophysics Data System (ADS)

    Chen, Ying-Nien; Gung, Yuancheng; Chiao, Ling-Yun; Rhie, Junkee

    2017-01-01

    SUMMARYWe present a quantitative procedure to evaluate the intrinsic <span class="hlt">noise</span> level (INL) of the <span class="hlt">noise</span> cross-correlation function (NCF). The method is applied to realistic NCFs derived from the continuous data recorded by the seismic arrays in Taiwan and Korea. The obtained temporal evolution of NCF <span class="hlt">noise</span> level follows fairly the prediction of the theoretical formulation, confirming the feasibility of the method. We then apply the obtained INL to the assessment of data quality and the <span class="hlt">source</span> characteristics of ambient <span class="hlt">noise</span>. We show that the INL-based signal-to-<span class="hlt">noise</span> ratio provides an exact measure for the true <span class="hlt">noise</span> level within the NCF and better resolving power for the NCF quality, and such measurement can be implemented to any time windows of the NCFs to evaluate the quality of overtones or coda waves. Moreover, since NCF amplitudes are influenced by both the population and excitation strengths of <span class="hlt">noises</span>, while INL is primarily sensitive to the overall <span class="hlt">source</span> population, with information from both measurements, we may better constrain the <span class="hlt">source</span> characteristics of seismic ambient <span class="hlt">noises</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770059282&hterms=sleeping&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dsleeping','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770059282&hterms=sleeping&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dsleeping"><span>Arousal from sleep - The physiological and subjective effects of a 15 dB/A/ reduction in <span class="hlt">aircraft</span> flyover <span class="hlt">noise</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Levere, T. E.; Davis, N.</p> <p>1977-01-01</p> <p>The present research was concerned with whether or not a 15 dB(A) reduction in overall <span class="hlt">noise</span> level would lessen the sleep disturbing properties of jet <span class="hlt">aircraft</span> flyover <span class="hlt">noise</span> and, if less disturbing, whether this would be subjectively appreciated by the sleeping individual. The results indicate that a reduction of 15 dB (A) does result in less sleep disruption but only during sleep characterized by fast-wave electroencephalographic activity. During sleep characterized by slow-wave electroencephalographic activity, such a reduction in the sleep-disturbing properties of jet <span class="hlt">aircraft</span> <span class="hlt">noise</span> has little effect. Moreover, even when effective during fast-wave sleep, the decreased arousal produced by the lower <span class="hlt">noise</span> levels is not subjectively appreciated by the individual in terms of his estimate of the quality of his night's sleep. Thus, reducing the overall <span class="hlt">noise</span> level of jet <span class="hlt">aircraft</span> flyovers by some 15 dB(A), is, at best, minimally beneficial to sleep.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720019381','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720019381"><span>Comparison of wind tunnel and flyover <span class="hlt">noise</span> measurements of the YOV-10A STOL <span class="hlt">aircraft</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Atencio, A., Jr.; Soderman, P. T.</p> <p>1972-01-01</p> <p>The YOV-10A Research <span class="hlt">Aircraft</span> was flown to obtain flyover <span class="hlt">noise</span> data that could be compared to <span class="hlt">noise</span> data measured in the 40- by 80- foot wind tunnel at NASA Ames Research Center. The flyover <span class="hlt">noise</span> measurements were made during the early morning hours on runway 32L at Moffett Field, California. A number of passes were made at 50 ft altitude in level flight with an airplane configuration closely matching that tested in the wind tunnel. Two passes were selected as prime and were designated for full data reduction. The YOV-10A was flown over a microphone field geometrically similar to the microphone array set up in the wind tunnel. An acoustic center was chosen as a matching point for the data. Data from the wind tunnel and flyover were reduced and appropiate corrections were applied to compare the data. Results show that wind tunnel and flight test acoustic data agreed closely.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APhy...62..495P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APhy...62..495P"><span><span class="hlt">Noise</span> simulation of <span class="hlt">aircraft</span> engine fans by the boundary element method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pyatunin, K. R.; Arkharova, N. V.; Remizov, A. E.</p> <p>2016-07-01</p> <p>Numerical simulation results of the civil <span class="hlt">aircraft</span> engine fan stage <span class="hlt">noise</span> in the far field are presented. Non-steady-state rotor-stator interaction is calculated the commercial software that solves the Navier-Stokes equations using differentturbulence models. <span class="hlt">Noise</span> propagation to the far acoustic field is calculated by the boundary element method using acoustic Lighthill analogies without taking into account the mean current in the air inlet duct. The calculated sound pressure levels at points 50 m from the engine are presented, and the directional patterns of the acoustic radiation are shown. The use of the eddy resolving turbulence model to calculate rotor-stator interaction increases the accuracy in predicting fan stage <span class="hlt">noise</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740012547','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740012547"><span>Effect of advanced <span class="hlt">aircraft</span> <span class="hlt">noise</span> reduction technology on the 1990 projected <span class="hlt">noise</span> environment around Patrick Henry Airport. [development of <span class="hlt">noise</span> exposure forecast contours for projected traffic volume and <span class="hlt">aircraft</span> types</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cawthorn, J. M.; Brown, C. G.</p> <p>1974-01-01</p> <p>A study has been conducted of the future <span class="hlt">noise</span> environment of Patric Henry Airport and its neighboring communities projected for the year 1990. An assessment was made of the impact of advanced <span class="hlt">noise</span> reduction technologies which are currently being considered. These advanced technologies include a two-segment landing approach procedure and <span class="hlt">aircraft</span> hardware modifications or retrofits which would add sound absorbent material in the nacelles of the engines or which would replace the present two- and three-stage fans with a single-stage fan of larger diameter. <span class="hlt">Noise</span> Exposure Forecast (NEF) contours were computed for the baseline (nonretrofitted) <span class="hlt">aircraft</span> for the projected traffic volume and fleet mix for the year 1990. These NEF contours are presented along with contours for a variety of retrofit options. Comparisons of the baseline with the <span class="hlt">noise</span> reduction options are given in terms of total land area exposed to 30 and 40 NEF levels. Results are also presented of the effects on <span class="hlt">noise</span> exposure area of the total number of daily operations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014RScI...85b4702G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014RScI...85b4702G"><span>Large bandwidth op-amp based white <span class="hlt">noise</span> current <span class="hlt">source</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Giusi, Gino; Scandurra, Graziella; Ciofi, Carmine</p> <p>2014-02-01</p> <p>Electrical <span class="hlt">noise</span> <span class="hlt">sources</span> are basic building blocks in many measurement and instrumentation applications and in communication systems. In this paper, we propose a quite simple topology for the realization of a programmable, wide bandwidth, white <span class="hlt">noise</span> current <span class="hlt">source</span> that requires only two resistors and one operational amplifier. We validate the proposed approach by means of SPICE simulations and demonstrate, by means of proper measurements, the capability of generating a flat current <span class="hlt">noise</span> spectrum in a frequency range up to four decades from a few Hz up to 100 kHz.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22489369','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22489369"><span>Demonstration of Johnson <span class="hlt">noise</span> thermometry with all-superconducting quantum voltage <span class="hlt">noise</span> <span class="hlt">source</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yamada, Takahiro Urano, Chiharu; Maezawa, Masaaki</p> <p>2016-01-25</p> <p>We present a Johnson <span class="hlt">noise</span> thermometry (JNT) system based on an integrated quantum voltage <span class="hlt">noise</span> <span class="hlt">source</span> (IQVNS) that has been fully implemented using superconducting circuit technology. To enable precise measurement of Boltzmann's constant, an IQVNS chip was designed to produce intrinsically calculable pseudo-white <span class="hlt">noise</span> to calibrate the JNT system. On-chip real-time generation of pseudo-random codes via simple circuits produced pseudo-voltage <span class="hlt">noise</span> with a harmonic tone interval of less than 1 Hz, which was one order of magnitude finer than the harmonic tone interval of conventional quantum voltage <span class="hlt">noise</span> <span class="hlt">sources</span>. We estimated a value for Boltzmann's constant experimentally by performing JNT measurements at the temperature of the triple point of water using the IQVNS chip.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760021873','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760021873"><span>Landing gear and cavity <span class="hlt">noise</span> prediction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bliss, D. B.; Hayden, R. E.</p> <p>1976-01-01</p> <p>Prediction of airframe <span class="hlt">noise</span> radiation from the landing gear and wheel wells of commercial <span class="hlt">aircraft</span> is examined. Measurements of these components on typical <span class="hlt">aircraft</span> are presented and potential <span class="hlt">noise</span> <span class="hlt">sources</span> identified. Semiempirical expressions for the sound generation by these <span class="hlt">sources</span> are developed from available experimental data and theoretical analyses. These expressions are employed to estimate the <span class="hlt">noise</span> radiation from the landing gear and wheel wells for a typical <span class="hlt">aircraft</span> and to rank order the component <span class="hlt">sources</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26526769','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26526769"><span>Airborne exposure patterns from a passenger <span class="hlt">source</span> in <span class="hlt">aircraft</span> cabins.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bennett, James S; Jones, Byron W; Hosni, Mohammad H; Zhang, Yuanhui; Topmiller, Jennifer L; Dietrich, Watts L</p> <p>2013-01-01</p> <p>Airflow is a critical factor that influences air quality, airborne contaminant distribution, and disease transmission in commercial airliner cabins. The general <span class="hlt">aircraft</span>-cabin air-contaminant transport effect model seeks to build exposure-spatial relationships between contaminant <span class="hlt">sources</span> and receptors, quantify the uncertainty, and provide a platform for incorporation of data from a variety of studies. Knowledge of infection risk to flight crews and passengers is needed to form a coherent response to an unfolding epidemic, and infection risk may have an airborne pathogen exposure component. The general aircraf-tcabin air-contaminant transport effect model was applied to datasets from the University of Illinois and Kansas State University and also to case study information from a flight with probable severe acute respiratory syndrome transmission. Data were fit to regression curves, where the dependent variable was contaminant concentration (normalized for <span class="hlt">source</span> strength and ventilation rate), and the independent variable was distance between <span class="hlt">source</span> and measurement locations. The data-driven model showed exposure to viable small droplets and post-evaporation nuclei at a <span class="hlt">source</span> distance of several rows in a mock-up of a twin-aisle airliner with seven seats per row. Similar behavior was observed in tracer gas, particle experiments, and flight infection data for severe acute respiratory syndrome. The study supports the airborne pathway as part of the matrix of possible disease transmission modes in <span class="hlt">aircraft</span> cabins.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4626449','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4626449"><span>Airborne exposure patterns from a passenger <span class="hlt">source</span> in <span class="hlt">aircraft</span> cabins</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bennett, James S.; Jones, Byron W.; Hosni, Mohammad H.; Zhang, Yuanhui; Topmiller, Jennifer L.; Dietrich, Watts L.</p> <p>2015-01-01</p> <p>Airflow is a critical factor that influences air quality, airborne contaminant distribution, and disease transmission in commercial airliner cabins. The general <span class="hlt">aircraft</span>-cabin air-contaminant transport effect model seeks to build exposure-spatial relationships between contaminant <span class="hlt">sources</span> and receptors, quantify the uncertainty, and provide a platform for incorporation of data from a variety of studies. Knowledge of infection risk to flight crews and passengers is needed to form a coherent response to an unfolding epidemic, and infection risk may have an airborne pathogen exposure component. The general aircraf-tcabin air-contaminant transport effect model was applied to datasets from the University of Illinois and Kansas State University and also to case study information from a flight with probable severe acute respiratory syndrome transmission. Data were fit to regression curves, where the dependent variable was contaminant concentration (normalized for <span class="hlt">source</span> strength and ventilation rate), and the independent variable was distance between <span class="hlt">source</span> and measurement locations. The data-driven model showed exposure to viable small droplets and post-evaporation nuclei at a <span class="hlt">source</span> distance of several rows in a mock-up of a twin-aisle airliner with seven seats per row. Similar behavior was observed in tracer gas, particle experiments, and flight infection data for severe acute respiratory syndrome. The study supports the airborne pathway as part of the matrix of possible disease transmission modes in <span class="hlt">aircraft</span> cabins. PMID:26526769</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4835309','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4835309"><span>Inter-individual Differences in the Effects of <span class="hlt">Aircraft</span> <span class="hlt">Noise</span> on Sleep Fragmentation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>McGuire, Sarah; Müller, Uwe; Elmenhorst, Eva-Maria; Basner, Mathias</p> <p>2016-01-01</p> <p>-assessed based on these findings. Citation: McGuire S, Müller U, Elmenhorst EM, Basner M. Inter-individual differences in the effects of <span class="hlt">aircraft</span> <span class="hlt">noise</span> on sleep fragmentation. SLEEP 2016;39(5):1107–1110. PMID:26856901</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005ASAJ..117.2363S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005ASAJ..117.2363S"><span>Implications of the road traffic and <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure and children's cognition and health (RANCH) study results for classroom acoustics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stansfeld, Stephen A.; Clark, Charlotte</p> <p>2005-04-01</p> <p>Studies in West London have found associations between <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure and childrens' cognitive performance. This has culminated in the RANCH Study examining exposure-effect associations between <span class="hlt">aircraft</span> and road traffic <span class="hlt">noise</span> exposure and cognitive performance and health. The RANCH project, the largest cross-sectional study of <span class="hlt">noise</span> and childrens health, examined 2844 children, 9-10 years old, from 89 schools around three major airports: in the Netherlands, Spain and the United Kingdom. Children were selected by external <span class="hlt">aircraft</span> and road traffic <span class="hlt">noise</span> exposure at school predicted from <span class="hlt">noise</span> contour maps, modeling and on-site measurements. A substudy indicated high internal levels of <span class="hlt">noise</span> within classrooms. Schools were matched for socioeconomic position within countries. Cognitive and health outcomes were measured by standardized tests and questionnaires administered in the classroom. A parental questionnaire collected information on socioeconomic position, parental education and ethnicity. Linear exposure-effect associations were found between chronic <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure and impairment of reading comprehension and recognition memory, maintained after adjustment for mothers education, socioeconomic factors, longstanding illness and classroom insulation. Road traffic <span class="hlt">noise</span> exposure was linearly associated with episodic memory. The implications of these results for childrens' learning environments will be discussed. [Work supported by European Community (QLRT-2000-00197) Vth framework program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19820006800','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19820006800"><span>Effects of <span class="hlt">aircraft</span> <span class="hlt">noise</span> on the equilibrium of airport residents: Supplementary analyses to the study carried out around Orly</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Francois, J.</p> <p>1981-01-01</p> <p>The effects of <span class="hlt">aircraft</span> <span class="hlt">noise</span> on humans living near airports were studied. Two main questions were considered: do residents give evidence of psychological or physiological disturbances in unusually intense <span class="hlt">noise</span> sectors; and do personality or health factors account for the high interindividual variability of annoyance? The methodology used and results obtained are presented. Samples of the survey questionnaires are included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23505502','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23505502"><span>MEG <span class="hlt">source</span> localization using invariance of <span class="hlt">noise</span> space.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Junpeng; Raij, Tommi; Hämäläinen, Matti; Yao, Dezhong</p> <p>2013-01-01</p> <p>We propose INvariance of <span class="hlt">Noise</span> (INN) space as a novel method for <span class="hlt">source</span> localization of magnetoencephalography (MEG) data. The method is based on the fact that modulations of <span class="hlt">source</span> strengths across time change the energy in signal subspace but leave the <span class="hlt">noise</span> subspace invariant. We compare INN with classical MUSIC, RAP-MUSIC, and beamformer approaches using simulated data while varying signal-to-<span class="hlt">noise</span> ratios as well as distance and temporal correlation between two <span class="hlt">sources</span>. We also demonstrate the utility of INN with actual auditory evoked MEG responses in eight subjects. In all cases, INN performed well, especially when the <span class="hlt">sources</span> were closely spaced, highly correlated, or one <span class="hlt">source</span> was considerably stronger than the other.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/3954697','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/3954697"><span><span class="hlt">Noise</span> levels in cockpits of <span class="hlt">aircraft</span> during normal cruise and considerations of auditory risk.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gasaway, D C</p> <p>1986-02-01</p> <p><span class="hlt">Noise</span> data, including A-levels and C-minus-A values, are summarized for exposures associated with normal cruise flight in 13 groups of 593 <span class="hlt">aircraft</span>; means and standard deviations are reported; degrees of auditory risk using OSHA-1983 criterion are presented; and at-the-ear protected and unprotected exposures are revealed. Mean A-levels were 95.0 for 528 fixed-wing; 100.9 for 65 rotary-wing; and 95.7 for all 593 <span class="hlt">aircraft</span>. Of 13 sub-groups, the lowest mean A-level (85.5) was exhibited in the cockpits of tail-mounted turbojet/fan-powered <span class="hlt">aircraft</span>, and the highest (105.0) was found in both reciprocating and turbine-powered twin-rotor helicopters. All mean A-levels exceeded the OSHA damage-risk criterion for 8 h.d-1 exposures. At-the-ear exposures while wearing hearing protection are presented. Results clearly illustrate the potential for auditory damage of unprotected aircrews. Hearing protection must be considered to effectively control routinely encountered exposures. The material and illustrations resulting from this study will help health and safety monitors during indoctrination and counseling of aircrews concerning the need to protect their hearing against <span class="hlt">noise</span> exposures during normal and routine flight operations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780004857','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780004857"><span>Measurements of the tonal component of cavity <span class="hlt">noise</span> and comparison with theory. [<span class="hlt">aircraft</span> <span class="hlt">noise</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Block, P. J. W.</p> <p>1977-01-01</p> <p>The frequency of the tonal <span class="hlt">noise</span> generated by a flow-excited rectangular cavity was measured using Mach numbers ranging from 0.05 to 0.40, and cavity length-to-depth ratios varying from 0.1 to 8. The data are used to evaluate a current prediction method, and good agreement is shown. Measurements of the minimum streamwise cavity length required for oscillation were also made.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920005567','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920005567"><span>Interior <span class="hlt">Noise</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mixson, John S.; Wilby, John F.</p> <p>1991-01-01</p> <p>The generation and control of flight vehicle interior <span class="hlt">noise</span> is discussed. Emphasis is placed on the mechanisms of transmission through airborne and structure-borne paths and the control of cabin <span class="hlt">noise</span> by path modification. Techniques for identifying the relative contributions of the various <span class="hlt">source</span>-path combinations are also discussed along with methods for the prediction of <span class="hlt">aircraft</span> interior <span class="hlt">noise</span> such as those based on the general modal theory and statistical energy analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750024675','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750024675"><span>Emotionality in response to <span class="hlt">aircraft</span> <span class="hlt">noise</span>: A report of development work</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Klaus, P. A.</p> <p>1975-01-01</p> <p>A literature search and pilot study conducted to investigate the topic of emotional response to <span class="hlt">aircraft</span> <span class="hlt">noise</span> are described. A Tell-A-Story Technique was developed for use in the pilot study which required respondents to make up stories for a series of <span class="hlt">aircraft</span>-related and non-<span class="hlt">aircraft</span>-related pictures. A content analysis of these stories was made. The major finding was that response patterns varied among three groups of respondents - those currently living near airports, those who had lived near airports in the past, and those who had never lived near airports. Negative emotional feelings toward <span class="hlt">aircraft</span> were greatest among respondents who had lived near airports in the past but no longer did. A possible explanation offered for this finding was that people currently living near airports might adapt to the situation by denying some of their negative feelings, which they might feel more free to express after they had moved away from the situation. Other techniques used in the pilot study are also described, including group interviews and a word association task.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JAG...128....1J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JAG...128....1J"><span>A de-<span class="hlt">noising</span> algorithm based on wavelet threshold-exponential adaptive window width-fitting for ground electrical <span class="hlt">source</span> airborne transient electromagnetic signal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ji, Yanju; Li, Dongsheng; Yu, Mingmei; Wang, Yuan; Wu, Qiong; Lin, Jun</p> <p>2016-05-01</p> <p>The ground electrical <span class="hlt">source</span> airborne transient electromagnetic system (GREATEM) on an unmanned <span class="hlt">aircraft</span> enjoys considerable prospecting depth, lateral resolution and detection efficiency, etc. In recent years it has become an important technical means of rapid resources exploration. However, GREATEM data are extremely vulnerable to stationary white <span class="hlt">noise</span> and non-stationary electromagnetic <span class="hlt">noise</span> (sferics <span class="hlt">noise</span>, <span class="hlt">aircraft</span> engine <span class="hlt">noise</span> and other human electromagnetic <span class="hlt">noises</span>). These <span class="hlt">noises</span> will cause degradation of the imaging quality for data interpretation. Based on the characteristics of the GREATEM data and major <span class="hlt">noises</span>, we propose a de-<span class="hlt">noising</span> algorithm utilizing wavelet threshold method and exponential adaptive window width-fitting. Firstly, the white <span class="hlt">noise</span> is filtered in the measured data using the wavelet threshold method. Then, the data are segmented using data window whose step length is even logarithmic intervals. The data polluted by electromagnetic <span class="hlt">noise</span> are identified within each window based on the discriminating principle of energy detection, and the attenuation characteristics of the data slope are extracted. Eventually, an exponential fitting algorithm is adopted to fit the attenuation curve of each window, and the data polluted by non-stationary electromagnetic <span class="hlt">noise</span> are replaced with their fitting results. Thus the non-stationary electromagnetic <span class="hlt">noise</span> can be effectively removed. The proposed algorithm is verified by the synthetic and real GREATEM signals. The results show that in GREATEM signal, stationary white <span class="hlt">noise</span> and non-stationary electromagnetic <span class="hlt">noise</span> can be effectively filtered using the wavelet threshold-exponential adaptive window width-fitting algorithm, which enhances the imaging quality.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992cacn.agarT....B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992cacn.agarT....B"><span>Measurement and prediction of <span class="hlt">noise</span> from low-altitude military <span class="hlt">aircraft</span> operations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barry, Bernard F.; Payne, Richard C.; Harris, Anthony L.; Weston, Ralph J.</p> <p>1992-04-01</p> <p>In response to the rapid growth in demand for information on <span class="hlt">noise</span> levels around military airfields in the UK, NPL developed AIRNOISE, a mathematical model for computing <span class="hlt">aircraft</span> <span class="hlt">noise</span> contours. Since its first applications in 1981, the model has been used to determine zones of eligibility within the MoD compensation scheme. The model has been subject to continuous development, e.g., the incorporation of Harrier V/STOL operations. We have now extended the model to include <span class="hlt">noise</span> from high-speed, low-level operations. The model predicts not only maximum levels but the complete time-history, so that the time-onset rate can be estimated. To aid refinement and validation of the model, a special exercise has been conducted in which Tornado, Harrier, Jaguar, Hawk, F-15 and F-16 <span class="hlt">aircraft</span> have flown straight and level at heights between about 100 and 400 feet, at various speeds and engine power settings over an array of microphones. This paper describes the trial and the results obtained. The prediction model is outlined and comparisons made between predictions and measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900005550','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900005550"><span>Evaluation of analysis techniques for low frequency interior <span class="hlt">noise</span> and vibration of commercial <span class="hlt">aircraft</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Landmann, A. E.; Tillema, H. F.; Marshall, S. E.</p> <p>1989-01-01</p> <p>The application of selected analysis techniques to low frequency cabin <span class="hlt">noise</span> associated with advanced propeller engine installations is evaluated. Three design analysis techniques were chosen for evaluation including finite element analysis, statistical energy analysis (SEA), and a power flow method using element of SEA (computer program Propeller <span class="hlt">Aircraft</span> Interior <span class="hlt">Noise</span>). An overview of the three procedures is provided. Data from tests of a 727 airplane (modified to accept a propeller engine) were used to compare with predictions. Comparisons of predicted and measured levels at the end of the first year's effort showed reasonable agreement leading to the conclusion that each technique had value for propeller engine <span class="hlt">noise</span> predictions on large commercial transports. However, variations in agreement were large enough to remain cautious and to lead to recommendations for further work with each technique. Assessment of the second year's results leads to the conclusion that the selected techniques can accurately predict trends and can be useful to a designer, but that absolute level predictions remain unreliable due to complexity of the <span class="hlt">aircraft</span> structure and low modal densities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999JSV...222..489N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999JSV...222..489N"><span>a Graphical Optimization of Take-Off <span class="hlt">Noise</span> Abatement Procedures for Subsonic <span class="hlt">Aircraft</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Norgia, L.</p> <p>1999-05-01</p> <p>This paper describes a numerical approach to the simulation of <span class="hlt">noise</span> contours generated during <span class="hlt">aircraft</span> operations. Common features of many existing <span class="hlt">noise</span>-contour programs make these procedures unsuitable for on-line piloted-simulator use. In fact, they usually require large computational tools and exhibit complex structure, so that they generally run quite slowly. The method proposed here is an attempt to overcome some of the above drawbacks. It works for arbitrarily complex take-off and landing paths, and reveals the influence of several quantitites on the shape and size of the contours. Besides, the calculations are simple enough to be implemented on a handheld programmable calculator. The method runs fast, and quickly provides contour shape, evaluates area and analyzes main characteristics of the end. The method has been used to optimize <span class="hlt">noise</span> abatement procedures for subsonic <span class="hlt">aircraft</span>; for every take-off procedure the model can generate an isofootprint on the ground which helps the operator to choose the best take-off solution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760007700','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760007700"><span>A review and preliminary evaluation of methodological factors in performance assessments of time-varying <span class="hlt">aircraft</span> <span class="hlt">noise</span> effects</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Coates, G. D.; Alluisi, E. A.</p> <p>1975-01-01</p> <p>The effects of <span class="hlt">aircraft</span> <span class="hlt">noise</span> on human performance is considered. Progress is reported in the following areas: (1) review of the literature to identify the methodological and stimulus parameters involved in the study of <span class="hlt">noise</span> effects on human performance; (2) development of a theoretical framework to provide working hypotheses as to the effects of <span class="hlt">noise</span> on complex human performance; and (3) data collection on the first of several experimental investigations designed to provide tests of the hypotheses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880036532&hterms=Propellers+aircraft&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DPropellers%2Baircraft','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880036532&hterms=Propellers+aircraft&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DPropellers%2Baircraft"><span>Propeller <span class="hlt">aircraft</span> interior <span class="hlt">noise</span> model. II - Scale-model and flight-test comparisons</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Willis, C. M.; Mayes, W. H.</p> <p>1987-01-01</p> <p>A program for predicting the sound levels inside propeller driven <span class="hlt">aircraft</span> arising from sidewall transmission of airborne exterior <span class="hlt">noise</span> is validated through comparisons of predictions with both scale-model test results and measurements obtained in flight tests on a turboprop <span class="hlt">aircraft</span>. The program produced unbiased predictions for the case of the scale-model tests, with a standard deviation of errors of about 4 dB. For the case of the flight tests, the predictions revealed a bias of 2.62-4.28 dB (depending upon whether or not the data for the fourth harmonic were included) and the standard deviation of the errors ranged between 2.43 and 4.12 dB. The analytical model is shown to be capable of taking changes in the flight environment into account.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740025342','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740025342"><span>Static <span class="hlt">noise</span> tests on augmentor wing jet STOL research <span class="hlt">aircraft</span> (C8A Buffalo)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Marrs, C. C.; Harkonen, D. L.; Okeefe, J. V.</p> <p>1974-01-01</p> <p>Results are presented for full scale ground static acoustic tests of over-area conical nozzles and a lobe nozzle installed on the Augmentor Wing Jet STOL Research <span class="hlt">Aircraft</span>, a modified C8A Buffalo. The <span class="hlt">noise</span> levels and spectrums of the test nozzles are compared against those of the standard conical nozzle now in use on the <span class="hlt">aircraft</span>. Acoustic evaluations at 152 m (500 ft), 304 m (1000 ft), and 1216 m (4000 ft) are made at various engine power settings with the emphasis on approach and takeoff power. Appendix A contains the test log and propulsion calculations. Appendix B gives the original test plan, which was closely adhered to during the test. Appendix C describes the acoustic data recording and reduction systems, with calibration details.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19770012808','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770012808"><span>A review of methodological factors in performance assessments of time-varying <span class="hlt">aircraft</span> <span class="hlt">noise</span> effects. [with annotated bibliography</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Coates, G. D.; Alluisi, E. A.; Adkins, C. J., Jr.</p> <p>1977-01-01</p> <p>Literature on the effects of general <span class="hlt">noise</span> on human performance is reviewed in an attempt to identify (1) those characteristics of <span class="hlt">noise</span> that have been found to affect human performance; (2) those characteristics of performance most likely to be affected by the presence of <span class="hlt">noise</span>, and (3) those characteristics of the performance situation typically associated with <span class="hlt">noise</span> effects. Based on the characteristics identified, a theoretical framework is proposed that will permit predictions of possible effects of time-varying <span class="hlt">aircraft</span>-type <span class="hlt">noise</span> on complex human performance. An annotated bibliography of 50 articles is included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120006513','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120006513"><span>Sub-Shot <span class="hlt">Noise</span> Power <span class="hlt">Source</span> for Microelectronics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Strekalov, Dmitry V.; Yu, Nan; Mansour, Kamjou</p> <p>2011-01-01</p> <p>Low-current, high-impedance microelectronic devices can be affected by electric current shot <span class="hlt">noise</span> more than they are affected by Nyquist <span class="hlt">noise</span>, even at room temperature. An approach to implementing a sub-shot <span class="hlt">noise</span> current <span class="hlt">source</span> for powering such devices is based on direct conversion of amplitude-squeezed light to photocurrent. The phenomenon of optical squeezing allows for the optical measurements below the fundamental shot <span class="hlt">noise</span> limit, which would be impossible in the domain of classical optics. This becomes possible by affecting the statistical properties of photons in an optical mode, which can be considered as a case of information encoding. Once encoded, the information describing the photon (or any other elementary excitations) statistics can be also transmitted. In fact, it is such information transduction from optics to an electronics circuit, via photoelectric effect, that has allowed the observation of the optical squeezing. It is very difficult, if not technically impossible, to directly measure the statistical distribution of optical photons except at extremely low light level. The photoelectric current, on the other hand, can be easily analyzed using RF spectrum analyzers. Once it was observed that the photocurrent <span class="hlt">noise</span> generated by a tested light <span class="hlt">source</span> in question is below the shot <span class="hlt">noise</span> limit (e.g. produced by a coherent light beam), it was concluded that the light <span class="hlt">source</span> in question possess the property of amplitude squeezing. The main novelty of this technology is to turn this well-known information transduction approach around. Instead of studying the statistical property of an optical mode by measuring the photoelectron statistics, an amplitude-squeezed light <span class="hlt">source</span> and a high-efficiency linear photodiode are used to generate photocurrent with sub-Poissonian electron statistics. By powering microelectronic devices with this current <span class="hlt">source</span>, their performance can be improved, especially their <span class="hlt">noise</span> parameters. Therefore, a room-temperature sub</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090015381','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090015381"><span>Jet <span class="hlt">Noise</span> Modeling for Suppressed and Unsuppressed <span class="hlt">Aircraft</span> in Simulated Flight</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stone, James R.; Krejsa, Eugene A.; Clark, Bruce J; Berton, Jeffrey J.</p> <p>2009-01-01</p> <p>This document describes the development of further extensions and improvements to the jet <span class="hlt">noise</span> model developed by Modern Technologies Corporation (MTC) for the National Aeronautics and Space Administration (NASA). The <span class="hlt">noise</span> component extraction and correlation approach, first used successfully by MTC in developing a <span class="hlt">noise</span> prediction model for two-dimensional mixer ejector (2DME) nozzles under the High Speed Research (HSR) Program, has been applied to dual-stream nozzles, then extended and improved in earlier tasks under this contract. Under Task 6, the coannular jet <span class="hlt">noise</span> model was formulated and calibrated with limited scale model data, mainly at high bypass ratio, including a limited-range prediction of the effects of mixing-enhancement nozzle-exit chevrons on jet <span class="hlt">noise</span>. Under Task 9 this model was extended to a wider range of conditions, particularly those appropriate for a Supersonic Business Jet, with an improvement in simulated flight effects modeling and generalization of the suppressor model. In the present task further comparisons are made over a still wider range of conditions from more test facilities. The model is also further generalized to cover single-stream nozzles of otherwise similar configuration. So the evolution of this prediction/analysis/correlation approach has been in a sense backward, from the complex to the simple; but from this approach a very robust capability is emerging. Also from these studies, some observations emerge relative to theoretical considerations. The purpose of this task is to develop an analytical, semi-empirical jet <span class="hlt">noise</span> prediction method applicable to takeoff, sideline and approach <span class="hlt">noise</span> of subsonic and supersonic cruise <span class="hlt">aircraft</span> over a wide size range. The product of this task is an even more consistent and robust model for the Footprint/Radius (FOOTPR) code than even the Task 9 model. The model is validated for a wider range of cases and statistically quantified for the various reference facilities. The possible</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070007329','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070007329"><span><span class="hlt">Source</span> <span class="hlt">Noise</span> Modeling Efforts for Fan <span class="hlt">Noise</span> in NASA Research Programs</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Huff, Dennis L.</p> <p>2006-01-01</p> <p>There has been considerable progress made in fan <span class="hlt">noise</span> prediction over the past 15 years. NASA has conducted and sponsored research that has improved both tone and broadband fan <span class="hlt">noise</span> prediction methods. This presentation highlights progress in these areas with emphasis on rotor/stator interaction <span class="hlt">noise</span> <span class="hlt">sources</span>. Tone <span class="hlt">noise</span> predictions are presented for an advanced prediction code called "LINFLUX". Comparisons with data are" included for individual fan duct modes. There has also been considerable work developing new fan broadband <span class="hlt">noise</span> prediction codes and validation data from wind tunnel model tests. Results from several code validation exercises are presented that show improvement of predicted sound power levels. A summary is included with recommendations for future work.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850004526','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850004526"><span>Algorithm for astronomical, point <span class="hlt">source</span>, signal to <span class="hlt">noise</span> ratio calculations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jayroe, R. R.; Schroeder, D. J.</p> <p>1984-01-01</p> <p>An algorithm was developed to simulate the expected signal to <span class="hlt">noise</span> ratios as a function of observation time in the charge coupled device detector plane of an optical telescope located outside the Earth's atmosphere for a signal star, and an optional secondary star, embedded in a uniform cosmic background. By choosing the appropriate input values, the expected point <span class="hlt">source</span> signal to <span class="hlt">noise</span> ratio can be computed for the Hubble Space Telescope using the Wide Field/Planetary Camera science instrument.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004RScI...75.1323R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004RScI...75.1323R"><span>Low flicker-<span class="hlt">noise</span> amplifier for 50 Ω <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rubiola, Enrico; Lardet-Vieudrin, Franck</p> <p>2004-05-01</p> <p>This article analyzes the design of a low-<span class="hlt">noise</span> amplifier intended as the input front-end for the measurement of the low-frequency components (below 10 Hz) of a 50 Ω <span class="hlt">source</span>. Low residual flicker is the main desired performance. This feature can only be appreciated if white <span class="hlt">noise</span> is sufficiently low, and if an appropriate design ensures dc stability. An optimal solution is proposed, in which the low-<span class="hlt">noise</span> and dc-stability features are achieved at a reasonable complexity. Gain is accurate to more than 100 kHz, which makes the amplifier an appealing external front-end for fast Fourier transform (FFT) analyzers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19750041732&hterms=Excess+attenuation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DExcess%2Battenuation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19750041732&hterms=Excess+attenuation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DExcess%2Battenuation"><span>Propagation of <span class="hlt">aircraft</span> <span class="hlt">noise</span> over long distances through the lower atmosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Abrahamson, A. L.</p> <p>1975-01-01</p> <p>Propagation of sound through the lower atmosphere is influenced by numerous factors which are difficult to measure and more difficult to predict. In addition to the well known laboratory observable loss mechanisms of heat conduction, gas transport, and molecular absorption, inhomogeneities in a real atmosphere have significant influence on a propagating sound wave. This study presents a qualitative discussion of different categories of atmospheric inhomogeneity and their individual and combined effects on sound propagation. Subsequently, a field test involving the propagation of <span class="hlt">aircraft</span> <span class="hlt">noise</span> over distances up to 10 miles is described, and a simplified empirical model for 'excess' atmospheric attenuation due to inhomogeneities in the atmosphere is derived from the data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870015369&hterms=phase+noise&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dphase%2Bnoise','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870015369&hterms=phase+noise&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dphase%2Bnoise"><span>Phase <span class="hlt">noise</span> from <span class="hlt">aircraft</span> motion: Compensation and effect on synthetic aperture radar images</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gabriel, Andrew K.; Goldstein, Richard M.</p> <p>1986-01-01</p> <p>Image degradation of airborne SAR imagery caused by phase errors introduced in the received signal by <span class="hlt">aircraft</span> motion is discussed. Mechanical motion has a small bandwidth and does not affect the range signal, where the total echo time is typically 60 microsec. However, since the aperture length can be several seconds, the synthesized azimuth signal can have significant errors of which phase <span class="hlt">noise</span> is the most important. An inertial navigation system can be used to compensate for these errors when processing the images. Calculations to evaluate how much improvement results from compensation are outlined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012APhy...58..404E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012APhy...58..404E"><span>A complex of analytical models for predicting <span class="hlt">noise</span> in an <span class="hlt">aircraft</span> cabin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Efimtsov, B. M.; Lazarev, L. A.</p> <p>2012-07-01</p> <p>A series of analytical calculated models for predicting the <span class="hlt">noise</span> in an <span class="hlt">aircraft</span> cabin is developed: an orthotropic model, a model with discrete frames, a model with discrete stringers, a model with isolated cells, and a model with a cross system of discrete ribs. The analytical solution is constructed on the basis of the method of space harmonic expansion. Vibrations are represented in the form of double trigonometric series. Strict periodicity allows dividing the series into a large number of independent groups, which makes it possible to effectively perform calculations for large fragments of the fuselage in the entire frequency region both for deterministic and random external force fields.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APhy...61..101K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APhy...61..101K"><span>Fan <span class="hlt">noise</span> reduction of an <span class="hlt">aircraft</span> engine by inclining the outlet guide vanes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khaletskiy, Yu. D.; Pochkin, Ya. S.</p> <p>2015-01-01</p> <p>The paper presents the results of an experimental study of the acoustic characteristics of an <span class="hlt">aircraft</span> engine fan in the design of which the outlet guide vanes are leaned in the circumferential direction. It was found that the configuration of the outlet guide with the vanes leaned along the rotation of the rotor leads to fan <span class="hlt">noise</span> reduction with respect to the configuration with outlet guide vanes, and a configuration of the outlet guide with an lean of the vane counterrotation of the rotor wheel leads to its increase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980236838','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980236838"><span>Sound Pressures and Correlations of <span class="hlt">Noise</span> on the Fuselage of a Jet <span class="hlt">Aircraft</span> in Flight</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shattuck, Russell D.</p> <p>1961-01-01</p> <p>Tests were conducted at altitudes of 10,000, 20,000, and 30,000 feet at speeds of Mach 0.4, 0.6, and O.8. It was found that the sound pressure levels on the aft fuselage of a jet <span class="hlt">aircraft</span> in flight can be estimated using an equation involving the true airspeed and the free air density. The cross-correlation coefficient over a spacing of 2.5 feet was generalized with Strouhal number. The spectrum of the <span class="hlt">noise</span> in flight is comparatively flat up to 10,000 cycles per second.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880014849','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880014849"><span>Analytical modeling of the structureborne <span class="hlt">noise</span> path on a small twin-engine <span class="hlt">aircraft</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cole, J. E., III; Stokes, A. Westagard; Garrelick, J. M.; Martini, K. F.</p> <p>1988-01-01</p> <p>The structureborne <span class="hlt">noise</span> path of a six passenger twin-engine <span class="hlt">aircraft</span> is analyzed. Models of the wing and fuselage structures as well as the interior acoustic space of the cabin are developed and used to evaluate sensitivity to structural and acoustic parameters. Different modeling approaches are used to examine aspects of the structureborne path. These approaches are guided by a number of considerations including the geometry of the structures, the frequency range of interest, and the tractability of the computations. Results of these approaches are compared with experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998STIN...0304290R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998STIN...0304290R"><span>Computing the Absorption of Sound by the Atmosphere and its Applicability to <span class="hlt">Aircraft</span> <span class="hlt">Noise</span> Certification</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rickley, E. J.</p> <p>1998-08-01</p> <p>The United States Department of Transportation, John A. Volpe National Transportation Systems Center (Volpe Center), Acoustics Facility, in support of the Federal Aviation Administration's Office of Environment and Energy (AEE), has recently completed a study of a new method for computing atmospheric absorption. This letter report presents the results of the study. Section 1 presents an introduction to the topic of atmospheric absorption as it relates to <span class="hlt">aircraft</span> <span class="hlt">noise</span> certification, along with the objective of the study. Section 2 discusses the evaluation procedure. Section 3 discusses the results of the evaluation. Section 4 and 5 present conclusions and recommendations, respectively.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780013946','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780013946"><span>Experimental and theoretical sound transmission. [reduction of interior <span class="hlt">noise</span> in <span class="hlt">aircraft</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Roskam, J.; Muirhead, V. U.; Smith, H. W.; Durenberger, D. W.</p> <p>1978-01-01</p> <p>The capabilities of the Kansas University- Flight Research Center for investigating panel sound transmission as a step toward the reduction of interior <span class="hlt">noise</span> in general aviation <span class="hlt">aircraft</span> were discussed. Data obtained on panels with holes, on honeycomb panels, and on various panel treatments at normal incidence were documented. The design of equipment for panel transmission loss tests at nonnormal (slanted) sound incidence was described. A comprehensive theory-based prediction method was developed and shows good agreement with experimental observations of the stiffness controlled, the region, the resonance controlled region, and the mass-law region of panel vibration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA098451','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA098451"><span>VLF P-Static <span class="hlt">Noise</span> Reduction In <span class="hlt">Aircraft</span>. Volume I. Current Knowledge.</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1980-09-01</p> <p>dielectric masts with conducting or partially conducting masts--are recommended to eliminate streamer- ing. <span class="hlt">Noise</span> levels produced by corona discharges... DIELECTRIC SURFACES IN THE MICROWAVE FREQUENCY REGION (1-4 GHz) AUTHOR: Cummings, Larry E. Air Force Avionics Lab Wright-Patterson AFB Ohio Technical...NOISEJ3EDUCTION IN <span class="hlt">AIRCRAFT</span> - j p P Volume to Current Knowlde P~ff~gOgn~zo 9.1 Pe9omeng Or lonization Nano end AddesI ---... 1rMU~i~. Avionics</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920016125','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920016125"><span>Interior <span class="hlt">noise</span> prediction methodology: ATDAC theory and validation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mathur, Gopal P.; Gardner, Bryce K.</p> <p>1992-01-01</p> <p>The Acoustical Theory for Design of <span class="hlt">Aircraft</span> Cabins (ATDAC) is a computer program developed to predict interior <span class="hlt">noise</span> levels inside <span class="hlt">aircraft</span> and to evaluate the effects of different <span class="hlt">aircraft</span> configurations on the <span class="hlt">aircraft</span> acoustical environment. The primary motivation for development of this program is the special interior <span class="hlt">noise</span> problems associated with advanced turboprop (ATP) <span class="hlt">aircraft</span> where there is a tonal, low frequency <span class="hlt">noise</span> problem. Prediction of interior <span class="hlt">noise</span> levels requires knowledge of the energy <span class="hlt">sources</span>, the transmission paths, and the relationship between the energy variable and the sound pressure level. The energy <span class="hlt">sources</span> include engine <span class="hlt">noise</span>, both airborne and structure-borne; turbulent boundary layer <span class="hlt">noise</span>; and interior <span class="hlt">noise</span> <span class="hlt">sources</span> such as air conditioner <span class="hlt">noise</span> and auxiliary power unit <span class="hlt">noise</span>. Since propeller and engine <span class="hlt">noise</span> prediction programs are widely available, they are not included in ATDAC. Airborne engine <span class="hlt">noise</span> from any prediction or measurement may be input to this program. This report describes the theory and equations implemented in the ATDAC program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA030657','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA030657"><span><span class="hlt">Aircraft</span> Configuration <span class="hlt">Noise</span> Reduction. Volume 3. Computer Program <span class="hlt">Source</span> Listing</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1976-06-01</p> <p>PKCPALA]ICN IS ULt .m[NC (ti ,IXtA4t7-3 PHBNAC 451 IF( fG0R.NE.J)G;XP=YNO P~3N( 5 WITt(f6,475tlJ (iPT9I=1121),GHP PHBNAL 453 4755 F-LRMA( :x, 22HO ) Gf ClND...BANOS.ABU( . C BCF = THE ARRAY OF BAND CEN\\TER FRECUENCIES. AbSOKP I b C T =AMBIENT TEMPERATURE IN’ DEGREES FARENHEIT ABSUtRP 17 C AdSOt(P 18 C OUTPUT</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhBio...9b6002N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhBio...9b6002N"><span>Isolating intrinsic <span class="hlt">noise</span> <span class="hlt">sources</span> in a stochastic genetic switch</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Newby, Jay M.</p> <p>2012-04-01</p> <p>The stochastic mutual repressor model is analysed using perturbation methods. This simple model of a gene circuit consists of two genes and three promotor states. Either of the two protein products can dimerize, forming a repressor molecule that binds to the promotor of the other gene. When the repressor is bound to a promotor, the corresponding gene is not transcribed and no protein is produced. Either one of the promotors can be repressed at any given time or both can be unrepressed, leaving three possible promotor states. This model is analysed in its bistable regime in which the deterministic limit exhibits two stable fixed points and an unstable saddle, and the case of small <span class="hlt">noise</span> is considered. On small timescales, the stochastic process fluctuates near one of the stable fixed points, and on large timescales, a metastable transition can occur, where fluctuations drive the system past the unstable saddle to the other stable fixed point. To explore how different intrinsic <span class="hlt">noise</span> <span class="hlt">sources</span> affect these transitions, fluctuations in protein production and degradation are eliminated, leaving fluctuations in the promotor state as the only <span class="hlt">source</span> of <span class="hlt">noise</span> in the system. The process without protein <span class="hlt">noise</span> is then compared to the process with weak protein <span class="hlt">noise</span> using perturbation methods and Monte Carlo simulations. It is found that some significant differences in the random process emerge when the intrinsic <span class="hlt">noise</span> <span class="hlt">source</span> is removed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030003692','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030003692"><span>Fan <span class="hlt">Noise</span> <span class="hlt">Source</span> Diagnostic Test Computation of Rotor Wake Turbulence <span class="hlt">Noise</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nallasamy, M.; Envia, E.; Thorp, S. A.; Shabbir, A.</p> <p>2002-01-01</p> <p>An important <span class="hlt">source</span> mechanism of fan broadband <span class="hlt">noise</span> is the interaction of rotor wake turbulence with the fan outlet guide vanes. A broadband <span class="hlt">noise</span> model that utilizes computed rotor flow turbulence from a RANS code is used to predict fan broadband <span class="hlt">noise</span> spectra. The <span class="hlt">noise</span> model is employed to examine the broadband <span class="hlt">noise</span> characteristics of the 22-inch <span class="hlt">Source</span> Diagnostic Test fan rig for which broadband <span class="hlt">noise</span> data were obtained in wind tunnel tests at the NASA Glenn Research Center. A 9-case matrix of three outlet guide vane configurations at three representative fan tip speeds are considered. For all cases inlet and exhaust acoustic power spectra are computed and compared with the measured spectra where possible. In general, the acoustic power levels and shape of the predicted spectra are in good agreement with the measured data. The predicted spectra show the experimentally observed trends with fan tip speed, vane count, and vane sweep. The results also demonstrate the validity of using CFD-based turbulence information for fan broadband <span class="hlt">noise</span> calculations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160001301','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160001301"><span>Autonomous Slat-Cove-Filler Device for Reduction of Aeroacoustic <span class="hlt">Noise</span> Associated with <span class="hlt">Aircraft</span> Systems</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Turner, Travis L. (Inventor); Kidd, Reggie T. (Inventor); Lockard, David P (Inventor); Khorrami, Mehdi R. (Inventor); Streett, Craig L. (Inventor); Weber, Douglas Leo (Inventor)</p> <p>2016-01-01</p> <p>A slat cove filler is utilized to reduce airframe <span class="hlt">noise</span> resulting from deployment of a leading edge slat of an <span class="hlt">aircraft</span> wing. The slat cove filler is preferably made of a super elastic shape memory alloy, and the slat cove filler shifts between stowed and deployed shapes as the slat is deployed. The slat cove filler may be configured such that a separate powered actuator is not required to change the shape of the slat cove filler from its deployed shape to its stowed shape and vice-versa. The outer contour of the slat cove filler preferably follows a profile designed to maintain accelerating flow in the gap between the slat cove filler and wing leading edge to provide for <span class="hlt">noise</span> reduction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26520292','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26520292"><span>The relationship between <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure and day-use visitor survey responses in backcountry areas of national parks.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rapoza, Amanda; Sudderth, Erika; Lewis, Kristin</p> <p>2015-10-01</p> <p>To evaluate the relationship between <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure and the quality of national park visitor experience, more than 4600 visitor surveys were collected at seven backcountry sites in four U.S. national parks simultaneously with calibrated sound level measurements. Multilevel logistic regression was used to estimate parameters describing the relationship among visitor responses, <span class="hlt">aircraft</span> <span class="hlt">noise</span> dose metrics, and mediator variables. For the regression models, survey responses were converted to three dichotomous variables, representing visitors who did or did not experience slightly or more, moderately or more, or very or more annoyance or interference with natural quiet from <span class="hlt">aircraft</span> <span class="hlt">noise</span>. Models with the most predictive power included <span class="hlt">noise</span> dose metrics of sound exposure level, percent time <span class="hlt">aircraft</span> were audible, and percentage energy due to helicopters and fixed-wing propeller <span class="hlt">aircraft</span>. These models also included mediator variables: visitor ratings of the "importance of calmness, peace and tranquility," visitor group composition (adults or both adults and children), first visit to the site, previously taken an air tour, and participation in bird-watching or interpretive talks. The results complement and extend previous research conducted in frontcountry areas and will inform evaluations of air tour <span class="hlt">noise</span> effects on visitors to national parks and remote wilderness sites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22280610','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22280610"><span>Perceptual interaction of the harmonic <span class="hlt">source</span> and <span class="hlt">noise</span> in voice.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kreiman, Jody; Gerratt, Bruce R</p> <p>2012-01-01</p> <p>Although the amount of inharmonic energy (<span class="hlt">noise</span>) present in a human voice is an important determinant of vocal quality, little is known about the perceptual interaction between harmonic and inharmonic aspects of the voice <span class="hlt">source</span>. This paper reports three experiments investigating this issue. Results indicate that perception of the harmonic slope and of <span class="hlt">noise</span> levels are both influenced by complex interactions between the spectral shape and relative levels of harmonic and <span class="hlt">noise</span> energy in the voice <span class="hlt">source</span>. Just-noticeable differences (JNDs) for the <span class="hlt">noise</span>-to-harmonics ratio (NHR) varied significantly with the NHR and harmonic spectral slope, but NHR had no effect on JNDs for NHR when harmonic slopes were steepest, and harmonic slope had no effect when NHRs were highest. Perception of changes in the harmonic <span class="hlt">source</span> slope depended on NHR and on the harmonic <span class="hlt">source</span> slope: JNDs increased when spectra rolled off steeply, with this effect in turn depending on NHR. Finally, all effects were modulated by the shape of the <span class="hlt">noise</span> spectrum. It thus appears that, beyond masking, understanding perception of individual parameters requires knowledge of the acoustic context in which they function, consistent with the view that voices are integral patterns that resist decomposition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPA....7b5014M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPA....7b5014M"><span>Developing general acoustic model for <span class="hlt">noise</span> <span class="hlt">sources</span> and parameters estimation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Madoliat, Reza; Nouri, Nowrouz Mohammad; Rahrovi, Ali</p> <p>2017-02-01</p> <p><span class="hlt">Noise</span> measured at various points around the environment can be evaluated by a series of acoustic <span class="hlt">sources</span>. Acoustic <span class="hlt">sources</span> with wide surface can be broken down in fluid environment using some smaller acoustic <span class="hlt">sources</span>. The aim of this study is to make a model to indicate the type, number, direction, position and strength of these <span class="hlt">sources</span> in a way that the main sound and the sound of equivalent <span class="hlt">sources</span> match together in an acceptable way. When position and direction of the <span class="hlt">source</span> is given, the strength of the <span class="hlt">source</span> can be found using inverse method. On the other hand, considering the non-uniqueness of solution in inverse method, a different acoustic strength is obtained for the <span class="hlt">sources</span> if different positions are selected. Selecting an arrangement of general <span class="hlt">source</span> and using the optimization algorithm, the least possible mismatch between the main sound and the sound of equivalent <span class="hlt">sources</span> can be achieved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870014728','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870014728"><span>Annoyance response to simulated advanced turboprop <span class="hlt">aircraft</span> interior <span class="hlt">noise</span> containing tonal beats</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Leatherwood, Jack D.</p> <p>1987-01-01</p> <p>A study is done to investigate the effects on subjective annoyance of simulated advanced turboprop (ATP) interior <span class="hlt">noise</span> environments containing tonal beats. The simulated environments consisted of low-frequency tones superimposed on a turbulent-boundary-layer <span class="hlt">noise</span> spectrum. The variables used in the study included propeller tone frequency (100 to 250 Hz), propeller tone levels (84 to 105 dB), and tonal beat frequency (0 to 1.0 Hz). Results indicated that propeller tones within the simulated ATP environment resulted in increased annoyance response that was fully predictable in terms of the increase in overall sound pressure level due to the tones. Implications for ATP <span class="hlt">aircraft</span> include the following: (1) the interior <span class="hlt">noise</span> environment with propeller tones is more annoying than an environment without tones if the tone is present at a level sufficient to increase the overall sound pressure level; (2) the increased annoyance due to the fundamental propeller tone frequency without harmonics is predictable from the overall sound pressure level; and (3) no additional <span class="hlt">noise</span> penalty due to the perception of single discrete-frequency tones and/or beats was observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21877795','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21877795"><span>A first-principles model for estimating the prevalence of annoyance with <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fidell, Sanford; Mestre, Vincent; Schomer, Paul; Berry, Bernard; Gjestland, Truls; Vallet, Michel; Reid, Timothy</p> <p>2011-08-01</p> <p>Numerous relationships between <span class="hlt">noise</span> exposure and transportation <span class="hlt">noise</span>-induced annoyance have been inferred by curve-fitting methods. The present paper develops a different approach. It derives a systematic relationship by applying an a priori, first-principles model to the findings of forty three studies of the annoyance of aviation <span class="hlt">noise</span>. The rate of change of annoyance with day-night average sound level (DNL) due to <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure was found to closely resemble the rate of change of loudness with sound level. The agreement of model predictions with the findings of recent curve-fitting exercises (cf. Miedma and Vos, 1998) is noteworthy, considering that other analyses have relied on different analytic methods and disparate data sets. Even though annoyance prevalence rates within individual communities consistently grow in proportion to duration-adjusted loudness, variability in annoyance prevalence rates across communities remains great. The present analyses demonstrate that 1) community-specific differences in annoyance prevalence rates can be plausibly attributed to the joint effect of acoustic and non-DNL related factors and (2) a simple model can account for the aggregate influences of non-DNL related factors on annoyance prevalence rates in different communities in terms of a single parameter expressed in DNL units-a "community tolerance level."</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3734456','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3734456"><span>An Epidemiological Prospective Study of Children’s Health and Annoyance Reactions to <span class="hlt">Aircraft</span> <span class="hlt">Noise</span> Exposure in South Africa</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Seabi, Joseph</p> <p>2013-01-01</p> <p>The purpose of this study was to investigate health and annoyance reactions to change in chronic exposure to <span class="hlt">aircraft</span> <span class="hlt">noise</span> on a sample of South African children. It was the intention of this study to examine if effects of <span class="hlt">noise</span> on health and annoyance can be demonstrated. If so, whether such effects persist over time, or whether such effects are reversible after the cessation of exposure to <span class="hlt">noise</span>. A cohort of 732 children with a mean age of 11.1 (range = 8–14) participated at baseline measurements in Wave 1 (2009), and 649 (mean age = 12.3; range = 9–15) and 174 (mean age = 13.3; range = 10–16) children were reassessed in Wave 2 (2010) and Wave 3 (2011) after the relocation of the airport, respectively. The findings revealed that the children who were exposed to chronic <span class="hlt">aircraft</span> <span class="hlt">noise</span> continued to experience significantly higher annoyance than their counterparts in all the waves at school, and only in Wave 1 and Wave 2 at home. <span class="hlt">Aircraft</span> <span class="hlt">noise</span> exposure did not have adverse effects on the children’s self-reported health outcomes. Taken together, these findings suggest that chronic exposure to <span class="hlt">aircraft</span> <span class="hlt">noise</span> may have a lasting impact on children’s annoyance, but not on their subjective health rating. This is one of the first longitudinal studies of this nature in the African continent to make use of an opportunity resulting from the relocation of airport. PMID:23823713</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23823713','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23823713"><span>An epidemiological prospective study of children's health and annoyance reactions to <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure in South Africa.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Seabi, Joseph</p> <p>2013-07-03</p> <p>The purpose of this study was to investigate health and annoyance reactions to change in chronic exposure to <span class="hlt">aircraft</span> <span class="hlt">noise</span> on a sample of South African children. It was the intention of this study to examine if effects of <span class="hlt">noise</span> on health and annoyance can be demonstrated. If so, whether such effects persist over time, or whether such effects are reversible after the cessation of exposure to <span class="hlt">noise</span>. A cohort of 732 children with a mean age of 11.1 (range = 8-14) participated at baseline measurements in Wave 1 (2009), and 649 (mean age = 12.3; range = 9-15) and 174 (mean age = 13.3; range = 10-16) children were reassessed in Wave 2 (2010) and Wave 3 (2011) after the relocation of the airport, respectively. The findings revealed that the children who were exposed to chronic <span class="hlt">aircraft</span> <span class="hlt">noise</span> continued to experience significantly higher annoyance than their counterparts in all the waves at school, and only in Wave 1 and Wave 2 at home. <span class="hlt">Aircraft</span> <span class="hlt">noise</span> exposure did not have adverse effects on the children's self-reported health outcomes. Taken together, these findings suggest that chronic exposure to <span class="hlt">aircraft</span> <span class="hlt">noise</span> may have a lasting impact on children's annoyance, but not on their subjective health rating. This is one of the first longitudinal studies of this nature in the African continent to make use of an opportunity resulting from the relocation of airport.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040073459','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040073459"><span>Investigation of Volumetric <span class="hlt">Sources</span> in Airframe <span class="hlt">Noise</span> Simulations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Casper, Jay H.; Lockard, David P.; Khorrami, Mehdi R.; Streett, Craig L.</p> <p>2004-01-01</p> <p>Hybrid methods for the prediction of airframe <span class="hlt">noise</span> involve a simulation of the near field flow that is used as input to an acoustic propagation formula. The acoustic formulations discussed herein are those based on the Ffowcs Williams and Hawkings equation. Some questions have arisen in the published literature in regard to an apparently significant dependence of radiated <span class="hlt">noise</span> predictions on the location of the integration surface used in the solution of the Ffowcs Williams and Hawkings equation. These differences in radiated <span class="hlt">noise</span> levels are most pronounced between solid-body surface integrals and off-body, permeable surface integrals. Such differences suggest that either a non-negligible volumetric <span class="hlt">source</span> is contributing to the total radiation or the input flow simulation is suspect. The focus of the current work is the issue of internal consistency of the flow calculations that are currently used as input to airframe <span class="hlt">noise</span> predictions. The case study for this research is a computer simulation for a three-element, high-lift wing profile during landing conditions. The <span class="hlt">noise</span> radiated from this flow is predicted by a two-dimensional, frequency-domain formulation of the Ffowcs Williams and Hawkings equation. Radiated sound from volumetric <span class="hlt">sources</span> is assessed by comparison of a permeable surface integration with the sum of a solid-body surface integral and a volume integral. The separate <span class="hlt">noise</span> predictions are found in good agreement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/272851','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/272851"><span>Effects of simulated jet <span class="hlt">aircraft</span> <span class="hlt">noise</span> on heart rate and behavior of desert ungulates</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Weisenberger, M.E.; Krausman, P.R.; Wallace, M.C.</p> <p>1996-01-01</p> <p>Many landscapes underlying military designated air spaces have been established as national parks, wildlife refuges, or wilderness areas. The juxtaposition of public, wilderness, and military uses has led to questions of compatibility between <span class="hlt">aircraft</span> and wildlife. We evaluated the effects of simulated low-altitude jet <span class="hlt">aircraft</span> <span class="hlt">noise</span> on the behavior and heart rate of captive desert mule deer (n = 6) and mountain sheep (n - 5). We measured heart rate and behavior related to the number of simulated overflights (n = 112 overflights/season) during 3 seasons. The heart rates of ungulates increased related to dB levels during simulated overflights (P {le} 0.05), but they returned to pre-disturbance levels in 60-180 seconds. Animal behavior also changed during overflights but returned to pre-disturbance condition in {le}252 seconds (P {le} 0.005). All animal responses decreased with increased exposure suggesting that they habituated to simulated sound levels of low-altitude <span class="hlt">aircraft</span>. 43 refs., 5 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900015540','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900015540"><span>En route <span class="hlt">noise</span>: NASA propfan test <span class="hlt">aircraft</span> (corrected data - simplified procedure)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rickley, E. J.</p> <p>1990-01-01</p> <p>Surface <span class="hlt">noise</span> measurements were made during a joint National Aeronautics and Space Administration (NASA) and Federal Aviation Administration (FAA) program to study the high-altitude, low-frequency acoustic <span class="hlt">noise</span> propagation characteristics of the Advanced Turboprop (propfan) <span class="hlt">Aircraft</span>. The measurements were made on October 26-31, 1987 in Huntsville, Alabama and on April 3-13, 1989 at the White Sands Missile Range (WSMR), New Mexico. To effectively compare flight-to-flight data as received on the ground, the procedures and practices of Federal Air Regulation (FAR) Part 36 were used as a guide in adjusting the measured ground data at the time of LA(sub MAX) to a set of reference conditions. After the data for each event were processed using slow detector characteristics, the data record at LA(sub MAX) was then identified and the coordinates of the <span class="hlt">aircraft</span> at the time of emission were calculated, taking into account atmospheric refraction effects. The effects of atmospheric absorption through the test day and reference day atmosphere were also taken into account and the 1/3-octave data were adjusted accordingly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.S51E..02S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.S51E..02S"><span>Seismic <span class="hlt">noise</span> frequency dependent P and S wave <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stutzmann, E.; Schimmel, M.; Gualtieri, L.; Farra, V.; Ardhuin, F.</p> <p>2013-12-01</p> <p>Seismic <span class="hlt">noise</span> in the period band 3-10 sec is generated in the oceans by the interaction of ocean waves. <span class="hlt">Noise</span> signal is dominated by Rayleigh waves but body waves can be extracted using a beamforming approach. We select the TAPAS array deployed in South Spain between June 2008 and September 2009 and we use the vertical and horizontal components to extract <span class="hlt">noise</span> P and S waves, respectively. Data are filtered in narrow frequency bands and we select beam azimuths and slownesses that correspond to the largest continuous <span class="hlt">sources</span> per day. Our procedure automatically discard earthquakes which are localized during short time durations. Using this approach, we detect many more <span class="hlt">noise</span> P-waves than S-waves. <span class="hlt">Source</span> locations are determined by back-projecting the detected slowness/azimuth. P and S waves are generated in nearby areas and both <span class="hlt">source</span> locations are frequency dependent. Long period <span class="hlt">sources</span> are dominantly in the South Atlantic and Indian Ocean whereas shorter period <span class="hlt">sources</span> are rather in the North Atlantic Ocean. We further show that the detected S-waves are dominantly Sv-waves. We model the observed body waves using an ocean wave model that takes into account all possible wave interactions including coastal reflection. We use the wave model to separate direct and multiply reflected phases for P and S waves respectively. We show that in the South Atlantic the complex <span class="hlt">source</span> pattern can be explained by the existence of both coastal and pelagic <span class="hlt">sources</span> whereas in the North Atlantic most body wave <span class="hlt">sources</span> are pelagic. For each detected <span class="hlt">source</span>, we determine the equivalent <span class="hlt">source</span> magnitude which is compared to the model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880053218&hterms=james+stewart&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Djames%2Bstewart','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880053218&hterms=james+stewart&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Djames%2Bstewart"><span><span class="hlt">Noise</span> tube <span class="hlt">sources</span> for the far IR and millimeter region</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moller, K. D.; Zoeller, R. G.; Ugras, N. G.; Zablocky, P.; Heaney, James B.; Stewart, K. P.; Boucarut, R. A.</p> <p>1988-01-01</p> <p>The radiant output of a <span class="hlt">noise</span> tube designed for the 90-140-GHz (3.3-2.1-mm) frequency range has been compared with that from mercury lamps over the wavelength region from 0.4 to about 6 mm. Lamellar grating and Michelson Fourier transform spectrometers were used in conjunction with He cooled bolometers of NEP from 10 to the -12th to 10 to the -14th W/sq rt H2 to measure relative spectral irradiance. With this instrumental arrangement, the radiant power emitted by the <span class="hlt">noise</span> tube was observed to be less than that from a mercury lamp, at least to a 3-mm wavelength, but it produced less <span class="hlt">source</span> <span class="hlt">noise</span> than an ac operated mercury lamp. When the <span class="hlt">noise</span> tube operating current was reduced, the spectral irradiance peak shifted to longer wavelengths.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/814835','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/814835"><span>Review of Subcritical <span class="hlt">Source</span>-Driven <span class="hlt">Noise</span> Analysis Measurements</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Valentine, T.E.</p> <p>1999-11-24</p> <p>Subcritical <span class="hlt">source</span>-driven <span class="hlt">noise</span> measurements are simultaneous Rossi-{alpha} and randomly pulsed neutron measurements that provide measured quantities that can be related to the subcritical neutron multiplication factor. In fact, subcritical <span class="hlt">source</span>-driven <span class="hlt">noise</span> measurements should be performed in lieu of Rossi-{alpha} measurements because of the additional information that is obtained from <span class="hlt">noise</span> measurements such as the spectral ratio and the coherence functions. The basic understanding of <span class="hlt">source</span>-driven <span class="hlt">noise</span> analysis measurements can be developed from a point reactor kinetics model to demonstrate how the measured quantities relate to the subcritical neutron multiplication factor. More elaborate models can also be developed using a generalized stochastic model. These measurements can be simulated using Monte Carlo codes to determine the subcritical neutron multiplication factor or to determine the sensitivity of calculations to nuclear cross section data. The interpretation of the measurement using a Monte Carlo method is based on a perturbation model for the relationship between the spectral ratio and the subcritical neutron multiplication factor. The subcritical <span class="hlt">source</span>-driven <span class="hlt">noise</span> measurement has advantages over other subcritical measurement methods in that reference measurements at delayed critical are not required for interpreting the measurements. Therefore, benchmark or in-situ subcritical measurements can be performed outside a critical experiment facility. Furthermore, a certain ratio of frequency spectra has been shown to be independent of detection efficiency thereby making the measurement more robust and unaffected by drifts or changes in instrumentation during the measurement. Criteria have been defined for application of this measurement method for benchmarks and in-situ subcritical measurements. An extension of the <span class="hlt">source</span>-driven subcritical <span class="hlt">noise</span> measurement has also been discussed that eliminates the few technical challenges for in-situ applications.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JSV...333.1356L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JSV...333.1356L"><span>Propeller sheet cavitation <span class="hlt">noise</span> <span class="hlt">source</span> modeling and inversion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Keunhwa; Lee, Jaehyuk; Kim, Dongho; Kim, Kyungseop; Seong, Woojae</p> <p>2014-02-01</p> <p>Propeller sheet cavitation is the main contributor to high level of <span class="hlt">noise</span> and vibration in the after body of a ship. Full measurement of the cavitation-induced hull pressure over the entire surface of the affected area is desired but not practical. Therefore, using a few measurements on the outer hull above the propeller in a cavitation tunnel, empirical or semi-empirical techniques based on physical model have been used to predict the hull-induced pressure (or hull-induced force). In this paper, with the analytic <span class="hlt">source</span> model for sheet cavitation, a multi-parameter inversion scheme to find the positions of <span class="hlt">noise</span> <span class="hlt">sources</span> and their strengths is suggested. The inversion is posed as a nonlinear optimization problem, which is solved by the optimization algorithm based on the adaptive simplex simulated annealing algorithm. Then, the resulting hull pressure can be modeled with boundary element method from the inverted cavitation <span class="hlt">noise</span> <span class="hlt">sources</span>. The suggested approach is applied to the hull pressure data measured in a cavitation tunnel of the Samsung Heavy Industry. Two monopole <span class="hlt">sources</span> are adequate to model the propeller sheet cavitation <span class="hlt">noise</span>. The inverted <span class="hlt">source</span> information is reasonable with the cavitation dynamics of the propeller and the modeled hull pressure shows good agreement with cavitation tunnel experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960045293','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960045293"><span>Comparison of the Performance of <span class="hlt">Noise</span> Metrics as Predictions of the Annoyance of Stage 2 and Stage 3 <span class="hlt">Aircraft</span> Overflights</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pearsons, Karl S.; Howe, Richard R.; Sneddon, Matthew D.; Fidell, Sanford</p> <p>1996-01-01</p> <p>Thirty audiometrically screened test participants judged the relative annoyance of two comparison (variable level) and thirty-four standard (fixed level) signals in an adaptive paired comparison psychoacoustic study. The signal ensemble included both FAR Part 36 Stage 2 and 3 <span class="hlt">aircraft</span> overflights, as well as synthesized <span class="hlt">aircraft</span> <span class="hlt">noise</span> signatures and other non-<span class="hlt">aircraft</span> signals. All test signals were presented for judgment as heard indoors, in the presence of continuous background <span class="hlt">noise</span>, under free-field listening conditions in an anechoic chamber. Analyses of the performance of 30 <span class="hlt">noise</span> metrics as predictors of these annoyance judgments confirmed that the more complex metrics were generally more accurate and precise predictors than the simpler methods. EPNL was somewhat less accurate and precise as a predictor of the annoyance judgments than a duration-adjusted variant of Zwicker's Loudness Level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4918658','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4918658"><span>Is there an association between <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure and the incidence of hypertension? A meta-analysis of 16784 participants</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Huang, Di; Song, XuPing; Cui, Qi; Tian, Jinhui; Wang, Quan; Yang, Kehu</p> <p>2015-01-01</p> <p>To determine if <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure causes an increased incidence of hypertension among residents near airports. We conducted a meta-analysis of observational studies to evaluate the association between <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure and the incidence of hypertension. PubMed, Embase, Web of Science, the Cochrane Library, and the Chinese Biomedical Literature Database were searched without any restrictions. Odds ratios (ORs) with 95% confidence intervals (CIs) were extracted. The pooled ORs were calculated using both the fixed effects model and random effects model. All analyses were performed using STATA version 12.0 software (Stata Corporation, College Station, TX, USA). We examined five studies, comprising a total of 16,784 residents. The overall OR for hypertension in residents with <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure was 1.63 (95% CI, 1.14-2.33), and one of our included studies showed that there was no evidence that <span class="hlt">aircraft</span> <span class="hlt">noise</span> is a risk factor for hypertension in women. According to our subgroup analysis, the summary OR for the incidence was 1.31 (95% CI, 0.85-2.02) with I2 of 80.7% in women and 1.36 (95% CI, 1.15-1.60) with moderate heterogeneity in men. The pooled OR for the incidence of hypertension in residents aged over 55 years and under 55 years was 1.66 (95% CI, 1.21-2.27) with no heterogeneity and 1.78 (95% CI, 1.33-2.39) with I2 of 29.4%, respectively. The present meta-analysis suggests that <span class="hlt">aircraft</span> <span class="hlt">noise</span> could contribute to the prevalence of hypertension, but the evidence for a relationship between <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure and hypertension is still inconclusive because of limitations in study populations, exposure characterization, and adjustment for important confounders. PMID:25774612</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25774612','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25774612"><span>Is there an association between <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure and the incidence of hypertension? A meta-analysis of 16784 participants.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Huang, Di; Song, XuPing; Cui, Qi; Tian, Jinhui; Wang, Quan; Yang, Kehu</p> <p>2015-01-01</p> <p>To determine if <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure causes an increased incidence of hypertension among residents near airports. We conducted a meta-analysis of observational studies to evaluate the association between <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure and the incidence of hypertension. PubMed, Embase, Web of Science, the Cochrane Library, and the Chinese Biomedical Literature Database were searched without any restrictions. Odds ratios (ORs) with 95% confidence intervals (CIs) were extracted. The pooled ORs were calculated using both the fixed effects model and random effects model. All analyses were performed using STATA version 12.0 software (Stata Corporation, College Station, TX, USA). We examined five studies, comprising a total of 16,784 residents. The overall OR for hypertension in residents with <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure was 1.63 (95% CI, 1.14-2.33), and one of our included studies showed that there was no evidence that <span class="hlt">aircraft</span> <span class="hlt">noise</span> is a risk factor for hypertension in women. According to our subgroup analysis, the summary OR for the incidence was 1.31 (95% CI, 0.85-2.02) with I2 of 80.7% in women and 1.36 (95% CI, 1.15-1.60) with moderate heterogeneity in men. The pooled OR for the incidence of hypertension in residents aged over 55 years and under 55 years was 1.66 (95% CI, 1.21-2.27) with no heterogeneity and 1.78 (95% CI, 1.33-2.39) with I2 of 29.4%, respectively. The present meta-analysis suggests that <span class="hlt">aircraft</span> <span class="hlt">noise</span> could contribute to the prevalence of hypertension, but the evidence for a relationship between <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure and hypertension is still inconclusive because of limitations in study populations, exposure characterization, and adjustment for important confounders.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010RScI...81f4706W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010RScI...81f4706W"><span>A battery-based, low-<span class="hlt">noise</span> voltage <span class="hlt">source</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wagner, Anke; Sturm, Sven; Schabinger, Birgit; Blaum, Klaus; Quint, Wolfgang</p> <p>2010-06-01</p> <p>A highly stable, low-<span class="hlt">noise</span> voltage <span class="hlt">source</span> was designed to improve the stability of the electrode bias voltages of a Penning trap. To avoid excess <span class="hlt">noise</span> and ground loops, the voltage <span class="hlt">source</span> is completely independent of the public electric network and uses a 12 V car battery to generate output voltages of ±15 and ±5 V. First, the dc supply voltage is converted into ac-voltage and gets amplified. Afterwards, the signal is rectified, filtered, and regulated to the desired output value. Each channel can deliver up to 1.5 A. The current as well as the battery voltage and the output voltages can be read out via a universal serial bus (USB) connection for monitoring purposes. With the presented design, a relative voltage stability of 7×10-7 over 6.5 h and a <span class="hlt">noise</span> level equal or smaller than 30 nV/√Hz is achieved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20590260','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20590260"><span>A battery-based, low-<span class="hlt">noise</span> voltage <span class="hlt">source</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wagner, Anke; Sturm, Sven; Schabinger, Birgit; Blaum, Klaus; Quint, Wolfgang</p> <p>2010-06-01</p> <p>A highly stable, low-<span class="hlt">noise</span> voltage <span class="hlt">source</span> was designed to improve the stability of the electrode bias voltages of a Penning trap. To avoid excess <span class="hlt">noise</span> and ground loops, the voltage <span class="hlt">source</span> is completely independent of the public electric network and uses a 12 V car battery to generate output voltages of +/-15 and +/-5 V. First, the dc supply voltage is converted into ac-voltage and gets amplified. Afterwards, the signal is rectified, filtered, and regulated to the desired output value. Each channel can deliver up to 1.5 A. The current as well as the battery voltage and the output voltages can be read out via a universal serial bus (USB) connection for monitoring purposes. With the presented design, a relative voltage stability of 7 x 10(-7) over 6.5 h and a <span class="hlt">noise</span> level equal or smaller than 30 nV/square root(Hz) is achieved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT........58O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT........58O"><span>Investigation of <span class="hlt">noise</span> <span class="hlt">sources</span> and propagation in external gear pumps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Opperwall, Timothy J.</p> <p></p> <p>Oil hydraulics is widely accepted as the best technology for transmitting power in many engineering applications due to its advantages in power density, control, layout flexibility, and efficiency. Due to these advantages, hydraulic systems are present in many different applications including construction, agriculture, aerospace, automotive, forestry, medical, and manufacturing, just to identify a few. Many of these applications involve the systems in close proximity to human operators and passengers where <span class="hlt">noise</span> is one of the main constraints to the acceptance and spread of this technology. As a key component in power transfer, displacement machines can be major <span class="hlt">sources</span> of <span class="hlt">noise</span> in hydraulic systems. Thus, investigation into the <span class="hlt">sources</span> of <span class="hlt">noise</span> and discovering strategies to reduce <span class="hlt">noise</span> is a key part of applying fluid power systems to a wider range of applications, as well as improving the performance of current hydraulic systems. The present research aims to leverage previous efforts and develop new models and experimental techniques in the topic of <span class="hlt">noise</span> generation caused by hydrostatic units. This requires challenging and surpassing current accepted methods in the understanding of <span class="hlt">noise</span> in fluid power systems. This research seeks to expand on the previous experimental and modeling efforts by directly considering the effect that system and component design changes apply on the total sound power and the sound frequency components emitted from displacement machines and the attached lines. The case of external gear pumps is taken as reference for a new model to understand the generation and transmission of <span class="hlt">noise</span> from the <span class="hlt">sources</span> out to the environment. The lumped parameter model HYGESim (HYdraulic GEar machine Simulator) was expanded to investigate the dynamic forces on the solid bodies caused by the pump operation and to predict interactions with the attached system. Vibration and sound radiation were then predicted using a combined finite element and boundary</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740015236','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740015236"><span>Program on ground test of modified quiet, clean, JT3D and JT8D turbofan engines in their respective nacelles. [modification of Boeing 707, 727, and 737 <span class="hlt">aircraft</span> for <span class="hlt">aircraft</span> <span class="hlt">noise</span> reduction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1973-01-01</p> <p>A program to reduce the community <span class="hlt">noise</span> levels of commercial jet <span class="hlt">aircraft</span> is summarized. The program objective is the development of three acoustically treated nacelle configurations for the 707, 727, and 737 series <span class="hlt">aircraft</span> to provide maximum <span class="hlt">noise</span> reduction with minimum performance loss, modification requirements, and economic impact. The preliminary design, model testing, data analyses, and economic studies of proposed nacelle configurations are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19770010664','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770010664"><span>A comparison of a laboratory and field study of annoyance and acceptability of <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposures. [human reactions and tolerance</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Borsky, P. N.</p> <p>1977-01-01</p> <p>Residents living in close, middle and distant areas from JFK Airport were included in a field interview and laboratory study. Judgments were made of simulated <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposures of comparable community indoor <span class="hlt">noise</span> levels and mixes of <span class="hlt">aircraft</span>. Each group of subjects judged the levels of <span class="hlt">noise</span> typical for its distance area. Four different numbers of flyovers were tested: less than average for each area, the approximate average, the peak number, or worst day, and above peak number. The major findings are: (1) the reported integrated field annoyance is best related to the annoyance reported for the simulated approximate worst day exposure in the laboratory; (2) annoyance is generally less when there are fewer <span class="hlt">aircraft</span> flyovers, and the subject has less fear of crashes and more favorable attitudes toward airplanes; (3) beliefs in harmful health effects and misfeasance by operators of <span class="hlt">aircraft</span> are also highly correlated with fear and <span class="hlt">noise</span> annoyance; (4) in direct retrospective comparisons of number of flights, <span class="hlt">noise</span> levels and annoyance, subjects more often said the worst day laboratory exposured more like their usual home environments; and (5) subjects do not expect an annoyance-free environment. Half of the subjects can accept an annoyance level of 5 to 6 from a possible annoyance range of 0 to 9, 28% can live with an annoyance intensity of 7, and only 5% can accept the top scores of 8 to 9.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002ASAJ..111.2336H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002ASAJ..111.2336H"><span>Identification and classification of <span class="hlt">noise</span> <span class="hlt">sources</span> in a chain conveyor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Homer, John P.; Vipperman, Jeffrey S.; Reeves, Efrem R.</p> <p>2002-05-01</p> <p><span class="hlt">Noise</span> induced hearing loss (NIHL) is one of the most significant disabilities of workers in the mining industry. In response, the National Institute of Occupational Safety and Health (NIOSH) is conducting a study associated with mining equipment. This study outlines the analysis of a chain conveyor. Band-limited accelerometer, sound-intensity, far-field and near-field microphone measurements were taken along the conveyor section. The sound intensity measurements were used to identify areas with high <span class="hlt">noise</span> as well as to calculate and 1/3-octave sound power levels. The total sound power results were used to classify the dominant <span class="hlt">noise</span> <span class="hlt">sources</span> where the 1/3-octave sound power results were used to identify the most contributive frequency bands to the overall <span class="hlt">noise</span> of the system. Coherence analysis was performed between accelerometer and microphone measurements to identify structure-borne and air-borne <span class="hlt">noise</span> paths of the system. Summary results from the analysis include recommendations for transmission control and damping devices and their ability to reduce <span class="hlt">noise</span> to regulatory acceptable levels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950008473','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950008473"><span>The effect of <span class="hlt">aircraft</span> speed on the penetration of sonic boom <span class="hlt">noise</span> into a flat ocean</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sparrow, Victor W.</p> <p>1994-01-01</p> <p>As U.S. <span class="hlt">aircraft</span> manufacturers now have focused their HSCT efforts on overwater supersonic flight, a great deal more must be known about sonic booms propagating overwater and interacting with the ocean. For example, it is thought that atmospheric turbulence effects are often much less severe over water than over land. Another important aspect of the overwater flight problems is the penetration of the sonic boom <span class="hlt">noise</span> into the ocean, where there could be an environmental impact on sea life. This talk will present a brief review on the penetration of sonic boom <span class="hlt">noise</span> into a large body of water with a flat surface. It has been determined recently that faster supersonic speeds imply greater penetration of sonic boom <span class="hlt">noise</span> into the ocean. The new theory is derived from the original Sawyers paper and from the knowledge that for level flight a boom's duration is proportional to the quantity M/(M(exp 2)-1)(exp 3/8) where M is the Mach number. It is found that for depths of 10 m or less, the peak SPL varies less than 6 dB over a wide range of M. For greater depths, 100 m for example, increased Mach numbers may increase the SPL by 15 dB or more.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFD.D4009R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFD.D4009R"><span>Towards the characterization of <span class="hlt">noise</span> <span class="hlt">sources</span> in a supersonic three-stream jet using advanced analysis tools</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruscher, Christopher; Gogineni, Sivaram</p> <p>2016-11-01</p> <p>Strict <span class="hlt">noise</span> regulation set by governing bodies currently make supersonic commercial aviation impractical. One of the many challenges that exist in developing practical supersonic commercial <span class="hlt">aircraft</span> is the <span class="hlt">noise</span> produced by the engine's exhaust jet. A promising method of jet <span class="hlt">noise</span> reduction for supersonic applications is through the addition of extra exhaust streams. Data for an axisymmetric three-stream nozzle were generated using the Naval Research Laboratory's JENRE code. This data will be compared to experimental results obtained by NASA for validation purposes. Once the simulation results show satisfactory agreement to the experiments, advanced analysis tools will be applied to the simulation data to characterize potential <span class="hlt">noise</span> <span class="hlt">sources</span>. The tools to be applied include methods that are based on proper orthogonal decomposition, wavelet decomposition, and stochastic estimation. Additionally, techniques such as empirical mode decomposition and momentum potential theorem will be applied to the data as well.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4080526','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4080526"><span>Long-Term <span class="hlt">Aircraft</span> <span class="hlt">Noise</span> Exposure and Body Mass Index, Waist Circumference, and Type 2 Diabetes: A Prospective Study</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hilding, Agneta; Pyko, Andrei; Bluhm, Gösta; Pershagen, Göran; Östenson, Claes-Göran</p> <p>2014-01-01</p> <p>Background: Long-term <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure may increase the risk of cardiovascular disease, but no study has investigated chronic effects on the metabolic system. Objectives: The aim of this study was to investigate effects of long-term <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure on body mass index (BMI), waist circumference, and type 2 diabetes. Furthermore, we explored the modifying effects of sleep disturbance. Methods: This prospective cohort study of residents of Stockholm County, Sweden, followed 5,156 participants with normal baseline oral glucose tolerance tests (OGTT) for up to 10 years. Exposure to <span class="hlt">aircraft</span> <span class="hlt">noise</span> was estimated based on residential history. Information on outcomes and confounders was obtained from baseline and follow-up surveys and examinations, and participants who developed prediabetes or type 2 diabetes were identified by self-reported physician diagnosis or OGTT at follow-up. Adjusted associations were assessed by linear, logistic, and random-effects models. Results: The mean (± SD) increases in BMI and waist circumference during follow-up were 1.09 ± 1.97 kg/m2 and 4.39 ± 6.39 cm, respectively. The cumulative incidence of prediabetes and type 2 diabetes was 8% and 3%, respectively. Based on an ordinal <span class="hlt">noise</span> variable, a 5-dB(A) increase in <span class="hlt">aircraft</span> <span class="hlt">noise</span> was associated with a greater increase in waist circumference of 1.51 cm (95% CI: 1.13, 1.89), fully adjusted. This association appeared particularly strong among those who did not change their home address during the study period, which may be a result of lower exposure misclassification. However, no clear associations were found for BMI or type 2 diabetes. Furthermore, sleep disturbances did not appear to modify the associations with <span class="hlt">aircraft</span> <span class="hlt">noise</span>. Conclusions: Long-term <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure may be linked to metabolic outcomes, in particular increased waist circumference. Citation: Eriksson C, Hilding A, Pyko A, Bluhm G, Pershagen G, Östenson CG. 2014. Long-term <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030107649','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030107649"><span><span class="hlt">Aircraft</span> Engine <span class="hlt">Noise</span> Scattering By Fuselage and Wings: A Computational Approach</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stanescu, D.; Hussaini, M. Y.; Farassat, F.</p> <p>2003-01-01</p> <p>The paper presents a time-domain method for computation of sound radiation from <span class="hlt">aircraft</span> engine <span class="hlt">sources</span> to the far-field. The effects of nonuniform flow around the <span class="hlt">aircraft</span> and scattering of sound by fuselage and wings are accounted for in the formulation. The approach is based on the discretization of the inviscid flow equations through a collocation form of the Discontinuous Galerkin spectral element method. An isoparametric representation of the underlying geometry is used in order to take full advantage of the spectral accuracy of the method. Large-scale computations are made possible by a parallel implementation based on message passing. Results obtained for radiation from an axisymmetric nacelle alone are compared with those obtained when the same nacelle is installed in a generic configuration, with and without a wing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040086540','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040086540"><span><span class="hlt">Aircraft</span> Engine <span class="hlt">Noise</span> Scattering by Fuselage and Wings: A Computational Approach</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stanescu, D.; Hussaini, M. Y.; Farassat, F.</p> <p>2003-01-01</p> <p>The paper presents a time-domain method for computation of sound radiation from <span class="hlt">aircraft</span> engine <span class="hlt">sources</span> to the far-field. The effects of nonuniform flow around the <span class="hlt">aircraft</span> and scattering of sound by fuselage and wings are accounted for in the formulation. The approach is based on the discretization of the inviscid flow equations through a collocation form of the Discontinuous Galerkin spectral element method. An isoparametric representation of the underlying geometry is used in order to take full advantage of the spectral accuracy of the method. Large-scale computations are made possible by a parallel implementation based on message passing. Results obtained for radiation from an axisymmetric nacelle alone are compared with those obtained when the same nacelle is installed in a generic configuration, with and without a wing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030063224&hterms=discontinuous+galerkin+time+domain&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Ddiscontinuous%2Bgalerkin%2Btime%2Bdomain','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030063224&hterms=discontinuous+galerkin+time+domain&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Ddiscontinuous%2Bgalerkin%2Btime%2Bdomain"><span><span class="hlt">Aircraft</span> Engine <span class="hlt">Noise</span> Scattering by Fuselage and Wings: A Computational Approach</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Farassat, F.; Stanescu, D.; Hussaini, M. Y.</p> <p>2003-01-01</p> <p>The paper presents a time-domain method for computation of sound radiation from <span class="hlt">aircraft</span> engine <span class="hlt">sources</span> to the far field. The effects of non-uniform flow around the <span class="hlt">aircraft</span> and scattering of sound by fuselage and wings are accounted for in the formulation. The approach is based on the discretization of the inviscid flow equations through a collocation form of the discontinuous Galerkin spectral element method. An isoparametric representation of the underlying geometry is used in order to take full advantage of the spectral accuracy of the method. Large-scale computations are made possible by a parallel implementation based on message passing. Results obtained for radiation from an axisymmetric nacelle alone are compared with those obtained when the same nacelle is installed in a generic configuration, with and without a wing. 0 2002 Elsevier Science Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010012156&hterms=research+methods+education&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dresearch%2Bmethods%2Beducation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010012156&hterms=research+methods+education&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dresearch%2Bmethods%2Beducation"><span>Advanced Methods for <span class="hlt">Aircraft</span> Engine Thrust and <span class="hlt">Noise</span> Benefits: Nozzle-Inlet Flow Analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gilinsky, Mikhail; Morgan, Morris H.; Hardin, Jay C.; Mosiane, Lotlamoreng; Kaushal, Patel; Blankson, Isaiah M.</p> <p>2000-01-01</p> <p>In this project, we continue to develop the previous joint research between the Fluid Mechanics and Acoustics Laboratory (FM&AL) at Hampton University (HU) and the Jet <span class="hlt">Noise</span> Team (JNT) at the NASA Langley Research Center (NASA LaRC). The FM&AL was established at Hampton University in June of 1996 and has conducted research under two NASA grants: NAG-1-1835 (1996-99), and NAG-1-1936 (1997-00). In addition, the FM&AL has jointly conducted research with the Central AeroHydrodynamics Institute (TsAGI, Moscow) in Russia under a Civilian Research and Development Foundation (CRDF) grant #RE2-136 (1996-99). The goals of the FM&AL programs are twofold: (1) to improve the working efficiency of the FM&AUs team in generating new innovative ideas and in conducting research in the field of fluid dynamics and acoustics, basically for improvement of supersonic and subsonic <span class="hlt">aircraft</span> engines, and (2) to attract promising minority students to this research and training and, in cooperation with other HU departments, to teach them basic knowledge in Aerodynamics, Gas Dynamics, and Theoretical and Experimental Methods in Aeroacoustics and Computational Fluid Dynamics (CFD). The research at the HU FM&AL supports reduction schemes associated with the emission of engine pollutants for commercial <span class="hlt">aircraft</span> and concepts for reduction of observables for military <span class="hlt">aircraft</span>. These research endeavors relate to the goals of the NASA Strategic Enterprise in Aeronautics concerning the development of environmentally acceptable <span class="hlt">aircraft</span>. It is in this precise area, where the US <span class="hlt">aircraft</span> industry, academia, and Government are in great need of trained professionals and which is a high priority goal of the Minority University Research and Education (MUREP) Program, that the HU FM&AL can make its most important contribution. The main achievements for the reporting period in the development of concepts for <span class="hlt">noise</span> reduction and improvement in efficiency for jet exhaust nozzles and inlets for <span class="hlt">aircraft</span> engines</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020087614','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020087614"><span>Hybrid Active-Passive Systems for Control of <span class="hlt">Aircraft</span> Interior <span class="hlt">Noise</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fuller, Chris R.; Palumbo, Dan (Technical Monitor)</p> <p>2002-01-01</p> <p>It was proposed to continue with development and application in the two active-passive areas of Active Tuned Vibration Absorbers (ATVA) and smart foam applied to the reduction of interior <span class="hlt">noise</span> in <span class="hlt">aircraft</span>. In general the work was focused on making both techniques more efficient, practical and robust thus increasing their application potential. The work was also concerned with demonstrating the potential of these two technologies under realistic implementations as well as understanding the fundamental physics of the systems. The proposed work consisted of a three-year program and was tightly coordinated with related work being carried out in the Structural Acoustics Branch at NASA LaRC. The work was supervised and coordinated through all phases by Prof Chris Fuller of Va Tech.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910043642&hterms=Propellers+aircraft&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DPropellers%2Baircraft','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910043642&hterms=Propellers+aircraft&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DPropellers%2Baircraft"><span>Cruise <span class="hlt">noise</span> of an advanced single-rotation propeller measured from an adjacent <span class="hlt">aircraft</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Woodward, Richard P.; Loeffler, Irvin J.; Ranaudo, Richard J.</p> <p>1989-01-01</p> <p>Results are reported from flight measurements of the <span class="hlt">noise</span> from a full-scale SR-7L advanced single-rotation turbofan model mounted on the wing of the NASA Lewis Propfan Test Assessment (PTA) <span class="hlt">aircraft</span> (a modified Gulfstream II). Data obtained on the PTA with an outboard microphone boom and by the NASA Lewis acoustically instrumented Learjet flying along several sidelines relative to the PTA are presented in tables and graphs and briefly discussed. It is found that the PTA-boom and Learjet sound levels are in good agreement at Mach 0.69 and altitude 20,000 ft, but the Learjet values are significantly lower than the boom levels at Mach 0.79 and altitude 36,000 ft.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.V33A2608M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.V33A2608M"><span>Volcanic jet <span class="hlt">noise</span>: infrasonic <span class="hlt">source</span> processes and atmospheric propagation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matoza, R. S.; Fee, D.; Ogden, D. E.</p> <p>2011-12-01</p> <p>Volcanic eruption columns are complex flows consisting of (possibly supersonic) injections of ash-gas mixtures into the atmosphere. A volcanic eruption column can be modeled as a lower momentum-driven jet (the gas-thrust region), which transitions with altitude into a thermally buoyant plume. Matoza et al. [2009] proposed that broadband infrasonic signals recorded during this type of volcanic activity represent a low-frequency form of jet <span class="hlt">noise</span>. Jet <span class="hlt">noise</span> is produced at higher acoustic frequencies by smaller-scale man-made jet flows (e.g., turbulent jet flow from jet engines and rockets). Jet <span class="hlt">noise</span> generation processes could operate at larger spatial scales and produce infrasonic frequencies in the lower gas-thrust portion of the eruption column. Jet-<span class="hlt">noise</span>-like infrasonic signals have been observed at ranges of tens to thousands of kilometers from sustained volcanic explosions at Mount St. Helens, WA; Tungurahua, Ecuador; Redoubt, AK; and Sarychev Peak, Kuril Islands. Over such distances, the atmosphere cannot be considered homogeneous. Long-range infrasound propagation takes place primarily in waveguides formed by vertical gradients in temperature and horizontal winds, and exhibits strong spatiotemporal variability. The timing and location of volcanic explosions can be estimated from remote infrasonic data and could be used with ash cloud dispersion forecasts for hazard mitigation. <span class="hlt">Source</span> studies of infrasonic volcanic jet <span class="hlt">noise</span>, coupled with infrasound propagation modeling, hold promise for being able to constrain more detailed eruption jet parameters with remote, ground-based geophysical data. Here we present recent work on the generation and propagation of volcanic jet <span class="hlt">noise</span>. Matoza, R. S., D. Fee, M. A. Garcés, J. M. Seiner, P. A. Ramón, and M. A. H. Hedlin (2009), Infrasonic jet <span class="hlt">noise</span> from volcanic eruptions, Geophys. Res. Lett., 36, L08303, doi:10.1029/2008GL036486.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030025715','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030025715"><span>Sound Generation in the Presence of Moving Surfaces with Application to Internally Generated <span class="hlt">Aircraft</span> Engine <span class="hlt">Noise</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldstein, Marvin E.; Envia, E.</p> <p>2002-01-01</p> <p>In many cases of technological interest solid boundaries play a direct role in the aerodynamic sound generation process and their presence often results in a large increase in the acoustic radiation. A generalized treatment of the emission of sound from moving boundaries is presented. The approach is similar to that of Ffowcs Williams and Hawkings (1969) but the effect of the surrounding mean flow is explicitly accounted for. The results are used to develop a rational framework for the prediction of internally generated aero-engine <span class="hlt">noise</span>. The final formulas suggest some new <span class="hlt">noise</span> <span class="hlt">sources</span> that may be of practical significance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140002894','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140002894"><span>Development of a SMA-Based Slat-Cove Filler for Reduction of Aeroacoustic <span class="hlt">Noise</span> Associated With Transport-Class <span class="hlt">Aircraft</span> Wings</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Turner, Travis L.; Kidd, Reggie T.; Hartl, Darren J.; Scholten, William D.</p> <p>2013-01-01</p> <p>Airframe <span class="hlt">noise</span> is a significant part of the overall <span class="hlt">noise</span> produced by typical, transport-class <span class="hlt">aircraft</span> during the approach and landing phases of flight. Leading-edge slat <span class="hlt">noise</span> is a prominent <span class="hlt">source</span> of airframe <span class="hlt">noise</span>. The concept of a slat-cove filler was proposed in previous work as an effective means of mitigating slat <span class="hlt">noise</span>. Bench-top models were deployed at 75% scale to study the feasibility of producing a functioning slat-cove filler. Initial results from several concepts led to a more-focused effort investigating a deformable structure based upon pseudoelastic SMA materials. The structure stows in the cavity between the slat and main wing during cruise and deploys simultaneously with the slat to guide the aerodynamic flow suitably for low <span class="hlt">noise</span>. A qualitative parametric study of SMA-enabled, slat-cove filler designs was performed on the bench-top. Computational models were developed and analyses were performed to assess the displacement response under representative aerodynamic load. The bench-top and computational results provide significant insight into design trades and an optimal design.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4064632','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4064632"><span>Exposure–Response Relationship Between <span class="hlt">Aircraft</span> <span class="hlt">Noise</span> and Sleep Quality: A Community-based Cross-sectional Study</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kim, Soo Jeong; Chai, Sang Kug; Lee, Keou Won; Park, Jae-Beom; Min, Kyoung-Bok; Kil, Hyun Gwon; Lee, Chan; Lee, Kyung Jong</p> <p>2014-01-01</p> <p>Objectives Exposure to <span class="hlt">aircraft</span> <span class="hlt">noise</span> has been shown to have adverse health effects, causing annoyance and affecting the health-related quality of life, sleep, and mental states of those exposed to it. This study aimed to determine sleep quality in participants residing near an airfield and to evaluate the relationship between the levels of <span class="hlt">aircraft</span> <span class="hlt">noise</span> and sleep quality. Methods Neighboring regions of a military airfield were divided into three groups: a high exposure group, a low exposure group, and a control group. A total of 1082 participants (aged 30–79 years) completed a comprehensive self-administered questionnaire requesting information about demographics, medical history, lifestyle, and the Pittsburgh Sleep Quality Index. Results Of the 1082 participants, 1005 qualified for this study. The prevalence of sleep disturbance was 45.5% in the control group, 71.8% in the low exposure group, and 77.1% in the high exposure group (p for trend < 0.001). After adjusting for potential confounding factors, we determined the exposure–response relationship between the degree of <span class="hlt">aircraft</span> <span class="hlt">noise</span> and sleep quality. Of the participants with a normal mental status, the prevalence of sleep disturbance was 2.61-fold higher in the low exposure group and 3.52-fold higher in the high exposure group than in the control group. Conclusion The relationship between <span class="hlt">aircraft</span> <span class="hlt">noise</span> and health should be further evaluated through a large-scale follow-up study. PMID:24955321</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23117540','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23117540"><span>The impact of <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure on South African children's reading comprehension: the moderating effect of home language.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Seabi, Joseph; Cockcroft, Kate; Goldschagg, Paul; Greyling, Mike</p> <p>2012-01-01</p> <p>Given the limited studies conducted within the African continent, the purpose of this study was to investigate the impact of chronic <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure and the moderating effect of home language on the learners' reading comprehension. The sample comprised 437 (52%) senior primary learners exposed to high levels of <span class="hlt">aircraft</span> <span class="hlt">noise</span> (Experimental group) and 337 (48%) learners residing in a quieter area (Control group). Of these, 151 learners in the Experimental group spoke English as a first language (EFL) and 162 spoke English as a second language (ESL). In the Control group, the numbers were similarly divided (EFL n = 191; ESL n = 156). A univariate General Linear Model was used to investigate the effects of <span class="hlt">aircraft</span> <span class="hlt">noise</span> exposure and language on reading comprehension, while observing for the possible impact of intellectual ability, gender, and socioeconomic status on the results. A significant difference was observed between ESL and EFL learners in favor of the latter (F 1,419 = 21.95, P =.000). In addition a substantial and significant interaction effect was found between the experimental and control groups for the two language groups. For the EFL speakers there was a strong reduction in reading comprehension in the <span class="hlt">aircraft</span> <span class="hlt">noise</span> group. By contrast this difference was not significant for the ESL speakers. Implications of the findings and suggestions for further research are made in the article.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JSV...376...18H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JSV...376...18H"><span>Active control of counter-rotating open rotor interior <span class="hlt">noise</span> in a Dornier 728 experimental <span class="hlt">aircraft</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haase, Thomas; Unruh, Oliver; Algermissen, Stephan; Pohl, Martin</p> <p>2016-08-01</p> <p>The fuel consumption of future civil <span class="hlt">aircraft</span> needs to be reduced because of the CO2 restrictions declared by the European Union. A consequent lightweight design and a new engine concept called counter-rotating open rotor are seen as key technologies in the attempt to reach this ambitious goals. Bearing in mind that counter-rotating open rotor engines emit very high sound pressures at low frequencies and that lightweight structures have a poor transmission loss in the lower frequency range, these key technologies raise new questions in regard to acoustic passenger comfort. One of the promising solutions for the reduction of sound pressure levels inside the <span class="hlt">aircraft</span> cabin are active sound and vibration systems. So far, active concepts have rarely been investigated for a counter-rotating open rotor pressure excitation on complex airframe structures. Hence, the state of the art is augmented by the preliminary study presented in this paper. The study shows how an active vibration control system can influence the sound transmission of counter-rotating open rotor <span class="hlt">noise</span> through a complex airframe structure into the cabin. Furthermore, open questions on the way towards the realisation of an active control system are addressed. In this phase, an active feedforward control system is investigated in a fully equipped Dornier 728 experimental prototype <span class="hlt">aircraft</span>. In particular, the sound transmission through the airframe, the coupling of classical actuators (inertial and piezoelectric patch actuators) into the structure and the performance of the active vibration control system with different error sensors are investigated. It can be shown that the active control system achieves a reduction up to 5 dB at several counter-rotating open rotor frequencies but also that a better performance could be achieved through further optimisations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21303001','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21303001"><span><span class="hlt">Aircraft</span> <span class="hlt">noise</span>: accounting for changes in air traffic with time of day.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schäffer, Beat; Bütikofer, Rudolf; Plüss, Stefan; Thomann, Georg</p> <p>2011-01-01</p> <p><span class="hlt">Aircraft</span> <span class="hlt">noise</span> contours are estimated using model calculations and, due to their impact on land use planning, they need to be highly accurate. During night time, not only the number and dominant types of <span class="hlt">aircraft</span> may differ from daytime but also the flight paths flown may differ. To determine to which detail these variations in flight paths need to be considered, calculations were performed exemplarily for two airports using all available radar data over 1 year, taking into account their changes over the day. The results of this approach were compared with results of a simpler approach which does not consider such changes. While both calculations yielded similar results for the day and close to the airport, differences increased with distance as well as with the period of day (day<first hour of the night<second hour of the night, respectively, day<evening<night). Only the detailed calculation always accounted for the flight path changes in full detail. Possible legal consequences of such different modeling approaches are estimated, and the model results are compared to monitoring measurements. Finally, the situations for which the simpler approach is sufficiently accurate are ascertained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920004540','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920004540"><span>Development of an annoyance model based upon elementary auditory sensations for steady-state <span class="hlt">aircraft</span> interior <span class="hlt">noise</span> containing tonal components</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Angerer, James R.; Mccurdy, David A.; Erickson, Richard A.</p> <p>1991-01-01</p> <p>The purpose of this investigation was to develop a <span class="hlt">noise</span> annoyance model, superior to those already in use, for evaluating passenger response to sounds containing tonal components which may be heard within current and future commercial <span class="hlt">aircraft</span>. The sound spectra investigated ranged from those being experienced by passengers on board turbofan powered <span class="hlt">aircraft</span> now in service to those cabin <span class="hlt">noise</span> spectra passengers may experience within advanced propeller-driven <span class="hlt">aircraft</span> of the future. A total of 240 sounds were tested in this experiment. Sixty-six of these 240 sounds were steady state, while the other 174 varied temporally due to tonal beating. Here, the entire experiment is described, but the analysis is limited to those responses elicited by the 66 steady-state sounds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23363199','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23363199"><span>Near-field shock formation in <span class="hlt">noise</span> propagation from a high-power jet <span class="hlt">aircraft</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gee, Kent L; Neilsen, Tracianne B; Downing, J Micah; James, Michael M; McKinley, Richard L; McKinley, Robert C; Wall, Alan T</p> <p>2013-02-01</p> <p><span class="hlt">Noise</span> measurements near the F-35A Joint Strike Fighter at military power are analyzed via spatial maps of overall and band pressure levels and skewness. Relative constancy of the pressure waveform skewness reveals that waveform asymmetry, characteristic of supersonic jets, is a <span class="hlt">source</span> phenomenon originating farther upstream than the maximum overall level. Conversely, growth of the skewness of the time derivative with distance indicates that acoustic shocks largely form through the course of near-field propagation and are not generated explicitly by a <span class="hlt">source</span> mechanism. These results potentially counter previous arguments that jet "crackle" is a <span class="hlt">source</span> phenomenon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040046150','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040046150"><span>Advanced Methods for <span class="hlt">Aircraft</span> Engine Thrust and <span class="hlt">Noise</span> Benefits: Nozzle-Inlet Flow Analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Morgan, Morris H., III; Gilinsky, Mikhail M.</p> <p>2004-01-01</p> <p>In this project on the first stage (2000-Ol), we continued to develop the previous joint research between the Fluid Mechanics and Acoustics Laboratory (FM&AL) at Hampton University (HU) and the Jet <span class="hlt">Noise</span> Team (JNT) at the NASA Langley Research Center (NASA LaRC). At the second stage (2001-03), FM&AL team concentrated its efforts on solving of problems of interest to Glenn Research Center (NASA GRC), especially in the field of propulsion system enhancement. The NASA GRC R&D Directorate and LaRC Hyper-X Program specialists in a hypersonic technology jointly with the FM&AL staff conducted research on a wide region of problems in the propulsion field as well as in experimental testing and theoretical and numerical simulation analyses for advanced <span class="hlt">aircraft</span> and rocket engines. The last year the Hampton University School of Engineering & Technology was awarded the NASA grant, for creation of the Aeropropulsion Center, and the FM&AL is a key team of the project fulfillment responsible for research in Aeropropulsion and Acoustics (Pillar I). This work is supported by joint research between the NASA GRC/ FM&AL and the Institute of Mechanics at Moscow State University (IMMSU) in Russia under a CRDF grant. The main areas of current scientific interest of the FM&AL include an investigation of the proposed and patented advanced methods for <span class="hlt">aircraft</span> engine thrust and <span class="hlt">noise</span> benefits. This is the main subject of our other projects, of which one is presented. The last year we concentrated our efforts to analyze three main problems: (a) new effective methods fuel injection into the flow stream in air-breathing engines; (b) new re-circulation method for mixing, heat transfer and combustion enhancement in propulsion systems and domestic industry application; (c) covexity flow The research is focused on a wide regime of problems in the propulsion field as well as in experimental testing and theoretical and numerical simulation analyses for advanced <span class="hlt">aircraft</span> and rocket engines (see, for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760009700','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760009700"><span>Special analysis of community annoyance with <span class="hlt">aircraft</span> <span class="hlt">noise</span> reported by residents in the vicinity of JFK Airport, 1972</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Borsky, P. N.</p> <p>1975-01-01</p> <p>During the summer of 1972, about 1500 residents were interviewed twice in 11 communities near JFK airport. Detailed <span class="hlt">aircraft</span> operations reports were also collected for this period, and an effort has been made to analyze recorded human response data in relation to a number of physical exposure parameters. A series of exposure indexes, based on an arithmetic integration of <span class="hlt">aircraft</span> operations, were correlated with summated <span class="hlt">aircraft</span> <span class="hlt">noise</span> annoyance responses. None of these correlations were as good as the CNR index which assumes a logrithmetic integration of numbers of <span class="hlt">aircraft</span> exposures and includes a day-night differential weighting of 10:1. There were substantial variations in average annoyance responses among communities with similar CNR exposures, substantiating previous findings that attitudinal and other personal variables also play an important role in determining annoyance differences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860014922','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860014922"><span>Consideration of some factors affecting low-frequency fuselage <span class="hlt">noise</span> transmission for propeller <span class="hlt">aircraft</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mixson, J. S.; Roussos, L. A.</p> <p>1986-01-01</p> <p>Possible reasons for disagreement between measured and predicted trends of sidewall <span class="hlt">noise</span> transmission at low frequency are investigated using simplified analysis methods. An analytical model combining incident plane acoustic waves with an infinite flat panel is used to study the effects of sound incidence angle, plate structural properties, frequency, absorption, and the difference between <span class="hlt">noise</span> reduction and transmission loss. Analysis shows that these factors have significant effects on <span class="hlt">noise</span> transmission but they do not account for the differences between measured and predicted trends at low frequencies. An analytical model combining an infinite flat plate with a normally incident acoustic wave having exponentially decaying magnitude along one coordinate is used to study the effect of a localized <span class="hlt">source</span> distribution such as is associated with propeller <span class="hlt">noise</span>. Results show that the localization brings the predicted low-frequency trend of <span class="hlt">noise</span> transmission into better agreement with measured propeller results. This effect is independent of low-frequency stiffness effects that have been previously reported to be associated with boundary conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1980aiaa.confS....R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1980aiaa.confS....R"><span>An analytical model for study of interior <span class="hlt">noise</span> control for high-speed, propeller-driven <span class="hlt">aircraft</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Revell, J. D.; Balena, F. J.; Koval, L. R.</p> <p>1980-06-01</p> <p>An analytical method is described for prediction of the interior <span class="hlt">noise</span> levels for propeller-driven <span class="hlt">aircraft</span>, given the exterior <span class="hlt">noise</span> signature and its harmonic spectrum, and a description of the fuselage sidewall structure and various candidate 'add-on' <span class="hlt">noise</span>-control elements. The structural response is described by the theory of Koval but simplified to consider the stiffeners as 'smeared' elements. The incremental transmission loss (TL) due to add-on-<span class="hlt">noise</span>-control elements is derived from the Beranek and Work method. Comparisons between experimental data and the theory are presented. The method is reasonably accurate below the ring frequency, but is somewhat conservative at normal incidence angle. This method is, however, expedient computationally, is economical and permits rapid comparisons of <span class="hlt">noise</span>-control penalties for various treatment concepts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8460382','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8460382"><span>A comparison between the impact of <span class="hlt">noise</span> from <span class="hlt">aircraft</span>, road traffic and trains on long-term recall and recognition of a text in children aged 12-14 years.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hygge, S</p> <p>1993-01-01</p> <p>A total of 417 students in the seventh grade, 12-14 old, took part in three 15 min learning sessions in their ordinary class-rooms. Their task was to read a text, and they were tested one week later with difficult recall questions and less difficult recognition items on the text. The first session was a pretest for their learning abilities. This session was run in ambient <span class="hlt">noise</span> conditions and all the students read the very same text. The scores from this session were employed to split the pupils along the median into two groups of learning ability. Sessions two and three were counterbalanced as a <span class="hlt">noise</span> condition or an ambient <span class="hlt">noise</span> condition. In these sessions two other texts were employed, and they appeared equally often under the <span class="hlt">noise</span> and ambient conditions, as well as under the two different presentation orders. Three subgroups of the pupils were exposed to <span class="hlt">aircraft</span> <span class="hlt">noise</span>, train <span class="hlt">noise</span> and road-traffic <span class="hlt">noise</span>. The <span class="hlt">noise</span> types were of the same equivalent level (66 dB(A) Leq) in all subgroups. The design of the study permitted two different analyses of long-term learning. First, in a within subject analysis, the difference scores between the <span class="hlt">noise</span> and ambient <span class="hlt">noise</span> conditions in session 2 and 3 were calculated, and crossed with learning ability (high and low) and type of <span class="hlt">noise</span>. In a second between subject analysis, the difference scores in session 1 and 2 were crossed with the group factor whether they had <span class="hlt">noise</span> or ambient conditions in session 2, and the ability and <span class="hlt">noise</span> type factors. Both analyses yielded the same results. <span class="hlt">Noise</span> impaired long-term recall of the difficult items. Degree of impairment on the recall items did not interact with <span class="hlt">noise</span> <span class="hlt">source</span> or learning ability. The average impairment due to <span class="hlt">aircraft</span> and road traffic <span class="hlt">noise</span> was around 23% of the scores. Train <span class="hlt">noise</span> had no effect. For the easy recognition items there were no effects of <span class="hlt">noise</span> exposure, nor of its interaction with <span class="hlt">noise</span> <span class="hlt">source</span> and learning ability. Since the number of pages read did not</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27106340','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27106340"><span>Military jet <span class="hlt">noise</span> <span class="hlt">source</span> imaging using multisource statistically optimized near-field acoustical holography.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wall, Alan T; Gee, Kent L; Neilsen, Tracianne B; McKinley, Richard L; James, Michael M</p> <p>2016-04-01</p> <p>The identification of acoustic <span class="hlt">sources</span> is critical to targeted <span class="hlt">noise</span> reduction efforts for jets on high-performance tactical <span class="hlt">aircraft</span>. This paper describes the imaging of acoustic <span class="hlt">sources</span> from a tactical jet using near-field acoustical holography techniques. The measurement consists of a series of scans over the hologram with a dense microphone array. Partial field decomposition methods are performed to generate coherent holograms. Numerical extrapolation of data beyond the measurement aperture mitigates artifacts near the aperture edges. A multisource equivalent wave model is used that includes the effects of the ground reflection on the measurement. Multisource statistically optimized near-field acoustical holography (M-SONAH) is used to reconstruct apparent <span class="hlt">source</span> distributions between 20 and 1250 Hz at four engine powers. It is shown that M-SONAH produces accurate field reconstructions for both inward and outward propagation in the region spanned by the physical hologram measurement. Reconstructions across the set of engine powers and frequencies suggests that directivity depends mainly on estimated <span class="hlt">source</span> location; <span class="hlt">sources</span> farther downstream radiate at a higher angle relative to the inlet axis. At some frequencies and engine powers, reconstructed fields exhibit multiple radiation lobes originating from overlapped <span class="hlt">source</span> regions, which is a phenomenon relatively recently reported for full-scale jets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800016607','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800016607"><span>Analysis of Vibratory Excitation of Gear Systems as a Contributor to <span class="hlt">Aircraft</span> Interior <span class="hlt">Noise</span>. [helicopter cabin <span class="hlt">noise</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mark, W. D.</p> <p>1979-01-01</p> <p>Application of the transfer function approach to predict the resulting interior <span class="hlt">noise</span> contribution requires gearbox vibration <span class="hlt">sources</span> and paths to be characterized in the frequency domain. Tooth-face deviations from perfect involute surfaces were represented in terms of Legendre polynomials which may be directly interpreted in terms of tooth-spacing errors, mean and random deviations associated with involute slope and fullness, lead mismatch and crowning, and analogous higher-order components. The contributions of these components to the spectrum of the static transmission error is discussed and illustrated using a set of measurements made on a pair of helicopter spur gears. The general methodology presented is applicable to both spur and helical gears.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6698744','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6698744"><span>Environmental issues: <span class="hlt">noise</span>, rail <span class="hlt">noise</span>, and high-speed rail</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hall, F.L.; Welland, J.D.; Bragdon, C.R.; Houtman, J.W.; Immers, B.H.</p> <p>1987-01-01</p> <p>The six papers in the report deal with the following areas: the effect of <span class="hlt">noise</span> barriers on the market value of adjacent residential properties; control of airport- and <span class="hlt">aircraft</span>-related <span class="hlt">noise</span> in the United States; a traffic-assignment model to reduce <span class="hlt">noise</span> annoyance in urban networks; a survey of railroad occupational <span class="hlt">noise</span> <span class="hlt">sources</span>; a prediction procedure for rail transportation ground-borne <span class="hlt">noise</span> and vibration; and high-speed rail in California: the dream, the process, and the reality.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850028724&hterms=Propellers+aircraft&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DPropellers%2Baircraft','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850028724&hterms=Propellers+aircraft&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DPropellers%2Baircraft"><span>Effects of acoustic treatment on the interior <span class="hlt">noise</span> levels of a twin-engine propeller <span class="hlt">aircraft</span> - Experimental flight results and theoretical predictions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Beyer, T. B.; Powell, C. A.; Daniels, E. F.; Pope, L. D.</p> <p>1984-01-01</p> <p>In-flight <span class="hlt">noise</span> level measurements were made within two cabin configurations of a general aviation business <span class="hlt">aircraft</span>. The Fairchild Merlin IVC twin-engine <span class="hlt">aircraft</span> was tested with bare walls and fiberglass insulation and in an executive trim configuration. Narrow-band and octave format data were subjected to analyses which permitted identification of the blade passage harmonics (BPH). Cabin <span class="hlt">noise</span> level reductions (insertion losses) due to added insulation varied with position in the cabin, the BPH number, cabin pressure, and engine torque. The measurements were closely predicted using the propeller <span class="hlt">aircraft</span> interior <span class="hlt">noise</span> (PAIN) mode.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020059662','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020059662"><span>General Aviation Interior <span class="hlt">Noise</span>. Part 3; <span class="hlt">Noise</span> Control Measure Evaluation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Unruh, James F.; Till, Paul D.; Palumbo, Daniel L. (Technical Monitor)</p> <p>2002-01-01</p> <p>The work reported herein is an extension to the work accomplished under NASA Grant NAG1-2091 on the development of <span class="hlt">noise/source</span>/path identification techniques for single engine propeller driven General Aviation <span class="hlt">aircraft</span>. The previous work developed a Conditioned Response Analysis (CRA) technique to identify potential <span class="hlt">noise</span> <span class="hlt">sources</span> that contributed to the dominating tonal responses within the <span class="hlt">aircraft</span> cabin. The objective of the present effort was to improve and verify the findings of the CRA and develop and demonstrate <span class="hlt">noise</span> control measures for single engine propeller driven General Aviation <span class="hlt">aircraft</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA468464','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA468464"><span>The Mitigation of Radio <span class="hlt">Noise</span> from External <span class="hlt">Sources</span> at Receiving Sites</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2007-05-01</p> <p>receiving site. Step 2—Understand <span class="hlt">sources</span> and <span class="hlt">source</span> mechanisms . Step 3—Locate <span class="hlt">sources</span>. Step 4—Identify the hardware which is generating <span class="hlt">noise</span>...Typical <span class="hlt">noise</span> problems at a receiving site are described in Section 1. Typical <span class="hlt">sources</span>, <span class="hlt">source</span> mechanisms and the temporal and spectral properties...Two common types of <span class="hlt">noise</span> will be encountered along with several less common types. These types are closely related to the <span class="hlt">source</span> mechanisms</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780061593&hterms=properties+sound&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dproperties%2Bsound','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780061593&hterms=properties+sound&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dproperties%2Bsound"><span>Effects of cavity resonances on sound transmission into a thin cylindrical shell. [<span class="hlt">noise</span> reduction in <span class="hlt">aircraft</span> fuselage</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Koval, L. R.</p> <p>1978-01-01</p> <p>In the context of the transmission of airborne <span class="hlt">noise</span> into an <span class="hlt">aircraft</span> fuselage, a mathematical model is presented for the effects of internal cavity resonances on sound transmission into a thin cylindrical shell. The '<span class="hlt">noise</span> reduction' of the cylinder is defined and computed, with and without including the effects of internal cavity resonances. As would be expected, the <span class="hlt">noise</span> reduction in the absence of cavity resonances follows the same qualitative pattern as does transmission loss. Numerical results show that cavity resonances lead to wide fluctuations and a general decrease of <span class="hlt">noise</span> reduction, especially at cavity resonances. Modest internal absorption is shown to greatly reduce the effect of cavity resonances. The effects of external airflow, internal cabin pressurization, and different acoustical properties inside and outside the cylinder are also included and briefly examined.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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