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Sample records for noise psyko-akustisk vaerdering

  1. Rotorcraft noise

    NASA Technical Reports Server (NTRS)

    Huston, R. J. (Compiler)

    1982-01-01

    The establishment of a realistic plan for NASA and the U.S. helicopter industry to develop a design-for-noise methodology, including plans for the identification and development of promising noise reduction technology was discussed. Topics included: noise reduction techniques, scaling laws, empirical noise prediction, psychoacoustics, and methods of developing and validing noise prediction methods.

  2. Airport noise

    NASA Technical Reports Server (NTRS)

    Pendley, R. E.

    1982-01-01

    The problem of airport noise at several airports and air bases is detailed. Community reactions to the noise, steps taken to reduce jet engine noise, and the effect of airport use restrictions and curfews on air transportation are discussed. The adverse effect of changes in allowable operational noise on airport safety and altenative means for reducing noise pollution are considered. Community-airport relations and public relations are discussed.

  3. Combustion noise

    NASA Technical Reports Server (NTRS)

    Strahle, W. C.

    1977-01-01

    A review of the subject of combustion generated noise is presented. Combustion noise is an important noise source in industrial furnaces and process heaters, turbopropulsion and gas turbine systems, flaring operations, Diesel engines, and rocket engines. The state-of-the-art in combustion noise importance, understanding, prediction and scaling is presented for these systems. The fundamentals and available theories of combustion noise are given. Controversies in the field are discussed and recommendations for future research are made.

  4. Community noise

    NASA Technical Reports Server (NTRS)

    Bragdon, C. R.

    1982-01-01

    Airport and community land use planning as they relate to airport noise reduction are discussed. Legislation, community relations, and the physiological effect of airport noise are considered. Noise at the Logan, Los Angeles, and Minneapolis/St. Paul airports is discussed.

  5. Interior Noise

    NASA Technical Reports Server (NTRS)

    Mixson, John S.; Wilby, John F.

    1991-01-01

    The generation and control of flight vehicle interior noise is discussed. Emphasis is placed on the mechanisms of transmission through airborne and structure-borne paths and the control of cabin noise by path modification. Techniques for identifying the relative contributions of the various source-path combinations are also discussed along with methods for the prediction of aircraft interior noise such as those based on the general modal theory and statistical energy analysis.

  6. Noise Protection

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Environmental Health Systems puts forth an increasing effort in the U.S. to develop ways of controlling noise, particularly in industrial environments due to Federal and State laws, labor union insistence and new findings relative to noise pollution impact on human health. NASA's Apollo guidance control system aided in the development of a noise protection product, SMART. The basis of all SMART products is SMART compound a liquid plastic mixture with exceptional energy/sound absorbing qualities. The basic compound was later refined for noise protection use.

  7. Noise pollution resources compendium

    NASA Technical Reports Server (NTRS)

    1972-01-01

    A compendium is presented of documents on noise. The articles presented are categorized in the following sections: noise sources, noise detection and measurement, noise abatement and control, physical effects of noise, psychological and physiological effects of noise, noise regulations and standards, patents and contracts, and noise research.

  8. Improving Gabor noise.

    PubMed

    Lagae, Ares; Lefebvre, Sylvain; Dutré, Philip

    2011-08-01

    We have recently proposed a new procedural noise function, Gabor noise, which offers a combination of properties not found in the existing noise functions. In this paper, we present three significant improvements to Gabor noise: 1) an isotropic kernel for Gabor noise, which speeds up isotropic Gabor noise with a factor of roughly two, 2) an error analysis of Gabor noise, which relates the kernel truncation radius to the relative error of the noise, and 3) spatially varying Gabor noise, which enables spatial variation of all noise parameters. These improvements make Gabor noise an even more attractive alternative for the existing noise functions.

  9. 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.

  10. Control of Environmental Noise

    ERIC Educational Resources Information Center

    Jensen, Paul

    1973-01-01

    Discusses the physical properties, sources, physiological effects, and legislation pertaining to noise, especially noise characteristics in the community. Indicates that noise reduction steps can be taken more intelligently after determination of the true noise sources and paths. (CC)

  11. Noise pollution resources compendium

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Abstracts of reports concerning noise pollution are presented. The abstracts are grouped in the following areas of activity: (1) sources of noise, (2) noise detection and measurement, (3) noise abatement and control, (4) physical effects of noise and (5) social effects of noise.

  12. Noise Abatement

    NASA Technical Reports Server (NTRS)

    1983-01-01

    SMART, Sound Modification and Regulated Temperature compound, is a liquid plastic mixture with exceptional energy and sound absorbing qualities. It is derived from a very elastic plastic which was an effective noise abatement material in the Apollo Guidance System. Discovered by a NASA employee, it is marketed by Environmental Health Systems, Inc. (EHS). The product has been successfully employed by a diaper company with noisy dryers and a sugar company with noisy blowers. The company also manufactures an audiometric test booth and acoustical office partitions.

  13. 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.

  14. Turbomachinery noise

    NASA Astrophysics Data System (ADS)

    Groeneweg, John F.; Sofrin, Thomas G.; Rice, Edward J.; Gliebe, Phillip R.

    1991-08-01

    Summarized here are key advances in experimental techniques and theoretical applications which point the way to a broad understanding and control of turbomachinery noise. On the experimental side, the development of effective inflow control techniques makes it possible to conduct, in ground based facilities, definitive experiments in internally controlled blade row interactions. Results can now be valid indicators of flight behavior and can provide a firm base for comparison with analytical results. Inflow control coupled with detailed diagnostic tools such as blade pressure measurements can be used to uncover the more subtle mechanisms such as rotor strut interaction, which can set tone levels for some engine configurations. Initial mappings of rotor wake-vortex flow fields have provided a data base for a first generation semiempirical flow disturbance model. Laser velocimetry offers a nonintrusive method for validating and improving the model. Digital data systems and signal processing algorithms are bringing mode measurement closer to a working tool that can be frequently applied to a real machine such as a turbofan engine. On the analytical side, models of most of the links in the chain from turbomachine blade source to far field observation point have been formulated. Three dimensional lifting surface theory for blade rows, including source noncompactness and cascade effects, blade row transmission models incorporating mode and frequency scattering, and modal radiation calculations, including hybrid numerical-analytical approaches, are tools which await further application.

  15. Turbomachinery noise

    NASA Technical Reports Server (NTRS)

    Groeneweg, John F.; Sofrin, Thomas G.; Rice, Edward J.; Gliebe, Phillip R.

    1991-01-01

    Summarized here are key advances in experimental techniques and theoretical applications which point the way to a broad understanding and control of turbomachinery noise. On the experimental side, the development of effective inflow control techniques makes it possible to conduct, in ground based facilities, definitive experiments in internally controlled blade row interactions. Results can now be valid indicators of flight behavior and can provide a firm base for comparison with analytical results. Inflow control coupled with detailed diagnostic tools such as blade pressure measurements can be used to uncover the more subtle mechanisms such as rotor strut interaction, which can set tone levels for some engine configurations. Initial mappings of rotor wake-vortex flow fields have provided a data base for a first generation semiempirical flow disturbance model. Laser velocimetry offers a nonintrusive method for validating and improving the model. Digital data systems and signal processing algorithms are bringing mode measurement closer to a working tool that can be frequently applied to a real machine such as a turbofan engine. On the analytical side, models of most of the links in the chain from turbomachine blade source to far field observation point have been formulated. Three dimensional lifting surface theory for blade rows, including source noncompactness and cascade effects, blade row transmission models incorporating mode and frequency scattering, and modal radiation calculations, including hybrid numerical-analytical approaches, are tools which await further application.

  16. Noise and blast

    NASA Technical Reports Server (NTRS)

    Hodge, D. C.; Garinther, G. R.

    1973-01-01

    Noise and blast environments are described, providing a definition of units and techniques of noise measurement and giving representative booster-launch and spacecraft noise data. The effects of noise on hearing sensitivity and performance are reviewed, and community response to noise exposure is discussed. Physiological, or nonauditory, effects of noise exposure are also treated, as are design criteria and methods for minimizing the noise effects of hearing sensitivity and communications. The low level sound detection and speech reception are included, along with subjective and behavioral responses to noise.

  17. Noise and blast

    NASA Technical Reports Server (NTRS)

    Hodge, D. C.; Garinther, G. R.

    1973-01-01

    Noise and blast environments are described, providing a definition of units and techniques of noise measurement and giving representative booster-launch and spacecraft noise data. The effects of noise on hearing sensitivity and performance are reviewed, and community response to noise exposure is discussed. Physiological, or nonauditory, effects of noise exposure are also treated, as are design criteria and methods for minimizing the noise effects of hearing sensitivity and communications. The low level sound detection and speech reception are included, along with subjective and behavioral responses to noise.

  18. Noise, Health, and Architecture.

    ERIC Educational Resources Information Center

    Beranek, Leo L.

    There is reasonable agreement that hearing impairment is related to noise exposure. This hearing loss due to noise is considered a serious health injury, but there is still difficulty in delineating the importance of noise related to people's general non-auditory well-being and health. Beside hearing loss, noise inhibits satisfactory speech…

  19. Active Noise Control for Dishwasher noise

    NASA Astrophysics Data System (ADS)

    Lee, Nokhaeng; Park, Youngjin

    2016-09-01

    The dishwasher is a useful home appliance and continually used for automatically washing dishes. It's commonly placed in the kitchen with built-in style for practicality and better use of space. In this environment, people are easily exposed to dishwasher noise, so it is an important issue for the consumers, especially for the people living in open and narrow space. Recently, the sound power levels of the noise are about 40 - 50 dBA. It could be achieved by removal of noise sources and passive means of insulating acoustical path. For more reduction, such a quiet mode with the lower speed of cycle has been introduced, but this deteriorates the washing capacity. Under this background, we propose active noise control for dishwasher noise. It is observed that the noise is propagating mainly from the lower part of the front side. Control speakers are placed in the part for the collocation. Observation part of estimating sound field distribution and control part of generating the anti-noise are designed for active noise control. Simulation result shows proposed active noise control scheme could have a potential application for dishwasher noise reduction.

  20. Aviation noise effects

    NASA Astrophysics Data System (ADS)

    Newman, J. S.; Beattie, K. R.

    1985-03-01

    This report summarizes the effects of aviation noise in many areas, ranging from human annoyance to impact on real estate values. It also synthesizes the findings of literature on several topics. Included in the literature were many original studies carried out under FAA and other Federal funding over the past two decades. Efforts have been made to present the critical findings and conclusions of pertinent research, providing, when possible, a bottom line conclusion, criterion or perspective. Issues related to aviation noise are highlighted, and current policy is presented. Specific topic addressed include: annoyance; Hearing and hearing loss; noise metrics; human response to noise; speech interference; sleep interference; non-auditory health effects of noise; effects of noise on wild and domesticated animals; low frequency acoustical energy; impulsive noise; time of day weightings; noise contours; land use compatibility; and real estate values. This document is designed for a variety of users, from the individual completely unfamiliar with aviation noise to experts in the field.

  1. [Subjective sensitivity to noise].

    PubMed

    Belojević, G

    1991-01-01

    It is likely that individual variations in subjectively estimated noise sensitivity influence different social and psychophysiological reactions of people exposed to noise. Subjective noise sensitivity might be a relatively stable personal characteristic. A correlation have been found between high sensitiveness to noise and some medical symptoms (sleep disturbance, nervousness, depression), and worse work performance in noisy environments. An introvert person with neurotic symptoms is more frequently found in people highly sensitive to noise. Testing for subjective sensitivity to noise might be helpful in professional selection and orientation for noisy work-places as well as in housing advising.

  2. Propagation of Environmental Noise

    ERIC Educational Resources Information Center

    Lyon, R. H.

    1973-01-01

    Solutions for environmental noise pollution lie in systematic study of many basic processes such as reflection, scattering, and spreading. Noise propagation processes should be identified in different situations and assessed for their relative importance. (PS)

  3. Propagation of Environmental Noise

    ERIC Educational Resources Information Center

    Lyon, R. H.

    1973-01-01

    Solutions for environmental noise pollution lie in systematic study of many basic processes such as reflection, scattering, and spreading. Noise propagation processes should be identified in different situations and assessed for their relative importance. (PS)

  4. NASA Jet Noise Research

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda

    2016-01-01

    The presentation highlights NASA's jet noise research for 2016. Jet-noise modeling efforts, jet-surface interactions results, acoustic characteristics of multi-stream jets, and N+2 Supersonic Aircraft system studies are presented.

  5. Handbook of noise ratings

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    Handbook announced in Tech Brief is compendium of information describing multifarious noise methods now in use. Reference material gives user better access to definitions, application, and calculation procedures of current noise rating methods.

  6. Core-Noise

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.

    2010-01-01

    This presentation is a technical progress report and near-term outlook for NASA-internal and NASA-sponsored external work on core (combustor and turbine) noise funded by the Fundamental Aeronautics Program Subsonic Fixed Wing (SFW) Project. Sections of the presentation cover: the SFW system level noise metrics for the 2015, 2020, and 2025 timeframes; the emerging importance of core noise and its relevance to the SFW Reduced-Noise-Aircraft Technical Challenge; the current research activities in the core-noise area, with some additional details given about the development of a high-fidelity combustion-noise prediction capability; the need for a core-noise diagnostic capability to generate benchmark data for validation of both high-fidelity work and improved models, as well as testing of future noise-reduction technologies; relevant existing core-noise tests using real engines and auxiliary power units; and examples of possible scenarios for a future diagnostic facility. The NASA Fundamental Aeronautics Program has the principal objective of overcoming today's national challenges in air transportation. The SFW Reduced-Noise-Aircraft Technical Challenge aims to enable concepts and technologies to dramatically reduce the perceived aircraft noise outside of airport boundaries. This reduction of aircraft noise is critical for enabling the anticipated large increase in future air traffic. Noise generated in the jet engine core, by sources such as the compressor, combustor, and turbine, can be a significant contribution to the overall noise signature at low-power conditions, typical of approach flight. At high engine power during takeoff, jet and fan noise have traditionally dominated over core noise. However, current design trends and expected technological advances in engine-cycle design as well as noise-reduction methods are likely to reduce non-core noise even at engine-power points higher than approach. In addition, future low-emission combustor designs could increase

  7. Noise Gating Solar Images

    NASA Astrophysics Data System (ADS)

    DeForest, Craig; Seaton, Daniel B.; Darnell, John A.

    2017-08-01

    I present and demonstrate a new, general purpose post-processing technique, "3D noise gating", that can reduce image noise by an order of magnitude or more without effective loss of spatial or temporal resolution in typical solar applications.Nearly all scientific images are, ultimately, limited by noise. Noise can be direct Poisson "shot noise" from photon counting effects, or introduced by other means such as detector read noise. Noise is typically represented as a random variable (perhaps with location- or image-dependent characteristics) that is sampled once per pixel or once per resolution element of an image sequence. Noise limits many aspects of image analysis, including photometry, spatiotemporal resolution, feature identification, morphology extraction, and background modeling and separation.Identifying and separating noise from image signal is difficult. The common practice of blurring in space and/or time works because most image "signal" is concentrated in the low Fourier components of an image, while noise is evenly distributed. Blurring in space and/or time attenuates the high spatial and temporal frequencies, reducing noise at the expense of also attenuating image detail. Noise-gating exploits the same property -- "coherence" -- that we use to identify features in images, to separate image features from noise.Processing image sequences through 3-D noise gating results in spectacular (more than 10x) improvements in signal-to-noise ratio, while not blurring bright, resolved features in either space or time. This improves most types of image analysis, including feature identification, time sequence extraction, absolute and relative photometry (including differential emission measure analysis), feature tracking, computer vision, correlation tracking, background modeling, cross-scale analysis, visual display/presentation, and image compression.I will introduce noise gating, describe the method, and show examples from several instruments (including SDO

  8. Noise Reduction Techniques

    NASA Astrophysics Data System (ADS)

    Hallas, Tony

    There are two distinct kinds of noise - structural and color. Each requires a specific method of attack to minimize. The great challenge is to reduce the noise without reducing the faint and delicate detail in the image. My most-used and favorite noise suppression is found in Photoshop CS 5 Camera Raw. If I cannot get the desired results with the first choice, I will use Noise Ninja, which has certain advantages in some situations that we will cover.

  9. Rating helicopter noise

    NASA Technical Reports Server (NTRS)

    Leverton, J. W.; Southwood, B. J.; Pike, A. C.

    1978-01-01

    The effectiveness of the EPNL procedure in quantifying helicopter blade slap and tail rotor noise heard on approach some distance from the flyover position is addressed. Alternative methods of rating helicopter noise are reviewed including correction procedures to the EPNL concept which account for blade slap and tail rotor noise. The impact of the use of such corrections is examined.

  10. Characteristics of USB noise

    NASA Technical Reports Server (NTRS)

    Gibson, J. S.; Searle, N.

    1976-01-01

    An extensive series of noise measurements, for a variety of geometric and operational parameters, was made on models of upper surface blowing (USB) powered lift systems. The data obtained were analyzed and the effects and trends of parametric variation defined. The behavior and nature of USB noise and the design of USB systems with low noise characteristics is examined.

  11. Handbook of noise ratings

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    The handbook was compiled to provide information in a concise form, describing the multitude of noise rating schemes. It is hoped that by describing the noise rating methods in a single volume the user will have better access to the definitions, application and calculation procedures of the current noise rating methods.

  12. Dragline noise survey

    NASA Astrophysics Data System (ADS)

    Vipperman, Jeffrey S.; Bauer, Eric R.

    2002-05-01

    It is estimated that 70%-90% of miners have enough noise induced hearing loss (NIHL) to be classified as a disability (NIOSH, Publication No. 76-172, 1976; Franks, NIOSH Internal Report, 1996). In response, NIOSH is conducting a cross-sectional survey of the mining industry in order to determine the sources of mining noise and offer recommendations on how to mitigate high noise levels, and bring mining operations into compliance with the recent mining noise regulation: 30CFR, Part 62. This paper will outline the results from noise surveys of eight draglines which operate in above-ground coal mining operations. The data recorded include noise dosimetry in conjunction with time-at-task studies and 1/3-octave sound level (Leq, Lmin, and Lmax) measurements. The 1/3-octave band readings were used to create noise contour maps which allowed the spatial and frequency information of the noise to be considered. Comparison of Lmin and Lmax levels offer insight into the variability of the noise levels inside the dragline. The potential for administrative controls is limited due to consistently high noise levels throughout the deck. Implementation of engineering controls is also hindered by the size and number of the noise sources and the frequency content of the noise.

  13. Core Noise - Increasing Importance

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.

    2011-01-01

    This presentation is a technical summary of and outlook for NASA-internal and NASA-sponsored external research on core (combustor and turbine) noise funded by the Fundamental Aeronautics Program Subsonic Fixed Wing (SFW) Project. Sections of the presentation cover: the SFW system-level noise metrics for the 2015, 2020, and 2025 timeframes; turbofan design trends and their aeroacoustic implications; the emerging importance of core noise and its relevance to the SFW Reduced-Perceived-Noise Technical Challenge; and the current research activities in the core-noise area, with additional details given about the development of a high-fidelity combustor-noise prediction capability as well as activities supporting the development of improved reduced-order, physics-based models for combustor-noise prediction. The need for benchmark data for validation of high-fidelity and modeling work and the value of a potential future diagnostic facility for testing of core-noise-reduction concepts are indicated. The NASA Fundamental Aeronautics Program has the principal objective of overcoming today's national challenges in air transportation. The SFW Reduced-Perceived-Noise Technical Challenge aims to develop concepts and technologies to dramatically reduce the perceived aircraft noise outside of airport boundaries. This reduction of aircraft noise is critical to enabling the anticipated large increase in future air traffic. Noise generated in the jet engine core, by sources such as the compressor, combustor, and turbine, can be a significant contribution to the overall noise signature at low-power conditions, typical of approach flight. At high engine power during takeoff, jet and fan noise have traditionally dominated over core noise. However, current design trends and expected technological advances in engine-cycle design as well as noise-reduction methods are likely to reduce non-core noise even at engine-power points higher than approach. In addition, future low-emission combustor

  14. Classical noise, quantum noise and secure communication

    NASA Astrophysics Data System (ADS)

    Tannous, C.; Langlois, J.

    2016-01-01

    Secure communication based on message encryption might be performed by combining the message with controlled noise (called pseudo-noise) as performed in spread-spectrum communication used presently in Wi-Fi and smartphone telecommunication systems. Quantum communication based on entanglement is another route for securing communications as demonstrated by several important experiments described in this work. The central role played by the photon in unifying the description of classical and quantum noise as major ingredients of secure communication systems is highlighted and described on the basis of the classical and quantum fluctuation dissipation theorems.

  15. [Cardiovascular effects of noise].

    PubMed

    Vacheron, A

    1992-03-01

    The circulatory response to noise is dominated by a peripheral blood vessels vasoconstriction, of greater magnitude when asleep than awake. Noise of lower frequency seems more able to produce this response. With repetition of the noise, adaptation and tolerance to it quickly appears. Meanwhile prolonged high level noise exposition induces an increasing prevalence of arterial hypertension among industrial workers. This increase is also clearly found in residential communities living near airports. Long-term exposure to noise is a dangerous nuisance, that can lead to an increase in arterial blood pressure and favour coronary artery disease development.

  16. 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.

  17. Optical Johnson noise thermometry

    NASA Technical Reports Server (NTRS)

    Shepard, R. L.; Blalock, T. V.; Maxey, L. C.; Roberts, M. J.; Simpson, M. L.

    1989-01-01

    A concept is being explored that an optical analog of the electrical Johnson noise may be used to measure temperature independently of emissivity. The concept is that a laser beam may be modulated on reflection from a hot surface by interaction of the laser photons with the thermally agitated conduction electrons or the lattice phonons, thereby adding noise to the reflected laser beam. If the reflectance noise can be detected and quantified in a background of other noise in the optical and signal processing systems, the reflectance noise may provide a noncontact measurement of the absolute surface temperature and may be independent of the surface's emissivity.

  18. Interpreting Transistor Noise

    NASA Astrophysics Data System (ADS)

    Pospieszalski, M. W.

    2010-10-01

    The simple noise models of field effect and bipolar transistors reviewed in this article are quite useful in engineering practice, as illustrated by measured and modeled results. The exact and approximate expressions for the noise parameters of FETs and bipolar transistors reveal certain common noise properties and some general noise properties of both devices. The usefulness of these expressions in interpreting the dependence of measured noise parameters on frequency, bias, and temperature and, consequently, in checking of consistency of measured data has been demonstrated.

  19. Core Noise Reduction

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.

    2011-01-01

    This presentation is a technical summary of and outlook for NASA-internal and NASA-sponsored external research on core (combustor and turbine) noise funded by the Fundamental Aeronautics Program Subsonic Fixed Wing (SFW) Project. Sections of the presentation cover: the SFW system-level noise metrics for the 2015, 2020, and 2025 timeframes; turbofan design trends and their aeroacoustic implications; the emerging importance of core noise and its relevance to the SFW Reduce-Perceived-Noise Technical Challenge; and the current research activities in the core noise area. Recent work1 on the turbine-transmission loss of combustor noise is briefly described, two2,3 new NRA efforts in the core-noise area are outlined, and an effort to develop CMC-based acoustic liners for broadband noise reduction suitable for turbofan-core application is delineated. The NASA Fundamental Aeronautics Program has the principal objective of overcoming today's national challenges in air transportation. The reduction of aircraft noise is critical to enabling the anticipated large increase in future air traffic. The Subsonic Fixed Wing Project's Reduce-Perceived-Noise Technical Challenge aims to develop concepts and technologies to dramatically reduce the perceived aircraft noise outside of airport boundaries.

  20. Core-Noise Research

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.

    2012-01-01

    This presentation is a technical summary of and outlook for NASA-internal and NASA-sponsored external research on core noise funded by the Fundamental Aeronautics Program Subsonic Fixed Wing (SFW) Project. Sections of the presentation cover: the SFW system-level noise metrics for the 2015 (N+1), 2020 (N+2), and 2025 (N+3) timeframes; SFW strategic thrusts and technical challenges; SFW advanced subsystems that are broadly applicable to N+3 vehicle concepts, with an indication where further noise research is needed; the components of core noise (compressor, combustor and turbine noise) and a rationale for NASA's current emphasis on the combustor-noise component; the increase in the relative importance of core noise due to turbofan design trends; the need to understand and mitigate core-noise sources for high-efficiency small gas generators; and the current research activities in the core-noise area, with additional details given about forthcoming updates to NASA's Aircraft Noise Prediction Program (ANOPP) core-noise prediction capabilities, two NRA efforts (Honeywell International, Phoenix, AZ and University of Illinois at Urbana-Champaign, respectively) to improve the understanding of core-noise sources and noise propagation through the engine core, and an effort to develop oxide/oxide ceramic-matrix-composite (CMC) liners for broadband noise attenuation suitable for turbofan-core application. Core noise must be addressed to ensure that the N+3 noise goals are met. Focused, but long-term, core-noise research is carried out to enable the advanced high-efficiency small gas-generator subsystem, common to several N+3 conceptual designs, needed to meet NASA's technical challenges. Intermediate updates to prediction tools are implemented as the understanding of the source structure and engine-internal propagation effects is improved. The NASA Fundamental Aeronautics Program has the principal objective of overcoming today's national challenges in air transportation. The

  1. Jet Noise Research at NASA

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda

    2008-01-01

    A presentation outlining current jet noise work at NASA was given at the NAVAIR Noise Workshop. Jet noise tasks in the Supersonics project of the Fundamental Aeronautics program were highlighted. The presentation gave an overview of developing jet noise reduction technologies and noise prediction capabilities. Advanced flow and noise diagnostic tools were also presented.

  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. Hot topics in noise

    NASA Astrophysics Data System (ADS)

    Stinson, Michael R.

    2003-10-01

    Our world continues to be a noisy place and the challenge to ``increase and diffuse knowledge of noise propagation, passive and active noise control, and the effects of noise'' remains. In the last several years, noise in the classroom has emerged as one of the hotter topics: Considerable progress has been made in the underpinning research, the formulation of recommendations, and the process of educating society on the social and personal impact of inadequate acoustical conditions in classrooms. The establishment of the ANSI S12.60-2002 standard for classroom acoustics was a milestone event. Noise in cities and the understanding of our soundscapes are subjects of ongoing significance. The development of standards and regulations is a continuing process, with urban community noise regulations, aviation noise, and the preservation of natural quiet in national parks being of current concern. New methods to reduce noise are under development and include passive and active methods of noise control, techniques for modeling the performance of noise barriers, and approaches for designing product sound quality.

  4. Noise Mapping and Annoyance.

    PubMed

    Knauss, D.

    2002-01-01

    The EC has published a Green Paper on noise policy in the EU and has issued a directive on the assessment and reduction of environmental noise. This directive will make noise mapping mandatory for cities with at least 250.000 inhabitants. Due to the development in computer technology it is possible to calculate noise maps for large urban areas using the available data on buildings, ground profile, road and rail traffic. Examples for noise mapping are Birmingham (GB), Linz (A) and various German cities. Based on noise maps and empirical data on the correlation between annoyance and noise levels annoyance maps for different sources (rail, road, aircraft) can be calculated. Under the assumption that the annoyance for the different sources are only weakly correlated, a combined annoyance map can be calculated. In a second step using the distribution of the population the actual number of annoyed people can be evaluated. This analysis can be used, for example, to identify noise hot spots and to assess the impact of major traffic projects - roads, airports- on the noise situation as well as the impact on the population. Furthermore, the combined annoyance maps can be used to investigate on health effects and to check whether or not empirical correlations between annoyance and noise levels are sufficiently correct.

  5. Optical Dipole Noise.

    NASA Astrophysics Data System (ADS)

    Bacon, Allan Mclain

    1995-01-01

    Optical dipole fluctuations in atoms play an important role in diverse physical phenomena: they limit the signal to background ratio in spectroscopic measurements, and thus limit the accuracy of atomic clocks; they determine the minimum temperature that can be obtained in laser cooling and in optical traps; and, they place a limit on squeezed state experiments. Although there have been many theoretical and experimental studies of noise in radiating atomic systems, the previous work has not provided a complete physical picture of the distinct sources of optical dipole noise. Hence, a detailed study of optical dipole fluctuations in a simple radiating system is of fundamental and pedagogical value. This dissertation presents measurements of optical dipole noise in a particularly simple system consisting of long-lived, coherently driven two-level atoms in an atomic beam. We use atoms with a long radiative lifetime, because the small spontaneous emission rate permits analysis of the noise spectra in terms of a simple fluctuating Bloch vector picture, without decay. The observed noise spectra exhibit manifestly different structure for radiation which is in-phase or out-of-phase with the driving field. The spectra and corresponding analysis afford clear insights into the roles played by three distinct sources of atomic noise: Spontaneous emission, phase-dependent Bloch vector projection noise, and phase-dependent mean dipole Poisson noise. Spontaneous emission and phase-dependent Bloch vector projection noise arise from quantum fluctuations in the optical dipole moment of single atoms. Phase-dependent mean dipole Poisson noise arises from fluctuations in the number of radiating atoms. Two novel experimental techniques permit sensitive measurement of optical dipole noise. First, the signals from two identically prepared experimental regions are subtracted. This method cancels the excess noise in the measured quadrature signal in addition to canceling the excess noise in

  6. Propulsion systems noise technology

    NASA Technical Reports Server (NTRS)

    Feiler, C. E.

    1978-01-01

    Turbofan engine noise research relevant to conventional aircraft is discussed. In the area of fan noise, static to flight noise differences were discussed and data were presented for two different ways of simulating flight behavior. Experimental results from a swept rotor fan design are presented which show that this concept has potential for reducing the multiple-pure-tone or buzz-saw noise related to the shock waves on a fan operating at supersonic tip speeds. Acoustic suppressor research objectives centered around the effect of the wave system generated by the fan stage that is the input to the treatment. A simplifying and unifying parameter, mode cutoff ratio was described. Results are presented which show that suppressor performance can be improved if the input wave is more precisely described. In jet noise, calculated results showing the potential noise reduction from the use of internal mixer nozzles rather than separate flow nozzles are presented.

  7. Noise and gastric secretion.

    PubMed

    Tomei, F; Papaleo, B; Baccolo, T P; Persechino, B; Spanò, G; Rosati, M V

    1994-09-01

    In view of the increasing incidence of diseases such as gastritis and ulcers in workers exposed to noise, we assessed whether noise does in fact affect gastric secretion. Then, considering the conflicting findings published on the effects of noise on gastric secretion, we also investigated whether the response was related to differences in baseline secretion, and whether it was further modified by a hydroalcoholic meal. We studied 50 dyspeptic subjects engaged in various types of work but not occupationally exposed to noise. They were exposed to a "pink noise" stimulus of 95 dB administered through earphones, lasting 15 minutes. Gastric secretion sometimes remained unchanged, sometimes increased, or sometimes even decreased in relation to the baseline hydrochloric acid secretion. The hydroalcoholic meal did not generally modify the effects of noise. These findings might help explain the differences in previous reports on this question.

  8. 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.

  9. Poultry Plant Noise Control

    NASA Technical Reports Server (NTRS)

    1982-01-01

    A demonstration conducted last winter at the Tip Top Poultry Plant intended to show poultry plant managers from all over the U.S. potential solutions to the problem of plant noise. Plastic covers used over sound absorbing materials need to meet cleanability requirements, high- pressure water cleaning and other harsh maintenance procedures peculiar to the poultry processing industry. For the demonstration, Fiber Flex, Inc. manufactured and donated 750 noise panels; Owens-Corning Fiberglas Corporation donated the fiberglas cores; and the cover material was purchased from Howe and Bainbridge. The Engineering Experiment Station (EES) conducted before and after noise surveys and is evaluating the effect of noise reduction on turnover and productivity in the demonstration plant. EES plans to conduct a noise abatement workshop and update a handbook to help poultry processors with noise problems. EES study and demonstration may be applicable to other food processing plants where similar sanitary constraints exist.

  10. Understanding Slat Noise Sources

    NASA Technical Reports Server (NTRS)

    Khorrami, Medhi R.

    2003-01-01

    Model-scale aeroacoustic tests of large civil transports point to the leading-edge slat as a dominant high-lift noise source in the low- to mid-frequencies during aircraft approach and landing. Using generic multi-element high-lift models, complementary experimental and numerical tests were carefully planned and executed at NASA in order to isolate slat noise sources and the underlying noise generation mechanisms. In this paper, a brief overview of the supporting computational effort undertaken at NASA Langley Research Center, is provided. Both tonal and broadband aspects of slat noise are discussed. Recent gains in predicting a slat s far-field acoustic noise, current shortcomings of numerical simulations, and other remaining open issues, are presented. Finally, an example of the ever-expanding role of computational simulations in noise reduction studies also is given.

  11. Poultry Plant Noise Control

    NASA Astrophysics Data System (ADS)

    1982-01-01

    A demonstration conducted last winter at the Tip Top Poultry Plant intended to show poultry plant managers from all over the U.S. potential solutions to the problem of plant noise. Plastic covers used over sound absorbing materials need to meet cleanability requirements, high- pressure water cleaning and other harsh maintenance procedures peculiar to the poultry processing industry. For the demonstration, Fiber Flex, Inc. manufactured and donated 750 noise panels; Owens-Corning Fiberglas Corporation donated the fiberglas cores; and the cover material was purchased from Howe and Bainbridge. The Engineering Experiment Station (EES) conducted before and after noise surveys and is evaluating the effect of noise reduction on turnover and productivity in the demonstration plant. EES plans to conduct a noise abatement workshop and update a handbook to help poultry processors with noise problems. EES study and demonstration may be applicable to other food processing plants where similar sanitary constraints exist.

  12. Prediction of airframe noise

    NASA Technical Reports Server (NTRS)

    Hardin, J. C.; Fratello, D. J.; Hayden, R. E.; Kadman, Y.; Africk, S.

    1975-01-01

    Methods of predicting airframe noise generated by aircraft in flight under nonpowered conditions are discussed. Approaches to predictions relying on flyover data and component theoretical analyses are developed. A nondimensional airframe noise spectrum of various aircraft is presented. The spectrum was obtained by smoothing all the measured spectra to remove any peculiarities due to airframe protrusions, normalizing each spectra by its overall sound pressure level and a characteristics frequency, and averaging the spectra together. A chart of airframe noise sources is included.

  13. Landing gear noise attenuation

    NASA Technical Reports Server (NTRS)

    Moe, Jeffrey W. (Inventor); Whitmire, Julia (Inventor); Kwan, Hwa-Wan (Inventor); Abeysinghe, Amal (Inventor)

    2011-01-01

    A landing gear noise attenuator mitigates noise generated by airframe deployable landing gear. The noise attenuator can have a first position when the landing gear is in its deployed or down position, and a second position when the landing gear is in its up or stowed position. The noise attenuator may be an inflatable fairing that does not compromise limited space constraints associated with landing gear retraction and stowage. A truck fairing mounted under a truck beam can have a compliant edge to allow for non-destructive impingement of a deflected fire during certain conditions.

  14. 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.

  15. Noise in biological circuits

    SciTech Connect

    Simpson, Michael L.; Allen, Michael S.; Cox, Chris D.; Dar, Roy D.; Karig, David K.; McCollum, James M.; Cooke, John F.

    2009-01-13

    Noise biology focuses on the sources, processing, and biological consequences of the inherent stochastic fluctuations in molecular transitions or interactions that control cellular behavior. These fluctuations are especially pronounced in small systems where the magnitudes of the fluctuations approach or exceed the mean value of the molecular population. Noise biology is an essential component of nanomedicine where the communication of information is across a boundary that separates small synthetic and biological systems that are bound by their size to reside in environments of large fluctuations. Here we review the fundamentals of the computational, analytical, and experimental approaches to noise biology. We review results that show that the competition between the benefits of low noise and those of low population has resulted in the evolution of genetic system architectures that produce an uneven distribution of stochasticity across the molecular components of cells and, in some cases, use noise to drive biological function. We review the exact and approximate approaches to gene circuit noise analysis and simulation, and reviewmany of the key experimental results obtained using flow cytometry and time-lapse fluorescent microscopy. In addition, we consider the probative value of noise with a discussion of using measured noise properties to elucidate the structure and function of the underlying gene circuit. Lastly, we conclude with a discussion of the frontiers of and significant future challenges for noise biology.

  16. Reliability, synchrony and noise

    PubMed Central

    Ermentrout, G. Bard; Galán, Roberto F.; Urban, Nathaniel N.

    2008-01-01

    The brain is noisy. Neurons receive tens of thousands of highly fluctuating inputs and generate spike trains that appear highly irregular. Much of this activity is spontaneous—uncoupled to overt stimuli or motor outputs—leading to questions about the functional impact of this noise. Although noise is most often thought of as disrupting patterned activity and interfering with the encoding of stimuli, recent theoretical and experimental work has shown that noise can play a constructive role—leading to increased reliability or regularity of neuronal firing in single neurons and across populations. These results raise fundamental questions about how noise can influence neural function and computation. PMID:18603311

  17. Understanding jet noise.

    PubMed

    Karabasov, S A

    2010-08-13

    Jets are one of the most fascinating topics in fluid mechanics. For aeronautics, turbulent jet-noise modelling is particularly challenging, not only because of the poor understanding of high Reynolds number turbulence, but also because of the extremely low acoustic efficiency of high-speed jets. Turbulent jet-noise models starting from the classical Lighthill acoustic analogy to state-of-the art models were considered. No attempt was made to present any complete overview of jet-noise theories. Instead, the aim was to emphasize the importance of sound generation and mean-flow propagation effects, as well as their interference, for the understanding and prediction of jet noise.

  18. Sounds and Noises. A Position Paper on Noise Pollution.

    ERIC Educational Resources Information Center

    Chapman, Thomas L.

    This position paper focuses on noise pollution and the problems and solutions associated with this form of pollution. The paper is divided into the following five sections: Noise and the Ear, Noise Measurement, III Effects of Noise, Acoustics and Action, and Programs and Activities. The first section identifies noise and sound, the beginnings of…

  19. Jet noise suppression

    NASA Astrophysics Data System (ADS)

    Gliebe, P. R.; Brausch, J. F.; Majjigi, R. K.; Lee, R.

    1991-08-01

    The objectives of this chapter are to review and summarize the jet noise suppression technology, to provide a physical and theoretical model to explain the measured jet noise suppression characteristics of different concepts, and to provide a set of guidelines for evolving jet noise suppression designs. The underlying principle for all jet noise suppression devices is to enhance rapid mixing (i.e., diffusion) of the jet plume by geometric and aerothermodynamic means. In the case of supersonic jets, the shock-cell broadband noise reduction is effectively accomplished by the elimination or mitigation of the shock-cell structure. So far, the diffusion concepts have predominantly concentrated on jet momentum and energy (kinetic and thermal) diffusion, in that order, and have yielded better noise reduction than the simple conical nozzles. A critical technology issue that needs resolution is the effect of flight on the noise suppression potential of mechanical suppressor nozzles. A more thorough investigation of this mechanism is necessary for the successful development and design of an acceptable noise suppression device for future high-speed civil transports.

  20. Jet Noise Suppression

    NASA Technical Reports Server (NTRS)

    Gliebe, P. R.; Brausch, J. F.; Majjigi, R. K.; Lee, R.

    1991-01-01

    The objectives of this chapter are to review and summarize the jet noise suppression technology, to provide a physical and theoretical model to explain the measured jet noise suppression characteristics of different concepts, and to provide a set of guidelines for evolving jet noise suppression designs. The underlying principle for all jet noise suppression devices is to enhance rapid mixing (i.e., diffusion) of the jet plume by geometric and aerothermodynamic means. In the case of supersonic jets, the shock-cell broadband noise reduction is effectively accomplished by the elimination or mitigation of the shock-cell structure. So far, the diffusion concepts have predominantly concentrated on jet momentum and energy (kinetic and thermal) diffusion, in that order, and have yielded better noise reduction than the simple conical nozzles. A critical technology issue that needs resolution is the effect of flight on the noise suppression potential of mechanical suppressor nozzles. A more thorough investigation of this mechanism is necessary for the successful development and design of an acceptable noise suppression device for future high-speed civil transports.

  1. Noise Pollution, Teachers' Edition.

    ERIC Educational Resources Information Center

    O'Donnell, Patrick A.; Lavaroni, Charles W.

    One of three in a series about pollution, this teacher's guide for a unit on noise pollution is designed for use in junior high school grades. It offers suggestions for extending the information and activities contained in the textual material for students. Chapter 1 discusses the problem of noise pollution and involves students in processes of…

  2. Speech communications in noise

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The physical characteristics of speech, the methods of speech masking measurement, and the effects of noise on speech communication are investigated. Topics include the speech signal and intelligibility, the effects of noise on intelligibility, the articulation index, and various devices for evaluating speech systems.

  3. Speech communications in noise

    NASA Astrophysics Data System (ADS)

    1984-07-01

    The physical characteristics of speech, the methods of speech masking measurement, and the effects of noise on speech communication are investigated. Topics include the speech signal and intelligibility, the effects of noise on intelligibility, the articulation index, and various devices for evaluating speech systems.

  4. Sounding Off about Noise

    ERIC Educational Resources Information Center

    Crumpton, Michael A.

    2005-01-01

    Noise in a community college library can be part of the nature of the environment. It can also become a huge distraction for those who see the library as their sanctuary for quiet study and review of resources. This article describes the steps that should be taken by library staff in order to be proactive about noise and the library environment,…

  5. Speech communications in noise

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The physical characteristics of speech, the methods of speech masking measurement, and the effects of noise on speech communication are investigated. Topics include the speech signal and intelligibility, the effects of noise on intelligibility, the articulation index, and various devices for evaluating speech systems.

  6. Noise: The Ignored Contaminant

    ERIC Educational Resources Information Center

    Miller, Maurice H.

    1977-01-01

    Noise is the single most omnipresent noxious contaminant in the American environment, yet little attention has been paid to its dangers and relatively small amounts of money spent to control it. Compares the effects and management of hearing impairment due to noise with those resulting from other causes. (Editor)

  7. Helicopter noise certification

    NASA Astrophysics Data System (ADS)

    Kearsey, P. R.

    The paper describes the noise certification requirements for helicopters adopted by ICAO in 1981 and points out differences between the ICAO standards and the American requirements. Described in detail are the reference procedures for take-off, overflight, and approach; the noise limits; test procedures; the noise unit; the adjustment to test data; computations of noise certification levels; and validation of the noise certification standard. A simplified scheme, agreed upon at the December 1991 meeting of the ICAO Committee on Aviation Environmental Protection, applicable to helicopters with a take-off mass of less than 2730 kg, is described. The scheme uses the sound exposure level (SEL) as the unit of measure, thereby eliminating the need for one third octave analysis and enabling the use of an integrating sound level meter which will give the measured SEL directly.

  8. Noise in coevolving networks

    NASA Astrophysics Data System (ADS)

    Diakonova, Marina; Eguíluz, Víctor M.; San Miguel, Maxi

    2015-09-01

    Coupling dynamics of the states of the nodes of a network to the dynamics of the network topology leads to generic absorbing and fragmentation transitions. The coevolving voter model is a typical system that exhibits such transitions at some critical rewiring. We study the robustness of these transitions under two distinct ways of introducing noise. Noise affecting all the nodes destroys the absorbing-fragmentation transition, giving rise in finite-size systems to two regimes: bimodal magnetization and dynamic fragmentation. Noise targeting a fraction of nodes preserves the transitions but introduces shattered fragmentation with its characteristic fraction of isolated nodes and one or two giant components. Both the lack of absorbing state for homogeneous noise and the shift in the absorbing transition to higher rewiring for targeted noise are supported by analytical approximations.

  9. Jet Noise Research at NASA

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda S.; Huff,Dennis

    2009-01-01

    A presentation outlining current jet noise work at NASA was given to the Naval Research Advisory Committee. Jet noise tasks in the Supersonics project of the Fundamental Aeronautics program were highlighted. The presentation gave an overview of developing jet noise reduction technologies and noise prediction capabilities. Advanced flow and noise diagnostic tools were also presented.

  10. 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.

  11. [The fetus and noise].

    PubMed

    Brezinka, C; Lechner, T; Stephan, K

    1997-01-01

    From 23 weeks of gestation some and from 28 weeks all healthy fetuses are capable of reacting to sound stimulation. The intrauterine acoustic environment is dominated by maternal sounds--heartbeat, breathing, the mother's voice, borborygmi and sounds caused by body movements. Background noise is never below 28 dB and can rise to 84 dB when the mother is singing. Noises that are meant to reach the fetus must be louder than the background noise and must be of low frequency as high frequency sounds are damped by maternal tissue. Vibroacoustic stimulation tests (VAST) have become popular in pregnancy surveillance over the last 20 years, mostly using an artificial larynx. Advantages and problems of the various VAST protocols in fetal monitoring are discussed in the light of animal experiments and clinical studies. Health legislation laws in most countries forbid pregnant women to work in surroundings with a high noise level (80 dB continuous noise and/or rapid impulse noise changes of 40 dB). Whereas regulations for pregnant women are easy to enforce in industry, pregnant women employed in discos or performing as musicians spend most of their working day exposed to noise impact higher than the recommended limit.

  12. Nature of orchestral noise.

    PubMed

    O'Brien, Ian; Wilson, Wayne; Bradley, Andrew

    2008-08-01

    Professional orchestral musicians are at risk of exposure to excessive noise when at work. This is an industry-wide problem that threatens not only the hearing of orchestral musicians but also the way orchestras operate. The research described in this paper recorded noise levels within a professional orchestra over three years in order to provide greater insight to the orchestral noise environment; to guide future research into orchestral noise management and hearing conservation strategies; and to provide a basis for the future education of musicians and their managers. Every rehearsal, performance, and recording from May 2004 to May 2007 was monitored, with the woodwind, brass, and percussion sections monitored in greatest detail. The study recorded dBALEQ and dBC peak data, which are presented in graphical form with accompanying summarized data tables. The findings indicate that the principal trumpet, first and third horns, and principal trombone are at greatest risk of exposure to excessive sustained noise levels and that the percussion and timpani are at greatest risk of exposure to excessive peak noise levels. However, the findings also strongly support the notion that the true nature of orchestral noise is a great deal more complex than this simple statement would imply.

  13. Analyzing nocturnal noise stratification.

    PubMed

    Rey Gozalo, Guillermo; Barrigón Morillas, Juan Miguel; Gómez Escobar, Valentín

    2014-05-01

    Pollution associated to traffic can be considered as one of the most relevant pollution sources in our cities; noise is one of the major components of traffic pollution; thus, efforts are necessary to search adequate noise assessment methods and low pollution city designs. Different methods have been proposed for the evaluation of noise in cities, including the categorization method, which is based on the functionality concept. Until now, this method has only been studied (with encouraging results) for short-term, diurnal measurements, but nocturnal noise presents a behavior clearly different on respect to the diurnal one. In this work 45 continuous measurements of approximately one week each in duration are statistically analyzed to identify differences between the proposed categories. The results show that the five proposed categories highlight the noise stratification of the studied city in each period of the day (day, evening, and night). A comparison of the continuous measurements with previous short-term measurements indicates that the latter can be a good approximation of the former in diurnal period, reducing the resource expenditure for noise evaluation. Annoyance estimated from the measured noise levels was compared with the response of population obtained from a questionnaire with good agreement. The categorization method can yield good information about the distribution of a pollutant associated to traffic in our cities in each period of the day and, therefore, is a powerful tool for town planning and the design of pollution prevention policies.

  14. Noise and Phase Transitions

    NASA Astrophysics Data System (ADS)

    Chen, Zhi; Yu, Clare C.

    2006-03-01

    Noise is present in many physical systems and is often viewed as a nuisance. Yet it can also be a probe of microscopic fluctuations. There have been indications recently that the noise in the resistivity increases in the vicinity of the metal-insulator transition. But what are the characteristics of the noise associated with well-understood first and second order phase transitions? It is well known that critical fluctuations are associated with second order phase transitions, but do these fluctuations lead to enhanced noise? We have addressed these questions using Monte Carlo simulations to study the noise in the 2D Ising model which undergoes a second order phase transition, and in the 5-state Potts model which undergoes a first order phase transition. We monitor these systems as the temperature drops below the critical temperature. At each temperature, after equilibration is established, we obtain the time series of quantities characterizing the properties of the system, i.e., the energy and magnetization per site. We apply different methods, such as the noise power spectrum, the Detrended Fluctuation Analysis (DFA) and the second spectrum of the noise, to analyze the fluctuations in these quantities.

  15. Broadband rotor noise analyses

    NASA Technical Reports Server (NTRS)

    George, A. R.; Chou, S. T.

    1984-01-01

    The various mechanisms which generate broadband noise on a range of rotors studied include load fluctuations due to inflow turbulence, due to turbulent boundary layers passing the blades' trailing edges, and due to tip vortex formation. Existing analyses are used and extensions to them are developed to make more accurate predictions of rotor noise spectra and to determine which mechanisms are important in which circumstances. Calculations based on the various prediction methods in existing experiments were compared. The present analyses are adequate to predict the spectra from a wide variety of experiments on fans, full scale and model scale helicopter rotors, wind turbines, and propellers to within about 5 to 10 dB. Better knowledge of the inflow turbulence improves the accuracy of the predictions. Results indicate that inflow turbulence noise depends strongly on ambient conditions and dominates at low frequencies. Trailing edge noise and tip vortex noise are important at higher frequencies if inflow turbulence is weak. Boundary layer trailing edge noise, important, for large sized rotors, increases slowly with angle of attack but not as rapidly as tip vortex noise.

  16. Noise contaminated transmittance

    SciTech Connect

    Zardecki, A.; McVey, B.D.; Nelson, D.H.

    1997-09-01

    The authors compare the efficiency of a classifier based on probabilistic neural networks and the general least squares method. Both methods must accommodate noise due to uncertainty in the measured spectrum at each wavelength. The evaluation of both methods is based on a simulated transmittance spectrum, in which the received signal is supplemented by an additive admixture of noise. To obtain a realistic description of the noise model, they generate several hundred laser pulses for each wavelength under consideration. These pulses have a predetermined correlation matrix for different wavelengths; furthermore, they are composed of three components accounting for the randomness of the observed spectrum. The first component is the correlated 1/f noise; the second component is due to uncorrelated 1/f noise; the third one is the uncorrelated white noise. The probabilistic neural network fails to retrieve the species concentration correctly for large noise levels; on the other hand, its predictions being confined to a fixed number of concentration bins, the network produces relatively small variances. To a large extent, the general least square method avoids the false alarms. It reproduces the average concentrations correctly; however, the concentration variances can be large.

  17. Fan Noise Test Facility

    NASA Image and Video Library

    1969-01-21

    The Fan Noise Test Facility built at the Lewis Research Center to obtain far-field noise data for the National Aeronautics and Space Administration (NASA) and General Electric Quiet Engine Program. The engine incorporated existing noise reduction methods into an engine of similar power to those that propelled the Boeing 707 or McDonnell-Douglas DC-8 airliner. The new the low-bypass ratio turbofan engines of the 1960s were inherently quieter than their turbojet counterparts, researchers had a better grasp of the noise generation problem, and new acoustic technologies had emerged. Lewis contracted General Electric in 1969 to build and aerodynamically test three experimental engines with 72-inch diameter fans. The engines were then brought to Lewis and tested with an acoustically treated nacelle. This Fan Noise Test Facility was built off of the 10- by 10-Foot Supersonic Wind Tunnel’s Main Compressor and Drive Building. Lewis researchers were able to isolate the fan’s noise during these initial tests by removing the core of the engine. The Lewis test rig drove engines to takeoff tip speeds of 1160 feet per second. The facility was later used to test a series of full-scale model fans and fan noise suppressors to be used with the quiet engine. NASA researchers predicted low-speed single-stage fans without inlet guide vanes and with large spacing between rotors and stators would be quieter. General Electric modified a TF39 turbofan engine by removing the the outer protion of the fan and spacing the blade rows of the inner portion. The tests revealed that the untreated version of the engine generated less noise than was anticipated, and the acoustically treated nacelle substantially reduced engine noise.

  18. 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.

  19. Control of jet noise

    NASA Technical Reports Server (NTRS)

    Schreck, Stefan

    1992-01-01

    To investigate the possibility of active control of jet noise, knowledge of the noise generation mechanisms in natural jets is essential. Once these mechanisms are determined, active control can be used to manipulate the noise production processes. We investigated the evolution of the flow fields and the acoustic fields of rectangular and circular jets. A predominant flapping mode was found in the supersonic rectangular jets. We hope to increase the spreading of supersonic jets by active control of the flapping mode found in rectangular supersonic jets.

  20. Blown flap noise prediction

    NASA Technical Reports Server (NTRS)

    Reddy, N. N.

    1978-01-01

    Theoretical and experimental developments of flow-surface interaction noise with a particular emphasis on blown-flap noise were reviewed. Several blown-flap noise prediction methods were evaluated by comparing predicted acoustic levels, directivity, and spectra with a recently obtained data base. A prediction method was selected and a detailed step-by-step description of this method was provided to develop a computer module to calculate one-third octave band frequency spectra at any given location in the far-field for under-the-wing and upper surface blown configurations as a function of geometric and operational parameters.

  1. Quantum phase slip noise

    NASA Astrophysics Data System (ADS)

    Semenov, Andrew G.; Zaikin, Andrei D.

    2016-07-01

    Quantum phase slips (QPSs) generate voltage fluctuations in superconducting nanowires. Employing the Keldysh technique and making use of the phase-charge duality arguments, we develop a theory of QPS-induced voltage noise in such nanowires. We demonstrate that quantum tunneling of the magnetic flux quanta across the wire yields quantum shot noise which obeys Poisson statistics and is characterized by a power-law dependence of its spectrum SΩ on the external bias. In long wires, SΩ decreases with increasing frequency Ω and vanishes beyond a threshold value of Ω at T →0 . The quantum coherent nature of QPS noise yields nonmonotonous dependence of SΩ on T at small Ω .

  2. Propfan noise propagation

    NASA Technical Reports Server (NTRS)

    George, Albert R.; Sim, Ben WEL-C.

    1993-01-01

    The unconventional supersonic tip speed of advanced propellers has led to uncertainties about Propfan's noise acceptability and compliance with Federal Aviation Noise Regulation (FAR 36). Overhead flight testing of the Propfan with an SR-7L blade during 1989's Propfan Test Assessment (PTA) Program have shown unexpectedly high far-field sound pressure levels. This study here attempts to provide insights into the acoustics of a single-rotating propeller (SRP) with supersonic tip speed. At the same time, the role of the atmosphere in shaping the far-field noise characteristics is investigated.

  3. Hypermedicalization in White Noise.

    PubMed

    Benson, Josef

    2015-09-01

    The Nazis hijacked Germany's medical establishment and appropriated medical language to hegemonize their ideology. In White Noise, shifting medical information stifles the public into docility. In Nazi Germany the primacy of language and medical authority magnified the importance of academic doctors. The muddling of identities caused complex insecurities and the need for psychological doubles. In White Noise, Professor Gladney is driven by professional insecurities to enact a double in Murray. Through the manipulation of language and medical overreach the U.S., exemplified in the novel White Noise, has become a hypermedicalized society where the spirit of the Hippocratic Oath has eroded.

  4. Reduction of propeller noise by active noise control

    NASA Astrophysics Data System (ADS)

    Bschorr, O.; Kubanke, D.

    1992-04-01

    Active noise control, a method of cancelling noise by means of interference with a secondary anti-noise source, is now in full development. The first commercial application of this technique is in the case of active electronically controlled head sets. The next step will be the active noise cancellation in air ducts and in passenger cabins. The aim of this paper is to assess the possibilities of the anti-noise technique for reducing propeller noise. First, by a mathematical simulation the theoretical noise reduction on the ground was calculated and found to be promising for further investigations. In the case of the periodic engine and propeller noise, for example, with only a single anti-noise source, the noise foot prints of the lower propeller harmonics can be reduced by up to 10 dB. In laboratory tests the theoretical values will be confirmed experimentally. For cancellation of the periodic noise one can use synchronous anti-noise generators. Compared with the engine and propeller noise the reduction of jet noise by the anti-noise technique is much more difficult. Therefore a sensor and controlling unit are necessary because of the stochastic nature of jet noise. Since aircraft noise is a severe problem, all methods are to be considered.

  5. Cochlear implant optimized noise reduction

    NASA Astrophysics Data System (ADS)

    Mauger, Stefan J.; Arora, Komal; Dawson, Pam W.

    2012-12-01

    Noise-reduction methods have provided significant improvements in speech perception for cochlear implant recipients, where only quality improvements have been found in hearing aid recipients. Recent psychoacoustic studies have suggested changes to noise-reduction techniques specifically for cochlear implants, due to differences between hearing aid recipient and cochlear implant recipient hearing. An optimized noise-reduction method was developed with significantly increased temporal smoothing of the signal-to-noise ratio estimate and a more aggressive gain function compared to current noise-reduction methods. This optimized noise-reduction algorithm was tested with 12 cochlear implant recipients over four test sessions. Speech perception was assessed through speech in noise tests with three noise types; speech-weighted noise, 20-talker babble and 4-talker babble. A significant speech perception improvement using optimized noise reduction over standard processing was found in babble noise and speech-weighted noise and over a current noise-reduction method in speech-weighted noise. Speech perception in quiet was not degraded. Listening quality testing for noise annoyance and overall preference found significant improvements over the standard processing and over a current noise-reduction method in speech-weighted and babble noise types. This optimized method has shown significant speech perception and quality improvements compared to the standard processing and a current noise-reduction method.

  6. Cochlear implant optimized noise reduction.

    PubMed

    Mauger, Stefan J; Arora, Komal; Dawson, Pam W

    2012-12-01

    Noise-reduction methods have provided significant improvements in speech perception for cochlear implant recipients, where only quality improvements have been found in hearing aid recipients. Recent psychoacoustic studies have suggested changes to noise-reduction techniques specifically for cochlear implants, due to differences between hearing aid recipient and cochlear implant recipient hearing. An optimized noise-reduction method was developed with significantly increased temporal smoothing of the signal-to-noise ratio estimate and a more aggressive gain function compared to current noise-reduction methods. This optimized noise-reduction algorithm was tested with 12 cochlear implant recipients over four test sessions. Speech perception was assessed through speech in noise tests with three noise types; speech-weighted noise, 20-talker babble and 4-talker babble. A significant speech perception improvement using optimized noise reduction over standard processing was found in babble noise and speech-weighted noise and over a current noise-reduction method in speech-weighted noise. Speech perception in quiet was not degraded. Listening quality testing for noise annoyance and overall preference found significant improvements over the standard processing and over a current noise-reduction method in speech-weighted and babble noise types. This optimized method has shown significant speech perception and quality improvements compared to the standard processing and a current noise-reduction method.

  7. Airframe noise prediction evaluation

    NASA Technical Reports Server (NTRS)

    Yamamoto, Kingo J.; Donelson, Michael J.; Huang, Shumei C.; Joshi, Mahendra C.

    1995-01-01

    The objective of this study is to evaluate the accuracy and adequacy of current airframe noise prediction methods using available airframe noise measurements from tests of a narrow body transport (DC-9) and a wide body transport (DC-10) in addition to scale model test data. General features of the airframe noise from these aircraft and models are outlined. The results of the assessment of two airframe prediction methods, Fink's and Munson's methods, against flight test data of these aircraft and scale model wind tunnel test data are presented. These methods were extensively evaluated against measured data from several configurations including clean, slat deployed, landing gear-deployed, flap deployed, and landing configurations of both DC-9 and DC-10. They were also assessed against a limited number of configurations of scale models. The evaluation was conducted in terms of overall sound pressure level (OASPL), tone corrected perceived noise level (PNLT), and one-third-octave band sound pressure level (SPL).

  8. Noise and Hearing Protection

    MedlinePlus

    ... most pharmacies. Will I hear other people and machine problems if I wear hearing protectors? Just as ... hear the noises that signify an improperly functioning machine. However, most workers readily adjust to the quieter ...

  9. Noise Abatement Materials

    NASA Technical Reports Server (NTRS)

    1986-01-01

    A former NASA employee who discovered a kind of plastic that soaked up energy, dampened vibrations, and was a good noise abatement material, founded a company to market noise deadening adhesives, sheets, panels and enclosures. Known as SMART products, they are 75-80% lighter than ordinary soundproofing material and have demonstrated a high degree of effectiveness. The company, Varian Associates, makes enclosures for high voltage terminals and other electronic system components, and easily transportable audiometric test booths.

  10. JPL noise control program

    NASA Technical Reports Server (NTRS)

    Klascius, A. F.

    1975-01-01

    Exposures of personnel to noise pollution at the Jet Propulsion Laboratories, Pasadena, California, were investigated. As a result of the study several protective measures were taken: (1) employees exposed to noise hazards were required to wear ear-protection devices, (2) mufflers and air diversion devices were installed around the wind tunnels; and (3) all personnel that are required to wear ear protection are given annual audimeter tests.

  11. Nocturnal aircraft noise effects.

    PubMed

    Basner, M; Samel, A

    2004-01-01

    Noise protection associated with the construction and extension of airports in the Federal Republic of Germany has been regulated by the law for protection against aircraft noise since 1971. This legislation is due for revision because of different aspects. One aspect is the growth of air traffic which has led many airports to the limits of their capacity and in search of new ways of adaptation to the increasing demand for flight services. Another aspect is the increasing concern of the population about noise effects which has to be addressed by better protection against the effects of aircraft noise. The framework conditions of policy in terms of society as a whole, its health and economic environment need to be put into effect by political action. Science can contribute to this goal by performing noise effects research and by providing recommendations to the political body. However, it remains controversial, what measures are necessary or adequate to assure effective protection of the population against aircraft noise. This is particularly true for the protection of rest and sleep at night. The problem of finding a common basis for adequate recommendations is associated with (1) the low number of primary studies, which also exhibited highly variable results and assessments, (2) the handling of acoustic or psycho-acoustic dimensions for quantifying psychological or physiological reactions, and (3) the conception of how far preventive measures have to go to prove effective. With this in mind, the DLR Institute for Aerospace Medicine is conducting a large-scale, multi-stage study for investigating the acute effects of nocturnal aircraft noise on human sleep. This enterprise is implemented in the framework of the HGF/DLR project "Quiet Air Traffic" for developing sustainable assessment criteria for human-specific effects of aircraft noise at night.

  12. NASA Jet Noise Research

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda

    2012-01-01

    The presentation highlights jet-noise research conducted in the Subsonic Fixed Wing, Supersonics, and Environmentally Responsible Aviation Projects in the Fundamental Aeronautics Program at NASA. The research efforts discussed include NASA's updated Aircraft NOise Prediction Program (ANOPP2), acoustic-analogy-based prediction tools, jet-surface-interaction studies, plasma-actuator investigations, N+2 Supersonics Validation studies, rectangular-jet experiments, twin-jet experiments, and Hybrid Wind Body (HWB) activities.

  13. Combustion Noise Investigation

    DTIC Science & Technology

    1977-02-01

    from aircraft engines arm de- velc. ped and experimentally evaluated by conducting rig experiments and by comparing with data from se’.,_ full scale ...engines. Comparison of predictions with full scale engine data indicate that direct combus- tior noise is the dominant source for the P&WA engines...investigated. The dlirect combustion noise prediction system includes expressions for acoustic pow.,r level, peak frequency and full- scale engine acoustic

  14. Television noise reduction device

    NASA Technical Reports Server (NTRS)

    Gordon, B. L.; Stamps, J. C. (Inventor)

    1975-01-01

    A noise reduction system that divides the color video signal into its luminance and chrominance components is reported. The luminance component of a given frame is summed with the luminance component of at least one preceding frame which was stored on a disc recorder. The summation is carried out so as to achieve a signal amplitude equivalent to that of the original signal. The averaged luminance signal is then recombined with the chrominance signal to achieve a noise-reduced television signal.

  15. Aircraft noise - Different ways to monitor the noise load

    NASA Astrophysics Data System (ADS)

    Bekebrede, G.

    Measures taken by the Dutch government to reduce aircraft-noise disturbances including the establishment of noise zones in which subsequent building is forbidden, while already existing homes are provided with noise insulation are discussed. To ensure accurate noise monitoring, the following recommendations were made by the NLR: (1) regular noise load calculations, utilizing aircraft noise and performance data, the air traffic mix, and flight route information; (2) flight track monitoring, performed by a computerized Flight Track and Aircraft Noise Monitoring System which identifies all aircraft deviating from the prescribed track (i.e., flying over congested regions); and (3) actual noise monitoring, to guard the noise level at a specific noise-sensitive area in close proximity to the airfield, such as a hospital.

  16. Environmental issues: noise, rail noise, and high-speed rail

    SciTech Connect

    Hall, F.L.; Welland, J.D.; Bragdon, C.R.; Houtman, J.W.; Immers, B.H.

    1987-01-01

    The six papers in the report deal with the following areas: the effect of noise barriers on the market value of adjacent residential properties; control of airport- and aircraft-related noise in the United States; a traffic-assignment model to reduce noise annoyance in urban networks; a survey of railroad occupational noise sources; a prediction procedure for rail transportation ground-borne noise and vibration; and high-speed rail in California: the dream, the process, and the reality.

  17. 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

  18. 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.

  19. Stable low noise voltage source

    NASA Technical Reports Server (NTRS)

    Lutes, G. F.

    1978-01-01

    Hum and noise on power sources can have a significant effect on system noise. Filtering to achieve low hum and noise is accomplished at low current levels. The diode regulator circuit is described which is ideal for this type of filtering. Hum and noise rejection is achieved with good output voltage stability in a small, low-cost, reliable circuit.

  20. Making noise comfortable for people

    SciTech Connect

    Leventhall, H.G.; Wise, S.S.

    1998-10-01

    Typical HVAC noise may produce an uncomfortable environment, leading to the associated problems of general dissatisfaction and reduced productivity. It is not sufficient to have good thermal, lighting, and air cleanliness conditions if the noise is disturbing. In this paper, noise comfort is considered, with special emphasis on the developing criteria for low-frequency noise.

  1. 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.

  2. 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.

  3. Train noise reduction scenarios for compliance with future noise legislation

    NASA Astrophysics Data System (ADS)

    Leth, S.

    2003-10-01

    The Technical Specification for Interoperability (TSI) for high-speed trains on the European market includes limits on noise emission. These and other future restrictions on exterior noise of high-speed and intercity trains will require that train manufacturers implement noise control measures early in the design phase. A fundamental problem faced by manufacturers during the design process is determining how much noise reduction is required for each of the various noise sources on the train in order to achieve an optimal balance. To illustrate this process, estimates are presented of the contributions from different sources on existing Bombardier trains, based on measured data, numerical calculations and empirical formulae. In addition, methods of achieving the required noise reductions for different sources are briefly discussed along with targets for future exterior noise emission. Measurement results presented demonstrate the importance of track quality in noise emission. Noise restrictions, including future legislation, must give proper recognition to this important parameter.

  4. 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.

  5. Aircraft turbofan noise

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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 techniques 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. Areas requiring further research are discussed, and the relevance of aircraft turbofan results to quieting other turbomachinery installation is addressed.

  6. Road Traffic Noise

    NASA Astrophysics Data System (ADS)

    Beckenbauer, Thomas

    Road traffic is the most interfering noise source in developed countries. According to a publication of the European Union (EU) at the end of the twentieth century [1], about 40% of the population in 15 EU member states is exposed to road traffic noise at mean levels exceeding 55 dB(A). Nearly 80 million people, 20% of the population, are exposed to levels exceeding 65 dB(A) during daytime and more than 30% of the population is exposed to levels exceeding 55 dB(A) during night time. Such high noise levels cause health risks and social disorders (aggressiveness, protest, and helplessness), interference of communication and disturbance of sleep; the long- and short-term consequences cause adverse cardiovascular effects, detrimental hormonal responses (stress hormones), and possible disturbance of the human metabolism (nutrition) and the immune system. Even performance at work and school could be impaired.

  7. Video noise reduction

    NASA Astrophysics Data System (ADS)

    Drewery, J. O.; Storey, R.; Tanton, N. E.

    1984-07-01

    A video noise and film grain reducer is described which is based on a first-order recursive temporal filter. Filtering of moving detail is avoided by inhibiting recursion in response to the amount of motion in a picture. Motion detection is based on the point-by-point power of the picture difference signal coupled with a knowledge of the noise statistics. A control system measures the noise power and adjusts the working point of the motion detector accordingly. A field trial of a manual version of the equipment at Television Center indicated that a worthwhile improvement in the quality of noisy or grainy pictures received by the viewer could be obtained. Subsequent trials of the automated version confirmed that the improvement could be maintained. Commercial equipment based on the design is being manufactured and marketed by Pye T.V.T. under license. It is in regular use on both the BBC1 and BBC2 networks.

  8. Ancient noise generators

    NASA Astrophysics Data System (ADS)

    Beristain, Sergio; Menchaca, Rolando; Velazquez, Roberto

    2002-11-01

    There has been found a whole family of similar artifacts which produce singing noises. These noises sometimes resemble those sounds generated by some animals and/or naturally produced by strong winds passing through holes and edges. It means that these sounds have wide frequency spectrums and very often some clear tones are identified. The original purpose of these artifacts is unknown, but some researchers think that some were used in mortuary ceremonies and employed by H-men. The Olmecan whistle previously presented belongs to this family, and now it is compared with a bone or wooden instrument shown in the Florentine codex.

  9. Rocket Noise Prediction Program

    NASA Technical Reports Server (NTRS)

    Margasahayam, Ravi; Caimi, Raoul

    1999-01-01

    A comprehensive, automated, and user-friendly software program was developed to predict the noise and ignition over-pressure environment generated during the launch of a rocket. The software allows for interactive modification of various parameters affecting the generated noise environment. Predictions can be made for different launch scenarios and a variety of vehicle and launch mount configurations. Moreover, predictions can be made for both near-field and far-field locations on the ground and any position on the vehicle. Multiple engine and fuel combinations can be addressed, and duct geometry can be incorporated efficiently. Applications in structural design are addressed.

  10. Community response to noise.

    PubMed

    Yano, Takashi; Gjestland, Truls; Lee, Soogab

    2012-01-01

    Activities from 2008 to 2011 by ICBEN community response to noise team were summarized. That is, individual community-based indexes such as community tolerance Level, Zuricher Fluglarm Index (ZFI) and Frankfurter Fluglarm Index (FFI/FNI) were newly proposed, differences in railway bonus between Europe and Asia were discussed by a Swedish survey, socio-acoustic surveys were reported from developing countries, and annoyance equivalents and dominant source models were proposed as the adequate combined noise model. Furthermore, not only negative, but also positive aspects of sound were discussed as soundscape studies. Finally, seven items were listed as future team activities.

  11. Psychoacoustic study on contribution of fan noise to engine noise

    NASA Astrophysics Data System (ADS)

    Zhang, Junhong; Liu, Hai; Bi, Fengrong; Ni, Guangjian; Zhang, Guichang; Lin, Jiewei; Yu, Hanzhengnan

    2012-07-01

    There are more researches on engine fan noise control focusing on reducing fan noise level through optimizing fan structure, and a lot of research achievements have been obtained. However, researches on the effect of fan noise to engine noise quality are lacking. The influences of the effects of fan structure optimization on the engine noise quality are unclear. Thus, there will be a decline in fan noise level, but the deterioration of engine noise quality. Aiming at the above problems, in consideration of fan structure design and engine noise quality, an innovative method to analyze the contribution of fan noise to engine noise quality using psychoacoustic theory is proposed. The noises of diesel engine installing different cooling fans are measured by using the acoustic pressure method. The experiment results are regarded as analysis samples. The model of sensory pleasantness is used to analyze the sound quality of a diesel engine with different cooling fans. Results show that after installing 10-blade fan in medium diameter the sensory pleasantness at each test point is increased, and the increase is 13.53% on average, which indicate the improvement of the engine noise quality. In order to verify the psychoacoustical analysis, the subjective assessment is carried out. The test result shows the noise quality of engine installed 10-blade fan in medium diameter is most superior. 1/3 octave frequency spectrum analysis is used to study the reason of the improvement of engine noise quality. It is found that after installing proper cooling fan the sound pressure level below 400 Hz are obviously increased, the frequency assignment and spectral envelope are more reasonable and a proper cooling fan can optimize the spectrum structure of the engine noise. The psychoacoustic study is applied in the contribution of fan noise to engine noise, and the idea of engine sound quality improvement through the structure optimization is proposed.

  12. Helicopter tail rotor noise

    NASA Technical Reports Server (NTRS)

    Chou, S.-T.; George, A. R.

    1986-01-01

    A study was made of helicopter tail rotor noise, particularly that due to interactions with the main rotor tip vortices, and with the fuselage separation mean wake. The tail rotor blade-main rotor tip vortex interaction is modelled as an airfoil of infinite span cutting through a moving vortex. The vortex and the geometry information required by the analyses are obtained through a free wake geometry analysis of the main rotor. The acoustic pressure-time histories for the tail rotor blade-vortex interactions are then calculated. These acoustic results are compared to tail rotor loading and thickness noise, and are found to be significant to the overall tail rotor noise generation. Under most helicopter operating conditions, large acoustic pressure fluctuations can be generated due to a series of skewed main rotor tip vortices passing through the tail rotor disk. The noise generation depends strongly upon the helicopter operating conditions and the location of the tail rotor relative to the main rotor.

  13. Community noise monitoring program

    Treesearch

    Arnold G. Konheim

    1977-01-01

    There are numerous questions in regard to methods, instrumentation, and human and agency resources for community noise monitoring. The U. S. Environmental Protection Agency is currently in the process of seeking answers to these questions through research within the agency and by cooperation with other organizations, including the Department of Defense and the National...

  14. Exploring Noise: Sound Pollution.

    ERIC Educational Resources Information Center

    Rillo, Thomas J.

    1979-01-01

    Part one of a three-part series about noise pollution and its effects on humans. This section presents the background information for teachers who are preparing a unit on sound. The next issues will offer learning activities for measuring the effects of sound and some references. (SA)

  15. JET Noise Prediction

    NASA Technical Reports Server (NTRS)

    Goldstein, M. E.; Leib, S. J.

    2007-01-01

    Aerodynamic noise prediction has been an important and challenging research area since James Lighthill first introduced his Acoustic Analogy Approach over fifty years ago. This talk attempts to provide a unified framework for the subsequent theoretical developments in this field. It assumes that there is no single approach that is optimal in all situations and uses the framework as a basis for discussing the strengths weaknesses of the various approaches to this topic. But the emphasis here will be on the important problem of predicting the noise from high speed air jets. Specific results will presented for round jets in the 0.5 to 1.4 Mach number range and compared with experimental data taken on the Glenn SHAR rig. It is demonstrated that non-parallel mean flow effects play an important role in predicting the noise at the supersonic Mach numbers. The results explain the failure of previous attempts based on the parallel flow Lilley model (which has served as the foundation for most jet noise analyses during past two decades).

  16. Noise: A Health Problem.

    ERIC Educational Resources Information Center

    Environmental Protection Agency, Washington, DC. Office of Noise Abatement and Control.

    This booklet contains nine sections describing ways in which noise may endanger health and well-being. Secions are included on: (1) hearing loss; (2) heart disease; (3) other reactions by the body; (4) effects on the unborn; (5) special effects on children; (6) intrusion at home and work; (7) sleep disruption; (8) mental and social well-being; and…

  17. Noise Assessment Guidelines.

    ERIC Educational Resources Information Center

    Schultz, Theodore J.; McMahon, Nancy M.

    The Department of Housing and Urban Development (HUD), in its efforts to provide decent housing and a suitable living environment, is concerned with noise as a major source of environmental pollution. To this end, these guidelines are presented to provide site screening techniques. The procedures described have been developed so that people…

  18. Curing the noise epidemic

    NASA Astrophysics Data System (ADS)

    Mazer, Susan

    2005-09-01

    The argument is made that design does not stop when the fixed architectural and acoustical components are in place. Spaces live and breathe with the people who reside in them. Research and examples are presented that show that noise, auditory clutter, thrives on itself in hospitals. Application of the Lombard reflex studies fit into the hospital setting, but do not offer solutions as to how one might reduce the impact. In addition, the basis for looking at the noise component as a physical as well cultural dynamic will be addressed. Whether the result of the wrong conversation in the wrong place or the right conversation in an unfortunate place, talk mixed with sounds of technology is shown to cause its own symptoms. From heightened anxiety and stress to medical errors, staff burnout, or HIPAA violations, the case is made that noise is pandemic in hospitals and demands financial and operational investment. An explanation of how to reduce noise by design of the dynamic environment - equipment, technology, staff protocols is also provided.

  19. Jet Engine Noise Reduction

    DTIC Science & Technology

    2009-04-01

    factors include: – Maceration of the thin skin of the ear canal leading to pain/and or infection. – Ear canal infection (external otitis ...145 – 150 dB) around jet aircraft. The magnitude and impact of noise transmitted via bone and other media such as fluid is largely unknown. The ear

  20. Jet Screech Noise Computation

    NASA Technical Reports Server (NTRS)

    Loh, Ching Y.; Hultgren, Lennart S.

    2003-01-01

    The near-field screech-tone noise of a typical underexpanded circular jet issuing from a sonic nozzle is simulated numerically. The self-sustained feedback loop is automatically established in the simulation. The computed shock-cell structure, acoustic wave length, screech tone frequencies, and sound pressure levels in the near field are in good agreement with existing experimental results.

  1. Noise Control through Education.

    ERIC Educational Resources Information Center

    Pennino, Martha

    1979-01-01

    Discussed are the public education and information programs on noise pollution control currently in operation within the Metropolitan Washington, D.C. area that have been either developed or implemented under the auspices of the Metropolitan Washington Council of Governments. (BT)

  2. Playback Experiments for Noise Exposure.

    PubMed

    Holles, Sophie; Simpson, Stephen D; Lecchini, David; Radford, Andrew N

    2016-01-01

    Playbacks are a useful tool for conducting well-controlled and replicated experiments on the effects of anthropogenic noise, particularly for repeated exposures. However, playbacks are unlikely to fully reproduce original sources of anthropogenic noise. Here we examined the sound pressure and particle acceleration of boat noise playbacks in a field experiment and reveal that although there remain recognized limitations, the signal-to-noise ratios of boat playbacks to ambient noise do not exceed those of a real boat. The experimental setup tested is therefore of value for use in experiments on the effects of repeated exposure of aquatic animals to boat noise.

  3. Microwatt shot-noise measurement

    NASA Astrophysics Data System (ADS)

    Bacon, A. M.; Zhao, H. Z.; Wang, L. J.; Thomas, J. E.

    1995-08-01

    We report a simple scheme for sensitive measurements of optical-noise spectra. Optical noise is separated from electronic noise when the output of an analog spectrum analyzer is real-time squared and then lock-in detected. This method directly yields the desired mean-square noise voltage, i.e., the power spectrum of the optical noise on a linear scale. To demonstrate this technique, the mean-square shot noise of a laser beam is measured and found to vary linearly with the laser power from several milliwatts down to one microwatt, in excellent quantitative agreement with predictions.

  4. Tandem Cylinder Noise Predictions

    NASA Technical Reports Server (NTRS)

    Lockhard, David P.; Khorrami, Mehdi R.; CHoudhari, Meelan M.; Hutcheson, Florence V.; Brooks, Thomas F.; Stead, Daniel J.

    2007-01-01

    In an effort to better understand landing-gear noise sources, we have been examining a simplified configuration that still maintains some of the salient features of landing-gear flow fields. In particular, tandem cylinders have been studied because they model a variety of component level interactions. The present effort is directed at the case of two identical cylinders spatially separated in the streamwise direction by 3.7 diameters. Experimental measurements from the Basic Aerodynamic Research Tunnel (BART) and Quiet Flow Facility (QFF) at NASA Langley Research Center (LaRC) have provided steady surface pressures, detailed off-surface measurements of the flow field using Particle Image Velocimetry (PIV), hot-wire measurements in the wake of the rear cylinder, unsteady surface pressure data, and the radiated noise. The experiments were conducted at a Reynolds number of 166 105 based on the cylinder diameter. A trip was used on the upstream cylinder to insure a fully turbulent shedding process and simulate the effects of a high Reynolds number flow. The parallel computational effort uses the three-dimensional Navier-Stokes solver CFL3D with a hybrid, zonal turbulence model that turns off the turbulence production term everywhere except in a narrow ring surrounding solid surfaces. The current calculations further explore the influence of the grid resolution and spanwise extent on the flow and associated radiated noise. Extensive comparisons with the experimental data are used to assess the ability of the computations to simulate the details of the flow. The results show that the pressure fluctuations on the upstream cylinder, caused by vortex shedding, are smaller than those generated on the downstream cylinder by wake interaction. Consequently, the downstream cylinder dominates the noise radiation, producing an overall directivity pattern that is similar to that of an isolated cylinder. Only calculations based on the full length of the model span were able to

  5. Reduction of turbomachinery noise

    NASA Technical Reports Server (NTRS)

    Waitz, Ian A. (Inventor); Brookfield, John M. (Inventor); Sell, Julian (Inventor); Hayden, Belva J. (Inventor); Ingard, K. Uno (Inventor)

    1999-01-01

    In the invention, propagating broad band and tonal acoustic components of noise characteristic of interaction of a turbomachine blade wake, produced by a turbomachine blade as the blade rotates, with a turbomachine component downstream of the rotating blade, are reduced. This is accomplished by injection of fluid into the blade wake through a port in the rotor blade. The mass flow rate of the fluid injected into the blade wake is selected to reduce the momentum deficit of the wake to correspondingly increase the time-mean velocity of the wake and decrease the turbulent velocity fluctuations of the wake. With this fluid injection, reduction of both propagating broad band and tonal acoustic components of noise produced by interaction of the blade wake with a turbomachine component downstream of the rotating blade is achieved. In a further noise reduction technique, boundary layer fluid is suctioned into the turbomachine blade through a suction port on the side of the blade that is characterized as the relatively low-pressure blade side. As with the fluid injection technique, the mass flow rate of the fluid suctioned into the blade is here selected to reduce the momentum deficit of the wake to correspondingly increase the time-mean velocity of the wake and decrease the turbulent velocity fluctuations of the wake; reduction of both propagating broad band and tonal acoustic components of noise produced by interaction of the blade wake with a turbomachine component downstream of the rotating blade is achieved with this suction technique. Blowing and suction techniques are also provided in the invention for reducing noise associated with the wake produced by fluid flow around a stationary blade upstream of a rotating turbomachine.

  6. 23 CFR 772.3 - Noise standards.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... OF HIGHWAY TRAFFIC NOISE AND CONSTRUCTION NOISE § 772.3 Noise standards. The highway traffic noise prediction requirements, noise analyses, noise abatement criteria, and requirements for informing local... 23 Highways 1 2011-04-01 2011-04-01 false Noise standards. 772.3 Section 772.3 Highways FEDERAL...

  7. 23 CFR 772.3 - Noise standards.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... OF HIGHWAY TRAFFIC NOISE AND CONSTRUCTION NOISE § 772.3 Noise standards. The highway traffic noise prediction requirements, noise analyses, noise abatement criteria, and requirements for informing local... 23 Highways 1 2010-04-01 2010-04-01 false Noise standards. 772.3 Section 772.3 Highways FEDERAL...

  8. 23 CFR 772.3 - Noise standards.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 23 Highways 1 2014-04-01 2014-04-01 false Noise standards. 772.3 Section 772.3 Highways FEDERAL... OF HIGHWAY TRAFFIC NOISE AND CONSTRUCTION NOISE § 772.3 Noise standards. The highway traffic noise prediction requirements, noise analyses, noise abatement criteria, and requirements for informing local...

  9. 23 CFR 772.3 - Noise standards.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 23 Highways 1 2013-04-01 2013-04-01 false Noise standards. 772.3 Section 772.3 Highways FEDERAL... OF HIGHWAY TRAFFIC NOISE AND CONSTRUCTION NOISE § 772.3 Noise standards. The highway traffic noise prediction requirements, noise analyses, noise abatement criteria, and requirements for informing local...

  10. 23 CFR 772.3 - Noise standards.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 23 Highways 1 2012-04-01 2012-04-01 false Noise standards. 772.3 Section 772.3 Highways FEDERAL... OF HIGHWAY TRAFFIC NOISE AND CONSTRUCTION NOISE § 772.3 Noise standards. The highway traffic noise prediction requirements, noise analyses, noise abatement criteria, and requirements for informing local...

  11. The Traffic Noise Index: A Method of Controlling Noise Nuisance.

    ERIC Educational Resources Information Center

    Langdon, F. J.; Scholes, W. E.

    This building research survey is an analysis of the social nuisance caused by urban motor ways and their noise. The Traffic Noise Index is used to indicate traffic noises and their effects on architectural designs and planning, while suggesting the need for more and better window insulation and acoustical barriers. Overall concern is for--(1)…

  12. 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.

  13. Jet Noise Reduction

    NASA Technical Reports Server (NTRS)

    Kenny, Patrick

    2004-01-01

    The Acoustics Branch is responsible for reducing noise levels for jet and fan components on aircraft engines. To do this, data must be measured and calibrated accurately to ensure validity of test results. This noise reduction is accomplished by modifications to hardware such as jet nozzles, and by the use of other experimental hardware such as fluidic chevrons, elliptic cores, and fluidic shields. To insure validity of data calibration, a variety of software is used. This software adjusts the sound amplitude and frequency to be consistent with data taken on another day. Both the software and the hardware help make noise reduction possible. work properly. These software programs were designed to make corrections for atmosphere, shear, attenuation, electronic, and background noise. All data can be converted to a one-foot lossless condition, using the proper software corrections, making a reading independent of weather and distance. Also, data can be transformed from model scale to full scale for noise predictions of a real flight. Other programs included calculations of Over All Sound Pressure Level (OASPL), Effective Perceived Noise Level (EPNL). OASPL is the integration of sound with respect to frequency, and EPNL is weighted for a human s response to different sound frequencies and integrated with respect to time. With the proper software correction, data taken in the NATR are useful in determining ways to reduce noise. display any difference between two or more data files. Using this program and graphs of the data, the actual and predicted data can be compared. This software was tested on data collected at the Aero Acoustic Propulsion Laboratory (AAPL) using a variety of window types and overlaps. Similarly, short scripts were written to test each individual program in the software suite for verification. Each graph displays both the original points and the adjusted points connected with lines. During this summer, data points were taken during a live experiment

  14. Advanced Noise Control Fan (ANCF)

    NASA Image and Video Library

    2014-01-15

    The Advanced Noise Control Fan shown here is located in NASA Glenn’s Aero-Acoustic Propulsion Laboratory. The 4-foot diameter fan is used to evaluate innovate aircraft engine noise reduction concepts less expensively and more quickly.

  15. High noise immunity one shot

    NASA Technical Reports Server (NTRS)

    Schaffer, G. L.

    1972-01-01

    Multivibrator circuit, which includes constant current source, isolates line noise from timing circuitry and field effect transistor controls circuit's operational modes. Circuit has high immunity to supply line noise.

  16. Spectral Characteristics of Pitot Noise

    NASA Astrophysics Data System (ADS)

    Hornung, H. G.; Parziale, N. J.

    For experimental studies of transition from laminar to turbulent boundary layer flow it is important to know the ambient noise spectrum in the facility. In supersonic wind tunnels this is often assessed by measuring pitot pressure noise.

  17. Noise in the nervous system.

    PubMed

    Faisal, A Aldo; Selen, Luc P J; Wolpert, Daniel M

    2008-04-01

    Noise--random disturbances of signals--poses a fundamental problem for information processing and affects all aspects of nervous-system function. However, the nature, amount and impact of noise in the nervous system have only recently been addressed in a quantitative manner. Experimental and computational methods have shown that multiple noise sources contribute to cellular and behavioural trial-to-trial variability. We review the sources of noise in the nervous system, from the molecular to the behavioural level, and show how noise contributes to trial-to-trial variability. We highlight how noise affects neuronal networks and the principles the nervous system applies to counter detrimental effects of noise, and briefly discuss noise's potential benefits.

  18. Automatic noise limiter-blanker

    NASA Technical Reports Server (NTRS)

    Burhans, R. W.

    1976-01-01

    A blanker system that may be used with audio noise limiters or automatic noise limiters was described. The system employs a pair of silicon diodes and two RC filters connected across the feedback impedance of an operational amplifier so as to counteract impulse noise interference caused by local spherics activity or 60 Hz harmonics radiated from ac motor control systems. The following information is given: circuit diagram and description, operating details, evaluation, discussion of other noise blanking methods.

  19. Quantum model of spin noise.

    PubMed

    Annabestani, R; Cory, D G; Emerson, J

    2015-03-01

    Any ensemble of quantum particles exhibits statistical fluctuations known as spin noise. Here, we provide a description of spin noise in the language of open quantum systems. The description unifies the signatures of spin noise under both strong and weak measurements. Further, the model accounts for arbitrary spin dynamics from an arbitrary initial state. In all cases we can find both the spin noise and its time correlation function.

  20. Reference noise method of removing powerline noise from recorded signals.

    PubMed

    Jiruska, Premysl; Cmejla, Roman; Powell, Andrew D; Chang, Wei-Chih; Vreugdenhil, Martin; Jefferys, John G R

    2009-10-30

    Powerline contamination of recorded signals represents a major source of noise in electrophysiology and impairs the use of recordings for research. In this article we present simple and effective method for cancelling 50 Hz (or 60 Hz) noise using a reference noise signal and average noise cycle subtraction. This method is capable of reliably removing not only the fundamental powerline frequency but also its harmonic frequencies. The efficiency of this method appears to be superior to other commonly used methods such as notch filtering or adaptive filtering. Our experience and results show that this method can be efficiently used with very low signal-to-noise ratios, while preserving original signal waveform.

  1. 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.

  2. The Signal Importance of Noise

    ERIC Educational Resources Information Center

    Macy, Michael; Tsvetkova, Milena

    2015-01-01

    Noise is widely regarded as a residual category--the unexplained variance in a linear model or the random disturbance of a predictable pattern. Accordingly, formal models often impose the simplifying assumption that the world is noise-free and social dynamics are deterministic. Where noise is assigned causal importance, it is often assumed to be a…

  3. Aircraft Noise Reduction Subproject Overview

    NASA Technical Reports Server (NTRS)

    Fernandez, Hamilton; Nark, Douglas M.; Van Zante, Dale E.

    2016-01-01

    The material presents highlights of propulsion and airframe noise research being completed for the Advanced Air Transport Technology Project. The basis of noise reduction plans along with representative work for the airframe, propulsion, and propulsion-airframe integration is discussed for the Aircraft Noise reduction Subproject.

  4. Sounds Alive: A Noise Workbook.

    ERIC Educational Resources Information Center

    Dickman, Donna McCord

    Sarah Screech, Danny Decibel, Sweetie Sound and Neil Noisy describe their experiences in the world of sound and noise to elementary students. Presented are their reports, games and charts which address sound measurement, the effects of noise on people, methods of noise control, and related areas. The workbook is intended to stimulate students'…

  5. School Noise and Its Control

    ERIC Educational Resources Information Center

    Ikenberrgy, Larry D.

    1974-01-01

    Sources of noises affecting schools and their hindrance of learning are presented. Noise levels for different activities are tabled and possible methods for controlling such noises are suggested. Internal to the school, shop and music levels are the most severe. More care in site selection and design considerations are recommended. (LS)

  6. 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

  7. Underwater Flow Noise

    NASA Astrophysics Data System (ADS)

    Dowling, A. P.

    Lighthill's theory of aerodynamic sound provides an effective way of investigating underwater flow noise. When combined with a model of the coherent vortical structures in a turbulent boundary layer, it predicts the wave-number frequency pressure spectrum on a rigid surface and, in particular, highlights the rôle of surface viscous stresses as a source of low wave-number pressure fluctuations on a plane surface. The inclusion of surface curvature and flexibility enables the theory to be applied to acoustic streamers (sometimes known as towed arrays). The effect of the interior mechanical structure of the streamers on the flow noise is investigated. Simple algebraic forms are derived for the comparative performance of liquid and visco-elastic-filled streamers. The introduction of porous foam into a liquid streamer is found to be a particularly effective way of attenuating low wave-number disturbances, and theoretical predictions are compared with experiment.

  8. Scaling aircraft noise perception.

    NASA Technical Reports Server (NTRS)

    Ollerhead, J. B.

    1973-01-01

    Following a brief review of the background to the study, an extensive experiment is described which was undertaken to assess the practical differences between numerous alternative methods for calculating the perceived levels of individual aircraft flyover wounds. One hundred and twenty recorded sounds, including jets, turboprops, piston aircraft and helicopters were rated by a panel of subjects in a pair 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 over a wider dynamic range (84-115 dB SPL) than had generally been used in previous experiments. Performances of the different scales were examined in detail for different aircraft categories, and the merits of different band level summation procedures, frequency weighting functions, duration and tone corrections were investigated.

  9. Active noise reduction

    NASA Astrophysics Data System (ADS)

    Geyer, Carolyn R.

    Active noise reduction (ANR) techniques are described with reference to their application to crewmembers during aircraft operation to enhance productivity and safety. ANR concepts and theory are explained, and the development of protective ANR systems for direct implementation are described. Sound attenuation testing was conducted to study the feasibility of aircraft-powered ANR systems, and the positive results spurred their development for compatibility with flight helmets. The Helmets Limited ANR system uses a bypass mode at times of limited available power and complements the use of passive sound attenuation. Subjective testing results show that the device is effective, and a planned program of intensive evaluation is discussed. The aircraft that require an ANR system are listed, and key areas of implementation include battery power and the combination of ANR circuitry and helmet oxygen masks. It is suggested that ANR techniques can positively impact the efficiency and performance of crewmembers in high-noise-level aircraft.

  10. Noise in Biology

    PubMed Central

    Tsimring, Lev S.

    2014-01-01

    Noise permeates biology on all levels, from the most basic molecular, sub-cellular processes to the dynamics of tissues, organs, organisms, and populations. The functional roles of noise in biological processes can vary greatly. Along with standard, entropy-increasing effects of producing random mutations, diversifying phenotypes in isogenic populations, limiting information capacity of signaling relays, it occasionally plays more surprising constructive roles by accelerating the pace of evolution, providing selective advantage in dynamic environments, enhancing intracellular transport of biomolecules and increasing information capacity of signaling pathways. This short review covers the recent progress in understanding mechanisms and effects of fluctuations in biological systems of different scales and the basic approaches to their mathematical modeling. PMID:24444693

  11. Strategies for Railway Noise

    NASA Astrophysics Data System (ADS)

    Bovey, E. C.

    1996-05-01

    Strategies are much talked about, but frequently lack any substance. The general concepts of strategic planning are discussed and the need for it to have a focus, i.e., a clear objective, are emphasized. A structural approach to strategic plan development is advocated, with a definition of the relevant issues being a prerequisite for success. Strategies, however, must be flexible and constantly reviewed even though the measures of success are often blurred. Railway noise is clearly amenable to strategic planning, but the issues will vary depending on the objectives of the organization. It is evident that railway noise technology, application and development, while important, needs to be substantially supplemented by other factors such as logistics and management issues to form an effective strategy in this domain.

  12. Fan noise prediction assessment

    NASA Technical Reports Server (NTRS)

    Bent, Paul H.

    1995-01-01

    This report is an evaluation of two techniques for predicting the fan noise radiation from engine nacelles. The first is a relatively computational intensive finite element technique. The code is named ARC, an abbreviation of Acoustic Radiation Code, and was developed by Eversman. This is actually a suite of software that first generates a grid around the nacelle, then solves for the potential flowfield, and finally solves the acoustic radiation problem. The second approach is an analytical technique requiring minimal computational effort. This is termed the cutoff ratio technique and was developed by Rice. Details of the duct geometry, such as the hub-to-tip ratio and Mach number of the flow in the duct, and modal content of the duct noise are required for proper prediction.

  13. Supersonics--Airport Noise

    NASA Technical Reports Server (NTRS)

    Bridges, James

    2007-01-01

    At this, the first year-end meeting of the Fundamental Aeronautics Program, an overview of the Airport Noise discipline of the Supersonics Project leads the presentation of technical plans and achievements in this area of the Project. The overview starts by defining the Technical Challenges targeted by Airport Noise efforts, and the Approaches planned to meet these challenges. These are fleshed out in Elements, namely Prediction, Diagnostics, and Engineering, and broken down into Tasks. The Tasks level is where individual researchers' work is defined and from whence the technical presentations to follow this presentation come. This overview also presents the Milestones accomplished to date and to be completed in the next year. Finally, the NASA Research Announcement cooperative agreement activities are covered and tied to the Tasks and Milestones.

  14. Noise Emission Assessment

    NASA Astrophysics Data System (ADS)

    Hübner, G.; Schorer, E.

    The acoustical efficiency of machines varies in the range of 10-9 to 10-5. This means even high power machines generate sound powers of a few Watts only. Due to the high sensitivity of the human ear however, such low sound powers create close to the machine loudnesses higher than 100 phon (64 sone). Consequently, the assessment of machinery noise emission requires relations to these subjective properties.

  15. Aerodynamic noise sources

    NASA Astrophysics Data System (ADS)

    Munin, A. G.; Kuznetsov, V. M.; Leontev, E. A.

    A general theory is developed for aerodynamic sound generation and its propagation in an inhomogeneous medium. Results of theoretical and experimental studies of the acoustic characteristics of jets are discussed, and a solution is presented to the problem concerning the noise from a section, free rotor, and a rotor located inside a channel. Sound propagation in a channel with flow and selection of soundproofing liners for the channel walls are also discussed.

  16. Optical Johnson noise thermometry

    DOEpatents

    Shepard, Robert L.; Blalock, Theron V.; Roberts, Michael J.; Maxey, Lonnie C.

    1992-01-01

    Method and device for direct, non-contact temperature measure of a body. A laser beam is reflected from the surface of the body and detected along with the Planck radiation. The detected signal is analyzed using signal correlation technique to generate an output signal proportional to the Johnson noise introduced into the reflected laser beam as a direct measure of the absolute temperature of the body.

  17. Cabin acoustical noise

    NASA Astrophysics Data System (ADS)

    Homick, J. L.

    1981-12-01

    Using a hand-held sound pressure level meter the crew made one octave band and A-weight sound level measurements at four locations in the Orbiter on Mission Day 1. The data were voice recorded and transmitted to the ground prior to the first inflight sleep period. The data obtained are summarized. From a physiological point of view the noise levels measured on STS-1 were not hazardous to the crewmens' hearing.

  18. Bloch vector projection noise

    NASA Technical Reports Server (NTRS)

    Wang, Li-Jun; Bacon, A. M.; Zhao, H.-Z.; Thomas, J. E.

    1994-01-01

    In the optical measurement of the Bloch vector components describing a system of N two-level atoms, the quantum fluctuations in these components are coupled into the measuring optical field. This paper develops the quantum theory of optical measurement of Bloch vector projection noise. The preparation and probing of coherence in an effective two-level system consisting of the two ground states in an atomic three-level lambda-scheme are analyzed.

  19. Aviation Noise Effects,

    DTIC Science & Technology

    1985-03-01

    included , ,.,-,;. 17 e18 . Distribution StatementA rcrafe, aviation, noise, annoyance, This document is available to the public helicopter, sleep, speech...measurement of real-ear protection of hearing protectors and physical attenuation of earmuffs. ANSI/ ASTM E336-77 (1977): Standard test method for...measurement of airborne sound insulation in buildings. ANSI/ ASTM E413-73 (1980): Standard classification for sound transmission class. ANSI/SAE ARP1071

  20. Noise and mental performance: personality attributes and noise sensitivity.

    PubMed

    Belojevic, G; Jakovljevic, B; Slepcevic, V

    2003-01-01

    The contradictory and confusing results in noise research on humans may partly be due to individual differences between the subjects participating in different studies. This review is based on a twelve year research on the role of neuroticism, extroversion and subjective noise sensitivity during mental work in noisy environment. Neurotic persons might show enhanced "arousability" i.e. their arousal level increases more in stress. Additional unfavorable factors for neurotics are worrying and anxiety, which might prevent them coping successfully with noise, or some other stressors during mental performance. In numerous experiments introverts have showed higher sensitivity to noise during mental performance compared to extroverts, while extroverts often cope with a boring task even by requesting short periods of noise during performance. Correlation analyses have regularly revealed a highly significant negative relation between extroversion and noise annoyance during mental processing. Numerous studies have shown that people with high noise sensitivity may be prevented from achieving the same work results as other people in noisy environment, thus leading to psychosomatic, neurotic or other difficulties. Positive relation between noise annoyance and subjective noise sensitivity might be very strong. Our results have shown, after matching with the results of other relevant studies, that more stable personality, with extroversive tendencies and with a relatively lower subjective noise sensitivity measured with standard questionnaires, may be expected to better adapt to noise during mental performance, compared to people with opposite personality traits.

  1. Noise Analysis on Graphene Devices via Scanning Noise Microscopy

    NASA Astrophysics Data System (ADS)

    Cho, Duckhyung; Sung, Moon Gyu; Lee, Hyungwoo; Heo, Kwang; Byun, Kyung-Eun; Kim, Taekyeong; Seo, David H.; Seo, Sunae; Hong, Seunghun

    2013-03-01

    Until now, the studies about low-frequency noises in electronic devices have mostly relied on the scaling behaviour analysis of current noise measured from multiple devices with different resistance values. However, the fabrication of such multiple devices for noise analysis is a labor-intensive and time-consuming work. Herein, we developed the scanning noise microscopy (SNM) method for nanoscale noise analysis of electronic devices, which allowed us to measure the scaling behaviour of electrical current noises in a graphene-strip-based device. In this method, a conductive atomic force microscopy probe made a direct contact on the graphene strip channel in the device to measure the noise spectra through it. The SNM method enabled the investigation of the noise scaling behaviour using only a single device. In addition, the nanoscale noise map was obtained, which allowed us to study the effect of structural defects on the noise characteristics of the graphene strip channel. Our method should be a powerful strategy for nanoscale noise analysis and play a significant role in basic research on nanoscale devices.

  2. Physical Mechanisms of Seismometer Site Noise and Self-Noise

    NASA Astrophysics Data System (ADS)

    Bainbridge, G. S.; Parker, T.; Townsend, B.; Upadhyaya, S.

    2016-12-01

    Ideally any seismometer installation should have a noise level corresponding to a predefined specification, to ensure the noise level is below the signals of interest. In practice seismic data may contain unforeseen noise artifacts and may vary widely in quality from one station to another due to particular site conditions, problematic installation methods, or a defective or unsuitable instrument. Also some modes of ground motion can be considered as noise, for example local vibration or tilt motion obscuring teleseismic signals. In this study we present an analysis of the physical phenomena which most commonly cause noise artifacts in broadband seismic data, based on data from controlled laboratory experiments as well as field installations. Each different physical mechanism gives rise to noise with particular distinguishing characteristics which can enable the user to diagnose noise symptoms, trace them to a root cause, take corrective action, and evolve towards best practices for particular environments and use cases.

  3. 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.

  4. Control of jet noise

    NASA Technical Reports Server (NTRS)

    Schreck, Stefan

    1993-01-01

    This reports describes experiments conducted at the High-Speed Jet Facility at the University of Southern California on supersonic jets. The goal of the study was to develop methods for controlling the noise emitted from supersonic jets by passive and/or active means. Work by Seiner et al (1991) indicates that eddy Mach wave radiation is the dominant noise source in a heated high speed jet. Eddy Mach radiation is caused by turbulent eddies traveling at supersonic speed in the shear layer of the jet. The convection velocity of the eddies decays with increasing distance from the nozzle exit due to the mixing of the jet stream with the ambient fluid. Once the convection speed reaches subsonic velocities, eddy Mach wave radiation ceases. To control noise, a rapid decay of the convection velocity is desired. This may be accomplished by enhanced mixing in the jet. In this study, small aspect ratio rectangular jet nozzles were tested. A flapping mode was noticed in the jets. By amplifying screech components of the jets and destabilizing the jet columns with a collar device, the flapping mode was excited. The result was a rapid decay of the jet velocity. A reduction in eddy Mach radiation in rectangular supersonic jets may be achieved with this device.

  5. Noise tolerant spatiotemporal chaos computing.

    PubMed

    Kia, Behnam; Kia, Sarvenaz; Lindner, John F; Sinha, Sudeshna; Ditto, William L

    2014-12-01

    We introduce and design a noise tolerant chaos computing system based on a coupled map lattice (CML) and the noise reduction capabilities inherent in coupled dynamical systems. The resulting spatiotemporal chaos computing system is more robust to noise than a single map chaos computing system. In this CML based approach to computing, under the coupled dynamics, the local noise from different nodes of the lattice diffuses across the lattice, and it attenuates each other's effects, resulting in a system with less noise content and a more robust chaos computing architecture.

  6. Handbook for industrial noise control

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The basic principles of sound, measuring techniques, and instrumentation associated with general purpose noise control are discussed. Means for identifying and characterizing a noise problem so that subsequent work may provide the most efficient and cost effective solution are outlined. A methodology for choosing appropriate noise control materials and the proper implementation of control procedures is detailed. The most significant NASA sponsored contributions to the state of the art development of optimum noise control technologies are described including cases in which aeroacoustics and related research have shed some light on ways of reducing noise generation at its source.

  7. Emerging Community Noise Reduction Approaches

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    2012-01-01

    An overview of the current NASA research portfolio in the area of aircraft noise reduction is presented. The emphasis of the research described herein is on meeting the aggressive near- and mid-term national goals for reducing aircraft noise emissions, which NASA internal studies have shown to be feasible using noise reduction technologies currently being developed in-house or in partnership with NASA s industry and academic partners. While NASA has an active research effort in airframe noise reduction, this overview focuses on propulsion noise reduction only.

  8. Noise tolerant spatiotemporal chaos computing

    SciTech Connect

    Kia, Behnam; Kia, Sarvenaz; Ditto, William L.; Lindner, John F.; Sinha, Sudeshna

    2014-12-01

    We introduce and design a noise tolerant chaos computing system based on a coupled map lattice (CML) and the noise reduction capabilities inherent in coupled dynamical systems. The resulting spatiotemporal chaos computing system is more robust to noise than a single map chaos computing system. In this CML based approach to computing, under the coupled dynamics, the local noise from different nodes of the lattice diffuses across the lattice, and it attenuates each other's effects, resulting in a system with less noise content and a more robust chaos computing architecture.

  9. Fan Noise Reduction: An Overview

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    2001-01-01

    Fan noise reduction technologies developed as part of the engine noise reduction element of the Advanced Subsonic Technology Program are reviewed. Developments in low-noise fan stage design, swept and leaned outlet guide vanes, active noise control, fan flow management, and scarfed inlet are discussed. In each case, a description of the method is presented and, where available, representative results and general conclusions are discussed. The review concludes with a summary of the accomplishments of the AST-sponsored fan noise reduction research and a few thoughts on future work.

  10. Externally blown flap impingement noise.

    NASA Technical Reports Server (NTRS)

    Putnam, T. W.; Lasagna, P. L.

    1972-01-01

    An investigation of externally blown flap impingement noise was conducted using a full-scale turbofan engine and aircraft wing. The noise produced with a daisy nozzle installed on the engine exhaust system was greater than that produced by a conical nozzle at the same thrust. The daisy nozzle caused the jet velocity to decay about 35 percent at the flap. The presence of the wing next to the conical nozzle increased the noise, as did increasing the flap deflection. Compared with the conical nozzle, the daisy nozzle produced slightly less noise at a flap deflection of 60 deg but produced more noise at the lower flap deflections tested.

  11. Handbook for industrial noise control

    NASA Astrophysics Data System (ADS)

    The basic principles of sound, measuring techniques, and instrumentation associated with general purpose noise control are discussed. Means for identifying and characterizing a noise problem so that subsequent work may provide the most efficient and cost effective solution are outlined. A methodology for choosing appropriate noise control materials and the proper implementation of control procedures is detailed. The most significant NASA sponsored contributions to the state of the art development of optimum noise control technologies are described including cases in which aeroacoustics and related research have shed some light on ways of reducing noise generation at its source.

  12. The Airframe Noise Reduction Challenge

    NASA Technical Reports Server (NTRS)

    Lockard, David P.; Lilley, Geoffrey M.

    2004-01-01

    The NASA goal of reducing external aircraft noise by 10 dB in the near-term presents the acoustics community with an enormous challenge. This report identifies technologies with the greatest potential to reduce airframe noise. Acoustic and aerodynamic effects will be discussed, along with the likelihood of industry accepting and implementing the different technologies. We investigate the lower bound, defined as noise generated by an aircraft modified with a virtual retrofit capable of eliminating all noise associated with the high lift system and landing gear. However, the airframe noise of an aircraft in this 'clean' configuration would only be about 8 dB quieter on approach than current civil transports. To achieve the NASA goal of 10 dB noise reduction will require that additional noise sources be addressed. Research shows that energy in the turbulent boundary layer of a wing is scattered as it crosses trailing edge. Noise generated by scattering is the dominant noise mechanism on an aircraft flying in the clean configuration. Eliminating scattering would require changes to much of the aircraft, and practical reduction devices have yet to receive serious attention. Evidence suggests that to meet NASA goals in civil aviation noise reduction, we need to employ emerging technologies and improve landing procedures; modified landing patterns and zoning restrictions could help alleviate aircraft noise in communities close to airports.

  13. Noise policy: Past and present

    NASA Astrophysics Data System (ADS)

    Lang, William W.

    2004-05-01

    Leo Beranek and the firm Bolt Beranek and Newman have played a defining role in the formulation of noise policy in America. The firm that he and Richard Bolt founded in 1948 with fewer than a half-dozen others grew to become the world's largest acoustical consulting firm with more than 2000 employees. Two decades later in 1971, Leo Beranek was a key founder of the Institute of Noise Control Engineering of the U.S.A. The Institute, which inaugurated the INTER-NOISE series of annual noise congresses in 1972 under Beranek's direction, played a major role in the enactment by the Congress of the Noise Control Act of 1972. NCA-72 identified the Environmental Protection Agency as the leading Federal agency with oversight responsibilities responsible for implementing the noise policies defined by the Congress. In 1981, funding for EPA's noise program was withdrawn. Since then, leadership at the Federal level for implementing a coordinated national noise policy has been absent, but a dozen Federal agencies remain active in the noise field. With the exception of aircraft, no product emission regulations on major sources of noise are enforced today. To rectify this situation, Leo Beranek has recently been playing a leadership role in a concerted effort to rejuvenate America's national noise policy.

  14. Noise Emission from Laboratory Air Blowers

    ERIC Educational Resources Information Center

    Rossing, Thomas D.; Windham, Betty

    1978-01-01

    Product noise ratings for a number of laboratory air blowers are reported and several recommendations for reducing laboratory noise from air blowers are given. Relevant noise ratings and methods for measuring noise emission of appliances are discussed. (BB)

  15. Noise Emission from Laboratory Air Blowers

    ERIC Educational Resources Information Center

    Rossing, Thomas D.; Windham, Betty

    1978-01-01

    Product noise ratings for a number of laboratory air blowers are reported and several recommendations for reducing laboratory noise from air blowers are given. Relevant noise ratings and methods for measuring noise emission of appliances are discussed. (BB)

  16. Externally blown flap impingement noise

    NASA Technical Reports Server (NTRS)

    Lasagna, P. L.; Putnam, T. W.

    1972-01-01

    Tests of the noise produced by the impingement of the jet exhaust on the wing and flap for an externally blown flap system were conducted with a CF700 turbofan engine and an F-111B wing panel. The noise produced with a daisy nozzle installed on the engine was greater than that produced by a conical nozzle at the same thrust. The presence of the wing next to the test nozzles increased the noise, as did increasing the flap deflection angle. Compared with the conical nozzle, the daisy nozzle produced slightly less noise at a flap deflection of 60 deg but produced more noise at the lower flap deflections tested. Tests showed that the single-slotted flap deflected 60 deg, produced less noise than the double-slotted flaps. Also, maintaining the maximum distance between the exit nozzle and flap system resulted in a minor reduction in noise.

  17. Non-propulsive aerodynamic noise

    NASA Astrophysics Data System (ADS)

    Willshire, William L., Jr.; Tracy, Maureen B.

    1992-04-01

    In the first part of the paper, the contribution of airframe noise to total aircraft noise on approach is assessed for a large current technology transport and for the same airframe powered with bypass ratio 10 engines with an additional 5 dB noise suppression applied to the fan and turbine noise sources. The airframe noise of the envisioned advanced subsonic transport is 2 EPNdB less than the largest contributor to the total aircraft noise, the fan inlet. The noise impact of the airframe noise, as measured by noise contour area, is 1/4 that of fan noise. Further fan noise reduction efforts should not view airframe noise as an absolute noise floor. In the second part of the paper, the results from one recent cavity noise wind tunnel experiment is reported. A cavity of dimensions 11.25 in. (28.58 cm) long, 2.5 in. (6.35 cm) wide, and variable depth was tested in the Mach number range of .20 through .90. Reynolds number varied from 5 to 100 million per foot (16 to 328 million per meter). The 1/d ratio was varied from 4.4 to 20.0. The model was tested at yaw angles from 0 to 15 degrees. In general, the deeper the cavity, the greater the amplitude of the acoustic tones. Reynolds number appeared to have little effect on acoustic tone amplitudes. Tone amplitude and bandwidth changed with Mach number. The effect of yaw on acoustic tones varied with Reynolds number, Mach number, 1/h, and mode number. At Mach number 0.90, increased yaw shifted the tone frequencies of the higher modal frequencies to lower frequencies. As cavity depth decreased, the effect of yaw decreased.

  18. Technologies for Turbofan Noise Reduction

    NASA Technical Reports Server (NTRS)

    Huff, Dennis

    2005-01-01

    An overview presentation of NASA's engine noise research since 1992 is given for subsonic commercial aircraft applications. Highlights are included from the Advanced Subsonic Technology (AST) Noise Reduction Program and the Quiet Aircraft Technology (QAT) project with emphasis on engine source noise reduction. Noise reduction goals for 10 EPNdB by 207 and 20 EPNdB by 2022 are reviewed. Fan and jet noise technologies are highlighted from the AST program including higher bypass ratio propulsion, scarf inlets, forward-swept fans, swept/leaned stators, chevron nozzles, noise prediction methods, and active noise control for fans. Source diagnostic tests for fans and jets that have been completed over the past few years are presented showing how new flow measurement methods such as Particle Image Velocimetry (PIV) have played a key role in understanding turbulence, the noise generation process, and how to improve noise prediction methods. Tests focused on source decomposition have helped identify which engine components need further noise reduction. The role of Computational AeroAcoustics (CAA) for fan noise prediction is presented. Advanced noise reduction methods such as Hershel-Quincke tubes and trailing edge blowing for fan noise that are currently being pursued n the QAT program are also presented. Highlights are shown form engine validation and flight demonstrations that were done in the late 1990's with Pratt & Whitney on their PW4098 engine and Honeywell on their TFE-731-60 engine. Finally, future propulsion configurations currently being studied that show promise towards meeting NASA's long term goal of 20 dB noise reduction are shown including a Dual Fan Engine concept on a Blended Wing Body aircraft.

  19. Non-propulsive aerodynamic noise

    NASA Technical Reports Server (NTRS)

    Willshire, William L., Jr.; Tracy, Maureen B.

    1992-01-01

    In the first part of the paper, the contribution of airframe noise to total aircraft noise on approach is assessed for a large current technology transport and for the same airframe powered with bypass ratio 10 engines with an additional 5 dB noise suppression applied to the fan and turbine noise sources. The airframe noise of the envisioned advanced subsonic transport is 2 EPNdB less than the largest contributor to the total aircraft noise, the fan inlet. The noise impact of the airframe noise, as measured by noise contour area, is 1/4 that of fan noise. Further fan noise reduction efforts should not view airframe noise as an absolute noise floor. In the second part of the paper, the results from one recent cavity noise wind tunnel experiment is reported. A cavity of dimensions 11.25 in. (28.58 cm) long, 2.5 in. (6.35 cm) wide, and variable depth was tested in the Mach number range of .20 through .90. Reynolds number varied from 5 to 100 million per foot (16 to 328 million per meter). The 1/d ratio was varied from 4.4 to 20.0. The model was tested at yaw angles from 0 to 15 degrees. In general, the deeper the cavity, the greater the amplitude of the acoustic tones. Reynolds number appeared to have little effect on acoustic tone amplitudes. Tone amplitude and bandwidth changed with Mach number. The effect of yaw on acoustic tones varied with Reynolds number, Mach number, 1/h, and mode number. At Mach number 0.90, increased yaw shifted the tone frequencies of the higher modal frequencies to lower frequencies. As cavity depth decreased, the effect of yaw decreased.

  20. Occupational noise in rice mills.

    PubMed

    Prasanna Kumar, G V; Dewangan, K N; Sarkar, Amaresh; Kumari, Amrita; Kar, Banani

    2008-01-01

    A major occupational hazard for the workers in rice mills is the noise during the operation of various machines. A noise survey was conducted in the workrooms of eight renowned rice mills of the north-eastern region of India established during the period between 1980 and 1985. The rice mills were selected on the basis of the outcome of a walk-through noise survey involving several rice mills of the region. A noise survey map of each rice mill was drawn to identify the predominant noise sources and the causes of high noise in the workrooms of the rice mill. The sound-pressure level (SPL) in the workrooms of the rice mill varied from 78 to 92 dBA. The paddy cleaner, rubber roll sheller, compartment separator, rice cleaner, auxiliary sieve shaker and an electric motor without enclosure were found to be the predominant noise sources in the workrooms of the mill. The causes of high noise in the rice mills may be attributed to the use of a long flat belt drive, crank-and-pitman mechanism, absence of an electric motor enclosure, poor machine maintenance and inadequate acoustic design of the workroom of the rice mill. About 26% of the total labourers were found to be exposed to higher levels of noise than 85 dBA. Subjective response indicated that about 26% of the total labourers felt noise interferes in their work and about 49% labourers were of opinion that noise interferes with their conversation. Noise from machines in the rice mills was found to be the major occupational hazard for the rice mill workers. The predominant noise sources need to be identified and the causes of high noise need to be studied to undertake the appropriate measures to reduce the noise level. To identify the predominant noise sources and their distributions in rice mills, to study the causes of high levels of noise in rice mills and to examine the response of the workers towards noise. A noise survey was conducted in eight renowned rice mills of the north-eastern region of India. The mills were

  1. Imaging with ambient noise

    SciTech Connect

    Snieder, Roel; Wapenaar, Kees

    2010-09-15

    Recent developments in seismology, ultrasonics, and underwater acoustics have led to a radical change in the way scientists think about ambient noise--the diffuse waves generated by pressure fluctuations in the atmosphere, the scattering of water waves in the ocean, and any number of other sources that pervade our world. Because diffuse waves consist of the superposition of waves propagating in all directions, they appear to be chaotic and random. That appearance notwithstanding, diffuse waves carry information about the medium through which they propagate.

  2. Calculated wind noise for an infrasonic wind noise enclosure.

    PubMed

    Abbott, JohnPaul; Raspet, Richard

    2015-07-01

    A simple calculation of the wind noise measured at the center of a large porous wind fence enclosure is developed. The calculation provides a good model of the measured wind noise, with a good agreement within ±5 dB, and is derived by combining the wind noise contributions from (a) the turbulence-turbulence and turbulence-shear interactions inside the enclosure, (b) the turbulence interactions on the surface of the enclosure, and (c) the turbulence-shear interactions outside of the enclosure. Each wind noise contribution is calculated from the appropriate measured turbulence spectra, velocity profiles, correlation lengths, and the mean velocity at the center, surface, and outside of the enclosure. The model is verified by comparisons of the measured wind noise to the calculated estimates of the differing noise contributions and their sum.

  3. Occupational noise in printing companies.

    PubMed

    Mihailovic, Aleksandra; Grujic, Selena D; Kiurski, Jelena; Krstic, Jelena; Oros, Ivana; Kovacevic, Ilija

    2011-10-01

    The extent of noise in five printing companies in Novi Sad, Serbia, was determined using TES-1358A Sound Analyzer with RS-232 Interface. The data on equivalent A-level (dBA), as well as, maximum and minimum sound pressure levels were collected. It was found that folders and offset printing units are the predominant noise sources, with the average L (eq) levels of 87.66 and 82.7 dBA, respectively. Forty percent of the machines produced noise levels above the limiting threshold level of 85 dBA, allowed by law. The noise in all printing companies was dominated by higher frequency noise, and the maximum level mostly appeared at 4,000 Hz. For offset printing machines and folders, the means of L (eq) levels exceeded the permissible levels given by NR-80 curve at higher frequencies. There are no published studies of occupational noise and hearing impairment of workers exposed to hazardous noise in printing industry in Serbia. More extensive studies are needed to determine the exact impact of noise on the workers. Technical and organizational measures in order to control noise and prevent noise exposure, and general hearing conservation program to protect workers, should be introduced in printing industry.

  4. Prediction of Externally Blown Flap Noise and Turbomachinery Strut Noise

    NASA Technical Reports Server (NTRS)

    Fink, M. R.

    1975-01-01

    Methods were developed for predicting externally blown flap (EBF) noise and turbomachinery strut noise. Noise radiated by under-the-wing and upper-surface-blowing EBF configurations is calculated as a sum of lift dipole noise, trailing edge noise, and jet quadrupole noise. Resulting predictions of amplitudes and spectra generally were in good agreement with data from small-scale models. These data cover a range of exhaust velocity, flap deflection, exhaust nozzle position, exhaust nozzle shape, and ratio of exhaust nozzle diameter to wing chord. A semi-empirical method for predicting dipole noise radiation from a strut with incident turbulence was in good agreement with data. Leading-edge regions made of perforated plate backed by a bulk acoustic absorber achieved up to 7 db reduction of strut noise caused by incident turbulence at high frequencies. Radial turbulence in a turbofan exit duct was found to have a relatively high level associated with the mean velocity defect in the rotor blade wakes. Use of these turbulence spectra and a dipole noise radiation equation gave general prediction of measured aft-radiated sound power caused by a splitter ring in a full-scale fan exit duct.

  5. Low-noise SQUID

    DOEpatents

    Dantsker, Eugene; Clarke, John

    2000-01-01

    The present invention comprises a high-transition-temperature superconducting device having low-magnitude low-frequency noise-characteristics in magnetic fields comprising superconducting films wherein the films have a width that is less than or equal to a critical width, w.sub.C, which depends on an ambient magnetic field. For operation in the Earth's magnetic field, the critical width is about 6 micrometers (.mu.m). When made with film widths of about 4 .mu.m an inventive high transition-temperature, superconducting quantum interference device (SQUID) excluded magnetic flux vortices up to a threshold ambient magnetic field of about 100 microTesla (.mu.T). SQUIDs were fabricated having several different film strip patterns. When the film strip width was kept at about 4 .mu.m, the SQUIDs exhibited essentially no increase in low-frequency noise, even when cooled in static magnetic fields of magnitude up to 100 .mu.T. Furthermore, the mutual inductance between the inventive devices and a seven-turn spiral coil was at least 85% of that for inductive coupling to a conventional SQUID.

  6. Fan noise research at NASA

    NASA Astrophysics Data System (ADS)

    Groeneweg, John F.

    Results of recent NASA research to reduce aircraft turbofan noise are described. As the bypass ratio of a turbofan engine increases from 5 to as much as 20, the dominant source of engine noise is the fan. A primary mechanism of tone noise generation is the rotor blade wakes interacting with downstream stator vanes. Methods of analyzing rotor-stator tone noise generation are described and sample results are given. The role of an acoustic modal description is emphasized. Wind tunnel tests of model fans and nacelles are described including a novel rotating microphone technique for modal measurement. Sample far field results are given showing the effects of inlet length, and modal measurements are shown which point to a new generation mechanism. Concepts for active fan noise control at the source are addressed. Implications of the research which have general relevance to fan noise generation and control are discussed.

  7. Noise exposure of music teachers.

    PubMed

    Behar, Alberto; MacDonald, Ewen; Lee, Jason; Cui, Jie; Kunov, Hans; Wong, Willy

    2004-04-01

    A noise exposure survey was performed to assess the risk of hearing loss to school music teachers during the course of their activities. Noise exposure of 18 teachers from 15 schools was measured using noise dosimeters. The equivalent continuous noise level (L(eq)) of each teacher was recorded during single activities (classes) as well as for the entire day, and a normalized 8-hour exposure, termed the noise exposure level (L(ex)) was also computed. The measured L(eq) exceeded the 85-dBA limit for 78% of the teachers. L(ex) exceeded 85 dBA for 39% of the teachers. Limited recommendations on how to reduce the noise exposures are provided. The need for a hearing conservation program has also been emphasized.

  8. Fan Noise Research at NASA

    NASA Technical Reports Server (NTRS)

    Groeneweg, John F.

    1994-01-01

    Results of recent NASA research to reduce aircraft turbofan noise are described. As the bypass ratio of a turbofan engine increases from five to as much as 20, the dominant source of engine noise is the fan. A primary mechanism of tone noise generation is the rotor blade wakes interacting with downstream stator vanes. Methods of analyzing rotor stator tone noise generation are described and sample results are given. The role of an acoustic modal description is emphasized. Wind tunnel tests of model fans and nacelles are described including a novel rotating microphone technique for modal measurement. Sample far field results are given showing the effects of inlet length, and modal measurements are shown which point to a new generation mechanism. Concepts for active fan noise control at the source are addressed. Implications of the research which have general relevance to fan noise generation and control are discussed.

  9. Passive Phase Noise Cancellation Scheme

    PubMed Central

    Kenig, Eyal; Cross, M. C.; Lifshitz, Ron; Karabalin, R. B.; Villanueva, L. G.; Matheny, M. H.; Roukes, M. L.

    2013-01-01

    We introduce a new method for reducing phase noise in oscillators, thereby improving their frequency precision. The noise reduction is realized by a passive device consisting of a pair of coupled nonlinear resonating elements that are driven parametrically by the output of a conventional oscillator at a frequency close to the sum of the linear mode frequencies. Above the threshold for parametric instability, the coupled resonators exhibit self-oscillations which arise as a response to the parametric driving, rather than by application of active feedback. We find operating points of the device for which this periodic signal is immune to frequency noise in the driving oscillator, providing a way to clean its phase noise. We present results for the effect of thermal noise to advance a broader understanding of the overall noise sensitivity and the fundamental operating limits. PMID:23004985

  10. Noise in Lead Beta Alumina.

    DTIC Science & Technology

    1987-05-01

    single crystal and ceramic samples. The temperature dependance for diffusion noise (I>O,1OHz) is greater than can be accounted for by Equation (1). This...3.2 3.3 3.4 3.5 3.6 3.7 1000/T IN 1/9 Figure 2. Temperature Dependance of Nyqutst Noise (5kHz) and Diffusion Noise (lOHz) of Single Crystal and

  11. 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.

  12. Noise of sliding rough contact

    NASA Astrophysics Data System (ADS)

    Le Bot, Alain

    2017-01-01

    This article is a discussion about the origin of friction noise produced when rubbing solids having rough surfaces. We show that noise emerges from numerous impacts into the contact between antagonist asperities of surfaces. Prediction of sound sources reduces to a statistical problem of contact mechanics. On the other hand, contact is also responsible of dissipation of vibration. This leads to the paradoxical result that the noise may not be proportional to the number of sources.

  13. Self-Report of Transportation Noise Exposure, Annoyance and Noise Sensitivity in Relation to Noise Map Information

    NASA Astrophysics Data System (ADS)

    HEINONEN-GUZEJEV, M.; VUORINEN, H. S.; KAPRIO, J.; HEIKKILÄ, K.; MUSSALO-RAUHAMAA, H.; KOSKENVUO, M.

    2000-07-01

    Self-report of noise exposure was compared with the information on noise maps while taking into account measures of self-reported annoyance and noise sensitivity. Self-report data were analyzed for 1495 subjects participating in a case-control study of hypertension from the Finnish Twin Cohort who had replied to a questionnaire in 1988. In addition, noise map information was included in analyses of the 218 study subjects living in the Metropolitan Area of Helsinki. The results show that: (1) In the factor analysis based on all subjects self-report of transportation noise exposure formed an own factor independent of the annoyance variables or noise sensitivity. Annoyance items loaded on to two different factors termed nighttime and daytime annoyance. Noise sensitivity did not load to either of the factors of annoyance. For the subsample with noise map information, the results indicated that: (2) Noise sensitivity was independent of noise map information. (3) Subjects with high noise sensitivity reported more transportation noise exposure than subjects with low noise sensitivity and they reported aircraft, railway and road traffic noise exposure outside the environmental noise map areas almost twice as often as non-sensitive subjects. (4) Noise map information and self-report of noise exposure were consistently associated when aircraft noise was considered. Self-report of noise related items may supplement noise map information in noise protection.

  14. Adjusting Phenotypes by Noise Control

    PubMed Central

    Kim, Kyung H.; Sauro, Herbert M.

    2012-01-01

    Genetically identical cells can show phenotypic variability. This is often caused by stochastic events that originate from randomness in biochemical processes involving in gene expression and other extrinsic cellular processes. From an engineering perspective, there have been efforts focused on theory and experiments to control noise levels by perturbing and replacing gene network components. However, systematic methods for noise control are lacking mainly due to the intractable mathematical structure of noise propagation through reaction networks. Here, we provide a numerical analysis method by quantifying the parametric sensitivity of noise characteristics at the level of the linear noise approximation. Our analysis is readily applicable to various types of noise control and to different types of system; for example, we can orthogonally control the mean and noise levels and can control system dynamics such as noisy oscillations. As an illustration we applied our method to HIV and yeast gene expression systems and metabolic networks. The oscillatory signal control was applied to p53 oscillations from DNA damage. Furthermore, we showed that the efficiency of orthogonal control can be enhanced by applying extrinsic noise and feedback. Our noise control analysis can be applied to any stochastic model belonging to continuous time Markovian systems such as biological and chemical reaction systems, and even computer and social networks. We anticipate the proposed analysis to be a useful tool for designing and controlling synthetic gene networks. PMID:22253584

  15. Noise-induced hearing loss

    SciTech Connect

    Catlin, F.I.

    1986-03-01

    Hearing loss affects 30 million people in the United States; of these, 21 million are over the age of 65 years. This disorder may have several causes: heredity, noise, aging, and disease. Hearing loss from noise has been recognized for centuries but was generally ignored until some time after the Industrial Revolution. Hearing loss from occupational exposure to hazardous noise was identified as a compensable disability by the United States courts in 1948 to 1959. Development of noisy jet engines and supersonic aircraft created additional claims for personal and property damage in the 1950s and 1960s. These conditions led to legislation for noise control in the form of the Occupational Safety and Health Act of 1970 and the Noise Control Act of 1972. Protection of the noise-exposed employee was also an objective of the Hearing Conservation Act of 1971. Subsequent studies have confirmed the benefits of periodic hearing tests for workers exposed to hazardous noise and of otologic evaluation as part of the hearing conservation process. Research studies in laboratory animals, using scanning electron microscopical techniques, have demonstrated that damage to the inner ear and organ of hearing can occur even though subjective (conditioned) response to sound stimuli remains unaffected. Some investigators have employed an epidemiologic approach to identify risk factors and to develop profiles to susceptibility to noise-induced hearing loss. The need for joint involvement of workers and employers in the reduction and control of occupational noise hazards is evident. 19 references.

  16. Noise-induced hearing loss.

    PubMed

    Catlin, F I

    1986-03-01

    Hearing loss affects 30 million people in the United States; of these, 21 million are over the age of 65 years. This disorder may have several causes: heredity, noise, aging, and disease. Hearing loss from noise has been recognized for centuries but was generally ignored until some time after the Industrial Revolution. Hearing loss from occupational exposure to hazardous noise was identified as a compensable disability by the United States courts in 1948 to 1959. Development of noisy jet engines and supersonic aircraft created additional claims for personal and property damage in the 1950s and 1960s. These conditions led to legislation for noise control in the form of the Occupational Safety and Health Act of 1970 and the Noise Control Act of 1972. Protection of the noise-exposed employee was also an objective of the Hearing Conservation Act of 1971. Subsequent studies have confirmed the benefits of periodic hearing tests for workers exposed to hazardous noise and of otologic evaluation as part of the hearing conservation process. Research studies in laboratory animals, using scanning electron microscopical techniques, have demonstrated that damage to the inner ear and organ of hearing can occur even though subjective (conditioned) response to sound stimuli remains unaffected. Some investigators have employed an epidemiologic approach to identify risk factors and to develop profiles to susceptibility to noise-induced hearing loss. The need for joint involvement of workers and employers in the reduction and control of occupational noise hazards is evident.

  17. How anthropogenic noise affects foraging.

    PubMed

    Luo, Jinhong; Siemers, Björn M; Koselj, Klemen

    2015-09-01

    The influence of human activity on the biosphere is increasing. While direct damage (e.g. habitat destruction) is relatively well understood, many activities affect wildlife in less apparent ways. Here, we investigate how anthropogenic noise impairs foraging, which has direct consequences for animal survival and reproductive success. Noise can disturb foraging via several mechanisms that may operate simultaneously, and thus, their effects could not be disentangled hitherto. We developed a diagnostic framework that can be applied to identify the potential mechanisms of disturbance in any species capable of detecting the noise. We tested this framework using Daubenton's bats, which find prey by echolocation. We found that traffic noise reduced foraging efficiency in most bats. Unexpectedly, this effect was present even if the playback noise did not overlap in frequency with the prey echoes. Neither overlapping noise nor nonoverlapping noise influenced the search effort required for a successful prey capture. Hence, noise did not mask prey echoes or reduce the attention of bats. Instead, noise acted as an aversive stimulus that caused avoidance response, thereby reducing foraging efficiency. We conclude that conservation policies may seriously underestimate numbers of species affected and the multilevel effects on animal fitness, if the mechanisms of disturbance are not considered.

  18. 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.

  19. Quantum noise in optical interferometers

    SciTech Connect

    Voronov, Volodymyr G.; Weyrauch, Michael

    2010-05-15

    We study the photon counting noise in optical interferometers used for gravitational wave detection. In order to reduce quantum noise, a squeezed vacuum is injected into the usually unused input port. It is investigated under which conditions the gravitational wave signal may be amplified without increasing counting noise concurrently. Such a possibility was suggested as a consequence of the entanglement of the two output ports of a beam splitter. We find that amplification without concurrent increase of noise is not possible for reasonable squeezing parameters. Photon distributions for various beam splitter angles and squeezing parameters are calculated.

  20. Noise exposure and public health.

    PubMed Central

    Passchier-Vermeer, W; Passchier, W F

    2000-01-01

    Exposure to noise constitutes a health risk. There is sufficient scientific evidence that noise exposure can induce hearing impairment, hypertension and ischemic heart disease, annoyance, sleep disturbance, and decreased school performance. For other effects such as changes in the immune system and birth defects, the evidence is limited. Most public health impacts of noise were already identified in the 1960s and noise abatement is less of a scientific but primarily a policy problem. A subject for further research is the elucidation of the mechanisms underlying noise-induced cardiovascular disorders and the relationship of noise with annoyance and nonacoustical factors modifying health outcomes. A high priority study subject is the effects of noise on children, including cognitive effects and their reversibility. Noise exposure is on the increase, especially in the general living environment, both in industrialized nations and in developing world regions. This implies that in the twenty-first century noise exposure will still be a major public health problem. Images Figure 2 PMID:10698728

  1. High level white noise generator

    DOEpatents

    Borkowski, Casimer J.; Blalock, Theron V.

    1979-01-01

    A wide band, stable, random noise source with a high and well-defined output power spectral density is provided which may be used for accurate calibration of Johnson Noise Power Thermometers (JNPT) and other applications requiring a stable, wide band, well-defined noise power spectral density. The noise source is based on the fact that the open-circuit thermal noise voltage of a feedback resistor, connecting the output to the input of a special inverting amplifier, is available at the amplifier output from an equivalent low output impedance caused by the feedback mechanism. The noise power spectral density level at the noise source output is equivalent to the density of the open-circuit thermal noise or a 100 ohm resistor at a temperature of approximately 64,000 Kelvins. The noise source has an output power spectral density that is flat to within 0.1% (0.0043 db) in the frequency range of from 1 KHz to 100 KHz which brackets typical passbands of the signal-processing channels of JNPT's. Two embodiments, one of higher accuracy that is suitable for use as a standards instrument and another that is particularly adapted for ambient temperature operation, are illustrated in this application.

  2. Fan and pump noise control

    NASA Technical Reports Server (NTRS)

    Misoda, J.; Magliozzi, B.

    1973-01-01

    The development is described of improved, low noise level fan and pump concepts for the space shuttle. In addition, a set of noise design criteria for small fans and pumps was derived. The concepts and criteria were created by obtaining Apollo hardware test data to correlate and modify existing noise estimating procedures. A set of space shuttle selection criteria was used to determine preliminary fan and pump concepts. These concepts were tested and modified to obtain noise sources and characteristics which yield the design criteria and quiet, efficient space shuttle fan and pump concepts.

  3. Noise reduction experience at Hughes Helicopter, Inc.

    NASA Technical Reports Server (NTRS)

    Janakiram, D. S.

    1982-01-01

    Noise reduction is mostly limited to light helicopters whose noise signature is dominated by their tail rotors. It is primarily hardware oriented. Well known noise reduction techniques such as reduction of rotor speeds with an accompanying increase in solidity to maintain performance, engine noise reduction with the use of exhaust mufflers, and acoustic blanketing of transmission and engine compartment are used. The concept of blade phasing as a means of reducing tail rotor noise is also used. Engine noise (exhaust noise), power train noise and airframe noise becomes important at low rotor tip speeds and means must be found to reduce these noise sources if further noise reductions are desired. The use of a special test rig aids in isolating the various noise sources and arriving at the penalties (performance or payload) involved in quieting them. Significant noise reduction are achieved for the light helicopter with minimum performance or weight penalties because of the dominance of a single noise source (the tail rotor).

  4. Noise reduction experience at Hughes Helicopter, Inc.

    NASA Technical Reports Server (NTRS)

    Janakiram, D. S.

    1982-01-01

    Noise reduction is mostly limited to light helicopters whose noise signature is dominated by their tail rotors. It is primarily hardware oriented. Well known noise reduction techniques such as reduction of rotor speeds with an accompanying increase in solidity to maintain performance, engine noise reduction with the use of exhaust mufflers, and acoustic blanketing of transmission and engine compartment are used. The concept of blade phasing as a means of reducing tail rotor noise is also used. Engine noise (exhaust noise), power train noise and airframe noise becomes important at low rotor tip speeds and means must be found to reduce these noise sources if further noise reductions are desired. The use of a special test rig aids in isolating the various noise sources and arriving at the penalties (performance or payload) involved in quieting them. Significant noise reduction are achieved for the light helicopter with minimum performance or weight penalties because of the dominance of a single noise source (the tail rotor).

  5. Noise sampling issues for impact/impulse noise surveys

    NASA Astrophysics Data System (ADS)

    Prince, Mary M.; Vipperman, Jeffrey S.

    2003-04-01

    Noise-induced hearing loss (NIHL) has been recognized as a serious health concern for decades. ISO Standard 1999:1990 provides a means to predict noise-induced hearing loss (NIHL) based on LAeq measurements in the working environments of workers. This standard seems to work well for predicting hearing loss in continuous noise fields. However, it is possible that ISO 1999 does not apply well to impact, impulsive, or other transient noise fields. NIOSH and University of Pittsburgh are currently developing noise-sampling strategies to measure impact and impulse noise in a manufacturing environment with the aim of developing new impulsive noise metrics. As part of the study, broadband impact/impulse pressure measurements will be made. Issues such as instrumentation, data quality, repeatability, spatial sampling, equipment portability, and calibration are addressed. Also, the annotation, digitization, and editing of the waveforms will be discussed. As part of the project, an archival database of manufacturing impulse/impact will be created to support the future algorithmic development. The ultimate goal of the project is to develop new metrics to characterize the hazards of impact/impulse noise that will complement ISO 1999 for predicting NIHL.

  6. Physiological, Psychological, and Social Effects of Noise

    NASA Technical Reports Server (NTRS)

    Kryter, K. D.

    1984-01-01

    The physiological, and behavioral effects of noise on man are investigated. Basic parameters such as definitions of noise, measuring techniques of noise, and the physiology of the ear are presented prior to the development of topics on hearing loss, speech communication in noise, social effects of noise, and the health effects of noise pollution. Recommendations for the assessment and subsequent control of noise is included.

  7. GRACE star camera noise

    NASA Astrophysics Data System (ADS)

    Harvey, Nate

    2016-08-01

    Extending results from previous work by Bandikova et al. (2012) and Inacio et al. (2015), this paper analyzes Gravity Recovery and Climate Experiment (GRACE) star camera attitude measurement noise by processing inter-camera quaternions from 2003 to 2015. We describe a correction to star camera data, which will eliminate a several-arcsec twice-per-rev error with daily modulation, currently visible in the auto-covariance function of the inter-camera quaternion, from future GRACE Level-1B product releases. We also present evidence supporting the argument that thermal conditions/settings affect long-term inter-camera attitude biases by at least tens-of-arcsecs, and that several-to-tens-of-arcsecs per-rev star camera errors depend largely on field-of-view.

  8. Experiments on propeller noise

    NASA Astrophysics Data System (ADS)

    Grosche, F. R.; Stiewitt, H.

    Propeller sound generation was investigated. Tests were performed at flow velocities up to 58 m/sec on 90 cm dia. four bladed propellers driven by an electric motor enclosed in a streamlined nacelle. Five models with different blade geometries were tested at helical tip Mach numbers up to 0.69. Nearfield blade tip measurements were made at 0.14 dia. by an in-flow microphone. The acoustic far field was measured by four microphones outside the wind tunnel flow 2.7 m from the propeller axis. An acoustic mirror telescope with three microphones was used to investigate sound generation from the upper, central and lower parts of the propeller. The spectrum in the propeller plane is dominated by the tonal components at the blade passing frequency and its harmonics. Tonal component amplitude is greatly reduced downstream. The blades radiate high frequency noise mainly in motion direction.

  9. Noise, Diffusion, and Hyperuniformity

    NASA Astrophysics Data System (ADS)

    Hexner, Daniel; Levine, Dov

    2017-01-01

    We consider driven many-particle models which have a phase transition between an active and an absorbing phase. Like previously studied models, we have particle conservation, but here we introduce an additional symmetry—when two particles interact, we give them stochastic kicks which conserve the center of mass. We find that the density fluctuations in the active phase decay in the fastest manner possible for a disordered isotropic system, and we present arguments that the large scale fluctuations are determined by a competition between a noise term which generates fluctuations, and a deterministic term which reduces them. Our results may be relevant to shear experiments and may further the understanding of hyperuniformity which occurs at the critical point.

  10. Active Noise Control of Radiated Noise from Jets Originating NASA

    NASA Technical Reports Server (NTRS)

    Doty, Michael J.; Fuller, Christopher R.; Schiller, Noah H.; Turner, Travis L.

    2013-01-01

    The reduction of jet noise using a closed-loop active noise control system with highbandwidth active chevrons was investigated. The high frequency energy introduced by piezoelectrically-driven chevrons was demonstrated to achieve a broadband reduction of jet noise, presumably due to the suppression of large-scale turbulence. For a nozzle with one active chevron, benefits of up to 0.8 dB overall sound pressure level (OASPL) were observed compared to a static chevron nozzle near the maximum noise emission angle, and benefits of up to 1.9 dB OASPL were observed compared to a baseline nozzle with no chevrons. The closed-loop actuation system was able to effectively reduce noise at select frequencies by 1-3 dB. However, integrated OASPL did not indicate further reduction beyond the open-loop benefits, most likely due to the preliminary controller design, which was focused on narrowband performance.

  11. Assessment of Domestic Appliance Noise.

    NASA Astrophysics Data System (ADS)

    Brooks, Jeanette Rosamond

    Available from UMI in association with The British Library. The aims of this study were: (i) to identify the factors involved in eliciting a subjective reaction to domestic appliance noise, (ii) to identify the noise index (or indices) that correlate highly with a subjective reaction to the noise, and (iii) to investigate the contribution of domestic appliance noise to an individual's daily noise dose. Two series of experimental studies were carried out using several examples of each of five types of domestic appliances. One determined the index values of domestic appliance noise--namely L_{WA} (using ISO 3741), L_{pA} , L_{pD}, L _{p}, PNL, L_{Aeq, 30 sec}, L_{Amax} and L_{AX}; the other determined subjective reactions to domestic appliance noise (judgements of noisiness, annoyance, the acceptability of the appliance noise and appraisals of usefulness). The success or failure of the research hypotheses was assessed statistically by analysis of variance, regression analysis, log linear analysis, Hotelling test, bootstrapping, t-test and post-hoc comparisons. Ratings of annoyance, noisiness and the acceptability of the noise of the appliance were found to be interrelated and interdependent, and not influenced by appraisals of usefulness of the appliances. Noisiness ratings were the most consistent of the subjective ratings investigated, and were influenced by the duration of the exposure, and the actual appliance type under investigation. Significant correlations were obtained between noisiness ratings and all the noise indices under investigation. However, statistical analysis demonstrated that L_ {WA} correlated less successfully with noisiness ratings than all other indices. L_ {Amax},L_{Aeq,30 sec }, and L_{AX} indices were the most successful. It is therefore suggested that the labelling of domestic appliance noise consist of L_{WA} and L _{Aeq} as measured in a standardised test environment. The percentage contribution of domestic appliance noise to the total

  12. Rotor blade vortex interaction noise

    NASA Astrophysics Data System (ADS)

    Yu, Yung H.

    2000-02-01

    Blade-vortex interaction noise-generated by helicopter main rotor blades is one of the most severe noise problems and is very important both in military applications and community acceptance of rotorcraft. Research over the decades has substantially improved physical understanding of noise-generating mechanisms, and various design concepts have been investigated to control noise radiation using advanced blade planform shapes and active blade control techniques. The important parameters to control rotor blade-vortex interaction noise and vibration have been identified: blade tip vortex structures and its trajectory, blade aeroelastic deformation, and airloads. Several blade tip design concepts have been investigated for diffusing tip vortices and also for reducing noise. However, these tip shapes have not been able to substantially reduce blade-vortex interaction noise without degradation of rotor performance. Meanwhile, blade root control techniques, such as higher-harmonic pitch control (HHC) and individual blade control (IBC) concepts, have been extensively investigated for noise and vibration reduction. The HHC technique has proved the substantial blade-vortex interaction noise reduction, up to 6 dB, while vibration and low-frequency noise have been increased. Tests with IBC techniques have shown the simultaneous reduction of rotor noise and vibratory loads with 2/rev pitch control inputs. Recently, active blade control concepts with smart structures have been investigated with the emphasis on active blade twist and trailing edge flap. Smart structures technologies are very promising, but further advancements are needed to meet all the requirements of rotorcraft applications in frequency, force, and displacement.

  13. Consumer oriented product noise testing

    NASA Astrophysics Data System (ADS)

    Blomberg, Les

    2005-09-01

    This paper explores the need for product noise measurements and how best to meet that need in the near future. Currently there is only a small market place for quieter consumer products. This is not because of lack of interest. No one really wants to announce to everyone in their house that they just flushed the toilet, few really want the entire neighborhood to know they are mowing their yard, etc. The small market place is primarily due to a lack of regulations on product noise, a lack of information easily available to consumers about which products are quieter, and market consolidation resulting in fewer manufacturers, most of whom are unwilling to emphasize their quieter products at the risk of eroding sales of their noisier ones (that currently have greater market share). In the absence of the EPA fulfilling its statutory requirement to regulate and label product noise under the Noise Control Act of 1972, and with the unwillingness of most industries to voluntarily publish accurate product noise data, there is a significant role for ``Consumer Oriented Product Noise Testing.'' This paper explores the Noise Pollution Clearinghouse's ongoing and planned product noise testing, evaluating its advantages, disadvantages, and limitations.

  14. Noise Reduction by Signal Accumulation

    ERIC Educational Resources Information Center

    Kraftmakher, Yaakov

    2006-01-01

    The aim of this paper is to show how the noise reduction by signal accumulation can be accomplished with a data acquisition system. This topic can be used for student projects. In many cases, the noise reduction is an unavoidable part of experimentation. Several techniques are known for this purpose, and among them the signal accumulation is the…

  15. Tuning noise in gene expression.

    PubMed

    Tyagi, Sanjay

    2015-05-05

    The relative contribution of promoter architecture and the associated chromatin environment in regulating gene expression noise has remained elusive. In their recent work, Arkin, Schaffer and colleagues (Dey et al, 2015) show that mean expression and noise for a given promoter at different genomic loci are uncorrelated and influenced by the local chromatin environment.

  16. Predicting Noise From Wind Turbines

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.

    1990-01-01

    Computer program WINDY predicts broadband noise spectra of horizontal-axis wind-turbine generators. Enables adequate assessment of impact of broadband wind-turbine noise. Effects of turbulence, trailing-edge wakes, and bluntness taken into account. Program has practical application in design and siting of wind-turbine machines acceptable to community. Written in GW-Basic.

  17. Anthropogenic noise affects vocal interactions.

    PubMed

    McMullen, Heather; Schmidt, Rouven; Kunc, Hansjoerg P

    2014-03-01

    Animal communication plays a crucial role in many species, and it involves a sender producing a signal and a receiver responding to that signal. The shape of a signal is determined by selection pressures acting upon it. One factor that exerts selection on acoustic signals is the acoustic environment through which the signal is transmitted. Recent experimental studies clearly show that senders adjust their signals in response to increased levels of anthropogenic noise. However, to understand how noise affects the whole process of communication, it is vital to know how noise affects the receiver's response during vocal interactions. Therefore, we experimentally manipulated ambient noise levels to expose male European robins (Erithacus rubecula) to two playback treatments consisting of the same song: one with noise and another one without noise. We found that males responding to a conspecific in a noise polluted environment increased minimum frequency and decreased song complexity and song duration. Thus, we show that the whole process of communication is affected by noise, not just the behaviour of the sender.

  18. White noise and sleep induction.

    PubMed Central

    Spencer, J A; Moran, D J; Lee, A; Talbert, D

    1990-01-01

    We studied two groups of 20 neonates, between 2 and 7 days old, in a randomised trial. Sixteen (80%) fell asleep within five minutes in response to white noise compared with only five (25%) who fell asleep spontaneously in the control group. White noise may help mothers settle difficult babies. PMID:2405784

  19. Predicting Noise From Wind Turbines

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.

    1990-01-01

    Computer program WINDY predicts broadband noise spectra of horizontal-axis wind-turbine generators. Enables adequate assessment of impact of broadband wind-turbine noise. Effects of turbulence, trailing-edge wakes, and bluntness taken into account. Program has practical application in design and siting of wind-turbine machines acceptable to community. Written in GW-Basic.

  20. 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.

  1. Noise Reduction by Signal Accumulation

    ERIC Educational Resources Information Center

    Kraftmakher, Yaakov

    2006-01-01

    The aim of this paper is to show how the noise reduction by signal accumulation can be accomplished with a data acquisition system. This topic can be used for student projects. In many cases, the noise reduction is an unavoidable part of experimentation. Several techniques are known for this purpose, and among them the signal accumulation is the…

  2. Noise sensitivity: A neurophenomenological perspective.

    PubMed

    Dzhambov, Angel M

    2015-11-01

    This paper addresses the current limitations of noise sensitivity research and the benefit of undertaking a neurophenomenological approach of investigation. It begins by questioning the invariance of noise sensitivity across different studies and contexts and argues that these are issues associated with the psychometric construct rather than the underlying reaction patterns. It suggest that our definition and operationalization of noise sensitivity might have been misspecified and that it needs to be revised on the basis of heuristically derived first-person data about our experiences of noise. It then shows why the basic principles of the neurophenomenological program are applicable to psychoacoustic research. Namely, it argues that phenomenological training leading to reflexive introspection and verbalization of our susceptibility to noise might have three-fold implication - (i) it will generate deeper understanding of noise sensitivity which will then allow us to deduce a hierarchical structure of meaning and concepts to supplement and be fed to quantitative research, (ii) it will provide better interpretation of neuroimaging and electroencephalographic data related to noise reaction and perception, which in turn will allow a process of reciprocal validation, (iii) and, most importantly, it presents a promising technique for emotional regulation of noise processing via modulation of the amygdalar function, when a state of awareness of this processing has been achieved.

  3. Television noise-reduction device

    NASA Technical Reports Server (NTRS)

    Stamps, J. C.; Gordon, B. L.

    1973-01-01

    System greatly improves signal-to-noise ratio with little or no loss in picture resolution. By storage of luminance component, which is summed with chrominance component, system performs mathematical integration of basically-repetitive television signals. Integration of signals over interval of their repetition causes little change in original signals and eliminates random noise.

  4. Transient noise suppression algorithm in speech system

    NASA Astrophysics Data System (ADS)

    Cao, Keyu; Wang, Mingjiang

    2017-08-01

    In this paper, I mainly introduce the algorithm of transient noise suppression in speech system. Firstly, it divides into impulsive noise and other types of transient noise according to the characteristics of transient noise. In the impulse noise suppression algorithm, I mainly use the averaging energy threshold method to detect the impulse noise, and then I use the amplitude threshold method to reduce the impulse noise which was detected. In the other types of transient noise suppression algorithm, I mainly use the Optimally Modified-Log Spectral Amplitude estimation (OM-LSA) algorithm and the Minimum Control Recursive Average (MCRA) algorithm to suppress the transient noise.

  5. Noise exposure in convertible automobiles.

    PubMed

    Mikulec, A A; Lukens, S B; Jackson, L E; Deyoung, M N

    2011-02-01

    To quantify the noise exposure received while driving a convertible automobile with the top open, compared with the top closed. Five different convertible automobiles were driven, with the top both closed and open, and noise levels measured. The cars were tested at speeds of 88.5, 104.6 and 120.7 km/h. When driving with the convertible top open, the mean noise exposure ranged from 85.3 dB at 88.5 km/h to 89.9 dB at 120.7 km/h. At the tested speeds, noise exposure increased by an average of 12.4-14.6 dB after opening the convertible top. Driving convertible automobiles at speeds exceeding 88.5 km/h, with the top open, may result in noise exposure levels exceeding recommended limits, especially when driving with the convertible top open for prolonged periods.

  6. Noise Injury: Etiology and Prevention

    PubMed Central

    Lees, R. E. M.

    1982-01-01

    Exposure to noise might be responsible for a wide and varied spectrum of physical and mental morbidity, although many of the claims of cause and effect relationship are controversial and unproven. The etiological relationship between noise and high frequency hearing loss is, however, well documented. While noise-induced hearing loss is considered to be primarily an occupational problem, current leisure time activities have created the potential for it to become more common in the community at large. Once developed, this hearing loss is permanent and cannot be influenced by therapy. Noise-induced hearing loss is almost completely preventable and the family physician has an important responsibility for primary and secondary prevention, whether the noise source is in the workplace or in some other location. PMID:21286519

  7. Noise reduction for vocal pathologies.

    PubMed

    Matassini, L; Manfredi, C

    2002-01-01

    A noise reduction scheme, particularly suited for the correction of vocal pathologies, is proposed. The filter makes use of concepts originated within the theory of dynamical systems and deterministic chaos. In particular, the idea of embedding scalar data in order to reconstruct a phase space is of fundamental importance here. Furthermore, the concept of an attractor as a result of dynamical constraints is exploited. In order to perform noise reduction one needs redundancy and the human voice provides it even within a phoneme, namely the smallest structural unit of speech. Due to several repetitions of a pattern called pitch inside a phoneme, separation between the pure voice signal and the noise is possible, provided the latter is uncorrelated with the former. With a proper parameter tuning, different kinds of noise can be removed. We describe the idea behind the noise reduction algorithm and present applications to vocal pathologies.

  8. Multiplicative noise enhances spatial reciprocity

    NASA Astrophysics Data System (ADS)

    Yao, Yao; Chen, Shen-Shen

    2014-11-01

    Recent research has identified the heterogeneity as crucial for the evolution of cooperation in spatial population. However, the influence of heterogeneous noise is still lacking. Inspired by this interesting question, in this work, we try to incorporate heterogeneous noise into the evaluation of utility, where only a proportion of population possesses noise, whose range can also be tuned. We find that increasing heterogeneous noise monotonously promotes cooperation and even translates the full defection phase (of the homogeneous version) into the complete cooperation phase. Moreover, the promotion effect of this mechanism can be attributed to the leading role of cooperators who have the heterogeneous noise. These type of cooperators can attract more agents penetrating into the robust cooperator clusters, which is beyond the text of traditional spatial reciprocity. We hope that our work may shed light on the understanding of the cooperative behavior in the society.

  9. Jet shielding of jet noise

    NASA Technical Reports Server (NTRS)

    Simonich, J. C.; Amiet, R. K.; Schlinker, R. H.

    1986-01-01

    An experimental and theoretical study was conducted to develop a validated first principle analysis for predicting the jet noise reduction achieved by shielding one jet exhaust flow with a second, closely spaced, identical jet flow. A generalized fuel jet noise analytical model was formulated in which the acoustic radiation from a source jet propagates through the velocity and temperature discontinuity of the adjacent shielding jet. Input variables to the prediction procedure include jet Mach number, spacing, temperature, diameter, and source frequency. Refraction, diffraction, and reflection effects, which control the dual jet directivity pattern, are incorporated in the theory. The analysis calculates the difference in sound pressure level between the dual jet configuration and the radiation field based on superimposing two independent jet noise directivity patterns. Jet shielding was found experimentally to reduce noise levels in the common plane of the dual jet system relative to the noise generated by two independent jets.

  10. Preamplifier Noise in VLF Receivers

    NASA Technical Reports Server (NTRS)

    Burhans, R. W.

    1978-01-01

    Noise specifications for junction field-effect transistors are presented in different ways depending on the particular semiconductor manufacturer. Arithmetic involved in converting these specifications to equivalent RMS noise in microvolts developed at the preamplifier input terminal is reviewed. These methods were useful for estimating the noise performance of high input impedance preamplifiers used with E-field antennas operating in the range of 1 KHz to 10 MHz. Both the JFET MPF-102 transistor and the COS/MOS CA3600 transistor array provided amplification for VLF receivers where the internally generated noise was well below the atmospheric noise level. The CA3600 transistor array provided better performance because of the more symmetrical complementary MOS transistor transfer characteristics than a single N-type biased JFET transistor. The CMOS amplifier resulted in self-compensating gain characteristics over a very wide temperature range from -55 to +125 C.

  11. 23 CFR 772.19 - Construction noise.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 23 Highways 1 2011-04-01 2011-04-01 false Construction noise. 772.19 Section 772.19 Highways... ABATEMENT OF HIGHWAY TRAFFIC NOISE AND CONSTRUCTION NOISE § 772.19 Construction noise. The following general... may be affected by noise from construction of the project. The identification is to be performed...

  12. 23 CFR 772.19 - Construction noise.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 23 Highways 1 2010-04-01 2010-04-01 false Construction noise. 772.19 Section 772.19 Highways... ABATEMENT OF HIGHWAY TRAFFIC NOISE AND CONSTRUCTION NOISE § 772.19 Construction noise. The following general... may be affected by noise from construction of the project. The identification is to be performed...

  13. 23 CFR 772.11 - Noise abatement.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... OF HIGHWAY TRAFFIC NOISE AND CONSTRUCTION NOISE § 772.11 Noise abatement. (a) In determining and abating traffic noise impacts, primary consideration is to be given to exterior areas. Abatement will usually be necessary only where frequent human use occurs and a lowered noise level would be of...

  14. A Literature Survey of Noise Pollution.

    ERIC Educational Resources Information Center

    Shih, H. H.

    Physically, noise is a complex sound that has little or no periodicity. However, the essential characteristic of noise is its undesirability. Thus, noise can be defined as any annoying or unwanted sound. In recent years, the rapid increase of noise level in our environment has become a national public health hazard. Noise affects man's state of…

  15. A Literature Survey of Noise Pollution.

    ERIC Educational Resources Information Center

    Shih, H. H.

    Physically, noise is a complex sound that has little or no periodicity. However, the essential characteristic of noise is its undesirability. Thus, noise can be defined as any annoying or unwanted sound. In recent years, the rapid increase of noise level in our environment has become a national public health hazard. Noise affects man's state of…

  16. 23 CFR 772.19 - Construction noise.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 23 Highways 1 2014-04-01 2014-04-01 false Construction noise. 772.19 Section 772.19 Highways... ABATEMENT OF HIGHWAY TRAFFIC NOISE AND CONSTRUCTION NOISE § 772.19 Construction noise. For all Type I and II projects, a highway agency shall: (a) Identify land uses or activities that may be affected by noise from...

  17. 23 CFR 772.19 - Construction noise.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 23 Highways 1 2013-04-01 2013-04-01 false Construction noise. 772.19 Section 772.19 Highways... ABATEMENT OF HIGHWAY TRAFFIC NOISE AND CONSTRUCTION NOISE § 772.19 Construction noise. For all Type I and II projects, a highway agency shall: (a) Identify land uses or activities that may be affected by noise from...

  18. Recent Advances in Studies of Current Noise

    NASA Astrophysics Data System (ADS)

    Blanter, Yaroslav M.

    This is a brief review of recent activities in the field of current noise intended for newcomers. We first briefly discuss main properties of shot noise in nanostructures, and then turn to recent developments, concentrating on issues related to experimental progress: non-symmetrized cumulants and quantum noise; counting statistics; super-Poissonian noise; current noise and interferometry

  19. 23 CFR 772.11 - Noise abatement.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... OF HIGHWAY TRAFFIC NOISE AND CONSTRUCTION NOISE § 772.11 Noise abatement. (a) In determining and abating traffic noise impacts, primary consideration is to be given to exterior areas. Abatement will usually be necessary only where frequent human use occurs and a lowered noise level would be of...

  20. The Effects of Noise on Pupil Performance.

    ERIC Educational Resources Information Center

    Slater, Barbara Ruth

    Effects of school noise conditions on student written task performance were studied. Three noise levels were examined--(1) irregular interval noise, 75-90 decibels, (2) average or normal noise, and (3) quiet condition, 45-55 decibels. An attempt was made to reproduce noise conditions typical of the school environment. A second controlled…

  1. 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.

  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. General Aviation Interior Noise. Part 3; Noise Control Measure Evaluation

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    The work reported herein is an extension to the work accomplished under NASA Grant NAG1-2091 on the development of noise/source/path identification techniques for single engine propeller driven General Aviation aircraft. The previous work developed a Conditioned Response Analysis (CRA) technique to identify potential noise sources that contributed to the dominating tonal responses within the aircraft cabin. The objective of the present effort was to improve and verify the findings of the CRA and develop and demonstrate noise control measures for single engine propeller driven General Aviation aircraft.

  4. Noise exposure in oil mills

    PubMed Central

    Kumar, G. V. Prasanna; Dewangan, K. N.; Sarkar, Amaresh

    2008-01-01

    Context: Noise of machines in various agro-based industries was found to be the major occupational hazard for the workers of industries. The predominant noise sources need to be identified and the causes of high noise need to be studied to undertake the appropriate measures to reduce the noise level in one of the major agro-based industries, oil mills. Aims: To identify the predominant noise sources in the workrooms of oil mills. To study the causes of noise in oil mills. To measure the extent of noise exposure of oil mill workers. To examine the response of workers towards noise, so that appropriate measures can be undertaken to minimize the noise exposure. Settings and Design: A noise survey was conducted in the three renowned oil mills of north-eastern region of India. Materials and Methods: Information like output capacity, size of power source, maintenance condition of the machines and workroom configurations of the oil mills was collected by personal observations and enquiry with the owner of the mill. Using a Sound Level Meter (SLM) (Model-824, Larson and Davis, USA), equivalent SPL was measured at operator's ear level in the working zone of the workers near each machine of the mills. In order to study the variation of SPL in the workrooms of the oil mill throughout its operation, equivalent SPL was measured at two appropriate locations of working zone of the workers in each mill. For conducting the noise survey, the guidelines of Canadian Centre for Occupational Health and Safety (CCOHS) were followed. Grid points were marked on the floor of the workroom of the oil mill at a spacing of 1 m × 1 m. SPL at grid points were measured at about 1.5 m above the floor. The direction of the SLM was towards the nearby noisy source. To increase accuracy, two replications were taken at each grid point. All the data were recorded for 30 sec. At the end of the experiment, data were downloaded to a personal computer. With the help of utility software of Larson and Davis

  5. Rocket noise - A review

    NASA Astrophysics Data System (ADS)

    McInerny, S. A.

    1990-10-01

    This paper reviews what is known about far-field rocket noise from the controlled studies of the late 1950s and 1960s and from launch data. The peak dimensionless frequency, the dependence of overall sound power on exhaust parameters, and the directivity of the overall sound power of rockets are compared to those of subsonic jets and turbo-jets. The location of the dominant sound source in the rocket exhaust plume and the mean flow velocity in this region are discussed and shown to provide a qualitative explanation for the low peak Strouhal number, fD(e)/V(e), and large angle of maximum directivity. Lastly, two empirical prediction methods are compared with data from launches of a Titan family vehicle (two, solid rocket motors of 5.7 x 10 to the 6th N thrust each) and the Saturn V (five, liquid oxygen/rocket propellant engines of 6.7 x 10 to the 6th N thrust, each). The agreement is favorable. In contrast, these methods appear to overpredict the far-field sound pressure levels generated by the Space Shuttle.

  6. 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.

  7. Signal with Flat Phase Noise Using a Carrier and the Power Spectral Density of White Noise for Phase Noise Standards

    NASA Astrophysics Data System (ADS)

    Watabe, Ken-ichi; Yanagimachi, Shinya; Ikegami, Takeshi; Iida, Hitoshi; Shimada, Yozo

    2012-01-01

    We have realized a phase noise standard of a signal with a -100 dBc/Hz flat phase noise at 10 MHz for Fourier frequencies of 1 Hz to 100 kHz, which ensures traceability to the International System of Units (SI). The flat phase noise signal is produced using a carrier combined with white noise. To ensure traceability, both the flat phase noise signal power and the power spectral density of white noise are determined with a calibrated power meter and the noise standard, respectively. The flatness of the phase noise standard is within ±0.7 dB.

  8. Hydrodynamic noise and surface compliance

    NASA Astrophysics Data System (ADS)

    Vonwinkle, W. A.; Fitzgerald, J.; Carey, W. M.; Bakewell, H. P., Jr.

    1982-09-01

    This document discusses the role of surface compliance on hydrodynamic noise and is based on a review of theoretical and experimental flow-noise investigations. Basic flow-noise theories are discussed in light of compliant surface boundary conditions. A comprehensive review of the experimental results of compliant surface flow-noise experiments is presented. Surface compliance can effect the measured noise; however, the compliance of the surfaces used in previous experiments was not adequately described. Consequently, results varied and showed a marked, but undefined, temperature dependence. The characterization of the complex surface compliance is discussed, including effects of frequency and temperature. A method that characterizes surface compliance is denoted and used to measure the properties of several mammalian tissues. Then a discussion and a comparison of these results to the wavenumber spectra data follows. An experimental investigation of the effect of surface compliance on the hydrodynamic noise is proposed by means of measurement of material properties, measurement of wall pressure fluctuation spectra, holographic representation of the surface displacement, and characterization of the TBL boundary layer to determine the magnitude and role of complex surface compliance of the TBL and its flow noise.

  9. Industrial jet noise: Coanda nozzles

    NASA Astrophysics Data System (ADS)

    Li, P.; Halliwell, N. A.

    1985-04-01

    Within the U.K. manufacturing industries noise from industrial jets ranks third as a major contributor to industrial deafness. Noise control is hindered because use is made of the air once it has exuded from the nozzle exit. Important tasks include swarf removal, paint spreading, cooling, etc. Nozzles which employ the Coanda effect appear to offer the possibility of significant noise reduction whilst maintaining high thrust efficiency when compared with the commonly used simple open pipe or ordinary convergent nozzle. In this paper the performance of Coanda-type nozzles is examined in detail and an index rating for nozzle performance is introduced. Results show that far field stagnation pressure distributions are Gaussian and similar in all cases with a dispersion coefficient σ = 0·64. Noise reduction and thrust efficiency are shown to be closely related to the design geometry of the central body of the nozzle. Performance is based on four fundamental characteristics, these being the noise level at 1 m from the exit and at a 90° station to the nozzle axis, and the thrust on a chosen profile, the noise reduction and the thrust efficiency. Physically, performance is attributed to flow near field effects where, although all nozzles are choked, shock cell associated noise is absent.

  10. Pavement noise measurements in Poland

    NASA Astrophysics Data System (ADS)

    Zofka, Ewa; Zofka, Adam; Mechowski, Tomasz

    2017-09-01

    The objective of this study is to investigate the feasibility of the On-Board Sound Intensity (OBSI) system to measure tire-pavement noise in Poland. In general, sources of noise emitted by the modern vehicles are the propulsion noise, aerodynamic resistance and noise generated at the tire-pavement interface. In order to capture tire-pavement noise, the OBSI system uses a noise intensity probe installed in the close proximity of that interface. In this study, OBSI measurements were performed at different types of pavement surfaces such as stone mastic asphalt (SMA), regular asphalt concrete (HMA) as well as Portland cement concrete (PCC). The influence of several necessary OBSI measurement conditions were recognized as: testing speed, air temperature, tire pressure and tire type. The results of this study demonstrate that the OBSI system is a viable and robust tool that can be used for the quality evaluation of newly built asphalt pavements in Poland. It can be also applied to generate reliable input parameters for the noise propagation models that are used to assess the environmental impact of new and existing highway corridors.

  11. Noise in eukaryotic gene expression

    NASA Astrophysics Data System (ADS)

    Blake, William J.; KÆrn, Mads; Cantor, Charles R.; Collins, J. J.

    2003-04-01

    Transcription in eukaryotic cells has been described as quantal, with pulses of messenger RNA produced in a probabilistic manner. This description reflects the inherently stochastic nature of gene expression, known to be a major factor in the heterogeneous response of individual cells within a clonal population to an inducing stimulus. Here we show in Saccharomyces cerevisiae that stochasticity (noise) arising from transcription contributes significantly to the level of heterogeneity within a eukaryotic clonal population, in contrast to observations in prokaryotes, and that such noise can be modulated at the translational level. We use a stochastic model of transcription initiation specific to eukaryotes to show that pulsatile mRNA production, through reinitiation, is crucial for the dependence of noise on transcriptional efficiency, highlighting a key difference between eukaryotic and prokaryotic sources of noise. Furthermore, we explore the propagation of noise in a gene cascade network and demonstrate experimentally that increased noise in the transcription of a regulatory protein leads to increased cell-cell variability in the target gene output, resulting in prolonged bistable expression states. This result has implications for the role of noise in phenotypic variation and cellular differentiation.

  12. Noise in nonlinear nanomechanical resonators

    NASA Astrophysics Data System (ADS)

    Cleland, Andrew

    2006-03-01

    Noise limits the sensitivity of linear sensors, in a manner that is well understood, but also limits nonlinear systems in a less trivial way. Nonlinear nanomechanical resonators present interesting possibilities for the sensitive detection of forces and masses, but the noise limitations have not been explored much to date. Here we report on noise effects on nonlinear resonators operated in regimes where they have either one or two stable attractors. We have made quantitative measurements of the nonlinear response of a radiofrequency mechanical resonator with very high quality factor, measuring the noise-free transitions between the two attractors, and find good agreement with theory. We measure the transition rate response to controlled levels of white noise, and extract the basin activation energy. This allows us to obtain precise values for the relevant frequencies and the cubic nonlinearity in the Duffing oscillator, with applications to parametric sensing, in particular mass sensing. References: ``Noise-enabled precision measurements of a Duffing nanomechanical resonator,'' J.S. Aldridge and A.N. Cleland, Phys. Rev. Lett. 94, 156403 (2005). ``Thermomechanical noise limits on parametric sensing with nanomechanical resonators,'' A.N. Cleland, New J. Phys. 7, 235 (2005).

  13. Airframe-Jet Engine Integration Noise

    NASA Technical Reports Server (NTRS)

    Tam, Christopher; Antcliff, Richard R. (Technical Monitor)

    2003-01-01

    It has been found experimentally that the noise radiated by a jet mounted under the wing of an aircraft exceeds that of the same jet in a stand-alone environment. The increase in noise is referred to as jet engine airframe integration noise. The objectives of the present investigation are, (1) To obtain a better understanding of the physical mechanisms responsible for jet engine airframe integration noise or installation noise. (2) To develop a prediction model for jet engine airframe integration noise. It is known that jet mixing noise consists of two principal components. They are the noise from the large turbulence structures of the jet flow and the noise from the fine scale turbulence. In this investigation, only the effect of jet engine airframe interaction on the fine scale turbulence noise of a jet is studied. The fine scale turbulence noise is the dominant noise component in the sideline direction. Thus we limit out consideration primarily to the sideline.

  14. Noise Pollution--What can be Done?

    ERIC Educational Resources Information Center

    Shaw, Edgar A. G.

    1975-01-01

    Discusses the ratio of energy dissipated as sound to the mechanical output of devices. Considers noise levels, ranges vs. peaks, noise indexes, and health hazards. Indicates some problems vs. solutions in the technology of noise control. (GH)

  15. Noise Pollution--What can be Done?

    ERIC Educational Resources Information Center

    Shaw, Edgar A. G.

    1975-01-01

    Discusses the ratio of energy dissipated as sound to the mechanical output of devices. Considers noise levels, ranges vs. peaks, noise indexes, and health hazards. Indicates some problems vs. solutions in the technology of noise control. (GH)

  16. Airframe-Jet Engine Integration Noise

    NASA Astrophysics Data System (ADS)

    Tam, Christopher

    2003-01-01

    It has been found experimentally that the noise radiated by a jet mounted under the wing of an aircraft exceeds that of the same jet in a stand-alone environment. The increase in noise is referred to as jet engine airframe integration noise. The objectives of the present investigation are, (1) To obtain a better understanding of the physical mechanisms responsible for jet engine airframe integration noise or installation noise. (2) To develop a prediction model for jet engine airframe integration noise. It is known that jet mixing noise consists of two principal components. They are the noise from the large turbulence structures of the jet flow and the noise from the fine scale turbulence. In this investigation, only the effect of jet engine airframe interaction on the fine scale turbulence noise of a jet is studied. The fine scale turbulence noise is the dominant noise component in the sideline direction. Thus we limit out consideration primarily to the sideline.

  17. Noise Levels in the Operating Room

    DTIC Science & Technology

    2001-10-01

    from realizing the effects of noise. Florence Nightingale noticed an association between noise and patient discomfort ( Nightingale , 1969). One...recommended standard: Occupational Noise Exposure. (NIOSH Publication No. 98- 126). Cincinnati, OH: author. Nightingale , F. (1969). Notes on

  18. Mitigation of structureborne noise nuisance

    NASA Astrophysics Data System (ADS)

    Ko, Wing P.

    2005-09-01

    This paper presents a noise complaint case which was solved by me a few years ago in Hong Kong. A newlywed couple in the residential unit complained to the Government that the noise emitted from the pump room directly beneath their unit was very annoying, especially in the night-time period. The owner of the building was then required by the Government to mitigate the noise to the night-time statutory noise requirement within 30 days, otherwise he would be prosecuted. Ideally, the structureborne noise from the pump room could be effectively mitigated by installation of floating slab and vibration isolators under the pumps. Also, the water tanks and water pipes were required to be isolated from the walls and floor. However, this work was impossible to be completed within 30 days to stop the prosecution. Water supply to the above residents would be seriously interrupted during the construction period. As the only noise parameter of the statutory requirement was 30 minute A-weighted Leq, the most effective and practical way in this exigent situation was to reduce the pump operation time within any 30 minute period to decrease the Leq values. In addition, the water pipes and pumps were also required to be isolated from the walls and floor with resilient materials to break the vibration channels. These noise mitigation measures were successfully applied to the pump room before the end of the 30 days. Finally, the noise levels inside the complainant's unit were found to meet the statutory requirement. The noise complaint case was then closed by the Government.

  19. Noise-induced hearing loss.

    PubMed

    Sliwinska-Kowalska, Mariola; Davis, Adrian

    2012-01-01

    Noise-induced hearing loss (NIHL) still remains a problem in developed countries, despite reduced occupational noise exposure, strict standards for hearing protection and extensive public health awareness campaigns. Therefore NIHL continues to be the focus of noise research activities. This paper summarizes progress achieved recently in our knowledge of NIHL. It includes papers published between the years 2008-2011 (in English), which were identified by a literature search of accessible medical and other relevant databases. A substantial part of this research has been concerned with the risk of NIHL in the entertainment sector, particularly in professional, orchestral musicians. There are also constant concerns regarding noise exposure and hearing risk in "hard to control" occupations, such as farming and construction work. Although occupational noise has decreased since the early 1980s, the number of young people subject to social noise exposure has tripled. If the exposure limits from the Noise at Work Regulations are applied, discotheque music, rock concerts, as well as music from personal music players are associated with the risk of hearing loss in teenagers and young adults. Several recent research studies have increased the understanding of the pathomechanisms of acoustic trauma, the genetics of NIHL, as well as possible dietary and pharmacologic otoprotection in acoustic trauma. The results of these studies are very promising and offer grounds to expect that targeted therapies might help prevent the loss of sensory hair cells and protect the hearing of noise-exposed individuals. These studies emphasize the need to launch an improved noise exposure policy for hearing protection along with developing more efficient norms of NIHL risk assessment.

  20. Spin noise amplification and giant noise in optical microcavity

    SciTech Connect

    Ryzhov, I. I.; Poltavtsev, S. V.; Kozlov, G. G.; Zapasskii, V. S.; Kavokin, A. V.; Lagoudakis, P. V.

    2015-06-14

    When studying the spin-noise-induced fluctuations of Kerr rotation in a quantum-well microcavity, we have found a dramatic increase of the noise signal (by more than two orders of magnitude) in the vicinity of anti-crossing of the polariton branches. The effect is explained by nonlinear optical instability of the microcavity giving rise to the light-power-controlled amplification of the polarization noise signal. In the framework of the developed model of built-in amplifier, we also interpret the nontrivial spectral and intensity-related properties of the observed noise signal below the region of anti-crossing of polariton branches. The discovered effect of optically controllable amplification of broadband polarization signals in microcavities in the regime of optical instability may be of interest for detecting weak oscillations of optical anisotropy in fundamental research and for other applications in optical information processing.

  1. Airframe Noise Reduction Studies and Clean-Airframe Noise Investigation

    NASA Technical Reports Server (NTRS)

    Fink, M. R.; Bailey, D. A.

    1980-01-01

    Acoustic wind tunnel tests were conducted of a wing model with modified leading edge slat and trailing edge flap. The modifications were intended to reduce the surface pressure response to convected turbulence and thereby reduce the airframe noise without changing the lift at constant incidence. Tests were conducted at 70.7 and 100 m/sec airspeeds, with Reynolds numbers 1.5 x 10 to the 6th power and 2.1 x 10 to the 6th power. Considerable reduction of noise radiation from the side edges of a 40 deflection single slotted flap was achieved by modification to the side edge regions or the leading edge region of the flap panel. Total far field noise was reduced 2 to 3 dB over several octaves of frequency. When these panels were installed as the aft panel of a 40 deg deflection double slotted flap, 2 dB noise reduction was achieved.

  2. Developing active noise control systems for noise attenuation in ducts

    NASA Astrophysics Data System (ADS)

    Campos, Rosely V.; Ivo, Rodrigo C.; Medeiros, Eduardo B.

    2002-11-01

    The present work describes some of the research effort on Active Noise Control (ANC) being jointly developed by the Catholic University of Minas Gerais (PUC-MINAS) and the Federal University of Minas Gerais (UFMG). Considerations about the implementation of Digital Signal Processing for noise control in ducts has been presented. The objective is to establish a study on Active Noise Control in ducts combining geometry and acoustic parameters modification together with adaptive digital filtering implementation. Both algorithm and digital signal processing details are also discussed. The main results for a typical application where real attenuation has been obtained are presented and considered according to their use in developing real applications. The authors also believe that the present text should provide an interesting overview for both designers and students concerned about Active Noise Control in ducts. (To be presented in Portuguese.)

  3. 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.

  4. Fractal features of seismic noise

    NASA Astrophysics Data System (ADS)

    Caserta, A.; Consolini, G.; Michelis, P. De

    2003-04-01

    We present experimental observations and data analysis concerning the fractal features of seismic noise in the frequency range from 1 Hz to 40 Hz. In detail, we investigate the 3D average squared soil displacement and the distribution function of its fluctuations for different near-surface geological structures. We found that the seismic noise is consistent with a persistent fractal brownian motion characterized by a Hurst exponent grather than 1/2. Moreover, a clear dependence of the fractal nature of the seismic noise on the near-surface local geology has been found.

  5. Active Control of Environmental Noise

    NASA Astrophysics Data System (ADS)

    Wright, S. E.; Vuksanovic, B.

    1996-02-01

    Most of the current research on active noise control is confined to restricted spaces such as earphones, active silencers, air-conditioning ducts, truck cabins and aircraft fuselages. In this paper the basic concepts of environmental noise reduction by using active noise control in unconfined spaces are explored. The approach is to develop a controlled acoustic shadow, generated by a wall of secondary sources, to reduce unwanted sound in the direction of a complaint area. The basic acoustic theory is considered, followed by computer modelling, and some results to show the effectiveness of the approach. EA Technology and Yorkshire electric in the United Kingdom are supporting this work.

  6. Entangled light from white noise.

    PubMed

    Plenio, M B; Huelga, S F

    2002-05-13

    An atom that couples to two distinct leaky optical cavities is driven by an external optical white noise field. We describe how entanglement between the light fields sustained by two optical cavities arises in such a situation. The entanglement is maximized for intermediate values of the cavity damping rates and the intensity of the white noise field, vanishing both for small and for large values of these parameters and thus exhibiting a stochastic-resonancelike behavior. This example illustrates the possibility of generating entanglement by exclusively incoherent means and sheds new light on the constructive role noise may play in certain tasks of interest for quantum information processing.

  7. Hearing through the noise: Biologically inspired noise reduction

    NASA Astrophysics Data System (ADS)

    Lee, Tyler Paul

    Vocal communication in the natural world demands that a listener perform a remarkably complicated task in real-time. Vocalizations mix with all other sounds in the environment as they travel to the listener, arriving as a jumbled low-dimensional signal. A listener must then use this signal to extract the structure corresponding to individual sound sources. How this computation is implemented in the brain remains poorly understood, yet an accurate description of such mechanisms would impact a variety of medical and technological applications of sound processing. In this thesis, I describe initial work on how neurons in the secondary auditory cortex of the Zebra Finch extract song from naturalistic background noise. I then build on our understanding of the function of these neurons by creating an algorithm that extracts speech from natural background noise using spectrotemporal modulations. The algorithm, implemented as an artificial neural network, can be flexibly applied to any class of signal or noise and performs better than an optimal frequency-based noise reduction algorithm for a variety of background noises and signal-to-noise ratios. One potential drawback to using spectrotemporal modulations for noise reduction, though, is that analyzing the modulations present in an ongoing sound requires a latency set by the slowest temporal modulation computed. The algorithm avoids this problem by reducing noise predictively, taking advantage of the large amount of temporal structure present in natural sounds. This predictive denoising has ties to recent work suggesting that the auditory system uses attention to focus on predicted regions of spectrotemporal space when performing auditory scene analysis.

  8. Cosmological flux noise and measured noise power spectra in SQUIDs.

    PubMed

    Beck, Christian

    2016-06-20

    The understanding of the origin of 1/f magnetic flux noise commonly observed in superconducting devices such as SQUIDs and qubits is still a major unsolved puzzle. Here we discuss the possibility that a significant part of the observed low-frequency flux noise measured in these devices is ultimately seeded by cosmological fluctuations. We consider a theory where a primordial flux noise field left over in unchanged form from an early inflationary or quantum gravity epoch of the universe intrinsically influences the phase difference in SQUIDs and qubits. The perturbation seeds generated by this field can explain in a quantitatively correct way the form and amplitude of measured low-frequency flux noise spectra in SQUID devices if one takes as a source of fluctuations the primordial power spectrum of curvature fluctuations as measured by the Planck collaboration. Our theoretical predictions are in excellent agreement with recent low-frequency flux noise measurements of various experimental groups. Magnetic flux noise, so far mainly considered as a nuisance for electronic devices, may thus contain valuable information about fluctuation spectra in the very early universe.

  9. Cosmological flux noise and measured noise power spectra in SQUIDs

    NASA Astrophysics Data System (ADS)

    Beck, Christian

    2016-06-01

    The understanding of the origin of 1/f magnetic flux noise commonly observed in superconducting devices such as SQUIDs and qubits is still a major unsolved puzzle. Here we discuss the possibility that a significant part of the observed low-frequency flux noise measured in these devices is ultimately seeded by cosmological fluctuations. We consider a theory where a primordial flux noise field left over in unchanged form from an early inflationary or quantum gravity epoch of the universe intrinsically influences the phase difference in SQUIDs and qubits. The perturbation seeds generated by this field can explain in a quantitatively correct way the form and amplitude of measured low-frequency flux noise spectra in SQUID devices if one takes as a source of fluctuations the primordial power spectrum of curvature fluctuations as measured by the Planck collaboration. Our theoretical predictions are in excellent agreement with recent low-frequency flux noise measurements of various experimental groups. Magnetic flux noise, so far mainly considered as a nuisance for electronic devices, may thus contain valuable information about fluctuation spectra in the very early universe.

  10. Noise suppression by quantum control before and after the noise

    NASA Astrophysics Data System (ADS)

    Wakamura, Hiroaki; Kawakubo, Ryûitirô; Koike, Tatsuhiko

    2017-02-01

    We discuss the possibility of protecting the state of a quantum system that goes through noise by measurements and operations before and after the noise process. The aim is to seek the optimal protocol that makes the input and output states as close as possible and to clarify the role of the measurements therein. We consider two cases: one can perform quantum measurements and operations (i) only after the noise process and (ii) both before and after. We prove in a two-dimensional Hilbert space that, in case (i), the noise suppression is essentially impossible for all types of noise and, in case (ii), the optimal protocol for the depolarizing noise is either the "do nothing" protocol or the "discriminate and reprepare" protocol. These protocols are not "truly quantum" and can be considered as classical. They involve no measurement or only use the measurement outcomes. These results describe the fundamental limitations in quantum mechanics from the viewpoint of control theory. Finally, we conjecture that a statement similar to case (ii) holds for higher-dimensional Hilbert spaces and present some numerical evidence.

  11. Noise attenuation of hearing protectors against heavy weapon noise.

    PubMed

    Pääkkönen, R; Lehtomäki, K; Savolainen, S; Myllyniemi, J; Hämäläinen, E

    2000-09-01

    This study evaluated the noise attenuation of earplugs and earmuffs or their combined use against heavy weapon noise in field conditions for military personnel. The noise attenuation was measured with a miniature microphone inserted into the ear canal. The subjects (13) were tested against pink noise and against the noise of explosions and bazooka, mortar, cannon, and howitzer. The attenuation (insertion loss) was 16 to 23 dB for earplugs, 10 to 20 dB for earmuffs, and 24 to 34 dB for the combined use of plugs and muffs. The transfer function of an open ear was 5 to 7 dB when measured as the C-weighted peak level. The combined use of earplugs and earmuffs gave smaller attenuation values than expected. If the limit for the C-weighted peak level is 140 dB for unprotected ears, then protection against low-frequency noise is provided for up to 156 dB by earplugs, up to 150 dB by earmuffs, and up to 165 dB by the combined use of plugs and muffs.

  12. Cosmological flux noise and measured noise power spectra in SQUIDs

    PubMed Central

    Beck, Christian

    2016-01-01

    The understanding of the origin of 1/f magnetic flux noise commonly observed in superconducting devices such as SQUIDs and qubits is still a major unsolved puzzle. Here we discuss the possibility that a significant part of the observed low-frequency flux noise measured in these devices is ultimately seeded by cosmological fluctuations. We consider a theory where a primordial flux noise field left over in unchanged form from an early inflationary or quantum gravity epoch of the universe intrinsically influences the phase difference in SQUIDs and qubits. The perturbation seeds generated by this field can explain in a quantitatively correct way the form and amplitude of measured low-frequency flux noise spectra in SQUID devices if one takes as a source of fluctuations the primordial power spectrum of curvature fluctuations as measured by the Planck collaboration. Our theoretical predictions are in excellent agreement with recent low-frequency flux noise measurements of various experimental groups. Magnetic flux noise, so far mainly considered as a nuisance for electronic devices, may thus contain valuable information about fluctuation spectra in the very early universe. PMID:27320418

  13. Effects of noise upon human information processing

    NASA Technical Reports Server (NTRS)

    Cohen, H. H.; Conrad, D. W.; Obrien, J. F.; Pearson, R. G.

    1974-01-01

    Studies of noise effects upon human information processing are described which investigated whether or not effects of noise upon performance are dependent upon specific characteristics of noise stimulation and their interaction with task conditions. The difficulty of predicting noise effects was emphasized. Arousal theory was considered to have explanatory value in interpreting the findings of all the studies. Performance under noise was found to involve a psychophysiological cost, measured by vasoconstriction response, with the degree of response cost being related to scores on a noise annoyance sensitivity scale. Noise sensitive subjects showed a greater autonomic response under noise stimulation.

  14. Seismometer Self-Noise and Measuring Methods

    USGS Publications Warehouse

    Ringler, Adam; R. Sleeman,; Hutt, Charles R.; Gee, Lind S.

    2014-01-01

    Seismometer self-noise is usually not considered when selecting and using seismic waveform data in scientific research as it is typically assumed that the self-noise is negligibly small compared to seismic signals. However, instrumental noise is part of the noise in any seismic record, and in particular, at frequencies below a few mHz, the instrumental noise has a frequency-dependent character and may dominate the noise. When seismic noise itself is considered as a carrier of information, as in seismic interferometry (e.g., Chaput et al. 2012), it becomes extremely important to estimate the contribution of instrumental noise to the recordings.

  15. Noise and Hearing Loss Prevention

    MedlinePlus

    ... on Facebook Tweet Share Compartir NIOSH Sound Level Meter App Buy Quiet Program Compendium of Hearing Protection ... Publications by Topic and Type Multimedia Sound Level Meter App Search NIOSH Publications Noise and Hearing Loss ...

  16. Human hearing enhanced by noise.

    PubMed

    Zeng, F G; Fu, Q J; Morse, R

    2000-06-30

    Noise was traditionally regarded as a nuisance, which should be minimized if possible. However, recent research has shown that addition of an appropriate amount of noise can actually improve signal detection in a nonlinear system, an effect called stochastic resonance. While stochastic resonance has been described in a variety of physical and biological systems, its functional significance in human sensory systems remains mostly unexplored. Here we report psychophysical data showing that signal detection and discrimination can be enhanced by noise in human subjects whose hearing is evoked by either normal acoustic stimulation or electric stimulation of the auditory nerve or the brainstem. Our results suggest that noise is an integral part of the normal sensory process and should be added to auditory prostheses.

  17. Chain reconfiguration in active noise

    NASA Astrophysics Data System (ADS)

    Samanta, Nairhita; Chakrabarti, Rajarshi

    2016-05-01

    In a typical single molecule experiment, the dynamics of an unfolded protein is studied by determining the reconfiguration time using long-range Förster resonance energy transfer, where the reconfiguration time is the characteristic decay time of the position correlation between two residues of the protein. In this paper we theoretically calculate the reconfiguration time for a single flexible polymer in the presence of active noise. The study suggests that though the mean square displacement grows faster, the chain reconfiguration is always slower in the presence of long-lived active noise with exponential temporal correlation. Similar behavior is observed for a worm-like semi-flexible chain and a Zimm chain. However it is primarily the characteristic correlation time of the active noise and not the strength that controls the increase in the reconfiguration time. In brief, such active noise makes the polymer move faster but the correlation loss between the monomers becomes slow.

  18. Rotor-vortex interaction noise

    NASA Technical Reports Server (NTRS)

    Schlinker, R. H.; Amiet, R. K.

    1983-01-01

    A theoretical and experimental study was conducted to develop a validated first principles analysis for predicting noise generated by helicopter main-rotor shed vortices interacting with the tail rotor. The generalized prediction procedure requires a knowledge of the incident vortex velocity field, rotor geometry, and rotor operating conditions. The analysis includes compressibility effects, chordwise and spanwise noncompactness, and treats oblique intersections with the blade planform. Assessment of the theory involved conducting a model rotor experiment which isolated the blade-vortex interaction noise from other rotor noise mechanisms. An isolated tip vortex, generated by an upstream semispan airfoil, was convected into the model tail rotor. Acoustic spectra, pressure signatures, and directivity were measured. Since assessment of the acoustic prediction required a knowledge of the vortex properties, blade-vortes intersection angle, intersection station, vortex stength, and vortex core radius were documented. Ingestion of the vortex by the rotor was experimentally observed to generate harmonic noise and impulsive waveforms.

  19. Analytical Lift Fan Noise Study

    NASA Technical Reports Server (NTRS)

    Rao, G. V. R.; Chu, W. T.; Digumarthi, R. V.

    1973-01-01

    Based on reasonable estimates of flow conditions occurring in an axial fan, acoustic radiation from various noise sources is evaluated. Results of computations on two specific fans are presented, and relative significance of the various sources is examined.

  20. Noise in Nonlinear Dynamical Systems

    NASA Astrophysics Data System (ADS)

    Moss, Frank; McClintock, P. V. E.

    2009-08-01

    List of contributors; Preface; Introduction to volume three; 1. The effects of coloured quadratic noise on a turbulent transition in liquid He II J. T. Tough; 2. Electrohydrodynamic instability of nematic liquid crystals: growth process and influence of noise S. Kai; 3. Suppression of electrohydrodynamic instabilities by external noise Helmut R. Brand; 4. Coloured noise in dye laser fluctuations R. Roy, A. W. Yu and S. Zhu; 5. Noisy dynamics in optically bistable systems E. Arimondo, D. Hennequin and P. Glorieux; 6. Use of an electronic model as a guideline in experiments on transient optical bistability W. Lange; 7. Computer experiments in nonlinear stochastic physics Riccardo Mannella; 8. Analogue simulations of stochastic processes by means of minimum component electronic devices Leone Fronzoni; 9. Analogue techniques for the study of problems in stochastic nonlinear dynamics P. V. E. McClintock and Frank Moss; Index.

  1. Simulation optimizes noise jammer design

    NASA Astrophysics Data System (ADS)

    Knorr, J. B.; Karantanas, D. T.

    1985-05-01

    Direct noise amplification (DINA) and pseudo noise (modulated carrier - MC) are the two techniques used to approximate white Gaussian radar jamming noise. DINA is seldom employed because of its inefficient demands on the microwave amplifier. MC features modulation of a carrier signal to induce a Gaussian waveform at the victim receiver. The MC method attains a high efficiency with a carcinotron power oscillator, provided the Gaussian noise quality (GNQ), which is a function of the modulating signal parameters, is good. Results from a mainframe computer simulation indicate that the jammer bandwidth needs to be at least as wide as the victim bandwidth. The GNQ decreases with nearness to the edge of the jamming band but is independent of the jamer bandwidth.

  2. Atmospheric noise mitigation for Loran

    NASA Astrophysics Data System (ADS)

    Boyce, C. O. Lee, Jr.

    While aircraft users increasingly rely on the Global Positioning System (GPS) for navigation, the received signal strength from these distant satellites is low and hence may easily be jammed. Of the alternative systems available to provide aircraft with a backup to GPS for non-precision approach (NPA), Loran promises to be an exceptional candidate since its signal is present over the continental United States (CONUS). Loran, a low-frequency hyperbolic radio-navigation system, provides positioning with quarter nautical mile accuracy, 95% of the time. Since it was not originally designed for aircraft navigation, the system requires upgrades to both the transmitters and user receivers to meet NPA requirements. Furthermore, to be viable, Loran's coverage area, defined as where it meets the NPA requirements, must be across most of CONUS. Impeding its success is Loran's susceptibility to lightning and other atmospheric noise. Determining Loran's coverage requires the estimation of atmospheric noise and the processing gain or credit for noise reduction due to non-linear processing techniques within a typical receiver. The traditional method uses the standard atmospheric noise model from the International Telecommunications Union (ITU), and estimates the processing gain as a constant. While easy to implement, such an analysis produces overly conservative results and, therefore, a poor estimate of coverage area. This dissertation presents a new method for predicting coverage by extending the ITU model and by demonstrating empirically that a lower bound on atmospheric noise impulsivity is proportional to the noise strength. Since it is well known that the gain in signal-to-noise ratio (SNR) in a receiver produced by non-linear signal processing is proportional to the noise impulsivity, then the correlation of noise impulsivity to noise strength implies that the processing gain is also proportional to noise strength and is not simply constant as previously predicted. The new

  3. Removal of Noise from Noise-Degraded Speech Signals. Panel on Removal of Noise from a Speech/Noise Signal

    DTIC Science & Technology

    1989-06-01

    listeners with a sensorineural hearing loss . The largest improvements in intelligibility scores were observed with iow-frequency noise (600 to 800 Hz) and...spectrum. Another study of the Zeta Noise Blocker was carried out by Wolinsky (1986) using 18 subjects with moderate to severe sensorineural hearing loss ...speech-enhancement devices for hearing -impaired people was reviewed. Evaluation techniques were reviewed to determine their suitability, particularly for

  4. Emissions and Noise Pervasive Panel

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda; Lee, Chi

    2008-01-01

    Objectives include: Provide interagency coordination of technology development, aimed at engine noise reduction. a) Provide recommendations to the Steering Committee on potential areas of interagency technology collaboration to maximize the use of government investments in noise reduction. b) Serve as a forum for information and technology exchange in order to coordinate gas turbine engine environmental strategies and policies among the member agencies and industry; c) Coordinate activities across panel representatives; and d) Communicate progress to VAATE steering committee.

  5. GE MOD-1 noise study

    NASA Technical Reports Server (NTRS)

    Wells, R. J.

    1981-01-01

    Noise studies of the MOD-1 Wind Turbine Generator are summarized, and a simple mathematical noise is presented which is adequate to correlate the sound levels found near the machine. A simple acoustic measure is suggested for use in evaluating far field sound levels. Use of this measure as input to a currently available sound complaint prediction program is discussed. Results of a recent statistical survey relative to the far field variation of this acoustic measure because of atmospheric effects are described.

  6. Health consequences of aircraft noise.

    PubMed

    Kaltenbach, Martin; Maschke, Christian; Klinke, Rainer

    2008-08-01

    The ever-increasing level of air traffic means that any medical evaluation of its effects must be based on recent data. Selective literature review of epidemiological studies from 2000 to 2007 regarding the illnesses, annoyance, and learning disorders resulting from aircraft noise. In residential areas, outdoor aircraft noise-induced equivalent noise levels of 60 dB(A) in the daytime and 45 dB(A) at night are associated with an increased incidence of hypertension. There is a dose-response relationship between aircraft noise and the occurrence of arterial hypertension. The prescription frequency of blood pressure-lowering medications is associated dose-dependently with aircraft noise from a level of about 45 dB(A). Around 25% of the population are greatly annoyed by exposure to noise of 55 dB(A) during the daytime. Exposure to 50 dB(A) in the daytime (outside) is associated with relevant learning difficulties in schoolchildren. Based on recent epidemiological studies, outdoor noise limits of 60 dB(A) in the daytime and 50 dB(A) at night can be recommended on grounds of health protection. Hence, maximum values of 55 dB(A) for the day and 45 dB(A) for the night should be aimed for in order to protect the more sensitive segments of the population such as children, the elderly, and the chronically ill. These values are 5 to 10 dB(A) lower than those specified by the German federal law on aircraft noise and in the report "synopsis" commissioned by the company that runs Frankfurt airport (Fraport).

  7. Noise induced phenomena in combustion

    NASA Astrophysics Data System (ADS)

    Liu, Hongliang

    Quantitative models of combustion usually consist of systems of deterministic differential equations. However, there are reasons to suspect that noise may have a significant influence. In this thesis, our primary objective is to study the effect of noise on measurable quantities in the combustion process. Our first study involves combustion in a homogeneous gas. With a one step reaction model, we analytically estimate the requirements under which noise is important to create significant differences. Our simulation shows that a bi-modality phenomenon appears when appropriate parameters are applied, which agrees with our analytical result. Our second study involves steady planar flames. We use a relatively complete chemical model of the H2/air reaction system, which contains all eight reactive species (H2, O2, H, O, OH, H2O, HO2, H2O2) and N2. Our mathematical model for this system is a reacting flow model. We derive noise terms related to transport processes by a method advocated by Landau & Lifshitz, and we also derive noise terms related to chemical reactions. We develop a code to simulate this system. The numerical implementation relies on a good Riemann solver, suitable initial and boundary conditions, and so on. We also implement a code on a continuation method, which not only can be used to study approximate properties of laminar flames under deterministic governing equations, but also eliminates the difficulty of providing a suitable initial condition for governing equations with noise. With numerical experiments, we find the difference of flame speed exist when the noise is turned on or off although it is small when compared with the influence of other parameters, for example, the equivalence ratio. It will be a starting point for further studies to include noise in combustion.

  8. [Does aircraft noise affect health?].

    PubMed

    Müller, R

    1980-06-01

    A field study of the Institute of Behavioral Sciences at the Federal Institute of Technology, Zürich, has verified that aircraft noise effects severe annoyance and inconvenience of airport area residents. This causes irritation, which manifests itself in numerous negative intentions, attitudes and opinions, in actions and meaures and even in psychosomatic disorders. Moreover noise exerts influence on vegetative reactions of persons performing different activities, mostly if they have to concentrate on a task.

  9. Physically Damped Noise Canceling Hydrophone

    DTIC Science & Technology

    2016-06-24

    Description of the Prior Art [0004] An acoustic hydrophone can transfer underwater pressure waves to electrical energy. As a result, an output charge...frequencies in the range of the generated noise. [0006] In the prior art, the design of a noise cancelling hydrophone was originally developed by Kahn...includes two types of piezoelectric transducers coupled together. One transducer maintains voids and is sensitive to hydrostatic acoustic signals. The

  10. Community response to aircraft noise.

    NASA Technical Reports Server (NTRS)

    Whitten, R. P.

    1972-01-01

    Organized community resistance to any plan of airport development has become so intense that noise exposure is a primary consideration in plans for new airports, runway extensions, and the introduction of new types of aircraft. Approaches for evaluating the amount of aircraft noise and the annoyance produced by it are discussed. The sociometric studies considered show that fear of crash is the strongest single variable.

  11. Anthropogenic noise changes arthropod abundances.

    PubMed

    Bunkley, Jessie P; McClure, Christopher J W; Kawahara, Akito Y; Francis, Clinton D; Barber, Jesse R

    2017-05-01

    Anthropogenic noise is a widespread and growing form of sensory pollution associated with the expansion of human infrastructure. One specific source of constant and intense noise is that produced by compressors used for the extraction and transportation of natural gas. Terrestrial arthropods play a central role in many ecosystems, and given that numerous species rely upon airborne sounds and substrate-borne vibrations in their life histories, we predicted that increased background sound levels or the presence of compressor noise would influence their distributions. In the second largest natural gas field in the United States (San Juan Basin, New Mexico, USA), we assessed differences in the abundances of terrestrial arthropod families and community structure as a function of compressor noise and background sound level. Using pitfall traps, we simultaneously sampled five sites adjacent to well pads that possessed operating compressors, and five alternate, quieter well pad sites that lacked compressors, but were otherwise similar. We found a negative association between sites with compressor noise or higher levels of background sound and the abundance of five arthropod families and one genus, a positive relationship between loud sites and the abundance of one family, and no relationship between noise level or compressor presence and abundance for six families and two genera. Despite these changes, we found no evidence of community turnover as a function of background sound level or site type (compressor and noncompressor). Our results indicate that anthropogenic noise differentially affects the abundances of some arthropod families. These preliminary findings point to a need to determine the direct and indirect mechanisms driving these observed responses. Given the diverse and important ecological functions provided by arthropods, changes in abundances could have ecological implications. Therefore, we recommend the consideration of arthropods in the environmental

  12. Hydrodynamical noise and Gubser flow

    NASA Astrophysics Data System (ADS)

    Yan, Li; Grönqvist, Hanna

    2016-03-01

    Hydrodynamical noise is introduced on top of Gubser's analytical solution to viscous hydrodynamics. With respect to the ultra-central collision events of Pb-Pb, p-Pb and p-p at the LHC energies, we solve the evolution of noisy fluid systems and calculate the radial flow velocity correlations. We show that the absolute amplitude of the hydrodynamical noise is determined by the multiplicity of the collision event. The evolution of azimuthal anisotropies, which is related to the generation of harmonic flow, receives finite enhancements from hydrodynamical noise. Although it is strongest in the p-p systems, the effect of hydrodynamical noise on flow harmonics is found to be negligible, especially in the ultra-central Pb-Pb collisions. For the short-range correlations, hydrodynamical noise contributes to the formation of a near-side peak on top of the correlation structure originated from initial state fluctuations. The shape of the peak is affected by the strength of hydrodynamical noise, whose height and width grow from the Pb-Pb system to the p-Pb and p-p systems.

  13. Blue-noise multitone dithering.

    PubMed

    Bacca Rodriguez, J; Arce, G R; Lau, D L

    2008-08-01

    The introduction of the blue-noise spectra-high-frequency white noise with minimal energy at low frequencies-has had a profound impact on digital halftoning for binary display devices, such as inkjet printers, because it represents an optimal distribution of black and white pixels producing the illusion of a given shade of gray. The blue-noise model, however, does not directly translate to printing with multiple ink intensities. New multilevel printing and display technologies require the development of corresponding quantization algorithms for continuous tone images, namely multitoning. In order to define an optimal distribution of multitone pixels, this paper develops the theory and design of multitone, blue-noise dithering. Here, arbitrary multitone dot patterns are modeled as a layered superposition of stack-constrained binary patterns. Multitone blue-noise exhibits minimum energy at low frequencies and a staircase-like, ascending, spectral pattern at higher frequencies. The optimum spectral profile is described by a set of principal frequencies and amplitudes whose calculation requires the definition of a spectral coherence structure governing the interaction between patterns of dots of different intensities. Efficient algorithms for the generation of multitone, blue-noise dither patterns are also introduced.

  14. Blast noise impacts on sleep

    NASA Astrophysics Data System (ADS)

    Nykaza, Edward T.; Pater, Larry L.

    2005-04-01

    Firing large guns during the hours of darkness is essential to combat readiness for the military. At the same time most people are particularly sensitive to noise when sleeping or trying to fall asleep. Laboratory studies done by Griefahn [J. Sound and Vib. 128, 109-119 (1989)] and Luz [see Luz et al., ERDC/CERL, TR-04-26 (2004)] suggest that a time period at night may exist where people are more tolerant to large weapon impulse noise (blast noise) and therefore, are less likely to be awakened from noise events. In the fall of 2004, a field study was conducted around a military installation to determine if such a time period(s) exists. Noise monitors were set up inside and outside of residents homes to record noise levels from live military training activities and actimeters were worn by participants sleeping their natural environment to measure sleep disturbance and awakening. The method and results of this study will be presented. [Work supported by US Army Engineer Research and Development Center CERL.

  15. Influence of the seismic noise characteristics on noise correlations

    NASA Astrophysics Data System (ADS)

    Krüger, F.; Pedersen, H. A.

    2005-12-01

    Cross-correlating seismic noise to obtain the Green function between two seismic sensors is a promising new technique for crustal tomography. We use data from 38 temporary broadband sensors in Finland to study how the nature of the seismic noise influences noise correlations. The study area is particularly well adapted for this study as the lateral variations of surface wave velocities are very small. We apply a processing technique which makes it possible to extract broadband signals between 2s and 35s period without applying any signal clipping. The extracted Green's functions are symmetrical at low and high-frequencies, but are strongly direction dependent around the two microseismic peaks (at approximately 15s and 8s). For these periods the signal amplitude varies by a factor of 90 between different azimuths. The maximum amplitudes are obtained for east-west profiles for the first microseismic peak and for east-west and north-south profiles for the second microseismic peak. The phase velocities when defined are however correct for all azimuths when all the traces in a given direction are used for slant stack. The group velocities calculated on individual traces do on the contrary vary strongly with azimuth, with a 1/cos dependence. We also apply f-k analysis on data from the NORSAR (Norway) and Gräfenberg (Germany) arrays as well as a small-aperture array in Finland to constrain the arrival directions of the coherent part of the noise. The microseismic noise generation is located west of the array for the first microseismic peak and west and north of the array for the second microseismic peak, in excellent agreement with the noise correlations. The f-k analysis also confirms that the noise generators are more randomly distributed for the long period (25s-50s) and short period (2s-4s) part of the noise. We conclude that in some frequency bands the noise in the study area is dominated by plane energy wavefronts, with strong phase perturbations. The profile

  16. 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.

  17. Noise measurements on the helicopter BK 117 design. Weighted noise levels and influence of airspeed

    NASA Astrophysics Data System (ADS)

    Splettstoesser, Wolf R.; Anders, Klaus P.; Spiegel, Karl-Heinz

    1986-11-01

    Noise measurements on the prototype helicopter BK 117 were performed in strict compliance with the proposed international Civil Aviation Organization regulations for noise certification of helicopters. Measurement procedure, noise data acquisition, analysis and reduction as well as applied correction procedures are described. Effective perceived noise levels (EPNL) and other noise descriptors were evaluated and related to the proposed noise limits. Additional level flyover tests with variable airspeed were conducted to investigate the resulting effect on the EPNL and other noise measures.

  18. The subjective importance of noise spectral content

    NASA Astrophysics Data System (ADS)

    Baxter, Donald; Phillips, Jonathan; Denman, Hugh

    2014-01-01

    This paper presents secondary Standard Quality Scale (SQS2) rankings in overall quality JNDs for a subjective analysis of the 3 axes of noise, amplitude, spectral content, and noise type, based on the ISO 20462 softcopy ruler protocol. For the initial pilot study, a Python noise simulation model was created to generate the matrix of noise masks for the softcopy ruler base images with different levels of noise, different low pass filter noise bandwidths and different band pass filter center frequencies, and 3 different types of noise: luma only, chroma only, and luma and chroma combined. Based on the lessons learned, the full subjective experiment, involving 27 observers from Google, NVIDIA and STMicroelectronics was modified to incorporate a wider set of base image scenes, and the removal of band pass filtered noise masks to ease observer fatigue. Good correlation was observed with the Aptina subjective noise study. The absence of tone mapping in the noise simulation model visibly reduced the contrast at high levels of noise, due to the clipping of the high levels of noise near black and white. Under the 34-inch viewing distance, no significant difference was found between the luma only noise masks and the combined luma and chroma noise masks. This was not the intuitive expectation. Two of the base images with large uniform areas, `restaurant' and `no parking', were found to be consistently more sensitive to noise than the texture rich scenes. Two key conclusions are (1) there are fundamentally different sensitivities to noise on a flat patch versus noise in real images and (2) magnification of an image accentuates visual noise in a way that is non-representative of typical noise reduction algorithms generating the same output frequency. Analysis of our experimental noise masks applied to a synthetic Macbeth ColorChecker Chart confirmed the color-dependent nature of the visibility of luma and chroma noise.

  19. Noise. Ag Ed Environmental Education Series.

    ERIC Educational Resources Information Center

    Tulloch, Rodney W.

    Noise is the subject of the student resource unit to be used with high school vocational agriculture students. The nature of noise as a phenomenon and as a problem is clarified. Sources of noise pollution and the decibel levels they produce are described. Among the effects of noise pollution discussed are hearing loss, annoyance, and accidental…

  20. 75 FR 44046 - Noise Exposure Map Acceptance

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-27

    ... the precise relationship of specific properties to noise exposure contours depicted on a noise... contours, or in interpreting the noise exposure maps to resolve questions concerning, for example, which.... Therefore, the responsibility for the detailed overlaying of noise exposure contours onto the map...

  1. 23 CFR 772.19 - Construction noise.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 23 Highways 1 2012-04-01 2012-04-01 false Construction noise. 772.19 Section 772.19 Highways... ABATEMENT OF HIGHWAY TRAFFIC NOISE AND CONSTRUCTION NOISE § 772.19 Construction noise. For all Type I and II... construction of the project. The identification is to be performed during the project development studies....

  2. 32 CFR 989.32 - Noise.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 32 National Defense 6 2013-07-01 2013-07-01 false Noise. 989.32 Section 989.32 National Defense... ANALYSIS PROCESS (EIAP) § 989.32 Noise. Aircraft noise data files used for analysis during EIAP will be... System for Aircraft Noise for military training routes and military operating areas. Guidance on...

  3. 32 CFR 989.32 - Noise.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 32 National Defense 6 2011-07-01 2011-07-01 false Noise. 989.32 Section 989.32 National Defense... ANALYSIS PROCESS (EIAP) § 989.32 Noise. Aircraft noise data files used for analysis during EIAP will be... System for Aircraft Noise for military training routes and military operating areas. Guidance on...

  4. 32 CFR 989.32 - Noise.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 32 National Defense 6 2012-07-01 2012-07-01 false Noise. 989.32 Section 989.32 National Defense... ANALYSIS PROCESS (EIAP) § 989.32 Noise. Aircraft noise data files used for analysis during EIAP will be... System for Aircraft Noise for military training routes and military operating areas. Guidance on...

  5. 32 CFR 989.32 - Noise.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 32 National Defense 6 2014-07-01 2014-07-01 false Noise. 989.32 Section 989.32 National Defense... ANALYSIS PROCESS (EIAP) § 989.32 Noise. Aircraft noise data files used for analysis during EIAP will be... System for Aircraft Noise for military training routes and military operating areas. Guidance on...

  6. 32 CFR 989.32 - Noise.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 6 2010-07-01 2010-07-01 false Noise. 989.32 Section 989.32 National Defense... ANALYSIS PROCESS (EIAP) § 989.32 Noise. Aircraft noise data files used for analysis during EIAP will be... System for Aircraft Noise for military training routes and military operating areas. Guidance on...

  7. 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.

  8. Helicopter noise certification - Past-present-future

    NASA Astrophysics Data System (ADS)

    Leverton, John W.

    1992-09-01

    A development history and a development trends evaluation are presented for helicopter noise-certification rules. It is noted that the Committee for Aircraft Noise 7 limits effectively constitute a cap on helicopter noise levels; a 9 dB total reduction in noise limits appears to be a desirable goal for variants of current helicopter designs. The certification scheme should allow noise-abatement (and other, similar) procedures to be exploited; this could result in the public's experience of lower noise levels, and establish a better groundwork for future noise reductions.

  9. Progress in rotor broadband noise research

    NASA Technical Reports Server (NTRS)

    Brooks, T. F.; Schlinker, R. H.

    1983-01-01

    The current status of research on various rotor broadband noise sources is reviewed. Theoretical modeling techniques which appear to have the most promise in the development of successful noise prediction capabilities are emphasized. The types of noise considered include: turbulence ingestion noise, blade self-noise due to turbulence passing the trailing edge, blade self-noise due to separated flow, and blade self-noise due to vortex shedding. Comparisons with experimental results are given, and present theoretical and experimental limitations are delineated to help identify areas of needed research.

  10. Helicopter noise regulations: An industry perspective

    NASA Technical Reports Server (NTRS)

    Wagner, R. A.

    1978-01-01

    A review of helicopter noise measurement programs and noise reduction/economic studies of FAA is given along with a critique of a study which addresses the economic impact of noise reduction on helicopter noise. Modification of several helicopters to reduce noise and demonstrate the economic impact of the application of the current state-of-the-art technology is discussed. Specific helicopters described include Boeing Vertol 347 Helicopter, Hughes OH-6 Helicopter, and Hughes 269C Helicopter. Other topics covered include: (1) noise trends and possible noise limits; (2) accuracy of helicopter noise prediction techniques; (3) limited change possibilities of derivatives; and (4) rotor impulsive noise. The unique operational capabilities of helicopters and the implications relative to noise regulations and certification are discussed.

  11. Underwater noise modelling for environmental impact assessment

    SciTech Connect

    Farcas, Adrian; Thompson, Paul M.; Merchant, Nathan D.

    2016-02-15

    Assessment of underwater noise is increasingly required by regulators of development projects in marine and freshwater habitats, and noise pollution can be a constraining factor in the consenting process. Noise levels arising from the proposed activity are modelled and the potential impact on species of interest within the affected area is then evaluated. Although there is considerable uncertainty in the relationship between noise levels and impacts on aquatic species, the science underlying noise modelling is well understood. Nevertheless, many environmental impact assessments (EIAs) do not reflect best practice, and stakeholders and decision makers in the EIA process are often unfamiliar with the concepts and terminology that are integral to interpreting noise exposure predictions. In this paper, we review the process of underwater noise modelling and explore the factors affecting predictions of noise exposure. Finally, we illustrate the consequences of errors and uncertainties in noise modelling, and discuss future research needs to reduce uncertainty in noise assessments.

  12. Health Effects of Noise Exposure in Children.

    PubMed

    Stansfeld, Stephen; Clark, Charlotte

    2015-06-01

    Environmental noise exposure, such as road traffic noise and aircraft noise, is associated with a range of health outcomes in children. Children demonstrate annoyance responses to noise, and noise is also related to lower well-being and stress responses, such as increased levels of adrenaline and noradrenaline. Noise does not cause more serious mental health problems, but there is growing evidence for an association with increased hyperactivity symptoms. Studies also suggest that noise might cause changes in cardiovascular functioning, and there is some limited evidence for an effect on low birth weight. There is robust evidence for an effect of school noise exposure on children's cognitive skills such as reading and memory, as well as on standardised academic test scores. Environmental noise does not usually reach levels that are likely to affect children's hearing; however, increasing use of personal electronic devices may leave some children exposed to harmful levels of noise.

  13. Airport noise impact reduction through operations

    NASA Technical Reports Server (NTRS)

    Deloach, R.

    1981-01-01

    The airport-noise levels and annoyance model (ALAMO) developed at NASA Langley Research Center is comprised of a system of computer programs which is capable of quantifying airport community noise impact in terms of noise level, population distribution, and human subjective response to noise. The ALAMO can be used to compare the noise impact of an airport's current operating scenario with the noise impact which would result from some proposed change in airport operations. The relative effectiveness of number of noise-impact reduction alternatives is assessed for a major midwest airport. Significant reductions in noise impact are predicted for certain noise abatement strategies while others are shown to result in relatively little noise relief.

  14. 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.

  15. Effects of road traffic background noise on judgments of individual airplane noises. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Powell, C. A.

    1979-01-01

    Two laboratory experiments were conducted to investigate the effects of road-traffic background noise on judgments of individual airplane flyover noises. In the first experiment, 27 subjects judged a set of 16 airplane flyover noises in the presence of traffic-noise sessions of 30-min duration consisting of the combinations of 3 traffic-noise types and 3 noise levels. In the second experiment, 24 subjects judged the same airplane flyover noises in the presence of traffic-noise sessions of 10-min duration consisting of the combinations of 2 traffic-noise types and 4 noise levels. In both experiments the airplane noises were judged less annoying in the presence of high traffic-noise levels than in the presence of low traffic-noise levels.

  16. Towards thermal noise free optomechanics

    NASA Astrophysics Data System (ADS)

    Page, Michael A.; Zhao, Chunnong; Blair, David G.; Ju, Li; Ma, Yiqiu; Pan, Huang-Wei; Chao, Shiuh; Mitrofanov, Valery P.; Sadeghian, Hamed

    2016-11-01

    Thermal noise generally greatly exceeds quantum noise in optomechanical devices unless the mechanical frequency is very high or the thermodynamic temperature is very low. This paper addresses the design concept for a novel optomechanical device capable of ultrahigh quality factors in the audio frequency band with negligible thermal noise. The proposed system consists of a minimally supported millimeter scale pendulum mounted in a double end-mirror sloshing cavity that is topologically equivalent to a membrane-in-the-middle cavity. The radiation pressure inside the high-finesse cavity allows for high optical stiffness, cancellation of terms which lead to unwanted negative damping and suppression of quantum radiation pressure noise. We solve the optical spring dynamics of the system using the Hamiltonian, find the noise spectral density and show that stable optical trapping is possible. We also assess various loss mechanisms, one of the most important being the acceleration loss due to the optical spring. We show that practical devices, starting from a centre-of-mass pendulum frequency of 0.1 Hz, could achieve a maximum quality factor of (1014) with optical spring stiffened frequency 1-10 kHz. Small resonators of mass 1 ≤ft(μ \\right) g or less could achieve a Q-factor of (1011) at a frequency of 100 kHz. Applications for such devices include white light cavities for improvement of gravitational wave detectors, or sensors able to operate near the quantum limit.

  17. Multiple pure tone noise prediction

    NASA Astrophysics Data System (ADS)

    Han, Fei; Sharma, Anupam; Paliath, Umesh; Shieh, Chingwei

    2014-12-01

    This paper presents a fully numerical method for predicting multiple pure tones, also known as “Buzzsaw” noise. It consists of three steps that account for noise source generation, nonlinear acoustic propagation with hard as well as lined walls inside the nacelle, and linear acoustic propagation outside the engine. Noise generation is modeled by steady, part-annulus computational fluid dynamics (CFD) simulations. A linear superposition algorithm is used to construct full-annulus shock/pressure pattern just upstream of the fan from part-annulus CFD results. Nonlinear wave propagation is carried out inside the duct using a pseudo-two-dimensional solution of Burgers' equation. Scattering from nacelle lip as well as radiation to farfield is performed using the commercial solver ACTRAN/TM. The proposed prediction process is verified by comparing against full-annulus CFD simulations as well as against static engine test data for a typical high bypass ratio aircraft engine with hardwall as well as lined inlets. Comparisons are drawn against nacelle unsteady pressure transducer measurements at two axial locations as well as against near- and far-field microphone array measurements outside the duct. This is the first fully numerical approach (no experimental or empirical input is required) to predict multiple pure tone noise generation, in-duct propagation and far-field radiation. It uses measured blade coordinates to calculate MPT noise.

  18. Quantum learning robust against noise

    NASA Astrophysics Data System (ADS)

    Cross, Andrew W.; Smith, Graeme; Smolin, John A.

    2015-07-01

    Noise is often regarded as anathema to quantum computation, but in some settings it can be an unlikely ally. We consider the problem of learning the class of n -bit parity functions by making queries to a quantum example oracle. In the absence of noise, quantum and classical parity learning are easy and almost equally powerful, both information-theoretically and computationally. We show that in the presence of noise this story changes dramatically. Indeed, the classical learning problem is believed to be intractable, while the quantum version remains efficient. Depolarizing the qubits at the oracle's output at any constant nonzero rate does not increase the computational (or query) complexity of quantum learning more than logarithmically. However, the problem of learning from corresponding classical examples is the learning parity with noise problem, for which the best known algorithms have superpolynomial complexity. This creates the possibility of observing a quantum advantage with a few hundred noisy qubits. The presence of noise is essential for creating this quantum-classical separation.

  19. Quantum learning robust to noise

    NASA Astrophysics Data System (ADS)

    Smolin, John; Cross, Andrew; Smith, Graeme

    2015-03-01

    Noise is often regarded as anathema to quantum computation, but in some settings it can be an unlikely ally. We consider the problem of learning the class of n-bit parity functions by making queries to a quantum example oracle. In the absence of noise, quantum and classical parity learning are easy and almost equally powerful, both information-theoretically and computationally. We show that in the presence of noise this story changes dramatically. Indeed, the classical learning problem is believed to be intractable, while the quantum version remains efficient. Depolarizing the qubits at the oracle's output at any constant nonzero rate does not increase the computational (or query) complexity of quantum learning more than logarithmically. However, the problem of learning from corresponding classical examples is the Learning Parity with Noise (LPN) problem, for which the best known algorithms have superpolynomial complexity. This creates the possibility of observing a quantum advantage with a few hundred noisy qubits. The presence of noise is essential for creating this quantum-classical separation. AWC and JAS acknowledge support from IARPA under Contract W911NF-10-1-0324.

  20. Aircraft en route noise annoyance

    NASA Technical Reports Server (NTRS)

    Mccurdy, David A.

    1990-01-01

    Results are reported from a laboratory experiment conducted in order to quantify the annoyance experienced by people on the ground in response to en route noise (ERN) generated by aircraft at cruise conditions. Objectives included the comparison of annoyance responses to ERN with the annoyance responses to takeoff and landing noise; the comparison of the annoyance responses to advanced turboprop aircraft ERN with those of the turbofan ERN; and also the ability of aircraft noise measurement procedures and corrections to predict annoyance to ERN. Tests were conducted at the Langley Acoustics Research Laboratory on 32 human subjects selected at random. Subjects judged the annoyance level of 24 Propfan Test Assessment advanced turboprop ERN stimuli, 18 conventional turbofan ERN stimuli, and 60 conventional turboprop and turbofan takeoff and landing noise stimuli. Analysis of resulting data compared annoyance responses to different aircraft types and operations, examined the ability of current noise measurement and correction procedures to predict annoyance ERN, and calculated optimum duration correction magnitudes for ERN.

  1. Estimating the coherence of noise

    NASA Astrophysics Data System (ADS)

    Wallman, Joel

    To harness the advantages of quantum information processing, quantum systems have to be controlled to within some maximum threshold error. Certifying whether the error is below the threshold is possible by performing full quantum process tomography, however, quantum process tomography is inefficient in the number of qubits and is sensitive to state-preparation and measurement errors (SPAM). Randomized benchmarking has been developed as an efficient method for estimating the average infidelity of noise to the identity. However, the worst-case error, as quantified by the diamond distance from the identity, can be more relevant to determining whether an experimental implementation is at the threshold for fault-tolerant quantum computation. The best possible bound on the worst-case error (without further assumptions on the noise) scales as the square root of the infidelity and can be orders of magnitude greater than the reported average error. We define a new quantification of the coherence of a general noise channel, the unitarity, and show that it can be estimated using an efficient protocol that is robust to SPAM. Furthermore, we also show how the unitarity can be used with the infidelity obtained from randomized benchmarking to obtain improved estimates of the diamond distance and to efficiently determine whether experimental noise is close to stochastic Pauli noise.

  2. Subsonic and transonic propeller noise

    NASA Astrophysics Data System (ADS)

    Lewy, S.; Gounet, H.

    Models for the noise levels from propellers are discussed, with results compared to in-flight measurements. Methods originally applied to noise from light aircraft are modified and extended to high speed passenger aircraft. Noise emitted from propellers has three components: a monopolar emission due to the air displaced by a blade; a bipolar form from average and fluctuating forces exerted by the blades; and a quadripolar component produced by deformation of the streamlines around the blade profile and defined by the Lighthill tensor. The latter is not a factor in the subsonic regime and can be neglected. Attention is given to a formalism which accounts for the sound level along each band, the frequency harmonics at each blade passage, the number of blades, and the rotation rate. The measured directivities of the two components are described. It is found that the radiated noise levels can be reduced in slow aircraft by lowering the peripheral velocity while keeping the same power with more blades. Calculations including the quadripolar term are necessary for modeling noise levels in transonic propellers.

  3. Supersonic jet shock noise reduction

    NASA Technical Reports Server (NTRS)

    Stone, J. R.

    1984-01-01

    Shock-cell noise is identified to be a potentially significant problem for advanced supersonic aircraft at takeoff. Therefore NASA conducted fundamental studies of the phenomena involved and model-scale experiments aimed at developing means of noise reduction. The results of a series of studies conducted to determine means by which supersonic jet shock noise can be reduced to acceptable levels for advanced supersonic cruise aircraft are reviewed. Theoretical studies were conducted on the shock associated noise of supersonic jets from convergent-divergent (C-D) nozzles. Laboratory studies were conducted on the influence of narrowband shock screech on broadband noise and on means of screech reduction. The usefulness of C-D nozzle passages was investigated at model scale for single-stream and dual-stream nozzles. The effect of off-design pressure ratio was determined under static and simulated flight conditions for jet temperatures up to 960 K. Annular and coannular flow passages with center plugs and multi-element suppressor nozzles were evaluated, and the effect of plug tip geometry was established. In addition to the far-field acoustic data, mean and turbulent velocity distributions were measured with a laser velocimeter, and shadowgraph images of the flow field were obtained.

  4. Modularity, noise, and natural selection.

    PubMed

    Marroig, Gabriel; Melo, Diogo A R; Garcia, Guilherme

    2012-05-01

    Most biological systems are formed by component parts that are to some degree interrelated. Groups of parts that are more associated among themselves and are relatively autonomous from others are called modules. One of the consequences of modularity is that biological systems usually present an unequal distribution of the genetic variation among traits. Estimating the covariance matrix that describes these systems is a difficult problem due to a number of factors such as poor sample sizes and measurement errors. We show that this problem will be exacerbated whenever matrix inversion is required, as in directional selection reconstruction analysis. We explore the consequences of varying degrees of modularity and signal-to-noise ratio on selection reconstruction. We then present and test the efficiency of available methods for controlling noise in matrix estimates. In our simulations, controlling matrices for noise vastly improves the reconstruction of selection gradients. We also perform an analysis of selection gradients reconstruction over a New World Monkeys skull database to illustrate the impact of noise on such analyses. Noise-controlled estimates render far more plausible interpretations that are in full agreement with previous results. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

  5. [Sleep disturbance caused by noise].

    PubMed

    Vallet, M

    1982-05-01

    This contribution is a state-of-the-art of recent knowledge regarding effects from environmental noise on sleep and proposes acoustic thresholds likely to help public authorities in setting up regulations. It recalls physiological sleep aspects and the cyclic organization of the various stages; then it examines noise effects, principally those arising from road traffic, planes and trains. Such effects are firstly considered as changes in sleep organization during night. It is noted that laboratory and home experiments lead to the same conclusions: duration of deep sleep is appreciably reduced for younger people, while the dream phase is disturbed for older people. These disturbances are associated with an average energetic level Leq. Then partial effects are investigated, either electro-encephalographic or cardiac; these effects are more especially associated with isolated acoustic phenomena and determined from the noise peak level. Other variables, e.g. back noise, phenomena number per period, interval between two noises, have an effect on probability of a local phenomenon which can be connected to a given peak level. The conclusion is that two acoustic values must be retained for considering sleep disturbances: the first one is the energetic level inside the room, with a comfort threshold of 35 dB(A) by night, and the second one is the lowest peak level which should not exceed 50 dB(A).

  6. Measurement of noise from toys

    NASA Astrophysics Data System (ADS)

    Altkorn, Robert; Milkovich, Scott M.; Rider, Gene

    2005-09-01

    Noise from toys is an issue receiving increasing attention in the toy and consumer product safety communities. Concern over loud toys is motivated both by reports of increasing hearing loss among children (the U.S. CDC estimated in 2001 that 12.5% of U.S. children 6 to 19 years old have permanent or temporary noise induced threshold shift in one or both ears) and by technological advances enabling sound and noise producing toys of increased play value at lower and lower cost. Consumer watchdog groups such as PIRG routinely identify excessively loud toys in their yearly lists of most dangerous toys. In 2003 ASTM revised its toy safety standard (F963-03) to include A and C weighted sound pressure level measurements and specific play or use dependent measurement geometries. RAM Consulting measures noise from toys as part of a comprehensive product safety program. Sound measurement equipment, geometries, and procedures used at RAM for different types of toys will be discussed. Unusual problems in noise measurement will be considered, as will the appropriateness of A and C weighting for the youngest age groups.

  7. New aspects of subsonic aerodynamic noise theory

    NASA Technical Reports Server (NTRS)

    Goldstein, M. E.; Howes, W. L.

    1973-01-01

    A theory of aerodynamic noise is presented which differs from Lighthill's theory primarily in the way in which convection of the noise sources is treated. The sound directivity pattern obtained from the present theory agrees better with jet-noise directivity data than does that obtained from Lighthill's theory. The results imply that the shear-noise contribution to jet noise is smaller than previously expected.

  8. [Noise exposure in neonatal intensive care units].

    PubMed

    Magnavita, V; Arslan, E; Benini, F

    1994-01-01

    This study evaluates the exposure of newborn babies in neonatal intensive care units (NICU) to noise which can cause hearing lesions directly (acoustic trauma) as well as indirectly (hypoxia). Moreover, noise can have an aggravating effect when combined with other potentially harmful factors in the NICU, such as ototoxic medication or stress due to other external stimuli, such as excessively bright light, lack of a day/night rhythm or pain. Sound pressure levels were measured in the NICU and inside the cribs in various experimental conditions, classified under 3 different types of sound events: constant background noise, variations in background noise and impulsive events. The main sources of noise detected were crib noise generated by ventilation and temperature control systems, ambient noise in the room, noise caused by the staff in the NICU, noise generated by crib alarm systems and NICU apparatus and noise caused by activity on the crib cover or on its plexiglas top. Findings revealed that the influence of ambient noise is fairly irrelevant. Background noise and its variations concerned with activities in the department never exceeded the limits considered potentially harmful to adults (DRC), whereas the impulsive noise generated by staff on the cribs or on the plexiglas tops was considerable and potentially harmful. These findings demonstrate that it is feasible and relatively easy to control noise in the NICU and significantly reduce the impulsive noise component by training staff to be more careful and avoid any unnecessary jolting and rough handling on and near the cribs.

  9. Measurement of hearing aid internal noise1

    PubMed Central

    Lewis, James D.; Goodman, Shawn S.; Bentler, Ruth A.

    2010-01-01

    Hearing aid equivalent input noise (EIN) measures assume the primary source of internal noise to be located prior to amplification and to be constant regardless of input level. EIN will underestimate internal noise in the case that noise is generated following amplification. The present study investigated the internal noise levels of six hearing aids (HAs). Concurrent with HA processing of a speech-like stimulus with both adaptive features (acoustic feedback cancellation, digital noise reduction, microphone directionality) enabled and disabled, internal noise was quantified for various stimulus levels as the variance across repeated trials. Changes in noise level as a function of stimulus level demonstrated that (1) generation of internal noise is not isolated to the microphone, (2) noise may be dependent on input level, and (3) certain adaptive features may contribute to internal noise. Quantifying internal noise as the variance of the output measures allows for noise to be measured under real-world processing conditions, accounts for all sources of noise, and is predictive of internal noise audibility. PMID:20370034

  10. Vessel Noise Promotes Hull Fouling.

    PubMed

    Stanley, Jenni A; Wilkens, Serena; McDonald, Justin I; Jeffs, Andrew G

    2016-01-01

    Fouling of submerged vessel hulls due to the rapid settlement of algae and invertebrates is a longstanding and costly problem. It is widely thought that the presence of extensive vacant surfaces on vessel hulls is responsible for the rapid attachment and growth of biofouling. We investigated whether noise from vessels in port could also be involved in promoting the settlement and growth of common biofouling organisms on vessel hulls. Three important biofouling species exhibited significantly faster development and settlement and better survival when exposed to vessel noise compared with control species. The extent of these responses appeared to vary in relation to the intensity of the vessel noise and may help to explain differences in biofouling observed on vessel hulls.

  11. 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.

  12. Noise suppressing capillary separation system

    DOEpatents

    Yeung, Edward S.; Xue, Yongjun

    1996-07-30

    A noise-suppressing capillary separation system for detecting the real-time presence or concentration of an analyte in a sample is provided. The system contains a capillary separation means through which the analyte is moved, a coherent light source that generates a beam which is split into a reference beam and a sample beam that irradiate the capillary, and a detector for detecting the reference beam and the sample beam light that transmits through the capillary. The laser beam is of a wavelength effective to be absorbed by a chromophore in the capillary. The system includes a noise suppressing system to improve performance and accuracy without signal averaging or multiple scans.

  13. Noise-enabled optical ratchets

    NASA Astrophysics Data System (ADS)

    León-Montiel, Roberto De J.; Quinto-Su, Pedro A.

    2017-03-01

    In this contribution, we report on the implementation of a novel noise-enabled optical ratchet system. We demonstrate that, unlike commonly-used ratchet schemes—where complex asymmetric optical potentials are needed—efficient transport of microparticles across a one-dimensional optical lattice can be produced by introducing controllable noise in the system. This work might open interesting routes towards the development of new technologies aimed at enhancing the efficiency of transport occurring at the micro- and nanoscale, from novel particle-sorting tools to efficient molecular motors.

  14. Ambient Noise in the Sea

    DTIC Science & Technology

    1984-01-01

    Pacific Ocean ....... ................. 4-11 4-7 Ambient noise spectra within and below a surface duct . . . . 4-13 5-1 Geometry of a simple model for... suspension system and the barge at the 100-ft hydrophone. The noise gradient tends to be greater at low frequencies than at high. We note from Figure...reflection). Expressing r, k and dr in terms of h and e, we 5-1 "-- -- ’dA / / I0 h I , ŕ"(L•)v ŕŔCOSvn{ PF Figure 5-1. Geometry of a simple model

  15. 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.

  16. Low noise optical position sensor

    DOEpatents

    Spear, Jonathan David

    1999-01-01

    A novel optical position sensor is described that uses two component photodiodes electrically connected in parallel, with opposing polarities. A lens provides optical gain and restricts the acceptance angle of the detector. The response of the device to displacements of an optical spot is similar to that of a conventional bi-cell type position sensitive detector. However, the component photodiode design enables simpler electronic amplification with inherently less electrical noise than the bi-cell. Measurements by the sensor of the pointing noise of a focused helium-neon laser as a function of frequency demonstrate high sensitivity and suitability for optical probe beam deflection experiments.

  17. Low noise optical position sensor

    DOEpatents

    Spear, J.D.

    1999-03-09

    A novel optical position sensor is described that uses two component photodiodes electrically connected in parallel, with opposing polarities. A lens provides optical gain and restricts the acceptance angle of the detector. The response of the device to displacements of an optical spot is similar to that of a conventional bi-cell type position sensitive detector. However, the component photodiode design enables simpler electronic amplification with inherently less electrical noise than the bi-cell. Measurements by the sensor of the pointing noise of a focused helium-neon laser as a function of frequency demonstrate high sensitivity and suitability for optical probe beam deflection experiments. 14 figs.

  18. Low-noise pulse conditioner

    DOEpatents

    Bird, David A.

    1983-01-01

    A low-noise pulse conditioner is provided for driving electronic digital processing circuitry directly from differentially induced input pulses. The circuit uses a unique differential-to-peak detector circuit to generate a dynamic reference signal proportional to the input peak voltage. The input pulses are compared with the reference signal in an input network which operates in full differential mode with only a passive input filter. This reduces the introduction of circuit-induced noise, or jitter, generated in ground referenced input elements normally used in pulse conditioning circuits, especially speed transducer processing circuits.

  19. Annoyance of helicopter impulsive noise

    NASA Technical Reports Server (NTRS)

    Dambra, F.; Damongeot, A.

    1978-01-01

    Psychoacoustic studies of helicopter impulsive noise were conducted in order to qualify additional annoyance due to this feature and to develop physical impulsiveness descriptors to develop impulsivity correction methods. The currently proposed descriptors and methods of impulsiveness correction are compared using a multilinear regression analysis technique. It is shown that the presently recommended descriptor and correction method provides the best correlation with the subjective evaluations of real helicopter impulsive noises. The equipment necessary for data processing in order to apply the correction method is discussed.

  20. Activity interference and noise annoyance

    NASA Astrophysics Data System (ADS)

    Hall, F. L.; Taylor, S. M.; Birnie, S. E.

    1985-11-01

    Debate continues over differences in the dose-response functions used to predict the annoyance at different sources of transportation noise. This debate reflects the lack of an accepted model of noise annoyance in residential communities. In this paper a model is proposed which is focussed on activity interference as a central component mediating the relationship between noise exposure and annoyance. This model represents a departure from earlier models in two important respects. First, single event noise levels (e.g., maximum levels, sound exposure level) constitute the noise exposure variables in place of long-term energy equivalent measures (e.g., 24-hour Leq or Ldn). Second, the relationships within the model are expressed as probabilistic rather than deterministic equations. The model has been tested by using acoustical and social survey data collected at 57 sites in the Toronto region exposed to aircraft, road traffic or train noise. Logit analysis was used to estimate two sets of equations. The first predicts the probability of activity interference as a function of event noise level. Four types of interference are included: indoor speech, outdoor speech, difficulty getting to sleep and awakening. The second set predicts the probability of annoyance as a function of the combination of activity interferences. From the first set of equations, it was possible to estimate a function for indoor speech interference only. In this case, the maximum event level was the strongest predictor. The lack of significant results for the other types of interference is explained by the limitations of the data. The same function predicts indoor speech interference for all three sources—road, rail and aircraft noise. The results for the second set of equations show strong relationships between activity interference and the probability of annoyance. Again, the parameters of the logit equations are similar for the three sources. A trial application of the model predicts a higher

  1. Noise-enabled optical ratchets

    PubMed Central

    León-Montiel, Roberto de J.; Quinto-Su, Pedro A.

    2017-01-01

    In this contribution, we report on the implementation of a novel noise-enabled optical ratchet system. We demonstrate that, unlike commonly-used ratchet schemes—where complex asymmetric optical potentials are needed—efficient transport of microparticles across a one-dimensional optical lattice can be produced by introducing controllable noise in the system. This work might open interesting routes towards the development of new technologies aimed at enhancing the efficiency of transport occurring at the micro- and nanoscale, from novel particle-sorting tools to efficient molecular motors. PMID:28287152

  2. Digital Noise Reduction: An Overview

    PubMed Central

    Bentler, Ruth; Chiou, Li-Kuei

    2006-01-01

    Digital noise reduction schemes are being used in most hearing aids currently marketed. Unlike the earlier analog schemes, these manufacturer-specific algorithms are developed to acoustically analyze the incoming signal and alter the gain/output characteristics according to their predetermined rules. Although most are modulation-based schemes (ie, differentiating speech from noise based on temporal characteristics), spectral subtraction techniques are being applied as well. The purpose of this article is to overview these schemes in terms of their differences and similarities. PMID:16959731

  3. Quantum Noise from Reduced Dynamics

    NASA Astrophysics Data System (ADS)

    Vacchini, Bassano

    2016-07-01

    We consider the description of quantum noise within the framework of the standard Copenhagen interpretation of quantum mechanics applied to a composite system environment setting. Averaging over the environmental degrees of freedom leads to a stochastic quantum dynamics, described by equations complying with the constraints arising from the statistical structure of quantum mechanics. Simple examples are considered in the framework of open system dynamics described within a master equation approach, pointing in particular to the appearance of the phenomenon of decoherence and to the relevance of quantum correlation functions of the environment in the determination of the action of quantum noise.

  4. Low-noise nozzle valve

    NASA Astrophysics Data System (ADS)

    Gwin, Hal S.; Aaron, James

    1990-09-01

    A low noise, variable discharage area, valve is constructed having opposed recesses within which a pair of gates are slidably disposed. Each of the gates is provided with upstream edges having a radius thereon, the radius enabling smooth, accelerated, low noise flow therebetween. The gates are further provided with tracks along each side, which in turn slide along splines set in the side walls of the valve. A threaded rod which rotates in a threaded insert in a rear wall of each of the gates, serves to move the gates within their respective recesses.

  5. The Problems with "Noise Numbers" for Wind Farm Noise Assessment

    ERIC Educational Resources Information Center

    Thorne, Bob

    2011-01-01

    Human perception responds primarily to sound character rather than sound level. Wind farms are unique sound sources and exhibit special audible and inaudible characteristics that can be described as modulating sound or as a tonal complex. Wind farm compliance measures based on a specified noise number alone will fail to address problems with noise…

  6. The Problems with "Noise Numbers" for Wind Farm Noise Assessment

    ERIC Educational Resources Information Center

    Thorne, Bob

    2011-01-01

    Human perception responds primarily to sound character rather than sound level. Wind farms are unique sound sources and exhibit special audible and inaudible characteristics that can be described as modulating sound or as a tonal complex. Wind farm compliance measures based on a specified noise number alone will fail to address problems with noise…

  7. Combustion generated noise in gas turbine combustors. [engine noise/noise reduction

    NASA Technical Reports Server (NTRS)

    Strahle, W. C.; Shivashankara, B. N.

    1974-01-01

    Experiments were conducted to determine the noise power and spectra emitted from a gas turbine combustor can exhausting to the atmosphere. Limited hot wire measurements were made of the cold flow turbulence level and spectra within the can. The fuels used were JP-4, acetone and methyl alcohol burning with air at atmospheric pressure. The experimental results show that for a fixed fuel the noise output is dominated by the airflow rate and not the fuel/air ratio. The spectra are dominated by the spectra of the cold flow turbulence spectra which were invariant with airflow rate in the experiments. The effect of fuel type on the noise power output was primarily through the heat of combustion and not the reactivity. A theory of combustion noise based upon the flame radiating to open surroundings is able to reasonably explain the observed results. A thermoacoustic efficiency for noise radiation as high as .00003 was observed in this program for JP-4 fuel. Scaling rules are presented for installed configurations.

  8. Evaluation of Noise Exposure Secondary to Wind Noise in Cyclists.

    PubMed

    Seidman, Michael D; Wertz, Anna G; Smith, Matthew M; Jacob, Steve; Ahsan, Syed F

    2017-07-01

    Objective Determine if the noise levels of wind exposure experienced by cyclists reach levels that could contribute to noise-induced hearing loss. Study Design Industrial lab research. Setting Industrial wind tunnel. Subjects and Methods A commercial-grade electric wind tunnel was used to simulate different speeds encountered by a cyclist. A single cyclist was used during the simulation for audiometric measurements. Microphones attached near the ears of the cyclist were used to measure the sound (dB sound pressure level) experienced by the cyclist. Loudness levels were measured with the head positioned at 15-degree increments from 0 degrees to 180 degrees relative to the oncoming wind at different speeds (10-60 mph). Results Wind noise ranged from 84.9 dB at 10 mph and increased proportionally with speed to a maximum of 120.3 dB at 60 mph. The maximum of 120.3 dB was measured at the downwind ear when the ear was 90 degrees away from the wind. Conclusions Wind noise experienced by a cyclist is proportional to the speed and the directionality of the wind current. Turbulent air flow patterns are observed that contribute to increased sound exposure in the downwind ear. Consideration of ear deflection equipment without compromising sound awareness for cyclists during prolonged rides is advised to avoid potential noise trauma. Future research is warranted and can include long-term studies including dosimetry measures of the sound and yearly pre- and postexposure audiograms of cyclists to detect if any hearing loss occurs with long-term cycling.

  9. FAA/NASA En Route Noise Symposium

    NASA Technical Reports Server (NTRS)

    Powell, Clemans A. (Compiler)

    1990-01-01

    Aircraft community noise annoyance is traditionally a concern only in localities near airports. The proposed introduction of large commercial airplanes with advanced turboprop propulsion systems with supersonic propellers has given rise to concerns of noise annoyance in areas previously considered not to be impacted by aircraft noise. A symposium was held to assess the current knowledge of factors important to the impact of en route noise and to aid in the formulation of FAA and NASA programs in the area. Papers were invited on human response to aircraft noise in areas with low ambient noise levels, aircraft noise heard indoors and outdoors, aircraft noise in recreational areas, detection of propeller and jet aircraft noise, and methodological issues relevant to the design of future studies.

  10. Suggested noise criteria for plumbing systems

    NASA Astrophysics Data System (ADS)

    Lilly, Jerry

    2005-09-01

    The issue of noise that is generated by plumbing systems has been addressed in several articles and texts in the acoustic literature, but most of this information deals with a description of the various noise generation mechanisms and recommended methods of controlling noise from plumbing fixtures and piping. As with any noise source that has the potential for generating annoyance, the question of how much noise is too much noise eventually arises. Chapter 47 of the 2003 ASHRAE Applications Handbook contains newly published guidelines for plumbing noise criteria as it impacts building occupants. This paper discusses the ASHRAE guidelines, and it also suggests additional noise criteria for other plumbing-related sources of noise in multitenant buildings.

  11. Forward sweep, low noise rotor blade

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F. (Inventor)

    1994-01-01

    A forward-swept, low-noise rotor blade includes an inboard section, an aft-swept section, and a forward-swept outboard section. The rotor blade reduces the noise of rotorcraft, including both standard helicopters and advanced systems such as tiltrotors. The primary noise reduction feature is the forward sweep of the planform over a large portion of the outer blade radius. The rotor blade also includes an aft-swept section. The purpose of the aft-swept region is to provide a partial balance to pitching moments produced by the outboard forward-swept portion of the blade. The noise source showing maximum noise reduction is blade-vortex interaction (BVI) noise. Also reduced are thickness, noise, high speed impulsive noise, cabin vibration, and loading noise.

  12. New developments in blown flap noise technology

    NASA Technical Reports Server (NTRS)

    Gibson, J. S.

    1976-01-01

    The noise technology relating to blown-flap systems is reviewed. There are three general sources of noise: turbomachinery, airframe, and the interaction noise of the jet blowing on the flaps. The latter noise-source area is the most critical and the main subject dicussed. Characteristics of lower surface blown and upper surface blown systems are described, including noise spectra, directivity, jet velocity characteristics, aircraft geometric variation effects, and aircraft forward speed effects. Noise reduction concepts are described, including slowing down the jet flow field by devices and engine cycle modifications, structural geometry and shielding modifications, local flow field modifications of the passive and active type, and the absorption of noise. It is concluded that, while there has been considerable progress in the past several years, low noise characteristics in blown flap aircraft must be largely built in by better application of low noise principles during the design.

  13. 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.

  14. 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.

  15. Application of barrier in industrial noise control

    NASA Astrophysics Data System (ADS)

    Chui, Jonathan; Ma, Yong; Hertil, Salem

    2005-04-01

    Noise barriers have been widely used in environmental noise control, such as traffic and railway noise. Actually they are also cost-effective mitigation measures in industrial noise control. In this paper, the applications of noise barrier in power plant are introduced. Types of barrier and barrier materials are briefly summarized and compared. A case study of noise barrier implement in a 50 MW power plant is presented. The plant is a natural gas-fired simple-cycle peaking facility, and consists of two opposed gas combustion turbine directly connected through a coupling to a single generator. Some residences are located around the facility. A noise barrier wall was designed and installed surrounding the facility to control the noise impact of the plant on the residences. The acoustic modeling software Cadna/A was used to predict the noise insertion loss of the barrier. The prediction results were also compared with the site measurements.

  16. Adaptive Noise Suppression Using Digital Signal Processing

    NASA Technical Reports Server (NTRS)

    Kozel, David; Nelson, Richard

    1996-01-01

    A signal to noise ratio dependent adaptive spectral subtraction algorithm is developed to eliminate noise from noise corrupted speech signals. The algorithm determines the signal to noise ratio and adjusts the spectral subtraction proportion appropriately. After spectra subtraction low amplitude signals are squelched. A single microphone is used to obtain both eh noise corrupted speech and the average noise estimate. This is done by determining if the frame of data being sampled is a voiced or unvoiced frame. During unvoice frames an estimate of the noise is obtained. A running average of the noise is used to approximate the expected value of the noise. Applications include the emergency egress vehicle and the crawler transporter.

  17. 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.

  18. Background noise spectra of global seismic stations

    SciTech Connect

    Wada, M.M.; Claassen, J.P.

    1996-08-01

    Over an extended period of time station noise spectra were collected from various sources for use in estimating the detection and location performance of global networks of seismic stations. As the database of noise spectra enlarged and duplicate entries became available, an effort was mounted to more carefully select station noise spectra while discarding others. This report discusses the methodology and criteria by which the noise spectra were selected. It also identifies and illustrates the station noise spectra which survived the selection process and which currently contribute to the modeling efforts. The resulting catalog of noise statistics not only benefits those who model network performance but also those who wish to select stations on the basis of their noise level as may occur in designing networks or in selecting seismological data for analysis on the basis of station noise level. In view of the various ways by which station noise were estimated by the different contributors, it is advisable that future efforts which predict network performance have available station noise data and spectral estimation methods which are compatible with the statistics underlying seismic noise. This appropriately requires (1) averaging noise over seasonal and/or diurnal cycles, (2) averaging noise over time intervals comparable to those employed by actual detectors, and (3) using logarithmic measures of the noise.

  19. Eye Noise and Map Design.

    ERIC Educational Resources Information Center

    Merriam, Mylon

    This paper describes the physiological "eye noise" effect of line contrast in maps and considers the effect of line contrast on the direct picture of terrain surface as produced by shaded relief. An attempt is made to describe map reading in its two major steps: 1) the enrichment of the brain image resulting from scanning the map sheet,…

  20. Noise Properties of Rectifying Nanopores

    SciTech Connect

    Powell, M R; Sa, N; Davenport, M; Healy, K; Vlassiouk, I; Letant, S E; Baker, L A; Siwy, Z S

    2011-02-18

    Ion currents through three types of rectifying nanoporous structures are studied and compared for the first time: conically shaped polymer nanopores, glass nanopipettes, and silicon nitride nanopores. Time signals of ion currents are analyzed by power spectrum. We focus on the low-frequency range where the power spectrum magnitude scales with frequency, f, as 1/f. Glass nanopipettes and polymer nanopores exhibit non-equilibrium 1/f noise, thus the normalized power spectrum depends on the voltage polarity and magnitude. In contrast, 1/f noise in rectifying silicon nitride nanopores is of equilibrium character. Various mechanisms underlying the voltage-dependent 1/f noise are explored and discussed, including intrinsic pore wall dynamics, and formation of vortices and non-linear flow patterns in the pore. Experimental data are supported by modeling of ion currents based on the coupled Poisson-Nernst-Planck and Navier Stokes equations. We conclude that the voltage-dependent 1/f noise observed in polymer and glass asymmetric nanopores might result from high and asymmetric electric fields inducing secondary effects in the pore such as enhanced water dissociation.

  1. Helicopter tail rotor noise analyses

    NASA Technical Reports Server (NTRS)

    George, A. R.; Chou, S. T.

    1986-01-01

    A study was made of helicopter tail rotor noise, particularly that due to interactions with the main rotor tip vortices, and with the fuselage separation mean wake. The tail rotor blade-main rotor tip vortex interaction is modelled as an airfoil of infinite span cutting through a moving vortex. The vortex and the geometry information required by the analyses are obtained through a free wake geometry analysis of the main rotor. The acoustic pressure-time histories for the tail rotor blade-vortex interactions are then calculated. These acoustic results are compared to tail rotor loading and thickness noise, and are found to be significant to the overall tail rotor noise generation. Under most helicopter operating conditions, large acoustic pressure fluctuations can be generated due to a series of skewed main rotor tip vortices passing through the tail rotor disk. The noise generation depends strongly upon the helicopter operating conditions and the location of the tail rotor relative to the main rotor.

  2. Radiated noise of ducted fans

    NASA Technical Reports Server (NTRS)

    Eversman, Walter

    1992-01-01

    The differences in the radiated acoustic fields of ducted and unducted propellers of the same thrust operating under similar conditions are investigated. An FEM model is created for the generation, propagation, and radiation of steady, rotor alone noise and exit guide vane interaction noise of a ducted fan. For a specified number of blades, angular mode harmonic, and rotor angular velocity, the acoustic field is described in a cylindrical coordinate system reduced to only the axial and radial directions. It is found that, contrary to the usual understanding of the Tyler and Sofrin (1962) result, supersonic tip speed rotor noise can be cut off if the tip Mach number is only slightly in excess of unity and if the number of blades is relatively small. If there are many blades, the fundamental angular mode number is large, and the Tyler and Sofrin result for thin annuli becomes more relevant. Shrouding of subsonic tip speed propellers is a very effective means of controlling rotor alone noise.

  3. Hydrodynamic Noise and Surface Compliance.

    DTIC Science & Technology

    1982-09-08

    Geib . 50 Thus, the TBL noise spectrum for a rigid boundary is fairly flat at the lower frequencies where transducer size effects may not be important...Layer," Soy. Phys. Acous., vol. 12, 1966, pp. 228-229. 50. F. E. Geib , Jr., "Measurements on the Effect of Transducer Size on the Resolution of Boundary

  4. Radiated noise of ducted fans

    NASA Astrophysics Data System (ADS)

    Eversman, Walter

    The differences in the radiated acoustic fields of ducted and unducted propellers of the same thrust operating under similar conditions are investigated. An FEM model is created for the generation, propagation, and radiation of steady, rotor alone noise and exit guide vane interaction noise of a ducted fan. For a specified number of blades, angular mode harmonic, and rotor angular velocity, the acoustic field is described in a cylindrical coordinate system reduced to only the axial and radial directions. It is found that, contrary to the usual understanding of the Tyler and Sofrin (1962) result, supersonic tip speed rotor noise can be cut off if the tip Mach number is only slightly in excess of unity and if the number of blades is relatively small. If there are many blades, the fundamental angular mode number is large, and the Tyler and Sofrin result for thin annuli becomes more relevant. Shrouding of subsonic tip speed propellers is a very effective means of controlling rotor alone noise.

  5. Noise Amplification in HGHG Seeding

    SciTech Connect

    Stupakov, G.; /SLAC

    2010-08-25

    An essential element of seeded FEL based on high-gain harmonic generation (HGHG) or echo-enabled harmonic generation (EEHG) is an undulator-modulator, in which interaction with a laser beam modulates the beam energy. We study how the interaction of electrons in this undulator-modulator changes the noise properties of the beam.

  6. Noise Exposures of Rural Adolescents

    ERIC Educational Resources Information Center

    Humann, Michael; Sanderson, Wayne; Flamme, Greg; Kelly, Kevin M.; Moore, Genna; Stromquist, Ann; Merchant, James A.

    2011-01-01

    Purpose: This project was conducted to characterize the noise exposure of adolescents living in rural and agricultural environments. Methods: From May to October, 25 adolescents ages 13 through 17, living either on a farm or a rural nonfarm, were enrolled in the study. Subjects received training on the correct operation and use of personal noise…

  7. Adaptive avoidance of reef noise.

    PubMed

    Simpson, Stephen D; Radford, Andrew N; Tickle, Edward J; Meekan, Mark G; Jeffs, Andrew G

    2011-02-04

    Auditory information is widely used throughout the animal kingdom in both terrestrial and aquatic environments. Some marine species are dependent on reefs for adult survival and reproduction, and are known to use reef noise to guide orientation towards suitable habitat. Many others that forage in food-rich inshore waters would, however, benefit from avoiding the high density of predators resident on reefs, but nothing is known about whether acoustic cues are used in this context. By analysing a sample of nearly 700,000 crustaceans, caught during experimental playbacks in light traps in the Great Barrier Reef lagoon, we demonstrate an auditory capability in a broad suite of previously neglected taxa, and provide the first evidence in any marine organisms that reef noise can act as a deterrent. In contrast to the larvae of species that require reef habitat for future success, which showed an attraction to broadcasted reef noise, taxa with a pelagic or nocturnally emergent lifestyle actively avoided it. Our results suggest that a far greater range of invertebrate taxa than previously thought can respond to acoustic cues, emphasising yet further the potential negative impact of globally increasing levels of underwater anthropogenic noise.

  8. Noise Properties of Rectifying Nanopore

    SciTech Connect

    Vlassiouk, Ivan V

    2011-01-01

    Ion currents through three types of rectifying nanoporous structures are studied and compared: conically shaped polymer nanopores, glass nanopipettes, and silicon nitride nanopores. Time signals of ion currents are analyzed by the power spectrum. We focus on the low-frequency range where the power spectrum magnitude scales with frequency, f, as 1/f. Glass nanopipettes and polymer nanopores exhibit nonequilibrium 1/f noise; thus, the normalized power spectrum depends on the voltage polarity and magnitude. In contrast, 1/f noise in rectifying silicon nitride nanopores is of equilibrium character. Various mechanisms underlying the voltage-dependent 1/f noise are explored and discussed, including intrinsic pore wall dynamics and formation of vortices and nonlinear flow patterns in the pore. Experimental data are supported by modeling of ion currents based on the coupled Poisson-Nernst-Planck and Navier-Stokes equations. We conclude that the voltage-dependent 1/f noise observed in polymer and glass asymmetric nanopores might result from high and asymmetric electric fields, inducing secondary effects in the pore, such as enhanced water dissociation.

  9. Oscillator With Low Phase Noise

    NASA Technical Reports Server (NTRS)

    Kleinberg, Leonard L.

    1987-01-01

    Phase errors cancelled for high frequency stability. Radio-frequency oscillator achieves high stability of frequency through parallel, two-amplifier configuration in which effects cause phase noise tend to cancel each other. Circuit includes two amplifiers with resonating elements, each constitutes part of feedback loop of other. Generate same frequency because each circuit provides other with conditions necessary for oscillation.

  10. Noise Exposures of Rural Adolescents

    ERIC Educational Resources Information Center

    Humann, Michael; Sanderson, Wayne; Flamme, Greg; Kelly, Kevin M.; Moore, Genna; Stromquist, Ann; Merchant, James A.

    2011-01-01

    Purpose: This project was conducted to characterize the noise exposure of adolescents living in rural and agricultural environments. Methods: From May to October, 25 adolescents ages 13 through 17, living either on a farm or a rural nonfarm, were enrolled in the study. Subjects received training on the correct operation and use of personal noise…

  11. Adaptive Avoidance of Reef Noise

    PubMed Central

    Simpson, Stephen D.; Radford, Andrew N.; Tickle, Edward J.; Meekan, Mark G.; Jeffs, Andrew G.

    2011-01-01

    Auditory information is widely used throughout the animal kingdom in both terrestrial and aquatic environments. Some marine species are dependent on reefs for adult survival and reproduction, and are known to use reef noise to guide orientation towards suitable habitat. Many others that forage in food-rich inshore waters would, however, benefit from avoiding the high density of predators resident on reefs, but nothing is known about whether acoustic cues are used in this context. By analysing a sample of nearly 700,000 crustaceans, caught during experimental playbacks in light traps in the Great Barrier Reef lagoon, we demonstrate an auditory capability in a broad suite of previously neglected taxa, and provide the first evidence in any marine organisms that reef noise can act as a deterrent. In contrast to the larvae of species that require reef habitat for future success, which showed an attraction to broadcasted reef noise, taxa with a pelagic or nocturnally emergent lifestyle actively avoided it. Our results suggest that a far greater range of invertebrate taxa than previously thought can respond to acoustic cues, emphasising yet further the potential negative impact of globally increasing levels of underwater anthropogenic noise. PMID:21326604

  12. Radiated noise of ducted fans

    NASA Technical Reports Server (NTRS)

    Eversman, Walter

    1992-01-01

    The differences in the radiated acoustic fields of ducted and unducted propellers of the same thrust operating under similar conditions are investigated. An FEM model is created for the generation, propagation, and radiation of steady, rotor alone noise and exit guide vane interaction noise of a ducted fan. For a specified number of blades, angular mode harmonic, and rotor angular velocity, the acoustic field is described in a cylindrical coordinate system reduced to only the axial and radial directions. It is found that, contrary to the usual understanding of the Tyler and Sofrin (1962) result, supersonic tip speed rotor noise can be cut off if the tip Mach number is only slightly in excess of unity and if the number of blades is relatively small. If there are many blades, the fundamental angular mode number is large, and the Tyler and Sofrin result for thin annuli becomes more relevant. Shrouding of subsonic tip speed propellers is a very effective means of controlling rotor alone noise.

  13. Supersonic coaxial jet noise predictions

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.; Morris, Philip J.

    1995-01-01

    Predictions are made for the noise radiation from supersonic, coaxial jets. These predictions are based on the assumption that the noise radiation in the downstream direction of supersonic jets is dominated by sound generated by instability waves with supersonic phase velocities relative to ambient. Since the analysis requires a known mean flow and the coaxial jet mean flow is not described easily in terms of analytical functions, a numerical prediction is made for its development. The compressible, Reynolds averaged, boundary layer equations are solved with a modified mixing length turbulence model. The model has been calibrated to account for compressibility and temperature effects on the rate of mixing. Both normal and inverted velocity profile jets are considered. Predictions are made for the differences between the noise radiated by coaxial jets with difference operating conditions and a single reference jet with the same thrust, mass flow, and exit area. The effects of area ratio changes and simulated enhanced mixing on noise radiation are also considered.

  14. Introduction: Unsolved Problems on Noise

    NASA Astrophysics Data System (ADS)

    Oriols, X.; Ciliberto, S.

    2016-05-01

    This paper is an introduction to the special issue of the 7th Int. Conf. on Unsolved Problems on Noise (UPoN) that took place at Casa Convalescència in Barcelona (Spain) in July 2015. The aim of the UPoN conferences is to provide a forum for researchers working on different fields of noise, fluctuations and variability, where they present their scientific problems which resist solutions. The papers of this Special Issue reflect the interdisciplinary topics (physics, biology, circuits, financial markets, psychology, technology, etc) presented at the UPoN conference. Noise is not only a hindrance to signal detection, but it is indeed a valuable source of information (not present in the signal) that help us to get a deeper understanding on how Nature works. This special issue of the 7th International Conference on Unsolved Problems on Noise (UPoN) is dedicated to Laszlo Kish in the occasion of his 60th birthday. He organized the first edition of these UPoN conferences in Szeged (Hungary) in 1996. Many of us have greatly benefited from his ‘volcanic imagination in tackling new problems from unconventional points of views’.

  15. Shot noise in radiobiological systems.

    PubMed

    Datesman, A

    2016-11-01

    As a model for human tissue, this report considers the rate of free radical generation in a dilute solution of water in which a beta-emitting radionuclide is uniformly dispersed. Each decay dissipates a discrete quantity of energy, creating a large number of free radicals in a short time within a small volume determined by the beta particle range. Representing the instantaneous dissipated power as a train of randomly-spaced pulses, the time-averaged dissipated power p¯ and rate of free radical generation g¯ are derived. The analogous result in the theory of electrical circuits is known as the shot noise theorem. The reference dose of X-rays Dref producing an identical rate of free radical generation and level of oxidative stress is shown a) to increase with the square root of the absorbed dose, D, and b) to be far larger than D. This finding may have important consequences for public health in cases where the level of shot noise exceeds some noise floor corresponding to equilibrium biological processes. An estimate of this noise floor is made using the example of potassium-40, a beta-emitting radioisotope universally present in living tissue.

  16. Theoretical aspects of supersonic jet noise

    NASA Technical Reports Server (NTRS)

    Tam, Christopher K. W.

    1992-01-01

    The topics covered include the following: the three components of supersonic jet noise; shock cell structure of imperfectly expanded jets; large turbulence structures/instability waves; supersonic jet noise theory; generation of turbulent mixing noise; comparisons between predicted peak noise frequency and direction of radiation with measurements; Strouhal number of maximum SPL of hot supersonic jets; near field sound pressure level contours; generation of broadband shock associated noise; calculated and measured far field shock noise spectra; generation of screech tones; and calculated and measured Strouhal number of screech tones.

  17. 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.

  18. Speech enhancement using a generic noise codebook.

    PubMed

    Srinivasan, Sriram; Rao Naidu, D Hanumantha

    2012-08-01

    Although single-microphone noise reduction methods perform well in stationary noise environments, their performance in non-stationary conditions remains unsatisfactory. Use of prior knowledge about speech and noise power spectral densities in the form of trained codebooks has been previously shown to address this limitation. While it is possible to use trained speech codebooks in a practical system, the variety of noise types encountered in practice makes the use of trained noise codebooks less practical. This letter presents a method that uses a generic noise codebook for speech enhancement that can be generated on-the-fly and provides good performance.

  19. Helicopter external noise requirements: FAA perspective

    NASA Technical Reports Server (NTRS)

    Foster, C. R.

    1978-01-01

    Enactment of helicopter noise certification standards for the control of noise impact contributing to community annoyance is considered in terms of the development of helicopters as an environmentally compatible air transportation mode. Increased use of helicopters for commercial applications and public awareness of aircraft noise are cited as factors making development of helicopter noise standards necessary both for the protection of the environmental interest of the community and to ensure the orderly growth of the helicopter industry itself. Noise sources, technology trends in helicopter design, and design concepts to control helicopter noise are discussed along with the regulatory background and specific helicopter regulatory concepts.

  20. Community noise technology needs: Boeing's perspective

    NASA Technical Reports Server (NTRS)

    Nihart, Gene L.

    1992-01-01

    Airport community acceptance of High Speed Civil Transport (HSCT) noise levels will depend on the relative noise levels of airplanes flying at the time of introduction. The 85 dBA noise contours for the range of large subsonic airplanes that are expected to be in service in the early 21st century are shown as a shaded area. A certifiable HSCT noise contour as shown, would be somewhat wider along the runway, but about the same in the residential areas downrange. An HSCT noise rule should insure this noise capability.

  1. Noise in nonlinear nanoelectromechanical resonators

    NASA Astrophysics Data System (ADS)

    Guerra Vidal, Diego N.

    Nano-Electro-Mechanical Systems (NEMS), due to their nanometer scale size, possess a number of desirable attributes: high sensitivity to applied forces, fast response times, high resonance frequencies and low power consumption. However, ultra small size and low power handling result in unwanted consequences: smaller signal size and higher dissipation, making the NEMS devices more susceptible to external and intrinsic noise. The simplest version of a NEMS, a suspended nanomechanical structure with two distinct excitation states, can be used as an archetypal two state system to study a plethora of fundamental phenomena such as Duffing nonlinearity, stochastic resonance, and macroscopic quantum tunneling at low temperatures. From a technical perspective, there are numerous applications such nanomechanical memory elements, microwave switches and nanomechanical computation. The control and manipulation of the mechanical response of these two state systems can be realized by exploiting a (seemingly) counterintuitive physical phenomenon, Stochastic Resonance: in a noisy nonlinear mechanical system, the presence of noise can enhance the system response to an external stimulus. This Thesis is mainly dedicated to study possible applications of Stochastic Resonance in two-state nanomechanical systems. First, on chip signal amplification by 1/falpha is observed. The effectiveness of the noise assisted amplification is observed to decrease with increasing a. Experimental evidence shows an increase in asymmetry between the two states with increasing noise color. Considering the prevalence of 1/f alpha noise in the materials in integrated circuits, the signal enhancement demonstrated here, suggests beneficial use of the otherwise detrimental noise. Finally, a nanomechanical device, operating as a reprogrammable logic gate, and performing fundamental logic functions such as AND/OR and NAND/NOR is presented. The logic function can be programmed (from AND to OR) dynamically, by

  2. Low frequency noise enhances cortisol among noise sensitive subjects during work performance.

    PubMed

    Waye, Kerstin Persson; Bengtsson, Johanna; Rylander, Ragnar; Hucklebridge, Frank; Evans, Phil; Clow, Angela

    2002-01-04

    Salivary free cortisol concentration, rated stress and annoyance were determined in 32 subjects before, during and after carrying out a battery of performance tasks for 2 hours during exposure to ventilation noise, with dominant low frequencies (low frequency noise) or a flat frequency spectrum (reference noise). Both noises had a level of 40 dBA. All subjects were studied on two occasions and were exposed to both noises in strict rotation. Subjects were categorised as high- or low-sensitive to noise in general and low frequency noise in particular on the basis of questionnaires. Cortisol concentrations during the task were not significantly modulated by the noises or related to noise sensitivity alone. The normal circadian decline in cortisol concentration was however significantly attenuated in subjects high-sensitive to noise in general, when they were exposed to the low frequency noise. This noise was rated as more annoying and more disruptive to working capacity than the reference noise. The study showed physiological evidence of increased stress related to noise sensitivity and noise exposure during work. This is the first study to demonstrate an effect of moderate levels of noise on neuroendocrine activity. The impact of long-term exposure to moderate noise levels, and particularly low frequency noise, in the workplace deserves further investigation.

  3. Psychoacoustic active noise control with ITU-R 468 noise weighting and its sound quality analysis.

    PubMed

    Bao, Hua; Panahi, Issa M S

    2010-01-01

    Non-uniform frequency response of human hearing system requires conventional active noise control (ANC) system to be modified. Psychoacoustic active noise control (PANC) system based on filtered-E least-mean-square (FELMS) structure aims to improve the noise attenuation performance in terms of hearing perception. ITU-R 468 noise weighting reflects human hearing response to random noise. In this paper we incorporate ITU-R 468 noise weighting into PANC system. Sound quality analysis is conducted for attenuated noise with a predictive pleasantness model which combines four psychoacoustic parameters (loudness, sharpness, roughness and tonality). Simulation on realistic MRI acoustic noise shows improvement of sound quality in the new system.

  4. Implementation of noise budgets for civil airports

    SciTech Connect

    Bishop, D.E.

    1982-01-01

    An increasing number of airports are faced with the need for establishing a lid on the noise from aircraft operations and for developing programs for reducing airport noise on a year-to-year basis. As an example, the California Airport Noise Standard acts to impose such programs on a number of airports in California. Any airport faced with the need to establish a quantitative reduction of noise obviously wants to achieve this reduction with the least impact on numbers of operations and reduction in air transportation services to the community. A reduction in noise and an increase in operations usually can be achieved only by encouraging use of the quietest aircraft available and, further adding incentives for operating procedures that minimize noise. One approach in administering airport noise reduction is to adopt an airport noise budget. As used in this paper, the noise budget concept implies that quantitative limits on the noise environment and on the noise contributions by major airport users will be established. Having methods for enforcing compliance with the airport budget for those airport users that exceed their budget will be established. Thus, the noise budget provides airport management, and major airport users, with quantitative measures for defining noise goals, and actual progress in achieving such goals.

  5. Mapping Urban Environmental Noise Using Smartphones

    PubMed Central

    Zuo, Jinbo; Xia, Hao; Liu, Shuo; Qiao, Yanyou

    2016-01-01

    Noise mapping is an effective method of visualizing and accessing noise pollution. In this paper, a noise-mapping method based on smartphones to effectively and easily measure environmental noise is proposed. By using this method, a noise map of an entire area can be created using limited measurement data. To achieve the measurement with certain precision, a set of methods was designed to calibrate the smartphones. Measuring noise with mobile phones is different from the traditional static observations. The users may be moving at any time. Therefore, a method of attaching an additional microphone with a windscreen is proposed to reduce the wind effect. However, covering an entire area is impossible. Therefore, an interpolation method is needed to achieve full coverage of the area. To reduce the influence of spatial heterogeneity and improve the precision of noise mapping, a region-based noise-mapping method is proposed in this paper, which is based on the distribution of noise in different region types tagged by volunteers, to interpolate and combine them to create a noise map. To validate the effect of the method, a comparison of the interpolation results was made to analyse our method and the ordinary Kriging method. The result shows that our method is more accurate in reflecting the local distribution of noise and has better interpolation precision. We believe that the proposed noise-mapping method is a feasible and low-cost noise-mapping solution. PMID:27754359

  6. 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.

  7. Noise characterization of oil and gas operations.

    PubMed

    Radtke, Cameron; Autenrieth, Daniel A; Lipsey, Tiffany; Brazile, William J

    2017-08-01

    In cooperation with The Colorado Oil and Gas Conservation Commission, researchers at Colorado State University performed area noise monitoring at 23 oil and gas sites throughout Northern Colorado. The goals of this study were to: (1) measure and compare the noise levels for the different phases of oil and gas development sites; (2) evaluate the effectiveness of noise barriers; and (3) determine if noise levels exceeded the Colorado Oil and Gas Conservation Commission noise limits. The four phases of oil and gas development include drilling, hydraulic fracturing, completion and production. Noise measurements were collected using the A- and C-weighted sound scales. Octave band analysis was also performed to characterize the frequency spectra of the noise measurements.  Noise measurements were collected using noise dosimeters and a hand-held sound-level meter at specified distances from the development sites in each cardinal direction. At 350 ft (107 m), drilling, hydraulic fracturing, and completion sites without noise barriers exceeded the maximum permissible noise levels for residential and commercial zones (55 dBA and 60 dBA, respectively). In addition, drilling and hydraulic fracturing sites with noise barriers exceeded the maximum permissible noise level for residential zones (55 dBA). However, during drilling, hydraulic fracturing, and completion operations, oil producers are allowed an exception to the noise permissible limits in that they only must comply with the industrial noise limit (80 dBA). It is stated in Rule 604.c.(2)A. that: "Operations involving pipeline or gas facility installation or maintenance, the use of a drilling rig, completion rig, workover rig, or stimulation is subject to the maximum permissible noise levels for industrial zones (80dBA)." ([8]) Production sites were within the Colorado Oil and Gas Conservation Commission permissible noise level criteria for all zones. At 350 ft (107 m) from the noise source, all drilling

  8. A community survey of helicopter noise annoyance conducted under controlled noise exposure conditions

    NASA Technical Reports Server (NTRS)

    Fields, J. M.; Powell, C. A.

    1985-01-01

    Reactions to low numbers of helicopter noise events (less than 50 per day) were studied in a community setting. Community residents were repeatedly interviewed about daily noise annoyance reactions on days when helicopter noise exposures were, without the residents' knowledge, controlled. The effects of maximum noise level and number of noise events on helicopter noise annoyance are consistent with the principles contained in LEQ-based noise indices. The effect of the duration of noise events is also consistent with LEQ-based indices. After removing the effect of differences in noise levels (LEQ) there is not an important difference between reactions to impulsive and nonimpulsive types of helicopters. EPNL, where corrected for number of overflights, and LEQ are approximately equally successful in representing the characteristics of noise which are related to human response. The new type of design provided estimates of the parameters in a noise reaction model which would not obtained with a similar degree of precision from conventional study designs.

  9. 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.

  10. When noise makes music: HIV reactivation with transcriptional noise enhancers.

    PubMed

    Tan, Xu; Elledge, Stephen J

    2014-01-01

    Reactivating latent HIV is key to depleting the virus reservoir in AIDS patients. A recent paper has described the rationale for and discovery of a new class of drugs - transcriptional noise enhancers - that can synergize with conventional transcription activators to more effectively reactivate latently infected T cells. As well as describing a promising new strategy in the bid to find a cure for AIDS, this study more broadly highlights the utility of exploring drug combinations in treatment of human disease.

  11. Photon-pair shot noise in electron shot noise

    NASA Astrophysics Data System (ADS)

    Simoneau, Jean Olivier; Virally, Stéphane; Lupien, Christian; Reulet, Bertrand

    2017-02-01

    We report the measurement of the statistics of photons in the nonclassical radiation emitted by a tunnel junction. This is obtained by measuring up to the fourth cumulant of the voltage fluctuations generated by the sample. When the electron shot noise generates a squeezed electromagnetic field, the measurement provides a strong signature of the presence of photon pairs, characterized by a Fano factor of the photon flux above unity.

  12. Switching bilateral filter with a texture/noise detector for universal noise removal.

    PubMed

    Lin, Chih-Hsing; Tsai, Jia-Shiuan; Chiu, Ching-Te

    2010-09-01

    In this paper, we propose a switching bilateral filter (SBF) with a texture and noise detector for universal noise removal. Operation was carried out in two stages: detection followed by filtering. For detection, we propose the sorted quadrant median vector (SQMV) scheme, which includes important features such as edge or texture information. This information is utilized to allocate a reference median from SQMV, which is in turn compared with a current pixel to classify it as impulse noise, Gaussian noise, or noise-free. The SBF removes both Gaussian and impulse noise without adding another weighting function. The range filter inside the bilateral filter switches between the Gaussian and impulse modes depending upon the noise classification result. Simulation results show that our noise detector has a high noise detection rate as well as a high classification rate for salt-and-pepper, uniform impulse noise and mixed impulse noise. Unlike most other impulse noise filters, the proposed SBF achieves high peak signal-to-noise ratio and great image quality by efficiently removing both types of mixed noise, salt-and-pepper with uniform noise and salt-and-pepper with Gaussian noise. In addition, the computational complexity of SBF is significantly less than that of other mixed noise filters.

  13. Condominium Design: Good and Bad Noise Control.

    ERIC Educational Resources Information Center

    Hargens, C. W.; Schutz, Victor K.

    This paper discusses pitfalls in condominium design and the incorpoation of related noise control problems into classroom situations. Two case studies are provided, and a list of architectural noise problems found in many condominiums is included. (CP)

  14. Construction noise decreases reproductive efficiency in mice.

    PubMed

    Rasmussen, Skye; Glickman, Gary; Norinsky, Rada; Quimby, Fred W; Tolwani, Ravi J

    2009-07-01

    Excessive noise is well known to impair rodent health. To better understand the effect of construction noise and to establish effective noise limits during a planned expansion of our vivarium, we analyzed the effects of construction noise on mouse gestation and neonatal growth. Our hypothesis was that high levels of construction noise would reduce the number of live births and retard neonatal growth. Female Swiss Webster mice were individually implanted with 15 B6CBAF1/J embryos and then exposed to 70- and 90-dBA concrete saw cutting noise samples at defined time points during gestation. In addition, groups of mice with litters were exposed to noise at 70, 80, or 90 dBA for 1 h daily during the first week after parturition. Litter size, birth weight, incidence of stillborn pups, and rate of neonatal weight gain were analyzed. Noise decreased reproductive efficiency by decreasing live birth rates and increasing the number of stillborn pups.

  15. Airframe Noise Studies: Review and Future Direction

    NASA Technical Reports Server (NTRS)

    Rackl, Robert G.; Miller, Gregory; Guo, Yueping; Yamamoto, Kingo

    2005-01-01

    This report contains the following information: 1) a review of airframe noise research performed under NASA's Advanced Subsonic Transport (AST) program up to the year 2000, 2) a comparison of the year 1992 airframe noise predictions with those using a year 2000 baseline, 3) an assessment of various airframe noise reduction concepts as applied to the year 2000 baseline predictions, and 4) prioritized recommendations for future airframe noise reduction work. NASA's Aircraft Noise Prediction Program was the software used for all noise predictions and assessments. For future work, the recommendations for the immediate future focus on the development of design tools sensitive to airframe noise treatment effects and on improving the basic understanding of noise generation by the landing gear as well as on its reduction.

  16. Impact of Air Injection on Jet Noise

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda; Norum, Tom

    2007-01-01

    The objective of this viewgraph presentation is to review the program to determine impact of core fluidic chevrons on noise produced by dual stream jets (i.e., broadband shock noise - supersonic, and mixing noise - subsonic and supersonic). The presentation reviews the sources of jet noise. It shows designs of Generation II Fluidic Chevrons. The injection impacts shock structure and stream disturbances through enhanced mixing. This may impact constructive interference between acoustic sources. The high fan pressures may inhibit mixing produced by core injectors. A fan stream injection may be required for better noise reduction. In future the modification of Gen II nozzles to allow for some azimuthal control: will allow for higher mass flow rates and will allow for shallower injection angles A Flow field study is scheduled for spring, 2008 The conclusions are that injection can reduce well-defined shock noise and injection reduces mixing noise near peak jet noise angle

  17. Helicopter impulsive noise: Theoretical and experimental status

    NASA Technical Reports Server (NTRS)

    Schmitz, F. H.; Yu, Y. H.

    1983-01-01

    The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanism is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanism of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory-experiment are suggested.

  18. Semiconductor Laser Low Frequency Noise Characterization

    NASA Technical Reports Server (NTRS)

    Maleki, Lute; Logan, Ronald T.

    1996-01-01

    This work summarizes the efforts in identifying the fundamental noise limit in semiconductor optical sources (lasers) to determine the source of 1/F noise and it's associated behavior. In addition, the study also addresses the effects of this 1/F noise on RF phased arrays. The study showed that the 1/F noise in semiconductor lasers has an ultimate physical limit based upon similar factors to fundamental noise generated in other semiconductor and solid state devices. The study also showed that both additive and multiplicative noise can be a significant detriment to the performance of RF phased arrays especially in regard to very low sidelobe performance and ultimate beam steering accuracy. The final result is that a noise power related term must be included in a complete analysis of the noise spectrum of any semiconductor device including semiconductor lasers.

  19. Annoyance caused by light aircraft noise

    SciTech Connect

    Not Available

    1981-03-01

    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.

  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. Noise Control in Space Shuttle Orbiter

    NASA Technical Reports Server (NTRS)

    Goodman, Jerry R.

    2009-01-01

    Acoustic limits in habitable space enclosures are required to ensure crew safety, comfort, and habitability. Noise control is implemented to ensure compliance with the acoustic requirements. The purpose of this paper is to describe problems with establishing acoustic requirements and noise control efforts, and present examples of noise control treatments and design applications used in the Space Shuttle Orbiter. Included is the need to implement the design discipline of acoustics early in the design process, and noise control throughout a program to ensure that limits are met. The use of dedicated personnel to provide expertise and oversight of acoustic requirements and noise control implementation has shown to be of value in the Space Shuttle Orbiter program. It is concluded that to achieve acceptable and safe noise levels in the crew habitable space, early resolution of acoustic requirements and implementation of effective noise control efforts are needed. Management support of established acoustic requirements and noise control efforts is essential.

  2. Survey of noise in coal preparation plants

    SciTech Connect

    Vipperman, J.S.; Bauer, E.R.; Babich, D.R.

    2007-01-15

    In response to the continuing problem of noise induced hearing loss (NIHL) among mine workers, the National Institute for Occupational Safety and Health (NIOSH) has conducted numerous noise surveys in coal preparation plants. The research, consisting of worker dose monitoring, task observations, and equipment noise profiling, was completed in eight separate preparation plants. Worker dose monitoring was conducted for three shifts in most cases. Workers experiencing higher than allowable doses were task-observed for one full shift to correlate dose to noise source(s). Finally, noise levels on all floors, and in lunch rooms and control rooms, were characterized. Results indicate that only workers who routinely spend a significant portion of their shift in the plants (away from the control rooms) are susceptible to overexposure from noise. Certain pieces of equipment (screens, centrifuges, sieve bends) are the loudest primary noise sources responsible for the worker noise exposures.

  3. Noise propagation in urban and industrial areas

    NASA Technical Reports Server (NTRS)

    Davies, H. G.

    1976-01-01

    Noise propagation in streets and the discrepancies between theoretical analyses and field measurements are discussed. A cell-model is used to estimate the general background level of noise due to vehicular sources distributed over the urban area.

  4. Interim prediction method for jet noise

    NASA Technical Reports Server (NTRS)

    Stone, J. R.

    1974-01-01

    A method is provided for predicting jet noise for a wide range of nozzle geometries and operating conditions of interest for aircraft engines. Jet noise theory, data and existing prediction methods was reviewed, and based on this information a interim method of jet noise prediction is proposed. Problem areas are idenified where further research is needed to improve the prediction method. This method predicts only the noise generated by the exhaust jets mixing with the surrounding air and does not include other noises emanating from the engine exhaust, such as combustion and machinery noise generated inside the engine (i.e., core noise). It does, however, include thrust reverser noise. Prediction relations are provided for conical nozzles, plug nozzles, coaxial nozzles and slot nozzles.

  5. Modeling phase noise in multifunction subassemblies.

    PubMed

    Driscoll, Michael

    2012-03-01

    Obtaining requisite phase noise performance in hardware containing multifunction circuitry requires accurate modeling of the phase noise characteristics of each signal path component, including both absolute (oscillator) and residual (non-oscillator) circuit contributors. This includes prediction of both static and vibration-induced phase noise. The model (usually in spreadsheet form) is refined as critical components are received and evaluated. Additive (KTBF) phase noise data can be reasonably estimated, based on device drive level and noise figure. However, accurate determination of component near-carrier (multiplicative) and vibration-induced noise usually must be determined via measurement. The model should also include the effects of noise introduced by IC voltage regulators and properly discriminate between common versus independent signal path residual noise contributors. The modeling can be easily implemented using a spreadsheet.

  6. Nighttime Airport Noise May Raise Heart Risks

    MedlinePlus

    ... More research needed to confirm that exposure to aircraft noise is the cause of health issues To ... 14, 2017 WEDNESDAY, June 14, 2017 (HealthDay News) -- Aircraft noise, particularly at night, may be linked to ...

  7. Electronic noise in a constant voltage anemometer

    NASA Astrophysics Data System (ADS)

    Weiss, Julien; Comte-Bellot, Geneviève

    2004-05-01

    The electronic noise and the signal-to-noise ratio in a constant voltage anemometer (CVA) are analyzed in terms of the main constitutive elements of the circuit. It is shown that the output voltage due to electronic noise decreases with the wire resistance, permitting one to know the noise upper limit by using the results of the unheated wire. The noise power spectrum increases at high frequencies as f2, like in other anemometers, because of the need to compensate for the thermal lag of the hot wire, thus leading to a reduced signal-to-noise ratio at high frequencies. Explicit formulas are given in terms of wire, CVA, and flow quantities. Measurements of electronic noise in a CVA prototype confirm the theoretical analysis and illustrate some interesting issues concerning measurements of noise and low levels of flow fluctuations.

  8. Airport Noise Tech Challenge Overview

    NASA Technical Reports Server (NTRS)

    Bridges, James

    2011-01-01

    The Supersonics Project, operating under NASA Aeronautics Mission Directorate#s Fundamental Aero Program, has been organized around the Technical Challenges that have historically precluded commercial supersonic flight. One of these Challenges is making aircraft that are capable of such high aerodynamic performance quiet enough around airports that they will not be objectionable. It is recognized that a successful civilian supersonic aircraft will be a system where many new technologies will come together, and for this to happen not only will new low noise propulsion concepts be required, but new engineering tools that predict the noise of the aircraft as these technologies are combined and compromised with the rest of the aircraft design. These are the two main objectives of the Airport Noise Tech Challenge. " ! As a Project in the Fundamental Aero Program, we work at a relatively low level of technology readiness. However, we have high level milestones which force us to integrate our efforts to impact systems-level activities. To keep the low-level work tied to delivering engineering tools and low-noise concepts, we have structured our milestones around development of the concepts and organized our activities around developing and applying our engineering tools to these concepts. The final deliverables in these milestones are noise prediction modules validated against the best embodiment of each concept. These will then be used in cross-disciplinary exercises to demonstrate the viability of aircraft designs to meet all the Technical Challenges. Some of the concepts being developed are shown: Fan Flow Diverters, Multi-jet Shielding, High-Aspect Ratio Embedded Nozzles, Plasma Actuated Instability Manipulation, Highly Variable Cycle Mixer- Ejectors, and Inverted Velocity Profiles. These concepts are being developed for reduced jet noise along with the design tools which describe how they perform when used in various aircraft configurations. Several key upcoming

  9. The annoyance caused by noise around airports

    NASA Technical Reports Server (NTRS)

    JOSSE

    1980-01-01

    A comprehensive study of noise around selected airports in France was performed. By use of questionnaires, the degree of annoyance caused by aircraft noise was determined. Three approaches used in the study were: (1) analytical study on the influence of noise on sleep; (2) sociological study on the satisfaction of occupants of buildings which conform to laws which are supposed to guarantee sufficient comfort; and (3) statistical study of correlations between external noises and psychological and pathological disturbances in residences.

  10. Shot noise suppression in avalanche photodiodes.

    PubMed

    Ma, Feng; Wang, Shuling; Campbell, Joe C

    2005-10-21

    We identify a new shot noise suppression mechanism in a thin (approximately 100 nm) heterostructure avalanche photodiode. In the low-gain regime the shot noise is suppressed due to temporal correlations within amplified current pulses. We demonstrate in a Monte Carlo simulation that the effective excess noise factors can be < 1, and reconcile the apparent conflict between theory and experiments. This shot noise suppression mechanism is independent of known mechanisms such as Coulomb interaction, or reflection at heterojunction interfaces.

  11. Acoustic noise during functional magnetic resonance imaging.

    PubMed

    Ravicz, M E; Melcher, J R; Kiang, N Y

    2000-10-01

    Functional magnetic resonance imaging (fMRI) enables sites of brain activation to be localized in human subjects. For studies of the auditory system, acoustic noise generated during fMRI can interfere with assessments of this activation by introducing uncontrolled extraneous sounds. As a first step toward reducing the noise during fMRI, this paper describes the temporal and spectral characteristics of the noise present under typical fMRI study conditions for two imagers with different static magnetic field strengths. Peak noise levels were 123 and 138 dB re 20 microPa in a 1.5-tesla (T) and a 3-T imager, respectively. The noise spectrum (calculated over a 10-ms window coinciding with the highest-amplitude noise) showed a prominent maximum at 1 kHz for the 1.5-T imager (115 dB SPL) and at 1.4 kHz for the 3-T imager (131 dB SPL). The frequency content and timing of the most intense noise components indicated that the noise was primarily attributable to the readout gradients in the imaging pulse sequence. The noise persisted above background levels for 300-500 ms after gradient activity ceased, indicating that resonating structures in the imager or noise reverberating in the imager room were also factors. The gradient noise waveform was highly repeatable. In addition, the coolant pump for the imager's permanent magnet and the room air-handling system were sources of ongoing noise lower in both level and frequency than gradient coil noise. Knowledge of the sources and characteristics of the noise enabled the examination of general approaches to noise control that could be applied to reduce the unwanted noise during fMRI sessions.

  12. Restaurant noise, hearing loss, and hearing aids.

    PubMed Central

    Lebo, C P; Smith, M F; Mosher, E R; Jelonek, S J; Schwind, D R; Decker, K E; Krusemark, H J; Kurz, P L

    1994-01-01

    Our multidisciplinary team obtained noise data in 27 San Francisco Bay Area restaurants. These data included typical minimum, peak, and average sound pressure levels; digital tape recordings; subjective noise ratings; and on-site unaided and aided speech discrimination tests. We report the details and implications of these noise measurements and provide basic information on selecting hearing aids and suggestions for coping with restaurant noise. Images PMID:7941506

  13. Effects of environmental noise on sleep.

    PubMed

    Hume, Kenneth I; Brink, Mark; Basner, Mathias

    2012-01-01

    This paper summarizes the findings from the past 3 year's research on the effects of environmental noise on sleep and identifies key future research goals. The past 3 years have seen continued interest in both short term effects of noise on sleep (arousals, awakenings), as well as epidemiological studies focusing on long term health impacts of nocturnal noise exposure. This research corroborated findings that noise events induce arousals at relatively low exposure levels, and independent of the noise source (air, road, and rail traffic, neighbors, church bells) and the environment (home, laboratory, hospital). New epidemiological studies support already existing evidence that night-time noise is likely associated with cardiovascular disease and stroke in the elderly. These studies collectively also suggest that nocturnal noise exposure may be more relevant for the genesis of cardiovascular disease than daytime noise exposure. Relative to noise policy, new effect-oriented noise protection concepts, and rating methods based on limiting awakening reactions were introduced. The publications of WHO's ''Night Noise Guidelines for Europe'' and ''Burden of Disease from Environmental Noise'' both stress the importance of nocturnal noise exposure for health and well-being. However, studies demonstrating a causal pathway that directly link noise (at ecological levels) and disturbed sleep with cardiovascular disease and/or other long term health outcomes are still missing. These studies, as well as the quantification of the impact of emerging noise sources (e.g., high speed rail, wind turbines) have been identified as the most relevant issues that should be addressed in the field on the effects of noise on sleep in the near future.

  14. Restaurant noise, hearing loss, and hearing aids.

    PubMed

    Lebo, C P; Smith, M F; Mosher, E R; Jelonek, S J; Schwind, D R; Decker, K E; Krusemark, H J; Kurz, P L

    1994-07-01

    Our multidisciplinary team obtained noise data in 27 San Francisco Bay Area restaurants. These data included typical minimum, peak, and average sound pressure levels; digital tape recordings; subjective noise ratings; and on-site unaided and aided speech discrimination tests. We report the details and implications of these noise measurements and provide basic information on selecting hearing aids and suggestions for coping with restaurant noise.

  15. Noise Control On Ships - Enabling Technologies

    DTIC Science & Technology

    2011-05-01

    Noise Induced Hearing Loss ( NIHL ) is described in this paper. Details are provided on existing and improved acoustic modeling tools that can be...warfighter performance. INTRODUCTION Navy personnel work and live in noise levels that put them at risk for Noise Induced Hearing Loss ( NIHL ) and...Navy‟s risk for NIHL /tinnitus and improve the noise environment on naval vessels. Hearing loss/tinnitus (ringing in the ears) poses a particular

  16. 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.

  17. 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.

  18. Wind noise under a pine tree canopy.

    PubMed

    Raspet, Richard; Webster, Jeremy

    2015-02-01

    It is well known that infrasonic wind noise levels are lower for arrays placed in forests and under vegetation than for those in open areas. In this research, the wind noise levels, turbulence spectra, and wind velocity profiles are measured in a pine forest. A prediction of the wind noise spectra from the measured meteorological parameters is developed based on recent research on wind noise above a flat plane. The resulting wind noise spectrum is the sum of the low frequency wind noise generated by the turbulence-shear interaction near and above the tops of the trees and higher frequency wind noise generated by the turbulence-turbulence interaction near the ground within the tree layer. The convection velocity of the low frequency wind noise corresponds to the wind speed above the trees while the measurements showed that the wind noise generated by the turbulence-turbulence interaction is near stationary and is generated by the slow moving turbulence adjacent to the ground. Comparison of the predicted wind noise spectrum with the measured wind noise spectrum shows good agreement for four measurement sets. The prediction can be applied to meteorological estimates to predict the wind noise under other pine forests.

  19. Modeling Noise in Geared Transmission Systems

    NASA Astrophysics Data System (ADS)

    Subrahmanyam, C. V. S. R.

    2010-11-01

    Noise is an unwanted sound that affects human and environment if not controlled properly. In the present article an effort is made to reduce noise in geared transmission systems by modeling noise. Numerical solution methods are suggested at the end. Energy considerations in geared transmissions are discussed.

  20. Noise Level Determination in Forestry Machines

    Treesearch

    Fernando Seixas; Rafael Alex Barbosa; Robert Rummer

    1999-01-01

    Until recently, the high noise level of many forestry machines presented an occupational risk of hearing loss for operators exposed over a long period of time. This is a serious health and, occupational safety problem, with different. regulations in various countries concerning noise levels and exposure time allowed. This study evaluated the noise level of sixteen...

  1. 14 CFR 36.1103 - Noise limits.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Noise limits. 36.1103 Section 36.1103 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS CERTIFICATION Tiltrotors § 36.1103 Noise limits. (a) Compliance with the...

  2. 14 CFR 36.801 - Noise measurement.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Noise measurement. 36.801 Section 36.801 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS CERTIFICATION Helicopters § 36.801 Noise measurement. For primary, normal...

  3. 14 CFR 36.103 - Noise limits.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Noise limits. 36.103 Section 36.103 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT NOISE STANDARDS... Noise limits. (a) For subsonic transport category large airplanes and subsonic jet airplanes compliance...

  4. 14 CFR 36.501 - Noise limits.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Noise limits. 36.501 Section 36.501 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT NOISE STANDARDS..., Commuter Category Airplanes § 36.501 Noise limits. (a) Compliance with this subpart must be shown for— (1...

  5. 14 CFR 36.103 - Noise limits.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Noise limits. 36.103 Section 36.103 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT NOISE STANDARDS... Noise limits. (a) For subsonic transport category large airplanes and subsonic jet airplanes compliance...

  6. Classroom Noise and Teachers' Voice Production

    ERIC Educational Resources Information Center

    Rantala, Leena M.; Hakala, Suvi; Holmqvist, Sofia; Sala, Eeva

    2015-01-01

    Purpose: The aim of this study was to research the associations between noise (ambient and activity noise) and objective metrics of teachers' voices in real working environments (i.e., classrooms). Method: Thirty-two female and 8 male teachers from 14 elementary schools were randomly selected for the study. Ambient noise was measured during breaks…

  7. 14 CFR 36.501 - Noise limits.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Noise limits. 36.501 Section 36.501 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT NOISE STANDARDS..., Commuter Category Airplanes § 36.501 Noise limits. (a) Compliance with this subpart must be shown for— (1...

  8. 14 CFR 36.501 - Noise limits.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Noise limits. 36.501 Section 36.501 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT NOISE STANDARDS..., Commuter Category Airplanes § 36.501 Noise limits. (a) Compliance with this subpart must be shown for— (1...

  9. 14 CFR 36.805 - Noise limits.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Noise limits. 36.805 Section 36.805 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS CERTIFICATION Helicopters § 36.805 Noise limits. (a) Compliance with the...

  10. 14 CFR 36.103 - Noise limits.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Noise limits. 36.103 Section 36.103 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT NOISE STANDARDS... Noise limits. (a) For subsonic transport category large airplanes and subsonic jet airplanes compliance...

  11. 14 CFR 36.805 - Noise limits.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Noise limits. 36.805 Section 36.805 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS CERTIFICATION Helicopters § 36.805 Noise limits. (a) Compliance with the...

  12. 14 CFR 36.801 - Noise measurement.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Noise measurement. 36.801 Section 36.801 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS CERTIFICATION Helicopters § 36.801 Noise measurement. For primary, normal...

  13. 14 CFR 36.801 - Noise measurement.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Noise measurement. 36.801 Section 36.801 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS CERTIFICATION Helicopters § 36.801 Noise measurement. For primary, normal...

  14. 14 CFR 36.805 - Noise limits.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Noise limits. 36.805 Section 36.805 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS CERTIFICATION Helicopters § 36.805 Noise limits. (a) Compliance with the...

  15. Combustion and Engine-Core Noise

    NASA Astrophysics Data System (ADS)

    Ihme, Matthias

    2017-01-01

    The implementation of advanced low-emission aircraft engine technologies and the reduction of noise from airframe, fan, and jet exhaust have made noise contributions from an engine core increasingly important. Therefore, meeting future ambitious noise-reduction goals requires the consideration of engine-core noise. This article reviews progress on the fundamental understanding, experimental analysis, and modeling of engine-core noise; addresses limitations of current techniques; and identifies opportunities for future research. After identifying core-noise contributions from the combustor, turbomachinery, nozzles, and jet exhaust, they are examined in detail. Contributions from direct combustion noise, originating from unsteady combustion, and indirect combustion noise, resulting from the interaction of flow-field perturbations with mean-flow variations in turbine stages and nozzles, are analyzed. A new indirect noise-source contribution arising from mixture inhomogeneities is identified by extending the theory. Although typically omitted in core-noise analysis, the impact of mean-flow variations and nozzle-upstream perturbations on the jet-noise modulation is examined, providing potential avenues for future core-noise mitigation.

  16. Communication system with adaptive noise suppression

    NASA Technical Reports Server (NTRS)

    Kozel, David (Inventor); Devault, James A. (Inventor); Birr, Richard B. (Inventor)

    2007-01-01

    A signal-to-noise ratio dependent adaptive spectral subtraction process eliminates noise from noise-corrupted speech signals. The process first pre-emphasizes the frequency components of the input sound signal which contain the consonant information in human speech. Next, a signal-to-noise ratio is determined and a spectral subtraction proportion adjusted appropriately. After spectral subtraction, low amplitude signals can be squelched. A single microphone is used to obtain both the noise-corrupted speech and the average noise estimate. This is done by determining if the frame of data being sampled is a voiced or unvoiced frame. During unvoiced frames an estimate of the noise is obtained. A running average of the noise is used to approximate the expected value of the noise. Spectral subtraction may be performed on a composite noise-corrupted signal, or upon individual sub-bands of the noise-corrupted signal. Pre-averaging of the input signal's magnitude spectrum over multiple time frames may be performed to reduce musical noise.

  17. Noise Reduction in an Undergraduate Library.

    ERIC Educational Resources Information Center

    Bird, Charles P.; Puglisi, Dawn D.

    1984-01-01

    Reports on program initiated to reduce noise in undergraduate library through combination of space reallocation, rule changes, and staff monitoring of noise. Objective and subjective measures of noise (sound-level readings, preintervention and postintervention questionnaires) and results of intervention program are discussed. Memo distributed on…

  18. Classroom Noise and Teachers' Voice Production

    ERIC Educational Resources Information Center

    Rantala, Leena M.; Hakala, Suvi; Holmqvist, Sofia; Sala, Eeva

    2015-01-01

    Purpose: The aim of this study was to research the associations between noise (ambient and activity noise) and objective metrics of teachers' voices in real working environments (i.e., classrooms). Method: Thirty-two female and 8 male teachers from 14 elementary schools were randomly selected for the study. Ambient noise was measured during breaks…

  19. Prediction and reduction of rotor broadband noise

    NASA Technical Reports Server (NTRS)

    Hayden, R. E.; Aravamudan, K. S.

    1978-01-01

    Prediction techniques which can be or have been applied to subsonic rotors, and methods for designing helicopter rotors for reduced broadband noise generation are summarized. It is shown how detailed physical models of the noise source can be used to identify approaches to noise control.

  20. Correlated noise in a logistic growth model

    NASA Astrophysics Data System (ADS)

    Ai, Bao-Quan; Wang, Xian-Ju; Liu, Guo-Tao; Liu, Liang-Gang

    2003-02-01

    The logistic differential equation is used to analyze cancer cell population, in the presence of a correlated Gaussian white noise. We study the steady state properties of tumor cell growth and discuss the effects of the correlated noise. It is found that the degree of correlation of the noise can cause tumor cell extinction.

  1. Noise Levels in the Operating Room

    DTIC Science & Technology

    2001-10-01

    59-63. Hodge, B., & Thompson , J . F . (1990). Noise pollution in the operating theatre. The Lancet, 335, 891-894. Noise Levels 41...Kam, P. C. A., Kam A. C., & Thompson , J . F . (1994). Noise pollution in the anaesthetic and intensive care environment. Anaesthesia, 49, 982-986

  2. Noise-induced stabilization in population dynamics.

    PubMed

    Parker, Matthew; Kamenev, Alex; Meerson, Baruch

    2011-10-28

    We investigate a model in which strong noise in a subpopulation creates a metastable state in an otherwise unstable two-population system. The induced metastable state is vortexlike, and its persistence time grows exponentially with the noise strength. A variety of distinct scaling relations are observed depending on the relative strength of the subpopulation noises.

  3. Noise canceling in-situ detection

    DOEpatents

    Walsh, David O.

    2014-08-26

    Technologies applicable to noise canceling in-situ NMR detection and imaging are disclosed. An example noise canceling in-situ NMR detection apparatus may comprise one or more of a static magnetic field generator, an alternating magnetic field generator, an in-situ NMR detection device, an auxiliary noise detection device, and a computer.

  4. Using noise to shape motor learning.

    PubMed

    Thorp, Elias B; Kording, Konrad P; Mussa-Ivaldi, Ferdinando A

    2017-02-01

    Each of our movements is selected from any number of alternative movements. Some studies have shown evidence that the central nervous system (CNS) chooses to make the specific movements that are least affected by motor noise. Previous results showing that the CNS has a natural tendency to minimize the effects of noise make the direct prediction that if the relationship between movements and noise were to change, the specific movements people learn to make would also change in a predictable manner. Indeed, this has been shown for well-practiced movements such as reaching. Here, we artificially manipulated the relationship between movements and visuomotor noise by adding noise to a motor task in a novel redundant geometry such that there arose a single control policy that minimized the noise. This allowed us to see whether, for a novel motor task, people could learn the specific control policy that minimized noise or would need to employ other compensation strategies to overcome the added noise. As predicted, subjects were able to learn movements that were biased toward the specific ones that minimized the noise, suggesting not only that the CNS can learn to minimize the effects of noise in a novel motor task but also that artificial visuomotor noise can be a useful tool for teaching people to make specific movements. Using noise as a teaching signal promises to be useful for rehabilitative therapies and movement training with human-machine interfaces.

  5. Psychophysical measurement of night vision goggle noise

    NASA Astrophysics Data System (ADS)

    Glasgow, Rachael L.; Marasco, Peter L.; Havig, Paul R.; Martinsen, Gary L.; Reis, George A.; Heft, Eric L.

    2003-09-01

    Pilots, developers, and other users of night-vision goggles (NVGs) have pointed out that different NVG image intensifier tubes have different subjective noise characteristics. Currently, no good model of the visual impact of NVG noise exists. Because it is very difficult to objectively measure the noise of a NVG, a method for assessing noise subjectively using simple psychophysical procedures was developed. This paper discusses the use of a computer program to generate noise images similar to what an observer sees through an NVG, based on filtered white noise. The images generated were based on 1/f (where f is frequency) filtered white noise with several adjustable parameters. Adjusting each of these parameters varied different characteristics of the noise. This paper discusses a study where observers compared the computer-generated noise images to true NVG noise and were asked to determine which computer-generated image was the best representation of the true noise. This method was repeated with different types of NVGs and at different luminance levels to study what NVG parameters cause variations in NVG noise.

  6. 14 CFR 36.103 - Noise limits.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Noise limits. 36.103 Section 36.103... Noise limits. (a) For subsonic transport category large airplanes and subsonic jet airplanes compliance... greater than the Stage 3 noise limit prescribed in section B36.5(c) of appendix B of this part. (c) Type...

  7. 14 CFR 36.103 - Noise limits.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Noise limits. 36.103 Section 36.103... Noise limits. (a) For subsonic transport category large airplanes and subsonic jet airplanes compliance... greater than the Stage 3 noise limit prescribed in section B36.5(c) of appendix B of this part. (c) Type...

  8. 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.

  9. Noise suppressing capillary separation system

    DOEpatents

    Yeung, E.S.; Xue, Y.

    1996-07-30

    A noise-suppressing capillary separation system for detecting the real-time presence or concentration of an analyte in a sample is provided. The system contains a capillary separation means through which the analyte is moved, a coherent light source that generates a beam which is split into a reference beam and a sample beam that irradiate the capillary, and a detector for detecting the reference beam and the sample beam light that transmits through the capillary. The laser beam is of a wavelength effective to be absorbed by a chromophore in the capillary. The system includes a noise suppressing system to improve performance and accuracy without signal averaging or multiple scans. 13 figs.

  10. 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.

  11. Quantum Noise in Laser Diodes

    NASA Technical Reports Server (NTRS)

    Giacobino, E.; Marin, F.; Bramati, A.; Jost, V.; Poizat, J. Ph.; Roch, J.-F.; Grangier, P.; Zhang, T.-C.

    1996-01-01

    We have investigated the intensity noise of single mode laser diodes, either free-running or using different types of line narrowing techniques at room temperature. We have measured an intensity squeezing of 1.2 dB with grating-extended cavity lasers and 1.4 dB with injection locked lasers (respectively 1.6 dB and 2.3 dB inferred at the laser output). We have observed that the intensity noise of a free-running nominally single mode laser diode results from a cancellation effect between large anti-correlated fluctuations of the main mode and of weak longitudinal side modes. Reducing the side modes by line narrowing techniques results in intensity squeezing.

  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. Advances in Barkhausen noise analysis

    NASA Astrophysics Data System (ADS)

    Meyendorf, Norbert; Hillmann, Susanne; Cikalova, Ulana; Schreiber, Juergen

    2014-03-01

    The magnetic Barkhausen Noise technique is a well suited method for the characterization of ferromagnetic materials. The Barkhausen effect results in an interaction between the magnetic structure and the microstructure of materials, and is sensitive to the stresses and microstructure related mechanical properties. Barkhausen noise is a complex signal that provides a large amount of information, for example frequency spectrum, amplitude, RMS value, dependence of magnetic field strength, magnetization frequency and fractal behavior. Although this technique has a lot potentials, it is not commonly used in nondestructive material testing. Large sensors and complex calibration procedures made the method impractical for many applications. However, research has progressed in recent years; new sensor designs were developed and evaluated, new algorithms to simplify the calibration and measurement procedures were developed as well as analysis of additional material properties have been introduced.

  14. Noise Generation in Hot Jets

    NASA Technical Reports Server (NTRS)

    Khavaran, Abbas; Kenzakowski, Donald C.

    2007-01-01

    A prediction method based on the generalized acoustic analogy is presented, and used to evaluate aerodynamic noise radiated from high speed hot jets. The set of Euler equations are split into their respective non-radiating and residual components. Under certain conditions, the residual equations are rearranged to form a wave equation. This equation consists of a third-order wave operator, plus a number of nonlinear terms that are identified with the equivalent sources of sound and their statistical characteristics are modeled. A specialized RANS solver provides the base flow as well as turbulence quantities and temperature fluctuations that determine the source strength. The main objective here is to evaluate the relative contribution from various source elements to the far-field spectra and to show the significance of temperature fluctuations as a source of aerodynamic noise in hot jets.

  15. Noise Reduction Through Circulation Control

    NASA Technical Reports Server (NTRS)

    Munro, Scott E.; Ahuja, K. K.; Englar, Robert J.

    2005-01-01

    Circulation control technology uses tangential blowing around a rounded trailing edge or a leading edge to change the force and moment characteristics of an aerodynamic body. This technology has been applied to circular cylinders, wings, helicopter rotors, and even to automobiles for improved aerodynamic performance. Only limited research has been conducted on the acoustic of this technology. Since wing flaps contribute to the environmental noise of an aircraft, an alternate blown high lift system without complex mechanical flaps could prove beneficial in reducing the noise of an approaching aircraft. Thus, in this study, a direct comparison of the acoustic characteristics of high lift systems employing a circulation control wing configuration and a conventional wing flapped configuration has been made. These results indicate that acoustically, a circulation control wing high lift system could be considerably more acceptable than a wing with conventional mechanical flaps.

  16. Low-noise pulse conditioner

    DOEpatents

    Bird, D.A.

    1981-06-16

    A low-noise pulse conditioner is provided for driving electronic digital processing circuitry directly from differentially induced input pulses. The circuit uses a unique differential-to-peak detector circuit to generate a dynamic reference signal proportional to the input peak voltage. The input pulses are compared with the reference signal in an input network which operates in full differential mode with only a passive input filter. This reduces the introduction of circuit-induced noise, or jitter, generated in ground referenced input elements normally used in pulse conditioning circuits, especially speed transducer processing circuits. This circuit may be used for conditioning the sensor signal from the Fidler coil in a gas centrifuge for separation of isotopic gaseous mixtures.

  17. Noise exposure in marching bands

    NASA Astrophysics Data System (ADS)

    Keefe, Joseph

    2005-09-01

    Previous studies involving orchestras have shown that music ensembles can produce hazardous noise levels. There are no similar data for marching bands and pep bands. In order to evaluate the noise levels produced by marching and pep bands, 1/3-octave-band sound-pressure levels were measured while these groups rehearsed and performed. Data were collected while marching with the bands to ensure a realistic environment. Comparing these data to OSHA and NIOSH criteria, marching and pep band exposures often exceed safe values. For typical exposures, OSHA doses range from 11% to 295%, while NIOSH doses range from 35% to 3055%. Exposures that would be considered hazardous in the workplace are common in marching and pep bands; students and band directors should take steps to recognize the risk posed by various instruments and various locations, and should implement hearing conservation efforts.

  18. Noise in laser oscillator systems

    NASA Technical Reports Server (NTRS)

    Hafele, Joseph C.

    1990-01-01

    The aim of the SUNLITE program is to demonstrate the performance of ultra-stable laser systems in the environment of space. The program uses Non-Planar Ring Oscillators (NPRO) which have shown great promise for time and frequency standards with unprecedented resolution and stability. An immediate goal is to test NPRO oscillators in orbital free fall by 1994. During the past year there was remarkable progress in the design and pre-flight testing of the SUNLITE test package. Current theoretical studies are investigating the possible effects of various noise sources on the linewidth and linecenter frequency stability of servocontrolled NPRO lasers. The frequency control system is reviewed and the potential impact on frequency stability of noise sources in the control system and in the environment is considered.

  19. Numerical simulation of jet noise

    NASA Astrophysics Data System (ADS)

    Paliath, Umesh

    In the present work, computational aeroacoustics and parallel computers are used to conduct a study of flow-induced noise from different jet nozzle geometries. The nozzle is included as part of the computational domain. This is important to predict jet noise from nozzles associated with military aircraft engines. The Detached Eddy Simulation (DES) approach is used to simulate both the jet nozzle internal and external flows as well as the jet plume. This methodology allows the turbulence model to transition from an unsteady Reynolds Averaged Navier-Stokes (URANS) method for attached boundary layers to a Large Eddy Simulation (LES) in separated regions. Thus, it is ideally suited to jet flow simulations where the nozzle is included. Both cylindrical polar and Cartesian coordinate systems are used. A spectral method is used to avoid the centerline singularity when using the cylindrical coordinate system. The one equation Spalart-Allmaras turbulence model, in DES mode, is used to describe the evolution of the turbulent eddy viscosity. An explicit 4th order Runge-Kutta time marching scheme is used. For spatial discritization the Dispersion Relation Preserving scheme(DRP) is used. The farfield sound is evaluated using the Ffowcs Williams-Hawkings permeable surface wave extrapolation method. This permits the noise to be predicted at large distances from the jet based on fluctuations in the jets near field. The present work includes a study of the effect of different nozzle geometries such as axisymmetric/non-axisymmetric and planar/non-planar exits on the far field noise predictions. Also the effect of operating conditions such as a heated/unheated jet, the effect of forward flight, a jet flow at an angle of attack, and the effect of a supersonic exit Mach number, are included in the study.

  20. The Human Brain Uses Noise

    NASA Astrophysics Data System (ADS)

    Mori, Toshio; Kai, Shoichi

    2003-05-01

    We present the first observation of stochastic resonance (SR) in the human brain's visual processing area. The novel experimental protocol is to stimulate the right eye with a sub-threshold periodic optical signal and the left eye with a noisy one. The stimuli bypass sensory organs and are mixed in the visual cortex. With many noise sources present in the brain, higher brain functions, e.g. perception and cognition, may exploit SR.

  1. 75 FR 11990 - Chicago Executive Airports Noise Exposure Map Approval and Noise Compatibility Program Review

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-12

    ... of specific properties to noise exposure contours depicted on a noise exposure map submitted under... relative locations of specific properties with regard to the depicted noise contours, or in interpreting... responsibility for the detailed overlaying of noise exposure contours onto the map depicting properties on...

  2. 78 FR 19355 - Noise Exposure Map Notice: Receipt of Noise Compatibility Program and Request for Review

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-29

    ... Exposure Contour, page 3-3. Exhibit 3-2: Future (2017) Baseline Noise Exposure Contour, page 3- 7. The FAA... of specific properties to noise exposure contours depicted on a noise exposure map submitted under... relative locations of specific properties with regard to the depicted noise contours, or in...

  3. Fighting noise with noise: Where the contest stands for powerplant applications

    SciTech Connect

    O'Keefe, W.

    1994-07-01

    This article examines the use of active noise cancellation in power plant applications. The article examines the basic concepts of active noise cancellation, types of controls and generators for the canceling noise, economic trade-off, noise regulations, working conditions and impact to employees, demonstration projects and commercial applications.

  4. Visibility of wavelet quantization noise

    NASA Technical Reports Server (NTRS)

    Watson, A. B.; Yang, G. Y.; Solomon, J. A.; Villasenor, J.

    1997-01-01

    The discrete wavelet transform (DWT) decomposes an image into bands that vary in spatial frequency and orientation. It is widely used for image compression. Measures of the visibility of DWT quantization errors are required to achieve optimal compression. Uniform quantization of a single band of coefficients results in an artifact that we call DWT uniform quantization noise; it is the sum of a lattice of random amplitude basis functions of the corresponding DWT synthesis filter. We measured visual detection thresholds for samples of DWT uniform quantization noise in Y, Cb, and Cr color channels. The spatial frequency of a wavelet is r 2-lambda, where r is display visual resolution in pixels/degree, and lambda is the wavelet level. Thresholds increase rapidly with wavelet spatial frequency. Thresholds also increase from Y to Cr to Cb, and with orientation from lowpass to horizontal/vertical to diagonal. We construct a mathematical model for DWT noise detection thresholds that is a function of level, orientation, and display visual resolution. This allows calculation of a "perceptually lossless" quantization matrix for which all errors are in theory below the visual threshold. The model may also be used as the basis for adaptive quantization schemes.

  5. Visibility of Wavelet Quantization Noise

    NASA Technical Reports Server (NTRS)

    Watson, Andrew B.; Yang, Gloria Y.; Solomon, Joshua A.; Villasenor, John; Null, Cynthia H. (Technical Monitor)

    1995-01-01

    The Discrete Wavelet Transform (DWT) decomposes an image into bands that vary in spatial frequency and orientation. It is widely used for image compression. Measures of the visibility of DWT quantization errors are required to achieve optimal compression. Uniform quantization of a single band of coefficients results in an artifact that is the sum of a lattice of random amplitude basis functions of the corresponding DWT synthesis filter, which we call DWT uniform quantization noise. We measured visual detection thresholds for samples of DWT uniform quantization noise in Y, Cb, and Cr color channels. The spatial frequency of a wavelet is r 2(exp)-L , where r is display visual resolution in pixels/degree, and L is the wavelet level. Amplitude thresholds increase rapidly with spatial frequency. Thresholds also increase from Y to Cr to Cb, and with orientation from low-pass to horizontal/vertical to diagonal. We describe a mathematical model to predict DWT noise detection thresholds as a function of level, orientation, and display visual resolution. This allows calculation of a "perceptually lossless" quantization matrix for which all errors are in theory below the visual threshold. The model may also be used as the basis for adaptive quantization schemes.

  6. Modelling seismic noise body waves

    NASA Astrophysics Data System (ADS)

    Stutzmann, Éléonore; Gualtieri, Lucia; Farra, Veronique; Capdeville, Yann; Schimmel, Martin; Ardhuin, Fabrice; Morelli, Andrea

    2014-05-01

    Secondary microseismic noise is generated by non-linear interactions between ocean waves at the ocean surface. We present the theory for computing the site effect of the ocean layer upon body waves generated by noise sources distributed along the ocean surface. We show that the ocean site effect can be described as the constructive interference of multiply reflected P-waves in the ocean that are then converted to either P-waves or SV-waves at the ocean-crust interface.The site effect varies strongly with period and ocean depth and that it is is stronger for P-waves than for S-waves. We validate our computation by comparing the theoretical noise body-wave sources with the sources inferred from beamforming analysis of the three seismogram components recorded by the Southern California Seismic Network. We use rotated traces for the beamforming analysis, and we show that we clearly detect P-waves generated by ocean gravity wave interactions along the track of typhoon Ioke (September 2006). We model the variability of the recorded P-waves associated with the typhon. We do not detect the corresponding SV-waves, and we demonstrate that this is because their amplitude is too weak to be detected.

  7. NASA Open Rotor Noise Research

    NASA Technical Reports Server (NTRS)

    Envia, Ed

    2010-01-01

    Owing to their inherent fuel burn efficiency advantage compared with the current generation high bypass ratio turbofan engines, there is resurgent interest in developing open rotor propulsion systems for powering the next generation commercial aircraft. However, to make open rotor systems truly competitive, they must be made to be acoustically acceptable too. To address this challenge, NASA in collaboration with industry is exploring the design space for low-noise open rotor propulsion systems. The focus is on the system level assessment of the open rotors compared with other candidate concepts like the ultra high bypass ratio cycle engines. To that end there is an extensive research effort at NASA focused on component testing and diagnostics of the open rotor acoustic performance as well as assessment and improvement of open rotor noise prediction tools. In this presentation and overview of the current NASA research on open rotor noise will be provided. Two NASA projects, the Environmentally Responsible Aviation Project and the Subsonic Fixed Wing Project, have been funding this research effort.

  8. How Synchronization Protects from Noise

    PubMed Central

    Tabareau, Nicolas; Slotine, Jean-Jacques; Pham, Quang-Cuong

    2010-01-01

    The functional role of synchronization has attracted much interest and debate: in particular, synchronization may allow distant sites in the brain to communicate and cooperate with each other, and therefore may play a role in temporal binding, in attention or in sensory-motor integration mechanisms. In this article, we study another role for synchronization: the so-called “collective enhancement of precision”. We argue, in a full nonlinear dynamical context, that synchronization may help protect interconnected neurons from the influence of random perturbations—intrinsic neuronal noise—which affect all neurons in the nervous system. More precisely, our main contribution is a mathematical proof that, under specific, quantified conditions, the impact of noise on individual interconnected systems and on their spatial mean can essentially be cancelled through synchronization. This property then allows reliable computations to be carried out even in the presence of significant noise (as experimentally found e.g., in retinal ganglion cells in primates). This in turn is key to obtaining meaningful downstream signals, whether in terms of precisely-timed interaction (temporal coding), population coding, or frequency coding. Similar concepts may be applicable to questions of noise and variability in systems biology. PMID:20090826

  9. Feature-Preserving Noise Removal.

    PubMed

    Youssef, Khalid; Jarenwattananon, Nanette N; Bouchard, Louis-S

    2015-09-01

    Conventional image restoration algorithms use transform-domain filters, which separate the noise from the sparse signal among the transform components or apply spatial smoothing filters in real space whose design relies on prior assumptions about the noise statistics. These filters also reduce the information content of the image by suppressing spatial frequencies or by recognizing only a limited set of shapes. Here we show that denoising can be efficiently done using a nonlinear filter, which operates along patch neighborhoods and multiple copies of the original image. The use of patches enables the algorithm to account for spatial correlations in the random field whereas the multiple copies are used to recognize the noise statistics. The nonlinear filter, which is implemented by a hierarchical multistage system of multilayer perceptrons, outperforms state-of-the-art denoising algorithms such as those based on collaborative filtering and total variation. Compared to conventional denoising algorithms, our filter can restore images without blurring them, making it attractive for use in medical imaging where the preservation of anatomical details is critical.

  10. Visibility of Wavelet Quantization Noise

    NASA Technical Reports Server (NTRS)

    Watson, Andrew B.; Yang, Gloria Y.; Solomon, Joshua A.; Villasenor, John; Null, Cynthia H. (Technical Monitor)

    1995-01-01

    The Discrete Wavelet Transform (DWT) decomposes an image into bands that vary in spatial frequency and orientation. It is widely used for image compression. Measures of the visibility of DWT quantization errors are required to achieve optimal compression. Uniform quantization of a single band of coefficients results in an artifact that is the sum of a lattice of random amplitude basis functions of the corresponding DWT synthesis filter, which we call DWT uniform quantization noise. We measured visual detection thresholds for samples of DWT uniform quantization noise in Y, Cb, and Cr color channels. The spatial frequency of a wavelet is r 2(exp)-L , where r is display visual resolution in pixels/degree, and L is the wavelet level. Amplitude thresholds increase rapidly with spatial frequency. Thresholds also increase from Y to Cr to Cb, and with orientation from low-pass to horizontal/vertical to diagonal. We describe a mathematical model to predict DWT noise detection thresholds as a function of level, orientation, and display visual resolution. This allows calculation of a "perceptually lossless" quantization matrix for which all errors are in theory below the visual threshold. The model may also be used as the basis for adaptive quantization schemes.

  11. Comparison of Ising spin glass noise to flux and inductance noise in SQUIDs.

    PubMed

    Chen, Zhi; Yu, Clare C

    2010-06-18

    Recent experiments implicate spins on the surface of metals as the source of flux and inductance noise in SQUIDs. We present Monte Carlo simulations of 2D and 3D Ising spin glasses that produce magnetization noise S(M) consistent with flux noise. At low frequencies S(M) is a maximum at the critical temperature T(C) in three dimensions, implying that flux noise should be a maximum at T(C). The second spectra of the magnetization noise and the noise in the susceptibility are consistent with experimentally measured SQUID inductance noise.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1995-04-01

    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.

  14. Noise Exposure Assessment in a Dental School

    PubMed Central

    Kaimook, Wandee; Tantisarasart, Ratchada; Sooksamear, Puwanai; Chayaphum, Satith; Kongkamol, Chanon; Srisintorn, Wisarut; Phakthongsuk, Pitchaya

    2011-01-01

    Objectives This cross-sectional study was performed in the Dental School of Prince of Songkla University to ascertain noise exposure of dentists, dental assistants, and laboratory technicians. A noise spectral analysis was taken to illustrate the spectra of dental devices. Methods A noise evaluation was performed to measure the noise level at dental clinics and one dental laboratory from May to December 2010. Noise spectral data of dental devices were taken during dental practices at the dental services clinic and at the dental laboratory. A noise dosimeter was set following the Occupational Safety and Health Administration criteria and then attached to the subjects' collar to record personal noise dose exposure during working periods. Results The peaks of the noise spectrum of dental instruments were at 1,000, 4,000, and 8,000 Hz which depended on the type of instrument. The differences in working areas and job positions had an influence on the level of noise exposure (p < 0.01). Noise measurement in the personal hearing zone found that the laboratory technicians were exposed to the highest impulsive noise levels (137.1 dBC). The dentists and dental assistants who worked at a pedodontic clinic had the highest percent noise dose (4.60 ± 3.59%). In the working areas, the 8-hour time-weighted average of noise levels ranged between 49.7-58.1 dBA while the noisiest working area was the dental laboratory. Conclusion Dental personnel are exposed to noise intensities lower than occupational exposure limits. Therefore, these dental personnel may not experience a noise-induced hearing loss. PMID:22953219

  15. Noise

    MedlinePlus

    ... traffic on a busy street. Listening to loud music, especially on headphones, is a common cause of ... by Keeping the volume down when listening to music Wearing earplugs when using loud equipment NIH: National ...

  16. Noise.

    DTIC Science & Technology

    1983-09-01

    sample paths. Unfortunately, the Wiener process sample paths are of bounded variation with probability zero and all the physical sample paths are of... bounded variation . Thus non-linear filtering theory cannot be applied in practice unless we are able to choose a particular version of the conditional

  17. Comparison of predicted engine core noise with proposed FAA helicopter noise certification requirements

    NASA Technical Reports Server (NTRS)

    Vonglahn, U.; Groesbeck, D. E.

    1981-01-01

    Calculated engine core noise levels, based on NASA-Lewis prediction procedures, for five representative helicopter engines are compared with measured total helicopter noise levels and proposed FAA helicopter noise certification requirements. Comparisons are made for level flyover and approach procedures. The measured noise levels are generally significantly greater than those predicted for the core noise levels, except for Sikorsky S-61 and S-64 helicopters. However, the predicted engine core noise levels are generally at or within 3 db of the proposed FAA noise rules. Consequently, helicopter engine core noise can be a significant contributor to the overall helicopter noise signature and, at this time, will provide a limiting floor to a further decrease in future noise regulations.

  18. Background Noise Reduction Using Adaptive Noise Cancellation Determined by the Cross-Correlation

    NASA Technical Reports Server (NTRS)

    Spalt, Taylor B.; Brooks, Thomas F.; Fuller, Christopher R.

    2012-01-01

    Background noise due to flow in wind tunnels contaminates desired data by decreasing the Signal-to-Noise Ratio. The use of Adaptive Noise Cancellation to remove background noise at measurement microphones is compromised when the reference sensor measures both background and desired noise. The technique proposed modifies the classical processing configuration based on the cross-correlation between the reference and primary microphone. Background noise attenuation is achieved using a cross-correlation sample width that encompasses only the background noise and a matched delay for the adaptive processing. A present limitation of the method is that a minimum time delay between the background noise and desired signal must exist in order for the correlated parts of the desired signal to be separated from the background noise in the crosscorrelation. A simulation yields primary signal recovery which can be predicted from the coherence of the background noise between the channels. Results are compared with two existing methods.

  19. Development of Jet Noise Power Spectral Laws

    NASA Technical Reports Server (NTRS)

    Khavaran, Abbas; Bridges, James

    2011-01-01

    High-quality jet noise spectral data measured at the Aero-Acoustic Propulsion Laboratory (AAPL) at NASA Glenn is used to develop jet noise scaling laws. A FORTRAN algorithm was written that provides detailed spectral prediction of component jet noise at user-specified conditions. The model generates quick estimates of the jet mixing noise and the broadband shock-associated noise (BBSN) in single-stream, axis-symmetric jets within a wide range of nozzle operating conditions. Shock noise is emitted when supersonic jets exit a nozzle at imperfectly expanded conditions. A successful scaling of the BBSN allows for this noise component to be predicted in both convergent and convergent-divergent nozzles. Configurations considered in this study consisted of convergent and convergent- divergent nozzles. Velocity exponents for the jet mixing noise were evaluated as a function of observer angle and jet temperature. Similar intensity laws were developed for the broadband shock-associated noise in supersonic jets. A computer program called sJet was developed that provides a quick estimate of component noise in single-stream jets at a wide range of operating conditions. A number of features have been incorporated into the data bank and subsequent scaling in order to improve jet noise predictions. Measurements have been converted to a lossless format. Set points have been carefully selected to minimize the instability-related noise at small aft angles. Regression parameters have been scrutinized for error bounds at each angle. Screech-related amplification noise has been kept to a minimum to ensure that the velocity exponents for the jet mixing noise remain free of amplifications. A shock-noise-intensity scaling has been developed independent of the nozzle design point. The computer program provides detailed narrow-band spectral predictions for component noise (mixing noise and shock associated noise), as well as the total noise. Although the methodology is confined to single

  20. Airframe noise: A design and operating problem

    NASA Technical Reports Server (NTRS)

    Hardin, J. C.

    1976-01-01

    A critical assessment of the state of the art in airframe noise is presented. Full-scale data on the intensity, spectra, and directivity of this noise source are evaluated in light of the comprehensive theory developed by Ffowcs Williams and Hawkings. Vibration of panels on the aircraft is identified as a possible additional source of airframe noise. The present understanding and methods for prediction of other component sources - airfoils, struts, and cavities - are discussed. Operating problems associated with airframe noise as well as potential design methods for airframe noise reduction are identified.

  1. 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.

  2. Indirect combustion noise of auxiliary power units

    NASA Astrophysics Data System (ADS)

    Tam, Christopher K. W.; Parrish, Sarah A.; Xu, Jun; Schuster, Bill

    2013-08-01

    Recent advances in noise suppression technology have significantly reduced jet and fan noise from commercial jet engines. This leads many investigators in the aeroacoustics community to suggest that core noise could well be the next aircraft noise barrier. Core noise consists of turbine noise and combustion noise. There is direct combustion noise generated by the combustion processes, and there is indirect combustion noise generated by the passage of combustion hot spots, or entropy waves, through constrictions in an engine. The present work focuses on indirect combustion noise. Indirect combustion noise has now been found in laboratory experiments. The primary objective of this work is to investigate whether indirect combustion noise is also generated in jet and other engines. In a jet engine, there are numerous noise sources. This makes the identification of indirect combustion noise a formidable task. Here, our effort concentrates exclusively on auxiliary power units (APUs). This choice is motivated by the fact that APUs are relatively simple engines with only a few noise sources. It is, therefore, expected that the chance of success is higher. Accordingly, a theoretical model study of the generation of indirect combustion noise in an Auxiliary Power Unit (APU) is carried out. The cross-sectional areas of an APU from the combustor to the turbine exit are scaled off to form an equivalent nozzle. A principal function of a turbine in an APU is to extract mechanical energy from the flow stream through the exertion of a resistive force. Therefore, the turbine is modeled by adding a negative body force to the momentum equation. This model is used to predict the ranges of frequencies over which there is a high probability for indirect combustion noise generation. Experimental spectra of internal pressure fluctuations and far-field noise of an RE220 APU are examined to identify anomalous peaks. These peaks are possible indirection combustion noise. In the case of the

  3. Predicting Anthropogenic Noise Contributions to US Waters.

    PubMed

    Gedamke, Jason; Ferguson, Megan; Harrison, Jolie; Hatch, Leila; Henderson, Laurel; Porter, Michael B; Southall, Brandon L; Van Parijs, Sofie

    2016-01-01

    To increase understanding of the potential effects of chronic underwater noise in US waters, the National Oceanic and Atmospheric Administration (NOAA) organized two working groups in 2011, collectively called "CetSound," to develop tools to map the density and distribution of cetaceans (CetMap) and predict the contribution of human activities to underwater noise (SoundMap). The SoundMap effort utilized data on density, distribution, acoustic signatures of dominant noise sources, and environmental descriptors to map estimated temporal, spatial, and spectral contributions to background noise. These predicted soundscapes are an initial step toward assessing chronic anthropogenic noise impacts on the ocean's varied acoustic habitats and the animals utilizing them.

  4. Cardiorespiratory Responses to Acoustic Noise in Belugas.

    PubMed

    Lyamin, Oleg I; Korneva, Svetlana M; Rozhnov, Viatcheslav V; Mukhametov, Lev M

    2016-01-01

    To date, most research on the adverse effects of anthropogenic noise on marine mammals has focused on auditory and behavioral responses. Other responses have received little attention and are often ignored. In this study, the effect of acoustic noise on heart rate was examined in captive belugas. The data suggest that (1) heart rate can be used as a measure of physiological response (including stress) to noise in belugas and other cetaceans, (2) cardiac response is influenced by parameters of noise and adaptation to repeated exposure, and (3) cetacean calves are more vulnerable to the adverse effect of noise than adults.

  5. Noise exposure from leisure activities: a review.

    PubMed

    Clark, W W

    1991-07-01

    Over the past two decades there has been increasing concern about the role of nonoccupational, or leisure noise on hearing. This paper reviews published studies that detail the noise levels and potential effects of some noisy leisure activities. Considered are the most common sources of leisure noise: exposure to live or amplified rock, classical, or jazz music; exposures from personal listening devices ("walkman" type); noise around the home, and hunting and target shooting. Although all activities listed above have the potential for dangerous levels of noise exposure, the most serious threat to hearing comes from recreational hunting or target shooting.

  6. Wideband model of HF atmospheric radio noise

    NASA Astrophysics Data System (ADS)

    Lemmon, John J.

    2001-01-01

    A model of the waveform generated by high-frequency atmospheric radio noise is presented. Cumulative probability distributions of the noise envelope are derived and shown to be in good agreement with a large database collected from a wide range of noise environments. The model includes correlations in the waveforms that simulate the burst structure of measured atmospheric noise. The bandwidth dependence of the voltage deviation parameter, which parameterizes the impulsiveness of the noise, shows behavior that is qualitatively similar to a limited amount of measured data.

  7. Flyover-noise measurement and prediction

    NASA Technical Reports Server (NTRS)

    Peart, Noel A.

    1991-01-01

    Details are presented for the measurement and prediction of aircraft flyover noise to be used for certification, research and development, community noise surveys, airport monitors, and pass fail criteria. Test details presented are applicable to all types of aircraft, both large and small, and the use of Federal Aviation Regulations (FAR) Part 36 (ref. 1) is emphasized. Accuracy of noise measurements is important. Thus, a pass-fail criterion should be used for all noise measurements. Finally, factors which influence the sound propagation and noise prediction procedures, such as atmospheric and ground effects, are also presented.

  8. KEPLER MISSION STELLAR AND INSTRUMENT NOISE PROPERTIES

    SciTech Connect

    Gilliland, Ronald L.; Chaplin, William J.; Elsworth, Yvonne P.; Miglio, Andrea; Dunham, Edward W.; Argabright, Vic S.; Borucki, William J.; Bryson, Stephen T.; Koch, David G.; Walkowicz, Lucianne M.; Basri, Gibor; Buzasi, Derek L.; Caldwell, Douglas A.; Jenkins, Jon M.; Van Cleve, Jeffrey; Welsh, William F.

    2011-11-01

    Kepler mission results are rapidly contributing to fundamentally new discoveries in both the exoplanet and asteroseismology fields. The data returned from Kepler are unique in terms of the number of stars observed, precision of photometry for time series observations, and the temporal extent of high duty cycle observations. As the first mission to provide extensive time series measurements on thousands of stars over months to years at a level hitherto possible only for the Sun, the results from Kepler will vastly increase our knowledge of stellar variability for quiet solar-type stars. Here, we report on the stellar noise inferred on the timescale of a few hours of most interest for detection of exoplanets via transits. By design the data from moderately bright Kepler stars are expected to have roughly comparable levels of noise intrinsic to the stars and arising from a combination of fundamental limitations such as Poisson statistics and any instrument noise. The noise levels attained by Kepler on-orbit exceed by some 50% the target levels for solar-type, quiet stars. We provide a decomposition of observed noise for an ensemble of 12th magnitude stars arising from fundamental terms (Poisson and readout noise), added noise due to the instrument and that intrinsic to the stars. The largest factor in the modestly higher than anticipated noise follows from intrinsic stellar noise. We show that using stellar parameters from galactic stellar synthesis models, and projections to stellar rotation, activity, and hence noise levels reproduce the primary intrinsic stellar noise features.

  9. Ultra-High Bypass Ratio Jet Noise

    NASA Technical Reports Server (NTRS)

    Low, John K. C.

    1994-01-01

    The jet noise from a 1/15 scale model of a Pratt and Whitney Advanced Ducted Propulsor (ADP) was measured in the United Technology Research Center anechoic research tunnel (ART) under a range of operating conditions. Conditions were chosen to match engine operating conditions. Data were obtained at static conditions and at wind tunnel Mach numbers of 0.2, 0.27, and 0.35 to simulate inflight effects on jet noise. Due to a temperature dependence of the secondary nozzle area, the model nozzle secondary to primary area ratio varied from 7.12 at 100 percent thrust to 7.39 at 30 percent thrust. The bypass ratio varied from 10.2 to 11.8 respectively. Comparison of the data with predictions using the current Society of Automotive Engineers (SAE) Jet Noise Prediction Method showed that the current prediction method overpredicted the ADP jet noise by 6 decibels. The data suggest that a simple method of subtracting 6 decibels from the SAE Coaxial Jet Noise Prediction for the merged and secondary flow source components would result in good agreement between predicted and measured levels. The simulated jet noise flight effects with wind tunnel Mach numbers up to 0.35 produced jet noise inflight noise reductions up to 12 decibels. The reductions in jet noise levels were across the entire jet noise spectra, suggesting that the inflight effects affected all source noise components.

  10. Chicago Transit Authority Train Noise Exposure.

    PubMed

    Phan, Linh T; Jones, Rachael M

    2017-02-07

    To characterize noise exposure of riders on Chicago Transit Authority (CTA) trains, we measured noise levels twice on each segment of seven of the eight CTA train lines, which are named after colors, yielding 48 time-series measurements. We found the Blue Line has the highest noise levels compared to other train lines, with mean 76.9 dBA; and that the maximum noise level, 88.9 dBA occurred in the tunnel between the Chicago and Grand stations. Train segments involving travel through a tunnel had significantly higher noise levels than segments with travel on elevated and ground level tracks. While 8-hour doses inside the passenger cars were not estimated to exceed occupational exposure limits, train operators ride in a separate cab with operational windows and may therefore have higher noise exposures than riders. Despite the low risk of hearing loss for riders on CTA trains, in part because transit noise accounts for a small part of total daily noise exposure, 1-minute average noise levels exceeded 85 dBA at times. This confirms anecdotal observations of discomfort due to noise levels, and indicates a need for noise management, particularly in tunnels.

  11. Ambient noise in large rivers (L).

    PubMed

    Vračar, Miodrag S; Mijić, Miomir

    2011-10-01

    This paper presents the results of hydroacoustic noise research in three large European rivers: the Danube, the Sava, and the Tisa. Noise in these rivers was observed during a period of ten years, which includes all annual variation in hydrological and meteorological conditions (flow rate, speed of flow, wind speed, etc.). Noise spectra are characterized by wide maximums at frequencies between 20 and 30 Hz, and relatively constant slope toward higher frequencies. Spectral level of noise changes in time in relatively wide limits. At low frequencies, below 100 Hz, the dynamics of noise level is correlated with the dynamics of water flow and speed. At higher frequencies, noise spectra are mostly influenced by human activities on river and on riverbanks. The influence of wind on noise in rivers is complex due to the annual variation of river surface. The influence of wind is less pronounced than in oceans, seas, and lakes.

  12. Anthropogenic noise increases fish mortality by predation

    PubMed Central

    Simpson, Stephen D.; Radford, Andrew N.; Nedelec, Sophie L.; Ferrari, Maud C. O.; Chivers, Douglas P.; McCormick, Mark I.; Meekan, Mark G.

    2016-01-01

    Noise-generating human activities affect hearing, communication and movement in terrestrial and aquatic animals, but direct evidence for impacts on survival is rare. We examined effects of motorboat noise on post-settlement survival and physiology of a prey fish species and its performance when exposed to predators. Both playback of motorboat noise and direct disturbance by motorboats elevated metabolic rate in Ambon damselfish (Pomacentrus amboinensis), which when stressed by motorboat noise responded less often and less rapidly to simulated predatory strikes. Prey were captured more readily by their natural predator (dusky dottyback, Pseudochromis fuscus) during exposure to motorboat noise compared with ambient conditions, and more than twice as many prey were consumed by the predator in field experiments when motorboats were passing. Our study suggests that a common source of noise in the marine environment has the potential to impact fish demography, highlighting the need to include anthropogenic noise in management plans. PMID:26847493

  13. Quantum limited heterodyne detection of spin noise

    NASA Astrophysics Data System (ADS)

    Cronenberger, S.; Scalbert, D.

    2016-09-01

    Spin noise spectroscopy is a powerful technique for studying spin relaxation in semiconductors. In this article, we propose an extension of this technique based on optical heterodyne detection of spin noise, which provides several key advantages compared to conventional spin noise spectroscopy: detection of high frequency spin noise not limited by detector bandwidth or sampling rates of digitizers, quantum limited sensitivity even in case of very weak probe power, and possible amplification of the spin noise signal. Heterodyne detection of spin noise is demonstrated on insulating n-doped GaAs. From measurements of spin noise spectra up to 0.4 Tesla, we determined the distribution of g-factors, Δg/g = 0.49%.

  14. Helicopter Flight Procedures for Community Noise Reduction

    NASA Technical Reports Server (NTRS)

    Greenwood, Eric

    2017-01-01

    A computationally efficient, semiempirical noise model suitable for maneuvering flight noise prediction is used to evaluate the community noise impact of practical variations on several helicopter flight procedures typical of normal operations. Turns, "quick-stops," approaches, climbs, and combinations of these maneuvers are assessed. Relatively small variations in flight procedures are shown to cause significant changes to Sound Exposure Levels over a wide area. Guidelines are developed for helicopter pilots intended to provide effective strategies for reducing the negative effects of helicopter noise on the community. Finally, direct optimization of flight trajectories is conducted to identify low noise optimal flight procedures and quantify the magnitude of community noise reductions that can be obtained through tailored helicopter flight procedures. Physically realizable optimal turns and approaches are identified that achieve global noise reductions of as much as 10 dBA Sound Exposure Level.

  15. On noise indices for domestic air conditioners

    NASA Astrophysics Data System (ADS)

    Tang, S. K.; Wong, M. Y.

    2004-07-01

    A survey was carried out in the present study to determine the noise indices which are capable of describing the nuisance caused by exposure to air-conditioner noise inside residential apartments. This survey consisted of a questionnaire, which asked the respondents to rate their feelings of annoyance and loudness on the air-conditioner noise and to give their preference of a change in the noise levels. Physical noise measurements were also carried out. A total of 57 noise spectra and 399 respondents were involved in the survey. Results show that the Zwicker's loudness level and the percentile level of 90% exceedence are the two major indices for air-conditioner noise assessment. Tonality appears not to be a good indicator for such a purpose.

  16. Non-Markovian stochastic processes: colored noise.

    PubMed

    Łuczka, J

    2005-06-01

    We survey classical non-Markovian processes driven by thermal equilibrium or nonequilibrium (nonthermal) colored noise. Examples of colored noise are presented. For processes driven by thermal equilibrium noise, the fluctuation-dissipation relation holds. In consequence, the system has to be described by a generalized (integro-differential) Langevin equation with a restriction on the damping integral kernel: Its form depends on the correlation function of noise. For processes driven by nonequilibrium noise, there is no such a restriction: They are considered to be described by stochastic differential (Ito- or Langevin-type) equations with an independent noise term. For the latter, we review methods of analysis of one-dimensional systems driven by Ornstein-Uhlenbeck noise.

  17. Anthropogenic noise increases fish mortality by predation.

    PubMed

    Simpson, Stephen D; Radford, Andrew N; Nedelec, Sophie L; Ferrari, Maud C O; Chivers, Douglas P; McCormick, Mark I; Meekan, Mark G

    2016-02-05

    Noise-generating human activities affect hearing, communication and movement in terrestrial and aquatic animals, but direct evidence for impacts on survival is rare. We examined effects of motorboat noise on post-settlement survival and physiology of a prey fish species and its performance when exposed to predators. Both playback of motorboat noise and direct disturbance by motorboats elevated metabolic rate in Ambon damselfish (Pomacentrus amboinensis), which when stressed by motorboat noise responded less often and less rapidly to simulated predatory strikes. Prey were captured more readily by their natural predator (dusky dottyback, Pseudochromis fuscus) during exposure to motorboat noise compared with ambient conditions, and more than twice as many prey were consumed by the predator in field experiments when motorboats were passing. Our study suggests that a common source of noise in the marine environment has the potential to impact fish demography, highlighting the need to include anthropogenic noise in management plans.

  18. Gypsies' response to road traffic noise

    NASA Astrophysics Data System (ADS)

    Griffiths, I. D.; Raw, G. J.; Hill, C. A.; Storrar, J. M.

    1985-07-01

    A survey was carried out at 11 gypsy sites, in order to determine the extent to which gypsies are bothered by road traffic noise. Interviews were obtained with 149 gypsies, providing data on noise bother and satisfaction with other aspects of the sites. Noise measurements were carried out at each site, providing values of 18 hr L eq dB(A). The hypothesis, that gypsies would be less bothered by road traffic noise than the settled population, was based on consideration of the importance of the road in gypsies' lives, and on a small pilot study. This hypothesis was supported. In addition, there was no indication that noise bother was correlated with noise level. From a closer inspection of this result, a further hypothesis has been developed, that gypsies living in caravans may tend to migrate to sites at which the noise level is acceptable in the context of other site features.

  19. Natural radio noise - A mini-review

    NASA Technical Reports Server (NTRS)

    Flock, W. L.; Smith, E. K.

    1984-01-01

    Natural radio noise in telecommunication systems can be accounted for by the contribution which it makes to antenna noise temperature. Attenuation due to water vapor and oxygen, clouds, and precipitation is accompanied by thermal noise which further degrades the applicable signal-to-noise ratio. Extraterrestrial noise may be of thermal or nonthermal origin and may cover a continuum of frequencies or occur at discrete frequencies. The spectral index n (the exponent giving the variation of noise power density with wavelength) is -2 for a black body and between 0 and -2 for thermal emission in general. The mechanism responsible for much of the extensive nonthermal extraterrestrial noise is synchrotron radiation, characterized by a positive spectral index.

  20. Image Compression in Signal-Dependent Noise

    NASA Astrophysics Data System (ADS)

    Shahnaz, Rubeena; Walkup, John F.; Krile, Thomas F.

    1999-09-01

    The performance of an image compression scheme is affected by the presence of noise, and the achievable compression may be reduced significantly. We investigated the effects of specific signal-dependent-noise (SDN) sources, such as film-grain and speckle noise, on image compression, using JPEG (Joint Photographic Experts Group) standard image compression. For the improvement of compression ratios noisy images are preprocessed for noise suppression before compression is applied. Two approaches are employed for noise suppression. In one approach an estimator designed specifically for the SDN model is used. In an alternate approach, the noise is first transformed into signal-independent noise (SIN) and then an estimator designed for SIN is employed. The performances of these two schemes are compared. The compression results achieved for noiseless, noisy, and restored images are also presented.