Science.gov

Sample records for active noise cancellation

  1. Active noise canceling system for mechanically cooled germanium radiation detectors

    DOEpatents

    Nelson, Karl Einar; Burks, Morgan T

    2014-04-22

    A microphonics noise cancellation system and method for improving the energy resolution for mechanically cooled high-purity Germanium (HPGe) detector systems. A classical adaptive noise canceling digital processing system using an adaptive predictor is used in an MCA to attenuate the microphonics noise source making the system more deployable.

  2. Active Control of Fan Noise: Feasibility Study. Volume 3; Active Fan Noise Cancellation in the NASA Lewis Active Noise Control Fan Facility

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G.; Hu, Ziqiang; Sutliff, Daniel L.

    1996-01-01

    This report describes the Active Noise Cancellation (ANC) System designed by General Electric and tested in the NASA Lewis Research Center's (LERC) 48 inch Active Noise Control Fan (ANCF). The goal of this study is to assess the feasibility of using wall mounted secondary acoustic sources and sensors within the duct of a high bypass turbofan aircraft engine for global active noise cancellation of fan tones. The GE ANC system is based on a modal control approach. A known acoustic mode propagating in the fan duct is canceled using an array of flush-mounted compact sound sources. The canceling modal signal is generated by a modal controller. Inputs to the controller are signals from a shaft encoder and from a microphone array which senses the residual acoustic mode in the duct. The key results are that the (6,0) was completely eliminated at the 920 Hz design frequency and substantially reduced elsewhere. The total tone power was reduced 6.8 dB (out of a possible 9.8 dB). Farfield reductions of 15 dB (SPL) were obtained. The (4,0) and (4,1) modes were reduced simultaneously yielding a 15 dB PWL decrease. The results indicate that global attenuation of PWL at the target frequency was obtained in the aft quadrant using an ANC actuator and sensor system totally contained within the duct. The quality of the results depended on precise mode generation. High spillover into spurious modes generated by the ANC actuator array caused less than optimum levels of PWL reduction. The variation in spillover is believed to be due to calibration procedure, but must be confirmed in subsequent tests.

  3. Industrial wideband noise reduction for hearing aids using a headset with adaptive-feedback active noise cancellation.

    PubMed

    Lin, J H; Li, P C; Tang, S T; Liu, P T; Young, S T

    2005-11-01

    High-intensity noises are a health hazard for industrial workers, and hearing protection is necessary to prevent hearing loss. Passive methods, such as ear muffs, are ineffective against low-frequency noise. Moreover, many hearing-impaired workers must wear hearing aids to enable communication at their workplace, and such aids can amplify ambient noise. To overcome this problem, the present study developed a headset equipped with a digital signal processing system to implement adaptive-feedback active noise cancellation (AFANC) to reduce low-frequency noise. The proposed AFANC headset was effective against wideband industrial noise, with a maximum noise spectrum power reduction of 30 dB. Furthermore, when used with a hearing aid, it improved the speech signal-to-noise ratio by up to 14 dB. These results suggest that a headset with AFANC would be useful for hearing protection in workplaces with high levels of low-frequency industrial noise, especially for hearing-impaired workers. PMID:16594300

  4. Active vibration control on a quarter-car for cancellation of road noise disturbance

    NASA Astrophysics Data System (ADS)

    Belgacem, Walid; Berry, Alain; Masson, Patrice

    2012-07-01

    In this paper, a methodology is presented for the cancellation of road noise, from the analysis of vibration transmission paths for an automotive suspension to the design of an active control system using inertial actuators on a suspension to reduce the vibrations transmitted to the chassis. First, experiments were conducted on a Chevrolet Epica LS automobile on a concrete test track to measure accelerations induced on the suspension by the road. These measurements were combined with experimental Frequency Response Functions (FRFs) measured on a quarter-car test bench to reconstruct an equivalent three dimensional force applied on the wheel hub. Second, FRFs measured on the test bench between the three-dimensional driving force and forces at each suspension/chassis linkage were used to characterize the different transmission paths of vibration energy to the chassis. Third, an experimental model of the suspension was constructed to simulate the configuration of the active control system, using the primary (disturbance) FRFs and secondary (control) FRFs also measured on the test bench. This model was used to optimize the configuration of the control actuators and to evaluate the required forces. Finally, a prototype of an active suspension was implemented and measurements were performed in order to assess the performance of the control approach. A 4.6 dB attenuation on transmitted forces was obtained in the 50-250 Hz range.

  5. Carbon Nanotube Thin Films for Active Noise Cancellation, Solar Energy Harvesting, and Energy Storage in Building Windows

    NASA Astrophysics Data System (ADS)

    Hu, Shan

    This research explores the application of carbon nanotube (CNT) films for active noise cancellation, solar energy harvesting and energy storage in building windows. The CNT-based components developed herein can be integrated into a solar-powered active noise control system for a building window. First, the use of a transparent acoustic transducer as both an invisible speaker for auxiliary audio playback and for active noise cancellation is accomplished in this work. Several challenges related to active noise cancellation in the window are addressed. These include secondary path estimation and directional cancellation of noise so as to preserve auxiliary audio and internal sounds while preventing transmission of external noise into the building. Solar energy can be harvested at a low rate of power over long durations while acoustic sound cancellation requires short durations of high power. A supercapacitor based energy storage system is therefore considered for the window. Using CNTs as electrode materials, two generations of flexible, thin, and fully solid-state supercapacitors are developed that can be integrated into the window frame. Both generations consist of carbon nanotube films coated on supporting substrates as electrodes and a solid-state polymer gel layer for the electrolyte. The first generation is a single-cell parallel-plate supercapacitor with a working voltage of 3 Volts. Its energy density is competitive with commercially available supercapacitors (which use liquid electrolyte). For many applications that will require higher working voltage, the second-generation multi-cell supercapacitor is developed. A six-cell device with a working voltage as high as 12 Volts is demonstrated here. Unlike the first generation's 3D structure, the second generation has a novel planar (2D) architecture, which makes it easy to integrate multiple cells into a thin and flexible supercapacitor. The multi-cell planar supercapacitor has energy density exceeding that of

  6. Noise canceling in-situ detection

    SciTech Connect

    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.

  7. 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

  8. Active Control of Environmental Noise, Vi: Performance of a Fundamental Free-Field Sound Cancelling System

    NASA Astrophysics Data System (ADS)

    WRIGHT, S. E.; ATMOKO, H.

    2001-08-01

    Before the adaptive cancellation performance of multichannel free-field acoustic systems could be evaluated in detail, it was considered prudent to establish first the performance of a single channel free-field cancelling system. The adaptive theory for this basic system, including the stability process, is described. Measured adaptive performance is given confirming the theory.The concept of stability bands and their prediction is considered. The bands are a consequence of phase differences between the primary source and secondary cancelling field, generated by the transfer functions of the control system. At the edge of these stability bands satellite pole frequencies “beat” with the cancelling frequency, generated by the zeros, to produce side bands. The relation between the stability bandwidth and the adaptive speed, in terms of reference signal strength and adaptive step size, are investigated.The sound generation and cancellation performance of this basic canceller are then considered. The acoustic sound field directivity characteristics are similar to that of a dipole, tripole or quadrupole type source, depending on the primary-secondary source separation distance. The acoustic shadow characteristics are established in detail and compared with measurement. Good agreement is obtained.

  9. Sub-band adaptive noise cancelling

    NASA Astrophysics Data System (ADS)

    Ryan, James G.; Goubran, Rafik A.

    The technique of using sub-band adaptive filters for acoustic noise suppression is examined. Simulation results are presented for experimental systems trained with white noise and colored noise for both decimated and non-decimated sub-band signals. To illustrate the usefulness of the sub-band approach for a real application, the full band and sub-band noise cancellers were applied to car data. Estimates of the input and output power spectra for the different cases are presented. It is shown that the full-band noise canceller is unable to attenuate the noise in the higher frequencies due to the low input signal power in this region. The sub-band decomposition of the input signal can significantly increase the rate as compared to a full-band implementation under certain conditions. This increase in convergence speed is manifested as an increased noise attenuation in those regions of the input spectrum with relatively low amounts of power. In addition, the sub-band processing is seen to eliminate the noise enhancement phenomenon found in acoustic noise cancellers for mobile telephony.

  10. Active Control of Fan Noise-Feasibility Study. Volume 2: Canceling Noise Source-Design of an Acoustic Plate Radiator Using Piezoceramic Actuators

    NASA Technical Reports Server (NTRS)

    Pla, F. G.; Rajiyah, H.

    1995-01-01

    The feasibility of using acoustic plate radiators powered by piezoceramic thin sheets as canceling sources for active control of aircraft engine fan noise is demonstrated. Analytical and numerical models of actuated beams and plates are developed and validated. An optimization study is performed to identify the optimum combination of design parameters that maximizes the plate volume velocity for a given resonance frequency. Fifteen plates with various plate and actuator sizes, thicknesses, and bonding layers were fabricated and tested using results from the optimization study. A maximum equivalent piston displacement of 0.39 mm was achieved with the optimized plate samples tested with only one actuator powered, corresponding to a plate deflection at the center of over 1 millimeter. This is very close to the deflection required for a full size engine application and represents a 160-fold improvement over previous work. Experimental results further show that performance is limited by the critical stress of the piezoceramic actuator and bonding layer rather than by the maximum moment available from the actuator. Design enhancements are described in detail that will lead to a flight-worthy acoustic plate radiator by minimizing actuator tensile stresses and reducing nonlinear effects. Finally, several adaptive tuning methods designed to increase the bandwidth of acoustic plate radiators are analyzed including passive, active, and semi-active approaches. The back chamber pressurization and volume variation methods are investigated experimentally and shown to be simple and effective ways to obtain substantial control over the resonance frequency of a plate radiator. This study shows that piezoceramic-based plate radiators can be a viable acoustic source for active control of aircraft engine fan noise.

  11. Driver Module for Noise Cancellation System

    NASA Astrophysics Data System (ADS)

    Shirvani, Mir S.

    2002-12-01

    The Driver module is an integral part of the noise cancellation system, which was my primary objective to research, design, and prototype during the tenure in NASA Langley research center. The function of the driver module is to actuate a panel that is constructed with a smart material and invented in NASA-LaRC. The bandwidth and amplitude of the actuation of the panel correlates the undesirable structural bandwidth and amplitude of the applied object. The undesirable structural bandwidth is relatively narrow and the undesirable amplitude is relatively large. A highly stable, low distortion, linear monolithic integrated circuit was used as a variable frequency and amplitude function generator. In order to elevate the amplitude of the output waveform of the generator to a sufficient magnitude a pair of high voltage monolithic MOSFET operational amplifiers were implemented. The amplifiers connected in a bipolar bridge configuration for a higher efficiency. In order to reduce the required external Supply voltages and make the driver capable to be operated by a battery a pair of ultra miniature high-output voltage dc to dc converters are also used. The driver module tested with the noise cancellation panel, the required data was acquired, and the result was promising. After examining all the options the driver module was designed and prototyped.

  12. Experimental testing of the noise-canceling processor.

    PubMed

    Collins, Michael D; Baer, Ralph N; Simpson, Harry J

    2011-09-01

    Signal-processing techniques for localizing an acoustic source buried in noise are tested in a tank experiment. Noise is generated using a discrete source, a bubble generator, and a sprinkler. The experiment has essential elements of a realistic scenario in matched-field processing, including complex source and noise time series in a waveguide with water, sediment, and multipath propagation. The noise-canceling processor is found to outperform the Bartlett processor and provide the correct source range for signal-to-noise ratios below -10 dB. The multivalued Bartlett processor is found to outperform the Bartlett processor but not the noise-canceling processor.

  13. Micropower non-contact EEG electrode with active common-mode noise suppression and input capacitance cancellation.

    PubMed

    Chi, Yu M; Cauwenberghs, Gert

    2009-01-01

    A non-contact EEG electrode with input capacitance neutralization and common-mode noise suppression circuits is presented. The coin sized sensor capacitively couples to the scalp without direct contact to the skin. To minimize the effect of signal attenuation and channel gain mismatch, the input capacitance of each sensor is actively neutralized using positive feedback and bootstrapping. Common-mode suppression is achieved through a single conductive sheet to establish a common mode reference. Each sensor electrode provides a differential gain of 60 dB. Signals are transmitted in a digital serial daisy-chain directly from a local 16-bit ADC, minimizing the number of wires required to establish a high density EEG sensor network. The micropower electrode consumes only 600 microW from a single 3.3 V supply.

  14. Laboratory Investigation of Noise-Canceling Headphones Utilizing "Mr. Blockhead"

    ERIC Educational Resources Information Center

    Koser, John

    2013-01-01

    While I was co-teaching an introductory course in musical acoustics a few years ago, our class investigated several pieces of equipment designed for audio purposes. One piece of such equipment was a pair of noise-canceling headphones. Our students were curious as to how these devices were in eliminating background noise and whether they indeed…

  15. Laboratory Investigation of Noise-Canceling Headphones Utilizing ``Mr. Blockhead''

    NASA Astrophysics Data System (ADS)

    Koser, John

    2013-09-01

    While I was co-teaching an introductory course in musical acoustics a few years ago, our class investigated several pieces of equipment designed for audio purposes. One piece of such equipment was a pair of noise-canceling headphones. Our students were curious as to how these devices were in eliminating background noise and whether they indeed block low-frequency sounds as advertised.

  16. A differential magnetoelectric heterostructure: Internal noise reduction and external noise cancellation

    NASA Astrophysics Data System (ADS)

    Wang, Yaojin; Li, Jiefang; Viehland, D.

    2015-12-01

    A differential heterostructure design which has a capability to reduce the internal noise and reject the external vibration noise for Metglas magnetostrictive foils/Pb(Zr, Ti)O3 piezofiber based-magnetoelectric (ME) laminated composite has been studied. The internal noise reduction is equivalent to that offered by sensor array stacks, and the external noise cancellation is based on a differential method (i.e., ME signal is in-phase but vibration noise is anti-phase). The ability of the structure to reduce the internal noise, and cancel the external vibration noise by a 10-fold attenuation factor, allows for practical applications of these sensors in real-world environments where contamination of magnetic signals by external vibrational noise increases the equivalent magnetic noise.

  17. Newtonian noise cancellation in tensor gravitational wave detector

    NASA Astrophysics Data System (ADS)

    Paik, Ho Jung; Harms, Jan

    2016-05-01

    Terrestrial gravity noise produced by ambient seismic and infrasound fields poses one of the main sensitivity limitations in low-frequency ground-based gravitational-wave (GW) detectors. This noise needs to be suppressed by 3-5 orders of magnitude in the frequency band 10 mHz to 1 Hz, which is extremely challenging. We present a new approach that greatly facilitates cancellation of gravity noise in full-tensor GW detectors. It makes explicit use of the direction of propagation of a GW, and can therefore either be implemented in directional searches for GWs or in observations of known sources. We show that suppression of the Newtonian-noise foreground is greatly facilitated using the extra strain channels in full-tensor GW detectors. Only a modest number of auxiliary, high-sensitivity environmental sensors is required to achieve noise suppression by a few orders of magnitude.

  18. Noise-Canceling Helmet Audio System

    NASA Technical Reports Server (NTRS)

    Seibert, Marc A.; Culotta, Anthony J.

    2007-01-01

    A prototype helmet audio system has been developed to improve voice communication for the wearer in a noisy environment. The system was originally intended to be used in a space suit, wherein noise generated by airflow of the spacesuit life-support system can make it difficult for remote listeners to understand the astronaut s speech and can interfere with the astronaut s attempt to issue vocal commands to a voice-controlled robot. The system could be adapted to terrestrial use in helmets of protective suits that are typically worn in noisy settings: examples include biohazard, fire, rescue, and diving suits. The system (see figure) includes an array of microphones and small loudspeakers mounted at fixed positions in a helmet, amplifiers and signal-routing circuitry, and a commercial digital signal processor (DSP). Notwithstanding the fixed positions of the microphones and loudspeakers, the system can accommodate itself to any normal motion of the wearer s head within the helmet. The system operates in conjunction with a radio transceiver. An audio signal arriving via the transceiver intended to be heard by the wearer is adjusted in volume and otherwise conditioned and sent to the loudspeakers. The wearer s speech is collected by the microphones, the outputs of which are logically combined (phased) so as to form a microphone- array directional sensitivity pattern that discriminates in favor of sounds coming from vicinity of the wearer s mouth and against sounds coming from elsewhere. In the DSP, digitized samples of the microphone outputs are processed to filter out airflow noise and to eliminate feedback from the loudspeakers to the microphones. The resulting conditioned version of the wearer s speech signal is sent to the transceiver.

  19. Background noise cancellation for improved acoustic detection of manatee vocalizations

    NASA Astrophysics Data System (ADS)

    Yan, Zheng; Niezrecki, Christopher; Beusse, Diedrich O.

    2005-04-01

    The West Indian manatee (Trichechus manatus latirostris) has become endangered partly because of an increase in the number of collisions with boats. A device to alert boaters of the presence of manatees, so that a collision can be avoided, is desired. Practical implementation of the technology is dependent on the hydrophone spacing and range of detection. These parameters are primarily dependent on the manatee vocalization strength, the decay of the signal strength with distance, and the background noise levels. An efficient method to extend the detection range by using background noise cancellation is proposed in this paper. An adaptive line enhancer (ALE) that can detect and track narrowband signals buried in broadband noise is implemented to cancel the background noise. The results indicate that the ALE algorithm can efficiently extract the manatee calls from the background noise. The improved signal-to-noise ratio of the signal can be used to extend the range of detection of manatee vocalizations and reduce the false alarm and missing detection rate in their natural habitat.

  20. Background noise cancellation for improved acoustic detection of manatee vocalizations

    NASA Astrophysics Data System (ADS)

    Yan, Zheng; Niezrecki, Christopher; Beusse, Diedrich O.

    2005-06-01

    The West Indian manatee (Trichechus manatus latirostris) has become endangered partly because of an increase in the number of collisions with boats. A device to alert boaters of the presence of manatees, so that a collision can be avoided, is desired. A practical implementation of the technology is dependent on the hydrophone spacing and range of detection. These parameters are primarily dependent on the manatee vocalization strength, the decay of the signal's strength with distance, and the background noise levels. An efficient method to extend the detection range by using background noise cancellation is proposed in this paper. An adaptive line enhancer (ALE) that can detect and track narrow band signals buried in broadband noise is implemented to cancel the background noise. The results indicate that the ALE algorithm can efficiently extract the manatee calls from the background noise. The improved signal-to-noise ratio of the signal can be used to extend the range of detection of manatee vocalizations and reduce the false alarm and missing detection rate in their natural habitat. .

  1. First Experimental Demonstration of Noise Cancellation for LISA Interferometry

    NASA Astrophysics Data System (ADS)

    De Vine, Glenn; Shaddock, D.; Ware, B.; Spero, R.; Klipstein, W.

    2009-01-01

    We report on the first experimental demonstration of post-processed, time-delay interferometry with USO noise cancellation for the Laser Interferometer Space Antenna. The demonstration used simplified optical benches constructed from ultra-low expansion glass and the LISA phasemeter prototype. Each bench was incorporated into an end station, consisting of two NPRO lasers, and three phase measurements (two inter-bench measurements and one local measurement). The interferometer has been designed to provide signals representative of LISA interferometry. The laser frequency noise-free combination, alpha, was formed by combining the six phase measurements from the two end stations, each of which contained a clock which was used as the master reference for that bench's three phase measurements. The phase measurements were interpolated in post-processing to correct for errors in sampling times caused by relative drift of the end stations' clocks. After interpolation, the laser frequency noise in alpha was reduced by almost 4 orders of magnitude (relative to the noise level in the individual phase measurements) down to the performance limit of the interferometer. As expected, the independent clocks' phase fluctuations also caused a large increase in the measured noise. This clock phase noise was removed by phase modulating the clock frequencies onto laser beams exchanged between spacecraft in the manner planned for LISA. The clock noise was suppressed by almost 5 orders of magnitude. Notably, both the laser frequency noise and clock noise were suppressed down to our interferometer displacement noise level of 20 pm/√Hz at 0.1 Hz. Although this noise meets the LISA minimum mission requirement, work is ongoing to reduce the pathlength noise low enough to demonstrate laser frequency noise and clock noise suppression to below the error allocation of approximately 13 pm/√Hz. The current results validate both the expected performance of TDI as well as the performance of the

  2. 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.

  3. Transient plasma estimation: a noise cancelling/identification approach

    SciTech Connect

    Candy, J.V.; Casper, T.; Kane, R.

    1985-03-01

    The application of a noise cancelling technique to extract energy storage information from sensors occurring during fusion reactor experiments on the Tandem Mirror Experiment-Upgrade (TMX-U) at the Lawrence Livermore National Laboratory (LLNL) is examined. We show how this technique can be used to decrease the uncertainty in the corresponding sensor measurements used for diagnostics in both real-time and post-experimental environments. We analyze the performance of algorithm on the sensor data and discuss the various tradeoffs. The algorithm suggested is designed using SIG, an interactive signal processing package developed at LLNL.

  4. Active attenuation of propeller blade passage noise

    NASA Technical Reports Server (NTRS)

    Zalas, J. M.; Tichy, J.

    1984-01-01

    Acoustic measurements are presented to show that active cancellation can be used to achieve significant reduction of blade passage noise in a turboprop cabin. Simultaneous suppression of all blade passage frequencies was attained. The spatial volume over which cancellation occurred, however, is limited. Acoustic intensity maps are presented to show that the acoustic input to the fuselage was sufficiently non-localized so as to require more judicious selection of cancellation speaker location.

  5. Real-time vehicle noise cancellation techniques for gunshot acoustics

    NASA Astrophysics Data System (ADS)

    Ramos, Antonio L. L.; Holm, Sverre; Gudvangen, Sigmund; Otterlei, Ragnvald

    2012-06-01

    Acoustical sniper positioning systems rely on the detection and direction-of-arrival (DOA) estimation of the shockwave and the muzzle blast in order to provide an estimate of a potential snipers location. Field tests have shown that detecting and estimating the DOA of the muzzle blast is a rather difficult task in the presence of background noise sources, e.g., vehicle noise, especially in long range detection and absorbing terrains. In our previous work presented in the 2011 edition of this conference we highlight the importance of improving the SNR of the gunshot signals prior to the detection and recognition stages, aiming at lowering the false alarm and miss-detection rates and, thereby, increasing the reliability of the system. This paper reports on real-time noise cancellation techniques, like Spectral Subtraction and Adaptive Filtering, applied to gunshot signals. Our model assumes the background noise as being short-time stationary and uncorrelated to the impulsive gunshot signals. In practice, relatively long periods without signal occur and can be used to estimate the noise spectrum and its first and second order statistics as required in the spectral subtraction and adaptive filtering techniques, respectively. The results presented in this work are supported with extensive simulations based on real data.

  6. Active{sup 3} noise reduction

    SciTech Connect

    Holzfuss, J.

    1996-06-01

    Noise reduction is a problem being encountered in a variety of applications, such as environmental noise cancellation, signal recovery and separation. Passive noise reduction is done with the help of absorbers. Active noise reduction includes the transmission of phase inverted signals for the cancellation. This paper is about a threefold active approach to noise reduction. It includes the separation of a combined source, which consists of both a noise and a signal part. With the help of interaction with the source by scanning it and recording its response, modeling as a nonlinear dynamical system is achieved. The analysis includes phase space analysis and global radial basis functions as tools for the prediction used in a subsequent cancellation procedure. Examples are given which include noise reduction of speech. {copyright} {ital 1996 American Institute of Physics.}

  7. An On-Chip Noise Canceller with High Voltage Supply Lines for Nanosecond-Range Power Supply Noise

    NASA Astrophysics Data System (ADS)

    Nakamura, Yasumi; Takamiya, Makoto; Sakurai, Takayasu

    An on-chip power supply noise canceller with higher voltage supply and switching transistor is proposed and the effectiveness of the canceller is experimentally verified. The noise canceller is effective for nano-second order noise caused by circuit wakeup or step increase of frequency in frequency hopping. The principle of the noise canceller is to reduce the current flowing through the supply line of VDD by injecting additional current from the higher voltage supply, so that the voltage drop across the VDD supply line is reduced. As additional current flow from higher supply, switching transistor has to be turned off not to increase the power consumption. With turn-off time of 2L/R, this current can be turned off without inducting another droop due to the increase of current flowing through the power supply line. The measurement shows the canceller reduces 68% of the noise with load circuit equivalent to 530k logic gates in 90-nm CMOS with 9% wire overhead, 1.5% area overhead, and 3% power overhead at 50k wake-ups/s. Compared to passive noise reduction, proposed noise canceller reduces power supply noise by 64% without wire overhead and to achieve same noise reduction with passive method, 77 times more C or 45 times less L is required. Too large switching transistor results in saturated noise reduction effect and higher power consumption. A rule-of-thumb is to set the on-resistance to supply 100% of load current when turned-on.

  8. Characteristics of noise-canceling headphones to reduce the hearing hazard for MP3 users.

    PubMed

    Liang, Maojin; Zhao, Fei; French, David; Zheng, Yiqing

    2012-06-01

    Three pairs of headphones [standard iPod ear buds and two noise-canceling headphones (NCHs)] were chosen to investigate frequency characteristics of noise reduction, together with their attenuation effects on preferred listening levels (PLLs) in the presence of various types of background noise. Twenty-six subjects with normal hearing chose their PLLs in quiet, street noise, and subway noise using the three headphones and with the noise-canceling system on/off. Both sets of NCHs reduced noise levels at mid- and high-frequencies. Further noise reductions occurred in low frequencies with the noise canceling system switched on. In street noise, both NCHs had similar noise reduction effects. In subway noise, better noise reduction effects were found in the expensive NCH and with noise-canceling on. A two way repeated measures analysis of variance showed that both listening conditions and headphone styles were significant influencing factors on the PLLs. Subjects tended to increase their PLLs as the background noise level increased. Compared with ear buds, PLLs obtained from NCHs-on in the presence of background noise were reduced up to 4 dB. Therefore, proper selection and use of NCHs appears beneficial in reducing the risk of hearing damage caused by high music listening levels in the presence of background noise.

  9. Recent advances in active noise control

    NASA Astrophysics Data System (ADS)

    Guicking, D.

    Advances in the field of active noise control over the last few years are reviewed. Some commercially available products and their technical applications are described, with particular attention given to broadband duct noise silencers, broadband active headphones, waveform synthesis, and LMS controllers. Recent theoretical and experimental research activities are then reviewed. These activities are concerned with duct noise, structural sound, interior spaces, algorithms, echo cancellation, and miscellaneous applications.

  10. Adaptive noise cancellation based on beehive pattern evolutionary digital filter

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaojun; Shao, Yimin

    2014-01-01

    Evolutionary digital filtering (EDF) exhibits the advantage of avoiding the local optimum problem by using cloning and mating searching rules in an adaptive noise cancellation system. However, convergence performance is restricted by the large population of individuals and the low level of information communication among them. The special beehive structure enables the individuals on neighbour beehive nodes to communicate with each other and thus enhance the information spread and random search ability of the algorithm. By introducing the beehive pattern evolutionary rules into the original EDF, this paper proposes an improved beehive pattern evolutionary digital filter (BP-EDF) to overcome the defects of the original EDF. In the proposed algorithm, a new evolutionary rule which combines competing cloning, complete cloning and assistance mating methods is constructed to enable the individuals distributed on the beehive to communicate with their neighbours. Simulation results are used to demonstrate the improved performance of the proposed algorithm in terms of convergence speed to the global optimum compared with the original methods. Experimental results also verify the effectiveness of the proposed algorithm in extracting feature signals that are contaminated by significant amounts of noise during the fault diagnosis task.

  11. A Background Noise Reduction Technique Using Adaptive Noise Cancellation for Microphone Arrays

    NASA Technical Reports Server (NTRS)

    Spalt, Taylor B.; Fuller, Christopher R.; Brooks, Thomas F.; Humphreys, William M., Jr.; Brooks, Thomas F.

    2011-01-01

    Background noise in wind tunnel environments poses a challenge to acoustic measurements due to possible low or negative Signal to Noise Ratios (SNRs) present in the testing environment. This paper overviews the application of time domain Adaptive Noise Cancellation (ANC) to microphone array signals with an intended application of background noise reduction in wind tunnels. An experiment was conducted to simulate background noise from a wind tunnel circuit measured by an out-of-flow microphone array in the tunnel test section. A reference microphone was used to acquire a background noise signal which interfered with the desired primary noise source signal at the array. The technique s efficacy was investigated using frequency spectra from the array microphones, array beamforming of the point source region, and subsequent deconvolution using the Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS) algorithm. Comparisons were made with the conventional techniques for improving SNR of spectral and Cross-Spectral Matrix subtraction. The method was seen to recover the primary signal level in SNRs as low as -29 dB and outperform the conventional methods. A second processing approach using the center array microphone as the noise reference was investigated for more general applicability of the ANC technique. It outperformed the conventional methods at the -29 dB SNR but yielded less accurate results when coherence over the array dropped. This approach could possibly improve conventional testing methodology but must be investigated further under more realistic testing conditions.

  12. Active local volume displacement cancellation of a vibrating baffled beam

    NASA Astrophysics Data System (ADS)

    Zahui, Marcellin

    An active noise control apparatus is developed. The device reduces the sound radiated from a vibrating clamped beam. The attenuation of the sound field is obtained through minimization of local volume displacements of the vibrating beam. Two single- input/single-output cancellation devices are used. Each device employs a motion sensor and an acoustic actuator. The actuator is a loudspeaker equipped with a pressure sensor to detect its volume displacement. The motion sensor signal is related to the local volume displacement of the structure which is then reduced by a loudspeaker driven with an equal but opposing volume displacement. The volume displacement sensors are developed and fabricated using Polyvinylidene Fluoride (PVDF). They measure the local volume displacements of the vibrating beam. The pressure sensor is mounted in the loudspeaker enclosure. It provides the feedback signal for the loudspeaker volume displacement control. Previous work showed the successful implementation of this technique for uniformly vibrating radiators. This thesis presents the development of this technique for the reduction of sound radiated from a vibrating beam. First, a numerical local volume displacement cancellation experiment is performed using several loudspeakers, each canceling the volume displacement of a section of the beam. The finite element method is used to calculate the velocity distribution of the vibrating beam. A discretized form of the Rayleigh integral is then used to find the sound pressure and the sound power radiated before and after cancellation. Second, the numerical results are verified by laboratory experiments using a beam divided into two sections. Two motion sensors for the beam and one pressure sensor for each loudspeaker are fabricated and thoroughly checked. The cancellation experiment is then performed on a broadband random noise using two independent Proportional-Derivative (PD) controllers.

  13. A Distributed Amplifier System for Bilayer Lipid Membrane (BLM) Arrays With Noise and Individual Offset Cancellation.

    PubMed

    Crescentini, Marco; Thei, Frederico; Bennati, Marco; Saha, Shimul; de Planque, Maurits R R; Morgan, Hywel; Tartagni, Marco

    2015-06-01

    Lipid bilayer membrane (BLM) arrays are required for high throughput analysis, for example drug screening or advanced DNA sequencing. Complex microfluidic devices are being developed but these are restricted in terms of array size and structure or have integrated electronic sensing with limited noise performance. We present a compact and scalable multichannel electrophysiology platform based on a hybrid approach that combines integrated state-of-the-art microelectronics with low-cost disposable fluidics providing a platform for high-quality parallel single ion channel recording. Specifically, we have developed a new integrated circuit amplifier based on a novel noise cancellation scheme that eliminates flicker noise derived from devices under test and amplifiers. The system is demonstrated through the simultaneous recording of ion channel activity from eight bilayer membranes. The platform is scalable and could be extended to much larger array sizes, limited only by electronic data decimation and communication capabilities.

  14. Reducing the Effects of Background Noise during Auditory Functional Magnetic Resonance Imaging of Speech Processing: Qualitative and Quantitative Comparisons between Two Image Acquisition Schemes and Noise Cancellation

    ERIC Educational Resources Information Center

    Blackman, Graham A.; Hall, Deborah A.

    2011-01-01

    Purpose: The intense sound generated during functional magnetic resonance imaging (fMRI) complicates studies of speech and hearing. This experiment evaluated the benefits of using active noise cancellation (ANC), which attenuates the level of the scanner sound at the participant's ear by up to 35 dB around the peak at 600 Hz. Method: Speech and…

  15. Enhanced Processing for a Towed Array Using an Optimal Noise Canceling Approach

    SciTech Connect

    Sullivan, E J; Candy, J V

    2005-07-21

    Noise self-generated by a surface ship towing an array in search of a weak target presents a major problem for the signal processing especially if broadband techniques are being employed. In this paper we discuss the development and application of an adaptive noise canceling processor capable of extracting the weak far-field acoustic target in a noisy ocean acoustic environment. The fundamental idea for this processor is to use a model-based approach incorporating both target and ship noise. Here we briefly describe the underlying theory and then demonstrate through simulation how effective the canceller and target enhancer perform. The adaptivity of the processor not only enables the ''tracking'' of the canceller coefficients, but also the estimation of target parameters for localization. This approach which is termed ''joint'' cancellation and enhancement produces the optimal estimate of both in a minimum (error) variance sense.

  16. Fully Integrated Low-Noise Readout Circuit with Automatic Offset Cancellation Loop for Capacitive Microsensors

    PubMed Central

    Song, Haryong; Park, Yunjong; Kim, Hyungseup; Cho, Dong-il Dan; Ko, Hyoungho

    2015-01-01

    Capacitive sensing schemes are widely used for various microsensors; however, such microsensors suffer from severe parasitic capacitance problems. This paper presents a fully integrated low-noise readout circuit with automatic offset cancellation loop (AOCL) for capacitive microsensors. The output offsets of the capacitive sensing chain due to the parasitic capacitances and process variations are automatically removed using AOCL. The AOCL generates electrically equivalent offset capacitance and enables charge-domain fine calibration using a 10-bit R-2R digital-to-analog converter, charge-transfer switches, and a charge-storing capacitor. The AOCL cancels the unwanted offset by binary-search algorithm based on 10-bit successive approximation register (SAR) logic. The chip is implemented using 0.18 μm complementary metal-oxide-semiconductor (CMOS) process with an active area of 1.76 mm2. The power consumption is 220 μW with 3.3 V supply. The input parasitic capacitances within the range of −250 fF to 250 fF can be cancelled out automatically, and the required calibration time is lower than 10 ms. PMID:26473877

  17. Fully integrated low-noise readout circuit with automatic offset cancellation loop for capacitive microsensors.

    PubMed

    Song, Haryong; Park, Yunjong; Kim, Hyungseup; Cho, Dong-Il Dan; Ko, Hyoungho

    2015-10-14

    Capacitive sensing schemes are widely used for various microsensors; however, such microsensors suffer from severe parasitic capacitance problems. This paper presents a fully integrated low-noise readout circuit with automatic offset cancellation loop (AOCL) for capacitive microsensors. The output offsets of the capacitive sensing chain due to the parasitic capacitances and process variations are automatically removed using AOCL. The AOCL generates electrically equivalent offset capacitance and enables charge-domain fine calibration using a 10-bit R-2R digital-to-analog converter, charge-transfer switches, and a charge-storing capacitor. The AOCL cancels the unwanted offset by binary-search algorithm based on 10-bit successive approximation register (SAR) logic. The chip is implemented using 0.18 μm complementary metal-oxide-semiconductor (CMOS) process with an active area of 1.76 mm². The power consumption is 220 μW with 3.3 V supply. The input parasitic capacitances within the range of -250 fF to 250 fF can be cancelled out automatically, and the required calibration time is lower than 10 ms.

  18. Fully integrated low-noise readout circuit with automatic offset cancellation loop for capacitive microsensors.

    PubMed

    Song, Haryong; Park, Yunjong; Kim, Hyungseup; Cho, Dong-Il Dan; Ko, Hyoungho

    2015-01-01

    Capacitive sensing schemes are widely used for various microsensors; however, such microsensors suffer from severe parasitic capacitance problems. This paper presents a fully integrated low-noise readout circuit with automatic offset cancellation loop (AOCL) for capacitive microsensors. The output offsets of the capacitive sensing chain due to the parasitic capacitances and process variations are automatically removed using AOCL. The AOCL generates electrically equivalent offset capacitance and enables charge-domain fine calibration using a 10-bit R-2R digital-to-analog converter, charge-transfer switches, and a charge-storing capacitor. The AOCL cancels the unwanted offset by binary-search algorithm based on 10-bit successive approximation register (SAR) logic. The chip is implemented using 0.18 μm complementary metal-oxide-semiconductor (CMOS) process with an active area of 1.76 mm². The power consumption is 220 μW with 3.3 V supply. The input parasitic capacitances within the range of -250 fF to 250 fF can be cancelled out automatically, and the required calibration time is lower than 10 ms. PMID:26473877

  19. Comparative study of adaptive-noise-cancellation algorithms for intrusion detection systems

    SciTech Connect

    Claassen, J.P.; Patterson, M.M.

    1981-01-01

    Some intrusion detection systems are susceptible to nonstationary noise resulting in frequent nuisance alarms and poor detection when the noise is present. Adaptive inverse filtering for single channel systems and adaptive noise cancellation for two channel systems have both demonstrated good potential in removing correlated noise components prior detection. For such noise susceptible systems the suitability of a noise reduction algorithm must be established in a trade-off study weighing algorithm complexity against performance. The performance characteristics of several distinct classes of algorithms are established through comparative computer studies using real signals. The relative merits of the different algorithms are discussed in the light of the nature of intruder and noise signals.

  20. Cancellation of Laser Noise in Space-Based Interferometer Detectors of Gravitational Radiation

    NASA Technical Reports Server (NTRS)

    Tinto, Massimo

    1999-01-01

    We presented a time-domain procedure for accurately cancelling laser noise fluctuations in an unequal-arm Michelson interferometer. The method involves separately measuring the phase of the returning light relative to the phase of the transmitted light in each arm. By suitable offsetting and differencing of these two time series, the common laser noise is cancelled exactly. The technique presented in this paper is general, in such that it can be implemented with any (Earth as well as space-based) unequal-arms Michelson interferometers,

  1. Cancellation of Laser Noise in an Unequal-arm Interferometer Detector of Gravitational Radiation

    NASA Technical Reports Server (NTRS)

    Tinto, M.; Armstrong, J. W.

    1998-01-01

    In this paper we present a method for exactly cancelling the laser noise in a one-bounce unequal-arm Michelson interferometer. The method requries separate measurements of the phase difference in each arm, made by interfering the returning laser light in each arm with the outgoing light.

  2. Noise cancellation in magnetoencephalography and electroencephalography with isolated reference sensors

    DOEpatents

    Kraus, Jr., Robert H.; Espy, Michelle A.; Matlachov, Andrei; Volegov, Petr

    2010-06-01

    An apparatus measures electromagnetic signals from a weak signal source. A plurality of primary sensors is placed in functional proximity to the weak signal source with an electromagnetic field isolation surface arranged adjacent the primary sensors and between the weak signal source and sources of ambient noise. A plurality of reference sensors is placed adjacent the electromagnetic field isolation surface and arranged between the electromagnetic isolation surface and sources of ambient noise.

  3. Noise-cancelling quadrature magnetic position, speed and direction sensor

    DOEpatents

    Preston, Mark A.; King, Robert D.

    1996-01-01

    An array of three magnetic sensors in a single package is employed with a single bias magnet for sensing shaft position, speed and direction of a motor in a high magnetic noise environment. Two of the three magnetic sensors are situated in an anti-phase relationship (i.e., 180.degree. out-of-phase) with respect to the relationship between the other of the two sensors and magnetically salient target, and the third magnetic sensor is situated between the anti-phase sensors. The result is quadrature sensing with noise immunity for accurate relative position, speed and direction measurements.

  4. The effect on recognition memory of noise cancelling headphones in a noisy environment with native and non-native speakers.

    PubMed

    Molesworth, Brett R C; Burgess, Marion; Gunnell, Belinda; Löffler, Diana; Venjakob, Antje

    2014-01-01

    Noise has the potential to impair cognitive performance. For nonnative speakers, the effect of noise on performance is more severe than their native counterparts. What remains unknown is the effectiveness of countermeasures such as noise attenuating devices in such circumstances. Therefore, the main aim of the present research was to examine the effectiveness of active noise attenuating countermeasures in the presence of simulated aircraft noise for both native and nonnative English speakers. Thirty-two participants, half native English speakers and half native German speakers completed four recognition (cued) recall tasks presented in English under four different audio conditions, all in the presence of simulated aircraft noise. The results of the research indicated that in simulated aircraft noise at 65 dB(A), performance of nonnative English speakers was poorer than for native English speakers. The beneficial effects of noise cancelling headphones in improving the signal to noise ratio led to an improved performance for nonnative speakers. These results have particular importance for organizations operating in a safety-critical environment such as aviation. PMID:25033791

  5. The effect on recognition memory of noise cancelling headphones in a noisy environment with native and non-native speakers.

    PubMed

    Molesworth, Brett R C; Burgess, Marion; Gunnell, Belinda; Löffler, Diana; Venjakob, Antje

    2014-01-01

    Noise has the potential to impair cognitive performance. For nonnative speakers, the effect of noise on performance is more severe than their native counterparts. What remains unknown is the effectiveness of countermeasures such as noise attenuating devices in such circumstances. Therefore, the main aim of the present research was to examine the effectiveness of active noise attenuating countermeasures in the presence of simulated aircraft noise for both native and nonnative English speakers. Thirty-two participants, half native English speakers and half native German speakers completed four recognition (cued) recall tasks presented in English under four different audio conditions, all in the presence of simulated aircraft noise. The results of the research indicated that in simulated aircraft noise at 65 dB(A), performance of nonnative English speakers was poorer than for native English speakers. The beneficial effects of noise cancelling headphones in improving the signal to noise ratio led to an improved performance for nonnative speakers. These results have particular importance for organizations operating in a safety-critical environment such as aviation.

  6. Active noise control: A tutorial for HVAC designers

    SciTech Connect

    Gelin, L.J.

    1997-08-01

    This article will identify the capabilities and limitations of ANC in its application to HVAC noise control. ANC can be used in ducted HVAC systems to cancel ductborne, low-frequency fan noise by injecting sound waves of equal amplitude and opposite phase into an air duct, as close as possible to the source of the unwanted noise. Destructive interference of the fan noise and injected noise results in sound cancellation. The noise problems that it solves are typically described as rumble, roar or throb, all of which are difficult to address using traditional noise control methods. This article will also contrast the use of active against passive noise control techniques. The main differences between the two noise control measures are acoustic performance, energy consumption, and design flexibility. The article will first present the fundamentals and basic physics of ANC. The application to real HVAC systems will follow.

  7. Algebraic cancellation of polarisation noise in fibre interferometers.

    PubMed

    McRae, Terry G; Ngo, Silvie; Lam, Timothy T-Y; McClelland, David E; Chow, Jong H; Shaddock, Daniel A; Gray, Malcolm B

    2016-05-16

    This experiment uses digital interferometry to reduce polarisation noise from a fiber interferometer to the level of double Rayleigh backscatter making precision fiber metrology systems robust for remote field applications. This is achieved with a measurement of the Jones matrix with interferometric sensitivity in real time, limited only by fibre length and processing bandwidth. This new approach leads to potentially new metrology applications and the ability to do ellipsometry without polarisation elements in the output field. PMID:27409872

  8. Active noise reduction

    NASA Astrophysics Data System (ADS)

    Carter, J.

    1984-01-01

    Active Noise Reduction (ANR) techniques, singly and in combination with passive hearing protectors, offer the potential for increased sound protection, enhanced voice communications and improved wearability features for personnel exposed to unacceptable noise conditions. An enhanced closed loop active noise reduction system was miniaturized and incorporated into a standard Air Force flight helmet (HGU-26/P). This report describes the theory of design and operation, prototype configuration and operation, and electroacoustic performance and specifications for the ANR system. This system is theoretically capable of producing in excess of 30 decibels of active noise reduction. Electroacoustic measurements on a flat plate coupler demonstrated approximately 20 decibels of active noise reduction with the prototype unit. A performance evaluation of the integrated ANR unit will be conducted under laboratory and field conditions by government personnel to determine the feasibility of the system for use in military applications.

  9. An OFDM Receiver with Frequency Domain Diversity Combined Impulsive Noise Canceller for Underwater Network.

    PubMed

    Saotome, Rie; Hai, Tran Minh; Matsuda, Yasuto; Suzuki, Taisaku; Wada, Tomohisa

    2015-01-01

    In order to explore marine natural resources using remote robotic sensor or to enable rapid information exchange between ROV (remotely operated vehicles), AUV (autonomous underwater vehicle), divers, and ships, ultrasonic underwater communication systems are used. However, if the communication system is applied to rich living creature marine environment such as shallow sea, it suffers from generated Impulsive Noise so-called Shrimp Noise, which is randomly generated in time domain and seriously degrades communication performance in underwater acoustic network. With the purpose of supporting high performance underwater communication, a robust digital communication method for Impulsive Noise environments is necessary. In this paper, we propose OFDM ultrasonic communication system with diversity receiver. The main feature of the receiver is a newly proposed Frequency Domain Diversity Combined Impulsive Noise Canceller. The OFDM receiver utilizes 20-28 KHz ultrasonic channel and subcarrier spacing of 46.875 Hz (MODE3) and 93.750 Hz (MODE2) OFDM modulations. In addition, the paper shows Impulsive Noise distribution data measured at a fishing port in Okinawa and at a barge in Shizuoka prefectures and then proposed diversity OFDM transceivers architecture and experimental results are described. By the proposed Impulsive Noise Canceller, frame bit error rate has been decreased by 20-30%. PMID:26351656

  10. An OFDM Receiver with Frequency Domain Diversity Combined Impulsive Noise Canceller for Underwater Network.

    PubMed

    Saotome, Rie; Hai, Tran Minh; Matsuda, Yasuto; Suzuki, Taisaku; Wada, Tomohisa

    2015-01-01

    In order to explore marine natural resources using remote robotic sensor or to enable rapid information exchange between ROV (remotely operated vehicles), AUV (autonomous underwater vehicle), divers, and ships, ultrasonic underwater communication systems are used. However, if the communication system is applied to rich living creature marine environment such as shallow sea, it suffers from generated Impulsive Noise so-called Shrimp Noise, which is randomly generated in time domain and seriously degrades communication performance in underwater acoustic network. With the purpose of supporting high performance underwater communication, a robust digital communication method for Impulsive Noise environments is necessary. In this paper, we propose OFDM ultrasonic communication system with diversity receiver. The main feature of the receiver is a newly proposed Frequency Domain Diversity Combined Impulsive Noise Canceller. The OFDM receiver utilizes 20-28 KHz ultrasonic channel and subcarrier spacing of 46.875 Hz (MODE3) and 93.750 Hz (MODE2) OFDM modulations. In addition, the paper shows Impulsive Noise distribution data measured at a fishing port in Okinawa and at a barge in Shizuoka prefectures and then proposed diversity OFDM transceivers architecture and experimental results are described. By the proposed Impulsive Noise Canceller, frame bit error rate has been decreased by 20-30%.

  11. An OFDM Receiver with Frequency Domain Diversity Combined Impulsive Noise Canceller for Underwater Network

    PubMed Central

    Saotome, Rie; Hai, Tran Minh; Matsuda, Yasuto; Suzuki, Taisaku; Wada, Tomohisa

    2015-01-01

    In order to explore marine natural resources using remote robotic sensor or to enable rapid information exchange between ROV (remotely operated vehicles), AUV (autonomous underwater vehicle), divers, and ships, ultrasonic underwater communication systems are used. However, if the communication system is applied to rich living creature marine environment such as shallow sea, it suffers from generated Impulsive Noise so-called Shrimp Noise, which is randomly generated in time domain and seriously degrades communication performance in underwater acoustic network. With the purpose of supporting high performance underwater communication, a robust digital communication method for Impulsive Noise environments is necessary. In this paper, we propose OFDM ultrasonic communication system with diversity receiver. The main feature of the receiver is a newly proposed Frequency Domain Diversity Combined Impulsive Noise Canceller. The OFDM receiver utilizes 20–28 KHz ultrasonic channel and subcarrier spacing of 46.875 Hz (MODE3) and 93.750 Hz (MODE2) OFDM modulations. In addition, the paper shows Impulsive Noise distribution data measured at a fishing port in Okinawa and at a barge in Shizuoka prefectures and then proposed diversity OFDM transceivers architecture and experimental results are described. By the proposed Impulsive Noise Canceller, frame bit error rate has been decreased by 20–30%. PMID:26351656

  12. Benign paroxysmal positional vertigo after use of noise-canceling headphones.

    PubMed

    Dan-Goor, Eric; Samra, Monica

    2012-01-01

    Benign paroxysmal positional vertigo (BPPV) is a common cause of vertigo. We describe a case of a woman presenting acutely with a severe episode of disabling positional vertigo. Although she had no known etiologic risk factors, this attack followed 12 hours of continuously wearing digital noise-canceling headphones. This is the first such reported association between BPPV and the use of this gadget. We also provide a short review of BPPV and speculate on the possible pathogenic mechanisms involved.

  13. Assessing the efficacy of active noise reduction

    NASA Astrophysics Data System (ADS)

    Rylands, Julia M.

    Active noise reduction (ANR) is an electronic technique, based on reverse phase cancellation, for reducing low frequency noise reaching an operators ears. This report discussed the basic concept, its capabilities and some approaches to assessing its efficacy. The technique provides a great enhancement to hearing protection and also enhances signal detection and communications capabilities. Tests of detectibility of pure tones at frequencies ranging up to 1750 Hz using ANR systems which had maximum noise attenuation between 300 and 600 Hz and masking noise typical of the SeaKing helicopter showed that improvements in detection performance extend up to 1000 Hz. ANR systems also offer improved speech intelligibility in high noise environments by reducing the upward spread of masking and adding speech pre-emphasis.

  14. System and method for motor fault detection using stator current noise cancellation

    DOEpatents

    Zhou, Wei; Lu, Bin; Nowak, Michael P.; Dimino, Steven A.

    2010-12-07

    A system and method for detecting incipient mechanical motor faults by way of current noise cancellation is disclosed. The system includes a controller configured to detect indicia of incipient mechanical motor faults. The controller further includes a processor programmed to receive a baseline set of current data from an operating motor and define a noise component in the baseline set of current data. The processor is also programmed to acquire at least on additional set of real-time operating current data from the motor during operation, redefine the noise component present in each additional set of real-time operating current data, and remove the noise component from the operating current data in real-time to isolate any fault components present in the operating current data. The processor is then programmed to generate a fault index for the operating current data based on any isolated fault components.

  15. Noise cancellation model validation for reduced motion artifact wearable PPG sensors using MEMS accelerometers.

    PubMed

    Wood, Levi B; Asada, H Harry

    2006-01-01

    This paper investigates the validity of utilizing Widrow's Active Noise Cancellation (ANC) in the context of motion artifact reduction for photoplethysmogram (PPG) sensors. The ANC approach has previously been applied to the PPG problem, but little consideration has been given to the validity of the ANC signal corruption assumptions and in what motion range the algorithm works. The ANC validity testing is done in the form of impact (approximate impulse) testing of the physical PPG system and comparing with the modeled response for a range of motion amplitudes. The testing reveals that the identified corruption model does not generally represent the true physical system, but locally approximates the true system. Testing shows that if a similar motion amplitude is used for model tuning as the impact test, an average peak deviation of 5.2% is obtained, but if motion amplitude that is smaller than the impact amplitude by a factor of 5, the peak deviation is 15%. Finally, after ANC filtering motion corrupted data, heart rate can be estimated with less than 1.6% error.

  16. 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.

  17. Transform Domain Robust Variable Step Size Griffiths' Adaptive Algorithm for Noise Cancellation in ECG

    NASA Astrophysics Data System (ADS)

    Hegde, Veena; Deekshit, Ravishankar; Satyanarayana, P. S.

    2011-12-01

    The electrocardiogram (ECG) is widely used for diagnosis of heart diseases. Good quality of ECG is utilized by physicians for interpretation and identification of physiological and pathological phenomena. However, in real situations, ECG recordings are often corrupted by artifacts or noise. Noise severely limits the utility of the recorded ECG and thus needs to be removed, for better clinical evaluation. In the present paper a new noise cancellation technique is proposed for removal of random noise like muscle artifact from ECG signal. A transform domain robust variable step size Griffiths' LMS algorithm (TVGLMS) is proposed for noise cancellation. For the TVGLMS, the robust variable step size has been achieved by using the Griffiths' gradient which uses cross-correlation between the desired signal contaminated with observation or random noise and the input. The algorithm is discrete cosine transform (DCT) based and uses symmetric property of the signal to represent the signal in frequency domain with lesser number of frequency coefficients when compared to that of discrete Fourier transform (DFT). The algorithm is implemented for adaptive line enhancer (ALE) filter which extracts the ECG signal in a noisy environment using LMS filter adaptation. The proposed algorithm is found to have better convergence error/misadjustment when compared to that of ordinary transform domain LMS (TLMS) algorithm, both in the presence of white/colored observation noise. The reduction in convergence error achieved by the new algorithm with desired signal decomposition is found to be lower than that obtained without decomposition. The experimental results indicate that the proposed method is better than traditional adaptive filter using LMS algorithm in the aspects of retaining geometrical characteristics of ECG signal.

  18. Nonuniformity correction algorithm based on a noise-cancellation system for infrared focal-plane arrays

    NASA Astrophysics Data System (ADS)

    Godoy, Sebastian E.; Torres, Sergio N.; Pezoa, Jorge E.; Hayat, Majeed M.; Wang, Qi

    2007-04-01

    In this paper a novel nonuniformity correction method that compensates for the fixed-pattern noise (FPN) in infrared focal-plane array (IRFPA) sensors is developed. The proposed NUC method compensates for the additive component of the FPN statistically processing the read-out signal using a noise-cancellation system. The main assumption of the method is that a source of noise correlated to the additive noise of the IRFPA is available to the system. Under this assumption, a finite impulse response (FIR) filter is designed to synthesize an estimate of the additive noise. Moreover, exploiting the fact that the assumed source of noise is constant in time, we derive a simple expression to calculate the estimate of the additive noise. Finally, the estimate is subtracted to the raw IR imagery to obtain the corrected version of the images. The performance of the proposed system and its ability to compensate for the FPN are tested with infrared images corrupted by both real and simulated nonuniformity.

  19. Cancellation of lateral displacement noise of three-port gratings for coupling light to cavities.

    PubMed

    Meinders, Melanie; Kroker, Stefanie; Singh, Amrit Pal; Kley, E-Bernhard; Tünnermann, Andreas; Danzmann, Karsten; Schnabel, Roman

    2015-05-01

    Reflection gratings enable light coupling to optical cavities without transmission through substrates. Gratings that have three ports and are mounted in a second-order Littrow configuration even allow the coupling to high-finesse cavities using low diffraction efficiencies. In contrast to conventional transmissive cavity couplers, however, the phase of the diffracted light depends on the lateral position of the grating, which introduces an additional noise coupling. Here, we experimentally demonstrate that this kind of noise cancels out once both diffracted output ports of the grating are combined. We achieve the same signal-to-shot-noise ratio as for a conventional coupler. From this perspective, three-port grating couplers in a second-order Littrow configuration remain a valuable approach to reducing optical absorption of cavity coupler substrates in future gravitational-wave detectors. PMID:25927782

  20. System and method for bearing fault detection using stator current noise cancellation

    DOEpatents

    Zhou, Wei; Lu, Bin; Habetler, Thomas G.; Harley, Ronald G.; Theisen, Peter J.

    2010-08-17

    A system and method for detecting incipient mechanical motor faults by way of current noise cancellation is disclosed. The system includes a controller configured to detect indicia of incipient mechanical motor faults. The controller further includes a processor programmed to receive a baseline set of current data from an operating motor and define a noise component in the baseline set of current data. The processor is also programmed to repeatedly receive real-time operating current data from the operating motor and remove the noise component from the operating current data in real-time to isolate any fault components present in the operating current data. The processor is then programmed to generate a fault index for the operating current data based on any isolated fault components.

  1. Hardware Verification of Laser Noise Cancellation and Gravitational Wave Extraction using Time-Delay Interferometry

    NASA Astrophysics Data System (ADS)

    Mitryk, Shawn; Mueller, Guido

    The Laser Interferometer Space Antenna (LISA) is a space-based modified Michelson interfer-ometer designed to measure gravitational radiation in the frequency range from 30 uHz to 1 Hz. The interferometer measurement system (IMS) utilizes one-way laser phase measurements to cancel the laser phase noise, reconstruct the proof-mass motion, and extract the gravitational wave (GW) induced laser phase modulations in post-processing using a technique called time-delay interferometry (TDI). Unfortunately, there exist few hard-ware verification experiments of the IMS. The University of Florida LISA Interferometry Simulator (UFLIS) is designed to perform hardware-in-the-loop simulations of the LISA interferometry system, modeling the characteris-tics of the LISA mission as accurately as possible. This depends, first, on replicating the laser pre-stabilization by locking the laser phase to an ultra-stable Zerodur cavity length reference using the PDH locking method. Phase measurements of LISA-like photodetector beat-notes are taken using the UF-phasemeter (PM) which can measure the laser BN frequency to within an accuracy of 0.22 uHz. The inter-space craft (SC) laser links including the time-delay due to the 5 Gm light travel time along the LISA arms, the laser Doppler shifts due to differential SC motion, and the GW induced laser phase modulations are simulated electronically using the electronic phase delay (EPD) unit. The EPD unit replicates the laser field propagation between SC by measuring a photodetector beat-note frequency with the UF-phasemeter and storing the information in memory. After the requested delay time, the frequency information is added to a Doppler offset and a GW-like frequency modulation. The signal is then regenerated with the inter-SC laser phase affects applied. Utilizing these components, I will present the first complete TDI simulations performed using the UFLIS. The LISA model is presented along-side the simulation, comparing the generation and

  2. Active control of environmental noise, VIII: increasing the response to primary source changes including unpredictable noise

    NASA Astrophysics Data System (ADS)

    Wright, S. E.; Atmoko, H.; Vuksanovic, B.

    2004-07-01

    Conventional adaptive cancellation systems using traditional transverse finite impulse response (FIR) filters, together with least mean square (LMS) adaptive algorithms, well known in active noise control, are slow to adapt to primary source changes. This makes them inappropriate for cancelling rapidly changing noise, including unpredictable noise such as speech and music. Secondly, the cancelling structures require considerable computational processing effort to adapt to primary source and plant changes, particularly for multi-channel systems. This paper describes methods to increase the adaptive speed to primary source changes in large enclosed spaces and outdoor environments. A method is described that increases the response to time varying periodic noise using traditional transverse FIR filters. Here a multi-passband filter, with individual variable adaptive step sizes for each passband is automatically adjusted according to the signal level in each band. This creates a similar adaptive response for all frequencies within the total pass-band, irrespective of amplitude, minimizing the signal distortion and increasing the combined adaptive speed. Unfortunately, there is a limit to the adaptive speed using the above method as classical transverse FIR filters have a finite adaptive speed given by the stability band zero bandwidth. For rapidly changing periodic noise and unpredictable non-stationary noise, a rapid to instantaneous response is required. In this case the on-line adaptive FIR filters are dispensed with and replaced by a time domain solution that gives virtually instantaneous cancellation response (infinite adaptive speed) to primary source changes, and is computationally efficient.

  3. Newtonian-noise cancellation in full-tensor gravitational-wave detectors

    NASA Astrophysics Data System (ADS)

    Harms, Jan; Paik, Ho Jung

    2015-07-01

    Terrestrial gravity noise, also known as Newtonian noise, produced by ambient seismic and infrasound fields will pose one of the main sensitivity limitations in low-frequency, ground-based, gravitational-wave (GW) detectors. It is estimated that this noise foreground needs to be suppressed by about 3-5 orders of magnitude in the frequency band 10 mHz to 1 Hz, which will be extremely challenging. In this article, we present a new approach that greatly facilitates cancellation of gravity noise in full-tensor GW detectors. The method uses optimal combinations of tensor channels and environmental sensors such as seismometers and microphones to reduce gravity noise. It makes explicit use of the direction of propagation of a GW and can, therefore, either be implemented in directional searches for GWs or in observations of known sources. We show that by using the extra strain channels in full-tensor GW detectors and a modest number of environmental sensors, the Newtonian-noise foreground can be reduced by a few orders of magnitude independent of the GW direction of propagation.

  4. Force sensing based on coherent quantum noise cancellation in a hybrid optomechanical cavity with squeezed-vacuum injection

    NASA Astrophysics Data System (ADS)

    Motazedifard, Ali; Bemani, F.; Naderi, M. H.; Roknizadeh, R.; Vitali, D.

    2016-07-01

    We propose and analyse a feasible experimental scheme for a quantum force sensor based on the elimination of backaction noise through coherent quantum noise cancellation (CQNC) in a hybrid atom-cavity optomechanical setup assisted with squeezed vacuum injection. The force detector, which allows for a continuous, broadband detection of weak forces well below the standard quantum limit (SQL), is formed by a single optical cavity simultaneously coupled to a mechanical oscillator and to an ensemble of ultracold atoms. The latter acts as a negative-mass oscillator so that atomic noise exactly cancels the backaction noise from the mechanical oscillator due to destructive quantum interference. Squeezed vacuum injection enforces this cancellation and allows sub-SQL sensitivity to be reached in a very wide frequency band, and at much lower input laser powers.

  5. Cancellation of simulated environmental noise as a tool for measuring vocal performance during noise exposure.

    PubMed

    Ternström, Sten; Södersten, Maria; Bohman, Mikael

    2002-06-01

    It can be difficult for the voice clinician to observe or measure how a patient uses his voice in a noisy environment. We consider here a novel method for obtaining this information in the laboratory. Worksite noise and filtered white noise were reproduced over high-fidelity loudspeakers. In this noise, 11 subjects read an instructional text of 1.5 to 2 minutes duration, as if addressing a group of people. Using channel estimation techniques, the site noise was suppressed from the recording, and the voice signal alone was recovered. The attainable noise rejection is limited only by the precision of the experimental setup, which includes the need for the subject to remain still so as not to perturb the estimated acoustic channel. This feasibility study, with 7 female and 4 male subjects, showed that small displacements of the speaker's body, even breathing, impose a practical limit on the attainable noise rejection. The noise rejection was typically 30 dB and maximally 40 dB down over the entire voice spectrum. Recordings thus processed were clean enough to permit voice analysis with the long-time average spectrum and the computerized phonetogram. The effects of site noise on voice sound pressure level, fundamental frequency, long-term average spectrum centroid, phonetogram area, and phonation time were much as expected, but with some interesting differences between females and males.

  6. Blood pressure measurement in noise intensive environments using adaptive interference cancellation.

    PubMed

    Pinto, Lisa; Dhanantwari, Amar; Wong, Winnie; Stergiopoulos, Stergios; Maris, Mike

    2002-05-01

    The traditional auscultatory technique and current methodologies for measuring human blood pressure are limited when used in situations where extreme vibration or acoustic noise is present. In this study, human subjects were used to establish the effectiveness of a novel adaptive blood pressure monitoring (ABPM) system in determining systolic-diastolic pressure in vibration and noise intense environments. To remove the effects of noise and vibration from the audible Korotkoff sounds, the proposed ABPM system employs two acoustic sensors in the pressure cuff. The primary acoustic sensor is placed on the brachial artery to record the Korotkoff sounds while the secondary acoustic sensor is placed away from the artery to record background noise and vibrations. The signals from the two acoustic sensors are provided to the input of an adaptive interference canceller to remove the noise effects in the signal of the primary acoustic sensor. In two phases of clinical testing, the ABPM system was first employed in a noiseless environment and then near and onboard search and rescue helicopters. The results from both phases deliver a successful demonstration of the ABPM system's capabilities to provide blood pressure estimates in noisy environments where the conventional auscultatory and other techniques have limited use.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  8. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  10. 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.

  11. Adaptive HIFU noise cancellation for simultaneous therapy and imaging using an integrated HIFU/imaging transducer

    PubMed Central

    Jeong, Jong Seob; Cannata, Jonathan Matthew; Shung, K Kirk

    2010-01-01

    It was previously demonstrated that it is feasible to simultaneously perform ultrasound therapy and imaging of a coagulated lesion during treatment with an integrated transducer that is capable of high intensity focused ultrasound (HIFU) and B-mode ultrasound imaging. It was found that coded excitation and fixed notch filtering upon reception could significantly reduce interference caused by the therapeutic transducer. During HIFU sonication, the imaging signal generated with coded excitation and fixed notch filtering had a range side-lobe level of less than −40 dB, while traditional short-pulse excitation and fixed notch filtering produced a range side-lobe level of −20 dB. The shortcoming is, however, that relatively complicated electronics may be needed to utilize coded excitation in an array imaging system. It is for this reason that in this paper an adaptive noise canceling technique is proposed to improve image quality by minimizing not only the therapeutic interference, but also the remnant side-lobe ‘ripples’ when using the traditional short-pulse excitation. The performance of this technique was verified through simulation and experiments using a prototype integrated HIFU/imaging transducer. Although it is known that the remnant ripples are related to the notch attenuation value of the fixed notch filter, in reality, it is difficult to find the optimal notch attenuation value due to the change in targets or the media resulted from motion or different acoustic properties even during one sonication pulse. In contrast, the proposed adaptive noise canceling technique is capable of optimally minimizing both the therapeutic interference and residual ripples without such constraints. The prototype integrated HIFU/imaging transducer is composed of three rectangular elements. The 6 MHz center element is used for imaging and the outer two identical 4 MHz elements work together to transmit the HIFU beam. Two HIFU elements of 14.4 mm × 20.0 mm dimensions

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  13. Joint application of a statistical optimization process and Empirical Mode Decomposition to Magnetic Resonance Sounding Noise Cancelation

    NASA Astrophysics Data System (ADS)

    Ghanati, Reza; Fallahsafari, Mahdi; Hafizi, Mohammad Kazem

    2014-12-01

    The signal quality of Magnetic Resonance Sounding (MRS) measurements is a crucial criterion. The accuracy of the estimation of the signal parameters (i.e. E0 and T2*) strongly depends on amplitude and conditions of ambient electromagnetic interferences at the site of investigation. In this paper, in order to enhance the performance in the noisy environments, a two-step noise cancelation approach based on the Empirical Mode Decomposition (EMD) and a statistical method is proposed. In the first stage, the noisy signal is adaptively decomposed into intrinsic oscillatory components called intrinsic mode functions (IMFs) by means of the EMD algorithm. Afterwards based on an automatic procedure the noisy IMFs are detected, and then the partly de-noised signal is reconstructed through the no-noise IMFs. In the second stage, the signal obtained from the initial section enters an optimization process to cancel the remnant noise, and consequently, estimate the signal parameters. The strategy is tested on a synthetic MRS signal contaminated with Gaussian noise, spiky events and harmonic noise, and on real data. By applying successively the proposed steps, we can remove the noise from the signal to a high extent and the performance indexes, particularly signal to noise ratio, will increase significantly.

  14. Study of active noise control system for a commercial HVAC unit

    NASA Astrophysics Data System (ADS)

    Devineni, Naga

    Acoustic noise is a common problem in everyday life. If the appliances that are present in the work and living areas generate noise then it's a serious problem. One such appliance is the Heating, Ventilation and Air-conditioning system (HVAC) in which blower fan and compressor units are housed together. Operation of a HVAC system creates two kinds of noise. One is the noise due to the air flow and the other is the result of the compressor. Both of them exhibit different signal properties and need different strategies to control them. There has been previous efforts in designing noise control systems that can control noise from the HVAC system. These include passive methods which use sound absorption materials to attenuate noise and active methods which cancel noise by generating anti-noise. Passive methods are effective in limiting the high frequency noise, but are inefficient in controlling low frequency noise from the compressor. Compressor noise is one of the strong low frequency components that propagate through the walls, therefore there is need for deploying active signal processing methods that consider the signal properties into consideration to cancel the noise acoustically. The quasi periodic nature of the compressor noise is exploited in noise modeling which aids in implementing an adaptive linear prediction filter in estimating the anti noise [12]. In this thesis, a multi channel architecture has been studied for a specific HVAC system in order to improve noise cancellation by creating larger quiet zone. In addition to the multi-channel architecture, a real time narrow band Active Noise Control (ANC) was employed to cancel noise under practical conditions.

  15. Phase noise tolerant inter-carrier-interference cancellation for WDM superchannels with sub-Nyquist channel spacing.

    PubMed

    Yao, Shuchang; Fu, Songnian; Li, Jianqiang; Tang, Ming; Shum, Perry; Liu, Deming

    2013-09-01

    We propose and demonstrate a novel multi-input multi-output (MIMO) equalization based inter-carrier-interference (ICI) cancellation approach employing constant modulus algorithm (CMA) for supperchanels with sub-Nyquist channel spacing, where optical combs are used as optical sources. Compared with the least mean square (LMS) algorithm based ICI canceller, the proposed approach has comparable capability to accomplish the ICI mitigation for 56 Gbaud dual-polarization quadrature phase shift keying (DP-QPSK) signals with tight channel spacing till 50 GHz. In particular, compared with the LMS-MIMO based ICI canceller, the optical linewidth tolerance of 6 MHz is relaxed to 20 MHz given a 1dB required optical signal-to-noise ratio (OSNR) penalty for the CMA-MIMO based ICI canceller. Meanwhile, the CMA-MIMO based ICI canceller is ideal for real-time processing, since the number of parallel processing pipelines can be greater than 240 even in the presence of large linewidth.

  16. Bearing fault diagnosis under unknown variable speed via gear noise cancellation and rotational order sideband identification

    NASA Astrophysics Data System (ADS)

    Wang, Tianyang; Liang, Ming; Li, Jianyong; Cheng, Weidong; Li, Chuan

    2015-10-01

    The interfering vibration signals of a gearbox often represent a challenging issue in rolling bearing fault detection and diagnosis, particularly under unknown variable rotational speed conditions. Though some methods have been proposed to remove the gearbox interfering signals based on their discrete frequency nature, such methods may not work well under unknown variable speed conditions. As such, we propose a new approach to address this issue. The new approach consists of three main steps: (a) adaptive gear interference removal, (b) fault characteristic order (FCO) based fault detection, and (c) rotational-order-sideband (ROS) based fault type identification. For gear interference removal, an enhanced adaptive noise cancellation (ANC) algorithm has been developed in this study. The new ANC algorithm does not require an additional accelerometer to provide reference input. Instead, the reference signal is adaptively constructed from signal maxima and instantaneous dominant meshing multiple (IDMM) trend. Key ANC parameters such as filter length and step size have also been tailored to suit the variable speed conditions, The main advantage of using ROS for fault type diagnosis is that it is insusceptible to confusion caused by the co-existence of bearing and gear rotational frequency peaks in the identification of the bearing fault characteristic frequency in the FCO sub-order region. The effectiveness of the proposed method has been demonstrated using both simulation and experimental data. Our experimental study also indicates that the proposed method is applicable regardless whether the bearing and gear rotational speeds are proportional to each other or not.

  17. Voice communications in the cockpit noise environment: The role of active noise reduction

    NASA Astrophysics Data System (ADS)

    Wheeler, Peter David

    The topic of voice communications in the cockpit noise environment of modern fast-jet aircraft and helicopters is addressed, and in particular, research undertaken in support of the development of a system for reducing the noise level at the operators' ear is described by acoustic cancellation within the ear defender, known as active noise reduction (ANR). The internal noise spectra of today's high performance fast-jet aircraft and military helicopters is described, and the complex interaction of acoustic noise transmission, speech, and microphone noise pick-up, which produces the total acoustic environment at the aircrews' ears, is discussed. Means of mathematically modelling the audio channel, quantifying the components identified above, and identifying areas of shortfall in performance are derived, leading to a procedure for the development of attenuation requirements, described as the communications audit. A model of the electroacoustic characteristics of the ANR ear defender assembly is presented and the sound field distribution within the ear defender/ear cavity, and its effect upon cancellation performance, is discussed. The extensive laboratory and flight testing of the ANR system that was undertaken is reviewed, paying particular attention to the measurement and analysis techniques employed in such testing. Finally, the performance characteristics of ANR are discussed and compared with the requirements previously established. Design limitations placed upon the system by the constraints of its area of application are described, and the scope for future improvements is considered.

  18. EEG/ERP adaptive noise canceller design with controlled search space (CSS) approach in cuckoo and other optimization algorithms.

    PubMed

    Ahirwal, M K; Kumar, Anil; Singh, G K

    2013-01-01

    This paper explores the migration of adaptive filtering with swarm intelligence/evolutionary techniques employed in the field of electroencephalogram/event-related potential noise cancellation or extraction. A new approach is proposed in the form of controlled search space to stabilize the randomness of swarm intelligence techniques especially for the EEG signal. Swarm-based algorithms such as Particles Swarm Optimization, Artificial Bee Colony, and Cuckoo Optimization Algorithm with their variants are implemented to design optimized adaptive noise canceler. The proposed controlled search space technique is tested on each of the swarm intelligence techniques and is found to be more accurate and powerful. Adaptive noise canceler with traditional algorithms such as least-mean-square, normalized least-mean-square, and recursive least-mean-square algorithms are also implemented to compare the results. ERP signals such as simulated visual evoked potential, real visual evoked potential, and real sensorimotor evoked potential are used, due to their physiological importance in various EEG studies. Average computational time and shape measures of evolutionary techniques are observed 8.21E-01 sec and 1.73E-01, respectively. Though, traditional algorithms take negligible time consumption, but are unable to offer good shape preservation of ERP, noticed as average computational time and shape measure difference, 1.41E-02 sec and 2.60E+00, respectively.

  19. Application of Noise Cancelling and Damage Detection Algorithms in NDE of Concrete Bridge Decks Using Impact Signals

    SciTech Connect

    Zhang, Gang; Harichandran, Ronald S.; Ramuhalli, Pradeep

    2011-09-13

    Delamination is a commonly observed distress in concrete bridge decks. Among all the delamination detection methods, acoustic methods have the advantages of being fast and inexpensive. In traditional acoustic inspection methods, the inspector drags a chain along or hammers on the bridge deck and detects delamination from the 'hollowness' of the sounds. The signals are often contaminated by ambient traffic noise and the detection of delamination is highly subjective. This paper describes the performance of an impact-bases acoustic NDE method where the traffic noise was filtered by employing a noise cancelling algorithm and where subjectivity was eliminated by introducing feature extraction and pattern recognition algorithms. Different algorithms were compared and the best one was selected in each category. The comparison showed that the modified independent component analysis (ICA) algorithm was most effective in cancelling the traffic noise and features consisting of mel-frequency cepstral coefficients (MFCCs) had the best performance in terms of repeatability and separabillty. The condition of the bridge deck was then detected by a radial basis function (RBF) neural network. The performance of the system was evaluated using both experimental and field data. The results show that the selected algorithms increase the noise robustness of acoustic methods and perform satisfactorily if the training data is representative.

  20. The effect of losses on the quantum-noise cancellation in the SU(1,1) interferometer

    NASA Astrophysics Data System (ADS)

    Xin, Jun; Wang, Hailong; Jing, Jietai

    2016-08-01

    Quantum-noise cancellation (QNC) is an effective method to control the noise of the quantum system, which reduces or even eliminates the noise of the quantum systems by utilizing destructive interference in the quantum system. However, QNC can be extremely dependent on the losses inside the system. In this letter, we experimentally and theoretically study how the losses can affect the QNC in the SU(1,1) interferometer. We find that losses in the different arms inside the SU(1,1) interferometer can have different effects on the QNC in the output fields from the SU(1,1) interferometer. And the QNC in the SU(1,1) interferometer can almost be insensitive to the losses in some cases. Our findings may find its potential applications in the quantum noise control.

  1. 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.

  2. Using A-weighting for psychoacoustic active noise control.

    PubMed

    Bao, Hua; Panahi, Issa M S

    2009-01-01

    Conventional adaptive active noise control (ANC) methods aim to attenuate the acoustic noise over the frequency band of interest indiscriminately using the sound pressure level (SPL) measurement (or the measurement of the residual error variance). However, SPL does not correctly reflect the human perception of attenuated noise due to the frequency selective sensitivity of human hearing system. A-weighting is a commonly used weighting filter for measuring the noise. This weighting filter quantifies frequency response of the human ears and hearing system. In this paper, we aim to improve the performance of adaptive noise cancellation method from the psychoacoustic point of view by incorporating the A-weighting into the ANC system design. Loudness is used as the psychoacoustic criterion for evaluating the ANC system performance. Simulation results illustrate the effectiveness of the proposed method. PMID:19963645

  3. 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.

  4. SVD-Based Technique for Interference Cancellation and Noise Reduction in NMR Measurement of Time-Dependent Magnetic Fields.

    PubMed

    Chen, Wenjun; Ma, Hong; Yu, De; Zhang, Hua

    2016-03-04

    A nuclear magnetic resonance (NMR) experiment for measurement of time-dependent magnetic fields was introduced. To improve the signal-to-interference-plus-noise ratio (SINR) of NMR data, a new method for interference cancellation and noise reduction (ICNR) based on singular value decomposition (SVD) was proposed. The singular values corresponding to the radio frequency interference (RFI) signal were identified in terms of the correlation between the FID data and the reference data, and then the RFI and noise were suppressed by setting the corresponding singular values to zero. The validity of the algorithm was verified by processing the measured NMR data. The results indicated that, this method has a significantly suppression of RFI and random noise, and can well preserve the FID signal. At present, the major limitation of the proposed SVD-based ICNR technique is that the threshold value for interference cancellation needs to be manually selected. Finally, the inversion waveform of the applied alternating magnetic field was given by fitting the processed experimental data.

  5. SVD-Based Technique for Interference Cancellation and Noise Reduction in NMR Measurement of Time-Dependent Magnetic Fields

    PubMed Central

    Chen, Wenjun; Ma, Hong; Yu, De; Zhang, Hua

    2016-01-01

    A nuclear magnetic resonance (NMR) experiment for measurement of time-dependent magnetic fields was introduced. To improve the signal-to-interference-plus-noise ratio (SINR) of NMR data, a new method for interference cancellation and noise reduction (ICNR) based on singular value decomposition (SVD) was proposed. The singular values corresponding to the radio frequency interference (RFI) signal were identified in terms of the correlation between the FID data and the reference data, and then the RFI and noise were suppressed by setting the corresponding singular values to zero. The validity of the algorithm was verified by processing the measured NMR data. The results indicated that, this method has a significantly suppression of RFI and random noise, and can well preserve the FID signal. At present, the major limitation of the proposed SVD-based ICNR technique is that the threshold value for interference cancellation needs to be manually selected. Finally, the inversion waveform of the applied alternating magnetic field was given by fitting the processed experimental data. PMID:26959024

  6. A multichannel nonlinear adaptive noise canceller based on generalized FLANN for fetal ECG extraction

    NASA Astrophysics Data System (ADS)

    Ma, Yaping; Xiao, Yegui; Wei, Guo; Sun, Jinwei

    2016-01-01

    In this paper, a multichannel nonlinear adaptive noise canceller (ANC) based on the generalized functional link artificial neural network (FLANN, GFLANN) is proposed for fetal electrocardiogram (FECG) extraction. A FIR filter and a GFLANN are equipped in parallel in each reference channel to respectively approximate the linearity and nonlinearity between the maternal ECG (MECG) and the composite abdominal ECG (AECG). A fast scheme is also introduced to reduce the computational cost of the FLANN and the GFLANN. Two (2) sets of ECG time sequences, one synthetic and one real, are utilized to demonstrate the improved effectiveness of the proposed nonlinear ANC. The real dataset is derived from the Physionet non-invasive FECG database (PNIFECGDB) including 55 multichannel recordings taken from a pregnant woman. It contains two subdatasets that consist of 14 and 8 recordings, respectively, with each recording being 90 s long. Simulation results based on these two datasets reveal, on the whole, that the proposed ANC does enjoy higher capability to deal with nonlinearity between MECG and AECG as compared with previous ANCs in terms of fetal QRS (FQRS)-related statistics and morphology of the extracted FECG waveforms. In particular, for the second real subdataset, the F1-measure results produced by the PCA-based template subtraction (TSpca) technique and six (6) single-reference channel ANCs using LMS- and RLS-based FIR filters, Volterra filter, FLANN, GFLANN, and adaptive echo state neural network (ESN a ) are 92.47%, 93.70%, 94.07%, 94.22%, 94.90%, 94.90%, and 95.46%, respectively. The same F1-measure statistical results from five (5) multi-reference channel ANCs (LMS- and RLS-based FIR filters, Volterra filter, FLANN, and GFLANN) for the second real subdataset turn out to be 94.08%, 94.29%, 94.68%, 94.91%, and 94.96%, respectively. These results indicate that the ESN a and GFLANN perform best, with the ESN a being slightly better than the GFLANN but about four times more

  7. Magnetic flux cancellation and Doppler shifts in flaring active regions

    NASA Astrophysics Data System (ADS)

    Burtseva, Olga; Petrie, Gordon

    2016-05-01

    Flux cancellation plays an important role in some theories of solar eruptions. The mechanism of flux cancellation is suggested by many models to be a necessary condition of flare initiation as a part of slow reconnection processes in the lower atmosphere. In our earlier work we analyzed flux cancellation events during major flares using GONG line-of-sight magnetograms. In this work we use vector magnetic field data from SDO/HMI for better interpretation of the longitudinal field changes. We also compute Doppler velocity shifts at the cancellation sites in attempt to distinguish between the three physical processes that could stand behind flux removal from the photosphere: submergence of U-shaped loops, emergence of Ω-shaped loops and magnetic reconnection.

  8. An efficient feedback active noise control algorithm based on reduced-order linear predictive modeling of FMRI acoustic noise.

    PubMed

    Kannan, Govind; Milani, Ali A; Panahi, Issa M S; Briggs, Richard W

    2011-12-01

    Functional magnetic resonance imaging (fMRI) acoustic noise exhibits an almost periodic nature (quasi-periodicity) due to the repetitive nature of currents in the gradient coils. Small changes occur in the waveform in consecutive periods due to the background noise and slow drifts in the electroacoustic transfer functions that map the gradient coil waveforms to the measured acoustic waveforms. The period depends on the number of slices per second, when echo planar imaging (EPI) sequencing is used. Linear predictability of fMRI acoustic noise has a direct effect on the performance of active noise control (ANC) systems targeted to cancel the acoustic noise. It is shown that by incorporating some samples from the previous period, very high linear prediction accuracy can be reached with a very low order predictor. This has direct implications on feedback ANC systems since their performance is governed by the predictability of the acoustic noise to be cancelled. The low complexity linear prediction of fMRI acoustic noise developed in this paper is used to derive an effective and low-cost feedback ANC system.

  9. 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.

  10. Active Cancellation of Acoustical Resonances with an FPGA FIR Filter

    NASA Astrophysics Data System (ADS)

    Ryou, Albert; Simon, Jonathan

    2016-05-01

    We demonstrate a novel approach to enhancing the closed-loop bandwidth of a feedback-controlled mechanical system by digitally cancelling its acoustical resonances and antiresonances with an FPGA FIR filter. By performing a real-time convolution of the feedback error signal with an arbitrary filter, we can suppress arbitrarily many poles and zeros below 100 kHz, each with a linewidth as small as 10 Hz. We demonstrate the efficacy of this technique by cancelling the six largest resonances and antiresonances of a high-finesse optical resonator piezomechanical transfer function, thereby enhancing the unity gain frequency by more than an order of magnitude. More broadly, this approach is applicable to stabilization of optical resonators, external cavity diode lasers, and scanning tunneling microscopes.

  11. Channel capacity of an array system for Gaussian channels with applications to combining and noise cancellation

    NASA Technical Reports Server (NTRS)

    Cheung, K. M.; Vilnrotter, V.

    1996-01-01

    A closed-form expression for the capacity of an array of correlated Gaussian channels is derived. It is shown that when signal and noise are independent, the array of observables can be replaced with a single observable without diminishing the capacity of the array channel. Examples are provided to illustrate the dependence of channel capacity on noise correlation for two- and three-channel arrays.

  12. First Test of Fan Active Noise Control (ANC) Completed

    NASA Technical Reports Server (NTRS)

    2005-01-01

    With the advent of ultrahigh-bypass engines, the space available for passive acoustic treatment is becoming more limited, whereas noise regulations are becoming more stringent. Active noise control (ANC) holds promise as a solution to this problem. It uses secondary (added) noise sources to reduce or eliminate the offending noise radiation. The first active noise control test on the low-speed fan test bed was a General Electric Company system designed to control either the exhaust or inlet fan tone. This system consists of a "ring source," an induct array of error microphones, and a control computer. Fan tone noise propagates in a duct in the form of spinning waves. These waves are detected by the microphone array, and the computer identifies their spinning structure. The computer then controls the "ring source" to generate waves that have the same spinning structure and amplitude, but 180 out of phase with the fan noise. This computer generated tone cancels the fan tone before it radiates from the duct and is heard in the far field. The "ring source" used in these tests is a cylindrical array of 16 flat-plate acoustic radiators that are driven by thin piezoceramic sheets bonded to their back surfaces. The resulting source can produce spinning waves up to mode 7 at levels high enough to cancel the fan tone. The control software is flexible enough to work on spinning mode orders from -6 to 6. In this test, the fan was configured to produce a tone of order 6. The complete modal (spinning and radial) structure of the tones was measured with two builtin sets of rotating microphone rakes. These rakes provide a measurement of the system performance independent from the control system error microphones. In addition, the far-field noise was measured with a semicircular array of 28 microphones. This test represents the first in a series of tests that demonstrate different active noise control concepts, each on a progressively more complicated modal structure. The tests are

  13. Background noise cancellation of manatee vocalizations using an adaptive line enhancer.

    PubMed

    Yan, Zheng; Niezrecki, Christopher; Cattafesta, Louis N; Beusse, Diedrich O

    2006-07-01

    The West Indian manatee (Trichechus manatus latirostris) has become an endangered species partly because of an increase in the number of collisions with boats. A device to alert boaters of the presence of manatees is desired. Previous research has shown that background noise limits the manatee vocalization detection range (which is critical for practical implementation). By improving the signal-to-noise ratio of the measured manatee vocalization signal, it is possible to extend the detection range. The finite impulse response (FIR) structure of the adaptive line enhancer (ALE) can detect and track narrow-band signals buried in broadband noise. In this paper, a constrained infinite impulse response (IIR) ALE, called a feedback ALE (FALE), is implemented to reduce the background noise. In addition, a bandpass filter is used as a baseline for comparison. A library consisting of 100 manatee calls spanning ten different signal categories is used to evaluate the performance of the bandpass filter, FIR-ALE, and FALE. The results show that the FALE is capable of reducing background noise by about 6.0 and 21.4 dB better than that of the FIR-ALE and bandpass filter, respectively, when the signal-to-noise ratio (SNR) of the original manatee call is -5 dB. PMID:16875212

  14. Common mode noise cancellation for electrically non-contact ECG measurement system on a chair.

    PubMed

    Keun Kim, Ko; Kyu Lim, Yong; Suk Park, Kwang

    2005-01-01

    Electrically non-contact ECG measurement system on a chair can be applied to a number of various fields for continuous health monitoring in daily life. However, the body is floated electrically for this system due to the capacitive electrodes and the floated body is very sensitive to the external noises or motion artifacts which affect the measurement system as the common mode noise. In this paper, the Driven-Seat-Ground circuit similar to the Driven-Right-Leg circuit is proposed to reduce the common mode noise. The analysis of this equivalent circuit is performed and the output signal waveforms are compared between with Driven-Seat-Ground and with capacitive ground. As the results, the Driven-Seat-Ground circuit improves significantly the properties of the fully capacitive ECG measurement system as the negative feedback.

  15. Wireless rake-receiver using adaptive filter with a family of partial update algorithms in noise cancellation applications

    NASA Astrophysics Data System (ADS)

    Fayadh, Rashid A.; Malek, F.; Fadhil, Hilal A.; Aldhaibani, Jaafar A.; Salman, M. K.; Abdullah, Farah Salwani

    2015-05-01

    For high data rate propagation in wireless ultra-wideband (UWB) communication systems, the inter-symbol interference (ISI), multiple-access interference (MAI), and multiple-users interference (MUI) are influencing the performance of the wireless systems. In this paper, the rake-receiver was presented with the spread signal by direct sequence spread spectrum (DS-SS) technique. The adaptive rake-receiver structure was shown with adjusting the receiver tap weights using least mean squares (LMS), normalized least mean squares (NLMS), and affine projection algorithms (APA) to support the weak signals by noise cancellation and mitigate the interferences. To minimize the data convergence speed and to reduce the computational complexity by the previous algorithms, a well-known approach of partial-updates (PU) adaptive filters were employed with algorithms, such as sequential-partial, periodic-partial, M-max-partial, and selective-partial updates (SPU) in the proposed system. The simulation results of bit error rate (BER) versus signal-to-noise ratio (SNR) are illustrated to show the performance of partial-update algorithms that have nearly comparable performance with the full update adaptive filters. Furthermore, the SPU-partial has closed performance to the full-NLMS and full-APA while the M-max-partial has closed performance to the full-LMS updates algorithms.

  16. Active Noise Control of Low Speed Fan Rotor-Stator Modes

    NASA Technical Reports Server (NTRS)

    Sutliff, Daniel L.; Hu, Ziqiang; Pla, Frederic G.; Heidelberg, Laurence J.

    1996-01-01

    This report describes the Active Noise Cancellation System designed by General Electric and tested in the NASA Lewis Research Center's 48 inch Active Noise Control Fan. The goal of this study was to assess the feasibility of using wall mounted secondary acoustic sources and sensors within the duct of a high bypass turbofan aircraft engine for active noise cancellation of fan tones. The control system is based on a modal control approach. A known acoustic mode propagating in the fan duct is cancelled using an array of flush-mounted compact sound sources. Controller inputs are signals from a shaft encoder and a microphone array which senses the residual acoustic mode in the duct. The canceling modal signal is generated by a modal controller. The key results are that the (6,0) mode was completely eliminated at 920 Hz and substantially reduced elsewhere. The total tone power was reduced 9.4 dB. Farfield 2BPF SPL reductions of 13 dB were obtained. The (4,0) and (4,1) modes were reduced simultaneously yielding a 15 dB modal PWL decrease. Global attenuation of PWL was obtained using an actuator and sensor system totally contained within the duct.

  17. Active Shielding and Control of Environmental Noise

    NASA Technical Reports Server (NTRS)

    Tsynkov, S. V.

    2001-01-01

    In the framework of the research project supported by NASA under grant # NAG-1-01064, we have studied the mathematical aspects of the problem of active control of sound, i.e., time-harmonic acoustic disturbances. The foundations of the methodology are described in our paper [1]. Unlike. many other existing techniques, the approach of [1] provides for the exact volumetric cancellation of the unwanted noise on a given predetermined region airspace, while leaving unaltered those components of the total acoustic field that are deemed as friendly. The key finding of the work is that for eliminating the unwanted component of the acoustic field in a given area, one needs to know relatively little; in particular, neither the locations nor structure nor strength of the exterior noise sources need to be known. Likewise, there is no need to know the volumetric properties of the supporting medium across which the acoustic signals propagate, except, maybe, in a narrow area of space near the perimeter of the protected region. The controls are built based solely on the measurements performed on the perimeter of the domain to be shielded; moreover, the controls themselves (i.e., additional sources) are concentrated also only on or near this perimeter. Perhaps as important, the measured quantities can refer to the total acoustic field rather than to its unwanted component only, and the methodology can automatically distinguish between the two. In [1], we have constructed the general solution for controls. The apparatus used for deriving this general solution is closely connected to the concepts of generalized potentials and boundary projections of Calderon's type. For a given total wave field, the application of a Calderon's projection allows one to definitively tell between its incoming and outgoing components with respect to a particular domain of interest, which may have arbitrary shape. Then, the controls are designed so that they suppress the incoming component for the domain

  18. Active noise control using a distributed mode flat panel loudspeaker.

    PubMed

    Zhu, H; Rajamani, R; Dudney, J; Stelson, K A

    2003-07-01

    A flat panel distributed mode loudspeaker (DML) has many advantages over traditional cone speakers in terms of its weight, size, and durability. However, its frequency response is uneven and complex, thus bringing its suitability for active noise control (ANC) under question. This paper presents experimental results demonstrating the effective use of panel DML speakers in an ANC application. Both feedback and feedforward control techniques are considered. Effective feedback control with a flat panel speaker could open up a whole range of new noise control applications and has many advantages over feedforward control. The paper develops a new control algorithm to attenuate tonal noise of a known frequency by feedback control. However, due to the uneven response of the speakers, feedback control is found to be only moderately effective even for this narrow-band application. Feedforward control proves to be most capable for the flat panel speaker. Using feedforward control, the sound pressure level can be significantly reduced in close proximity to an error microphone. The paper demonstrates an interesting application of the flat panel in which the panel is placed in the path of sound and effectively used to block sound transmission using feedforward control. This is a new approach to active noise control enabled by the use of flat panels and can be used to prevent sound from entering into an enclosure in the first place rather than the traditional approach of attempting to cancel sound after it enters the enclosure.

  19. 30 CFR 251.9 - Temporarily stopping, canceling, or relinquishing activities approved under a permit.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... relinquishing activities approved under a permit. 251.9 Section 251.9 Mineral Resources BUREAU OF OCEAN ENERGY...) EXPLORATIONS OF THE OUTER CONTINENTAL SHELF § 251.9 Temporarily stopping, canceling, or relinquishing activities approved under a permit. (a) MMS may temporarily stop exploration or scientific...

  20. 30 CFR 251.9 - Temporarily stopping, canceling, or relinquishing activities approved under a permit.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Temporarily stopping, canceling, or relinquishing activities approved under a permit. 251.9 Section 251.9 Mineral Resources MINERALS MANAGEMENT.... (a) MMS may temporarily stop exploration or scientific research activities under a permit when...

  1. Adaptive singular value cancelation of ventricular activity in single-lead atrial fibrillation electrocardiograms.

    PubMed

    Alcaraz, Raúl; Rieta, José Joaquín

    2008-12-01

    The proper analysis and characterization of atrial fibrillation (AF) from surface electrocardiographic (ECG) recordings requires to cancel out the ventricular activity (VA), which is composed of the QRS complex and the T wave. Historically, for single-lead ECGs, the averaged beat subtraction (ABS) has been the most widely used technique. However, this method is very sensitive to QRST wave variations and, moreover, high-quality cancelation templates may be difficult to obtain when only short length and single-lead recordings are available. In order to overcome these limitations, a new QRST cancelation method based on adaptive singular value cancelation (ASVC) applied to each single beat is proposed. In addition, an exhaustive study about the optimal set of complexes for better cancelation of every beat is also presented for the first time. The whole study has been carried out with both simulated and real AF signals. For simulated AF, the cancelation performance was evaluated making use of a cross-correlation index and the normalized mean square error (nmse) between the estimated and the original atrial activity (AA). For real AF signals, two additional new parameters were proposed. First, the ventricular residue (VR) index estimated the presence of ventricular activity in the extracted AA. Second, the similarity (S) evaluated how the algorithm preserved the AA segments out of the QRST interval. Results indicated that for simulated AF signals, mean correlation, nmse, VR and S values were 0.945 +/- 0.024, 0.332 +/- 0.073, 1.552 +/- 0.386 and 0.986 +/- 0.012, respectively, for the ASVC method and 0.866 +/- 0.042, 0.424 +/- 0.120, 2.161 +/- 0.564 and 0.922 +/- 0.051 for ABS. In the case of real signals, the mean VR and S values were 1.725 +/- 0.826 and 0.983 +/- 0.038, respectively, for ASVC and 3.159 +/- 1.097 and 0.951 +/- 0.049 for ABS. Thus, ASVC provides a more accurate beat-to-beat ventricular QRST representation than traditional techniques. As a consequence, VA

  2. Qubit quantum-dot sensors: Noise cancellation by coherent backaction, initial slips, and elliptical precession

    NASA Astrophysics Data System (ADS)

    Hell, M.; Wegewijs, M. R.; DiVincenzo, D. P.

    2016-01-01

    We theoretically investigate the backaction of a sensor quantum dot with strong local Coulomb repulsion on the transient dynamics of a qubit that is probed capacitively. We show that the measurement backaction induced by the noise of electron cotunneling through the sensor is surprisingly mitigated by the recently identified coherent backaction [M. Hell, M. R. Wegewijs, and D. P. DiVincenzo, Phys. Rev. B 89, 195405 (2014), 10.1103/PhysRevB.89.195405] arising from quantum fluctuations. This indicates that a sensor with quantized states may be switched off better than naively expected. This renormalization effect is missing in semiclassical stochastic fluctuator models and typically also in Born-Markov approaches, which try to avoid the calculation of the nonstationary, nonequilibrium state of the qubit plus sensor. Technically, we integrate out the current-carrying electrodes to obtain kinetic equations for the joint, nonequilibrium detector-qubit dynamics. We show that the sensor current response, level renormalization, cotunneling broadening, and leading non-Markovian corrections always appear together and cannot be turned off individually in an experiment or ignored theoretically. We analyze the backaction on the reduced qubit state—capturing the full non-Markovian effects imposed by the sensor quantum dot on the qubit—by applying a Liouville-space decomposition into quasistationary and rapidly decaying modes. Importantly, the sensor cannot be eliminated completely even in the simplest high-temperature, weak-measurement limit since the qubit state experiences an initial slip depending on the initial preparation of qubit plus sensor quantum dot. The slip persists over many qubit cycles, i.e., also on the time scale of the qubit decoherence induced by the backaction. A quantum-dot sensor can thus not be modeled as usual as a "black box" without accounting for its dynamical variables; it is part of the quantum circuit. We furthermore find that the Bloch vector

  3. Effects of aircraft noise on human activities

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  4. Active Control of Fan Noise-Feasibility Study. Volume 1; Flyover System Noise Studies

    NASA Technical Reports Server (NTRS)

    Kraft, Robert E.; Janardan, B. A.; Kontos, G. C.; Gliebe, P. R.

    1994-01-01

    A study has been completed to examine the potential reduction of aircraft flyover noise by the method of active noise control (ANC). It is assumed that the ANC system will be designed such that it cancels discrete tones radiating from the engine fan inlet or fan exhaust duct. Thus, without considering the engineering details of the ANC system design, tone levels are arbitrarily removed from the engine component noise spectrum and the flyover noise EPNL levels are compared with and without the presence of tones. The study was conducted for a range of engine cycles, corresponding to fan pressure ratios from 1.3 to 1.75. The major conclusions that can be drawn are that, for a fan pressure ratio of 1.75, ANC of tones gives about the same suppression as acoustic treatment without ANC, and for a fan pressure ratio of 1.45, ANC appears to offer less effectiveness than passive treatment. Additionally, ANC appears to be more effective at sideline and cutback conditions than at approach. Overall EPNL suppressions due to tone removal range from about 1 to 3 dB at takeoff engine speeds and from 1 to 5 db at approach speeds. Studies of economic impact of the installation of an ANC system for the four engine cases indicate increases of DOC ranging from 1 to 2 percent, favoring the lower fan pressure ratio engines. Further study is needed to confirm the results by examining additional engine data, particularly at low fan pressure ratios, and studying the details of the current results to obtain a more complete understanding. Further studies should also include determining the effects of combining passive and active treatment.

  5. Active control of fan noise-feasibility study. Volume 1: Flyover system noise studies

    NASA Astrophysics Data System (ADS)

    Kraft, Robert E.; Janardan, B. A.; Kontos, G. C.; Gliebe, P. R.

    1994-10-01

    A study has been completed to examine the potential reduction of aircraft flyover noise by the method of active noise control (ANC). It is assumed that the ANC system will be designed such that it cancels discrete tones radiating from the engine fan inlet or fan exhaust duct. Thus, without considering the engineering details of the ANC system design, tone levels are arbitrarily removed from the engine component noise spectrum and the flyover noise EPNL levels are compared with and without the presence of tones. The study was conducted for a range of engine cycles, corresponding to fan pressure ratios from 1.3 to 1.75. The major conclusions that can be drawn are that, for a fan pressure ratio of 1.75, ANC of tones gives about the same suppression as acoustic treatment without ANC, and for a fan pressure ratio of 1.45, ANC appears to offer less effectiveness than passive treatment. Additionally, ANC appears to be more effective at sideline and cutback conditions than at approach. Overall EPNL suppressions due to tone removal range from about 1 to 3 dB at takeoff engine speeds and from 1 to 5 db at approach speeds. Studies of economic impact of the installation of an ANC system for the four engine cases indicate increases of DOC ranging from 1 to 2 percent, favoring the lower fan pressure ratio engines. Further study is needed to confirm the results by examining additional engine data, particularly at low fan pressure ratios, and studying the details of the current results to obtain a more complete understanding. Further studies should also include determining the effects of combining passive and active treatment.

  6. Source localization for active control of turbofan rotor-stator broadband noise

    NASA Astrophysics Data System (ADS)

    Walker, Bruce E.

    2005-09-01

    In order to identify a reference signal source for an active noise cancellation system, cross-correlation techniques were used to localize broadband noise source regions on exit guide vanes of the NASA Glenn Research Center Advance Noise Control Fan (ANCF). Arrays of surface pressure sensors were imbedded in one guide vane and in the wall of the fan. Synchronous sampling was used with a multichannel data acquisition system to allow removal of periodic components from the signals. The signals were then cross-correlated to assess radiation directivity and the relationship between vane surface pressure and in-duct acoustic noise. The results of these measurements indicated that broadband unsteady pressures near the leading edge tip of the guide vane were well enough correlated with acoustic radiation that 2-3 dB active noise cancellation could be achieved using a simple gain-delay control algorithm and actuator array. After successful simulation in a wind tunnel environment the concept was incorporated on 15 guide vanes and tested in ANCF. Cross-correlation measurements were further used to evaluate system performance and to identify competing noises from rotating and stationary sources within the fan.

  7. Signal-to-noise ratio in neuro activation PET studies

    SciTech Connect

    Votaw, J.R.

    1996-04-01

    It has become commonplace to compare scanner sensitivity characteristics by comparing noise equivalent count rate curves. However, because a 20-cm diameter uniform phantom is drastically difference from a human brain, these curves give misleading information when planning a neuro activation PET experiment. Signal-to-noise ratio (SNR) calculations have been performed using measured data (Siemens 921 scanner) from the three-dimensional (3-D) Hoffman brain phantom for the purpose of determining the optimal injection and scanning protocol for [{sup 15}O] labeled activation experiments. Region of interest (ROI) values along with the variance due to prompt (trues plus randoms) and random events were determined for various regions and radioactivity concentrations. Calculated attenuation correction was used throughout. Scatter correction was not used when calculating the SNR in activation studies because the number of scattered events is almost identical in each data acquisition and hence cancels. The results indicate that randoms correction should not be performed and that rather than being limited by the scanner capabilities, neuro activation experiments are limited by the amount of radioactivity that can be injected and the length of time the patient can stay in the scanner.

  8. Active cancellation of occlusion: an electronic vent for hearing aids and hearing protectors.

    PubMed

    Mejia, Jorge; Dillon, Harvey; Fisher, Michael

    2008-07-01

    The occlusion effect is commonly described as an unnatural and mostly annoying quality of the voice of a person wearing hearing aids or hearing protectors. As a result, it is often reported by hearing aid users as a deterrent to wearing hearing aids. This paper presents an investigation into active occlusion cancellation. Measured transducer responses combined with models of an active feedback scheme are first examined in order to predict the effectiveness of occlusion reduction. The simulations predict 18 dB of occlusion reduction in completely blocked ear canals. Simulations incorporating a 1 mm vent (providing passive occlusion reduction) predict a combined active and passive occlusion reduction of 20 dB. A prototype occlusion canceling system was constructed. Averaged across 12 listeners with normal hearing, it provided 15 dB of occlusion reduction. Ten of the subjects reported a more natural own voice quality and an appreciable increase in comfort with the cancellation active, and 11 out of the 12 preferred the active system over the passive system. PMID:18646971

  9. Active cancellation of occlusion: an electronic vent for hearing aids and hearing protectors.

    PubMed

    Mejia, Jorge; Dillon, Harvey; Fisher, Michael

    2008-07-01

    The occlusion effect is commonly described as an unnatural and mostly annoying quality of the voice of a person wearing hearing aids or hearing protectors. As a result, it is often reported by hearing aid users as a deterrent to wearing hearing aids. This paper presents an investigation into active occlusion cancellation. Measured transducer responses combined with models of an active feedback scheme are first examined in order to predict the effectiveness of occlusion reduction. The simulations predict 18 dB of occlusion reduction in completely blocked ear canals. Simulations incorporating a 1 mm vent (providing passive occlusion reduction) predict a combined active and passive occlusion reduction of 20 dB. A prototype occlusion canceling system was constructed. Averaged across 12 listeners with normal hearing, it provided 15 dB of occlusion reduction. Ten of the subjects reported a more natural own voice quality and an appreciable increase in comfort with the cancellation active, and 11 out of the 12 preferred the active system over the passive system.

  10. Hybrid feedforward-feedback active noise reduction for hearing protection and communication.

    PubMed

    Ray, Laura R; Solbeck, Jason A; Streeter, Alexander D; Collier, Robert D

    2006-10-01

    A hybrid active noise reduction (ANR) architecture is presented and validated for a circumaural earcup and a communication earplug. The hybrid system combines source-independent feedback ANR with a Lyapunov-tuned leaky LMS filter (LyLMS) improving gain stability margins over feedforward ANR alone. In flat plate testing, the earcup demonstrates an overall C-weighted total noise reduction of 40 dB and 30-32 dB, respectively, for 50-800 Hz sum-of-tones noise and for aircraft or helicopter cockpit noise, improving low frequency (<100 Hz) performance by up to 15 dB over either control component acting individually. For the earplug, a filtered-X implementation of the LyLMS accommodates its nonconstant cancellation path gain. A fast time-domain identification method provides a high-fidelity, computationally efficient, infinite impulse response cancellation path model, which is used for both the filtered-X implementation and communication feedthrough. Insertion loss measurements made with a manikin show overall C-weighted total noise reduction provided by the ANR earplug of 46-48 dB for sum-of-tones 80-2000 Hz and 40-41 dB from 63 to 3000 Hz for UH-60 helicopter noise, with negligible degradation in attenuation during speech communication. For both hearing protectors, a stability metric improves by a factor of 2 to several orders of magnitude through hybrid ANR. PMID:17069300

  11. Experimental evaluation of leaky least-mean-square algorithms for active noise reduction in communication headsets

    NASA Astrophysics Data System (ADS)

    Cartes, David A.; Ray, Laura R.; Collier, Robert D.

    2002-04-01

    An adaptive leaky normalized least-mean-square (NLMS) algorithm has been developed to optimize stability and performance of active noise cancellation systems. The research addresses LMS filter performance issues related to insufficient excitation, nonstationary noise fields, and time-varying signal-to-noise ratio. The adaptive leaky NLMS algorithm is based on a Lyapunov tuning approach in which three candidate algorithms, each of which is a function of the instantaneous measured reference input, measurement noise variance, and filter length, are shown to provide varying degrees of tradeoff between stability and noise reduction performance. Each algorithm is evaluated experimentally for reduction of low frequency noise in communication headsets, and stability and noise reduction performance are compared with that of traditional NLMS and fixed-leakage NLMS algorithms. Acoustic measurements are made in a specially designed acoustic test cell which is based on the original work of Ryan et al. [``Enclosure for low frequency assessment of active noise reducing circumaural headsets and hearing protection,'' Can. Acoust. 21, 19-20 (1993)] and which provides a highly controlled and uniform acoustic environment. The stability and performance of the active noise reduction system, including a prototype communication headset, are investigated for a variety of noise sources ranging from stationary tonal noise to highly nonstationary measured F-16 aircraft noise over a 20 dB dynamic range. Results demonstrate significant improvements in stability of Lyapunov-tuned LMS algorithms over traditional leaky or nonleaky normalized algorithms, while providing noise reduction performance equivalent to that of the NLMS algorithm for idealized noise fields.

  12. Influence of Amplitude Cancellation on the Accuracy of Determining the Onset of Muscle Activity from the Surface Electromyogram

    PubMed Central

    Jesunathadas, Mark; Aidoor, Sameer S.; Keenan, Kevin G.; Farina, Dario; Enoka, Roger M.

    2012-01-01

    The purpose of the study was to quantify the influence of amplitude cancellation on the accuracy of detecting the onset of muscle activity based on an analysis of simulated surface electromyographic (EMG) signals. EMG activity of a generic lower limb muscle was simulated during the stance phase of human gait. Surface EMG signals were generated with and without amplitude cancellation by summing simulated motor unit potentials either before (cancellation EMG) or after (no-cancellation EMG) the potentials had been rectified. The two sets of EMG signals were compared at forces of 30 and 80% of maximum voluntary contraction (MVC) and with various low-pass filter cut-off frequencies. Onset time was determined both visually and by an algorithm that identified when the mean amplitude of the signal within a sliding window exceeded a specified standard deviation (SD) above the baseline mean. Onset error was greater for the no-cancellation conditions when determined automatically and by visual inspection. However, the differences in onset error between the two cancellation conditions appear to be clinically insignificant. Therefore, amplitude cancellation does not appear to limit the ability to detect the onset of muscle activity from the surface EMG. PMID:22330887

  13. Active cancellation - A means to zero dead-time pulse EPR.

    PubMed

    Franck, John M; Barnes, Ryan P; Keller, Timothy J; Kaufmann, Thomas; Han, Songi

    2015-12-01

    The necessary resonator employed in pulse electron paramagnetic resonance (EPR) rings after the excitation pulse and creates a finite detector dead-time that ultimately prevents the detection of signal from fast relaxing spin systems, hindering the application of pulse EPR to room temperature measurements of interesting chemical or biological systems. We employ a recently available high bandwidth arbitrary waveform generator (AWG) to produce a cancellation pulse that precisely destructively interferes with the resonant cavity ring-down. We find that we can faithfully detect EPR signal at all times immediately after, as well as during, the excitation pulse. This is a proof of concept study showcasing the capability of AWG pulses to precisely cancel out the resonator ring-down, and allow for the detection of EPR signal during the pulse itself, as well as the dead-time of the resonator. However, the applicability of this approach to conventional EPR experiments is not immediate, as it hinges on either (1) the availability of low-noise microwave sources and amplifiers to produce the necessary power for pulse EPR experiment or (2) the availability of very high conversion factor micro coil resonators that allow for pulse EPR experiments at modest microwave power. PMID:26507308

  14. Active cancellation - A means to zero dead-time pulse EPR

    NASA Astrophysics Data System (ADS)

    Franck, John M.; Barnes, Ryan P.; Keller, Timothy J.; Kaufmann, Thomas; Han, Songi

    2015-12-01

    The necessary resonator employed in pulse electron paramagnetic resonance (EPR) rings after the excitation pulse and creates a finite detector dead-time that ultimately prevents the detection of signal from fast relaxing spin systems, hindering the application of pulse EPR to room temperature measurements of interesting chemical or biological systems. We employ a recently available high bandwidth arbitrary waveform generator (AWG) to produce a cancellation pulse that precisely destructively interferes with the resonant cavity ring-down. We find that we can faithfully detect EPR signal at all times immediately after, as well as during, the excitation pulse. This is a proof of concept study showcasing the capability of AWG pulses to precisely cancel out the resonator ring-down, and allow for the detection of EPR signal during the pulse itself, as well as the dead-time of the resonator. However, the applicability of this approach to conventional EPR experiments is not immediate, as it hinges on either (1) the availability of low-noise microwave sources and amplifiers to produce the necessary power for pulse EPR experiment or (2) the availability of very high conversion factor micro coil resonators that allow for pulse EPR experiments at modest microwave power.

  15. Evaluating the effectiveness of active noise reduction in flight helmets

    NASA Astrophysics Data System (ADS)

    Forshaw, S. E.; Rylands, J. M.; Crabtree, R. B.

    1988-08-01

    The advent of high powered fixed- and rotary-wing aircraft and tracked armoured fighting vehicles has increased the level of noise to which crews are exposed. Active noise reduction (ANR) offers a means of increasing the attenuation at low and mid frequencies. It relies on sensing the sound inside a circumaural device and cancelling it by means of negative feedback through a miniature speaker inside the enclosed volume. This study was carried out to investigate laboratory procedures appropriate for measuring the effectiveness of ANR devices. The procedures were: ear-canal measurements using an acoustic test fixture (an objective procedure), and masked threshold and loudness balance tests (psycho-physical procedures). In addition, the effect of ANR on signal detection and speech reception was investigated. The results do not clearly permit one procedure to be recommended for the evaluation of ANR systems. Signal detection performance and speech intelligibility may be used, but the results are specific to the acoustic environment of the listener and the detection task or speech-system parameters of the evaluation. When the attenuation of the ANR system is measured objectively with a transducer inside the earmuff/ear-canal volume, the location of the transducer affects the observed ANR attenuations.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  17. Active cancellation of residual amplitude modulation in a frequency-modulation based Fabry-Perot interferometer.

    PubMed

    Yu, Yinan; Wang, Yicheng; Pratt, Jon R

    2016-03-01

    Residual amplitude modulation (RAM) is one of the most common noise sources known to degrade the sensitivity of frequency modulation spectroscopy. RAM can arise as a result of the temperature dependent birefringence of the modulator crystal, which causes the orientation of the crystal's optical axis to shift with respect to the polarization of the incident light with temperature. In the fiber-based optical interferometer used on the National Institute of Standards and Technology calculable capacitor, RAM degrades the measured laser frequency stability and correlates with the environmental temperature fluctuations. We have demonstrated a simple approach that cancels out excessive RAM due to polarization mismatch between the light and the optical axis of the crystal. The approach allows us to measure the frequency noise of a heterodyne beat between two lasers individually locked to different resonant modes of a cavity with an accuracy better than 0.5 ppm, which meets the requirement to further determine the longitudinal mode number of the cavity length. Also, this approach has substantially mitigated the temperature dependency of the measurements of the cavity length and consequently the capacitance. PMID:27036752

  18. Active cancellation of residual amplitude modulation in a frequency-modulation based Fabry-Perot interferometer

    NASA Astrophysics Data System (ADS)

    Yu, Yinan; Wang, Yicheng; Pratt, Jon R.

    2016-03-01

    Residual amplitude modulation (RAM) is one of the most common noise sources known to degrade the sensitivity of frequency modulation spectroscopy. RAM can arise as a result of the temperature dependent birefringence of the modulator crystal, which causes the orientation of the crystal's optical axis to shift with respect to the polarization of the incident light with temperature. In the fiber-based optical interferometer used on the National Institute of Standards and Technology calculable capacitor, RAM degrades the measured laser frequency stability and correlates with the environmental temperature fluctuations. We have demonstrated a simple approach that cancels out excessive RAM due to polarization mismatch between the light and the optical axis of the crystal. The approach allows us to measure the frequency noise of a heterodyne beat between two lasers individually locked to different resonant modes of a cavity with an accuracy better than 0.5 ppm, which meets the requirement to further determine the longitudinal mode number of the cavity length. Also, this approach has substantially mitigated the temperature dependency of the measurements of the cavity length and consequently the capacitance.

  19. Bucking Coil Implementation on PMT for Active Cancelling of Magnetic Field

    SciTech Connect

    Gogami, T; Asaturyan, A; Bono, J; Baturin, P; Chen, C; Chiba, A; Chiga, N; Fujii, Y; Hashimoto, O; Kawama, D; Maruta, T; Maxwell, V; Mkrtchyan, A; Nagao, S; Nakamura, S N; Reinhold, J; Shichijo, A; Tang, L; Taniya, N; Wood, S A; Ye, Z

    2013-11-01

    Aerogel and water Cerenkov detectors were employed to tag kaons for a lambda hypernuclear spectroscopic experiment which used the (e,e'K{sup +}) reaction in experimental Hall C at Jefferson Lab (JLab E05-115). Fringe fields from the kaon spectrometer magnet yielded ~5 Gauss at the photomultiplier tubes (PMT) for these detectors which could not be easily shielded. As this field results in a lowered kaon detection efficiency, we implemented a bucking coil on each photomultiplier tubes to actively cancel this magnetic field, thus maximizing kaon detection efficiency.

  20. Filament Activation in Response to Magnetic Flux Emergence and Cancellation in Filament Channels

    NASA Astrophysics Data System (ADS)

    Li, Ting; Zhang, Jun; Ji, Haisheng

    2015-06-01

    We conducted a comparative analysis of two filaments that showed a quite different activation in response to the flux emergence within the filament channels. The observations from the Solar Dynamics Observatory (SDO) and Global Oscillation Network Group (GONG) were made to analyze the two filaments on 2013 August 17 - 20 (SOL2013-08-17) and September 29 (SOL2013-09-29). The first event showed that the main body of the filament was separated into two parts when an active region (AR) emerged with a maximum magnetic flux of about 6.4×1021 Mx underlying the filament. The close neighborhood and common direction of the bright threads in the filament and the open AR fan loops suggest a similar magnetic connectivity of these two flux systems. The equilibrium of the filament was not destroyed three days after the start of the emergence of the AR. To our knowledge, similar observations have never been reported before. In the second event, the emerging flux occurred nearby a barb of the filament with a maximum magnetic flux of 4.2×1020 Mx, about one order of magnitude lower than that of the first event. Two patches of parasitic polarity in the vicinity of the barb merged, then cancelled with nearby network fields. About 20 hours after the onset of the emergence, the filament erupted. Our findings imply that the location of emerging flux within the filament channel is probably crucial to filament evolution. If the flux emergence appears nearby the barbs, it is highly likely that the emerging flux and the filament magnetic fields will cancel, which may lead to the eruption of the filament. The comparison of the two events shows that the emergence of a small AR may still not be enough to disrupt the stability of a filament system, and the actual eruption only occurs after the flux cancellation sets in.

  1. Active Attenuation of Acoustic Noise Using Adaptive Armax Control.

    NASA Astrophysics Data System (ADS)

    Swanson, David Carl

    An adaptive auxiliary input autoregressive moving average (ARMAX) control system using the recursive least -squares lattice for system identification is developed for active control of dynamic systems. The closed-loop adaptive ARMAX control system is applied to active acoustic noise reduction in three-dimensional spaces. The structure of the ARMAX system is compared to that for duct cancellation systems, model-reference control systems, and the general field solution and is seen as a reasonable approach for active field control in the general case. The ARMAX system is derived for multiple inputs and outputs where the measured outputs are to be driven to desired waveforms with least -squares error using a multi-channel ARMAX lattice for recursive system identification. A significant reduction in complexity is obtained by neglecting the ARMAX zeros for the special case of active attenuation of non-dispersive acoustic waves. It is shown that using the least-squares lattice requires fewer multiplies, divides, additions, and subtractions than the recursive least-squares algorithm which is based on the matrix inversion lemma. Computational complexity is seen as an important issue in the application of adaptive ARMAX systems to active field control because the system must control relatively higher numbers of modes and frequencies in real time than are seen in industrial process plants for which the adaptive ARMAX systems were first developed using recursive least squares. Convergence requirements using the lattice system identification algorithm are the same as that for the recursive least squares algorithm in adaptive ARMAX system and are verified in numerical simulations using known ARMAX parameters. A real-time simulation of active attenuation of acoustic noise is presented using the blade-excited harmonics from a small axial flow fan. The adaptive ARMAX controller provides active attenuation for correlated spectral peaks but not for uncorrelated noise from turbulence

  2. Active Control of Noise Using Actuator/Sensor Arrays

    NASA Technical Reports Server (NTRS)

    Lindner, Douglas K.; Winder, Patrice; Kirby, George

    1996-01-01

    Current research in smart structures is directed toward the integration of many actuators and sensors into a material. In this paper we investigate the possibility of using this instrumentation for active noise control from a vibrating structures. Current technology for reducing radiated sound is limited by the instrumentation for the control system. These control systems employ relatively small numbers of sensors and actuators. Hence, these control systems must rely on a model of the structure to estimate and control the global vibrations that contribute to the far field pressure. For complex, realistic structures the development of such a model is a formidable task. The model is a limiting factor in the continuing development of structural acoustics. In this paper we propose to increase the number of actuators and sensors of a smart material to offset the complexity of the model used for control design. The sensor arrays will be used to directly sense the shape of the structure rather than using a model of the structures to indirectly sense the shape of the structure. The actuator array is used to apply distributed forces to the structure, rather than using the structure itself as a load path. A control system for the active cancellation of sound is derived from standard control system methodologies.

  3. A multi-band spectral subtraction-based algorithm for real-time noise cancellation applied to gunshot acoustics

    NASA Astrophysics Data System (ADS)

    Ramos, António L. L.; Holm, Sverre; Gudvangen, Sigmund; Otterlei, Ragnvald

    2013-06-01

    Acoustical sniper positioning is based on the detection and direction-of-arrival estimation of the shockwave and the muzzle blast acoustical signals. In real-life situations, the detection and direction-of-arrival estimation processes is usually performed under the influence of background noise sources, e.g., vehicles noise, and might result in non-negligible inaccuracies than can affect the system performance and reliability negatively, specially when detecting the muzzle sound under long range distance and absorbing terrains. This paper introduces a multi-band spectral subtraction based algorithm for real-time noise reduction, applied to gunshot acoustical signals. The ballistic shockwave and the muzzle blast signals exhibit distinct frequency contents that are affected differently by additive noise. In most real situations, the noise component is colored and a multi-band spectral subtraction approach for noise reduction contributes to reducing the presence of artifacts in denoised signals. The proposed algorithm is tested using a dataset generated by combining signals from real gunshots and real vehicle noise. The noise component was generated using a steel tracked military tank running on asphalt and includes, therefore, the sound from the vehicle engine, which varies slightly in frequency over time according to the engine's rpm, and the sound from the steel tracks as the vehicle moves.

  4. 48 CFR 52.203-8 - Cancellation, Rescission, and Recovery of Funds for Illegal or Improper Activity.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ..., and Recovery of Funds for Illegal or Improper Activity. 52.203-8 Section 52.203-8 Federal Acquisition... for Illegal or Improper Activity. As prescribed in 3.104-9(a), insert the following clause: Cancellation, Rescission, and Recovery of Funds for Illegal or Improper Activity (JAN 1997) (a) If...

  5. 48 CFR 52.203-8 - Cancellation, Rescission, and Recovery of Funds for Illegal or Improper Activity.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ..., and Recovery of Funds for Illegal or Improper Activity. 52.203-8 Section 52.203-8 Federal Acquisition... for Illegal or Improper Activity. As prescribed in 3.104-9(a), insert the following clause: Cancellation, Rescission, and Recovery of Funds for Illegal or Improper Activity (MAY 2014) (a) If...

  6. 48 CFR 52.203-8 - Cancellation, Rescission, and Recovery of Funds for Illegal or Improper Activity.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ..., and Recovery of Funds for Illegal or Improper Activity. 52.203-8 Section 52.203-8 Federal Acquisition... for Illegal or Improper Activity. As prescribed in 3.104-9(a), insert the following clause: Cancellation, Rescission, and Recovery of Funds for Illegal or Improper Activity (JAN 1997) (a) If...

  7. 48 CFR 52.203-8 - Cancellation, Rescission, and Recovery of Funds for Illegal or Improper Activity.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ..., and Recovery of Funds for Illegal or Improper Activity. 52.203-8 Section 52.203-8 Federal Acquisition... for Illegal or Improper Activity. As prescribed in 3.104-9(a), insert the following clause: Cancellation, Rescission, and Recovery of Funds for Illegal or Improper Activity (JAN 1997) (a) If...

  8. Differential-mode vibrational noise cancellation structure for Metglas/Pb(Zr,Ti)O₃ fiber magnetoelectric laminates.

    PubMed

    Gao, Junqi; Zhai, Junyi; Shen, Ying; Shen, Liangguo; Gray, David; Li, Jiefang; Finkel, Peter; Viehland, D

    2011-08-01

    A differential structure which has the ability to reject external vibrational noise for Metglas/Pb(Zr,Ti)O(3) (PZT) fiber-based magnetoelectric (ME) heterostructures has been studied. This type of ME structure functions better than conventional sensors as a magnetic sensor when used in an environment in which vibrational isolation is impractical. Sensors fabricated with this differential mode structure can attenuate external vibrational noise by about 10 to 20 dB at different frequencies, while simultaneously having a doubled ME voltage coefficient. Interestingly, in addition to offering a means of mitigating vibrational noise, this ME structure offers the potential to be a hybrid sensor, separating magnetic and acoustical signals.

  9. Active Control of Fan Noise: Feasibility Study. Volume 4; Flyover System Noise Studies

    NASA Technical Reports Server (NTRS)

    Kraft, R. E.; Janardan, B. A.; Gliebe, P. R.; Kontos, G. C.

    1996-01-01

    An extension of a prior study has been completed to examine the potential reduction of aircraft flyover noise by the method of active noise control (ANC). It is assumed that the ANC system will be designed such that it cancels discrete tones radiating from the engine fan inlet or fan exhaust duct, at least to the extent that they no longer protrude above the surrounding broadband noise levels. Thus, without considering the engineering details of the ANC system design, tone levels am arbitrarily removed from the engine component noise spectrum and the flyover noise EPNL levels are compared with and without the presence of tones. The study was conducted for a range of engine cycles, corresponding to fan pressure ratios of 1.3, 1.45, 1.6, and 1.75. This report is an extension of an effort reported previously. The major conclusions drawn from the prior study, which was restricted to fan pressure ratios of 1.45 and 1.75, are that, for a fan pressure ratio of 1.75, ANC of tones gives about the same suppression as acoustic treatment without ANC. For a fan pressure ratio of 1.45, ANC appears to offer less effectiveness from passive treatment. In the present study, the other two fan pressure ratios are included in a more detailed examination of the benefits of the ANC suppression levels. The key results of this extended study are the following observations: (1) The maximum overall benefit obtained from suppression of BPF alone was 2.5 EPNdB at high fan speeds. The suppression benefit increases with increase in fan pressure ratio (FPR), (2) The maximum overall benefit obtained from suppression of the first three harmonics was 3 EPNdB at high speeds. Suppression benefit increases with increase in FPR, (3) At low FPR, only about 1.0 EPNdB maximum reduction was obtained. Suppression is primarily from reduction of BPF at high FPR values and from the combination of tones at low FPR, (4) The benefit from ANC is about the same as the benefit from passive treatment at fan pressure

  10. UV/visible Fourier transform spectroscopy using an inductively-coupled plasma: dual-channel noise cancellation

    NASA Astrophysics Data System (ADS)

    Travis, J. C.; Winchester, M. R.; Salit, M. L.; Wythoff, B. J.; Scheeline, A.

    1993-04-01

    Although technological advances have extended the range of Fourier transform spectroscopy (FTS) into the UV/visible spectral domain, its application to spectroscopic and spectrometric problems has been hampered-relative to such applications in the infrared domain-by noise considerations. Although the technique retains high resolution, accurate wavelength registration, and simultaneous broad band coverage, the multiplex advantage present in the IR is severely compromised in the UV/visible due to the relative insignificance of detector noise. In particular, signal-carried noise distributes widely through the spectrum, degrading the dynamic range needed for many spectroscopic and analytical applications. This study demonstrates the use of complementary optical output channels in a commercial FTS to achieve up to ten-fold noise reductions for spectra acquired from an analytical inductively-coupled plasma with conventional pneumatic sample aspiration. The study also demonstrates the advisability of increasing the sampling rate of future instruments to exceed the maximum noise frequency characteristic of droplet evaporation effects.

  11. SEMICONDUCTOR INTEGRATED CIRCUITS: Noise-canceling and IP3 improved CMOS RF front-end for DRM/DAB/DVB-H applications

    NASA Astrophysics Data System (ADS)

    Keping, Wang; Zhigong, Wang; Xuemei, Lei

    2010-02-01

    A CMOS RF (radio frequency) front-end for digital radio broadcasting applications is presented that contains a wideband LNA, I/Q-mixers and VGAs, supporting other various wireless communication standards in the ultra-wide frequency band from 200 kHz to 2 GHz as well. Improvement of the NF (noise figure) and IP3 (third-order intermodulation distortion) is attained without significant degradation of other performances like voltage gain and power consumption. The NF is minimized by noise-canceling technology, and the IP3 is improved by using differential multiple gate transistors (DMGTR). The dB-in-linear VGA (variable gain amplifier) exploits a single PMOS to achieve exponential gain control. The circuit is fabricated in 0.18-μm CMOS technology. The S11 of the RF front-end is lower than -11.4 dB over the whole band of 200 kHz-2 GHz. The variable gain range is 12-42 dB at 0.25 GHz and 4-36 dB at 2 GHz. The DSB NF at maximum gain is 3.1-6.1 dB. The IIP3 at middle gain is -4.7 to 0.2 dBm. It consumes a DC power of only 36 mW at 1.8 V supply.

  12. Active control of automotive fan noise

    NASA Astrophysics Data System (ADS)

    Gerard, Anthony; Berry, Alain; Masson, Patrice

    2002-11-01

    Active control for globally reducing the noise radiated by automotive axial engine cooling fans is investigated. First, an aeroacoutic model of the fan is combined with acoustic directivity measurements to derive a distribution of equivalent dipole sources on the fan surface. The results reveal that the fan behaves like a distributed dipole at blade passage tones when the upstream flow through the fan is spatially nonuniform. Numerical simulations of active noise control in the free field have been carried out using the previous aeroacoustic model of the fan and a dipole secondary source in front of the fan. The numerical results show that a single dipole control source is effective in globally controlling the sound radiation of the fan at the blade passage frequency and its first harmonic. Last, an experimental investigation of active control is presented. It consists of a SISO feedforward configuration with either a LMS algorithm (for FIR filters) or a back-retropopagation algorithm (for neural networks) using the Simulink/Dspace environment for real-time implementation.

  13. An active noise reduction system for aircrew helmets

    NASA Technical Reports Server (NTRS)

    Wheeler, P. D.; Rawlinson, D.; Pelc, S. F.; Dorey, T. P.

    1978-01-01

    An active noise reduction system was developed for use in aircrew flying helmets in which the acoustic noise field inside the ear defender is detected using a miniature microphone and an antiphase signal is fed back to a communications telephone within the ear defender. Performance of the active noise reduction system in a laboratory trial simulating flight conditions is shown to be satisfactory.

  14. Active Control of Wind Tunnel Noise

    NASA Technical Reports Server (NTRS)

    Hollis, Patrick (Principal Investigator)

    1991-01-01

    The need for an adaptive active control system was realized, since a wind tunnel is subjected to variations in air velocity, temperature, air turbulence, and some other factors such as nonlinearity. Among many adaptive algorithms, the Least Mean Squares (LMS) algorithm, which is the simplest one, has been used in an Active Noise Control (ANC) system by some researchers. However, Eriksson's results, Eriksson (1985), showed instability in the ANC system with an ER filter for random noise input. The Restricted Least Squares (RLS) algorithm, although computationally more complex than the LMS algorithm, has better convergence and stability properties. The ANC system in the present work was simulated by using an FIR filter with an RLS algorithm for different inputs and for a number of plant models. Simulation results for the ANC system with acoustic feedback showed better robustness when used with the RLS algorithm than with the LMS algorithm for all types of inputs. Overall attenuation in the frequency domain was better in the case of the RLS adaptive algorithm. Simulation results with a more realistic plant model and an RLS adaptive algorithm showed a slower convergence rate than the case with an acoustic plant as a delay plant. However, the attenuation properties were satisfactory for the simulated system with the modified plant. The effect of filter length on the rate of convergence and attenuation was studied. It was found that the rate of convergence decreases with increase in filter length, whereas the attenuation increases with increase in filter length. The final design of the ANC system was simulated and found to have a reasonable convergence rate and good attenuation properties for an input containing discrete frequencies and random noise.

  15. Active Aircraft Pylon Noise Control System

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  16. On-line Monitoring and Active Control for Transformer Noise

    NASA Astrophysics Data System (ADS)

    Liang, Jiabi; Zhao, Tong; Tian, Chun; Wang, Xia; He, Zhenhua; Duan, Lunfeng

    This paper introduces the system for on-line monitoring and active noise control towards the transformer noise based on LabVIEW and the hardware equipment including the hardware and software. For the hardware part, it is mainly focused on the composition and the role of hardware devices, as well as the mounting location in the active noise control experiment. And the software part introduces the software flow chats, the measurement and analysis module for the sound pressure level including A, B, C weighting methods, the 1/n octave spectrum and the power spectrum, active noise control module and noise data access module.

  17. Active noise reduction systems: Their interaction with very low frequency acoustical energy

    NASA Astrophysics Data System (ADS)

    Crabtree, R. Brian

    1994-08-01

    Active noise reduction (ANR) is used for reducing noise at the ears of an observer through the action of interfering sound waves. Noise sensed by a microphone built into the observer's headset or helmet is processed and reintroduced into the ear cup cavity out of phase with the original sound, thus cancelling the noise at the ear. Recent field experience has shown that system exposure to very high amplitude low-frequency sound, such as during the operation of helicopters, can lead to saturation or overload of the ANR electronics. Experiments using acoustical maniquins were conducted to assess the low-frequency behavior of ANR equipment. Results of measurement of the threshold of overload indicated large differences in the saturation thresholds among systems tested. Performance strongly depended on the integrity of the ear seal. Those systems offering active attenuation into the infrasound region tended to saturate most easily, but did create the best listening condition for the user when operated below the saturation threshold.

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  20. A high quality voice coder with integrated echo canceller and voice activity detector for mobile satellite applications

    NASA Technical Reports Server (NTRS)

    Kondoz, A. M.; Evans, B. G.

    1993-01-01

    In the last decade, low bit rate speech coding research has received much attention resulting in newly developed, good quality, speech coders operating at as low as 4.8 Kb/s. Although speech quality at around 8 Kb/s is acceptable for a wide variety of applications, at 4.8 Kb/s more improvements in quality are necessary to make it acceptable to the majority of applications and users. In addition to the required low bit rate with acceptable speech quality, other facilities such as integrated digital echo cancellation and voice activity detection are now becoming necessary to provide a cost effective and compact solution. In this paper we describe a CELP speech coder with integrated echo canceller and a voice activity detector all of which have been implemented on a single DSP32C with 32 KBytes of SRAM. The quality of CELP coded speech has been improved significantly by a new codebook implementation which also simplifies the encoder/decoder complexity making room for the integration of a 64-tap echo canceller together with a voice activity detector.

  1. In-flight active wave cancelation with delayed-x-LMS control algorithm in a laminar boundary layer

    NASA Astrophysics Data System (ADS)

    Simon, Bernhard; Fabbiane, Nicolò; Nemitz, Timotheus; Bagheri, Shervin; Henningson, Dan S.; Grundmann, Sven

    2016-10-01

    This manuscript demonstrates the first successful application of the delayed-x-LMS (dxLMS) control algorithm for TS-wave cancelation. Active wave cancelation of two-dimensional broadband Tollmien-Schlichting (TS) disturbances is performed with a single DBD plasma actuator. The experiments are conducted in flight on the pressure side of a laminar flow wing glove, mounted on a manned glider. The stability properties of the controller are investigated in detail with experimental flight data, DNS and stability analysis of the boundary layer. Finally, a model-free approach for dxLMS operation is introduced to operate the controller as a `black-box' system, which automatically adjusts the controller settings based on a group speed measurement of the disturbance wave packets. The modified dxLMS controller is operated without a model and is able to adapt to varying conditions that may occur during flight in atmosphere.

  2. Role of colored noise in active dynamical theories

    NASA Astrophysics Data System (ADS)

    Kachan, Devin; Levine, Alex

    2015-03-01

    The noise driving many dynamical systems is temporally correlated, or colored. Biological motor proteins, for example, generate processive stresses in biopolymer networks, and it would be incorrect to model this forcing as uncorrelated white noise. To gain insight into the role of the noise spectrum, we study a phi⌃4 theory in the presence of active colored noise with renormalization group techniques. Using a frequency shell integration scheme, we perform an epsilon expansion around d =8 for power law noise of the form 1/f⌃2 and find frequency and wavevector dependent corrections to the transport coefficients. The power law noise assumption is, of course, an approximation: all physical processes possess a small frequency cutoff. We study the effect of this cutoff and find a change in scaling behavior as the system transitions from a power law divergent regime to one dominated by white noise.

  3. Low Speed, 2-D Rotor/Stator Active Noise Control at the Source Demonstration

    NASA Technical Reports Server (NTRS)

    Simonich, John C.; Kousen, Ken A.; Zander, Anthony C.; Bak, Michael; Topol, David A.

    1997-01-01

    Wake/blade-row interaction noise produced by the Annular Cascade Facility at Purdue University has been modeled using the LINFLO analysis. Actuator displacements needed for complete cancellation of the propagating acoustic response modes have been determined, along with the associated actuator power requirements. As an alternative, weighted least squares minimization of the total far-field sound power using individual actuators has also been examined. Attempts were made to translate the two-dimensional aerodynamic results into three-dimensional actuator requirements. The results lie near the limit of present actuator technology. In order to investigate the concept of noise control at the source for active rotor/stator noise control at the source, various techniques for embedding miniature actuators into vanes were examined. Numerous miniature speaker arrangements were tested and analyzed to determine their suitability as actuators for a demonstration test in the Annular Cascade Facility at Purdue. The best candidates demonstrated marginal performance. An alternative concept to using vane mounted speakers as control actuators was developed and tested. The concept uses compression drivers which are mounted externally to the stator vanes. Each compression driver is connected via a tube to an air cavity in the stator vane, from which the driver signal radiates into the working section of the experimental rig. The actual locations and dimensions of the actuators were used as input parameters for a LINFLO computational analysis of the actuator displacements required for complete cancellation of tones in the Purdue experimental rig. The actuators were designed and an arrangement determined which is compatible with the Purdue experimental rig and instrumentation. Experimental tests indicate that the actuators are capable of producing equivalent displacements greater than the requirements predicted by the LINFLO analysis. The acoustic output of the actuators was also found

  4. Microwave noise field: active radiometry principles and applications

    NASA Astrophysics Data System (ADS)

    Polivka, Jiri

    2012-06-01

    Principles of Active Radiometry are presented. Noise radiators are used to generate the low-coherence microwave noise field, and radiometers to evaluate its intensity, polarization and coherence. Several types of noise radiators are described as well as radiometers and antennas. The following applications are introduced: Material evaluation where insertion loss and reflectivity of grainy, irregular and moving objects are preferable. Microwave Coherence Tomography allowing the depth irregularity to be detected in low-loss objects. Near-Field antenna testing, field coherence evaluation, and spatial combining of noise radiators.

  5. Active flow control for Aeolian tone noise reduction

    NASA Technical Reports Server (NTRS)

    Hardin, Jay C.; Pope, D. Stuart

    1989-01-01

    This paper examines the use of active flow control for the purpose of noise reduction. As a simple demonstration of such techniques, several methods for controlling the wake and resulting noise production by a cylinder in a uniform stream are evaluated numerically.

  6. Firefighter noise exposure during training activities and general equipment use.

    PubMed

    Root, Kyle S; Schwennker, Catherine; Autenrieth, Daniel; Sandfort, Delvin R; Lipsey, Tiffany; Brazile, William J

    2013-01-01

    Multiple noise measurements were taken on 6 types of fire station equipment and 15 types of emergency response vehicle-related equipment used by firefighters during routine and emergency operations at 10 fire stations. Five of the six types of fire station equipment, when measured at a distance of one meter and ear level, emitted noise equal to or greater than 85 dBA, including lawn maintenance equipment, snow blowers, compressors, and emergency alarms. Thirteen of 15 types of equipment located on the fire engines emitted noise levels equal to or greater than 85 dBA, including fans, saws, alarms, and extrication equipment. In addition, noise measurements were taken during fire engine operations, including the idling vehicle, vehicle sirens, and water pumps. Results indicated that idling fire-engine noise levels were below 85 dBA; however, during water pump and siren use, noise levels exceeded 85 dBA, in some instances, at different locations around the trucks where firefighters would be stationed during emergency operations. To determine if the duration and use of fire fighting equipment was sufficient to result in overexposures to noise during routine training activities, 93 firefighter personal noise dosimetry samples were taken during 10 firefighter training activities. Two training activities per sampling day were monitored during each sampling event, for a mean exposure time of 70 min per day. The noise dosimetry samples were grouped based on job description to compare noise exposures between the different categories of job tasks commonly associated with fire fighting. The three job categories were interior, exterior, and engineering. Mean personal dosimetry results indicated that the average noise exposure was 78 dBA during the training activities that lasted 70 min on average. There was no significant difference in noise exposure between each of the three job categories. Although firefighters routinely use equipment and emergency response vehicles that

  7. Firefighter noise exposure during training activities and general equipment use.

    PubMed

    Root, Kyle S; Schwennker, Catherine; Autenrieth, Daniel; Sandfort, Delvin R; Lipsey, Tiffany; Brazile, William J

    2013-01-01

    Multiple noise measurements were taken on 6 types of fire station equipment and 15 types of emergency response vehicle-related equipment used by firefighters during routine and emergency operations at 10 fire stations. Five of the six types of fire station equipment, when measured at a distance of one meter and ear level, emitted noise equal to or greater than 85 dBA, including lawn maintenance equipment, snow blowers, compressors, and emergency alarms. Thirteen of 15 types of equipment located on the fire engines emitted noise levels equal to or greater than 85 dBA, including fans, saws, alarms, and extrication equipment. In addition, noise measurements were taken during fire engine operations, including the idling vehicle, vehicle sirens, and water pumps. Results indicated that idling fire-engine noise levels were below 85 dBA; however, during water pump and siren use, noise levels exceeded 85 dBA, in some instances, at different locations around the trucks where firefighters would be stationed during emergency operations. To determine if the duration and use of fire fighting equipment was sufficient to result in overexposures to noise during routine training activities, 93 firefighter personal noise dosimetry samples were taken during 10 firefighter training activities. Two training activities per sampling day were monitored during each sampling event, for a mean exposure time of 70 min per day. The noise dosimetry samples were grouped based on job description to compare noise exposures between the different categories of job tasks commonly associated with fire fighting. The three job categories were interior, exterior, and engineering. Mean personal dosimetry results indicated that the average noise exposure was 78 dBA during the training activities that lasted 70 min on average. There was no significant difference in noise exposure between each of the three job categories. Although firefighters routinely use equipment and emergency response vehicles that

  8. Application of Feedforward Adaptive Active-Noise Control for Reducing Blade Passing Noise in Centrifugal Fans

    NASA Astrophysics Data System (ADS)

    WU, J.-D.; BAI, M. R.

    2001-02-01

    This paper describes two configurations of feedforward adaptive active-noise control (ANC) technique for reducing blade passing noise in centrifugal fans. In one configuration, the control speaker is installed at the cut-off region of the fan, while in the other configuration at the exit duct. The proposed ANC system is based on the filtered-x least-mean-squares (FXLMS) algorithm with multi-sine synthesized reference signal and frequency counting and is implemented by using a digital signal processor (DSP). Experiments are carried out to evaluate the proposed system for reducing the noise at the blade passing frequency (BPF) and its harmonics at various flow speeds. The results of the experiment indicated that the ANC technique is effective in reducing the blade passing noise for two configurations by using the feedforward adaptive control.

  9. Active Noise Control Experiments using Sound Energy Flu

    NASA Astrophysics Data System (ADS)

    Krause, Uli

    2015-03-01

    This paper reports on the latest results concerning the active noise control approach using net flow of acoustic energy. The test set-up consists of two loudspeakers simulating the engine noise and two smaller loudspeakers which belong to the active noise system. The system is completed by two acceleration sensors and one microphone per loudspeaker. The microphones are located in the near sound field of the loudspeakers. The control algorithm including the update equation of the feed-forward controller is introduced. Numerical simulations are performed with a comparison to a state of the art method minimising the radiated sound power. The proposed approach is experimentally validated.

  10. Active control of low-speed turbofan tonal noise

    NASA Astrophysics Data System (ADS)

    Sommerfeldt, Scott D.; Remington, Paul J.

    2003-10-01

    Active noise control has been proposed as a technique for reducing the tonal noise radiated from turbofan engines. The sound field in the duct of a turbofan engine is characterized by acoustic modes, which exhibit both a radial and a circumferential spatial dependence. The dominant circumferential modes are determined by the relationship between the number of rotor and stator blades. Using these concepts, an active noise control system has been developed to measure and minimize the modes in the duct of a turbofan engine. By using multiple source and sensor locations, it has also been shown that it is possible to control multiple radial modes within the engine duct. Some of the issues associated with the design of the control system will be reviewed, and results obtained using the Active Noise Control Fan (ANCF) at NASA Glenn Research Center will be presented. [Work supported by NASA.

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

    PubMed Central

    Sætrevik, Bjørn; Sörqvist, Patrik

    2015-01-01

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

  12. A turn-key Concept for active cancellation of Global Positioning System L3 Signal

    NASA Astrophysics Data System (ADS)

    Nigra, Lou; Lewis, B. M.; Edgar, C. E.; Perillat, P.; Quintero, L.; Stanimirovic, S.; Gallagher, J. S., III

    2011-01-01

    We present a concept, developed at the National Astronomy and Ionosphere Center (NAIC) at Arecibo, Puerto Rico, for suppression of Global Positioning System (GPS) signals in the 305 m dish radio receiver path prior to backend processing. The subsystem does not require an auxiliary antenna and is intended for easy integration with radio telescope systems with a goal of being a turnkey addition to virtually any facility. We have focused on detection and cancellation of the GPS L3 signal at 1381.05 MHz which, during periodic test modes and particularly during system-wide tests, interfere with observations of objects in a range of redshifts that includes the Coma supercluster, for example. The signal can dynamically change modulation modes and our scheme has demonstrated, through simulations using actual sampled telescope data, the ability to acquire and track these signals as well as detect the mode changes in order to apply cancellation or blanking, as appropriate. The subsystem can also be adapted to GPS L1 (1575.42 MHz), L2C (1227.6 MHz), and others. A follow-up is underway to develop a prototype to deploy and evaluate at NAIC.

  13. Quelling Cabin Noise in Turboprop Aircraft via Active Control

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  14. Active control of fan-generated plane wave noise

    NASA Astrophysics Data System (ADS)

    Gerhold, Carl H.; Nuckolls, William E.; Santamaria, Odillyn L.; Martinson, Scott D.

    1993-08-01

    Subsonic propulsion systems for future aircraft may incorporate ultra-high bypass ratio ducted fan engines whose dominant noise source is the fan with blade passage frequency less than 1000 Hz. This low frequency combines with the requirement of a short nacelle to diminish the effectiveness of passive duct liners. Active noise control is seen as a viable method to augment the conventional passive treatments. An experiment to control ducted fan noise using a time domain active adaptive system is reported. The control sound source consists of loudspeakers arrayed around the fan duct. The error sensor location is in the fan duct. The purpose of this experiment is to demonstrate that the in-duct error sensor reduces the mode spillover in the far field, thereby increasing the efficiency of the control system. In this first series of tests, the fan is configured so that predominantly zero order circumferential waves are generated. The control system is found to reduce the blade passage frequency tone significantly in the acoustic far field when the mode orders of the noise source and of the control source are the same. The noise reduction is not as great when the mode orders are not the same even though the noise source modes are evanescent, but the control system converges stably and global noise reduction is demonstrated in the far field. Further experimentation is planned in which the performance of the system will be evaluated when higher order radial and spinning modes are generated.

  15. Active control of fan-generated plane wave noise

    NASA Technical Reports Server (NTRS)

    Gerhold, Carl H.; Nuckolls, William E.; Santamaria, Odillyn L.; Martinson, Scott D.

    1993-01-01

    Subsonic propulsion systems for future aircraft may incorporate ultra-high bypass ratio ducted fan engines whose dominant noise source is the fan with blade passage frequency less than 1000 Hz. This low frequency combines with the requirement of a short nacelle to diminish the effectiveness of passive duct liners. Active noise control is seen as a viable method to augment the conventional passive treatments. An experiment to control ducted fan noise using a time domain active adaptive system is reported. The control sound source consists of loudspeakers arrayed around the fan duct. The error sensor location is in the fan duct. The purpose of this experiment is to demonstrate that the in-duct error sensor reduces the mode spillover in the far field, thereby increasing the efficiency of the control system. In this first series of tests, the fan is configured so that predominantly zero order circumferential waves are generated. The control system is found to reduce the blade passage frequency tone significantly in the acoustic far field when the mode orders of the noise source and of the control source are the same. The noise reduction is not as great when the mode orders are not the same even though the noise source modes are evanescent, but the control system converges stably and global noise reduction is demonstrated in the far field. Further experimentation is planned in which the performance of the system will be evaluated when higher order radial and spinning modes are generated.

  16. Sound quality of low-frequency and car engine noises after active noise control

    NASA Astrophysics Data System (ADS)

    Gonzalez, A.; Ferrer, M.; de Diego, M.; Piñero, G.; Garcia-Bonito, J. J.

    2003-08-01

    The ability of active noise control (ANC) systems to achieve a more pleasant sound has been evaluated by means of sound quality analysis of a real multi-channel active noise controller. Recordings of real car engine noises had been carried out using a Head acoustics TM binaural head simulator seated in a typical car seat, and these signals together with synthesized noise have been actively controlled in an enclosed room. The sound quality study has focused on the estimation of noise quality changes through the evaluation of the sense of comfort. Two methods have been developed: firstly, a predictive method based on psychoacoustic parameters (loudness, roughness, tonality and sharpness); and secondly, a subjective method using a jury test. Both results have been related to the spectral characteristics of the sounds before and after active control. It can be concluded from both analyses that ANC positively affects acoustic comfort. The engine noise mathematical comfort predictor is based on loudness and roughness (two psychoacoustic parameters directly influenced by ANC), and has satisfactorily predicted the improvements in the pleasantness of the sounds. As far as the subjective evaluation method is concerned, the jury test has showed that acoustic comfort is, in most cases, directly related to the sense of quietness. However, ANC has also been assessed negatively by the jury in the cases that it was unable to reduce the loudness, perhaps because of the low amplitudes of the original sounds. Finally, from what has been shown, it can be said that the subjective improvements strongly depends on the attenuation level achieved by the ANC system operation, as well as the spectral characteristics of the sounds before and after control.

  17. Collisional activation with random noise in ion trap mass spectrometry

    SciTech Connect

    McLuckey, S.A.; Goeringer, D.E.; Glish, G.L.

    1992-07-01

    Random noise applied to the end caps of a quadrupole ion trap is shown to be an effective means for the collisional activation of trapped ions independent of mass/charge ratio and number of ions. This technique is compared and contrasted with conventional single-frequency collisional activation for the molecular ion of N,N-dimethylaniline, protonated cocaine, the molecular anion of 2,4,6-trinitrotoluene, and doubly protonated neuromedin U-8. Collisional activation with noise tends to produce more extensive fragmentation than the conventional approach due to the fact that product ions are also kinetically excited in the noise experiment. The efficiency of the noise experiment in producing detectable product ions relative to the conventional approach ranges from being equivalent to being a factor of 3 less efficient. Furthermore, discrimination against low mass/charge product ions is apparent in the data from multiply charged biomolecules. Nevertheless, collisional activation with random noise provides a very simple means for overcoming problems associated with the dependence of single-frequency collisional activation on mass/charge ratio and the number of ions in the ion trap. 45 refs., 7 figs.

  18. 34 CFR 674.59 - Cancellation for military service.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... balance on an NDSL or Perkins loan for active duty service that ended before August 14, 2008, as a member... 34 Education 3 2011-07-01 2011-07-01 false Cancellation for military service. 674.59 Section 674... Cancellation for military service. (a) Cancellation on a Defense loan. (1) An institution must cancel up to...

  19. The use of active noise control (ANC) to reduce acoustic noise generated during MRI scanning: some initial results.

    PubMed

    McJury, M; Stewart, R W; Crawford, D; Toma, E

    1997-01-01

    MRI scanning generates high levels of acoustic noise that cannot only pose a safety hazard, but also impair communication between staff and patient. In this article we present active noise control (ANC) techniques that introduce antiphase noise to destructively interfere with the MRI noise and with the aim of producing a zone of quiet around the patient's ears. Using noise recorded from a 1.0 Tesla midfield MR scanner the acoustic noise generated by three standard MR imaging sequences was replayed to a real time two channel ANC system. The results obtained show a useful attenuation of low-frequency periodic acoustic noise components. Therefore, in combination with standard passive ear protection, this suggests that MR generated acoustic noise can be effectively attenuated at both low and high frequencies leading to improved patient comfort.

  20. An evaluation of active noise control in a cylindrical shell

    NASA Technical Reports Server (NTRS)

    Silcox, R. J.; Lester, H. C.; Abler, S. B.

    1987-01-01

    The physical mechanisms governing the use of active noise control in an extended volume of a cylindrical shell are discussed. Measured data was compared with computer results from a previously derived analytical model based on an infinite shell theory. For both the analytical model and experiment, the radiation of the external monopoles is coupled to the internal acoustic field through the radial displacement of the thin, elastic cylindrical shell. An active noise control system was implemented in the cylinder using a fixed array of discrete monopole sources, all of which lie in the plane of the exterior noise sources. Good agreement between measurement and prediction was obtained for both internal pressure response and overall noise reduction. Attenuations in the source plane greater than 15 dB were recorded along with a uniformly quieted noise environment over the entire length of the experimental model. Results indicate that for extended axial forcing distributions or very low shell damping, axial arrays of control sources may be required. Finally, the Nyquist criteria for the number of azimuthal control sources is shown to provide for effective control over the full cylinder cross section.

  1. An evaluation of active noise control in a cylindrical shell

    NASA Technical Reports Server (NTRS)

    Silcox, R. J.; Lester, H. C.; Abler, S. B.

    1989-01-01

    The physical mechanisms governing the use of active noise control in an extended volume of a cylindrical shell are discussed. Measured data was compared with computer results from a previously derived analytical model based on an infinite shell theory. For both the analytical model and experiment, the radiation of the external monopoles is coupled to the internal acoustic field through the radial displacement of the thin, elastic cylindrical shell. An active noise control system was implemented in the cylinder using a fixed array of discrete monopole sources, all of which lie in the plane of the exterior noise sources. Good agreement between measurement and prediction was obtained for both internal pressure response and overall noise reduction. Attenuations in the source plane greater than 15 dB were recorded along with a uniformly quieted noise environment over the entire length of the experimental model. Results indicate that for extended axial forcing distributions or very low shell damping, axial arrays of control sources may be required. Finally, the Nyquist criteria for the number of azimuthal control sources is shown to provide for effective control over the full cylinder cross section.

  2. Applications of active adaptive noise control to jet engines

    NASA Technical Reports Server (NTRS)

    Shoureshi, Rahmat; Brackney, Larry

    1993-01-01

    During phase 2 research on the application of active noise control to jet engines, the development of multiple-input/multiple-output (MIMO) active adaptive noise control algorithms and acoustic/controls models for turbofan engines were considered. Specific goals for this research phase included: (1) implementation of a MIMO adaptive minimum variance active noise controller; and (2) turbofan engine model development. A minimum variance control law for adaptive active noise control has been developed, simulated, and implemented for single-input/single-output (SISO) systems. Since acoustic systems tend to be distributed, multiple sensors, and actuators are more appropriate. As such, the SISO minimum variance controller was extended to the MIMO case. Simulation and experimental results are presented. A state-space model of a simplified gas turbine engine is developed using the bond graph technique. The model retains important system behavior, yet is of low enough order to be useful for controller design. Expansion of the model to include multiple stages and spools is also discussed.

  3. A multi-resolution filtered-x LMS algorithm based on discrete wavelet transform for active noise control

    NASA Astrophysics Data System (ADS)

    Qiu, Z.; Lee, C.-M.; Xu, Z. H.; Sui, L. N.

    2016-01-01

    We have developed a new active control algorithm based on discrete wavelet transform (DWT) for both stationary and non-stationary noise control. First, the Mallat pyramidal algorithm is introduced to implement the DWT, which can decompose the reference signal into several sub-bands with multi-resolution and provides a perfect reconstruction (PR) procedure. To reduce the extra computational complexity introduced by DWT, an efficient strategy is proposed that updates the adaptive filter coefficients in the frequency domainDeepthi B.B using a fast Fourier transform (FFT). Based on the reference noise source, a 'Haar' wavelet is employed and by decomposing the noise signal into two sub-band (3-band), the proposed DWT-FFT-based FXLMS (DWT-FFT-FXLMS) algorithm has greatly reduced complexity and a better convergence performance compared to a time domain filtered-x least mean square (TD-FXLMS) algorithm. As a result of the outstanding time-frequency characteristics of wavelet analysis, the proposed DWT-FFT-FXLMS algorithm can effectively cancel both stationary and non-stationary noise, whereas the frequency domain FXLMS (FD-FXLMS) algorithm cannot approach this point.

  4. Regular Wave Propagation Out of Noise in Chemical Active Media

    SciTech Connect

    Alonso, S.; Sendina-Nadal, I.; Perez-Munuzuri, V.; Sancho, J. M.; Sagues, F.

    2001-08-13

    A pacemaker, regularly emitting chemical waves, is created out of noise when an excitable photosensitive Belousov-Zhabotinsky medium, strictly unable to autonomously initiate autowaves, is forced with a spatiotemporal patterned random illumination. These experimental observations are also reproduced numerically by using a set of reaction-diffusion equations for an activator-inhibitor model, and further analytically interpreted in terms of genuine coupling effects arising from parametric fluctuations. Within the same framework we also address situations of noise-sustained propagation in subexcitable media.

  5. Multichannel active noise control system for local spectral reshaping of multifrequency noise

    NASA Astrophysics Data System (ADS)

    de Diego, M.; Gonzalez, A.; Ferrer, M.; Piñero, G.

    2004-07-01

    This paper discusses the development of a multichannel active system for local spectral reshaping of multitone noise. The aim of this work is to design a real practical system that performs well in local active noise control (ANC) applications, and so improving the comfort sensation produced by enclosed sound fields. The adaptive algorithm implemented in the controller is a multichannel extension of the multifrequency adaptive equalizer developed by Kuo. The philosophy behind these equalizers lies in independently controlling some given frequencies of a primary signal. Moreover, the algorithm should manage to generate usefully sized zones of equalization in order to allow for the head motion of somebody with restricted mobility; for example, a passenger seated in a car. To verify the successful implementation of the multichannel system, experiments were carried out under listening room conditions. The developed prototype consists of an array of up to four microphones used as error sensors and two secondary sources. A 4100-type Bruel and Kjaer mannequin with two calibrated microphones at the ear canals was used to measure sound levels in a hypothetical listener's head. Different synthesized repetitive noises were used, as reference signals, specifically repetitive noise with harmonics of 15, 20, and 28 Hz, as well as an 80 Hz single tone. The equalized points include an area around the error sensor positions, and these are measured using the mannequin and an x- y moving platform. The extent to which the experimental equalization zones obtained favourable results validates the multichannel local ANC equalization system. Different error sensor positions around the listener head were also tested. The residual field inside the equalization zone was measured in all cases.

  6. Noise control using a plate radiator and an acoustic resonator

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor)

    1996-01-01

    An active noise control subassembly for reducing noise caused by a source (such as an aircraft engine) independent of the subassembly. A noise radiating panel is bendably vibratable to generate a panel noise canceling at least a portion of the source noise. A piezoceramic actuator plate is connected to the panel. A front plate is spaced apart from the panel and the first plate, is positioned generally between the source noise and the panel, and has a sound exit port. A first pair of spaced-apart side walls each generally abut the panel and the front plate so as to generally enclose a front cavity to define a resonator.

  7. Scope for active noise abatement in vehicle diesel engines

    NASA Astrophysics Data System (ADS)

    Summerauer, I.; Boesch, N.

    1984-04-01

    Noise reduction measures must be directed to the engine, the exhaust system, and the cooling system (fan) all of which contribute approximately 90% of the sound energy emitted from commercial diesel trucks. The noise generation processes were visualized and limiting conditions fixed by law were considered in establishing criteria for active solar noise abatement measures. A more effective silencer and better vibration damping on the surface of the silencer and exhaust pipes can reduce noise from the exhaust system. Acoustic emission generated by the fan and air flow can be reduced by decreasing flow velocity or by turning on the fan only when a full cooling output is required (10% of the time). Active measures are needed on the engine itself either at the point of the solid-borne sound transmission or at the point of the solid-borne vibrations. The predominant effect is on the engine casing; oil sump; air suction pipe or air charge line; the flywheel casing; and the clutch housing.

  8. Active Flow Effectors for Noise and Separation Control

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.

    2011-01-01

    New flow effector technology for separation control and enhanced mixing is based upon shape memory alloy hybrid composite (SMAHC) technology. The technology allows for variable shape control of aircraft structures through actively deformable surfaces. The flow effectors are made by embedding shape memory alloy actuator material in a composite structure. When thermally actuated, the flow effector def1ects into or out of the flow in a prescribed manner to enhance mixing or induce separation for a variety of applications, including aeroacoustic noise reduction, drag reduction, and f1ight control. The active flow effectors were developed for noise reduction as an alternative to fixed-configuration effectors, such as static chevrons, that cannot be optimized for airframe installation effects or variable operating conditions and cannot be retracted for off-design or fail-safe conditions. Benefits include: Increased vehicle control, overall efficiency, and reduced noise throughout all f1ight regimes, Reduced flow noise, Reduced drag, Simplicity of design and fabrication, Simplicity of control through direct current stimulation, autonomous re sponse to environmental heating, fast re sponse, and a high degree of geometric stability. The concept involves embedding prestrained SMA actuators on one side of the chevron neutral axis in order to generate a thermal moment and def1ect the structure out of plane when heated. The force developed in the host structure during def1ection and the aerodynamic load is used for returning the structure to the retracted position. The chevron design is highly scalable and versatile, and easily affords active and/or autonomous (environmental) control. The technology offers wide-ranging market applications, including aerospace, automotive, and any application that requires flow separation or noise control.

  9. The Timing of Noise-Sensitive Activities in Residential Areas

    NASA Technical Reports Server (NTRS)

    Fields, J. M.

    1985-01-01

    Data from a nationally representative survey of time use was analyzed to provide estimates of the percentage of the population which is engaged in noise sensitive activities during each hour of the day on weekdays, Fridays, Saturdays and Sundays. Estimates are provided of the percentage engaged in aural communication activities at home, sleeping at home, or simply at home. The day can be roughly divided into four noise sensitivity periods consisting of two relatively steady state periods, night and day and the early morning and evening transition periods. Weekends differ from weekdays in that the morning transition period is one hour later and the numbers of people engaged in aural communication during the day at home are approximately one-half to three-quarters greater. The extent and timing of noise sensitive activities was found to be similiar for all parts of the United States, for different sizes of urban areas, and for the three seasons surveyed (September through May). The timing of activity periods does not differ greatly by sex or age even though women and people over 65 are much more likely to be at home during the daytime.

  10. Hybrid Active/Passive Jet Engine Noise Suppression System

    NASA Technical Reports Server (NTRS)

    Parente, C. A.; Arcas, N.; Walker, B. E.; Hersh, A. S.; Rice, E. J.

    1999-01-01

    A novel adaptive segmented liner concept has been developed that employs active control elements to modify the in-duct sound field to enhance the tone-suppressing performance of passive liner elements. This could potentially allow engine designs that inherently produce more tone noise but less broadband noise, or could allow passive liner designs to more optimally address high frequency broadband noise. A proof-of-concept validation program was undertaken, consisting of the development of an adaptive segmented liner that would maximize attenuation of two radial modes in a circular or annular duct. The liner consisted of a leading active segment with dual annuli of axially spaced active Helmholtz resonators, followed by an optimized passive liner and then an array of sensing microphones. Three successively complex versions of the adaptive liner were constructed and their performances tested relative to the performance of optimized uniform passive and segmented passive liners. The salient results of the tests were: The adaptive segmented liner performed well in a high flow speed model fan inlet environment, was successfully scaled to a high sound frequency and successfully attenuated three radial modes using sensor and active resonator arrays that were designed for a two mode, lower frequency environment.

  11. The timing of noise-sensitive activities in residential areas

    NASA Astrophysics Data System (ADS)

    Fields, J. M.

    1985-07-01

    Data from a nationally representative survey of time use was analyzed to provide estimates of the percentage of the population which is engaged in noise sensitive activities during each hour of the day on weekdays, Fridays, Saturdays and Sundays. Estimates are provided of the percentage engaged in aural communication activities at home, sleeping at home, or simply at home. The day can be roughly divided into four noise sensitivity periods consisting of two relatively steady state periods, night and day and the early morning and evening transition periods. Weekends differ from weekdays in that the morning transition period is one hour later and the numbers of people engaged in aural communication during the day at home are approximately one-half to three-quarters greater. The extent and timing of noise sensitive activities was found to be similiar for all parts of the United States, for different sizes of urban areas, and for the three seasons surveyed (September through May). The timing of activity periods does not differ greatly by sex or age even though women and people over 65 are much more likely to be at home during the daytime.

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

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  13. Active Control of Fan-Generated Tone Noise

    NASA Technical Reports Server (NTRS)

    Gerhold, Carl H.

    1995-01-01

    This paper reports on an experiment to control the noise radiated from the inlet of a ducted fan using a time domain active adaptive system. The control ,sound source consists of loudspeakers arranged in a ring around the fan duct. The error sensor location is in the fan duct. The purpose of this experiment is to demonstrate that the in-duct error sensor reduces the mode spillover in the far field, thereby increasing the efficiency of the control system. The control system is found to reduce the blade passage frequency tone significantly in the acoustic far field when the mode orders of the noise source and of the control source are the same, when the dominant wave in the duct is a plane wave. The presence of higher order modes in the duct reduces the noise reduction efficiency, particularly near the mode cut-on where the standing wave component is strong, but the control system converges stably. The control system is stable and converges when the first circumferential mode is generated in the duct. The control system is found to reduce the fan noise in the far field on an arc around the fan inlet by as much as 20 dB with none of the sound amplification associated with mode spillover.

  14. Noise-activated dissociation of soft elastic contacts.

    PubMed

    Chaudhury, M K; Goohpattader, P S

    2012-12-01

    Adhesive forces are capable of deforming a soft elastic object when it comes in contact with a flat rigid substrate. The contact is in stable equilibrium if the total energy of the system arising from the elastic and surface forces exhibits a minimum at a zero or at a slightly negative load. However, as the system is continually unloaded, the energy barrier decreases and it eventually disappears, thus leading to a ballistic separation of the contact. While this type of contact splitting has received wide recognition, what has not been much appreciated with these types of soft adhesion problems is that rupture of a contact can also occur at any finite sub critical load in the presence of a noise. The soft contact problems are unique in that the noise can be athermal, whereas the metastable and stable states of the thermodynamic potential can arise from the competition of the elastic and the interfacial energies of the system. Analysis based on Kramers' theory and simulations based on Langevin dynamics show that the contact rupture dynamics is amenable to an Eyring's form of a force and noise-induced escape of a particle from a potential well that is generic to various types of colloidal and macromolecular processes. These ideas are useful in understanding the results of a recent experiment involving the noise-activated rolling dynamics of a rigid sphere on a surface, where it is pinned by soft micro-fibrillar contacts.

  15. Comparison of Active Noise Control Structures in the Presence of Acoustical Feedback by Using THEH∞SYNTHESIS Technique

    NASA Astrophysics Data System (ADS)

    Bai, M. R.; Lin, H. H.

    1997-10-01

    This study compares three control structures of active noise cancellation for ducts: feedback control, feedforward control, and hybrid control. These structures are compared in terms of performance, stability, and robustness by using a general framework of theH∞robust control theory. In addition, theH∞synthesis procedure automatically incorporates the acoustic feedback path that is usually a plaguing problem to feedforward control design. The controllers are implemented by using a digital signal processor and tested on a finite-length duct. In an experimental verification, the proposed controllers are also compared with the well-known filtered-uleast mean square (FULMS) controller. The advantages and disadvantages of each ANC structure as well as the adverse effects due to acoustic feedback are addressed.

  16. 30 CFR 551.9 - Temporarily stopping, canceling, or relinquishing activities approved under a permit.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... relinquishing activities approved under a permit. 551.9 Section 551.9 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE GEOLOGICAL AND GEOPHYSICAL (G&G) EXPLORATIONS OF THE OUTER.... (a) BOEM may temporarily stop exploration or scientific research activities under a permit when...

  17. 30 CFR 551.9 - Temporarily stopping, canceling, or relinquishing activities approved under a permit.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... relinquishing activities approved under a permit. 551.9 Section 551.9 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE GEOLOGICAL AND GEOPHYSICAL (G&G) EXPLORATIONS OF THE OUTER.... (a) BOEM may temporarily stop exploration or scientific research activities under a permit when...

  18. 30 CFR 551.9 - Temporarily stopping, canceling, or relinquishing activities approved under a permit.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... relinquishing activities approved under a permit. 551.9 Section 551.9 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE GEOLOGICAL AND GEOPHYSCIAL (G&G) EXPLORATIONS OF THE OUTER.... (a) BOEM may temporarily stop exploration or scientific research activities under a permit when...

  19. 14-3-3-dependent inhibition of the deubiquitinating activity of UBPY and its cancellation in the M phase

    SciTech Connect

    Mizuno, Emi; Kitamura, Naomi; Komada, Masayuki

    2007-10-01

    The deubiquitinating enzyme UBPY, also known as USP8, regulates cargo sorting and membrane traffic at early endosomes. Here we demonstrate the regulatory mechanism of the UBPY catalytic activity. We identified 14-3-3 {epsilon}, {gamma}, and {zeta} as UBPY-binding proteins using co-immunoprecipitation followed by mass spectrometric analysis. The 14-3-3 binding of UBPY was inhibited by mutating the consensus 14-3-3-binding motif RSYS{sup 680}SP, by phosphatase treatment, and by competition with the Ser{sup 680}-phosphorylated RSYS{sup 680}SP peptide. Metabolic labeling with [{sup 32}P]orthophosphate and immunoblotting using antibody against the phosphorylated 14-3-3-binding motif showed that Ser{sup 680} is a major phosphorylation site in UBPY. These results indicated that 14-3-3s bind to the region surrounding Ser{sup 680} in a phosphorylation-dependent manner. The mutation at Ser{sup 680} led to enhanced ubiquitin isopeptidase activity of UBPY toward poly-ubiquitin chains and a cellular substrate, epidermal growth factor receptor, in vitro and in vivo. Moreover, addition of 14-3-3{epsilon} inhibited the UBPY activity in vitro. Finally, UBPY was dephosphorylated at Ser{sup 680} and dissociated from 14-3-3s in the M phase, resulting in enhanced activity of UBPY during cell division. We conclude that UBPY is catalytically inhibited in a phosphorylation-dependent manner by 14-3-3s during the interphase, and this regulation is cancelled in the M phase.

  20. Active Control of Fan Noise by Vane Actuators

    NASA Technical Reports Server (NTRS)

    Curtis, Alan R. D.

    1999-01-01

    An active noise control system for ducted fan noise was built that uses actuators located in stator vanes. The actuators were piezoelectric benders manufactured using the THUNDER technology and were custom designed for the application. The active noise control system was installed in the NASA ANCF rig. Four actuator array with a total of 168 actuators in 28 stator vanes were used. Simultaneous reductions of acoustic power in both the inlet and exhaust duct were demonstrated for a fan disturbance that contained two radial mode orders in both inlet and exhaust. Total power levels in the target modes were reduced by up to 9 dB in the inlet and total tone levels by over 6 dB while exhaust power levels were reduced by up to 3 dB. Far field sound pressure level reductions of up to 17 dB were observed. A simpler control system, matched to the location of the disturbance with two radial actuator arrays, was demonstrated to control total acoustic power in four disturbance modes simultaneously in inlet and exhaust. The vane actuator met the requirements given for the ANCF, although in practice the performance of the system was limited by the constraints of the power amplifiers and the presence of control spillover. The vane actuators were robust. None of the 168 vane actuators failed during the tests.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  2. Noise exposure immediately activates cochlear mitogen-activated protein kinase signaling.

    PubMed

    Alagramam, Kumar N; Stepanyan, Ruben; Jamesdaniel, Samson; Chen, Daniel H-C; Davis, Rickie R

    2014-01-01

    Noise-induced hearing loss (NIHL) is a major public health issue worldwide. Uncovering the early molecular events associated with NIHL would reveal mechanisms leading to the hearing loss. Our aim is to investigate the immediate molecular responses after different levels of noise exposure and identify the common and distinct pathways that mediate NIHL. Previous work showed mice exposed to 116 decibels sound pressure level (dB SPL) broadband noise for 1 h had greater threshold shifts than the mice exposed to 110 dB SPL broadband noise, hence we used these two noise levels in this study. Groups of 4-8-week-old CBA/CaJ mice were exposed to no noise (control) or to broadband noise for 1 h, followed by transcriptome analysis of total cochlear RNA isolated immediately after noise exposure. Previously identified and novel genes were found in all data sets. Following exposure to noise at 116 dB SPL, the earliest responses included up-regulation of 243 genes and down-regulation of 61 genes, while a similar exposure at 110 dB SPL up-regulated 155 genes and down-regulated 221 genes. Bioinformatics analysis indicated that mitogen-activated protein kinase (MAPK) signaling was the major pathway in both levels of noise exposure. Nevertheless, both qualitative and quantitative differences were noticed in some MAPK signaling genes, after exposure to different noise levels. Cacna1b , Cacna1g , and Pla2g6 , related to calcium signaling were down-regulated after 110 dB SPL exposure, while the fold increase in the expression of Fos was relatively lower than what was observed after 116 dB SPL exposure. These subtle variations provide insight on the factors that may contribute to the differences in NIHL despite the activation of a common pathway.

  3. Active and passive noise control using electroactive polymer actuators (EAPAs)

    NASA Astrophysics Data System (ADS)

    Ramanathan, Kartik; Zhu, Bei; Chang, Woosuk; Varadan, Vasundara V.; Varadan, Vijay K.

    1999-06-01

    Electro-active polymer actuators (EAPA) have been a topic of research interest in the recent decades due to their ability to produce large strains under the influence of relatively low electric fields as compared to commercially available actuators. This paper investigates the feasibility of EAPA for active and passive cabin noise control. The passive damping characteristics of EAPA were determined, by measuring the transmission loss of four samples of various thickness and composition in an anechoic chamber in the 200 - 2000 Hz frequency range. This was then compared to that of Plexiglas and silicone rubber sheets of comparable thickness. The transmission loss of EAPA and Plexiglas were observed to be about the same. The transmission loss of EAPA was greater than that of silicone rubber, of the same thickness. The experimental and theoretical results computed using the mass law agree well. EAPA produces a strain of 0.006 for an applied field of 1 V/m. The ability of EAPA to potentially provide active as well as passive damping in the low to intermediate frequency range, along with being light- weight, pliable and transparent, makes it attractive for noise control applications as active/passive windows or wall papers.

  4. Active noise control using a steerable parametric array loudspeaker.

    PubMed

    Tanaka, Nobuo; Tanaka, Motoki

    2010-06-01

    Arguably active noise control enables the sound suppression at the designated control points, while the sound pressure except the targeted locations is likely to augment. The reason is clear; a control source normally radiates the sound omnidirectionally. To cope with this problem, this paper introduces a parametric array loudspeaker (PAL) which produces a spatially focused sound beam due to the attribute of ultrasound used for carrier waves, thereby allowing one to suppress the sound pressure at the designated point without causing spillover in the whole sound field. First the fundamental characteristics of PAL are overviewed. The scattered pressure in the near field contributed by source strength of PAL is then described, which is needed for the design of an active noise control system. Furthermore, the optimal control law for minimizing the sound pressure at control points is derived, the control effect being investigated analytically and experimentally. With a view to tracking a moving target point, a steerable PAL based upon a phased array scheme is presented, with the result that the generation of a moving zone of quiet becomes possible without mechanically rotating the PAL. An experiment is finally conducted, demonstrating the validity of the proposed method.

  5. What kind of noise is brain noise: anomalous scaling behavior of the resting brain activity fluctuations

    PubMed Central

    Fraiman, Daniel; Chialvo, Dante R.

    2012-01-01

    The study of spontaneous fluctuations of brain activity, often referred as brain noise, is getting increasing attention in functional magnetic resonance imaging (fMRI) studies. Despite important efforts, much of the statistical properties of such fluctuations remain largely unknown. This work scrutinizes these fluctuations looking at specific statistical properties which are relevant to clarify its dynamical origins. Here, three statistical features which clearly differentiate brain data from naive expectations for random processes are uncovered: First, the variance of the fMRI mean signal as a function of the number of averaged voxels remains constant across a wide range of observed clusters sizes. Second, the anomalous behavior of the variance is originated by bursts of synchronized activity across regions, regardless of their widely different sizes. Finally, the correlation length (i.e., the length at which the correlation strength between two regions vanishes) as well as mutual information diverges with the cluster's size considered, such that arbitrarily large clusters exhibit the same collective dynamics than smaller ones. These three properties are known to be exclusive of complex systems exhibiting critical dynamics, where the spatio-temporal dynamics show these peculiar type of fluctuations. Thus, these findings are fully consistent with previous reports of brain critical dynamics, and are relevant for the interpretation of the role of fluctuations and variability in brain function in health and disease. PMID:22934058

  6. Development and Demonstration of Active Noise Control Concepts

    NASA Technical Reports Server (NTRS)

    Kraft, R.; Hu, Z.; Sommerfeldt, S.; Walker, B.; Hersh, A.; Luo, H.; Spencer, M.; Hallman, D.; Mitchell, C.; Sutliff, D.

    2000-01-01

    This report details design methods for and feasibility of an Active Noise Control (ANC) system using flush-wall-mounted sensors and actuators to reduce turbofan engine rotor-stator interaction noise. ANC concepts capable of suppressing discrete-tone spinning modes containing several cut-on radial mode were identified, developed analytically, and evaluated. Separate ANC systems that suppressed at least three radial modes in a cylindrical inlet duct and three radial modes in an exhaust annulus were developed. These designs resulted in inlet duct and exhaust duct tests that were performed at NASA on the 4-ft ANC Fan in the NASA Glenn AAPL facility. Effective suppression of 2-BPF spinning mode m = 2 tone noise was achieved over a range of fan speeds 1800 to 2450 rpm, where up to 4 radials were present. In the inlet duct, up to 12 dB reduction was obtained for 3 radial modes, and up to 4 dB was obtained with 4 radial modes. In the exhaust duct, up to 15 dB PWL reduction was obtained with either two or three radial modes present. Thus, the ability to suppress multiple radial modes for tones in both the inlet and exhaust ducts has been successfully demonstrated. Implications of ANC system design requirements on installation and system integration issues for ANC systems capable of suppressing higher order radial mode content when applied to a 767 using twin CF6 engines were evaluated analytically. The analytical results indicated an ANC system must be part of an integrated design to be effective.

  7. Active control of payload fairing noise using distributed active vibration absorbers

    NASA Astrophysics Data System (ADS)

    Charpentier, Arnaud; Johnson, Marty E.; Fuller, Chris R.

    2003-04-01

    High sound pressure inside a launch vehicle fairing during lift-off can damage the payload. Interior levels of up to 140 dB between 60 and 250 Hz are mostly due to exhaust plume noise combined with the limited transmission loss of lightweight composite fairings and little acoustic damping in the fairing volume. Past work using passive and hybrid passive/reactive noise control devices has shown that their limitations are mostly due to packaging volume and weight penalty. The objective of this work is to design a lightweight, compact, and low electrical power active noise control system to reduce the fairing interior sound level. Hybrid active/passive actuators such as Smart Foam (Couche and Fuller, Proceedings of Active 1999, Ft. Lauderdale, FL, pp. 609-620) and Distributed Active Vibration Absorbers (Marcotte, Fuller, and Johnson, Proceedings of Active 2002, ISVR, Southampton, England, pp. 535-546) are optimized for fairing noise control. The latter have been used to increase the transmission loss of the fairing. Active noise control test results on a sub-scale, sandwich composite fairing are presented. The global interior acoustic response due to airborne exterior excitation is minimized using an adaptive multiple-input, multiple-output feedforward controller. [Work supported by the Air Force Research Laboratory, Space Vehicles Directorate (AFRL).

  8. Noise as a tool for evaluating the activation of cathodes

    NASA Technical Reports Server (NTRS)

    Kosmahl, H.

    1978-01-01

    Measurements, at low frequencies, of the shot noise current from space charge limited cathodes always produced results substantially in excess of theoretical predictions. Measuring the ratio (I sub eq)/S yielded a relation (I sub eq)/S = 1.288 V sub k = 1.288 k(T sub k)/e, independent of the operating point of the diode (triode) as long as all parts of the cathode had a full space charge controlled emission. This method was so sensitive as to permit detection of cathode temperature changes by 1 K, thus it allowed a powerful screening method between well and poorly activated cathodes, superior to dip tests and other current-voltage methods.

  9. Relation between measures of speech-in-noise performance and measures of efferent activity

    NASA Astrophysics Data System (ADS)

    Smith, Brad; Harkrider, Ashley; Burchfield, Samuel; Nabelek, Anna

    2003-04-01

    Individual differences in auditory perceptual abilities in noise are well documented but the factors causing such variability are unclear. The purpose of this study was to determine if individual differences in responses measured from the auditory efferent system were correlated to individual variations in speech-in-noise performance. The relation between behavioral performance on three speech-in-noise tasks and two objective measures of the efferent auditory system were examined in thirty normal-hearing, young adults. Two of the speech-in-noise tasks measured an acceptable noise level, the maximum level of speech-babble noise that a subject is willing to accept while listening to a story. For these, the acceptable noise level was evaluated using both an ipsilateral (story and noise in same ear) and a contralateral (story and noise in opposite ears) paradigm. The third speech-in-noise task evaluated speech recognition using monosyllabic words presented in competing speech babble. Auditory efferent activity was assessed by examining the resulting suppression of click-evoked otoacoustic emissions following the introduction of a contralateral, broad-band stimulus and the activity of the ipsilateral and contralateral acoustic reflex arc was evaluated using tones and broad-band noise. Results will be discussed relative to current theories of speech in noise performance and auditory inhibitory processes.

  10. Magnetic Flux Cancellation and Formation of Prominence

    NASA Astrophysics Data System (ADS)

    Miley, George; Kim, Mun Song; Chon Nam, Sok; Kim, Kyong Chol

    2015-08-01

    Magnetic flux cancellation appears to be closely related to various kinds of solar activities such as flares, microflares/surges/jets, X-ray bright points, erupting mini-filaments, transition region explosive events, filament formation, filament activation and eruption, and coronal mass ejections. It is commonly believed that magnetic reconnections in the low atmosphere are responsible for canceling magnetic features, and magnetic fragments are observed to originate as bipoles. According to the Sweet-Parker type reconnection model, the inflow speed closely corresponds to the converging speed of each pole in a canceling magnetic feature and the rate of flux cancellation must be explained by the observed converging speed. As distinct from the corona, the efficiency of photospheric magnetic reconnection may be due to the small Cowling conductivity, instead of the Spitzer, of weakly ionized and magnetized plasma in the low atmosphere of the sun. Using the VAL-C atmospheric model and Cowling conductivity, we have computed the parameters describing Sweet-Parker type reconnecting current sheets in the plasma of the solar photosphere and chromosphere, and particularly for the phenomena of magnetic flux cancellation and dark filament formation which occurred on July 2, 1994 we have estimated the rate of flux cancellation, the inflow speed(the converging speed) and the upward mass flux to compare with the observation. The results show that when taking account of the Cowling conductivity in the low atmosphere, large flux cancellation rates(>1019Mxhr-1) in solar active regions are better explained than by the Spitzer conductivity-considered reconnection model. Particularly for the flux cancellation event on July 2, 1994, the inflow speed(0.26kms-1)is almost similar to the converging speed(0.22kms-1)and the upward mass flux(3.3X1012gs-1) in the model is sufficient for the large dark filament formation in a time of several hours through magnetic flux cancellation process.

  11. Effect of unpleasant loud noise on hippocampal activities during picture encoding: an fMRI study.

    PubMed

    Hirano, Yoshiyuki; Fujita, Masafumi; Watanabe, Kazuko; Niwa, Masami; Takahashi, Toru; Kanematsu, Masayuki; Ido, Yasushi; Tomida, Mihoko; Onozuka, Minoru

    2006-08-01

    The functional link between the amygdala and hippocampus in humans has not been well documented. We examined the effect of unpleasant loud noise on hippocampal and amygdaloid activities during picture encoding by means of fMRI, and on the correct response in humans. The noise reduced activity in the hippocampus during picture encoding, decreased the correct response and increased the activity of the amygdala. A path diagram using structural equation modeling suggested that hippocampus activity might be depressed by high amygdala activity. Therefore, noise should diminish memory by reducing hippocampal activity, which might be depressed by high amygdala activity.

  12. Comparison of speech intelligibility in cockpit noise using SPH-4 flight helmet with and without active noise reduction

    NASA Technical Reports Server (NTRS)

    Chan, Jeffrey W.; Simpson, Carol A.

    1990-01-01

    Active Noise Reduction (ANR) is a new technology which can reduce the level of aircraft cockpit noise that reaches the pilot's ear while simultaneously improving the signal to noise ratio for voice communications and other information bearing sound signals in the cockpit. A miniature, ear-cup mounted ANR system was tested to determine whether speech intelligibility is better for helicopter pilots using ANR compared to a control condition of ANR turned off. Two signal to noise ratios (S/N), representative of actual cockpit conditions, were used for the ratio of the speech to cockpit noise sound pressure levels. Speech intelligibility was significantly better with ANR compared to no ANR for both S/N conditions. Variability of speech intelligibility among pilots was also significantly less with ANR. When the stock helmet was used with ANR turned off, the average PB Word speech intelligibility score was below the Normally Acceptable level. In comparison, it was above that level with ANR on in both S/N levels.

  13. Active control of fan noise from a turbofan engine

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H.; Burdisso, Ricardo A.; Fuller, Christopher R.; O'Brien, Walter F.

    1994-01-01

    A three-channel active control system is applied to an operational turbofan engine to reduce tonal noise produced by both the fan and the high-pressure compressor. The control approach is the feedforward filtered-x least-mean-square algorithm implemented on a digital signal processing board. Reference transducers mounted on the engine case provide blade passing and harmonics frequency information to the controller. Error information is provided by large area microphones placed in the acoustic far field. To minimize the error signal, the controller actuates loudspeakers mounted on the inlet to produce destructive interference. The sound pressure level of the fundamental tone of the fan was reduced using the three-channel controller by up to 16 dB over a +/- 30-deg angle about the engine axis. A single-channel controller could produce reduction over a +/- 15-deg angle. The experimental results show the control to be robust. Outside of the areas contolled, the levels of the tone actually increased due to the generation of radial modes by the control sources. Simultaneous control of two tones is achieved with parallel controllers. The fundamental and the first harmonic tones of the fan were controlled simultaneously with reductions of 12 and 5 dBA, respectively, measured on the engine axis. Simultaneous control was also demonstrated for the fan fundamental and the high-pressure compressor fundamental tones.

  14. Active control of fan noise from a turbofan engine

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H.; Burdisso, Ricardo A.; Fuller, Christopher R.; O'Brien, Walter F.

    1993-01-01

    A three channel active control system is applied to an operational turbofan engine in order to reduce tonal noise produced by both the fan and high pressure compressor. The control approach is the feedforward filtered-x least-mean-square algorithm implemented on a digital signal processing board. Reference transducers mounted on the engine case provides blade passing and harmonics frequency information to the controller. Error information is provided by large area microphones placed in the acoustic far field. In order to minimize the error signal, the controller actuates loudspeakers mounted on the inlet to produce destructive interference. The sound pressure level of the fundamental tone of the fan was reduced using the three channel controller by up to 16 dB over a 60 deg angle about the engine axis. A single channel controller could produce reduction over a 30 deg angle. The experimental results show the control to be robust. Simultaneous control of two tones is done with parallel controllers. The fundamental and the first harmonic tones of the fan were controlled simultaneously with reductions of 12 dBA and 5 dBA, respectively, measured on the engine axis. Simultaneous control was also demonstrated for the fan fundamental and the high pressure compressor fundamental tones.

  15. Multi-channel Kalman filters for active noise control.

    PubMed

    van Ophem, S; Berkhoff, A P

    2013-04-01

    By formulating the feed-forward broadband active noise control problem as a state estimation problem it is possible to achieve a faster rate of convergence than the filtered reference least mean squares algorithm and possibly also a better tracking performance. A multiple input/multiple output Kalman algorithm is derived to perform this state estimation. To make the algorithm more suitable for real-time applications, the Kalman filter is written in a fast array form and the secondary path state matrices are implemented in output normal form. The resulting filter implementation is tested in simulations and in real-time experiments. It was found that for a constant primary path the filter has a fast rate of convergence and is able to track changes in the frequency spectrum. For a forgetting factor equal to unity the system is robust but the filter is unable to track rapid changes in the primary path. A forgetting factor lower than 1 gives a significantly improved tracking performance but leads to a numerical instability for the fast array form of the algorithm. PMID:23556580

  16. Effect of Unpleasant Loud Noise on Hippocampal Activities during Picture Encoding: An fMRI Study

    ERIC Educational Resources Information Center

    Hirano, Yoshiyuki; Fujita, Masafumi; Watanabe, Kazuko; Niwa, Masami; Takahashi, Toru; Kanematsu, Masayuki; Ido, Yasushi; Tomida, Mihoko; Onozuka, Minoru

    2006-01-01

    The functional link between the amygdala and hippocampus in humans has not been well documented. We examined the effect of unpleasant loud noise on hippocampal and amygdaloid activities during picture encoding by means of fMRI, and on the correct response in humans. The noise reduced activity in the hippocampus during picture encoding, decreased…

  17. Noise in brain activity engenders perception and influences discrimination sensitivity.

    PubMed

    Bernasconi, Fosco; De Lucia, Marzia; Tzovara, Athina; Manuel, Aurelie L; Murray, Micah M; Spierer, Lucas

    2011-12-01

    Behavioral and brain responses to identical stimuli can vary with experimental and task parameters, including the context of stimulus presentation or attention. More surprisingly, computational models suggest that noise-related random fluctuations in brain responses to stimuli would alone be sufficient to engender perceptual differences between physically identical stimuli. In two experiments combining psychophysics and EEG in healthy humans, we investigated brain mechanisms whereby identical stimuli are (erroneously) perceived as different (higher vs lower in pitch or longer vs shorter in duration) in the absence of any change in the experimental context. Even though, as expected, participants' percepts to identical stimuli varied randomly, a classification algorithm based on a mixture of Gaussians model (GMM) showed that there was sufficient information in single-trial EEG to reliably predict participants' judgments of the stimulus dimension. By contrasting electrical neuroimaging analyses of auditory evoked potentials (AEPs) to the identical stimuli as a function of participants' percepts, we identified the precise timing and neural correlates (strength vs topographic modulations) as well as intracranial sources of these erroneous perceptions. In both experiments, AEP differences first occurred ~100 ms after stimulus onset and were the result of topographic modulations following from changes in the configuration of active brain networks. Source estimations localized the origin of variations in perceived pitch of identical stimuli within right temporal and left frontal areas and of variations in perceived duration within right temporoparietal areas. We discuss our results in terms of providing neurophysiologic evidence for the contribution of random fluctuations in brain activity to conscious perception.

  18. Active-passive gradient shielding for MRI acoustic noise reduction.

    PubMed

    Edelstein, William A; Kidane, Tesfaye K; Taracila, Victor; Baig, Tanvir N; Eagan, Timothy P; Cheng, Yu-Chung N; Brown, Robert W; Mallick, John A

    2005-05-01

    An important source of MRI acoustic noise-magnet cryostat warm-bore vibrations caused by eddy-current-induced forces-can be mitigated by a passive metal shield mounted on the outside of a vibration-isolated, vacuum-enclosed shielded gradient set. Finite-element (FE) calculations for a z-gradient indicate that a 2-mm-thick Cu layer wrapped on the gradient assembly can decrease mechanical power deposition in the warm bore and reduce warm-bore acoustic noise production by about 25 dB. Eliminating the conducting warm bore and other magnet parts as significant acoustic noise sources could lead to the development of truly quiet, fully functioning MRI systems with noise levels below 70 dB.

  19. Tuning active Brownian motion with shot-noise energy pulses

    NASA Astrophysics Data System (ADS)

    Fiasconaro, Alessandro; Gudowska-Nowak, Ewa; Ebeling, Werner

    2009-01-01

    The main aim of this work is to explore the possibility of modeling the biological energy support mediated by absorption of ATP (adenosine triphosphate) as an energetic shot noise. We develop a general model with discrete input of energy pulses and study shot-noise-driven ratchets. We consider these ratchets as prototypes of Brownian motors driven by energy-rich ATP molecules. Our model is a stochastic machine able to acquire energy from the environment and convert it into kinetic energy of motion. We present characteristic features and demonstrate the possibility of tuning these motors by adapting the mean frequency of the discrete energy inputs, which are described as a special shot noise. In particular, the effect of stochastically driven directionality and uphill flux in systems acquiring energy from the shot noise is analyzed. As a possible application we consider the motion of kinesin on a microtubule under a constant load force.

  20. Noise-enhanced stability and double stochastic resonance of active Brownian motion

    NASA Astrophysics Data System (ADS)

    Zeng, Chunhua; Zhang, Chun; Zeng, Jiakui; Liu, Ruifen; Wang, Hua

    2015-08-01

    In this paper, we study the transient and resonant properties of active Brownian particles (ABPs) in the Rayleigh-Helmholtz (RH) and Schweitzer-Ebeling-Tilch (SET) models, which is driven by the simultaneous action of multiplicative and additive noise and periodic forcing. It is shown that the cross-correlation between two noises (λ) can break the symmetry of the potential to generate motion of the ABPs. In case of no correlation between two noises, the mean first passage time (MFPT) is a monotonic decrease depending on the multiplicative noise, however in case of correlation between two noises, the MFPT exhibits a maximum, depending on the multiplicative noise for both models, this maximum for MFPT identifies the noise-enhanced stability (NES) effect of the ABPs. By comparing with case of no correlation (λ =0.0 ), we find two maxima in the signal-to-noise ratio (SNR) depending on the cross-correlation intensity, i.e. the double stochastic resonance is shown in both models. For the RH model, the SNR exhibits two maxima depending on the multiplicative noise for small cross-correlation intensity, while in the SET model, it exhibits only a maximum depending on the multiplicative noise. Whether λ =0.0 or not, the MFPT is a monotonic decrease, and the SNR exhibits a maximum, depending on the additive noise in both models.

  1. Reduction of Helicopter Blade-Vortex Interaction Noise by Active Rotor Control Technology

    NASA Technical Reports Server (NTRS)

    Yu, Yung H.; Gmelin, Bernd; Splettstoesser, Wolf; Brooks, Thomas F.; Philippe, Jean J.; Prieur, Jean

    1997-01-01

    Helicopter blade-vortex interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor blade-vortex interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently available for rotor blade vortex interaction noise reduction, including higher harmonic pitch control, individual blade control, and on-blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations, Published by Elsevier Science Ltd.

  2. Method and System for Active Noise Control of Tiltrotor Aircraft

    NASA Technical Reports Server (NTRS)

    Betzina, Mark D. (Inventor); Nguyen, Khanh Q. (Inventor)

    2003-01-01

    Methods and systems for reducing noise generated by rotating blades of a tiltrotor aircraft. A rotor-blade pitch angle associated with the tiltrotor aircraft can be controlled utilizing a swashplate connected to rotating blades of the tiltrotor aircraft. One or more Higher Harmonic Control (HHC) signals can be transmitted and input to a swashplate control actuator associated with the swashplate. A particular blade pitch oscillation (e.g., four cycles per revolution) is there-after produced in a rotating frame of reference associated with the rotating blades in response to input of an HHC signal to the swashplate control actuator associated with the swashplate to thereby reduce noise associated with the rotating blades of the tiltrotor aircraft. The HHC signal can be transmitted and input to the swashplate control actuator to reduce noise of the tiltrotor aircraft in response to a user input utilizing an open-loop configuration.

  3. Behavioral evaluation of movement cancellation.

    PubMed

    Walton, Mark M G; Gandhi, Neeraj J

    2006-10-01

    The countermanding saccade task has been used in many studies to investigate the neural mechanisms that underlie the decision to execute or restrain rapid eye movements. In this task, the presentation of a saccade target is sometimes followed by the appearance of a stop cue that indicates that the subject should cancel the planned movement. Performance has been modeled as a race between motor preparation and cancellation processes. The signal that reaches its activation threshold first determines whether a saccade is generated or cancelled. In these studies, an important parameter is the time required to process the stop cue, referred to as the stop signal reaction time (SSRT). The SSRT is estimated using statistical approaches, the validity of which has not been unequivocally established. A more direct measure of this parameter might be obtainable if a method was available to "unmask" the developing motor command. This can be accomplished by air-puff-evoked blinks, which inhibit pontine omnipause neurons that serve as an inhibitory gate for the saccadic system. In the present study, brief puffs of air were used to elicit blinks at various times while rhesus monkeys performed a countermanding saccade task. If the developing motor command has not yet been cancelled, this should trigger a saccade. When blinks occurred between approximately 50 and 200 ms after target onset, saccades were often evoked. Saccades were rarely evoked more than approximately 70 ms after stop cue onset; this value represents a behavioral evaluation of SSRT and was comparable to the estimates obtained using standard statistical approaches. When saccades occurred near the SSRT on blink trials, they were often hypometric. Furthermore, Monte Carlo simulations were performed to model the effects of blink time on the race model. Overall, the study supports the validity of the statistical methods currently in use. PMID:16760340

  4. Simulation Study on Active Noise Control for a 4 Tesla MRI Scanner

    PubMed Central

    Li, Mingfeng; Lim, Teik C.; Lee, Jing-Huei

    2008-01-01

    The purpose of this work is to study computationally the possibility of the application of a hybrid active noise control technique for MRI acoustic noise reduction. A hybrid control system combined with both feedforward and feedback loops embedded is proposed for potential application on active MRI noise reduction. A set of computational simulation studies were performed. Sets of MRI acoustic noise emissions measured at the patient's left ear location were recorded and used in the simulation study. By comparing three different control systems, namely the feedback, the feedforward and the hybrid control, our results revealed that the hybrid control system is the most effective. The hybrid control system achieved approximately a 20 dB reduction at the principal frequency component. We concluded that the proposed hybrid active control scheme could have a potential application for MRI scanner noise reduction. PMID:18060719

  5. Simulation study on active noise control for a 4-T MRI scanner.

    PubMed

    Li, Mingfeng; Lim, Teik C; Lee, Jing-Huei

    2008-04-01

    The purpose of this work is to study computationally the possibility of the application of a hybrid active noise control technique for magnetic resonance imaging (MRI) acoustic noise reduction. A hybrid control system combined with both feedforward and feedback loops embedded is proposed for potential application on active MRI noise reduction. A set of computational simulation studies were performed. Sets of MRI acoustic noise emissions measured at the patient's left ear location were recorded and used in the simulation study. By comparing three different control systems, namely, the feedback, the feedforward and the hybrid control, our results revealed that the hybrid control system is the most effective. The hybrid control system achieved approximately a 20-dB reduction at the principal frequency component. We concluded that the proposed hybrid active control scheme could have a potential application for MRI scanner noise reduction.

  6. The spatial structure of underwater noise due to shipping activities in the Celtic Sea

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Shapiro, Georgy; Thain, Richard

    2014-05-01

    Underwater noise is now classed as pollution alongside chemical pollution and marine litter (MSFD, 2012). Underwater noise from man-made sources arises from a number of sources including shipping activities. There are numerous examples of sound-induced effects recorded for various marine mammals, either in controlled situations, or opportunistically (MSFD-GES, 2012). Broad or narrow band continuous sounds, as well as pulses, have been documented to cause effects ranging from slight behaviour change, to activity disruption, avoidance or abandonment of preferred habitat (see Clark et al., 2009). Underwater ambient noise generated by shipping activities has increased significantly over the past decades (e.g. Mcdonald et al., 2006). Noise from shipping is a major contributor to the ambient noise levels in ocean, particularly at low (

  7. Environmental noise levels affect the activity budget of the Florida manatee

    NASA Astrophysics Data System (ADS)

    Miksis-Olds, Jennifer L.; Donaghay, Percy L.; Miller, James H.; Tyack, Peter L.

    2005-09-01

    Manatees inhabit coastal bays, lagoons, and estuaries because they are dependent on the aquatic vegetation that grows in shallow waters. Food requirements force manatees to occupy the same areas in which human activities are the greatest. Noise produced from human activities has the potential to affect these animals by eliciting responses ranging from mild behavioral changes to extreme aversion. This study quantifies the behavioral responses of manatees to both changing levels of ambient noise and transient noise sources. Results indicate that elevated environmental noise levels do affect the overall activity budget of this species. The proportion of time manatees spend feeding, milling, and traveling in critical habitats changed as a function of noise level. More time was spent in the directed, goal-oriented behaviors of feeding and traveling, while less time was spent milling when noise levels were highest. The animals also responded to the transient noise of approaching vessels with changes in behavioral state and movements out of the geographical area. This suggests that manatees detect and respond to changes in environmental noise levels. Whether these changes legally constitute harassment and produce biologically significant effects need to be addressed with hypothesis-driven experiments and long-term monitoring. [For Animal Bioacoustics Best Student Paper Award.

  8. A Review on Successive Interference Cancellation Scheme Based on Optical CDMA Network

    NASA Astrophysics Data System (ADS)

    Alsowaidi, N.; Eltaif, T.; Mokhtar, M. R.

    2014-12-01

    Due to various desirable features of optical code division multiple access (OCDMA), it is believed this technique once developed and commercially available will be an integral part of optical access networks. Optical CDMA system suffers from a problem called multiple access interference (MAI) which limits the number of active users, it occurs when number of active users share the same carriers. The aim of this paper is to review successive interference cancellation (SIC) scheme based on optical CDMA system. The paper also reviews the system performance in presence of shot noise, thermal noise, and phase-induced intensity noise (PIIN). A comprehensive review on the mathematical model of SIC scheme using direct detection (DS) and spectral amplitude coding (SAC) were presented in this article.

  9. INVITED PAPER: Application of an active device for helicopter noise reduction in JAXA

    NASA Astrophysics Data System (ADS)

    Saito, Shigeru; Kobiki, Noboru; Tanabe, Yasutada

    2010-02-01

    Important issues in noise problems for current helicopters are described. An active tab (AT) was developed as a new active device for noise/vibration reduction under research cooperation between Japan Aerospace Exploration Agency (JAXA) and Kawada Industries, Inc. The wind tunnel test was conducted in order to investigate the effectiveness of the AT on the aeroacoustic characteristics of a helicopter. From the wind tunnel test, the capability of reducing blade vortex interaction (BVI) noise by an AT was verified. A new control law using instantaneous pressure change on a blade during BVI phenomena was introduced and applied to the wind tunnel testing. This new control law shows reasonable controllability for helicopter noise reduction. Furthermore, in order to analyze noise characteristics, the advanced computational fluid dynamics (CFD) code named JAXA_ov3d was developed in JAXA and extended to include CFD-CSD (computational structure dynamics) coupling by using the beam theory for blade deformation.

  10. Adaptive cancellation techniques

    NASA Astrophysics Data System (ADS)

    1983-11-01

    An adaptive signal canceller has been evaluated for the enhancement of pulse signal reception during the transmission of a high power ECM jamming signal. The canceller design is based on the use of DRFM(Digital RF Memory) technology as part of an adaptive multiple tapped delay line. The study includes analysis of relationship of tap spacing and waveform bandwidth, survey of related documents in areas of sidelobe cancellers, transversal equalizers, and adaptive filters, and derivation of control equations and corresponding control processes. The simulation of overall processes included geometric analysis of the multibeam transmitting antenna, multiple reflection sources and the receiving antenna; waveforms, tap spacings and bandwidths; and alternate control algorithms. Conclusions are provided regarding practical system control algorithms, design characteristics and limitations.

  11. Ambient noise and temporal patterns of boat activity in the US Virgin Islands National Park.

    PubMed

    Kaplan, Maxwell B; Mooney, T Aran

    2015-09-15

    Human activity is contributing increasing noise to marine ecosystems. Recent studies have examined the effects of boat noise on marine fishes, but there is limited understanding of the prevalence of this type of sound source. This investigation tracks vessel noise on three reefs in the US Virgin Islands National Park over four months in 2013. Ambient noise levels ranged from 106 to 129dBrms re 1μPa (100Hz-20kHz). Boat noise occurred in 6-12% of samples. In the presence of boat noise, ambient noise in a low-frequency band (100-1000Hz) increased by >7dB above baseline levels and sound levels were significantly higher. The frequency with the most acoustic energy shifted to a significantly lower frequency when boat noise was present during the day. These results indicate the abundance of boat noise and its overlap with reef organism sound production, raising concern for the communication abilities of these animals.

  12. The Effect of Human Activities and Their Associated Noise on Ungulate Behavior

    PubMed Central

    Brown, Casey L.; Hardy, Amanda R.; Barber, Jesse R.; Fristrup, Kurt M.; Crooks, Kevin R.; Angeloni, Lisa M.

    2012-01-01

    Background The effect of anthropogenic noise on terrestrial wildlife is a relatively new area of study with broad ranging management implications. Noise has been identified as a disturbance that has the potential to induce behavioral responses in animals similar to those associated with predation risk. This study investigated potential impacts of a variety of human activities and their associated noise on the behavior of elk (Cervus elaphus) and pronghorn (Antilocapra americana) along a transportation corridor in Grand Teton National Park. Methodology/Principal Findings We conducted roadside scan surveys and focal observations of ungulate behavior while concurrently recording human activity and anthropogenic noise. Although we expected ungulates to be more responsive with greater human activity and noise, as predicted by the risk disturbance hypothesis, they were actually less responsive (less likely to perform vigilant, flight, traveling and defensive behaviors) with increasing levels of vehicle traffic, the human activity most closely associated with noise. Noise levels themselves had relatively little effect on ungulate behavior, although there was a weak negative relationship between noise and responsiveness in our scan samples. In contrast, ungulates did increase their responsiveness with other forms of anthropogenic disturbance; they reacted to the presence of pedestrians (in our scan samples) and to passing motorcycles (in our focal observations). Conclusions These findings suggest that ungulates did not consistently associate noise and human activity with an increase in predation risk or that they could not afford to maintain responsiveness to the most frequent human stimuli. Although reduced responsiveness to certain disturbances may allow for greater investment in fitness-enhancing activities, it may also decrease detections of predators and other environmental cues and increase conflict with humans. PMID:22808175

  13. Temporal pattern of acoustic imaging noise asymmetrically modulates activation in the auditory cortex.

    PubMed

    Ranaweera, Ruwan D; Kwon, Minseok; Hu, Shuowen; Tamer, Gregory G; Luh, Wen-Ming; Talavage, Thomas M

    2016-01-01

    This study investigated the hemisphere-specific effects of the temporal pattern of imaging related acoustic noise on auditory cortex activation. Hemodynamic responses (HDRs) to five temporal patterns of imaging noise corresponding to noise generated by unique combinations of imaging volume and effective repetition time (TR), were obtained using a stroboscopic event-related paradigm with extra-long (≥27.5 s) TR to minimize inter-acquisition effects. In addition to confirmation that fMRI responses in auditory cortex do not behave in a linear manner, temporal patterns of imaging noise were found to modulate both the shape and spatial extent of hemodynamic responses, with classically non-auditory areas exhibiting responses to longer duration noise conditions. Hemispheric analysis revealed the right primary auditory cortex to be more sensitive than the left to the presence of imaging related acoustic noise. Right primary auditory cortex responses were significantly larger during all the conditions. This asymmetry of response to imaging related acoustic noise could lead to different baseline activation levels during acquisition schemes using short TR, inducing an observed asymmetry in the responses to an intended acoustic stimulus through limitations of dynamic range, rather than due to differences in neuronal processing of the stimulus. These results emphasize the importance of accounting for the temporal pattern of the acoustic noise when comparing findings across different fMRI studies, especially those involving acoustic stimulation.

  14. Temporal pattern of acoustic imaging noise asymmetrically modulates activation in the auditory cortex.

    PubMed

    Ranaweera, Ruwan D; Kwon, Minseok; Hu, Shuowen; Tamer, Gregory G; Luh, Wen-Ming; Talavage, Thomas M

    2016-01-01

    This study investigated the hemisphere-specific effects of the temporal pattern of imaging related acoustic noise on auditory cortex activation. Hemodynamic responses (HDRs) to five temporal patterns of imaging noise corresponding to noise generated by unique combinations of imaging volume and effective repetition time (TR), were obtained using a stroboscopic event-related paradigm with extra-long (≥27.5 s) TR to minimize inter-acquisition effects. In addition to confirmation that fMRI responses in auditory cortex do not behave in a linear manner, temporal patterns of imaging noise were found to modulate both the shape and spatial extent of hemodynamic responses, with classically non-auditory areas exhibiting responses to longer duration noise conditions. Hemispheric analysis revealed the right primary auditory cortex to be more sensitive than the left to the presence of imaging related acoustic noise. Right primary auditory cortex responses were significantly larger during all the conditions. This asymmetry of response to imaging related acoustic noise could lead to different baseline activation levels during acquisition schemes using short TR, inducing an observed asymmetry in the responses to an intended acoustic stimulus through limitations of dynamic range, rather than due to differences in neuronal processing of the stimulus. These results emphasize the importance of accounting for the temporal pattern of the acoustic noise when comparing findings across different fMRI studies, especially those involving acoustic stimulation. PMID:26519093

  15. Erratum to "Noise-induced changes of neuronal spontaneous activity in mice inferior colliculus brain slices".

    PubMed

    Basta, Dietmar; Ernst, Arne

    2005-02-01

    The inferior colliculus (IC) in vivo is reportedly subject to a noise-induced decrease of GABA-related inhibitory synaptic transmission accompanied by an amplitude increase of auditory evoked responses, a widening of tuning curves and a higher neuronal discharge rate at suprathreshold levels. However, other in vivo experiments which demonstrated constant neuronal auditory thresholds or unchanged spontaneous activity in the IC after noise exposure did not confirm those findings. Perhaps this can be the result of complex noise-induced interactions between different central auditory structures. It was, therefore, the aim of the present study to investigate the effects of noise exposure on the spontaneous electrical activity of single neurons in a slice preparation of the isolated mouse IC. Normal hearing mice were exposed to noise (10 kHz center frequency at 115 dB SPL for 3 h) at the age of 21 days under anesthesia (Ketamin/Rompun 10:1). After one week, auditory brainstem response (ABR) recordings and extracellular single-unit recordings from spontaneously active neurons within the IC slice were performed in noise-exposed and in normal hearing control mice. Noise-exposed animals showed a significant ABR threshold shift in the whole tested frequency range and a significant lower neuronal spontaneous activity in all investigated isofrequency laminae compared to controls. In both groups, the firing rate of 80% of IC neurons (approximately) increased significantly during the application of the GABA(A) receptor antagonist Bicucullin (10 microM). The present findings demonstrate a noise-related modulation of spontaneous activity in the IC, which possibly contribute to the generation of noise-induced tinnitus and hearing loss.

  16. Noise-induced changes of neuronal spontaneous activity in mice inferior colliculus brain slices.

    PubMed

    Basta, Dietmar; Ernest, Arne

    2004-09-30

    The inferior colliculus (IC) in vivo is reportedly subject to a noise-induced decrease of GABA-related inhibitory synaptic transmission accompanied by an amplitude increase of auditory evoked responses, a widening of tuning curves and a higher neuronal discharge rate at suprathreshold levels. However, other in vivo experiments which demonstrated constant neuronal auditory thresholds or unchanged spontaneous activity in the IC after noise exposure did not confirm those findings. Perhaps this can be the result of complex noise-induced interactions between different central auditory structures. It was, therefore, the aim of the present study to investigate the effects of noise exposure on the spontaneous electrical activity of single neurons in a slice preparation of the isolated mouse IC. Normal hearing mice were exposed to noise (10 kHz center frequency at 115 dB SPL for 3 h) at the age of 21 days under anesthesia (Ketamin/Rompun 10:1). After one week, auditory brainstem response (ABR) recordings and extracellular single-unit recordings from spontaneously active neurons within the IC slice were performed in noise-exposed and in normal hearing control mice. Noise-exposed animals showed a significant ABR threshold shift in the whole tested frequency range and a significant lower neuronal spontaneous activity in all investigated isofrequency laminae compared to controls. In both groups, the firing rate of 80% of IC neurons (approximately) increased significantly during the application of the GABA(A) receptor antagonist Bicucullin (10 microM). The present findings demonstrate a noise-related modulation of spontaneous activity in the IC, which possibly contribute to the generation of noise-induced tinnitus and hearing loss.

  17. Active Control of Automotive Intake Noise under Rapid Acceleration using the Co-FXLMS Algorithm

    NASA Astrophysics Data System (ADS)

    Lee, Hae-Jin; Lee, Gyeong-Tae; Oh, Jae-Eung

    The method of reducing automotive intake noise can be classified by passive and active control techniques. However, passive control has a limited effect of noise reduction at low frequency range (below 500 Hz) and is limited by the space of the engine room. However, active control can overcome these passive control limitations. The active control technique mostly uses the Least-Mean-Square (LMS) algorithm, because the LMS algorithm can easily obtain the complex transfer function in real-time, particularly when the Filtered-X LMS (FXLMS) algorithm is applied to an active noise control (ANC) system. However, the convergence performance of the LMS algorithm decreases significantly when the FXLMS algorithm is applied to the active control of intake noise under rapidly accelerating driving conditions. Therefore, in this study, the Co-FXLMS algorithm was proposed to improve the control performance of the FXLMS algorithm during rapid acceleration. The Co-FXLMS algorithm is realized by using an estimate of the cross correlation between the adaptation error and the filtered input signal to control the step size. The performance of the Co-FXLMS algorithm is presented in comparison with that of the FXLMS algorithm. Experimental results show that active noise control using Co-FXLMS is effective in reducing automotive intake noise during rapid acceleration.

  18. Effects of secondary loudspeaker properties on broadband feedforward active duct noise control.

    PubMed

    Chan, Yum-Ji; Huang, Lixi; Lam, James

    2013-07-01

    Dependence of the performance of feedforward active duct noise control on secondary loudspeaker parameters is investigated. Noise reduction performance can be improved if the force factor of the secondary loudspeaker is higher. For example, broadband noise reduction improvement up to 1.6 dB is predicted by increasing the force factor by 50%. In addition, a secondary loudspeaker with a larger force factor was found to have quicker convergence in the adaptive algorithm in experiment. In simulations, noise reduction is improved in using an adaptive algorithm by using a secondary loudspeaker with a heavier moving mass. It is predicted that an extra broadband noise reduction of more than 7 dB can be gained using an adaptive filter if the force factor, moving mass and coil inductance of a commercially available loudspeaker are doubled. Methods to increase the force factor beyond those of commercially available loudspeakers are proposed.

  19. A hybrid active/passive exhaust noise control system for locomotives

    NASA Astrophysics Data System (ADS)

    Remington, Paul J.; Knight, J. Scott; Hanna, Doug; Rowley, Craig

    2005-01-01

    A prototype hybrid system consisting of active and passive components for controlling far-field locomotive exhaust noise has been designed, assembled, and tested on a locomotive. The system consisted of a resistive passive silencer for controlling high-frequency broadband noise and a feedforward multiple-input, multiple-output active control system for suppressing low-frequency tonal noise. The active system used ten roof-mounted bandpass speaker enclosures with 2-12-in. speakers per enclosure as actuators, eight roof-mounted electret microphones as residual sensors, and an optical tachometer that sensed locomotive engine speed as a reference sensor. The system was installed on a passenger locomotive and tested in an operating rail yard. Details of the system are described and the near-field and far-field noise reductions are compared against the design goal. .

  20. A hybrid active/passive exhaust noise control system for locomotives.

    PubMed

    Remington, Paul J; Knight, J Scott; Hanna, Doug; Rowley, Craig

    2005-01-01

    A prototype hybrid system consisting of active and passive components for controlling far-field locomotive exhaust noise has been designed, assembled, and tested on a locomotive. The system consisted of a resistive passive silencer for controlling high-frequency broadband noise and a feedforward multiple-input, multiple-output active control system for suppressing low-frequency tonal noise. The active system used ten roof-mounted bandpass speaker enclosures with 2-12-in. speakers per enclosure as actuators, eight roof-mounted electret microphones as residual sensors, and an optical tachometer that sensed locomotive engine speed as a reference sensor. The system was installed on a passenger locomotive and tested in an operating rail yard. Details of the system are described and the near-field and far-field noise reductions are compared against the design goal.

  1. A hybrid active/passive exhaust noise control system for locomotives.

    PubMed

    Remington, Paul J; Knight, J Scott; Hanna, Doug; Rowley, Craig

    2005-01-01

    A prototype hybrid system consisting of active and passive components for controlling far-field locomotive exhaust noise has been designed, assembled, and tested on a locomotive. The system consisted of a resistive passive silencer for controlling high-frequency broadband noise and a feedforward multiple-input, multiple-output active control system for suppressing low-frequency tonal noise. The active system used ten roof-mounted bandpass speaker enclosures with 2-12-in. speakers per enclosure as actuators, eight roof-mounted electret microphones as residual sensors, and an optical tachometer that sensed locomotive engine speed as a reference sensor. The system was installed on a passenger locomotive and tested in an operating rail yard. Details of the system are described and the near-field and far-field noise reductions are compared against the design goal. PMID:15704399

  2. Inertia Wheel on Low-Noise Active Magnetic Suspension

    NASA Astrophysics Data System (ADS)

    Carabelli, S.; Genta, G.; Silvagni, M.; Tonoli, A.

    2002-01-01

    Magnetic bearings are particularly suited for space applications for a number of reasons: - they are ideally suited for vacuum applications; - the lack of lubrication and wear enhances the reliability and guaranties a long maintenance-free operation - the low drag torque decreases power consumption and reduces the torque exerted on the stator of the machine. - the possibility of insulating actively the spacecraft from the excitation due to unbalance of the rotating system In the case of reaction wheels, a well designed magnetic suspension allows high speed operation with a very low power consumption and vibration level. Conversely, microgravity (and possibly vacuum) operation is an advantage for magnetic bearings. The absence of static forces allows to operate with low current levels, thus reducing electrical noise and allowing to reach even lower vibration levels than in Earth applications of magnetic bearings. Active magnetic bearings (AMB) allow to adapt the working characteristics of the system to the operating needs: it is possible to use the actuators to lock the system during launch (absence of grabbers) and to stiffen the suspension when the spacecraft is accelerated (impulsive phases), while working in conditions optimised for microgravity when this is needed. Magnetic suspension systems designed for microgravity environment cannot be correctly tested on the ground. Testing in ground conditions results in the need of grossly overdesigning the levitation device; furthermore, in some cases ground testing is completely impossible, if not by introducing devices which compensate for the Earth gravitational field. If the compensation for the gravitational force is supplied by the same actuators used for microgravity operation, the actuators and the power amplifiers must be overdesigned and in some cases the suspension can be altogether impossible. They work in conditions which are much different from nominal ones and, above all, it is impossible to reach the

  3. Active control of wake/blade-row interaction noise through the use of blade surface actuators

    NASA Technical Reports Server (NTRS)

    Kousen, Kenneth A.; Verdon, Joseph M.

    1993-01-01

    A combined analytical/computational approach for controlling of the noise generated by wake/blade-row interaction through the use of anti-sound actuators on the blade surfaces is described. A representative two-dimensional section of a fan stage, composed of an upstream fan rotor and a downstream fan exit guide vane (FEGV), is examined. An existing model for the wakes generated by the rotor is analyzed to provide realistic magnitudes for the vortical excitations imposed at the inlet to the FEGV. The acoustic response of the FEGV is determined at multiples of the blade passing frequency (BPF) by using the linearized unsteady flow analysis, LINFLO. Acoustic field contours are presented at each multiple of BPF illustrating the generated acoustic response disturbances. Anti-sound is then provided by placing oscillating control surfaces, whose lengths and locations are specified arbitrarily, on the blades. An analysis is then conducted to determine the complex amplitudes required for the control surface motions to best reduce the noise. It is demonstrated that if the number of acoustic response modes to be controlled is equal to the number of available independent control surfaces, complete noise cancellation can be achieved. A weighted least squares minimization procedure for the control equations is given for cases in which the number of acoustic modes exceeds the number of available control surfaces. The effectiveness of the control is measured by the magnitude of a propagating acoustic response vector, which is related to the circumferentially averaged sound pressure level (SPL), and is minimized by a standard least-squares minimization procedure.

  4. Head-mounted active noise control system with virtual sensing technique

    NASA Astrophysics Data System (ADS)

    Miyazaki, Nobuhiro; Kajikawa, Yoshinobu

    2015-03-01

    In this paper, we apply a virtual sensing technique to a head-mounted active noise control (ANC) system we have already proposed. The proposed ANC system can reduce narrowband noise while improving the noise reduction ability at the desired locations. A head-mounted ANC system based on an adaptive feedback structure can reduce noise with periodicity or narrowband components. However, since quiet zones are formed only at the locations of error microphones, an adequate noise reduction cannot be achieved at the locations where error microphones cannot be placed such as near the eardrums. A solution to this problem is to apply a virtual sensing technique. A virtual sensing ANC system can achieve higher noise reduction at the desired locations by measuring the system models from physical sensors to virtual sensors, which will be used in the online operation of the virtual sensing ANC algorithm. Hence, we attempt to achieve the maximum noise reduction near the eardrums by applying the virtual sensing technique to the head-mounted ANC system. However, it is impossible to place the microphone near the eardrums. Therefore, the system models from physical sensors to virtual sensors are estimated using the Head And Torso Simulator (HATS) instead of human ears. Some simulation, experimental, and subjective assessment results demonstrate that the head-mounted ANC system with virtual sensing is superior to that without virtual sensing in terms of the noise reduction ability at the desired locations.

  5. The Physical Mechanism for Retinal Discrete Dark Noise: Thermal Activation or Cellular Ultraweak Photon Emission?

    PubMed

    Salari, Vahid; Scholkmann, Felix; Bokkon, Istvan; Shahbazi, Farhad; Tuszynski, Jack

    2016-01-01

    For several decades the physical mechanism underlying discrete dark noise of photoreceptors in the eye has remained highly controversial and poorly understood. It is known that the Arrhenius equation, which is based on the Boltzmann distribution for thermal activation, can model only a part (e.g. half of the activation energy) of the retinal dark noise experimentally observed for vertebrate rod and cone pigments. Using the Hinshelwood distribution instead of the Boltzmann distribution in the Arrhenius equation has been proposed as a solution to the problem. Here, we show that the using the Hinshelwood distribution does not solve the problem completely. As the discrete components of noise are indistinguishable in shape and duration from those produced by real photon induced photo-isomerization, the retinal discrete dark noise is most likely due to 'internal photons' inside cells and not due to thermal activation of visual pigments. Indeed, all living cells exhibit spontaneous ultraweak photon emission (UPE), mainly in the optical wavelength range, i.e., 350-700 nm. We show here that the retinal discrete dark noise has a similar rate as UPE and therefore dark noise is most likely due to spontaneous cellular UPE and not due to thermal activation.

  6. The Physical Mechanism for Retinal Discrete Dark Noise: Thermal Activation or Cellular Ultraweak Photon Emission?

    PubMed Central

    Salari, Vahid; Scholkmann, Felix; Bokkon, Istvan; Shahbazi, Farhad; Tuszynski, Jack

    2016-01-01

    For several decades the physical mechanism underlying discrete dark noise of photoreceptors in the eye has remained highly controversial and poorly understood. It is known that the Arrhenius equation, which is based on the Boltzmann distribution for thermal activation, can model only a part (e.g. half of the activation energy) of the retinal dark noise experimentally observed for vertebrate rod and cone pigments. Using the Hinshelwood distribution instead of the Boltzmann distribution in the Arrhenius equation has been proposed as a solution to the problem. Here, we show that the using the Hinshelwood distribution does not solve the problem completely. As the discrete components of noise are indistinguishable in shape and duration from those produced by real photon induced photo-isomerization, the retinal discrete dark noise is most likely due to ‘internal photons’ inside cells and not due to thermal activation of visual pigments. Indeed, all living cells exhibit spontaneous ultraweak photon emission (UPE), mainly in the optical wavelength range, i.e., 350–700 nm. We show here that the retinal discrete dark noise has a similar rate as UPE and therefore dark noise is most likely due to spontaneous cellular UPE and not due to thermal activation. PMID:26950936

  7. The Physical Mechanism for Retinal Discrete Dark Noise: Thermal Activation or Cellular Ultraweak Photon Emission?

    PubMed

    Salari, Vahid; Scholkmann, Felix; Bokkon, Istvan; Shahbazi, Farhad; Tuszynski, Jack

    2016-01-01

    For several decades the physical mechanism underlying discrete dark noise of photoreceptors in the eye has remained highly controversial and poorly understood. It is known that the Arrhenius equation, which is based on the Boltzmann distribution for thermal activation, can model only a part (e.g. half of the activation energy) of the retinal dark noise experimentally observed for vertebrate rod and cone pigments. Using the Hinshelwood distribution instead of the Boltzmann distribution in the Arrhenius equation has been proposed as a solution to the problem. Here, we show that the using the Hinshelwood distribution does not solve the problem completely. As the discrete components of noise are indistinguishable in shape and duration from those produced by real photon induced photo-isomerization, the retinal discrete dark noise is most likely due to 'internal photons' inside cells and not due to thermal activation of visual pigments. Indeed, all living cells exhibit spontaneous ultraweak photon emission (UPE), mainly in the optical wavelength range, i.e., 350-700 nm. We show here that the retinal discrete dark noise has a similar rate as UPE and therefore dark noise is most likely due to spontaneous cellular UPE and not due to thermal activation. PMID:26950936

  8. Secondary Path Modeling Method for Active Noise Control of Power Transformer

    NASA Astrophysics Data System (ADS)

    Zhao, Tong; Liang, Jiabi; Liang, Yuanbin; Wang, Lixin; Pei, Xiugao; Li, Peng

    The accuracy of the secondary path modeling is critical to the stability of active noise control system. On condition of knowing the input and output of the secondary path, system identification theory can be used to identify the path. Based on the experiment data, correlation analysis is adopted to eliminate the random noise and nonlinear harmonic in the output data in order to obtain the accurate frequency characteristic of the secondary path. After that, Levy's Method is applied to identify the transfer function of the path. Computer simulation results are given respectively, both showing the proposed off-line modeling method is feasible and applicable. At last, Levy's Method is used to attain an accurate secondary path model in the active control of transformer noise experiment and achieves to make the noise sound level decrease about 10dB.

  9. Modeling, analysis, and validation of an active T-shaped noise barrier.

    PubMed

    Fan, Rongping; Su, Zhongqing; Cheng, Li

    2013-09-01

    With ever-increasing land traffic, abatement of traffic noise using noise barriers remains significant, yet it is a challenging task due to spatial competition with other infrastructure. In this study, a deep insight into the diffraction characteristics of acoustic fields near noise barriers of various geometries and surface conditions was achieved using numerical simulations. A T-shaped passive noise barrier with acoustically soft upper surfaces was demonstrated to outperform other candidates in a middle- or high-frequency range. Based on attributes of the acoustic field diffracted by T-shaped barriers, an active control strategy was developed to revamp the T-shaped barrier, in which a filtered minimax algorithm was established to drive the secondary sound sources. This algorithm resulted in more uniformly distributed residual sound fields than a filtered-X least mean square algorithm. Performance of the actively controlled barrier was evaluated at different positions and spacings of secondary sound sources and error sensors, leading to a series of optimal criteria for the design of active noise barriers. A prototype was fabricated and validated experimentally, manifesting particular effectiveness in insulating low-frequency noise, supplementing well the capacity of a passive T-shaped barrier which is effective in the middle- or high-frequency range.

  10. Postal cancellation from spaceport

    NASA Astrophysics Data System (ADS)

    The John F. Kennedy Space Center, in cooperation with the United States Postal Service, is offering a cancellation service to interested philatelists for the space flight programs at Kennedy.Philatelists who wish to avail themselves of this service may do so by following the procedures outlined below: Specify the event for which you wish this service. There is a limit of five covers per customer per event.

  11. Noise influence on spike activation in a Hindmarsh-Rose small-world neural network

    NASA Astrophysics Data System (ADS)

    Zhe, Sun; Micheletto, Ruggero

    2016-07-01

    We studied the role of noise in neural networks, especially focusing on its relation to the propagation of spike activity in a small sized system. We set up a source of information using a single neuron that is constantly spiking. This element called initiator x o feeds spikes to the rest of the network that is initially quiescent and subsequently reacts with vigorous spiking after a transitional period of time. We found that noise quickly suppresses the initiator’s influence and favors spontaneous spike activity and, using a decibel representation of noise intensity, we established a linear relationship between noise amplitude and the interval from the initiator’s first spike and the rest of the network activation. We studied the same process with networks of different sizes (number of neurons) and found that the initiator x o has a measurable influence on small networks, but as the network grows in size, spontaneous spiking emerges disrupting its effects on networks of more than about N = 100 neurons. This suggests that the mechanism of internal noise generation allows information transmission within a small neural neighborhood, but decays for bigger network domains. We also analyzed the Fourier spectrum of the whole network membrane potential and verified that noise provokes the reduction of main θ and α peaks before transitioning into chaotic spiking. However, network size does not reproduce a similar phenomena; instead we recorded a reduction in peaks’ amplitude, a better sharpness and definition of Fourier peaks, but not the evident degeneration to chaos observed with increasing external noise. This work aims to contribute to the understanding of the fundamental mechanisms of propagation of spontaneous spiking in neural networks and gives a quantitative assessment of how noise can be used to control and modulate this phenomenon in Hindmarsh-Rose (H-R) neural networks.

  12. Noise influence on spike activation in a Hindmarsh–Rose small-world neural network

    NASA Astrophysics Data System (ADS)

    Zhe, Sun; Micheletto, Ruggero

    2016-07-01

    We studied the role of noise in neural networks, especially focusing on its relation to the propagation of spike activity in a small sized system. We set up a source of information using a single neuron that is constantly spiking. This element called initiator x o feeds spikes to the rest of the network that is initially quiescent and subsequently reacts with vigorous spiking after a transitional period of time. We found that noise quickly suppresses the initiator’s influence and favors spontaneous spike activity and, using a decibel representation of noise intensity, we established a linear relationship between noise amplitude and the interval from the initiator’s first spike and the rest of the network activation. We studied the same process with networks of different sizes (number of neurons) and found that the initiator x o has a measurable influence on small networks, but as the network grows in size, spontaneous spiking emerges disrupting its effects on networks of more than about N = 100 neurons. This suggests that the mechanism of internal noise generation allows information transmission within a small neural neighborhood, but decays for bigger network domains. We also analyzed the Fourier spectrum of the whole network membrane potential and verified that noise provokes the reduction of main θ and α peaks before transitioning into chaotic spiking. However, network size does not reproduce a similar phenomena; instead we recorded a reduction in peaks’ amplitude, a better sharpness and definition of Fourier peaks, but not the evident degeneration to chaos observed with increasing external noise. This work aims to contribute to the understanding of the fundamental mechanisms of propagation of spontaneous spiking in neural networks and gives a quantitative assessment of how noise can be used to control and modulate this phenomenon in Hindmarsh‑Rose (H‑R) neural networks.

  13. Advanced modeling of active control of fan noise for ultra high bypass turbofan engines

    NASA Astrophysics Data System (ADS)

    Hutcheson, Florence Vanel

    1999-11-01

    An advanced model of active control of fan noise for ultra high bypass turbofan engines has been developed. This model is based on a boundary integral equation method and simulates the propagation, radiation and control of the noise generated by an engine fan surrounded by a duct of finite length and cylindrical shape, placed in a uniform flow. Control sources, modeled by point monopoles placed along the wall of the engine inlet or outlet duct, inject anti-noise into the duct to destructively interfere with the sound field generated by the fan. The duct inner wall can be lined or rigid. Unlike current methods, reflection from the duct openings is taken into account, as well as the presence of the evanescent modes. Forward, as well as backward (i.e., from the rear of the engine), external radiation is computed. The development of analytical expressions for the sound field resulting from both the fan loading noise and the control sources is presented. Two fan models are described. The first model uses spinning line sources with radially distributed strength to model the loading force that the fan blades exert on the medium. The second model uses radial arrays of spinning point dipoles to simulate the generation of fan modes of specific modal amplitudes. It is shown that these fan models can provide a reasonable approximation of actual engine fan noise in the instance when the modal amplitude of the propagating modes or the loading force distribution on the fan blades, is known. Sample cases of active noise control are performed to demonstrate the feasibility of the model. The results from these tests indicate that this model (1)is conducive to more realistic studies of active control of fan noise on ultra high bypass turbofan engines because it accounts for the presence of evanescent modes and for interference between inlet and outlet radiation, which were shown to have some impact on the performance of the active control system; (2)is very useful because it allows

  14. Resonant activation in a colored multiplicative thermal noise driven closed system

    SciTech Connect

    Ray, Somrita; Bag, Bidhan Chandra; Mondal, Debasish

    2014-05-28

    In this paper, we have demonstrated that resonant activation (RA) is possible even in a thermodynamically closed system where the particle experiences a random force and a spatio-temporal frictional coefficient from the thermal bath. For this stochastic process, we have observed a hallmark of RA phenomena in terms of a turnover behavior of the barrier-crossing rate as a function of noise correlation time at a fixed noise variance. Variance can be fixed either by changing temperature or damping strength as a function of noise correlation time. Our another observation is that the barrier crossing rate passes through a maximum with increase in coupling strength of the multiplicative noise. If the damping strength is appreciably large, then the maximum may disappear. Finally, we compare simulation results with the analytical calculation. It shows that there is a good agreement between analytical and numerical results.

  15. 30 CFR 280.27 - When may MMS cancel my permit?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... responsible for proper abandonment of any drill site according to the requirements of 30 CFR 251.7(b)(8). You... 30 Mineral Resources 2 2010-07-01 2010-07-01 false When may MMS cancel my permit? 280.27 Section... Part Interrupted Activities § 280.27 When may MMS cancel my permit? The RD may cancel a permit at...

  16. Experimental Investigation of Active Noise Controller for Internal Combustion Engine Exhaust System

    NASA Astrophysics Data System (ADS)

    Wu, Jian-Da; Chen, Chih-Keng; Lee, Chun-Ying; Lee, Tian-Hua

    2002-10-01

    Two active noise control (ANC) algorithms for internal combustion engine exhaust systems are developed and their performances are compared in various experiments. The first controller is based on the filtered-x least mean square (FXLMS) algorithm with feedback neutralization, while the second is a fixed controller with a gain-scheduled active control technique for broadband attenuation with thermal effects. Both control algorithms are implemented on a digital signal processing (DSP) platform. Experiments are carried out to evaluate the attenuation performance of the proposed active noise control systems for an engine exhaust system. The results of the experiments indicate that both the adaptive controller and the gain-scheduled controller effectively suppress the noise of engine exhaust systems. The experimental comparison and analysis of the proposed controllers are also described.

  17. Preliminary experiments on active control of fan noise from a turbofan engine

    NASA Technical Reports Server (NTRS)

    Thomas, R. H.; Burdisso, R. A.; Fuller, C. R.; O'Brien, W. F.

    1993-01-01

    In the preliminary experiments reported here, active acoustic sources positioned around the circumference of a turbofan engine were used to control the fan noise radiated forward through the inlet. The main objective was to demonstrate the potential of active techniques to alleviate the noise pollution that will be produced by the next generation of larger engines. A reduction of up to 19 dB in the radiation directivity was demonstrated in a zone that encompasses a 30-deg angle, near the error sensor, while spillover effects were observed toward the lateral direction. The simultaneous control of two tones was also demonstrated using two identical controllers in a parallel control configuration.

  18. Anticipated Effectiveness of Active Noise Control in Propeller Aircraft Interiors as Determined by Sound Quality Tests

    NASA Technical Reports Server (NTRS)

    Powell, Clemans A.; Sullivan, Brenda M.

    2004-01-01

    Two experiments were conducted, using sound quality engineering practices, to determine the subjective effectiveness of hypothetical active noise control systems in a range of propeller aircraft. The two tests differed by the type of judgments made by the subjects: pair comparisons in the first test and numerical category scaling in the second. Although the results of the two tests were in general agreement that the hypothetical active control measures improved the interior noise environments, the pair comparison method appears to be more sensitive to subtle changes in the characteristics of the sounds which are related to passenger preference.

  19. Potential Subjective Effectiveness of Active Interior Noise Control in Propeller Airplanes

    NASA Technical Reports Server (NTRS)

    Powell, Clemans A.; Sullivan, Brenda M.

    2000-01-01

    Active noise control technology offers the potential for weight-efficient aircraft interior noise reduction, particularly for propeller aircraft. However, there is little information on how passengers respond to this type of interior noise control. This paper presents results of two experiments that use sound quality engineering practices to determine the subjective effectiveness of hypothetical active noise control (ANC) systems in a range of propeller aircraft. The two experiments differed by the type of judgments made by the subjects: pair comparisons based on preference in the first and numerical category scaling of noisiness in the second. Although the results of the two experiments were in general agreement that the hypothetical active control measures improved the interior noise environments, the pair comparison method appears to be more sensitive to subtle changes in the characteristics of the sounds which are related to passenger preference. The reductions in subjective response due to the ANC conditions were predicted with reasonable accuracy by reductions in measured loudness level. Inclusion of corrections for the sound quality characteristics of tonality and fluctuation strength in multiple regression models improved the prediction of the ANC effects.

  20. Reduced In-Plane, Low Frequency Helicopter Noise of an Active Flap Rotor

    NASA Technical Reports Server (NTRS)

    Sim, Ben W.; Janakiram, Ram D.; Barbely, Natasha L.; Solis, Eduardo

    2009-01-01

    Results from a recent joint DARPA/Boeing/NASA/Army wind tunnel test demonstrated the ability to reduce in-plane, low frequency noise of the full-scale Boeing-SMART rotor using active flaps. Test data reported in this paper illustrated that acoustic energy in the first six blade-passing harmonics could be reduced by up to 6 decibels at a moderate airspeed, level flight condition corresponding to advance ratio of 0.30. Reduced noise levels were attributed to selective active flap schedules that modified in-plane blade airloads on the advancing side of the rotor, in a manner, which generated counteracting acoustic pulses that partially offset the negative pressure peaks associated with in-plane, steady thickness noise. These favorable reduced-noise operating states are a strong function of the active flap actuation amplitude, frequency and phase. The associated noise reductions resulted in reduced aural detection distance by up to 18%, but incurred significant vibratory load penalties due to increased hub shear forces. Small reductions in rotor lift-to-drag ratios, of no more than 3%, were also measured

  1. BVI induced vibration and noise alleviation by active and passive approaches

    NASA Astrophysics Data System (ADS)

    Liu, Li

    This dissertation describes the development of a comprehensive aeroelastic/aeroacoustic simulation capability for the modeling of vibration and noise in rotorcraft induced by blade-vortex interaction (BVI). Subsequently this capability is applied to study vibration and noise reduction, using active and passive control approaches. The active approach employed is the actively controlled partial span trailing edge flaps (ACF), implemented in single and dual, servo and plain flap configurations. The passive approach is based on varying the sweep and anhedral on the tip of the rotor. Two different modern helicopters are chosen as the baseline for the implementation of ACF approach, one resembling a four-bladed MBB BO-105 hingeless rotor and the other similar to a five-bladed MD-900 bearingless rotor. The structural model is based on a finite element approach capable of simulating composite helicopter blades with swept tips, and representing multiple load paths at the blade root which is a characteristic of bearingless rotors. An unsteady compressible aerodynamic model based on a rational function approximation (RFA) approach is combined with a free wake analysis which has been enhanced by improving the wake analysis resolution and modeling a dual vortex structure. These enhancements are important for capturing BVI effects. A method for predicting compressible unsteady blade surface pressure distribution on rotor blades has been developed, which is required by the acoustic analysis. A modified version of helicopter noise code WOPWOP with provisions for blade flexibility has been combined with the aeroelastic analysis to predict the BVI noise. Several variants of the higher harmonic control (HHC) algorithm have been applied for the active noise control, as well as the simultaneous vibration and noise control. Active control of BVI noise is accomplished using feedback from an onboard microphone. The simulation has been extensively validated against experimental data and

  2. Canceling planned action: an FMRI study of countermanding saccades.

    PubMed

    Curtis, Clayton E; Cole, Michael W; Rao, Vikas Y; D'Esposito, Mark

    2005-09-01

    We investigated the voluntary control of motor behavior by studying the process of deciding whether or not to execute a movement. We imaged the human dorsal cortex while subjects performed a countermanding task that allowed us to manipulate the probability that subjects would be able to cancel a planned saccade in response to an imperative stop signal. We modeled the behavioral data as a race between gaze-shifting mechanisms and gaze-holding mechanisms towards a finish line where a saccade is generated or canceled, and estimated that saccade cancelation took approximately 160 ms. The frontal eye fields showed greater activation on stop signal trials regardless of successful cancelation, suggesting coactivation of saccade and fixation mechanisms. The supplementary eye fields, however, distinguished between successful and unsuccessful cancelation, suggesting a role in monitoring performance. These oculomotor regions play distinct roles in the decision processes mediating saccadic choice. PMID:15616130

  3. Active control of turbomachine discrete tones

    NASA Astrophysics Data System (ADS)

    Fleeter, Sanford

    This paper was directed at active control of discrete frequency noise generated by subsonic blade rows through cancellation of the blade row interaction generated propagating acoustic waves. First discrete frequency noise generated by a rotor and stator in a duct was analyzed to determine the propagating acoustic pressure waves. Then a mathematical model was developed to analyze and predict the active control of discrete frequency noise generated by subsonic blade rows through cancellation of the propagating acoustic waves, accomplished by utilizing oscillating airfoil surfaces to generate additional control propagating pressure waves. These control waves interact with the propagating acoustic waves, thereby, in principle, canceling the acoustic waves and thus, the far field discrete frequency tones. This model was then applied to a fan exit guide vane to investigate active airfoil surface techniques for control of the propagating acoustic waves, and thus the far field discrete frequency tones, generated by blade row interactions.

  4. High temperature sensor/microphone development for active noise control

    NASA Technical Reports Server (NTRS)

    Shrout, Thomas R.

    1993-01-01

    The industrial and scientific communities have shown genuine interest in electronic systems which can operate at high temperatures, among which are sensors to monitor noise, vibration, and acoustic emissions. Acoustic sensing can be accomplished by a wide variety of commercially available devices, including: simple piezoelectric sensors, accelerometers, strain gauges, proximity sensors, and fiber optics. Of the several sensing mechanisms investigated, piezoelectrics were found to be the most prevalent, because of their simplicity of design and application and, because of their high sensitivity over broad ranges of frequencies and temperature. Numerous piezoelectric materials are used in acoustic sensors today; but maximum use temperatures are imposed by their transition temperatures (T(sub c)) and by their resistivity. Lithium niobate, in single crystal form, has the highest operating temperature of any commercially available material, 650 C; but that is not high enough for future requirements. Only two piezoelectric materials show potential for use at 1000 C; AlN thin film reported to be piezoactive at 1150 C, and perovskite layer structure (PLS) materials, which possess among the highest T(sub c) (greater than 1500 C) reported for ferroelectrics. A ceramic PLS composition was chosen. The solid solution composition, 80% strontium niobate (SN) and 20% strontium tantalate (STa), with a T(sub c) approximately 1160 C, was hot forged, a process which concurrently sinters and renders the plate-like grains into a highly oriented configuration to enhance piezo properties. Poled samples of this composition showed coupling (k33) approximately 6 and piezoelectric strain constant (d33) approximately 3. Piezoactivity was seen at 1125 C, the highest temperature measurement reported for a ferroelectric ceramic. The high temperature piezoelectric responses of this, and similar PLS materials, opens the possibility of their use in electronic devices operating at temperatures up to

  5. Effects of inhomogeneous activity of players and noise on cooperation in spatial public goods games

    NASA Astrophysics Data System (ADS)

    Guan, Jian-Yue; Wu, Zhi-Xi; Wang, Ying-Hai

    2007-11-01

    We study the public goods game in the noisy case by considering the players with inhomogeneous activity of teaching on a square lattice. It is shown that the introduction of the inhomogeneous activity of teaching the players can remarkably promote cooperation. By investigating the effects of noise on cooperative behavior in detail, we find that the variation of cooperator density ρC with the noise parameter κ displays several different behaviors: ρC monotonically increases (decreases) with κ ; ρC first increases (decreases) with κ and then it decreases (increases) monotonically after reaching its maximum (minimum) value, which depends on the amount of the multiplication factor r , on whether the system is homogeneous or inhomogeneous, and on whether the adopted updating is synchronous or asynchronous. These results imply that the noise plays an important and nontrivial role in the evolution of cooperation.

  6. EEG gamma-band activity during audiovisual speech comprehension in different noise environments.

    PubMed

    Lin, Yanfei; Liu, Baolin; Liu, Zhiwen; Gao, Xiaorong

    2015-08-01

    The presence of cross-modal stochastic resonance in different noise environments has been proved in previous behavioral and event-related potential studies, while it was still unclear whether the gamma-band oscillation study was another evidence of cross-modal stochastic resonance. The multisensory gain of gamma-band activity between the audiovisual (AV) and auditory-only conditions in different noise environments was analyzed. Videos of face motion articulating words concordant with different levels of pink noise were used as stimuli. Signal-to-noise ratios (SNRs) of 0, -4, -8, -12 and -16 dB were selected to measure the speech recognition accuracy and EEG activity for 20 healthy subjects. The power and phase of EEG gamma-band oscillations increased in a time window of 50-90 ms. The multisensory gains of evoked and total activity, as well as phase-locking factor, were greatest at the -12 dB SNR, which were consistent with the behavioral result. The multisensory gain of gamma-band activity showed an inverted U-shaped curve as a function of SNR. This finding confirmed the presence of cross-modal stochastic resonance. In addition, there was a significant correlation between evoked activity and phase-locking factor of gamma-band at five different SNRs. Gamma-band oscillation was believed to play a role in the rapid processing and information linkage strengthening of AV modalities in the early stage of cognitive processes.

  7. Active control of noise radiated through rectangular plates using piezeletric patches

    NASA Astrophysics Data System (ADS)

    Santana, Danuza Cristina; Duarte, Marcus Antonio Viana; Rade, Domingos Alves

    2002-11-01

    Due to problems caused by noise in industrial environment and in human daily life, techniques of noise control have received increasing attention from engineers and researchers lately. More recently, the use of piezeletric elements as sensors and/or actuators in noise and vibration control systems has been extensively investigated. The main advantage of the use of such devices is that they can be easily integrated to the mechanical system with little added mass and relatively high control authority. The present paper addresses a technique of active control of sound transmitted through a rectangular, thin, simply supported plate by employing multiple piezeletric patches bonded to the plate's surface. A harmonic plane wave incident on one side of the plate is considered to be the primary noise source. Aiming at minimizing the noise transmitted to the other side of the plate, bending motion is induced through the piezeletric patches so that the plate behaves as a secondary sound source. The paper brings the development of the system mathematical model which enables to obtain the spatial distribution of sound pressure radiated through the plate in the far field. An optimal control technique providing the voltage control signals for the activation of the piezoelectric patches is presented, based on the minimization of a cost function representing the mean square integral of the sound pressure radiated in a semi-sphere in far field. It is also proposed a methodology for the optimal placement on the piezelectric patches using Genetic Algorithms. (To be presented in Portuguese.)

  8. [Actual and perspective activities of the European Union concerning protection against noise].

    PubMed

    Kowalska, S; Sułkowski, W

    1997-01-01

    In most industrialised countries exposure to noise is one of major health problems which, because of its social and economic dimension has been given priority in the area of preventive activities. It is estimated that only in Europe about 25-30 million people are employed in conditions under exposure to noise at excessive levels, harmful to the hearing organ, generating the risk of hearing loss (disability), and in consequence limiting the possibility of active life. Acknowledging the significance of the problem and its consequences the World Health Organization (WHO) in cooperation with the International (ISA) and European Federation of Audiological Society (EFAS) has developed the programme for the protection against noise. The prime aims of the programme are to establish the cooperation between scientists, health services and technicians in order to promote knowledge and exchange of experience, to improve workers' health, and to identify the biological, neuropsychological and psycho-social effect of noise exposure on the hearing ability. The authors discuss basic objectives and adopted strategies of experimental and clinical studies carried out in countries of the European Union, participating in the implementation of the programme. The WHO guidelines for the reduction in noise exposure in the working, municipal and recreation environments are also presented. PMID:9558638

  9. Noise-based body-wave seismic tomography in an active underground mine.

    NASA Astrophysics Data System (ADS)

    Olivier, G.; Brenguier, F.; Campillo, M.; Lynch, R.; Roux, P.

    2014-12-01

    Over the last decade, ambient noise tomography has become increasingly popular to image the earth's upper crust. The seismic noise recorded in the earth's crust is dominated by surface waves emanating from the interaction of the ocean with the solid earth. These surface waves are low frequency in nature ( < 1 Hz) and not usable for imaging smaller structures associated with mining or oil and gas applications. The seismic noise recorded at higher frequencies are typically from anthropogenic sources, which are short lived, spatially unstable and not well suited for constructing seismic Green's functions between sensors with conventional cross-correlation methods. To examine the use of ambient noise tomography for smaller scale applications, continuous data were recorded for 5 months in an active underground mine in Sweden located more than 1km below surface with 18 high frequency seismic sensors. A wide variety of broadband (10 - 3000 Hz) seismic noise sources are present in an active underground mine ranging from drilling, scraping, trucks, ore crushers and ventilation fans. Some of these sources generate favorable seismic noise, while others are peaked in frequency and not usable. In this presentation, I will show that the noise generated by mining activity can be useful if periods of seismic noise are carefully selected. Although noise sources are not temporally stable and not evenly distributed around the sensor array, good estimates of the seismic Green's functions between sensors can be retrieved for a broad frequency range (20 - 400 Hz) when a selective stacking scheme is used. For frequencies below 100 Hz, the reconstructed Green's functions show clear body-wave arrivals for almost all of the 153 sensor pairs. The arrival times of these body-waves are picked and used to image the local velocity structure. The resulting 3-dimensional image shows a high velocity structure that overlaps with a known ore-body. The material properties of the ore-body differ from

  10. Localized, Non-Harmonic Active Flap Motions for Low Frequency In-Plane Rotor Noise Reduction

    NASA Technical Reports Server (NTRS)

    Sim, Ben W.; Potsdam, Mark; Kitaplioglu, Cahit; LeMasurier, Philip; Lorber, Peter; Andrews, Joseph

    2012-01-01

    A first-of-its-kind demonstration of the use of localized, non-harmonic active flap motions, for suppressing low frequency, in-plane rotor noise, is reported in this paper. Operational feasibility is verified via testing of the full-scale AATD/Sikorsky/UTRC active flap demonstration rotor in the NFAC's 40- by 80-Foot anechoic wind tunnel. Effectiveness of using localized, non-harmonic active flap motions are compared to conventional four-per-rev harmonic flap motions, and also active flap motions derived from closed-loop acoustics implementations. All three approaches resulted in approximately the same noise reductions over an in-plane three-by-three microphone array installed forward and near in-plane of the rotor in the nearfield. It is also reported that using an active flap in this localized, non-harmonic manner, resulted in no more that 2% rotor performance penalty, but had the tendency to incur higher hub vibration levels.

  11. A method of interference cancellation in binary PSK coherent receiver

    NASA Astrophysics Data System (ADS)

    Segawa, K.; Nakagawa, M.

    1985-08-01

    A new interference cancellation method using a Costas loop is proposed for PSK communication. Experiments are reported which demonstrate the influence of the waveform distortion due to a phase shifter on the demodulated data signal, the influence of additive noise on the canceller, and the influence of interference-induced phase jitter on the Costas loop. It is demonstrated that, with the introduction of a simple additional circuit, sufficiently effective interference elimination can be achieved for delta f higher than 0.3 fB, where delta f is the difference between the frequencies of the PSK carrier and the interfering signal and fB is the data bit rate.

  12. Speech recognition in noise with active and passive hearing protectors: a comparative study.

    PubMed

    Bockstael, Annelies; De Coensel, Bert; Botteldooren, Dick; D'Haenens, Wendy; Keppler, Hannah; Maes, Leen; Philips, Birgit; Swinnen, Freya; Bart, Vinck

    2011-06-01

    The perceived negative influence of standard hearing protectors on communication is a common argument for not wearing them. Thus, "augmented" protectors have been developed to improve speech intelligibility. Nevertheless, their actual benefit remains a point of concern. In this paper, speech perception with active earplugs is compared to standard passive custom-made earplugs. The two types of active protectors included amplify the incoming sound with a fixed level or to a user selected fraction of the maximum safe level. For the latter type, minimal and maximal amplification are selected. To compare speech intelligibility, 20 different speech-in-noise fragments are presented to 60 normal-hearing subjects and speech recognition is scored. The background noise is selected from realistic industrial noise samples with different intensity, frequency, and temporal characteristics. Statistical analyses suggest that the protectors' performance strongly depends on the noise condition. The active protectors with minimal amplification outclass the others for the most difficult and the easiest situations, but they also limit binaural listening. In other conditions, the passive protectors clearly surpass their active counterparts. Subsequently, test fragments are analyzed acoustically to clarify the results. This provides useful information for developing prototypes, but also indicates that tests with human subjects remain essential. PMID:21682395

  13. Subjective Listening Effort and Electrodermal Activity in Listening Situations with Reverberation and Noise

    PubMed Central

    Haeder, Kristina; Imbery, Christina; Weber, Reinhard

    2016-01-01

    Disturbing factors like reverberation or ambient noise can impair speech recognition and raise the listening effort needed for successful communication in daily life. Situations with high listening effort are thought to result in increased stress for the listener. The aim of this study was to explore possible measures to determine listening effort in situations with varying background noise and reverberation. For this purpose, subjective ratings of listening effort, speech recognition, and stress level, together with the electrodermal activity as a measure of the autonomic stress reaction, were investigated. It was expected that the electrodermal activity would show different stress levels in different acoustic situations and might serve as an alternative to subjective ratings. Ten young normal-hearing and 17 elderly hearing-impaired subjects listened to sentences from the Oldenburg sentence test either with stationary background noise or with reverberation. Four listening situations were generated, an easy and a hard one for each of the two disturbing factors, which were related to each other by the Speech Transmission Index. The easy situation resulted in 100% and the hard situation resulted in 30 to 80% speech recognition. The results of the subjective ratings showed significant differences between the easy and the hard listening situations in both subject groups. Two methods of analyzing the electrodermal activity values revealed similar, but nonsignificant trends. Significant correlations between subjective ratings and physiological electrodermal activity data were observed for normal-hearing subjects in the noise situation. PMID:27698257

  14. 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.

  15. Method and system to perform energy-extraction based active noise control

    NASA Technical Reports Server (NTRS)

    Kelkar, Atul (Inventor); Joshi, Suresh M. (Inventor)

    2009-01-01

    A method to provide active noise control to reduce noise and vibration in reverberant acoustic enclosures such as aircraft, vehicles, appliances, instruments, industrial equipment and the like is presented. A continuous-time multi-input multi-output (MIMO) state space mathematical model of the plant is obtained via analytical modeling and system identification. Compensation is designed to render the mathematical model passive in the sense of mathematical system theory. The compensated system is checked to ensure robustness of the passive property of the plant. The check ensures that the passivity is preserved if the mathematical model parameters are perturbed from nominal values. A passivity-based controller is designed and verified using numerical simulations and then tested. The controller is designed so that the resulting closed-loop response shows the desired noise reduction.

  16. Human evoked cortical activity to signal-to-noise ratio and absolute signal level.

    PubMed

    Billings, Curtis J; Tremblay, Kelly L; Stecker, G Christopher; Tolin, Wendy M

    2009-08-01

    The purpose of this study was to determine the effect of signal level and signal-to-noise ratio (SNR) on the latency and amplitude of evoked cortical activity to further our understanding of how the human central auditory system encodes signals in noise. Cortical auditory evoked potentials (CAEPs) were recorded from 15 young normal-hearing adults in response to a 1000 Hz tone presented at two tone levels in quiet and while continuous background noise levels were varied in five equivalent SNR steps. These 12 conditions were used to determine the effects of signal level and SNR level on CAEP components P1, N1, P2, and N2. Based on prior signal-in-noise experiments conducted in animals, we hypothesized that SNR, would be a key contributor to human CAEP characteristics. As hypothesized, amplitude increased and latency decreased with increasing SNR; in addition, there was no main effect of tone level across the two signal levels tested (60 and 75 dB SPL). Morphology of the P1-N1-P2 complex was driven primarily by SNR, highlighting the importance of noise when recording CAEPs. Results are discussed in terms of the current interest in recording CAEPs in hearing aid users.

  17. Robust active noise control in the loadmaster area of a military transport aircraft.

    PubMed

    Kochan, Kay; Sachau, Delf; Breitbach, Harald

    2011-05-01

    The active noise control (ANC) method is based on the superposition of a disturbance noise field with a second anti-noise field using loudspeakers and error microphones. This method can be used to reduce the noise level inside the cabin of a propeller aircraft. However, during the design process of the ANC system, extensive measurements of transfer functions are necessary to optimize the loudspeaker and microphone positions. Sometimes, the transducer positions have to be tailored according to the optimization results to achieve a sufficient noise reduction. The purpose of this paper is to introduce a controller design method for such narrow band ANC systems. The method can be seen as an extension of common transducer placement optimization procedures. In the presented method, individual weighting parameters for the loudspeakers and microphones are used. With this procedure, the tailoring of the transducer positions is replaced by adjustment of controller parameters. Moreover, the ANC system will be robust because of the fact that the uncertainties are considered during the optimization of the controller parameters. The paper describes the necessary theoretic background for the method and demonstrates the efficiency in an acoustical mock-up of a military transport aircraft.

  18. Activation process in excitable systems with multiple noise sources: One and two interacting units.

    PubMed

    Franović, Igor; Todorović, Kristina; Perc, Matjaž; Vasović, Nebojša; Burić, Nikola

    2015-12-01

    We consider the coaction of two distinct noise sources on the activation process of a single excitable unit and two interacting excitable units, which are mathematically described by the Fitzhugh-Nagumo equations. We determine the most probable activation paths around which the corresponding stochastic trajectories are clustered. The key point lies in introducing appropriate boundary conditions that are relevant for a class II excitable unit, which can be immediately generalized also to scenarios involving two coupled units. We analyze the effects of the two noise sources on the statistical features of the activation process, in particular demonstrating how these are modified due to the linear or nonlinear form of interactions. Universal properties of the activation process are qualitatively discussed in the light of a stochastic bifurcation that underlies the transition from a stochastically stable fixed point to continuous oscillations. PMID:26764778

  19. Activation process in excitable systems with multiple noise sources: One and two interacting units

    NASA Astrophysics Data System (ADS)

    Franović, Igor; Todorović, Kristina; Perc, Matjaž; Vasović, Nebojša; Burić, Nikola

    2015-12-01

    We consider the coaction of two distinct noise sources on the activation process of a single excitable unit and two interacting excitable units, which are mathematically described by the Fitzhugh-Nagumo equations. We determine the most probable activation paths around which the corresponding stochastic trajectories are clustered. The key point lies in introducing appropriate boundary conditions that are relevant for a class II excitable unit, which can be immediately generalized also to scenarios involving two coupled units. We analyze the effects of the two noise sources on the statistical features of the activation process, in particular demonstrating how these are modified due to the linear or nonlinear form of interactions. Universal properties of the activation process are qualitatively discussed in the light of a stochastic bifurcation that underlies the transition from a stochastically stable fixed point to continuous oscillations.

  20. 43 CFR 3601.62 - Cancellation procedure.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) MINERAL MATERIALS DISPOSAL Mineral Materials Disposal; General Provisions Contract and Permit Cancellation § 3601.62 Cancellation procedure....

  1. 43 CFR 3601.62 - Cancellation procedure.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) MINERAL MATERIALS DISPOSAL Mineral Materials Disposal; General Provisions Contract and Permit Cancellation § 3601.62 Cancellation procedure....

  2. Variation in harbour porpoise activity in response to seismic survey noise.

    PubMed

    Pirotta, Enrico; Brookes, Kate L; Graham, Isla M; Thompson, Paul M

    2014-05-01

    Animals exposed to anthropogenic disturbance make trade-offs between perceived risk and the cost of leaving disturbed areas. Impact assessments tend to focus on overt behavioural responses leading to displacement, but trade-offs may also impact individual energy budgets through reduced foraging performance. Previous studies found no evidence for broad-scale displacement of harbour porpoises exposed to impulse noise from a 10 day two-dimensional seismic survey. Here, we used an array of passive acoustic loggers coupled with calibrated noise measurements to test whether the seismic survey influenced the activity patterns of porpoises remaining in the area. We showed that the probability of recording a buzz declined by 15% in the ensonified area and was positively related to distance from the source vessel. We also estimated received levels at the hydrophones and characterized the noise response curve. Our results demonstrate how environmental impact assessments can be developed to assess more subtle effects of noise disturbance on activity patterns and foraging efficiency. PMID:24850891

  3. Variation in harbour porpoise activity in response to seismic survey noise

    PubMed Central

    Pirotta, Enrico; Brookes, Kate L.; Graham, Isla M.; Thompson, Paul M.

    2014-01-01

    Animals exposed to anthropogenic disturbance make trade-offs between perceived risk and the cost of leaving disturbed areas. Impact assessments tend to focus on overt behavioural responses leading to displacement, but trade-offs may also impact individual energy budgets through reduced foraging performance. Previous studies found no evidence for broad-scale displacement of harbour porpoises exposed to impulse noise from a 10 day two-dimensional seismic survey. Here, we used an array of passive acoustic loggers coupled with calibrated noise measurements to test whether the seismic survey influenced the activity patterns of porpoises remaining in the area. We showed that the probability of recording a buzz declined by 15% in the ensonified area and was positively related to distance from the source vessel. We also estimated received levels at the hydrophones and characterized the noise response curve. Our results demonstrate how environmental impact assessments can be developed to assess more subtle effects of noise disturbance on activity patterns and foraging efficiency. PMID:24850891

  4. A boundary element approach to optimization of active noise control sources on three-dimensional structures

    NASA Technical Reports Server (NTRS)

    Cunefare, K. A.; Koopmann, G. H.

    1991-01-01

    This paper presents the theoretical development of an approach to active noise control (ANC) applicable to three-dimensional radiators. The active noise control technique, termed ANC Optimization Analysis, is based on minimizing the total radiated power by adding secondary acoustic sources on the primary noise source. ANC Optimization Analysis determines the optimum magnitude and phase at which to drive the secondary control sources in order to achieve the best possible reduction in the total radiated power from the noise source/control source combination. For example, ANC Optimization Analysis predicts a 20 dB reduction in the total power radiated from a sphere of radius at a dimensionless wavenumber ka of 0.125, for a single control source representing 2.5 percent of the total area of the sphere. ANC Optimization Analysis is based on a boundary element formulation of the Helmholtz Integral Equation, and thus, the optimization analysis applies to a single frequency, while multiple frequencies can be treated through repeated analyses.

  5. Thermal Noise Reduction of Mechanical Oscillators by Actively Controlled External Dissipative Forces

    NASA Technical Reports Server (NTRS)

    Liang, Shoudan; Medich, David; Czajkowsky, Daniel M.; Sheng, Sitong; Yuan, Jian-Yang; Shao, Zhifeng

    1999-01-01

    We show that the thermal fluctuations of very soft mechanical oscillators, such as the cantilever in an atomic force microscope (AFM), can be reduced without changing the stiffness of the spring or having to lower the environment temperature. We derive a theoretical relationship between the thermal fluctuations of an oscillator and an actively external-dissipative force. This relationship is verified by experiments with an AFM cantilever where the external active force is coupled through a magnetic field. With simple instrumentation, we have reduced the thermal noise amplitude of the cantilever by a factor of 3.4, achieving an apparent temperature of 25 K with the environment at 295K. This active noise reduction approach can significantly improve the accuracy of static position or static force measurements in a number of practical applications.

  6. Effectiveness of noise in blocking electromagnetic effects on enzyme activity in the chick embryo.

    PubMed

    Martin, A H; Moses, G C

    1995-05-01

    We have previously demonstrated that exposure of the chick embryo to a 60 Hz, 4 microT split sine wave for the first 72 hours of development causes a significant reduction in the activity of the ectoenzyme 5'-nucleotidase. This reduced activity persisted, throughout the embryonic period, despite further incubation in a field free environment. We also showed that the reduction in 5'NT activity can be localized in the developing brain to the Cerebellum. The present study reveals that superimposition of an electromagnetic noise, of similar amplitude and frequency, can mitigate the effect of the field on 5'NT activity.

  7. Dopamine Activation Preserves Visual Motion Perception Despite Noise Interference of Human V5/MT

    PubMed Central

    Yousif, Nada; Fu, Richard Z.; Abou-El-Ela Bourquin, Bilal; Bhrugubanda, Vamsee; Schultz, Simon R.

    2016-01-01

    When processing sensory signals, the brain must account for noise, both noise in the stimulus and that arising from within its own neuronal circuitry. Dopamine receptor activation is known to enhance both visual cortical signal-to-noise-ratio (SNR) and visual perceptual performance; however, it is unknown whether these two dopamine-mediated phenomena are linked. To assess this, we used single-pulse transcranial magnetic stimulation (TMS) applied to visual cortical area V5/MT to reduce the SNR focally and thus disrupt visual motion discrimination performance to visual targets located in the same retinotopic space. The hypothesis that dopamine receptor activation enhances perceptual performance by improving cortical SNR predicts that dopamine activation should antagonize TMS disruption of visual perception. We assessed this hypothesis via a double-blinded, placebo-controlled study with the dopamine receptor agonists cabergoline (a D2 agonist) and pergolide (a D1/D2 agonist) administered in separate sessions (separated by 2 weeks) in 12 healthy volunteers in a William's balance-order design. TMS degraded visual motion perception when the evoked phosphene and the visual stimulus overlapped in time and space in the placebo and cabergoline conditions, but not in the pergolide condition. This suggests that dopamine D1 or combined D1 and D2 receptor activation enhances cortical SNR to boost perceptual performance. That local visual cortical excitability was unchanged across drug conditions suggests the involvement of long-range intracortical interactions in this D1 effect. Because increased internal noise (and thus lower SNR) can impair visual perceptual learning, improving visual cortical SNR via D1/D2 agonist therapy may be useful in boosting rehabilitation programs involving visual perceptual training. SIGNIFICANCE STATEMENT In this study, we address the issue of whether dopamine activation improves visual perception despite increasing sensory noise in the visual cortex

  8. A New Method to Cancel RFI---The Adaptive Filter

    NASA Astrophysics Data System (ADS)

    Bradley, R.; Barnbaum, C.

    1996-12-01

    An increasing amount of precious radio frequency spectrum in the VHF, UHF, and microwave bands is being utilized each year to support new commercial and military ventures, and all have the potential to interfere with radio astronomy observations. Some radio spectral lines of astronomical interest occur outside the protected radio astronomy bands and are unobservable due to heavy interference. Conventional approaches to deal with RFI include legislation, notch filters, RF shielding, and post-processing techniques. Although these techniques are somewhat successful, each suffers from insufficient interference cancellation. One concept of interference excision that has not been used before in radio astronomy is adaptive interference cancellation. The concept of adaptive interference canceling was first introduced in the mid-1970s as a way to reduce unwanted noise in low frequency (audio) systems. Examples of such systems include the canceling of maternal ECG in fetal electrocardiography and the reduction of engine noise in the passenger compartment of automobiles. Only recently have high-speed digital filter chips made adaptive filtering possible in a bandwidth as large a few megahertz, finally opening the door to astronomical uses. The system consists of two receivers: the main beam of the radio telescope receives the desired signal corrupted by RFI coming in the sidelobes, and the reference antenna receives only the RFI. The reference antenna is processed using a digital adaptive filter and then subtracted from the signal in the main beam, thus producing the system output. The weights of the digital filter are adjusted by way of an algorithm that minimizes, in a least-squares sense, the power output of the system. Through an adaptive-iterative process, the interference canceler will lock onto the RFI and the filter will adjust itself to minimize the effect of the RFI at the system output. We are building a prototype 100 MHz receiver and will measure the cancellation

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

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

  10. In Situ Active Control of Noise in a 4-Tesla MRI Scanner

    PubMed Central

    Li, Mingfeng; Rudd, Brent; Lim, Teik C.; Lee, Jing-Huei

    2011-01-01

    Purpose To evaluate the effectiveness of the proposed active noise control (ANC) system for the reduction of the acoustic noise emission generated by a 4 T MRI scanner during operation and to assess the feasibility of developing an ANC device that can be deployed in situ. Materials and Methods Three typical scanning sequences, namely EPI (echo planar imaging), GEMS (gradient echo multi-slice) and MDEFT (Modified Driven Equilibrium Fourier Transform), were used for evaluating the performance of the ANC system, which was composed of a magnetic compatible headset and a multiple reference feedforward filtered-x least mean square controller. Results The greatest reduction, about 55 dB, was achieved at the harmonic at a frequency of 1.3 kHz in the GEMS case. Approximately 21 dB and 30 dBA overall reduction was achieved for GEMS noise across the entire audible frequency range. For the MDEFT sequence, the control system achieved 14 dB and 14 dBA overall reduction in the audible frequency range, while 13 dB and 14 dBA reduction was obtained for the EPI case. Conclusion The result is highly encouraging because it shows great potential for treating MRI noise with an ANC application during real time scanning. PMID:21751284

  11. Alien Crosstalk Cancellation for Multipair Digital Subscriber Line Systems

    NASA Astrophysics Data System (ADS)

    Ginis, George; Peng, Chia-Ning

    2006-12-01

    An overview of alien crosstalk cancellation for DSL systems with multiple pairs is here presented. It is shown that when a common crosstalk source affects the receivers of multiple pairs, the noise exhibits a certain correlation among the pairs. In a DMT system, the frequency-domain noise samples are most strongly correlated between pairs when they correspond to the same tone. Thus, noise decorrelation algorithms applied independently for each tone can provide significant performance enhancements. Three possible methods are described for noise decorrelation, one is suitable for two-sided coordination and two are suited for receiver coordination among the pairs. It is theoretically proven that the data-rate performance of these three methods is identical from the perspective of the sum rate over all pairs. Simulation results corresponding to an ADSL2+ two-pair system with a T1 disturber are presented to illustrate the noise correlation property and to indicate the potential performance benefits.

  12. Activation barrier scaling and crossover for noise-induced switching in micromechanical parametric oscillators.

    PubMed

    Chan, H B; Stambaugh, C

    2007-08-10

    We explore fluctuation-induced switching in parametrically driven micromechanical torsional oscillators. The oscillators possess one, two, or three stable attractors depending on the modulation frequency. Noise induces transitions between the coexisting attractors. Near the bifurcation points, the activation barriers are found to have a power law dependence on frequency detuning with critical exponents that are in agreement with predicted universal scaling relationships. At large detuning, we observe a crossover to a different power law dependence with an exponent that is device specific.

  13. Active Control of Fan Noise: Feasibility Study. Volume 6; Theoretical Analysis for Coupling of Active Noise Control Actuator Ring Sources to an Annular Duct with Flow

    NASA Technical Reports Server (NTRS)

    Kraft, R. E.

    1996-01-01

    The objective of this effort is to develop an analytical model for the coupling of active noise control (ANC) piston-type actuators that are mounted flush to the inner and outer walls of an annular duct to the modes in the duct generated by the actuator motion. The analysis will be used to couple the ANC actuators to the modal analysis propagation computer program for the annular duct, to predict the effects of active suppression of fan-generated engine noise sources. This combined program will then be available to assist in the design or evaluation of ANC systems in fan engine annular exhaust ducts. An analysis has been developed to predict the modes generated in an annular duct due to the coupling of flush-mounted ring actuators on the inner and outer walls of the duct. The analysis has been combined with a previous analysis for the coupling of modes to a cylindrical duct in a FORTRAN computer program to perform the computations. The method includes the effects of uniform mean flow in the duct. The program can be used for design or evaluation purposes for active noise control hardware for turbofan engines. Predictions for some sample cases modeled after the geometry of the NASA Lewis ANC Fan indicate very efficient coupling in both the inlet and exhaust ducts for the m = 6 spinning mode at frequencies where only a single radial mode is cut-on. Radial mode content in higher order cut-off modes at the source plane and the required actuator displacement amplitude to achieve 110 dB SPL levels in the desired mode were predicted. Equivalent cases with and without flow were examined for the cylindrical and annular geometry, and little difference was found for a duct flow Mach number of 0.1. The actuator ring coupling program will be adapted as a subroutine to the cylindrical duct modal analysis and the exhaust duct modal analysis. This will allow the fan source to be defined in terms of characteristic modes at the fan source plane and predict the propagation to the

  14. Active Control of Inlet Noise on the JT15D Turbofan Engine

    NASA Technical Reports Server (NTRS)

    Smith, Jerome P.; Hutcheson, Florence V.; Burdisso, Ricardo A.; Fuller, Chris R.

    1999-01-01

    This report presents the key results obtained by the Vibration and Acoustics Laboratories at Virginia Tech over the year from November 1997 to December 1998 on the Active Noise Control of Turbofan Engines research project funded by NASA Langley Research Center. The concept of implementing active noise control techniques with fuselage-mounted error sensors is investigated both analytically and experimentally. The analytical part of the project involves the continued development of an advanced modeling technique to provide prediction and design guidelines for application of active noise control techniques to large, realistic high bypass engines of the type on which active control methods are expected to be applied. Results from the advanced analytical model are presented that show the effectiveness of the control strategies, and the analytical results presented for fuselage error sensors show good agreement with the experimentally observed results and provide additional insight into the control phenomena. Additional analytical results are presented for active noise control used in conjunction with a wavenumber sensing technique. The experimental work is carried out on a running JT15D turbofan jet engine in a test stand at Virginia Tech. The control strategy used in these tests was the feedforward Filtered-X LMS algorithm. The control inputs were supplied by single and multiple circumferential arrays of acoustic sources equipped with neodymium iron cobalt magnets mounted upstream of the fan. The reference signal was obtained from an inlet mounted eddy current probe. The error signals were obtained from a number of pressure transducers flush-mounted in a simulated fuselage section mounted in the engine test cell. The active control methods are investigated when implemented with the control sources embedded within the acoustically absorptive material on a passively-lined inlet. The experimental results show that the combination of active control techniques with fuselage

  15. Annoyance and activity disturbance induced by high-speed railway and conventional railway noise: a contrastive case study

    PubMed Central

    2014-01-01

    Background High-speed railway (HR, Electrified railway with service speed above 200 km/h.) noise and conventional railway (CR, Electrified railway with service speed under 200 km/h.) noise are different in both time and frequency domain. There is an urgent need to study the influence of HR noise and consequently, develop appropriate noise evaluation index and limits for the total railway noise including HR and CR noise. Methods Based on binaural recording of HR and CR noises in a approximate semi-free field, noise annoyance and activity disturbance induced by maximal train pass-by events in China were investigated through laboratory subjective evaluation. 80 students within recruited 102 students, 40 males and 40 females, 23.9 ± 2.1 years old, were finally selected as the subjects. After receiving noise stimulus via headphone of a binaural audio playback system, subjects were asked to express the annoyance or activity disturbance due to railway noise at a 0-100 numerical scale. Results The results show that with the same annoyance rating (A) or activity disturbance rating (D), the A-weighted equivalent sound pressure level (LAeq) of CR noise is approximately 7 dB higher than that of HR noise. Linear regression analysis between some acoustical parameters and A (or D) suggests that the coefficient of determination (R2) is higher with the instantaneous fast A-weighted sound pressure level (LAFmax) than that with LAeq. A combined acoustical parameter, LHC = 1.74LAFmax + 0.008LAFmax(Lp-LAeq), where Lp is the sound pressure level, was derived consequently, which could better evaluate the total railway noise, including HR and CR noise. More importantly, with a given LHC, the noise annoyance of HR and CR noise is the same. Conclusions Among various acoustical parameters including LHC and LAeq, A and D have the highest correlation with LHC. LHC has been proved to be an appropriate index to evaluate the total railway noise, including both HR and CR. However

  16. Unexpected cancellations in gravity theories

    SciTech Connect

    Bern, Z.; Carrasco, J. J.; Johansson, H.; Forde, D.; Ita, H.

    2008-01-15

    Recent computations of scattering amplitudes show that N=8 supergravity is surprisingly well behaved in the ultraviolet and may even be ultraviolet finite in perturbation theory. The novel cancellations necessary for ultraviolet finiteness first appear at one loop in the guise of the ''no-triangle hypothesis.'' We study one-loop amplitudes in pure Einstein gravity and point out the existence of cancellations similar to those found previously in N=8 supergravity. These cancellations go beyond those found in the one-loop effective action. Using unitarity, this suggests that generic theories of quantum gravity based on the Einstein-Hilbert action may be better behaved in the ultraviolet at higher loops than suggested by naive power counting, though without additional (supersymmetric) cancellations they diverge. We comment on future studies that should be performed to support this proposal.

  17. Unexpected Cancellations in Gravity Theories

    SciTech Connect

    Bern, Z.; Carrasco, J.J.; Forde, D.; Ita, H.; Johansson, H.; /UCLA

    2007-07-13

    Recent computations of scattering amplitudes show that N = 8 supergravity is surprisingly well behaved in the ultraviolet and may even be ultraviolet finite in perturbation theory. The novel cancellations necessary for ultraviolet finiteness first appear at one loop in the guise of the ''no-triangle hypothesis''. We study one-loop amplitudes in pure Einstein gravity and point out the existence of cancellations similar to those found previously in N = 8 supergravity. These cancellations go beyond those found in the one-loop effective action. Using unitarity, this suggests that generic theories of quantum gravity based on the Einstein-Hilbert action may be better behaved in the ultraviolet at higher loops than suggested by naive power counting, though without additional (supersymmetric) cancellations they diverge. We comment on future studies that should be performed to support this proposal.

  18. Distinct promoter activation mechanisms modulate noise-driven HIV gene expression.

    PubMed

    Chavali, Arvind K; Wong, Victor C; Miller-Jensen, Kathryn

    2015-01-01

    Latent human immunodeficiency virus (HIV) infections occur when the virus occupies a transcriptionally silent but reversible state, presenting a major obstacle to cure. There is experimental evidence that random fluctuations in gene expression, when coupled to the strong positive feedback encoded by the HIV genetic circuit, act as a 'molecular switch' controlling cell fate, i.e., viral replication versus latency. Here, we implemented a stochastic computational modeling approach to explore how different promoter activation mechanisms in the presence of positive feedback would affect noise-driven activation from latency. We modeled the HIV promoter as existing in one, two, or three states that are representative of increasingly complex mechanisms of promoter repression underlying latency. We demonstrate that two-state and three-state models are associated with greater variability in noisy activation behaviors, and we find that Fano factor (defined as variance over mean) proves to be a useful noise metric to compare variability across model structures and parameter values. Finally, we show how three-state promoter models can be used to qualitatively describe complex reactivation phenotypes in response to therapeutic perturbations that we observe experimentally. Ultimately, our analysis suggests that multi-state models more accurately reflect observed heterogeneous reactivation and may be better suited to evaluate how noise affects viral clearance. PMID:26666681

  19. Distinct promoter activation mechanisms modulate noise-driven HIV gene expression

    NASA Astrophysics Data System (ADS)

    Chavali, Arvind K.; Wong, Victor C.; Miller-Jensen, Kathryn

    2015-12-01

    Latent human immunodeficiency virus (HIV) infections occur when the virus occupies a transcriptionally silent but reversible state, presenting a major obstacle to cure. There is experimental evidence that random fluctuations in gene expression, when coupled to the strong positive feedback encoded by the HIV genetic circuit, act as a ‘molecular switch’ controlling cell fate, i.e., viral replication versus latency. Here, we implemented a stochastic computational modeling approach to explore how different promoter activation mechanisms in the presence of positive feedback would affect noise-driven activation from latency. We modeled the HIV promoter as existing in one, two, or three states that are representative of increasingly complex mechanisms of promoter repression underlying latency. We demonstrate that two-state and three-state models are associated with greater variability in noisy activation behaviors, and we find that Fano factor (defined as variance over mean) proves to be a useful noise metric to compare variability across model structures and parameter values. Finally, we show how three-state promoter models can be used to qualitatively describe complex reactivation phenotypes in response to therapeutic perturbations that we observe experimentally. Ultimately, our analysis suggests that multi-state models more accurately reflect observed heterogeneous reactivation and may be better suited to evaluate how noise affects viral clearance.

  20. Active vibration and noise control of vibro-acoustic system by using PID controller

    NASA Astrophysics Data System (ADS)

    Li, Yunlong; Wang, Xiaojun; Huang, Ren; Qiu, Zhiping

    2015-07-01

    Active control simulation of the acoustic and vibration response of a vibro-acoustic cavity of an airplane based on a PID controller is presented. A full numerical vibro-acoustic model is developed by using an Eulerian model, which is a coupled model based on the finite element formulation. The reduced order model, which is used to design the closed-loop control system, is obtained by the combination of modal expansion and variable substitution. Some physical experiments are made to validate and update the full-order and the reduced-order numerical models. Optimization of the actuator placement is employed in order to get an effective closed-loop control system. For the controller design, an iterative method is used to determine the optimal parameters of the PID controller. The process is illustrated by the design of an active noise and vibration control system for a cavity structure. The numerical and experimental results show that a PID-based active control system can effectively suppress the noise inside the cavity using a sound pressure signal as the controller input. It is also possible to control the noise by suppressing the vibration of the structure using the structural displacement signal as the controller input. For an airplane cavity structure, considering the issue of space-saving, the latter is more suitable.

  1. Distinct promoter activation mechanisms modulate noise-driven HIV gene expression

    PubMed Central

    Chavali, Arvind K.; Wong, Victor C.; Miller-Jensen, Kathryn

    2015-01-01

    Latent human immunodeficiency virus (HIV) infections occur when the virus occupies a transcriptionally silent but reversible state, presenting a major obstacle to cure. There is experimental evidence that random fluctuations in gene expression, when coupled to the strong positive feedback encoded by the HIV genetic circuit, act as a ‘molecular switch’ controlling cell fate, i.e., viral replication versus latency. Here, we implemented a stochastic computational modeling approach to explore how different promoter activation mechanisms in the presence of positive feedback would affect noise-driven activation from latency. We modeled the HIV promoter as existing in one, two, or three states that are representative of increasingly complex mechanisms of promoter repression underlying latency. We demonstrate that two-state and three-state models are associated with greater variability in noisy activation behaviors, and we find that Fano factor (defined as variance over mean) proves to be a useful noise metric to compare variability across model structures and parameter values. Finally, we show how three-state promoter models can be used to qualitatively describe complex reactivation phenotypes in response to therapeutic perturbations that we observe experimentally. Ultimately, our analysis suggests that multi-state models more accurately reflect observed heterogeneous reactivation and may be better suited to evaluate how noise affects viral clearance. PMID:26666681

  2. Subthreshold voltage noise due to channel fluctuations in active neuronal membranes.

    PubMed

    Steinmetz, P N; Manwani, A; Koch, C; London, M; Segev, I

    2000-01-01

    Voltage-gated ion channels in neuronal membranes fluctuate randomly between different conformational states due to thermal agitation. Fluctuations between conducting and nonconducting states give rise to noisy membrane currents and subthreshold voltage fluctuations and may contribute to variability in spike timing. Here we study subthreshold voltage fluctuations due to active voltage-gated Na+ and K+ channels as predicted by two commonly used kinetic schemes: the Mainen et al. (1995) (MJHS) kinetic scheme, which has been used to model dendritic channels in cortical neurons, and the classical Hodgkin-Huxley (1952) (HH) kinetic scheme for the squid giant axon. We compute the magnitudes, amplitude distributions, and power spectral densities of the voltage noise in isopotential membrane patches predicted by these kinetic schemes. For both schemes, noise magnitudes increase rapidly with depolarization from rest. Noise is larger for smaller patch areas but is smaller for increased model temperatures. We contrast the results from Monte Carlo simulations of the stochastic nonlinear kinetic schemes with analytical, closed-form expressions derived using passive and quasi-active linear approximations to the kinetic schemes. For all subthreshold voltage ranges, the quasi-active linearized approximation is accurate within 8% and may thus be used in large-scale simulations of realistic neuronal geometries.

  3. Performance of an Active Noise Control System for Fan Tones Using Vane Actuators

    NASA Technical Reports Server (NTRS)

    Sutliff, Daniel L.; Curtis, Alan R. D.; Heidelberg, Laurence J.; Remington, Paul J.

    2000-01-01

    An Active Noise Control (ANC) system for ducted fan noise was built that uses actuators located in stator vanes. The custom designed actuators A,ere piezoelectric benders manufactured using THUNDER technology. The ANC system was tested in the NASA Active Noise Control Fan rig. A total of 168 actuators in 28 stator vanes were used (six per vane). Simultaneous inlet and exhaust acoustic power level reductions were demonstrated for a fan modal structure that contained two radial modes in each direction. Total circumferential mode power levels were reduced by up to 9 dB in the inlet and 3 dB in the exhaust. The corresponding total 2BPF tone level reductions were by 6 dB in the inlet and 2 dB in the exhaust. Farfield sound pressure level reductions of up to 17 dB were achieved at the peak mode lobe angle. The performance of the system was limited by the constraints of the power amplifiers and the presence of control spillover. Simpler control/actuator systems using carefully selected subsets of the full system and random simulated failures of up to 7% of the actuators were investigated. (The actuators were robust and none failed during the test). Useful reductions still occurred under these conditions.

  4. Long-term transportation noise annoyance is associated with subsequent lower levels of physical activity.

    PubMed

    Foraster, Maria; Eze, Ikenna C; Vienneau, Danielle; Brink, Mark; Cajochen, Christian; Caviezel, Seraina; Héritier, Harris; Schaffner, Emmanuel; Schindler, Christian; Wanner, Miriam; Wunderli, Jean-Marc; Röösli, Martin; Probst-Hensch, Nicole

    2016-05-01

    Noise annoyance (NA) might lead to behavioral patterns not captured by noise levels, which could reduce physical activity (PA) either directly or through impaired sleep and constitute a noise pathway towards cardiometabolic diseases. We investigated the association of long-term transportation NA and its main sources (aircraft, road, and railway) at home with PA levels. We assessed 3842 participants (aged 37-81) that attended the three examinations (SAP 1, 2, and 3 in years 1991, 2001 and 2011, respectively) of the population-based Swiss cohort on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA). Participants reported general 24-h transportation NA (in all examinations) and source-specific NA at night (only SAP 3) on an ICBEN-type 11-point scale. We assessed moderate, vigorous, and total PA from a short-questionnaire (SAP 3). The main outcome was moderate PA (active/inactive: cut-off≥150min/week). We used logistic regression including random effects by area and adjusting for age, sex, socioeconomic status, and lifestyles (main model) and evaluated potential effect modifiers. We analyzed associations with PA at SAP 3 a) cross-sectionally: for source-specific and transportation NA in the last year (SAP 3), and b) longitudinally: for 10-y transportation NA (mean of SAP 1+2), adjusting for prior PA (SAP 2) and changes in NA (SAP 3-2). Reported NA (score≥5) was 16.4%, 7.5%, 3%, and 1.1% for 1-year transportation, road, aircraft, and railway at SAP 3, respectively. NA was greater in the past, reaching 28.5% for 10-y transportation NA (SAP 1+2). The 10-y transportation NA was associated with a 3.2% (95% CI: 6%-0.2%) decrease in moderate PA per 1-NA rating point and was related to road and aircraft NA at night in cross-sectional analyses. The longitudinal association was stronger for women, reported daytime sleepiness or chronic diseases and it was not explained by objectively modeled levels of road traffic noise at SAP 3. In conclusion, long-term NA

  5. Low-noise encoding of active touch by layer 4 in the somatosensory cortex.

    PubMed

    Hires, Samuel Andrew; Gutnisky, Diego A; Yu, Jianing; O'Connor, Daniel H; Svoboda, Karel

    2015-08-06

    Cortical spike trains often appear noisy, with the timing and number of spikes varying across repetitions of stimuli. Spiking variability can arise from internal (behavioral state, unreliable neurons, or chaotic dynamics in neural circuits) and external (uncontrolled behavior or sensory stimuli) sources. The amount of irreducible internal noise in spike trains, an important constraint on models of cortical networks, has been difficult to estimate, since behavior and brain state must be precisely controlled or tracked. We recorded from excitatory barrel cortex neurons in layer 4 during active behavior, where mice control tactile input through learned whisker movements. Touch was the dominant sensorimotor feature, with >70% spikes occurring in millisecond timescale epochs after touch onset. The variance of touch responses was smaller than expected from Poisson processes, often reaching the theoretical minimum. Layer 4 spike trains thus reflect the millisecond-timescale structure of tactile input with little noise.

  6. Re-active Passive (RAP) Devices for Control of Noise Transmission through a Panel

    NASA Technical Reports Server (NTRS)

    Carneal, James P.; Giovanardi, Marco; Fuller, Chris R.; Palumbo, Daniel L.

    2008-01-01

    Re-Active Passive (RAP) devices have been developed to control low frequency (<1000 Hz) noise transmission through a panel. These devices use a combination of active, re-active, and passive technologies packaged into a single unit to control a broad frequency range utilizing the strength of each technology over its best suited frequency range. The RAP device uses passive constrained layer damping to cover the relatively high frequency range (>200 Hz), reactive distributed vibration absorber) to cover the medium frequency range (75 to 250 Hz), and active control for controlling low frequencies (<200 Hz). The device was applied to control noise transmission through a panel mounted in a transmission loss test facility. Experimental results are presented for the bare panel, and combinations of passive treatment, reactive treatment, and active control. Results indicate that three RAP devices were able to increase the overall broadband (15-1000 Hz) transmission loss by 9.4 dB. These three devices added a total of 285 grams to the panel mass of 6.0 kg, or approximately 5%, not including control electronics.

  7. A near-threshold, 0.16 nJ/b OOK-transmitter with 0.18 nJ/b noise-cancelling super-regenerative receiver for the medical implant communications service.

    PubMed

    Ma, Chao; Hu, Changhui; Cheng, Jiao; Xia, Lingli; Chiang, Patrick Yin

    2013-12-01

    A 0.16 nJ/b MICS transmitter and 0.18 nJ/b super-regenerative receiver are demonstrated, where each is specifically designed to operate in the near-threshold region. The low-VDD transmitter utilizes a sub-harmonic injection-locked ring oscillator, edge combiner for frequency multiplication, and class-C power amplifier. The low-VDD receiver introduces a replica super-regenerative receiver as a method to reject common-mode noise sources, such as supply/substrate coupling, thereby reducing undesired self-oscillations and improving BER. Designed in a 90-nm CMOS process, the test-chip measurements show a sensitivity of -80 dBm at 500 kb/s and -65 dBm at 1 Mb/s, respectively, at a BER less than 10⁻³, with 340 μW total power.

  8. Numerical investigation of sound transmission through double wall cylinders with respect to active noise control

    NASA Astrophysics Data System (ADS)

    Coats, T. J.; Silcox, R. J.; Lester, H. C.

    Market pressure for more fuel efficient air travel has led to increased use of turboprop and higher bypass turbofan engines. The low frequency components of propeller, jet and boundary layer noise are difficult to attenuate with conventional passive techniques. Weight and geometric restrictions for sound absorbing meterials limit the amount and type of treatment that may be applied. An active noise control (ANC) method is providing to be an attractive alternative. The approach taken in this paper uses a numerical finite/boundary element method (FEM/BEM) that may be easilty adapted to arbitrary geometries. A double walled cylinder is modeled using commercially available software. The outer shell is modeled as an aluminum cylinder, similar to that of aircraft skins. The inner shell is modeled as a composite material representative of a lightweight, stiff trim panel. Two different inner shell materials are used. The first is representative of current trim structure, the second a much stiffer composite. The primary source is generated by an exterior acoustic monopole. Control fields are generated using normal force inputs to the inner cylindrical shell. A linear least mean square (LMS) algorithm is used to determine amplitudes of control forces that minimize the interior acoustic field. Coupling of acoustic and structural modes and noise reductions are discussed for each of the inner shell materials.

  9. Structural sensing of interior sound for active control of noise in structural-acoustic cavities.

    PubMed

    Bagha, Ashok K; Modak, S V

    2015-07-01

    This paper proposes a method for structural sensing of acoustic potential energy for active control of noise in a structural-acoustic cavity. The sensing strategy aims at global control and works with a fewer number of sensors. It is based on the established concept of radiation modes and hence does not add too many states to the order of the system. Acoustic potential energy is sensed using a combination of a Kalman filter and a frequency weighting filter with the structural response measurements as the inputs. The use of Kalman filter also makes the system robust against measurement noise. The formulation of the strategy is presented using finite element models of the system including that of sensors and actuators so that it can be easily applied to practical systems. The sensing strategy is numerically evaluated in the framework of Linear Quadratic Gaussian based feedback control of interior noise in a rectangular box cavity with a flexible plate with single and multiple pairs of piezoelectric sensor-actuator patches when broadband disturbances act on the plate. The performance is compared with an "acoustic filter" that models the complete transfer function from the structure to the acoustic domain. The sensing performance is also compared with a direct estimation strategy.

  10. An active structural acoustic control approach for the reduction of the structure-borne road noise

    NASA Astrophysics Data System (ADS)

    Douville, Hugo; Berry, Alain; Masson, Patrice

    2002-11-01

    The reduction of the structure-borne road noise generated inside the cabin of an automobile is investigated using an Active Structural Acoustic Control (ASAC) approach. First, a laboratory test bench consisting of a wheel/suspension/lower suspension A-arm assembly has been developed in order to identify the vibroacoustic transfer paths (up to 250 Hz) for realistic road noise excitation of the wheel. Frequency Response Function (FRF) measurements between the excitation/control actuators and each suspension/chassis linkage are used to characterize the different transfer paths that transmit energy through the chassis of the car. Second, a FE/BE model (Finite/Boundary Elements) was developed to simulate the acoustic field of an automobile cab interior. This model is used to predict the acoustic field inside the cabin as a response to the measured forces applied on the suspension/chassis linkages. Finally, an experimental implementation of ASAC is presented. The control approach relies on the use of inertial actuators to modify the vibration behavior of the suspension and the automotive chassis such that its noise radiation efficiency is decreased. The implemented algorithm consists of a MIMO (Multiple-Input-Multiple-Output) feedforward configuration with a filtered-X LMS algorithm using an advanced reference signal (width FIR filters) using the Simulink/Dspace environment for control prototyping.

  11. Transversely isotropic elasticity imaging of cancellous bone.

    PubMed

    Shore, Spencer W; Barbone, Paul E; Oberai, Assad A; Morgan, Elise F

    2011-06-01

    , the effects of noise on reconstruction quality is demonstrated and a signal-to-noise ratio (SNR) of 40 dB is identified as a reasonable threshold for obtaining accurate reconstructions from experimental data. This study demonstrates that given an appropriate set of displacement fields, level of regularization, and signal strength, the transversely isotropic method can recover the relative magnitudes of all five elastic parameters without an independent measurement of stress. The quality of the reconstructions improves with increasing contrast, magnitude of deformation, and asymmetry in the distributions of material properties, indicating that elasticity imaging of cancellous bone could be a useful tool in laboratory studies to monitor the progression of damage and disease in this tissue. PMID:21744922

  12. Towards undistorted and noise-free speech in an MRI scanner: correlation subtraction followed by spectral noise gating.

    PubMed

    Inouye, Joshua M; Blemker, Silvia S; Inouye, David I

    2014-03-01

    Noise cancellation in an MRI environment is difficult due to the high noise levels that are in the spectral range of human speech. This paper describes a two-step method to cancel MRI noise that combines operations in both the time domain (correlation subtraction) and the frequency domain (spectral noise gating). The resulting filtered recording has a noise power suppression of over 100 dB, a significant improvement over previously described techniques on MRI noise cancellation. The distortion is lower and the noise suppression higher than using spectral noise gating in isolation. Implementation of this method will aid in detailed studies of speech in relation to vocal tract and velopharyngeal function.

  13. Activation process in excitable systems with multiple noise sources: Large number of units.

    PubMed

    Franović, Igor; Perc, Matjaž; Todorović, Kristina; Kostić, Srdjan; Burić, Nikola

    2015-12-01

    We study the activation process in large assemblies of type II excitable units whose dynamics is influenced by two independent noise terms. The mean-field approach is applied to explicitly demonstrate that the assembly of excitable units can itself exhibit macroscopic excitable behavior. In order to facilitate the comparison between the excitable dynamics of a single unit and an assembly, we introduce three distinct formulations of the assembly activation event. Each formulation treats different aspects of the relevant phenomena, including the thresholdlike behavior and the role of coherence of individual spikes. Statistical properties of the assembly activation process, such as the mean time-to-first pulse and the associated coefficient of variation, are found to be qualitatively analogous for all three formulations, as well as to resemble the results for a single unit. These analogies are shown to derive from the fact that global variables undergo a stochastic bifurcation from the stochastically stable fixed point to continuous oscillations. Local activation processes are analyzed in the light of the competition between the noise-led and the relaxation-driven dynamics. We also briefly report on a system-size antiresonant effect displayed by the mean time-to-first pulse. PMID:26764779

  14. Psychoacoustical and ear canal cancellation of (2f1-f2)-distortion products.

    PubMed

    Zwicker, E; Harris, F P

    1990-06-01

    Level and phase of the (2f1-f2)-difference tone were measured as a function of primary-tone level using the psychoacoustical method of cancellation and the objective method of emission cancellation for four frequency separations of f1 = 1620 Hz and f2 in four subjects. Differences between hearing- and emission-cancellation levels ranged from 60-33 dB as delta f = f2-f1 increased from 180 to 432 Hz. For smaller separations of the primaries, phase changes for emission cancellation covered a wide range and had sharp "steps," whereas for hearing cancellation, the phase varied only slightly. With wider separations of the primaries, the phase became more varied for hearing cancellation and more homogeneous for emission cancellation. Both emission- and hearing-cancellation level functions were nonmonotonic as a function of constant SL1 and varied SL2. Remarkable phase shifts always appeared near minima in level at all separations of the primaries for emission cancellation. Four sources may be contributing to the differences in results: (a) the frequency-dependent attenuation of the middle-ear transfer function, (b) the frequency-dependent mismatch of the acoustical impedances at the eardrum, (c) the frequency dependence of the microphone's sensitivity mounted within the probe, and (d) the different reaction of active nonlinear cochlear processes on the hearing- and emission-cancellation tones.

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

    NASA Technical Reports Server (NTRS)

    Silcox, Richard J.; Lyle, Karen H.

    1996-01-01

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

  16. Numerical Comparison of Active Acoustic and Structural Noise Control in a Stiffened Double Wall Cylinder

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.

    1996-01-01

    The active acoustic and structural noise control characteristics of a double wall cylinder with and without ring stiffeners were numerically evaluated. An exterior monopole was assumed to acoustically excite the outside of the double wall cylinder at an acoustic cavity resonance frequency. Structural modal vibration properties of the inner and outer shells were analyzed by post-processing the results from a finite element analysis. A boundary element approach was used to calculate the acoustic cavity response and the coupled structural-acoustic interaction. In the frequency region of interest, below 500 Hz, all structural resonant modes were found to be acoustically slow and the nonresonant modal response to be dominant. Active sound transmission control was achieved by control forces applied to the inner or outer shell, or acoustic control monopoles placed just outside the inner or outer shell. A least mean square technique was used to minimize the interior sound pressures at the nodes of a data recovery mesh. Results showed that single acoustic control monopoles placed just outside the inner or outer shells resulted in better sound transmission control than six distributed point forces applied to either one of the shells. Adding stiffeners to the double wall structure constrained the modal vibrations of the shells, making the double wall stiffer with associated higher modal frequencies. Active noise control obtained for the stiffened double wall configurations was less than for the unstiffened cylinder. In all cases, the acoustic control monopoles controlled the sound transmission into the interior better than the structural control forces.

  17. Evaluating the B-cell density with various activation functions using White Noise Path Integral Approach

    NASA Astrophysics Data System (ADS)

    Aban, C. J. G.; Bacolod, R. O.; Confesor, M. N. P.

    2015-06-01

    A The White Noise Path Integral Approach is used in evaluating the B-cell density or the number of B-cell per unit volume for a basic type of immune system response based on the modeling done by Perelson and Wiegel. From the scaling principles of Perelson [1], the B- cell density is obtained where antigens and antibodies mutates and activation function f(|S-SA|) is defined describing the interaction between a specific antigen and a B-cell. If the activation function f(|S-SA|) is held constant, the major form of the B-cell density evaluated using white noise analysis is similar to the form of the B-cell density obtained by Perelson and Wiegel using a differential approach.A piecewise linear functionis also used to describe the activation f(|S-SA|). If f(|S-SA|) is zero, the density decreases exponentially. If f(|S-SA|) = S-SA-SB, the B- cell density increases exponentially until it reaches a certain maximum value. For f(|S-SA|) = 2SA-SB-S, the behavior of B-cell density is oscillating and remains to be in small values.

  18. Hybrid Fluid-borne Noise Control in Fluid-filled Pipelines

    NASA Astrophysics Data System (ADS)

    Pan, M.; Johnston, N.; Plummer, A.

    2016-09-01

    This article reports on an initial investigation of a hybrid fluid-borne noise control system in hydraulic pipelines. The hybrid system is built by integrating an active feedforward noise controller with passive tuned flexible hoses. The active attenuator is designed to cancel the dominant harmonic pressure pulsations in the fluid line, while the passive hose is tuned to attenuate the residual high frequency pulsations. The active attenuator can effectively decrease the fluid-borne noise by superimposing a secondary anti-phase control signal. Adaptive notch filters with the filtered-X least mean square algorithm were applied for the controller and a frequency-domain least mean square filter was used for the secondary path on-line identification. The transmission line model was used to model the pipeline, and a time-domain hose model which includes coupling of longitudinal wall and fluid waves was used to model the flexible hose. Simulation results show that very good noise cancellation was achieved using the proposed approach, which has several advantages over existing fluid-borne noise control systems, being effective for a wide range of frequencies without impairing the system dynamic response much. While the flexible hoses may be less effective than purpose-built passive silencers, they can form an inexpensive and practical solution in combination with active control.

  19. The association of flares to cancelling magnetic features on the sun

    NASA Technical Reports Server (NTRS)

    Livi, Silvia H. B.; Martin, Sara; Wang, Haimin; Ai, Guoxiang

    1989-01-01

    Previous work relating flares to evolutionary changes of photospheric solar magnetic fields are reviewed and reinterpreted in the light of recent observations of canceling magnetic fields. The results show that cancelation happens with fields spanning a wide range of magnetic field strengths. Flares of all magnitudes begin adjacent to cancelation sites, whether the associated active region as a whole is developing or decaying. Both small and big flares are initiated near canceling sites, from the microflares associated with ephemeral regions to the kernels of the great flares. Canceling magnetic flux is observed or deduced to be the common denominator among all observed associations of flares to changing magnetic fields. It is proposed that canceling magnetic fields are a necessary evolutionary condition for the initiation of solar flares.

  20. Pairing broadband noise with cortical stimulation induces extensive suppression of ascending sensory activity

    PubMed Central

    Markovitz, Craig D.; Hogan, Patrick S.; Wesen, Kyle A.; Lim, Hubert H.

    2015-01-01

    Objective The corticofugal system can alter coding along the ascending sensory pathway. Within the auditory system, electrical stimulation of the auditory cortex (AC) paired with a pure tone can cause egocentric shifts in the tuning of auditory neurons, making them more sensitive to the pure tone frequency. Since tinnitus has been linked with hyperactivity across auditory neurons, we sought to develop a new neuromodulation approach that could suppress a wide range of neurons rather than enhance specific frequency-tuned neurons. Approach We performed experiments in the guinea pig to assess the effects of cortical stimulation paired with broadband noise (PN-Stim) on ascending auditory activity within the central nucleus of the inferior colliculus (CNIC), a widely studied region for AC stimulation paradigms. Main results All eight stimulated AC regions induced extensive suppression of activity across the CNIC that was not possible with noise stimulation alone. This suppression built up over time and remained after the PN-Stim paradigm. Significance We propose that the corticofugal system is designed to decrease the brain’s input gain to irrelevant stimuli and PN-Stim is able to artificially amplify this effect to suppress neural firing across the auditory system. The PN-Stim concept may have potential for treating tinnitus and other neurological disorders. PMID:25686163

  1. Spectral characterisation and noise performance of Vanilla—an active pixel sensor

    NASA Astrophysics Data System (ADS)

    Blue, Andrew; Bates, R.; Bohndiek, S. E.; Clark, A.; Arvanitis, Costas D.; Greenshaw, T.; Laing, A.; Maneuski, D.; Turchetta, R.; O'Shea, V.

    2008-06-01

    This work will report on the characterisation of a new active pixel sensor, Vanilla. The Vanilla comprises of 512×512 (25μm 2) pixels. The sensor has a 12 bit digital output for full-frame mode, although it can also be readout in analogue mode, whereby it can also be read in a fully programmable region-of-interest (ROI) mode. In full frame, the sensor can operate at a readout rate of more than 100 frames per second (fps), while in ROI mode, the speed depends on the size, shape and number of ROIs. For example, an ROI of 6×6 pixels can be read at 20,000 fps in analogue mode. Using photon transfer curve (PTC) measurements allowed for the calculation of the read noise, shot noise, full-well capacity and camera gain constant of the sensor. Spectral response measurements detailed the quantum efficiency (QE) of the detector through the UV and visible region. Analysis of the ROI readout mode was also performed. Such measurements suggest that the Vanilla APS (active pixel sensor) will be suitable for a wide range of applications including particle physics and medical imaging.

  2. Actuator Feasibility Study for Active Control of Ducted Axial Fan Noise

    NASA Technical Reports Server (NTRS)

    Simonich, John C.

    1994-01-01

    A feasibility study was performed to investigate actuator technology which is relevant for a particular application of active noise control for gas turbine stator vanes. This study investigated many different classes of actuators and ranked them on the order of applicability. The most difficult requirements the actuators had to meet were high frequency response, large amplitude deflections, and a thin profile. Based on this assessment, piezoelectric type actuators were selected as the most appropriate actuator class. Specifically, Rainbows (a new class of high performance piezoelectric actuators), and unimorphs (a ceramic/metal composite) appeared best suited to the requirements. A benchtop experimental study was conducted. The performance of a variety of different actuators was examined, including high polymer films, flextensional actuators, miniature speakers, unimorphs, and Rainbows. The displacement/frequency response and phase characteristics of the actuators were measured. Physical limitations of actuator operation were also examined. This report includes the first known, high displacement, dynamic data obtained for Rainbow actuators. A new "hard" ceramic Rainbow actuator which does not appear to be limited in operation by self heating as "soft" ceramic Rainbows was designed, constructed and tested. The study concludes that a suitable actuator for active noise control in gas turbine engines can be achieved with state of the art materials and processing.

  3. Pairing broadband noise with cortical stimulation induces extensive suppression of ascending sensory activity

    NASA Astrophysics Data System (ADS)

    Markovitz, Craig D.; Hogan, Patrick S.; Wesen, Kyle A.; Lim, Hubert H.

    2015-04-01

    Objective. The corticofugal system can alter coding along the ascending sensory pathway. Within the auditory system, electrical stimulation of the auditory cortex (AC) paired with a pure tone can cause egocentric shifts in the tuning of auditory neurons, making them more sensitive to the pure tone frequency. Since tinnitus has been linked with hyperactivity across auditory neurons, we sought to develop a new neuromodulation approach that could suppress a wide range of neurons rather than enhance specific frequency-tuned neurons. Approach. We performed experiments in the guinea pig to assess the effects of cortical stimulation paired with broadband noise (PN-Stim) on ascending auditory activity within the central nucleus of the inferior colliculus (CNIC), a widely studied region for AC stimulation paradigms. Main results. All eight stimulated AC subregions induced extensive suppression of activity across the CNIC that was not possible with noise stimulation alone. This suppression built up over time and remained after the PN-Stim paradigm. Significance. We propose that the corticofugal system is designed to decrease the brain’s input gain to irrelevant stimuli and PN-Stim is able to artificially amplify this effect to suppress neural firing across the auditory system. The PN-Stim concept may have potential for treating tinnitus and other neurological disorders.

  4. Analysis and control of computer cooling fan noise

    NASA Astrophysics Data System (ADS)

    Wong, Kam

    features the leading mode drag noise. Further reduction of this noise is left to the active noise control. The feasibility of the active noise control technique is demonstrated for the cancellation of both thrust and drag noise radiated at their leading modes. An open loop, feed-forward system is used to maximize the simplicity of the rig in order to deliver an appropriate technology for a small ventilation fan. (Abstract shortened by UMI.)

  5. 34 CFR 674.52 - Cancellation procedures.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... accelerated— (i) May qualify for a loan cancellation for services performed before the date of acceleration; and (ii) Cannot qualify for a cancellation for services performed on or after the date of...

  6. In-flight evaluation of noise levels and assessment of active noise reduction systems in the Seahawk S-70B-2 helicopter

    NASA Astrophysics Data System (ADS)

    King, R. B.; Foran, D. A.

    Cabin and at-ear sound spectra in the S-70B-2 at various crew positions and flight conditions were measured in order to determine the noise attenuation properties of the ALPHA helmet and the effectiveness of active noise reduction (ANR) systems developed by the Defence Research Agency-Aerospace Division (formerly the Royal Aerospace Establishment) and the BOSE Corporation. Results show that if newly proposed hearing conservation guidelines are adopted, aircrew wearing the ALPHA helmet would require additional attenuation devices. It is recommended that an ANR system be incorporated into the S-70B-2 as such a system would allow realistic flight duration to be maintained, improve voice communication, and reduce aircrew fatigue.

  7. Landslide noise.

    PubMed

    Cadman, J D; Goodman, R E

    1967-12-01

    Acoustical monitoring of real landslides has revealed the existence of subaudible noise activity prior to failure and has enabled prediction of the depth of the seat of sliding when conducted in boreholes beneath the surface. Recordings of noise generated in small slopes of moist sand, tilted to failure in laboratory tests, have been analyzed to determine the foci of discrete subaudible noise events. The noises emitted shortly before failure were plotted close to the true sliding surface observed after failure. The foci of earlier events lay either within the central portion of the sliding mass or in a region behind the failure surface. The head and toe zones were devoid of strong seismic activity. PMID:17734306

  8. 77 FR 19747 - Proposed Cancelation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-02

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF TRANSPORTATION Office of the Secretary Proposed Cancelation of the Air Taxi Authority Of VIH Cougar Helicopters, Inc... cause why it should not issue an order finding that VIH Cougar Helicopters, Inc. is not a U.S....

  9. Hybrid Active-Passive Systems for Control of Aircraft Interior Noise

    NASA Technical Reports Server (NTRS)

    Fuller, Chris R.; Palumbo, Dan (Technical Monitor)

    2002-01-01

    It was proposed to continue with development and application in the two active-passive areas of Active Tuned Vibration Absorbers (ATVA) and smart foam applied to the reduction of interior noise in aircraft. In general the work was focused on making both techniques more efficient, practical and robust thus increasing their application potential. The work was also concerned with demonstrating the potential of these two technologies under realistic implementations as well as understanding the fundamental physics of the systems. The proposed work consisted of a three-year program and was tightly coordinated with related work being carried out in the Structural Acoustics Branch at NASA LaRC. The work was supervised and coordinated through all phases by Prof Chris Fuller of Va Tech.

  10. Impacts of chronic anthropogenic noise from energy-sector activity on abundance of songbirds in the boreal forest.

    PubMed

    Bayne, Erin M; Habib, Lucas; Boutin, Stan

    2008-10-01

    The effects of human activities in forests are often examined in the context of habitat conversion. Changes in habitat structure and composition are also associated with increases in the activity of people with vehicles and equipment, which results in increases in anthropogenic noise. Anthropogenic noise may reduce habitat quality for many species, particularly those that rely on acoustic signals for communication. We compared the density and occupancy rate of forest passerines close to versus far from noise-generating compressor stations and noiseless well pads in the boreal forest of Alberta, Canada. Using distance-based sampling, we found that areas near noiseless energy facilities had a total passerine density 1.5 times higher than areas near noise-producing energy sites. The White-throated Sparrow (Zonotrichia albicollis), Yellow-rumped Warbler (Dendroica coronata), and Red-eyed Vireo (Vireo olivaceus) were less dense in noisy areas. We used repeat sampling to estimate occupancy rate for 23 additional species. Seven had lower conditional or unconditional occupancy rates near noise-generating facilities. One-third of the species examined showed patterns that supported the hypothesis that abundance is influenced by anthropogenic noise. An additional 4 species responded negatively to edge effects. To mitigate existing noise impacts on birds would require approximately $175 million. The merits of such an effort relative to other reclamation actions are discussed. Nevertheless, given the $100 billion energy-sector investment planned for the boreal forest in the next 10 years, including noise suppression technology at the outset of construction, makes noise mitigation a cost-effective best-management practice that might help conserve high-quality habitat for boreal birds. PMID:18616740

  11. Simultaneous BVI noise and vibration reduction in rotorcraft using actively-controlled flaps and including performance considerations

    NASA Astrophysics Data System (ADS)

    Patt, Daniel A.

    This work presents the development and application of an active control approach for reduction of both vibration and noise induced by helicopter rotor blade vortex interaction (BVI). Control is implemented through single or dual actively controlled flaps (ACFs) on each blade. Low-speed helicopter flight is prone to severe BVI, resulting in elevated vibration and noise levels. Existing research has suggested that when some form of active control is used to reduce vibration, noise will increase and vice versa. The present research achieves simultaneous reduction of noise and vibration, and also investigates the physical sources of the observed reduction. The initial portion of this work focused on developing a tool for simulating helicopter noise and vibrations in the BVI flight regime. A method for predicting compressible unsteady blade surface pressure distribution on rotor blades was developed and combined with an enhanced free-wake model and an acoustic prediction tool with provisions for blade flexibility. These elements were incorporated within an aeroelastic analysis featuring fully coupled flap-lag-torsional blade dynamics. Subsequently, control algorithms were developed that were effective for reducing noise and vibration even in the nonlinear BVI flight regime; saturation limits were incorporated constraining flap deflections to specified limits. The resulting simulation was also validated with a wide range of experimental data, achieving excellent correlation. Finally, a number of active control studies were performed. Multi-component vibration reductions of 40--80% could be achieved, while incurring a small noise penalty. Noise was reduced using an onboard feedback microphone; reductions of 4--10 dB on the advancing side were observed on a plane beneath the rotor when using dual flaps. Finally, simultaneous noise and vibration reduction was studied. A reduction of about 5 dB in noise on the advancing side combined with a 60% reduction in vibration was

  12. 47 CFR 213.3 - Cancellation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Cancellation. 213.3 Section 213.3 Telecommunication OFFICE OF SCIENCE AND TECHNOLOGY POLICY AND NATIONAL SECURITY COUNCIL GOVERNMENT AND PUBLIC CORRESPONDENCE TELECOMMUNICATIONS PRECEDENCE SYSTEM § 213.3 Cancellation. This circular cancels: (a)...

  13. 47 CFR 213.3 - Cancellation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Cancellation. 213.3 Section 213.3 Telecommunication OFFICE OF SCIENCE AND TECHNOLOGY POLICY AND NATIONAL SECURITY COUNCIL GOVERNMENT AND PUBLIC CORRESPONDENCE TELECOMMUNICATIONS PRECEDENCE SYSTEM § 213.3 Cancellation. This circular cancels: (a)...

  14. 47 CFR 213.3 - Cancellation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Cancellation. 213.3 Section 213.3 Telecommunication OFFICE OF SCIENCE AND TECHNOLOGY POLICY AND NATIONAL SECURITY COUNCIL GOVERNMENT AND PUBLIC CORRESPONDENCE TELECOMMUNICATIONS PRECEDENCE SYSTEM § 213.3 Cancellation. This circular cancels: (a)...

  15. 47 CFR 213.3 - Cancellation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Cancellation. 213.3 Section 213.3 Telecommunication OFFICE OF SCIENCE AND TECHNOLOGY POLICY AND NATIONAL SECURITY COUNCIL GOVERNMENT AND PUBLIC CORRESPONDENCE TELECOMMUNICATIONS PRECEDENCE SYSTEM § 213.3 Cancellation. This circular cancels: (a)...

  16. Noise power associated with decreased task-induced variability of brain electrical activity in schizophrenia.

    PubMed

    Molina, Vicente; Bachiller, Alejandro; Suazo, Vanessa; Lubeiro, Alba; Poza, Jesús; Hornero, Roberto

    2016-02-01

    In schizophrenia, both increased baseline metabolic and electroencephalographic (EEG) activities as well as decreased task-related modulation of neural dynamics have been reported. Noise power (NP) can measure the background EEG activity during task performance, and Shannon entropy (SE) is useful for quantifying the global modulation of EEG activity with a high temporal resolution. In this study, we have assessed the possible relationship between increased NP in theta and gamma bands and decreased SE modulation in 24 patients with schizophrenia and 26 controls over the parietal and central regions during a P300 task. SE modulation was calculated as the change from baseline to the active epoch (i.e., 150-550 ms following the target stimulus onset). Patients with schizophrenia displayed statistically significant higher NP values and lower SE modulation than healthy controls. We found a significant association between gamma NP and SE in all of the participants. Specifically, a NP increase in the gamma band was followed by a decrease in SE change. These results support the notion that an excess of gamma activity, unlocked to the task being performed, is accompanied by a decreased modulation of EEG activity in schizophrenia.

  17. Performance of Optimized Actuator and Sensor Arrays in an Active Noise Control System

    NASA Technical Reports Server (NTRS)

    Palumbo, D. L.; Padula, S. L.; Lyle, K. H.; Cline, J. H.; Cabell, R. H.

    1996-01-01

    Experiments have been conducted in NASA Langley's Acoustics and Dynamics Laboratory to determine the effectiveness of optimized actuator/sensor architectures and controller algorithms for active control of harmonic interior noise. Tests were conducted in a large scale fuselage model - a composite cylinder which simulates a commuter class aircraft fuselage with three sections of trim panel and a floor. Using an optimization technique based on the component transfer functions, combinations of 4 out of 8 piezoceramic actuators and 8 out of 462 microphone locations were evaluated against predicted performance. A combinatorial optimization technique called tabu search was employed to select the optimum transducer arrays. Three test frequencies represent the cases of a strong acoustic and strong structural response, a weak acoustic and strong structural response and a strong acoustic and weak structural response. Noise reduction was obtained using a Time Averaged/Gradient Descent (TAGD) controller. Results indicate that the optimization technique successfully predicted best and worst case performance. An enhancement of the TAGD control algorithm was also evaluated. The principal components of the actuator/sensor transfer functions were used in the PC-TAGD controller. The principal components are shown to be independent of each other while providing control as effective as the standard TAGD.

  18. 3D active edge silicon sensors with different electrode configurations: Radiation hardness and noise performance

    NASA Astrophysics Data System (ADS)

    Da Viá, C.; Bolle, E.; Einsweiler, K.; Garcia-Sciveres, M.; Hasi, J.; Kenney, C.; Linhart, V.; Parker, Sherwood; Pospisil, S.; Rohne, O.; Slavicek, T.; Watts, S.; Wermes, N.

    2009-06-01

    3D detectors, with electrodes penetrating the entire silicon wafer and active edges, were fabricated at the Stanford Nano Fabrication Facility (SNF), California, USA, with different electrode configurations. After irradiation with neutrons up to a fluence of 8.8×10 15 n eq cm -2, they were characterised using an infrared laser tuned to inject ˜2 minimum ionising particles showing signal efficiencies as high as 66% for the configuration with the shortest (56 μm) inter-electrode spacing. Sensors from the same wafer were also bump-bonded to the ATLAS FE-I3 pixel readout chip and their noise characterised. Most probable signal-to-noise ratios were calculated before and after irradiation to be as good as 38:1 after the highest irradiation level with a substrate thickness of 210 μm. These devices are promising candidates for application at the LHC such as the very forward detectors at ATLAS and CMS, the ATLAS B-Layer replacement and the general pixel upgrade. Moreover, 3D sensors could play a role in applications where high speed, high-resolution detectors are required, such as the vertex locators at the proposed Compact Linear Collider (CLIC) at CERN.

  19. Low-noise encoding of active touch by layer 4 in the somatosensory cortex

    PubMed Central

    Andrew Hires, Samuel; Gutnisky, Diego A; Yu, Jianing; O'Connor, Daniel H; Svoboda, Karel

    2015-01-01

    Cortical spike trains often appear noisy, with the timing and number of spikes varying across repetitions of stimuli. Spiking variability can arise from internal (behavioral state, unreliable neurons, or chaotic dynamics in neural circuits) and external (uncontrolled behavior or sensory stimuli) sources. The amount of irreducible internal noise in spike trains, an important constraint on models of cortical networks, has been difficult to estimate, since behavior and brain state must be precisely controlled or tracked. We recorded from excitatory barrel cortex neurons in layer 4 during active behavior, where mice control tactile input through learned whisker movements. Touch was the dominant sensorimotor feature, with >70% spikes occurring in millisecond timescale epochs after touch onset. The variance of touch responses was smaller than expected from Poisson processes, often reaching the theoretical minimum. Layer 4 spike trains thus reflect the millisecond-timescale structure of tactile input with little noise. DOI: http://dx.doi.org/10.7554/eLife.06619.001 PMID:26245232

  20. Active Vibration Control for Helicopter Interior Noise Reduction Using Power Minimization

    NASA Technical Reports Server (NTRS)

    Mendoza, J.; Chevva, K.; Sun, F.; Blanc, A.; Kim, S. B.

    2014-01-01

    This report describes work performed by United Technologies Research Center (UTRC) for NASA Langley Research Center (LaRC) under Contract NNL11AA06C. The objective of this program is to develop technology to reduce helicopter interior noise resulting from multiple gear meshing frequencies. A novel active vibration control approach called Minimum Actuation Power (MAP) is developed. MAP is an optimal control strategy that minimizes the total input power into a structure by monitoring and varying the input power of controlling sources. MAP control was implemented without explicit knowledge of the phasing and magnitude of the excitation sources by driving the real part of the input power from the controlling sources to zero. It is shown that this occurs when the total mechanical input power from the excitation and controlling sources is a minimum. MAP theory is developed for multiple excitation sources with arbitrary relative phasing for single or multiple discrete frequencies and controlled by a single or multiple controlling sources. Simulations and experimental results demonstrate the feasibility of MAP for structural vibration reduction of a realistic rotorcraft interior structure. MAP control resulted in significant average global vibration reduction of a single frequency and multiple frequency excitations with one controlling actuator. Simulations also demonstrate the potential effectiveness of the observed vibration reductions on interior radiated noise.

  1. Active Structural Acoustic Control of Interior Noise on a Raytheon 1900D

    NASA Technical Reports Server (NTRS)

    Palumbo, Dan; Cabell, Ran; Sullivan, Brenda; Cline, John

    2000-01-01

    An active structural acoustic control system has been demonstrated on a Raytheon Aircraft Company 1900D turboprop airliner. Both single frequency and multi-frequency control of the blade passage frequency and its harmonics was accomplished. The control algorithm was a variant of the popular filtered-x LMS implemented in the principal component domain. The control system consisted of 21 inertial actuators and 32 microphones. The actuators were mounted to the aircraft's ring frames. The microphones were distributed uniformly throughout the interior at head height, both seated and standing. Actuator locations were selected using a combinatorial search optimization algorithm. The control system achieved a 14 dB noise reduction of the blade passage frequency during single frequency tests. Multi-frequency control of the first 1st, 2nd and 3rd harmonics resulted in 10.2 dB, 3.3 dB and 1.6 dB noise reductions respectively. These results fall short of the predictions which were produced by the optimization algorithm (13.5 dB, 8.6 dB and 6.3 dB). The optimization was based on actuator transfer functions taken on the ground and it is postulated that cabin pressurization at flight altitude was a factor in this discrepancy.

  2. Enhanced Cancelable Biometrics for Online Signature Verification

    NASA Astrophysics Data System (ADS)

    Muramatsu, Daigo; Inuma, Manabu; Shikata, Junji; Otsuka, Akira

    Cancelable approaches for biometric person authentication have been studied to protect enrolled biometric data, and several algorithms have been proposed. One drawback of cancelable approaches is that the performance is inferior to that of non-cancelable approaches. In this paper, we propose a scheme to improve the performance of a cancelable approach for online signature verification. Our scheme generates two cancelable dataset from one raw dataset and uses them for verification. Preliminary experiments were performed using a distance-based online signature verification algorithm. The experimental results show that our proposed scheme is promising.

  3. REGULAR VERSUS DIFFUSIVE PHOTOSPHERIC FLUX CANCELLATION

    SciTech Connect

    Litvinenko, Yuri E.

    2011-04-20

    Observations of photospheric flux cancellation on the Sun imply that cancellation can be a diffusive rather than regular process. A criterion is derived, which quantifies the parameter range in which diffusive photospheric cancellation should occur. Numerical estimates show that regular cancellation models should be expected to give a quantitatively accurate description of photospheric cancellation. The estimates rely on a recently suggested scaling for a turbulent magnetic diffusivity, which is consistent with the diffusivity measurements on spatial scales varying by almost two orders of magnitude. Application of the turbulent diffusivity to large-scale dispersal of the photospheric magnetic flux is discussed.

  4. Activation of SIRT3 by the NAD⁺ precursor nicotinamide riboside protects from noise-induced hearing loss.

    PubMed

    Brown, Kevin D; Maqsood, Sadia; Huang, Jing-Yi; Pan, Yong; Harkcom, William; Li, Wei; Sauve, Anthony; Verdin, Eric; Jaffrey, Samie R

    2014-12-01

    Intense noise exposure causes hearing loss by inducing degeneration of spiral ganglia neurites that innervate cochlear hair cells. Nicotinamide adenine dinucleotide (NAD(+)) exhibits axon-protective effects in cultured neurons; however, its ability to block degeneration in vivo has been difficult to establish due to its poor cell permeability and serum instability. Here, we describe a strategy to increase cochlear NAD(+) levels in mice by administering nicotinamide riboside (NR), a recently described NAD(+) precursor. We find that administration of NR, even after noise exposure, prevents noise-induced hearing loss (NIHL) and spiral ganglia neurite degeneration. These effects are mediated by the NAD(+)-dependent mitochondrial sirtuin, SIRT3, since SIRT3-overexpressing mice are resistant to NIHL and SIRT3 deletion abrogates the protective effects of NR and expression of NAD(+) biosynthetic enzymes. These findings reveal that administration of NR activates a NAD(+)-SIRT3 pathway that reduces neurite degeneration caused by noise exposure.

  5. Activation of SIRT3 by the NAD⁺ precursor nicotinamide riboside protects from noise-induced hearing loss.

    PubMed

    Brown, Kevin D; Maqsood, Sadia; Huang, Jing-Yi; Pan, Yong; Harkcom, William; Li, Wei; Sauve, Anthony; Verdin, Eric; Jaffrey, Samie R

    2014-12-01

    Intense noise exposure causes hearing loss by inducing degeneration of spiral ganglia neurites that innervate cochlear hair cells. Nicotinamide adenine dinucleotide (NAD(+)) exhibits axon-protective effects in cultured neurons; however, its ability to block degeneration in vivo has been difficult to establish due to its poor cell permeability and serum instability. Here, we describe a strategy to increase cochlear NAD(+) levels in mice by administering nicotinamide riboside (NR), a recently described NAD(+) precursor. We find that administration of NR, even after noise exposure, prevents noise-induced hearing loss (NIHL) and spiral ganglia neurite degeneration. These effects are mediated by the NAD(+)-dependent mitochondrial sirtuin, SIRT3, since SIRT3-overexpressing mice are resistant to NIHL and SIRT3 deletion abrogates the protective effects of NR and expression of NAD(+) biosynthetic enzymes. These findings reveal that administration of NR activates a NAD(+)-SIRT3 pathway that reduces neurite degeneration caused by noise exposure. PMID:25470550

  6. A Real-time Auto-detection Method for Random Telegraph Signal (RTS) Noise Detection in CMOS Active pixel sensors

    NASA Astrophysics Data System (ADS)

    Zheng, R.; Zhao, R.; Ma, Y.; Li, B.; Wei, X.; Wang, J.; Gao, W.; Wei, T.; Gao, D.; Hu, Y.

    2015-07-01

    CMOS Active pixel sensors (CMOS APS) are attractive for use in the innermost layers of charged particle trackers, due to their good tradeoffs among the key performances. However, CMOS APS can be greatly influenced by random telegraph signal (RTS) noise, which can cause particle tracking or energy calculation failures. In-depth research of pixels' RTS behavior stimulates the interest of the methods for RTS noise detection, reconstruction and parameters extraction. In this paper, a real-time auto-detection method is proposed, using real-time Gaussian noise standard deviation as the detection threshold. Experimental results show that, compared with current methods using signal standard deviation as the thresholds, the proposed method is more sensitive in multi-level RTS detection and more effective in the case of RTS noise degradation.

  7. Choice-related activity and correlated noise in subcortical vestibular neurons.

    PubMed

    Liu, Sheng; Gu, Yong; DeAngelis, Gregory C; Angelaki, Dora E

    2013-01-01

    Functional links between neuronal activity and perception are studied by examining trial-by-trial correlations (choice probabilities) between neural responses and perceptual decisions. We addressed fundamental issues regarding the nature and origin of choice probabilities by recording from subcortical (brainstem and cerebellar) neurons in rhesus monkeys during a vestibular heading discrimination task. Subcortical neurons showed robust choice probabilities that exceeded those seen in cortex (area MSTd) under identical conditions. The greater choice probabilities of subcortical neurons could be predicted by a stronger dependence of correlated noise on tuning similarity, as revealed by population decoding. Significant choice probabilities were observed almost exclusively for neurons that responded selectively to translation, whereas neurons that represented net gravito-inertial acceleration did not show choice probabilities. These findings suggest that the emergence of choice probabilities in the vestibular system depends on a critical signal transformation that occurs in subcortical pathways to distinguish translation from orientation relative to gravity. PMID:23178975

  8. Adaptive RSOV filter using the FELMS algorithm for nonlinear active noise control systems

    NASA Astrophysics Data System (ADS)

    Zhao, Haiquan; Zeng, Xiangping; He, Zhengyou; Li, Tianrui

    2013-01-01

    This paper presents a recursive second-order Volterra (RSOV) filter to solve the problems of signal saturation and other nonlinear distortions that occur in nonlinear active noise control systems (NANC) used for actual applications. Since this nonlinear filter based on an infinite impulse response (IIR) filter structure can model higher than second-order and third-order nonlinearities for systems where the nonlinearities are harmonically related, the RSOV filter is more effective in NANC systems with either a linear secondary path (LSP) or a nonlinear secondary path (NSP). Simulation results clearly show that the RSOV adaptive filter using the multichannel structure filtered-error least mean square (FELMS) algorithm can further greatly reduce the computational burdens and is more suitable to eliminate nonlinear distortions in NANC systems than a SOV filter, a bilinear filter and a third-order Volterra (TOV) filter.

  9. Impact of Substrate Bias on Fixed-Pattern-Noise in Active Pixel Sensor Cells

    NASA Astrophysics Data System (ADS)

    Terauchi, Mamoru

    2007-11-01

    The effect of substrate (body) bias on fixed-pattern-noise (FPN) in active pixel sensor (APS) cells is studied. Through measuring test devices consisting of two metal-oxide-semiconductor field-effect transistors (MOSFETs) connected in series with each of the transistors located in the same well region, it has been revealed that substrate bias, which is inevitably applied in a normal circuit configuration in conventional APS cells, worsens the characteristics fluctuation in source-follower amplifiers in APS cells, leading to FPN that cannot be mitigated by conventional correction methods such as correlated double sampling. In addition it has been confirmed that the current-voltage characteristics of logarithmic converters, each of which is realized using a MOSFET with gate and drain terminals connected together, are also affected by substrate bias, resulting in increased characteristics fluctuation as compared with the case with no substrate bias.

  10. Modular feed-forward active noise control units for ventilation ducts.

    PubMed

    Gardonio, P; Rohlfing, J

    2014-12-01

    This paper presents theoretical and experimental work on feed-forward active noise control for a ventilation duct. In particular three single channel control arrangements are investigated: (a) A classical widespread-mid-span configuration, where the control loudspeakers are located approximately half way through the duct and the reference and error microphones are placed close to inlet and outlet duct sections, respectively; (b) a compact-mid-span configuration, where both the reference and error microphones are moved close to the control loudspeakers to form a self-contained control unit, and (c) a compact-outlet configuration where the self-contained control unit is moved to the duct outlet. The two compact configurations offer self-evident practical installation and operation advantages. Moreover, the paper shows that they are characterized by much simpler control filters, which can be effectively implemented on modern audio digital signal processing boards and produce similar control performance to the classical widespread configuration. PMID:25480054

  11. H.R. 73: A Bill to protect the ecologically fragile coastal resources of south Florida by prohibiting offshore oil and gas activities and by cancelling Federal leases in the area of the Outer Continental Shelf adjacent to the south Florida coast. Introduced in the House of Representatives, One Hundred Fourth Congress, First session

    SciTech Connect

    1995-12-31

    This document contains H.R. 73, A Bill to protect the ecologically fragile coastal resources of south Florida by prohibiting offshore oil and gas activities and by cancelling Federal leases in the area of the Outer Continental Shelf adjacent to south Florida. This Bill was introduced in the House of Representatives, 104th Congress, First Session, January 4, 1995.

  12. Ignorance is bliss: general and robust cancellation of decoherence via no-knowledge quantum feedback.

    PubMed

    Szigeti, Stuart S; Carvalho, Andre R R; Morley, James G; Hush, Michael R

    2014-07-11

    A "no-knowledge" measurement of an open quantum system yields no information about any system observable; it only returns noise input from the environment. Surprisingly, performing such a no-knowledge measurement can be advantageous. We prove that a system undergoing no-knowledge monitoring has reversible noise, which can be canceled by directly feeding back the measurement signal. We show how no-knowledge feedback control can be used to cancel decoherence in an arbitrary quantum system coupled to a Markovian reservoir that is being monitored. Since no-knowledge feedback does not depend on the system state or Hamiltonian, such decoherence cancellation is guaranteed to be general and robust, and can operate in conjunction with any other quantum control protocol. As an application, we show that no-knowledge feedback could be used to improve the performance of dissipative quantum computers subjected to local loss.

  13. Active control of counter-rotating open rotor interior noise in a Dornier 728 experimental aircraft

    NASA Astrophysics Data System (ADS)

    Haase, Thomas; Unruh, Oliver; Algermissen, Stephan; Pohl, Martin

    2016-08-01

    The fuel consumption of future civil aircraft needs to be reduced because of the CO2 restrictions declared by the European Union. A consequent lightweight design and a new engine concept called counter-rotating open rotor are seen as key technologies in the attempt to reach this ambitious goals. Bearing in mind that counter-rotating open rotor engines emit very high sound pressures at low frequencies and that lightweight structures have a poor transmission loss in the lower frequency range, these key technologies raise new questions in regard to acoustic passenger comfort. One of the promising solutions for the reduction of sound pressure levels inside the aircraft cabin are active sound and vibration systems. So far, active concepts have rarely been investigated for a counter-rotating open rotor pressure excitation on complex airframe structures. Hence, the state of the art is augmented by the preliminary study presented in this paper. The study shows how an active vibration control system can influence the sound transmission of counter-rotating open rotor noise through a complex airframe structure into the cabin. Furthermore, open questions on the way towards the realisation of an active control system are addressed. In this phase, an active feedforward control system is investigated in a fully equipped Dornier 728 experimental prototype aircraft. In particular, the sound transmission through the airframe, the coupling of classical actuators (inertial and piezoelectric patch actuators) into the structure and the performance of the active vibration control system with different error sensors are investigated. It can be shown that the active control system achieves a reduction up to 5 dB at several counter-rotating open rotor frequencies but also that a better performance could be achieved through further optimisations.

  14. [Summary of ongoing activities on environmental noise and health at the WHO regional office for Europe].

    PubMed

    Héroux, M E; Braubach, M; Dramac, D; Korol, N; Paunovic, E; Zastenskaya, I

    2014-01-01

    The environmental noise is an important public health issue, according to recent assessment of the burden of diseases among environmental health risk factors in order of importance the environmental noise occupies the second place after air pollution. The World Health Organization (WHO) for the first time published its public health recommendations for the environmental noise in 1999 in the "WHO Guidelines for Community Noise (1999)". These recommendations found their development in WHO Night Noise Guidelines for Europe" (2009). From then onward there have been published new important data on the impact of the environmental noise on the health, that stipulated the revision of existing guidelines. Furthermore, both in the European Union (EU) Directive 2002/49/ EC and the Parma Declaration from 2010 there was pointed out the importance of renewal environmental noise recommendations. Responding to appearing interrogation, WHO Regional Office for Europe has recently initiated the process of the elaboration of new guiding principles known as "WHO Environmental Noise Guidelines for the European Region". The Guidelines will include a systematic review of most critical or important health consequences and also concentrate on health benefits of measures for the reducing noise levels. The Guidelines will consider noise coming from various noise sources such as aircraft, railroad, personal electronic devices and wind turbines. The Guidelines will also consider the particularity of such accommodations as residences, hospitals, and educational facilities. The work in the mentioned spheres is ongoing and the revised Guidelines are expected to be published in mid-2015. The Guidelines will provide up-to-date information on the health risks related to the environmental noise and evidence-based recommendations in order to support for WHO Member States in their efforts to prevent of the excessive noise and the struggle with their negative impact. PMID:25831923

  15. [Summary of ongoing activities on environmental noise and health at the WHO regional office for Europe].

    PubMed

    Héroux, M E; Braubach, M; Dramac, D; Korol, N; Paunovic, E; Zastenskaya, I

    2014-01-01

    The environmental noise is an important public health issue, according to recent assessment of the burden of diseases among environmental health risk factors in order of importance the environmental noise occupies the second place after air pollution. The World Health Organization (WHO) for the first time published its public health recommendations for the environmental noise in 1999 in the "WHO Guidelines for Community Noise (1999)". These recommendations found their development in WHO Night Noise Guidelines for Europe" (2009). From then onward there have been published new important data on the impact of the environmental noise on the health, that stipulated the revision of existing guidelines. Furthermore, both in the European Union (EU) Directive 2002/49/ EC and the Parma Declaration from 2010 there was pointed out the importance of renewal environmental noise recommendations. Responding to appearing interrogation, WHO Regional Office for Europe has recently initiated the process of the elaboration of new guiding principles known as "WHO Environmental Noise Guidelines for the European Region". The Guidelines will include a systematic review of most critical or important health consequences and also concentrate on health benefits of measures for the reducing noise levels. The Guidelines will consider noise coming from various noise sources such as aircraft, railroad, personal electronic devices and wind turbines. The Guidelines will also consider the particularity of such accommodations as residences, hospitals, and educational facilities. The work in the mentioned spheres is ongoing and the revised Guidelines are expected to be published in mid-2015. The Guidelines will provide up-to-date information on the health risks related to the environmental noise and evidence-based recommendations in order to support for WHO Member States in their efforts to prevent of the excessive noise and the struggle with their negative impact.

  16. Evaluation of noise associated with geothermal-development activities. Final report, July 31, 1979-April 30, 1982

    SciTech Connect

    Long, M.; Stern, R.

    1982-01-01

    This report was prepared for the purpose of ascertaining the current state of noise generation, suppression, and mitigation techniques associated with geothermal development. A description of the geothermal drilling process is included as well as an overview of geothermal development activities in the United States. Noise sources at the well site, along geothermal pipelines, and at the power plants are considered. All data presented are measured values by workers in the field and by Marshall Long/Acoustics. One particular well site was monitored for a period of 55 continuous days, and includes all sources of noise from the time that the drilling rig was brought in until the time that it was moved off site. A complete log of events associated with the drilling process is correlated with the noise measurements including production testing of the completed well. Data are also presented which compare measured values of geothermal noise with federal, state, county, and local standards. A section on control of geothermal noise is also given. Volume I of this document presents summary information.

  17. Performance benefits of adaptive, multimicrophone, interference-canceling systems in everyday environments

    NASA Astrophysics Data System (ADS)

    Desloge, Joseph G.; Zimmer, Martin J.; Zurek, Patrick M.

    2001-05-01

    Adaptive multimicrophone systems are currently used for a variety of noise-cancellation applications (such as hearing aids) to preserve signals arriving from a particular (target) direction while canceling other (jammer) signals in the environment. Although the performance of these systems is known to degrade with increasing reverberation, there are few measurements of adaptive performance in everyday reverberant environments. In this study, adaptive performance was compared to that of a simple, nonadaptive cardioid microphone to determine a measure of adaptive benefit. Both systems used recordings (at an Fs of 22050 Hz) from the same two omnidirectional microphones, which were separated by 1 cm. Four classes of environment were considered: outdoors, household, parking garage, and public establishment. Sources were either environmental noises (e.g., household appliances, restaurant noise) or a controlled noise source. In all situations, no target was present (i.e., all signals were jammers) to obtain maximal jammer cancellation. Adaptive processing was based upon the Griffiths-Jim generalized sidelobe canceller using filter lengths up to 400 points. Average intelligibility-weighted adaptive benefit levels at a source distance of 1 m were, at most, 1.5 dB for public establishments, 2 dB for household rooms and the parking garage, and 3 dB outdoors. [Work supported by NIOSH.

  18. Numerical modeling of multi-mode active control of turbofan tonal noise using a boundary element method

    NASA Astrophysics Data System (ADS)

    Ireland, Laralee Gordon

    A numerical model was developed to investigate the possibility of implementing active control (ANC) to minimize noise radiation from high-bypass turbofan engines. Previous experimental work on the NASA Glenn Research Center active noise control fan (ANCF) was encouraging, but the question remained whether the modal approach investigated could be effective on real engines. The engine model developed for this research project uses an indirect boundary element method, implemented with Sysnoise, and a multi-mode Newton's algorithm, implemented with MATLAB(TM), to simulate the active control. Noise from the inlet was targeted. Both the experimental and numerical results based on the NASA ANCF simplified cylindrical engine geometry indicate overall reductions in the m = 2 component of the noise. Reductions obtained at the numerical sensor rings range from 17 dB to 63 dB and at a plane in the duct inlet, -8 dB to 33 dB. Rings mounted on the inlet duct are unable to accurately predict the total reduction of the inlet field, but the controller is still able to effectively reduce the total acoustic field. Generally, one sensor ring and one actuator ring per propagating mode were necessary to control the inlet field. At frequencies close to the cut-off frequency of a mode, an additional sensor and actuator ring were needed to adequately control the inlet field due to the evanescent mode. A more realistic, but still axisymmetric, engine geometry based on the GE CF6-80C engine was developed and the same algorithm used. Reductions obtained at the sensor rings range from 4 dB to 56 dB and at the duct inlet plane, from 12 dB to 26 dB. The overall far field noise radiation from the engine remained unchanged (0.4 dB) or decreased slightly (3.6 dB). The inlet noise was controlled at all frequencies but the noise from the exhaust was increased. The effect of inlet control on the exhaust radiation suggests the need for a controller that targets both the inlet and exhaust noise

  19. Relationship between auditory intensity discrimination in noise and olivocochlear efferent system activity in humans.

    PubMed

    Micheyl, C; Perrot, X; Collet, L

    1997-08-01

    Recent physiological data in animals suggest a role of the medial olivocochlear system (MOCS) in auditory intensity discrimination in noise. In this study, the existence of statistical relationships between intensity difference limens (IDLs) and MOCS functioning was tested in humans. IDLs were measured in conditions of quiet and of ipsilateral, contralateral, and dichotic noise. MOCS functioning was assessed through the contralateral evoked otoacoustic emission (EOAE) amplitude attenuation effect. A first finding was that IDLs measured in the presence of ipsilateral noise were reduced when contralateral noise was added. Furthermore, the observed shift in IDL appeared to be significantly correlated to the contralateral EOAE amplitude attenuation effect. These results support the hypothesis that MOCS functioning plays a role in intensity discrimination in dichotic noise in humans.

  20. Passive magnetic field cancellation device by multiple high-Tc superconducting coils

    NASA Astrophysics Data System (ADS)

    Gu, C.; Zou, S.; Han, Z.; Qu, T.-M.

    2010-04-01

    A passive magnetic field cancellation device (PMFCD) is designed. The PMFCD could automatically cancel the field as an active cancellation system did; however it requires no power sources and feedback systems. The capability of the PMFCD is based on the principle that a closed loop can resist flux variation and keep the flux constant inside. The closed loop in the PMFCD is formed by connecting two pairs of high temperature superconductor Helmholtz coils with different radii in series. More important thing is that the ratio of the radius and the turn number between the coils has to satisfy a number of conditions, with which 100% cancellation can be reached. Theoretical methods to obtain the turn number ratio and radius ratio are the major part of the paper. Numerical simulation was followed, aiming to evaluate field distribution under a cancellation state and correct the theoretical values.

  1. Investigation of the potential effects of underwater noise from petroleum-industry activities on feeding humpback whale behavior. Final report

    SciTech Connect

    Malme, C.I.; Miles, P.R.; Tyack, P.; Clark, C.W.; Bird, J.E.

    1985-06-01

    An investigation was made of the potential effects of underwater noise from petroleum-industry activities on the behavior of feeding humpback whales in Frederick Sound and Stephens Passage, Alaska in August, 1984. Test sounds were a 100 cu. in. air gun and playbacks of recorded drillship, drilling platform, production platform, semi-submersible drill rig, and helicopter fly-over noise. Sound source levels and acoustic propagation losses were measured. The movement patterns of whales were determined by observations of whale-surfacing positions.

  2. 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…

  3. 34 CFR 674.59 - Cancellation for military service.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 34 Education 3 2014-07-01 2014-07-01 false Cancellation for military service. 674.59 Section 674... Cancellation for military service. (a) Cancellation on a Defense loan. (1) An institution must cancel up to 50... fraction of a year beyond a complete year of service, does not qualify for military cancellation....

  4. 34 CFR 674.59 - Cancellation for military service.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 34 Education 3 2012-07-01 2012-07-01 false Cancellation for military service. 674.59 Section 674... Cancellation for military service. (a) Cancellation on a Defense loan. (1) An institution must cancel up to 50... fraction of a year beyond a complete year of service, does not qualify for military cancellation....

  5. 34 CFR 674.59 - Cancellation for military service.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 34 Education 3 2013-07-01 2013-07-01 false Cancellation for military service. 674.59 Section 674... Cancellation for military service. (a) Cancellation on a Defense loan. (1) An institution must cancel up to 50... fraction of a year beyond a complete year of service, does not qualify for military cancellation....

  6. Transcript degradation and noise of small RNA-controlled genes in a switch activated network in Escherichia coli.

    PubMed

    Arbel-Goren, Rinat; Tal, Asaf; Parasar, Bibudha; Dym, Alvah; Costantino, Nina; Muñoz-García, Javier; Court, Donald L; Stavans, Joel

    2016-08-19

    Post-transcriptional regulatory processes may change transcript levels and affect cell-to-cell variability or noise. We study small-RNA downregulation to elucidate its effects on noise in the iron homeostasis network of Escherichia coli In this network, the small-RNA RyhB undergoes stoichiometric degradation with the transcripts of target genes in response to iron stress. Using single-molecule fluorescence in situ hybridization, we measured transcript numbers of the RyhB-regulated genes sodB and fumA in individual cells as a function of iron deprivation. We observed a monotonic increase of noise with iron stress but no evidence of theoretically predicted, enhanced stoichiometric fluctuations in transcript numbers, nor of bistable behavior in transcript distributions. Direct detection of RyhB in individual cells shows that its noise is much smaller than that of these two targets, when RyhB production is significant. A generalized two-state model of bursty transcription that neglects RyhB fluctuations describes quantitatively the dependence of noise and transcript distributions on iron deprivation, enabling extraction of in vivo RyhB-mediated transcript degradation rates. The transcripts' threshold-linear behavior indicates that the effective in vivo interaction strength between RyhB and its two target transcripts is comparable. Strikingly, the bacterial cell response exhibits Fur-dependent, switch-like activation instead of a graded response to iron deprivation. PMID:27085802

  7. Transcript degradation and noise of small RNA-controlled genes in a switch activated network in Escherichia coli.

    PubMed

    Arbel-Goren, Rinat; Tal, Asaf; Parasar, Bibudha; Dym, Alvah; Costantino, Nina; Muñoz-García, Javier; Court, Donald L; Stavans, Joel

    2016-08-19

    Post-transcriptional regulatory processes may change transcript levels and affect cell-to-cell variability or noise. We study small-RNA downregulation to elucidate its effects on noise in the iron homeostasis network of Escherichia coli In this network, the small-RNA RyhB undergoes stoichiometric degradation with the transcripts of target genes in response to iron stress. Using single-molecule fluorescence in situ hybridization, we measured transcript numbers of the RyhB-regulated genes sodB and fumA in individual cells as a function of iron deprivation. We observed a monotonic increase of noise with iron stress but no evidence of theoretically predicted, enhanced stoichiometric fluctuations in transcript numbers, nor of bistable behavior in transcript distributions. Direct detection of RyhB in individual cells shows that its noise is much smaller than that of these two targets, when RyhB production is significant. A generalized two-state model of bursty transcription that neglects RyhB fluctuations describes quantitatively the dependence of noise and transcript distributions on iron deprivation, enabling extraction of in vivo RyhB-mediated transcript degradation rates. The transcripts' threshold-linear behavior indicates that the effective in vivo interaction strength between RyhB and its two target transcripts is comparable. Strikingly, the bacterial cell response exhibits Fur-dependent, switch-like activation instead of a graded response to iron deprivation.

  8. Active Control of Multi-Tonal Noise with Reference Generator Based on On-Line Frequency Estimation

    NASA Astrophysics Data System (ADS)

    KIM, S.; PARK, Y.

    1999-10-01

    In this paper, a novel active noise control (ANC) structure with a frequency estimator is proposed for systems with multi-tonal noise. The conventional feedforward ANC algorithms need a measured reference signal to calculate the gradient of the squared error and filter coefficients. For ANC systems applied to aircraft or passenger ships, which reference signals are usually measured are so far from seats where engines from the main part of controllers is placed that the scheme might be difficult to implement or very costly. Feedback ANC algorithms which do not require a measure of reference signals, use error signals alone to update the filter and are usually sensitive to measurement noise and unexpected transient noise such as a sneeze, clapping of hands and so on.The proposed algorithm, which estimates frequencies of the multi-tonal noise in real time using adaptive notch filter (ANF), improves convergence rate, threshold SNR and computational efficiency compared with the conventional ones. The reference signal needed for the feedforward control is not measured directly, but is generated with the estimated frequencies. It has a strong similarity to the conventional IMC-based feedback control because the reference is generated from the error signal in both cases. The proposed ANC algorithm is compared with the conventional IMC-based feedback control algorithm.Cascade ANF, which has a low computational burden, is used to implement the ANC system in real time. Experiments for verifying efficacy of the proposed algorithm are carried out in the laboratory.

  9. Noise levels in the learning-teaching activities in a dental medicine school

    NASA Astrophysics Data System (ADS)

    Matos, Andreia; Carvalho, Antonio P. O.; Fernandes, Joao C. S.

    2002-11-01

    The noise levels made by different clinical handpieces and laboratory engines are considered to be the main descriptors of acoustical comfort in learning spaces in a dental medicine school. Sound levels were measured in five types of classrooms and teaching laboratories at the University of Porto Dental Medicine School. Handpiece noise measurements were made while instruments were running free and during operations with cutting tools (tooth, metal, and acrylic). Noise levels were determined using a precision sound level meter, which was positioned at ear level and also at one-meter distance from the operator. Some of the handpieces were brand new and the others had a few years of use. The sound levels encountered were between 60 and 99 dB(A) and were compared with the noise limits in A-weighted sound pressure level for mechanical equipments installed in educational buildings included in the Portuguese Noise Code and in other European countries codes. The daily personal noise exposure levels (LEP,d) of the students and professors were calculated to be between 85 and 90 dB(A) and were compared with the European legal limits. Some noise limits for this type of environment are proposed and suggestions for the improvement of the acoustical environment are given.

  10. Lévy stable noise-induced transitions: stochastic resonance, resonant activation and dynamic hysteresis

    NASA Astrophysics Data System (ADS)

    Dybiec, Bartłomiej; Gudowska-Nowak, Ewa

    2009-05-01

    A standard approach to analysis of noise-induced effects in stochastic dynamics assumes a Gaussian character of the noise term describing interaction of the analyzed system with its complex surroundings. An additional assumption about the existence of timescale separation between the dynamics of the measured observable and the typical timescale of the noise allows external fluctuations to be modeled as temporally uncorrelated and therefore white. However, in many natural phenomena the assumptions concerning the above mentioned properties of 'Gaussianity' and 'whiteness' of the noise can be violated. In this context, in contrast to the spatiotemporal coupling characterizing general forms of non-Markovian or semi-Markovian Lévy walks, so called Lévy flights correspond to the class of Markov processes which can still be interpreted as white, but distributed according to a more general, infinitely divisible, stable and non-Gaussian law. Lévy noise-driven non-equilibrium systems are known to manifest interesting physical properties and have been addressed in various scenarios of physical transport exhibiting a superdiffusive behavior. Here we present a brief overview of our recent investigations aimed at understanding features of stochastic dynamics under the influence of Lévy white noise perturbations. We find that the archetypal phenomena of noise-induced ordering are robust and can be detected also in systems driven by memoryless, non-Gaussian, heavy-tailed fluctuations with infinite variance.

  11. Use of noise attenuation modeling in managing missile motor detonation activities.

    PubMed

    McFarland, Michael J; Watkins, Jeffrey W; Kordich, Micheal M; Pollet, Dean A; Palmer, Glenn R

    2004-03-01

    The Sound Intensity Prediction System (SIPS) and Blast Operation Overpressure Model (BOOM) are semiempirical sound models that are employed by the Utah Test and Training Range (UTTR) to predict whether noise levels from the detonation of large missile motors will exceed regulatory thresholds. Field validation of SIPS confirmed that the model was effective in limiting the number of detonations of large missile motors that could potentially result in a regulatory noise exceedance. Although the SIPS accurately predicted the impact of weather on detonation noise propagation, regulators have required that the more conservative BOOM model be employed in conjunction with SIPS in evaluating peak noise levels in populated areas. By simultaneously considering the output of both models, in 2001, UTTR detonated 104 missile motors having net explosive weights (NEW) that ranged between 14,960 and 38,938 lb without a recorded public noise complaint. Based on the encouraging results, the U.S. Department of Defense is considering expanding the application of these noise models to support the detonation of missile motors having a NEW of 81,000 lb. Recent modeling results suggest that, under appropriate weather conditions, missile motors containing up to 96,000 lb NEW can be detonated at the UTTR without exceeding the regulatory noise limit of 134 decibels (dB).

  12. Baseline acoustic levels of the NASA Active Noise Control Fan rig

    NASA Technical Reports Server (NTRS)

    Sutliff, Daniel L.; Heidelberg, Laurence J.; Elliott, David M.; Nallasamy, M.

    1996-01-01

    Extensive measurements of the spinning acoustic mode structure in the NASA 48 inch Active Noise Control Fan (ANCF) test rig have been taken. A continuously rotating microphone rake system with a least-squares data reduction technique was employed to measure these modes in the inlet and exhaust. Farfield directivity patterns in an anechoic environment were also measured at matched corrected rotor speeds. Several vane counts and spacings were tested over a range of rotor speeds. The Eversman finite element radiation code was run with the measured in-duct modes as input and the computed farfield results were compared to the experimentally measured directivity pattern. The experimental data show that inlet spinning mode measurements can be made very accurately. Exhaust mode measurements may have wake interference, but the least-squares reduction does a good job of rejecting the non-acoustic pressure. The Eversman radiation code accurately extrapolates the farfield levels and directivity pattern when all in-duct modes are included.

  13. Computationally efficient algorithm for high sampling-frequency operation of active noise control

    NASA Astrophysics Data System (ADS)

    Rout, Nirmal Kumar; Das, Debi Prasad; Panda, Ganapati

    2015-05-01

    In high sampling-frequency operation of active noise control (ANC) system the length of the secondary path estimate and the ANC filter are very long. This increases the computational complexity of the conventional filtered-x least mean square (FXLMS) algorithm. To reduce the computational complexity of long order ANC system using FXLMS algorithm, frequency domain block ANC algorithms have been proposed in past. These full block frequency domain ANC algorithms are associated with some disadvantages such as large block delay, quantization error due to computation of large size transforms and implementation difficulties in existing low-end DSP hardware. To overcome these shortcomings, the partitioned block ANC algorithm is newly proposed where the long length filters in ANC are divided into a number of equal partitions and suitably assembled to perform the FXLMS algorithm in the frequency domain. The complexity of this proposed frequency domain partitioned block FXLMS (FPBFXLMS) algorithm is quite reduced compared to the conventional FXLMS algorithm. It is further reduced by merging one fast Fourier transform (FFT)-inverse fast Fourier transform (IFFT) combination to derive the reduced structure FPBFXLMS (RFPBFXLMS) algorithm. Computational complexity analysis for different orders of filter and partition size are presented. Systematic computer simulations are carried out for both the proposed partitioned block ANC algorithms to show its accuracy compared to the time domain FXLMS algorithm.

  14. Reduction of noise in the beta camera for low activity applications

    SciTech Connect

    Ljunggren, K.L.; Strand, S.E. . Radiation Physics Dept.)

    1994-08-01

    The Beta-camera'' is a position sensitive light detector based on a photocathode, microchannel plates and a resistive anode adapted with a plastic scintillator (0.3 mm NE102A). The light from the scintillator is collected in a manner similar to conventional scintillation (Anger-type) cameras. The Beta-camera'' used in the past in the authors laboratory for imaging of biomedical samples, has a noise level of about 50 counts per second. It is desirable to reduce this noise, in order to improve the detectability in the biological samples. Accordingly in this paper, the authors report on a coincidence technique that reduces the noise level to almost zero.

  15. Active noise reduction in aviation helmets during a military jet trainer test flight.

    PubMed

    Pääkkönen, R; Kuronen, P; Korteoja, M

    2001-01-01

    Cockpit noise measurements were carried out in a two-seat jet trainer. For the continuous time and frequency analyses a two-channel tape-recording system was constructed of two miniature microphones connected through an amplifier to a digital tape-recorder. The analysed and averaged noise exposure including radio communication was 80-81 dB when the ANC system was on and 84-89 dB when the ANC system was off. For the conventional flight helmet the same noise exposure was 86 dB, and the noise exposure in the cockpit was 104-106 dB. The effect of the ANC system on the averaged noise exposure (L(Aeq8min)) was an improvement of 4-8 dB over the noise attenuation of the same helmets when the ANC system was off. Both ANC systems worked properly during the test flights. No severe ringing or voice circulation was found except during extreme vibration.

  16. Active hearing protectors: Prospects for improving speech intelligibility while maintaining noise reduction and audibility of warning alarms

    NASA Astrophysics Data System (ADS)

    Brammer, Anthony J.; Peterson, Donald R.; Cherniack, Martin G.; Gullapalli, Subhash

    2005-04-01

    Users of hearing protection devices (HPDs), including the communication headsets and helmets commonly worn by aircraft air and ground crews, emergency responders, military personnel, and persons in industry working in hostile environments, have long complained that HPDs interfere with their ability to communicate and to hear warning alarms. There thus appears to be a need for additional specialized HPDs designed specifically for these situations. The technology of active noise control together with signal processing applied to the communication channel of the HPD may provide a potential solution. The combination could improve noise reduction at low frequencies and enhance the intelligibility of speech reproduced by the communication channel, while maintaining the overall noise reduction within occupational exposure requirements, and assisting the perception of external warning alarms. A strategy for achieving these goals using an active circumaural earmuff equipped with sub-band processing will be described, in which parallel controllers optimize the speech signal-to-noise ratio in bands that contribute most to intelligibility. The perception of a tonal alarm is assisted by binaural feed through to the earphones, within the constraints imposed by occupational exposure limits, and by sub-band processing to reduce the upward spread of masking.

  17. 29 CFR 4.190 - Contract cancellation.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., the contract is subject upon written notice to cancellation by the contracting agency, whereupon the... contract is similarly subject upon written notice to immediate cancellation by the contracting agency and... in paragraph (a). Such contract is without warrant of law and has no force and effect and is void...

  18. 25 CFR 214.19 - Cancellation.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 25 Indians 1 2014-04-01 2014-04-01 false Cancellation. 214.19 Section 214.19 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF OSAGE RESERVATION LANDS, OKLAHOMA, FOR MINING, EXCEPT OIL AND GAS § 214.19 Cancellation. When a lessee makes application for...

  19. 25 CFR 213.40 - Cancellations.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 25 Indians 1 2013-04-01 2013-04-01 false Cancellations. 213.40 Section 213.40 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF RESTRICTED LANDS OF MEMBERS OF FIVE CIVILIZED TRIBES, OKLAHOMA, FOR MINING Operations § 213.40 Cancellations. (a) When, in the...

  20. 25 CFR 214.19 - Cancellation.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 25 Indians 1 2012-04-01 2011-04-01 true Cancellation. 214.19 Section 214.19 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF OSAGE RESERVATION LANDS, OKLAHOMA, FOR MINING, EXCEPT OIL AND GAS § 214.19 Cancellation. When a lessee makes application for...

  1. 25 CFR 213.40 - Cancellations.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 25 Indians 1 2014-04-01 2014-04-01 false Cancellations. 213.40 Section 213.40 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF RESTRICTED LANDS OF MEMBERS OF FIVE CIVILIZED TRIBES, OKLAHOMA, FOR MINING Operations § 213.40 Cancellations. (a) When, in the...

  2. 25 CFR 213.40 - Cancellations.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 25 Indians 1 2012-04-01 2011-04-01 true Cancellations. 213.40 Section 213.40 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF RESTRICTED LANDS OF MEMBERS OF FIVE CIVILIZED TRIBES, OKLAHOMA, FOR MINING Operations § 213.40 Cancellations. (a) When, in the...

  3. 25 CFR 214.19 - Cancellation.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 25 Indians 1 2011-04-01 2011-04-01 false Cancellation. 214.19 Section 214.19 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF OSAGE RESERVATION LANDS, OKLAHOMA, FOR MINING, EXCEPT OIL AND GAS § 214.19 Cancellation. When a lessee makes application for...

  4. 25 CFR 214.19 - Cancellation.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 25 Indians 1 2013-04-01 2013-04-01 false Cancellation. 214.19 Section 214.19 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF OSAGE RESERVATION LANDS, OKLAHOMA, FOR MINING, EXCEPT OIL AND GAS § 214.19 Cancellation. When a lessee makes application for...

  5. 25 CFR 227.28 - Cancellations.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Cancellations. 227.28 Section 227.28 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF CERTAIN LANDS IN WIND RIVER INDIAN RESERVATION, WYOMING, FOR OIL AND GAS MINING Operations § 227.28 Cancellations. Leases shall...

  6. 25 CFR 227.28 - Cancellations.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 25 Indians 1 2012-04-01 2011-04-01 true Cancellations. 227.28 Section 227.28 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF CERTAIN LANDS IN WIND RIVER INDIAN RESERVATION, WYOMING, FOR OIL AND GAS MINING Operations § 227.28 Cancellations. Leases shall...

  7. 25 CFR 227.28 - Cancellations.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 25 Indians 1 2011-04-01 2011-04-01 false Cancellations. 227.28 Section 227.28 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF CERTAIN LANDS IN WIND RIVER INDIAN RESERVATION, WYOMING, FOR OIL AND GAS MINING Operations § 227.28 Cancellations. Leases shall...

  8. 25 CFR 227.28 - Cancellations.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 25 Indians 1 2013-04-01 2013-04-01 false Cancellations. 227.28 Section 227.28 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF CERTAIN LANDS IN WIND RIVER INDIAN RESERVATION, WYOMING, FOR OIL AND GAS MINING Operations § 227.28 Cancellations. Leases shall...

  9. 25 CFR 227.28 - Cancellations.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 25 Indians 1 2014-04-01 2014-04-01 false Cancellations. 227.28 Section 227.28 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF CERTAIN LANDS IN WIND RIVER INDIAN RESERVATION, WYOMING, FOR OIL AND GAS MINING Operations § 227.28 Cancellations. Leases shall...

  10. 34 CFR 674.52 - Cancellation procedures.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... borrower's loan deferment under § 674.34(c) to run concurrently with any period for which cancellation... run concurrently with any period for which a cancellation under §§ 674.53, 674.56, 674.57, or 674.58 is granted. (e) National community service. No borrower who has received a benefit under subtitle...

  11. 25 CFR 23.53 - Cancellation.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Cancellation. 23.53 Section 23.53 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR HUMAN SERVICES INDIAN CHILD WELFARE ACT General and Uniform Grant Administration Provisions and Requirements § 23.53 Cancellation. (a) The grants officer may...

  12. 43 CFR 3601.62 - Cancellation procedure.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) MINERAL MATERIALS DISPOSAL Mineral Materials Disposal; General Provisions Contract and Permit Cancellation § 3601.62 Cancellation procedure. (a... notice under paragraph (a) of this section, or if delivery of the notice is refused, or not completed...

  13. 36 CFR 223.116 - Cancellation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... DISPOSAL OF NATIONAL FOREST SYSTEM TIMBER Timber Sale Contracts Contract Administration § 223.116 Cancellation. (a) Timber sale contracts and permits may be canceled: (1) For serious or continued violation of... the value of the timber remaining to be cut is diminished materially because of catastrophic...

  14. 7 CFR 1942.12 - Loan cancellation.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... REGULATIONS (CONTINUED) ASSOCIATIONS Community Facility Loans § 1942.12 Loan cancellation. Loans which have... Development Manager or State Director may prepare and execute Form Rural Development 1940-10, Cancellation of... disbursement has been received or is subsequently received in the Area Office, the Rural Development...

  15. 34 CFR 674.52 - Cancellation procedures.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... covered under the Family and Medical Leave Act of 1993 (FMLA) (29 U.S.C. 2601, et seq.), the borrower... cancellation based on a claim of simultaneous employment as a nurse or medical technician in two or more... of title I of the National and Community Service Act of 1990 may receive a cancellation under......

  16. 43 CFR 3601.62 - Cancellation procedure.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) MINERAL MATERIALS DISPOSAL Mineral Materials Disposal; General Provisions Contract and Permit Cancellation § 3601.62 Cancellation procedure. (a... notice under paragraph (a) of this section, or if delivery of the notice is refused, or not completed...

  17. 44 CFR 206.376 - Loan cancellation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... HOMELAND SECURITY DISASTER ASSISTANCE FEDERAL DISASTER ASSISTANCE Community Disaster Loans § 206.376 Loan cancellation. (a) FEMA shall cancel repayment of all or part of a Special Community Disaster Loan to the extent... Special Community Disaster loans issued from the dates of enactment of Public Law 109-88 and Public...

  18. 44 CFR 206.376 - Loan cancellation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... HOMELAND SECURITY DISASTER ASSISTANCE FEDERAL DISASTER ASSISTANCE Community Disaster Loans § 206.376 Loan cancellation. (a) FEMA shall cancel repayment of all or part of a Special Community Disaster Loan to the extent... Special Community Disaster loans issued from the dates of enactment of Public Law 109-88 and Public...

  19. 44 CFR 206.366 - Loan cancellation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... HOMELAND SECURITY DISASTER ASSISTANCE FEDERAL DISASTER ASSISTANCE Community Disaster Loans § 206.366 Loan cancellation. (a) Policies. (1) FEMA shall cancel repayment of all or part of a Community Disaster Loan to the... incurred for general government purposes, such as police and fire protection, trash collection,...

  20. 44 CFR 206.366 - Loan cancellation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... HOMELAND SECURITY DISASTER ASSISTANCE FEDERAL DISASTER ASSISTANCE Community Disaster Loans § 206.366 Loan cancellation. (a) Policies. (1) FEMA shall cancel repayment of all or part of a Community Disaster Loan to the... incurred for general government purposes, such as police and fire protection, trash collection,...

  1. 44 CFR 206.376 - Loan cancellation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... HOMELAND SECURITY DISASTER ASSISTANCE FEDERAL DISASTER ASSISTANCE Community Disaster Loans § 206.376 Loan cancellation. (a) FEMA shall cancel repayment of all or part of a Special Community Disaster Loan to the extent... Special Community Disaster loans issued from the dates of enactment of Public Law 109-88 and Public...

  2. 44 CFR 206.366 - Loan cancellation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... HOMELAND SECURITY DISASTER ASSISTANCE FEDERAL DISASTER ASSISTANCE Community Disaster Loans § 206.366 Loan cancellation. (a) Policies. (1) FEMA shall cancel repayment of all or part of a Community Disaster Loan to the... incurred for general government purposes, such as police and fire protection, trash collection,...

  3. 44 CFR 206.366 - Loan cancellation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... HOMELAND SECURITY DISASTER ASSISTANCE FEDERAL DISASTER ASSISTANCE Community Disaster Loans § 206.366 Loan cancellation. (a) Policies. (1) FEMA shall cancel repayment of all or part of a Community Disaster Loan to the... incurred for general government purposes, such as police and fire protection, trash collection,...

  4. 7 CFR 1956.70 - Cancellation.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... REGULATIONS (CONTINUED) DEBT SETTLEMENT Debt Settlement-Farm Loan Programs and Multi-Family Housing § 1956.70 Cancellation. Nonjudgment debts may be canceled in the following instances: (a) With application. The debt or any extension thereof on Farmer Programs debts do not have to be due and payable under the terms...

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

    NASA Astrophysics Data System (ADS)

    Tavossi, Ph. D., Hasson M.

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

  6. Nuclear plant cancellations: causes, costs, and consequences

    SciTech Connect

    Not Available

    1983-04-01

    This study was commissioned in order to help quantify the effects of nuclear plant cancellations on the Nation's electricity prices. This report presents a historical overview of nuclear plant cancellations through 1982, the costs associated with those cancellations, and the reasons that the projects were terminated. A survey is presented of the precedents for regulatory treatment of the costs, the specific methods of cost recovery that were adopted, and the impacts of these decisions upon ratepayers, utility stockholders, and taxpayers. Finally, the report identifies a series of other nuclear plants that remain at risk of canellation in the future, principally as a result of similar demand, finance, or regulatory problems cited as causes of cancellation in the past. The costs associated with these potential cancellations are estimated, along with their regional distributions, and likely methods of cost recovery are suggested.

  7. Modeling of piezoelectric smart structures for active vibration and noise control applications

    NASA Astrophysics Data System (ADS)

    Gopinathan, Senthil V.

    Active vibration control and active structural acoustic control using piezoelectric sensors and actuators have recently emerged as a practical and promising technology. Efficient and accurate modeling of these structures bonded to or embedded with actuators and sensors is needed for efficient design of smart structures. This dissertation addresses the modeling of these structures and the associated control system design technique. Modeling of structures with both laminated and discrete type of actuators and sensors are addressed. For piezoelectric laminates the governing equations of motion are derived using First Order Shear Deformation Theory (FSDT) and for the first time the dynamic response fields inside the laminate are obtained and compared with full elasticity solutions. This comparison brought out the effect of assumptions made with respect to the electric and mechanical fields using FSDT and Classical Laminate Theory (CLT) in previous work. It is expected that this analysis and the interior field estimations would help designers to understand the shortcomings of FSDT in modeling piezoelectric laminates, and help them to adopt this theory properly for use in FE or other numerical models. For discrete patch actuators/sensors, the governing dynamic equation of motion for a plate is derived. The solution to this equation is obtained using a Fourier series method and the effect of passive stiffness and mass on the natural frequency is studied. The studies showed that ignoring the mass and the passive stiffness' of actuators/sensors leads to large errors in estimating the vibration characteristics of the smart plate. A Rayleigh-Ritz (RR) approach is then presented for studying the active vibration and transmitted noise control of a smart plate with discrete piezoelectric patches. Classical laminated plate theory is used to model the composite plate and electro elastic theory is used model the piezoelectric patches. The dynamic equations of motion for the coupled

  8. Dynamic characteristics of an active coastal spreading area using ambient noise measurements—Anchor Bay, Malta

    NASA Astrophysics Data System (ADS)

    Galea, Pauline; D'Amico, Sebastiano; Farrugia, Daniela

    2014-11-01

    Anchor Bay and surrounding regions are located on the northwest coast of the island of Malta, Central Mediterranean. The area is characterized by a coastal cliff environment having an outcropping layer of hard coralline limestone (UCL) resting on a thick (up to 50 m) layer of clays and marls (Blue Clay, BC). This configuration gives rise to coastal instability effects, in particular lateral spreading phenomena and rock falls. Previous and ongoing studies have identified both lateral spreading rates and vertical motions of several millimetres per year. The area is an interesting natural laboratory as coastal detachment processes in a number of different stages can be identified and are easily accessible. We investigate the site dynamic characteristics of this study area by recording ambient noise time-series at more than 30 points, over an area of 0.07 km2, using a portable three-component seismograph. The time-series are processed to give both horizontal-to-vertical spectral ratio graphs (H/V) as well as frequency-dependent polarisation analysis. The H/V graphs illustrate and quantify aspects of site resonance effects due both to underlying geology as well as to mechanical resonance of partly or wholly detached blocks. The polarization diagrams indicate the degree of linearity and predominant directions of vibrational effects. H/V curves closer to the cliff edge show complex responses at higher frequencies, characteristic of the dynamic behaviour of individual detached blocks. Particle motion associated with the higher frequencies shows strongly directional polarization and a high degree of linearity at well-defined frequencies, indicative of normal-mode vibration. The stable plateau areas, on the other hand, show simple, single-peak H/V curves representative of the underlying stratification and no predominant polarization direction. These results, which will be compared with those from other experiments in the area, have important implications for the

  9. Promises and Limitations of RFI Canceling Solutions

    NASA Astrophysics Data System (ADS)

    Fisher, J. R.

    2004-05-01

    Recent years have seen a kindling of interest in signal processing solutions to radio frequency interference (RFI) to astronomical observations. Over a dozen refereed papers and several dozen conference presentations on the subject are now in the astronomical and engineering literature. This work builds on several decades of signal processing development in the fields of acoustics and communications for which there are a number of standard texts. Radio astronomy has the unique requirement that interference must be suppressed below very low detection thresholds before the scientific results of observations can be considered reliable. These detection thresholds are several orders of magnitude lower than is typical of communications signal levels. Initial trials of coherent cancellation of TV and satellite signals and blanking of pulsed interference, such as radar and aircraft signals, are encouraging, but the signal processing power required for useful bandwidths is sobering. Simultaneous cancellation of many signals and compensation for multi-path propagation effects of distant transmitters add to the processing load and are challenges that remain to be tackled. Spectrum management is becoming increasingly complex with greater emphasis on spectrum sharing in the time and spacial domains. This requires a better understanding of long-distance propagation effects and the techniques and economics of signal separation to guide the protection of the scientific use of the radio spectrum. The traditional concept of frequency allocations will be only one aspect of spectrum management in the coming years. Active users of the spectrum will expect us to devote some of our engineering and managerial resources to spectrum sharing agreements, Hence, we need to continually build a firm technical footing upon which to base our negotiating positions. The NRAO is operated for the National Science Foundation (NSF) by Associated Universities, Inc. (AUI), under a cooperative agreement.

  10. 78 FR 48456 - Notice of Cancellation of Customs Broker Licenses

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-08

    ... permits of certain customs brokers are being cancelled without prejudice. SUPPLEMENTARY INFORMATION... following customs broker licenses are cancelled without prejudice. ] Last/company name First name License...

  11. Disruption of prosomes by some bivalent metal ions results in the loss of their multicatalytic proteinase activity and cancels the nuclease resistance of prosomal RNA.

    PubMed Central

    Nothwang, H G; Coux, O; Bey, F; Scherrer, K

    1992-01-01

    Prosomes are ribonucleoprotein particles constituted by a variable set of about 20 proteins found associated with untranslated mRNA. In addition, they contain a small RNA, the presence of which has been an issue of controversy for a long time. The intact particles have a multicatalytic proteinase (MCP) activity and are very stable; we have never observed autodigestion of the particle by its intrinsic proteinase activity. Surprisingly it was found that Zn2+ and Cu2+ ions at concentrations of 0.1-1 mM disrupt the prosome particles isolated from HeLa cells and duck erythroblasts and abolish instantaneously its MCP activity, without altering the two-dimensional electrophoretic pattern of the constituent proteins. Fe2+, however, seems to induce autodegradation rather than dissociation of the prosome constituents. Most interestingly, protein or oligopeptide substrates protect the particle and its proteinase activity from disruption by Zn2+ or Cu2+. Nuclease-digestion assays reveal that the prosomal RNA, which is largely resistant in the intact particle, becomes digestible after dissociation of prosomes by Zn2+. These data give, for the first time, unambiguous proof of the presence of an RNA in the particle. Furthermore, they demonstrate a structure-function relationship between the complex and its enzyme activity, which seems to be based on the particle as an entity and not on the single constituent proteins. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 6. PMID:1445237

  12. Gaps-in-noise detection and gender identification from noise-vocoded vowel segments: Comparing performance of active musicians to non-musicians.

    PubMed

    Donai, Jeremy J; Jennings, Mariah B

    2016-05-01

    This study evaluated performance on a gender identification and temporal resolution task among active musicians and age-matched non-musicians. Brief duration (i.e., 50 and 100 ms) vowel segments produced by four adult male and four adult female speakers were spectro-temporally degraded using various parameters and presented to both groups for gender identification. Gap detection thresholds were measured using the gaps-in-noise (GIN) test. Contrary to the stated hypothesis, a significant difference in gender identification was not observed between the musician and non-musician listeners. A significant difference, however, was observed on the temporal resolution task, with the musician group achieving approximately 2 ms shorter gap detection thresholds on the GIN test compared to the non-musician counterparts. These results provide evidence supporting the potential benefits of musical training on temporal processing abilities, which have implications for the processing of speech in degraded listening environments and the enhanced processing of the fine-grained temporal aspects of the speech signal. The results also support the GIN test as an instrument sensitive to temporal processing differences among active musicians and non-musicians. PMID:27250197

  13. Brillouin scattering self-cancellation.

    PubMed

    Florez, O; Jarschel, P F; Espinel, Y A V; Cordeiro, C M B; Mayer Alegre, T P; Wiederhecker, G S; Dainese, P

    2016-01-01

    The interaction between light and acoustic phonons is strongly modified in sub-wavelength confinement, and has led to the demonstration and control of Brillouin scattering in photonic structures such as nano-scale optical waveguides and cavities. Besides the small optical mode volume, two physical mechanisms come into play simultaneously: a volume effect caused by the strain-induced refractive index perturbation (known as photo-elasticity), and a surface effect caused by the shift of the optical boundaries due to mechanical vibrations. As a result, proper material and structure engineering allows one to control each contribution individually. Here, we experimentally demonstrate the perfect cancellation of Brillouin scattering arising from Rayleigh acoustic waves by engineering a silica nanowire with exactly opposing photo-elastic and moving-boundary effects. This demonstration provides clear experimental evidence that the interplay between the two mechanisms is a promising tool to precisely control the photon-phonon interaction, enhancing or suppressing it. PMID:27283092

  14. Brillouin scattering self-cancellation

    NASA Astrophysics Data System (ADS)

    Florez, O.; Jarschel, P. F.; Espinel, Y. A. V.; Cordeiro, C. M. B.; Mayer Alegre, T. P.; Wiederhecker, G. S.; Dainese, P.

    2016-06-01

    The interaction between light and acoustic phonons is strongly modified in sub-wavelength confinement, and has led to the demonstration and control of Brillouin scattering in photonic structures such as nano-scale optical waveguides and cavities. Besides the small optical mode volume, two physical mechanisms come into play simultaneously: a volume effect caused by the strain-induced refractive index perturbation (known as photo-elasticity), and a surface effect caused by the shift of the optical boundaries due to mechanical vibrations. As a result, proper material and structure engineering allows one to control each contribution individually. Here, we experimentally demonstrate the perfect cancellation of Brillouin scattering arising from Rayleigh acoustic waves by engineering a silica nanowire with exactly opposing photo-elastic and moving-boundary effects. This demonstration provides clear experimental evidence that the interplay between the two mechanisms is a promising tool to precisely control the photon-phonon interaction, enhancing or suppressing it.

  15. Brillouin scattering self-cancellation

    PubMed Central

    Florez, O.; Jarschel, P. F.; Espinel, Y. A. V.; Cordeiro, C. M. B.; Mayer Alegre, T. P.; Wiederhecker, G. S.; Dainese, P.

    2016-01-01

    The interaction between light and acoustic phonons is strongly modified in sub-wavelength confinement, and has led to the demonstration and control of Brillouin scattering in photonic structures such as nano-scale optical waveguides and cavities. Besides the small optical mode volume, two physical mechanisms come into play simultaneously: a volume effect caused by the strain-induced refractive index perturbation (known as photo-elasticity), and a surface effect caused by the shift of the optical boundaries due to mechanical vibrations. As a result, proper material and structure engineering allows one to control each contribution individually. Here, we experimentally demonstrate the perfect cancellation of Brillouin scattering arising from Rayleigh acoustic waves by engineering a silica nanowire with exactly opposing photo-elastic and moving-boundary effects. This demonstration provides clear experimental evidence that the interplay between the two mechanisms is a promising tool to precisely control the photon–phonon interaction, enhancing or suppressing it. PMID:27283092

  16. Background canceling surface alpha detector

    DOEpatents

    MacArthur, Duncan W.; Allander, Krag S.; Bounds, John A.

    1996-01-01

    A background canceling long range alpha detector which is capable of providing output proportional to both the alpha radiation emitted from a surface and to radioactive gas emanating from the surface. The detector operates by using an electrical field between first and second signal planes, an enclosure and the surface or substance to be monitored for alpha radiation. The first and second signal planes are maintained at the same voltage with respect to the electrically conductive enclosure, reducing leakage currents. In the presence of alpha radiation and radioactive gas decay, the signal from the first signal plane is proportional to both the surface alpha radiation and to the airborne radioactive gas, while the signal from the second signal plane is proportional only to the airborne radioactive gas. The difference between these two signals is proportional to the surface alpha radiation alone.

  17. Background canceling surface alpha detector

    DOEpatents

    MacArthur, D.W.; Allander, K.S.; Bounds, J.A.

    1996-06-11

    A background canceling long range alpha detector which is capable of providing output proportional to both the alpha radiation emitted from a surface and to radioactive gas emanating from the surface. The detector operates by using an electrical field between first and second signal planes, an enclosure and the surface or substance to be monitored for alpha radiation. The first and second signal planes are maintained at the same voltage with respect to the electrically conductive enclosure, reducing leakage currents. In the presence of alpha radiation and radioactive gas decay, the signal from the first signal plane is proportional to both the surface alpha radiation and to the airborne radioactive gas, while the signal from the second signal plane is proportional only to the airborne radioactive gas. The difference between these two signals is proportional to the surface alpha radiation alone. 5 figs.

  18. Measurement of hearing aid internal noise.

    PubMed

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

    2010-04-01

    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

  19. 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

  20. Effect of cancellation in neutrinoless double beta decay

    NASA Astrophysics Data System (ADS)

    Mitra, Manimala; Pascoli, Silvia; Wong, Steven

    2014-11-01

    In light of recent experimental results, we carefully analyze the effects of interference in neutrinoless double beta decay, when more than one mechanism is operative. If a complete cancellation is at work, the half-life of the corresponding isotope is infinite, and any constraint on it will automatically be satisfied. We analyze this possibility in detail assuming a cancellation in Xe 136 , and find its implications on the half-life of other isotopes, such as Ge 76 . For definiteness, we consider the role of light and heavy sterile neutrinos. In this case, the effective Majorana mass parameter can be redefined to take into account all contributions, and its value gets suppressed. Hence, larger values of neutrino masses are required for the same half-life. The canonical light neutrino contribution cannot saturate the present limits of half-lives or the positive claim of observation of neutrinoless double beta decay, once the stringent bounds from cosmology are taken into account. For the case of cancellation, where all the sterile neutrinos are heavy, the tension between the results from neutrinoless double beta decay and cosmology becomes more severe. We show that the inclusion of light sterile neutrinos in this setup can resolve this issue. Using the recent results from GERDA, we derive upper limits on the active-sterile mixing angles and compare them with the case of no cancellation. The required values of the mixing angles become larger, if a cancellation is at work. A direct test of destructive interference in Xe 136 is provided by the observation of this process in other isotopes, and we study in detail the correlation between their half-lives. Finally, we discuss the model realizations which can accommodate light and heavy sterile neutrinos and the cancellation. We show that sterile neutrinos of few hundred MeV or GeV mass range, coming

  1. Voice interactive systems in severe noise conditions

    NASA Astrophysics Data System (ADS)

    Steeneken, J. H. M.; Langhout, G.

    1987-02-01

    In a comparison of word recognition performance between human listeners and automatic speech recognition systems (ASR), the human listeners performs much better, especially in severe noise conditions. An application engineer can try to optimize the performance of an ASR system by selecting the optimal noise cancelling microphone and vocabulary for voice input. Some results from a study on the effect of signal handling and vocabulary configuration on the performance of voice input and voice output systems are discussed.

  2. Improved Iterative Parallel Interference Cancellation Receiver for Future Wireless DS-CDMA Systems

    NASA Astrophysics Data System (ADS)

    Morosi, Simone; Fantacci, Romano; Bernacchioni, Andrea

    2005-12-01

    We present a new turbo multiuser detector for turbo-coded direct sequence code division multiple access (DS-CDMA) systems. The proposed detector is based on the utilization of a parallel interference cancellation (PIC) and a bank of turbo decoders. The PIC is broken up in order to perform interference cancellation after each constituent decoder of the turbo decoding scheme. Moreover, in the paper we propose a new enhanced algorithm that provides a more accurate estimation of the signal-to-noise-plus-interference-ratio used in the tentative decision device and in the MAP decoding algorithm. The performance of the proposed receiver is evaluated by means of computer simulations for medium to very high system loads, in AWGN and multipath fading channel, and compared to recently proposed interference cancellation-based iterative MUD, by taking into account the number of iterations and the complexity involved. We will see that the proposed receiver outperforms the others especially for highly loaded systems.

  3. A New Approach to Interference Excision in Radio Astronomy: Real-Time Adaptive Cancellation

    NASA Astrophysics Data System (ADS)

    Barnbaum, Cecilia; Bradley, Richard F.

    1998-11-01

    Every year, an increasing amount of radio-frequency (RF) spectrum in the VHF, UHF, and microwave bands is being utilized to support new commercial and military ventures, and all have the potential to interfere with radio astronomy observations. Such services already cause problems for radio astronomy even in very remote observing sites, and the potential for this form of light pollution to grow is alarming. Preventive measures to eliminate interference through FCC legislation and ITU agreements can be effective; however, many times this approach is inadequate and interference excision at the receiver is necessary. Conventional techniques such as RF filters, RF shielding, and postprocessing of data have been only somewhat successful, but none has been sufficient. Adaptive interference cancellation is a real-time approach to interference excision that has not been used before in radio astronomy. We describe here, for the first time, adaptive interference cancellation in the context of radio astronomy instrumentation, and we present initial results for our prototype receiver. In the 1960s, analog adaptive interference cancelers were developed that obtain a high degree of cancellation in problems of radio communications and radar. However, analog systems lack the dynamic range, noised performance, and versatility required by radio astronomy. The concept of digital adaptive interference cancellation was introduced in the mid-1960s as a way to reduce unwanted noise in low-frequency (audio) systems. Examples of such systems include the canceling of maternal ECG in fetal electrocardiography and the reduction of engine noise in the passenger compartments of automobiles. These audio-frequency applications require bandwidths of only a few tens of kilohertz. Only recently has high-speed digital filter technology made high dynamic range adaptive canceling possible in a bandwidth as large as a few megahertz, finally opening the door to application in radio astronomy. We have

  4. 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.

  5. 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.

  6. Analysis of helicopter blade-vortex interaction noise with application to adaptive-passive and active alleviation methods

    NASA Astrophysics Data System (ADS)

    Tauszig, Lionel Christian

    This study focuses on detection and analysis methods of helicopter blade-vortex interactions (BVI) and applies these methods to two different BVI noise alleviation schemes---an adaptive-passive and an active scheme. A standard free-wake analysis based on relaxation methods is extended in this study to compute high-resolution blade loading, to account for blade-to-blade dissimilarities, and dual vortices when there is negative loading at the blade tips. The free-wake geometry is still calculated on a coarse azimuthal grid and then interpolated to a high-resolution grid to calculate the BVI induced impulsive loading. Blade-to-blade dissimilarities are accounted by allowing the different blades to release their own vortices. A number of BVI detection criteria, including the spherical method (a geometric criterion developed in this thesis) are critically examined. It was determined that high-resolution azimuthal discretization is required in virtually all detection methods except the spherical method which detected the occurrence of parallel BVI even while using a low-resolution azimuthal mesh. Detection methods based on inflow and blade loads were, in addition, found to be sensitive to vortex core size. While most BVI studies use the high-resolution airloads to compute BVI noise, the total noise can often be due to multiple dominant interactions on the advancing and retreating sides. A methodology is developed to evaluate the contribution of an individual interaction to the total BVI noise, based on using the loading due to an individual vortex as an input to the acoustic code WOPWOP. The adaptive-passive BVI alleviation method considered in this study comprises of reducing the length of one set of opposite blades (of a 4-bladed rotor) in low-speed descent. Results showed that differential coning resulting from the blade dissimilarity increases the blade-vortex miss-distances and reduces the BVI noise by 4 dB. The Higher Harmonic Control Aeroacoustic Rotor Test (HART

  7. Effect of atmospheric interference and sensor noise in retrieval of optically active materials in the ocean by hyperspectral remote sensing.

    PubMed

    Levin, Iosif M; Levina, Elizaveta

    2007-10-01

    We present a method to construct the best linear estimate of optically active material concentration from ocean radiance spectra measured through an arbitrary atmosphere layer by a hyperspectral sensor. The algorithm accounts for sensor noise. Optical models of seawater and maritime atmosphere were used to obtain the joint distribution of spectra and concentrations required for the algorithm. The accuracy of phytoplankton retrieval is shown to be substantially lower than that of sediment and dissolved matter. In all cases, the sensor noise noticeably reduces the retrieval accuracy. Additional errors due to atmospheric interference are analyzed, and possible ways to increase the accuracy of retrieval are suggested, such as changing sensor parameters and including a priori information about observation conditions.

  8. Development and experimental verification of a robust active noise control system for a diesel engine in submarines

    NASA Astrophysics Data System (ADS)

    Sachau, D.; Jukkert, S.; Hövelmann, N.

    2016-08-01

    This paper presents the development and experimental validation of an ANC (active noise control)-system designed for a particular application in the exhaust line of a submarine. Thereby, tonal components of the exhaust noise in the frequency band from 75 Hz to 120 Hz are reduced by more than 30 dB. The ANC-system is based on the feedforward leaky FxLMS-algorithm. The observability of the sound pressure in standing wave field is ensured by using two error microphones. The noninvasive online plant identification method is used to increase the robustness of the controller. Online plant identification is extended by a time-varying convergence gain to improve the performance in the presence of slight error in the frequency of the reference signal.

  9. On the prediction of impact noise, Part IX: The noise from punch presses

    NASA Astrophysics Data System (ADS)

    Richards, E. J.; Stimpson, G. J.

    1985-11-01

    The punch press is a further classical example of impact noise: the force is built up in the punch relatively slowly, and the whole machine is strained until the load on the material being punched reaches a yield and shortly afterwards a fracture level. At this stage the strain energy in the machine and its workpiece must be redistributed and this leads to vibration of the whole machine and to noise radiation. In this paper work which has been carried out at ISVR over a number of years is presented. It describes the way the Energy Accountancy Equation [1] can be modified to relate the noise radiated directly to the sum of the squares of the large rates of change of force against time, and illustrates clearly the way that noise control, with use of passive or active methods in designing the punch tooling, can be related directly to the one parameter 10 log Σ[ f( t)] max2. It is shown that noise levels can be reduced by up to 30 dB under ideal conditions by fracture pulse tailoring while still cutting metal, but that more realistically, 10 dB reductions may be obtained below those of current practice by practical tool design. An explanation is given of why large open presses are never likely to achieve the proposed factory noise levels and that the noise from double-sided presses can be controlled effectively by tooling modifications and by the addition of damping. The paper describes work carried out on passive and active cancellation systems used to arrest and springback of the press structure following workpiece material fracture and explains the practical limitations of such systems. Active techniques are limited by the difficulties obtained, with brittle hard materials, of finding a trigger and load freezing system which can operate fast enough to reduce adequately the force parameter 10 log Σ ( fmax( t)) 2. Where punching finish allows, it has been found that well-designed shear and/or cutting with low percentage clearance is superior to active cancellation

  10. Observation of radiation-pressure effects and back-action cancellation in interferometric measurements

    NASA Astrophysics Data System (ADS)

    Heidmann, A.; Caniard, T.; Verlot, P.; Briant, T.; Cohadon, P.-F.

    2008-02-01

    Radiation pressure exerted by light in interferometric measurements is responsible for displacements of mirrors which appear as an additional back-action noise and limit the sensitivity of the measurement. We experimentally study these effects by monitoring in a very highfinesse optical cavity the displacements of a mirror with a sensitivity at the 10 -20 m/√Hz level. This unique sensitivity is a step towards the first observation of the fundamental quantum effects of radiation pressure and the resulting standard quantum limit in interferometric measurements. Our experiment may become a powerful facility to test quantum noise reduction schemes, and we already report the first experimental demonstration of a back-action noise cancellation. Using a classical radiation-pressure noise to mimic the quantum noise of light, we have observed a drastic improvement of sensitivity both in position and force measurements.

  11. 42 CFR 493.1842 - Cancellation of Medicare approval.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...) Written notice of the rationale for, effective date, and effect of, cancellation; (2) Opportunity to submit written evidence or other information against cancellation of the laboratory's approval. This... appeals procedures set forth in § 493.1844. (c) Effect of cancellation. Cancellation of Medicare...

  12. 43 CFR 3452.2-1 - Cause for cancellation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Cause for cancellation. 3452.2-1 Section... Relinquishment, Cancellation, and Termination § 3452.2-1 Cause for cancellation. (a) The authorized officer... continued operation requirements shall be subject to cancellation in whole or in part. In deciding...

  13. 43 CFR 3452.2-1 - Cause for cancellation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Cause for cancellation. 3452.2-1 Section... Relinquishment, Cancellation, and Termination § 3452.2-1 Cause for cancellation. (a) The authorized officer... continued operation requirements shall be subject to cancellation in whole or in part. In deciding...

  14. 43 CFR 3452.2-1 - Cause for cancellation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Cause for cancellation. 3452.2-1 Section... Relinquishment, Cancellation, and Termination § 3452.2-1 Cause for cancellation. (a) The authorized officer... continued operation requirements shall be subject to cancellation in whole or in part. In deciding...

  15. 43 CFR 3452.2-1 - Cause for cancellation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Cause for cancellation. 3452.2-1 Section... Relinquishment, Cancellation, and Termination § 3452.2-1 Cause for cancellation. (a) The authorized officer... continued operation requirements shall be subject to cancellation in whole or in part. In deciding...

  16. 18 CFR 4.83 - Cancellation and loss of priority.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... opportunity for hearing. Cancellation of a permit will result in loss of the permittee's priority of... 18 Conservation of Power and Water Resources 1 2011-04-01 2011-04-01 false Cancellation and loss... Permit § 4.83 Cancellation and loss of priority. (a) The Commission may cancel a preliminary permit...

  17. 18 CFR 4.83 - Cancellation and loss of priority.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... opportunity for hearing. Cancellation of a permit will result in loss of the permittee's priority of... 18 Conservation of Power and Water Resources 1 2014-04-01 2014-04-01 false Cancellation and loss... Permit § 4.83 Cancellation and loss of priority. (a) The Commission may cancel a preliminary permit...

  18. 12 CFR 209.3 - Cancellation of Reserve Bank stock.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 12 Banks and Banking 2 2010-01-01 2010-01-01 false Cancellation of Reserve Bank stock. 209.3... ISSUE AND CANCELLATION OF FEDERAL RESERVE BANK CAPITAL STOCK (REGULATION I) § 209.3 Cancellation of Reserve Bank stock. (a) Application for cancellation. Any bank that desires to withdraw from membership...

  19. 42 CFR 493.1842 - Cancellation of Medicare approval.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 5 2010-10-01 2010-10-01 false Cancellation of Medicare approval. 493.1842 Section 493.1842 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN... Cancellation of Medicare approval. (a) Basis for cancellation. (1) CMS always cancels a laboratory's...

  20. 18 CFR 4.83 - Cancellation and loss of priority.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 18 Conservation of Power and Water Resources 1 2013-04-01 2013-04-01 false Cancellation and loss... Permit § 4.83 Cancellation and loss of priority. (a) The Commission may cancel a preliminary permit after... opportunity for hearing. Cancellation of a permit will result in loss of the permittee's priority...

  1. 18 CFR 4.83 - Cancellation and loss of priority.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 18 Conservation of Power and Water Resources 1 2010-04-01 2010-04-01 false Cancellation and loss... Permit § 4.83 Cancellation and loss of priority. (a) The Commission may cancel a preliminary permit after... opportunity for hearing. Cancellation of a permit will result in loss of the permittee's priority...

  2. 18 CFR 4.83 - Cancellation and loss of priority.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 18 Conservation of Power and Water Resources 1 2012-04-01 2012-04-01 false Cancellation and loss... Permit § 4.83 Cancellation and loss of priority. (a) The Commission may cancel a preliminary permit after... opportunity for hearing. Cancellation of a permit will result in loss of the permittee's priority...

  3. Effective Topological Charge Cancelation Mechanism

    PubMed Central

    Mesarec, Luka; Góźdź, Wojciech; Iglič, Aleš; Kralj, Samo

    2016-01-01

    Topological defects (TDs) appear almost unavoidably in continuous symmetry breaking phase transitions. The topological origin makes their key features independent of systems’ microscopic details; therefore TDs display many universalities. Because of their strong impact on numerous material properties and their significant role in several technological applications it is of strong interest to find simple and robust mechanisms controlling the positioning and local number of TDs. We present a numerical study of TDs within effectively two dimensional closed soft films exhibiting in-plane orientational ordering. Popular examples of such class of systems are liquid crystalline shells and various biological membranes. We introduce the Effective Topological Charge Cancellation mechanism controlling localised positional assembling tendency of TDs and the formation of pairs {defect, antidefect} on curved surfaces and/or presence of relevant “impurities” (e.g. nanoparticles). For this purpose, we define an effective topological charge Δmeff consisting of real, virtual and smeared curvature topological charges within a surface patch Δς identified by the typical spatially averaged local Gaussian curvature K. We demonstrate a strong tendency enforcing Δmeff → 0 on surfaces composed of Δς exhibiting significantly different values of spatially averaged K. For Δmeff ≠ 0 we estimate a critical depinning threshold to form pairs {defect, antidefect} using the electrostatic analogy. PMID:27250777

  4. Effective Topological Charge Cancelation Mechanism

    NASA Astrophysics Data System (ADS)

    Mesarec, Luka; Góźdź, Wojciech; Iglič, Aleš; Kralj, Samo

    2016-06-01

    Topological defects (TDs) appear almost unavoidably in continuous symmetry breaking phase transitions. The topological origin makes their key features independent of systems’ microscopic details; therefore TDs display many universalities. Because of their strong impact on numerous material properties and their significant role in several technological applications it is of strong interest to find simple and robust mechanisms controlling the positioning and local number of TDs. We present a numerical study of TDs within effectively two dimensional closed soft films exhibiting in-plane orientational ordering. Popular examples of such class of systems are liquid crystalline shells and various biological membranes. We introduce the Effective Topological Charge Cancellation mechanism controlling localised positional assembling tendency of TDs and the formation of pairs {defect, antidefect} on curved surfaces and/or presence of relevant “impurities” (e.g. nanoparticles). For this purpose, we define an effective topological charge Δmeff consisting of real, virtual and smeared curvature topological charges within a surface patch Δς identified by the typical spatially averaged local Gaussian curvature K. We demonstrate a strong tendency enforcing Δmeff → 0 on surfaces composed of Δς exhibiting significantly different values of spatially averaged K. For Δmeff ≠ 0 we estimate a critical depinning threshold to form pairs {defect, antidefect} using the electrostatic analogy.

  5. Unperceivable noise to active light touch effects on fast postural sway.

    PubMed

    Kimura, Tetsuya; Kouzaki, Motoki; Masani, Kei; Moritani, Toshio

    2012-01-01

    Human postural sway during quiet standing is reduced when a fingertip lightly touches a stable surface. The tactile feedback information from the fingertip has been considered responsible for this effect of light touch. Studies have shown that a noise-like minute stimulation to the sensory system can improve the system's weak signal detection. In the present study, we investigated whether a noise-like unperceivable vibration on the fingertip enhances its tactile sensation and facilitates the effect of light touch during quiet standing. Thirteen volunteers maintained quiet standing while lightly touching a touch surface with the index fingertip. Based on each subject's vibrotactile threshold (VT), a noise-like vibration was applied to the touch surface at amplitudes under (0.5VT) or at VT (1.0VT), in addition to the normal light touch condition (no vibration, 0VT). The results showed that the mean velocities of the foot center of pressure (CoP) in both the anteroposterior (AP) and mediolateral (ML) directions were significantly reduced at 0.5VT compared to 0VT and 1.0VT (P<0.05), while there was no significant difference between 1.0VT and 0VT (P>0.05). Frequency analysis of CoP revealed that the power of high-frequency fluctuation (1-10Hz) was significantly reduced at 0.5VT (P<0.05), whereas no significant change was observed in that of low-frequency sway (below 1Hz) (P>0.05). These results indicate that an unperceivable noise-like vibration can facilitate the effect of light touch on postural stability, by further reducing fast postural sway. PMID:22075223

  6. Modeling the impact of common noise inputs on the network activity of retinal ganglion cells

    PubMed Central

    Ahmadian, Yashar; Shlens, Jonathon; Pillow, Jonathan W.; Kulkarni, Jayant; Litke, Alan M.; Chichilnisky, E. J.; Simoncelli, Eero; Paninski, Liam

    2013-01-01

    Synchronized spontaneous firing among retinal ganglion cells (RGCs), on timescales faster than visual responses, has been reported in many studies. Two candidate mechanisms of synchronized firing include direct coupling and shared noisy inputs. In neighboring parasol cells of primate retina, which exhibit rapid synchronized firing that has been studied extensively, recent experimental work indicates that direct electrical or synaptic coupling is weak, but shared synaptic input in the absence of modulated stimuli is strong. However, previous modeling efforts have not accounted for this aspect of firing in the parasol cell population. Here we develop a new model that incorporates the effects of common noise, and apply it to analyze the light responses and synchronized firing of a large, densely-sampled network of over 250 simultaneously recorded parasol cells. We use a generalized linear model in which the spike rate in each cell is determined by the linear combination of the spatio-temporally filtered visual input, the temporally filtered prior spikes of that cell, and unobserved sources representing common noise. The model accurately captures the statistical structure of the spike trains and the encoding of the visual stimulus, without the direct coupling assumption present in previous modeling work. Finally, we examined the problem of decoding the visual stimulus from the spike train given the estimated parameters. The common-noise model produces Bayesian decoding performance as accurate as that of a model with direct coupling, but with significantly more robustness to spike timing perturbations. PMID:22203465

  7. Modeling the impact of common noise inputs on the network activity of retinal ganglion cells.

    PubMed

    Vidne, Michael; Ahmadian, Yashar; Shlens, Jonathon; Pillow, Jonathan W; Kulkarni, Jayant; Litke, Alan M; Chichilnisky, E J; Simoncelli, Eero; Paninski, Liam

    2012-08-01

    Synchronized spontaneous firing among retinal ganglion cells (RGCs), on timescales faster than visual responses, has been reported in many studies. Two candidate mechanisms of synchronized firing include direct coupling and shared noisy inputs. In neighboring parasol cells of primate retina, which exhibit rapid synchronized firing that has been studied extensively, recent experimental work indicates that direct electrical or synaptic coupling is weak, but shared synaptic input in the absence of modulated stimuli is strong. However, previous modeling efforts have not accounted for this aspect of firing in the parasol cell population. Here we develop a new model that incorporates the effects of common noise, and apply it to analyze the light responses and synchronized firing of a large, densely-sampled network of over 250 simultaneously recorded parasol cells. We use a generalized linear model in which the spike rate in each cell is determined by the linear combination of the spatio-temporally filtered visual input, the temporally filtered prior spikes of that cell, and unobserved sources representing common noise. The model accurately captures the statistical structure of the spike trains and the encoding of the visual stimulus, without the direct coupling assumption present in previous modeling work. Finally, we examined the problem of decoding the visual stimulus from the spike train given the estimated parameters. The common-noise model produces Bayesian decoding performance as accurate as that of a model with direct coupling, but with significantly more robustness to spike timing perturbations.

  8. ANOMALY STRUCTURE OF SUPERGRAVITY AND ANOMALY CANCELLATION

    SciTech Connect

    Butter, Daniel; Gaillard, Mary K.

    2009-06-10

    We display the full anomaly structure of supergravity, including new D-term contributions to the conformal anomaly. This expression has the super-Weyl and chiral U(1){sub K} transformation properties that are required for implementation of the Green-Schwarz mechanism for anomaly cancellation. We outline the procedure for full anomaly cancellation. Our results have implications for effective supergravity theories from the weakly coupled heterotic string theory.

  9. Proceedings, inter-noise 84 - international cooperation for noise control. 2 Vols

    SciTech Connect

    Maling, G.C. Jr.

    1984-01-01

    A total of 199 papers were presented on noise control engineering, especially in the areas of community noise control, sound intensity, noise emission sources, active sound attenuation and noise reduction by barriers. 4 papers have been abstracted separately.

  10. Coarse-fine residual gravity cancellation system with magnetic levitation

    NASA Technical Reports Server (NTRS)

    Salcudean, S. E.; Davis, H.; Chen, C. T.; Goertz, D. E.; Tryggvason, B. V.

    1992-01-01

    Aircraft flight along parabolic trajectories have been proposed and executed in order to achieve low cost, near free fall conditions of moderate duration. This paper describes a six degree of freedom experiment isolation system designed to cancel out residual accelerations due to mechanical vibrations and errors in aircraft trajectory. The isolation system consists of a fine motion magnetic levitator whose stator is transported by a conventional coarse motion stage. The levitator uses wide gap voice coil actuators and has the dual purpose of isolating the experiment platform from aircraft vibrations and actively cancelling residual accelerations through feedback control. The course motion stage tracks the levitated platform in order to keep the levitator's coils centered within their matching magnetic gaps. Aspects of system design, an analysis of the proposed control strategy and simulation results are presented. Feasibility experiments are also discussed.

  11. 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

  12. A Simplified model of mutually inhibitory sleep-active and wake-active neuronal populations employing a noise-based switching mechanism.

    PubMed

    Patel, Mainak

    2016-04-01

    Infant rats switch randomly between the sleeping and waking states; during early infancy (up to postnatal day 8), sleep and wake bouts are random, brief (with means on the order of several seconds) and exponentially distributed, with the length of a particular bout independent of the length of prior bouts. As the rat ages during this early period, mean sleep and wake bout lengths gradually increase, though sleep and wake bouts remain exponentially distributed. Additionally, sleep and wake bouts are regulated independently of each other - alterations in the development of sleep (wake) bouts has no impact on the regulation wake (sleep) bouts. Sleep and wake bout behavior is associated with the activity of mutually inhibitory sleep-active and wake-active brainstem populations. In this work, I employ a simplified biophysical model of two mutually inhibitory populations consisting of ten integrate-and-fire neurons each and a noise-based switching mechanism. I show that such a noise-based switching mechanism naturally accounts for the experimentally observed features of sleep-wake switching during early infancy - random alternating activity bouts occur as a consequence of noise (provided inhibition is strong relative to excitation), bout durations are exponential (due to a lack of memory within the system), and cross-population inhibition or intrapopulation excitatory coupling provide mechanisms for changing and independently regulated sleep and wake bout means. PMID:26802484

  13. A Simplified model of mutually inhibitory sleep-active and wake-active neuronal populations employing a noise-based switching mechanism.

    PubMed

    Patel, Mainak

    2016-04-01

    Infant rats switch randomly between the sleeping and waking states; during early infancy (up to postnatal day 8), sleep and wake bouts are random, brief (with means on the order of several seconds) and exponentially distributed, with the length of a particular bout independent of the length of prior bouts. As the rat ages during this early period, mean sleep and wake bout lengths gradually increase, though sleep and wake bouts remain exponentially distributed. Additionally, sleep and wake bouts are regulated independently of each other - alterations in the development of sleep (wake) bouts has no impact on the regulation wake (sleep) bouts. Sleep and wake bout behavior is associated with the activity of mutually inhibitory sleep-active and wake-active brainstem populations. In this work, I employ a simplified biophysical model of two mutually inhibitory populations consisting of ten integrate-and-fire neurons each and a noise-based switching mechanism. I show that such a noise-based switching mechanism naturally accounts for the experimentally observed features of sleep-wake switching during early infancy - random alternating activity bouts occur as a consequence of noise (provided inhibition is strong relative to excitation), bout durations are exponential (due to a lack of memory within the system), and cross-population inhibition or intrapopulation excitatory coupling provide mechanisms for changing and independently regulated sleep and wake bout means.

  14. 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

  15. Active shunt capacitance cancelling oscillator circuit

    DOEpatents

    Wessendorf, Kurt O.

    2003-09-23

    An oscillator circuit is disclosed which can be used to produce oscillation using a piezoelectric crystal, with a frequency of oscillation being largely independent of any shunt capacitance associated with the crystal (i.e. due to electrodes on the surfaces of the crystal and due to packaging and wiring for the crystal). The oscillator circuit is based on a tuned gain stage which operates the crystal at a frequency, f, near a series resonance frequency, f.sub.S. The oscillator circuit further includes a compensation circuit that supplies all the ac current flow through the shunt resistance associated with the crystal so that this ac current need not be supplied by the tuned gain stage. The compensation circuit uses a current mirror to provide the ac current flow based on the current flow through a reference capacitor that is equivalent to the shunt capacitance associated with the crystal. The oscillator circuit has applications for driving piezoelectric crystals for sensing of viscous, fluid or solid media by detecting a change in the frequency of oscillation of the crystal and a resonator loss which occur from contact of an exposed surface of the crystal by the viscous, fluid or solid media.

  16. A Nonlinear Adaptive Filter for Gyro Thermal Bias Error Cancellation

    NASA Technical Reports Server (NTRS)

    Galante, Joseph M.; Sanner, Robert M.

    2012-01-01

    Deterministic errors in angular rate gyros, such as thermal biases, can have a significant impact on spacecraft attitude knowledge. In particular, thermal biases are often the dominant error source in MEMS gyros after calibration. Filters, such as J\\,fEKFs, are commonly used to mitigate the impact of gyro errors and gyro noise on spacecraft closed loop pointing accuracy, but often have difficulty in rapidly changing thermal environments and can be computationally expensive. In this report an existing nonlinear adaptive filter is used as the basis for a new nonlinear adaptive filter designed to estimate and cancel thermal bias effects. A description of the filter is presented along with an implementation suitable for discrete-time applications. A simulation analysis demonstrates the performance of the filter in the presence of noisy measurements and provides a comparison with existing techniques.

  17. Adaptive Suppression of Noise in Voice Communications

    NASA Technical Reports Server (NTRS)

    Kozel, David; DeVault, James A.; Birr, Richard B.

    2003-01-01

    A subsystem for the adaptive suppression of noise in a voice communication system effects a high level of reduction of noise that enters the system through microphones. The subsystem includes a digital signal processor (DSP) plus circuitry that implements voice-recognition and spectral- manipulation techniques. The development of the adaptive noise-suppression subsystem was prompted by the following considerations: During processing of the space shuttle at Kennedy Space Center, voice communications among test team members have been significantly impaired in several instances because some test participants have had to communicate from locations with high ambient noise levels. Ear protection for the personnel involved is commercially available and is used in such situations. However, commercially available noise-canceling microphones do not provide sufficient reduction of noise that enters through microphones and thus becomes transmitted on outbound communication links.

  18. Does exposure to noise from human activities compromise sensory information from cephalopod statocysts?

    NASA Astrophysics Data System (ADS)

    Solé, Marta; Lenoir, Marc; Durfort, Mercè; López-Bejar, Manel; Lombarte, Antoni; van der Schaar, Mike; André, Michel

    2013-10-01

    Many anthropogenic noise sources are nowadays contributing to the general noise budget of the oceans. The extent to which sound in the sea impacts and affects marine life is a topic of considerable current interest both to the scientific community and to the general public. Cepaholopods potentially represent a group of species whose ecology may be influenced by artificial noise that would have a direct consequence on the functionality and sensitivity of their sensory organs, the statocysts. These are responsible for their equilibrium and movements in the water column. Controlled Exposure Experiments, including the use of a 50-400Hz sweep (RL=157±5dB re 1μPa with peak levels up to SPL=175dB re 1μPa) revealed lesions in the statocysts of four cephalopod species of the Mediterranean Sea, when exposed to low frequency sounds: (n=76) of Sepia officinalis, (n=4) Octopus vulgaris, (n=5) Loligo vulgaris and (n=2) Illex condietii. The analysis was performed through scanning (SEM) and transmission (TEM) electron microscopical techniques of the whole inner structure of the cephalopods' statocyst, especially on the macula and crista. All exposed individuals presented the same lesions and the same incremental effects over time, consistent with a massive acoustic trauma observed in other species that have been exposed to much higher intensities of sound: Immediately after exposure, the damage was observed in the macula statica princeps (msp) and in the crista sensory epithelium. Kinocilia on hair cells were either missing or were bent or flaccid. A number of hair cells showed protruding apical poles and ruptured lateral plasma membranes, most probably resulting from the extrusion of cytoplasmic material. Hair cells were also partially ejected from the sensory epithelium, and spherical holes corresponding to missing hair cells were visible in the epithelium. The cytoplasmic content of the damaged hair cells showed obvious changes, including the presence of numerous vacuoles

  19. 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.

  20. 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.

  1. A study of active tonal noise control for a small axial flow fan.

    PubMed

    Wang, J; Huang, L; Cheng, L

    2005-02-01

    Sound radiated by a computer cooling fan consists of tones which are phase locked with the rotation, and other less deterministic tones and broadband random noise. This paper demonstrates the feasibility of globally eliminating the rotation-locked tones by applying a very simple destructive interference to a modified cooling fan with the number of struts equal to the number of rotor blades. The rig consists of a miniature electret microphone used as a rotation sensor, an ordinary loudspeaker, and a bandpass filter with adjustable amplitude and phase delay. The microphone is located at the inlet bellmouth of the fan to pick up the fluctuating aerodynamic pressure caused by the passing rotor blades. The pressure spectrum is rich in the blade passing frequency (BPF) and its low-order harmonics. It provides much better performance than a pulse-generating tachometer. Analysis of the original fan noise shows that about 90% of the radiated tonal sound is phase locked with rotation, and this portion is almost completely eliminated in all directions. The reductions of the radiated sound power in the first two BPFs are 18.5 and 13.0 dB, respectively, and the overall sound power reduction is 11.0 dB.

  2. A study of active tonal noise control for a small axial flow fan

    NASA Astrophysics Data System (ADS)

    Wang, J.; Huang, L.; Cheng, L.

    2005-02-01

    Sound radiated by a computer cooling fan consists of tones which are phase locked with the rotation, and other less deterministic tones and broadband random noise. This paper demonstrates the feasibility of globally eliminating the rotation-locked tones by applying a very simple destructive interference to a modified cooling fan with the number of struts equal to the number of rotor blades. The rig consists of a miniature electret microphone used as a rotation sensor, an ordinary loudspeaker, and a bandpass filter with adjustable amplitude and phase delay. The microphone is located at the inlet bellmouth of the fan to pick up the fluctuating aerodynamic pressure caused by the passing rotor blades. The pressure spectrum is rich in the blade passing frequency (BPF) and its low-order harmonics. It provides much better performance than a pulse-generating tachometer. Analysis of the original fan noise shows that about 90% of the radiated tonal sound is phase locked with rotation, and this portion is almost completely eliminated in all directions. The reductions of the radiated sound power in the first two BPFs are 18.5 and 13.0 dB, respectively, and the overall sound power reduction is 11.0 dB. .

  3. A study of active tonal noise control for a small axial flow fan.

    PubMed

    Wang, J; Huang, L; Cheng, L

    2005-02-01

    Sound radiated by a computer cooling fan consists of tones which are phase locked with the rotation, and other less deterministic tones and broadband random noise. This paper demonstrates the feasibility of globally eliminating the rotation-locked tones by applying a very simple destructive interference to a modified cooling fan with the number of struts equal to the number of rotor blades. The rig consists of a miniature electret microphone used as a rotation sensor, an ordinary loudspeaker, and a bandpass filter with adjustable amplitude and phase delay. The microphone is located at the inlet bellmouth of the fan to pick up the fluctuating aerodynamic pressure caused by the passing rotor blades. The pressure spectrum is rich in the blade passing frequency (BPF) and its low-order harmonics. It provides much better performance than a pulse-generating tachometer. Analysis of the original fan noise shows that about 90% of the radiated tonal sound is phase locked with rotation, and this portion is almost completely eliminated in all directions. The reductions of the radiated sound power in the first two BPFs are 18.5 and 13.0 dB, respectively, and the overall sound power reduction is 11.0 dB. PMID:15759693

  4. Noise considerations for remote detection of life signs with microwave Doppler radar.

    PubMed

    Nguyen, Dung; Yamada, Shuhei; Park, Byung-Kwon; Lubecke, Victor; Boric-Lubecke, Olga; Host-Madsen, Anders

    2007-01-01

    This paper describes and quantifies three main sources of baseband noise affecting physiological signals in a direct conversion microwave Doppler radar for life signs detection. They are thermal noise, residual phase noise, and Flicker noise. In order to increase the SNR of physiological signals at baseband, the noise floor, in which the Flicker noise is the most dominant factor, needs to be minimized. This paper shows that with the consideration of the noise factor in our Doppler radar, Flicker noise canceling techniques may drastically reduce the power requirement for heart rate signal detection by as much as a factor of 100.

  5. 2D and 3D Numerical Simulations of Flux Cancellation

    NASA Technical Reports Server (NTRS)

    Karpen, Judith T.; DeVore, C.; Antiochos, S. K.; Linton, M. G.

    2009-01-01

    Cancellation of magnetic flux in the solar photosphere and chromosphere has been linked observationally and theoretically to a broad range of solar activity, from filament channel formation to CME initiation. Because this phenomenon is typically measured at only a single layer in the atmosphere, in the radial (line of sight) component of the magnetic field, the actual processes behind this observational signature are ambiguous. It is clear that reconnection is involved in some way, but the location of the reconnection sites and associated connectivity changes remain uncertain in most cases. We are using numerical modeling to demystify flux cancellation, beginning with the simplest possible configuration: a subphotospheric Lundquist flux tube surrounded by a potential field, immersed in a gravitationally stratified atmosphere, spanning many orders of magnitude in plasma beta. In this system, cancellation is driven slowly by a 2-cell circulation pattern imposed in the convection zone, such that the tops of the cells are located around the beta=1 level (i.e., the photosphere) and the flows converge and form a downdraft at the polarity inversion line; note however that no flow is imposed along the neutral line. We will present the results of 2D and 3D MHD-AMR simulations of flux cancellation, in which the flux at the photosphere begins in either an unsheared or sheared state. In all cases, a low-lying flux rope is formed by reconnection at the polarity inversion line within a few thousand seconds. The flux rope remains stable and does not rise, however, in contrast to models which do not include the presence of significant mass loading.

  6. 20 and 3D Numerical Simulations of Flux Cancellation

    NASA Technical Reports Server (NTRS)

    Karpen, Judith T.; DeVore, C.; Antiochos, S. K.; Linton, M. G.

    2009-01-01

    Cancellation of magnetic flux in the solar photosphere and chromosphere has been linked observationally and theoretically to a broad range of solar activity, from filament channel formation to CME initiation. Because this phenomenon is typically measured at only a single layer in the atmosphere, in the radial (line of sight) component of the magnetic field, the actual processes behind this observational signature are ambiguous. It is clear that reconnection is involved in some way, but the location of the reconnection sites and associated connectivity changes remain uncertain in most cases. We are using numerical modeling to demystify flux cancellation, beginning with the simplest possible configuration: a subphotospheric Lundquist flux tube surrounded by a potential field, immersed in a gravitationally stratified atmosphere, spanning many orders of magnitude in plasma beta. In this system, cancellation is driven slowly by a 2-cell circulation pattern imposed in the convection zone, such that the tops of the cells are located around the beta= 1 level (Le., the photosphere) and the flows converge and form a downdraft at the polarity inversion line; note however that no flow is imposed along the neutral line. We will present the results of 2D and 3D MHD-AMR simulations of flux cancellation, in which the flux at the photosphere begins in either an unsheared or sheared state. In all cases, a lOW-lying flux rope is formed by reconnection at the polarity inversion line within a few thousand seconds. The flux rope remains stable and does not rise, however, in contrast to models which do not include the presence of significant mass loading.

  7. 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.

  8. Low-noise detector and amplifier design for 100 ns direct detection CO{sub 2} LIDAR receiver

    SciTech Connect

    Cafferty, M.M.; Cooke, B.J.; Laubscher, B.E.; Olivas, N.L.; Fuller, K.

    1997-06-01

    The development and test results of a prototype detector/amplifier design for a background limited, pulsed 100 ns, 10--100 kHz repetition rate LIDAR/DIAL receiver system are presented. Design objectives include near-matched filter detection of received pulse amplitude and round trip time-of-flight, and the elimination of excess correlated detector/amplifier noise for optimal pulse averaging. A novel pole-zero cancellation amplifier, coupled with a state-of-the-art SBRC (Santa Barbara Research Center) infrared detector was implemented to meet design objectives. The pole-zero cancellation amplifier utilizes a tunable, pseudo-matched filter technique to match the width of the laser pulse to the shaping time of the filter for optimal SNR performance. Low frequency correlated noise, (l/f and drift noise) is rejected through a second order high gain feedback loop. The amplifier also employs an active detector bias stage minimizing detector drift. Experimental results will be provided that demonstrate near-background limited, 100 ns pulse detection performance given a 8.5--11.5 {micro}m (300 K B.B.) radiant background, with the total noise floor spectrally white for optimal pulse averaging efficiency.

  9. Active Control of Low-Speed Fan Tonal Noise Using Actuators Mounted in Stator Vanes: Part III Results

    NASA Technical Reports Server (NTRS)

    Sutliff, Daniel L.; Remington, Paul J.; Walker, Bruce E.

    2003-01-01

    A test program to demonstrate simplification of Active Noise Control (ANC) systems relative to standard techniques was performed on the NASA Glenn Active Noise Control Fan from May through September 2001. The target mode was the m = 2 circumferential mode generated by the rotor-stator interaction at 2BPF. Seven radials (combined inlet and exhaust) were present at this condition. Several different error-sensing strategies were implemented. Integration of the error-sensors with passive treatment was investigated. These were: (i) an in-duct linear axial array, (ii) an induct steering array, (iii) a pylon-mounted array, and (iv) a near-field boom array. The effect of incorporating passive treatment was investigated as well as reducing the actuator count. These simplified systems were compared to a fully ANC specified system. Modal data acquired using the Rotating Rake are presented for a range of corrected fan rpm. Simplified control has been demonstrated to be possible but requires a well-known and dominant mode signature. The documented results here in are part III of a three-part series of reports with the same base title. Part I and II document the control system and error-sensing design and implementation.

  10. Noise reduction in a launch vehicle fairing using actively tuned loudspeakers.

    PubMed

    Kemp, Jonathan D; Clark, Robert L

    2003-04-01

    Loudspeakers tuned as optimal acoustic absorbers can significantly reduce damaging, low frequency, reverberant noise in a full-scale launch vehicle fairing. Irregular geometry, changing payloads, and the compliant nature of the fairing hinder effective implementation of a passively tuned loudspeaker. A method of tuning the loudspeaker dynamics in real time is required to meet the application requirements. Through system identification, the dynamics of the enclosure can be identified and used to tune the dynamics of the loudspeaker for reduction of targeted, high intensity, low-frequency modes that dominate the acoustic response in the fairing. A loudspeaker model with desired dynamics serves as the reference model in a control law designed to tune the dynamics of a non-ideal loudspeaker to act as an optimal tuned absorber. Experimental results indicate that a tuned loudspeaker placed in the nose cone of the fairing significantly reduces acoustic energy and verifies results calculated from the simulation.

  11. Improved CDMA Performance Using Parallel Interference Cancellation

    NASA Technical Reports Server (NTRS)

    Simon, Marvin; Divsalar, Dariush

    1995-01-01

    This report considers a general parallel interference cancellation scheme that significantly reduces the degradation effect of user interference but with a lesser implementation complexity than the maximum-likelihood technique. The scheme operates on the fact that parallel processing simultaneously removes from each user the interference produced by the remaining users accessing the channel in an amount proportional to their reliability. The parallel processing can be done in multiple stages. The proposed scheme uses tentative decision devices with different optimum thresholds at the multiple stages to produce the most reliably received data for generation and cancellation of user interference. The 1-stage interference cancellation is analyzed for three types of tentative decision devices, namely, hard, null zone, and soft decision, and two types of user power distribution, namely, equal and unequal powers. Simulation results are given for a multitude of different situations, in particular, those cases for which the analysis is too complex.

  12. 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

  13. CancellationTools: All-in-one software for administration and analysis of cancellation tasks.

    PubMed

    Dalmaijer, Edwin S; Van der Stigchel, Stefan; Nijboer, Tanja C W; Cornelissen, Tim H W; Husain, Masud

    2015-12-01

    In a cancellation task, a participant is required to search for and cross out ("cancel") targets, which are usually embedded among distractor stimuli. The number of cancelled targets and their location can be used to diagnose the neglect syndrome after stroke. In addition, the organization of search provides a potentially useful way to measure executive control over multitarget search. Although many useful cancellation measures have been introduced, most fail to make their way into research studies and clinical practice due to the practical difficulty of acquiring such parameters from traditional pen-and-paper measures. Here we present new, open-source software that is freely available to all. It allows researchers and clinicians to flexibly administer computerized cancellation tasks using stimuli of their choice, and to directly analyze the data in a convenient manner. The automated analysis suite provides output that includes almost all of the currently existing measures, as well as several new ones introduced here. All tasks can be performed using either a computer mouse or a touchscreen as an input device, and an online version of the task runtime is available for tablet devices. A summary of the results is produced in a single A4-sized PDF document, including high quality data visualizations. For research purposes, batch analysis of large datasets is possible. In sum, CancellationTools allows users to employ a flexible, computerized cancellation task, which provides extensive benefits and ease of use.

  14. Cloaking through cancellation of diffusive wave scattering

    NASA Astrophysics Data System (ADS)

    Farhat, M.; Chen, P. Y.; Guenneau, S.; Bağc, H.; Salama, K. N.; Alù, A.

    2016-08-01

    A new cloaking mechanism, which makes enclosed objects invisible to diffusive photon density waves, is proposed. First, diffusive scattering from a basic core-shell geometry, which represents the cloaked structure, is studied. The conditions of scattering cancellation in a quasi-static scattering regime are derived. These allow for tailoring the diffusivity constant of the shell enclosing the object so that the fields scattered from the shell and the object cancel each other. This means that the photon flow outside the cloak behaves as if the cloaked object were not present. Diffusive light invisibility may have potential applications in hiding hot spots in infrared thermography or tissue imaging.

  15. 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…

  16. Novel active signal compression in low-noise analog readout at future X-ray FEL facilities

    NASA Astrophysics Data System (ADS)

    Manghisoni, M.; Comotti, D.; Gaioni, L.; Lodola, L.; Ratti, L.; Re, V.; Traversi, G.; Vacchi, C.

    2015-04-01

    This work presents the design of a low-noise front-end implementing a novel active signal compression technique. This feature can be exploited in the design of analog readout channels for application to the next generation free electron laser (FEL) experiments. The readout architecture includes the low-noise charge sensitive amplifier (CSA) with dynamic signal compression, a time variant shaper used to process the signal at the preamplifier output and a 10-bit successive approximation register (SAR) analog-to-digital converter (ADC). The channel will be operated in such a way to cope with the high frame rate (exceeding 1 MHz) foreseen for future XFEL machines. The choice of a 65 nm CMOS technology has been made in order to include all the building blocks in the target pixel pitch of 100 μm. This work has been carried out in the frame of the PixFEL Project funded by the Istituto Nazionale di Fisica Nucleare (INFN), Italy.

  17. On the use of sensor fusion to reduce the impact of rotational and additive noise in human activity recognition.

    PubMed

    Banos, Oresti; Damas, Miguel; Pomares, Hector; Rojas, Ignacio

    2012-01-01

    The main objective of fusion mechanisms is to increase the individual reliability of the systems through the use of the collectivity knowledge. Moreover, fusion models are also intended to guarantee a certain level of robustness. This is particularly required for problems such as human activity recognition where runtime changes in the sensor setup seriously disturb the reliability of the initial deployed systems. For commonly used recognition systems based on inertial sensors, these changes are primarily characterized as sensor rotations, displacements or faults related to the batteries or calibration. In this work we show the robustness capabilities of a sensor-weighted fusion model when dealing with such disturbances under different circumstances. Using the proposed method, up to 60% outperformance is obtained when a minority of the sensors are artificially rotated or degraded, independent of the level of disturbance (noise) imposed. These robustness capabilities also apply for any number of sensors affected by a low to moderate noise level. The presented fusion mechanism compensates the poor performance that otherwise would be obtained when just a single sensor is considered.

  18. The Effect of Exposure to High Noise Levels on the Performance and Rate of Error in Manual Activities

    PubMed Central

    Khajenasiri, Farahnaz; Zamanian, Alireza; Zamanian, Zahra

    2016-01-01

    Introduction Sound is among the significant environmental factors for people’s health, and it has an important role in both physical and psychological injuries, and it also affects individuals’ performance and productivity. The aim of this study was to determine the effect of exposure to high noise levels on the performance and rate of error in manual activities. Methods This was an interventional study conducted on 50 students at Shiraz University of Medical Sciences (25 males and 25 females) in which each person was considered as its own control to assess the effect of noise on her or his performance at the sound levels of 70, 90, and 110 dB by using two factors of physical features and the creation of different conditions of sound source as well as applying the Two-Arm coordination Test. The data were analyzed using SPSS version 16. Repeated measurements were used to compare the length of performance as well as the errors measured in the test. Results Based on the results, we found a direct and significant association between the levels of sound and the length of performance. Moreover, the participant’s performance was significantly different for different sound levels (at 110 dB as opposed to 70 and 90 dB, p < 0.05 and p < 0.001, respectively). Conclusion This study found that a sound level of 110 dB had an important effect on the individuals’ performances, i.e., the performances were decreased. PMID:27123216

  19. A local active noise control system based on a virtual-microphone technique for railway sleeping vehicle applications

    NASA Astrophysics Data System (ADS)

    Diaz, J.; Egaña, J. M.; Viñolas, J.

    2006-11-01

    Low-frequency broadband noise generated on a railway vehicle by the wheel-rail interaction could be a big annoyance for passengers in sleeping cars. Low-frequency acoustic radiation is extremely difficult to attenuate by using passive devices. In this article, an active noise control (ANC) technique has been proposed for this purpose. A three-dimensional cabin was built in the laboratory to carry out the experiments. The proposed scheme is based on a Filtered-X Least Mean Square (FXLMS) control algorithm, particularised for a virtual-microphone technique. Control algorithms were designed with the Matlab-Simulink tool, and the Real Time Windows Target toolbox of Matlab was used to run in real time the ANC system. Referring to the results, different simulations and experimental performances were analysed to enlarge the silence zone around the passenger's ear zone and along the bed headboard. Attenuations of up to 20 and 15 dB(A) (re:20 μPa) were achieved at the passenger's ear in simulations and in experimental results, respectively.

  20. On the Use of Sensor Fusion to Reduce the Impact of Rotational and Additive Noise in Human Activity Recognition

    PubMed Central

    Banos, Oresti; Damas, Miguel; Pomares, Hector; Rojas, Ignacio

    2012-01-01

    The main objective of fusion mechanisms is to increase the individual reliability of the systems through the use of the collectivity knowledge. Moreover, fusion models are also intended to guarantee a certain level of robustness. This is particularly required for problems such as human activity recognition where runtime changes in the sensor setup seriously disturb the reliability of the initial deployed systems. For commonly used recognition systems based on inertial sensors, these changes are primarily characterized as sensor rotations, displacements or faults related to the batteries or calibration. In this work we show the robustness capabilities of a sensor-weighted fusion model when dealing with such disturbances under different circumstances. Using the proposed method, up to 60% outperformance is obtained when a minority of the sensors are artificially rotated or degraded, independent of the level of disturbance (noise) imposed. These robustness capabilities also apply for any number of sensors affected by a low to moderate noise level. The presented fusion mechanism compensates the poor performance that otherwise would be obtained when just a single sensor is considered. PMID:22969386

  1. Macroscopic Models of Local Field Potentials and the Apparent 1/f Noise in Brain Activity

    PubMed Central

    Bédard, Claude; Destexhe, Alain

    2009-01-01

    The power spectrum of local field potentials (LFPs) has been reported to scale as the inverse of the frequency, but the origin of this 1/f noise is at present unclear. Macroscopic measurements in cortical tissue demonstrated that electric conductivity (as well as permittivity) is frequency-dependent, while other measurements failed to evidence any dependence on frequency. In this article, we propose a model of the genesis of LFPs that accounts for the above data and contradictions. Starting from first principles (Maxwell equations), we introduce a macroscopic formalism in which macroscopic measurements are naturally incorporated, and also examine different physical causes for the frequency dependence. We suggest that ionic diffusion primes over electric field effects, and is responsible for the frequency dependence. This explains the contradictory observations, and also reproduces the 1/f power spectral structure of LFPs, as well as more complex frequency scaling. Finally, we suggest a measurement method to reveal the frequency dependence of current propagation in biological tissue, and which could be used to directly test the predictions of this formalism. PMID:19348744

  2. 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.

  3. Evaluating Signal-Correlated Noise as a Control Task with Language-Related Gamma Activity on Electrocorticography

    PubMed Central

    Brown, Erik C.; Muzik, Otto; Rothermel, Robert; Juhász, Csaba; Shah, Aashit K.; Fuerst, Darren; Mittal, Sandeep; Sood, Sandeep; Asano, Eishi

    2014-01-01

    Objective Our recent electrocorticography (ECoG) study suggested reverse speech, a widely used control task, to be a poor control for non-language-related auditory activity. We hypothesized that this may be due to retained perception as a human voice. We report a follow-up ECoG study in which we contrast forward and reverse speech with a signal-correlated noise (SCN) control task that cannot be perceived as a human voice. Methods Ten patients were presented 90 audible stimuli, including 30 each of corresponding forward speech, reverse speech, and SCN trials, during ECoG recording with evaluation of gamma activity between 50–150 Hz. Results Sites of the lateral temporal gyri activated throughout speech stimuli were generally less activated by SCN, while some temporal sites seemed to process both human and non-human sounds. Reverse speech trials were associated with activities across the temporal lobe similar to those associated with forward speech. Conclusions Findings herein externally validate functional neuroimaging studies utilizing SCN as a control for non-language-specific auditory function. Our findings are consistent with the notion that stimuli perceived as originating from a human voice are poor controls for non-language auditory function. Significance Our findings have implications in functional neuroimaging research as well as improved clinical mapping of auditory functions. PMID:24412331

  4. Contralateral parahippocampal gamma-band activity determines noise-like tinnitus laterality: a region of interest analysis.

    PubMed

    Vanneste, S; Heyning, P Van de; Ridder, D De

    2011-12-29

    Tinnitus is described as an auditory perception in the absence of any external sound source. Tinnitus loudness has been correlated to sustained high frequency gamma-band activity in auditory cortex. It remains unknown whether unilateral tinnitus is always generated in the left auditory cortex, irrespective of the side on which the tinnitus is perceived, or in the contralateral auditory cortex. In order to solve this enigma source localized electroencephalographic (EEG) recordings of a homogenous group of unilateral left and right-sided tinnitus patients presenting with noise-like tinnitus was analyzed. Based on a region of interest analysis, the most important result of this study is that tinnitus lateralization depended on the gamma-band activity of the contralateral parahippocampal area. As for the auditory cortex no differences were found between left-sided and right-sided tinnitus patients. However, in comparison to a control group both left and right-sided tinnitus patients had an increased gamma-band activity in both the left and right primary and secondary auditory cortex. Thus whereas in tinnitus the primary and secondary auditory cortices of both sides are characterized by increased gamma-band activity, the side on which the tinnitus is perceived relates to gamma-band activity in the contralateral parahippocampal area. PMID:21920411

  5. Where's the Noise? Key Features of Spontaneous Activity and Neural Variability Arise through Learning in a Deterministic Network.

    PubMed

    Hartmann, Christoph; Lazar, Andreea; Nessler, Bernhard; Triesch, Jochen

    2015-12-01

    Even in the absence of sensory stimulation the brain is spontaneously active. This background "noise" seems to be the dominant cause of the notoriously high trial-to-trial variability of neural recordings. Recent experimental observations have extended our knowledge of trial-to-trial variability and spontaneous activity in several directions: 1. Trial-to-trial variability systematically decreases following the onset of a sensory stimulus or the start of a motor act. 2. Spontaneous activity states in sensory cortex outline the region of evoked sensory responses. 3. Across development, spontaneous activity aligns itself with typical evoked activity patterns. 4. The spontaneous brain activity prior to the presentation of an ambiguous stimulus predicts how the stimulus will be interpreted. At present it is unclear how these observations relate to each other and how they arise in cortical circuits. Here we demonstrate that all of these phenomena can be accounted for by a deterministic self-organizing recurrent neural network model (SORN), which learns a predictive model of its sensory environment. The SORN comprises recurrently coupled populations of excitatory and inhibitory threshold units and learns via a combination of spike-timing dependent plasticity (STDP) and homeostatic plasticity mechanisms. Similar to balanced network architectures, units in the network show irregular activity and variable responses to inputs. Additionally, however, the SORN exhibits sequence learning abilities matching recent findings from visual cortex and the network's spontaneous activity reproduces the experimental findings mentioned above. Intriguingly, the network's behaviour is reminiscent of sampling-based probabilistic inference, suggesting that correlates of sampling-based inference can develop from the interaction of STDP and homeostasis in deterministic networks. We conclude that key observations on spontaneous brain activity and the variability of neural responses can be

  6. Where's the Noise? Key Features of Spontaneous Activity and Neural Variability Arise through Learning in a Deterministic Network.

    PubMed

    Hartmann, Christoph; Lazar, Andreea; Nessler, Bernhard; Triesch, Jochen

    2015-12-01

    Even in the absence of sensory stimulation the brain is spontaneously active. This background "noise" seems to be the dominant cause of the notoriously high trial-to-trial variability of neural recordings. Recent experimental observations have extended our knowledge of trial-to-trial variability and spontaneous activity in several directions: 1. Trial-to-trial variability systematically decreases following the onset of a sensory stimulus or the start of a motor act. 2. Spontaneous activity states in sensory cortex outline the region of evoked sensory responses. 3. Across development, spontaneous activity aligns itself with typical evoked activity patterns. 4. The spontaneous brain activity prior to the presentation of an ambiguous stimulus predicts how the stimulus will be interpreted. At present it is unclear how these observations relate to each other and how they arise in cortical circuits. Here we demonstrate that all of these phenomena can be accounted for by a deterministic self-organizing recurrent neural network model (SORN), which learns a predictive model of its sensory environment. The SORN comprises recurrently coupled populations of excitatory and inhibitory threshold units and learns via a combination of spike-timing dependent plasticity (STDP) and homeostatic plasticity mechanisms. Similar to balanced network architectures, units in the network show irregular activity and variable responses to inputs. Additionally, however, the SORN exhibits sequence learning abilities matching recent findings from visual cortex and the network's spontaneous activity reproduces the experimental findings mentioned above. Intriguingly, the network's behaviour is reminiscent of sampling-based probabilistic inference, suggesting that correlates of sampling-based inference can develop from the interaction of STDP and homeostasis in deterministic networks. We conclude that key observations on spontaneous brain activity and the variability of neural responses can be

  7. 78 FR 73587 - Taxpayer Advocacy Panel; Meeting Cancellation.

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-06

    ... Internal Revenue Service Taxpayer Advocacy Panel; Meeting Cancellation. AGENCY: Internal Revenue Service... cancellation of the open meeting of the Taxpayer Advocacy Panel Taxpayer Communications Project Committee..., Acting Director, Taxpayer Advocacy Panel. BILLING CODE 4830-01-P...

  8. 37 CFR 2.111 - Filing petition for cancellation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... cancellation. (a) A cancellation proceeding is commenced by filing in the Office a timely petition for... representative, as specified in § 11.14(b) of this chapter. Electronic signatures pursuant to § 2.193(c)...

  9. Control of jet noise

    NASA Astrophysics Data System (ADS)

    Schreck, Stefan

    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.

  10. Suppression of Enhanced Physiological Tremor via Stochastic Noise: Initial Observations

    PubMed Central

    Huethe, Frank; Schulte-Mönting, Jürgen; Mendez-Balbuena, Ignacio; Baker, Stuart N.; Baker, Mark; Hepp-Reymond, Marie-Claude; Manjarrez, Elias; Kristeva, Rumyana

    2014-01-01

    Enhanced physiological tremor is a disabling condition that arises because of unstable interactions between central tremor generators and the biomechanics of the spinal stretch reflex. Previous work has shown that peripheral input may push the tremor-related spinal and cortical systems closer to anti-phase firing, potentially leading to a reduction in tremor through phase cancellation. The aim of the present study was to investigate whether peripherally applied mechanical stochastic noise can attenuate enhanced physiological tremor and improve motor performance. Eight subjects with enhanced physiological tremor performed a visuomotor task requiring the right index finger to compensate a static force generated by a manipulandum to which Gaussian noise (3–35 Hz) was applied. The finger position was displayed on-line on a monitor as a small white dot which the subjects had to maintain in the center of a larger green circle. Electromyogram (EMG) from the active hand muscles and finger position were recorded. Performance was measured by the mean absolute deviation of the white dot from the zero position. Tremor was identified by the acceleration in the frequency range 7–12 Hz. Two different conditions were compared: with and without superimposed noise at optimal amplitude (determined at the beginning of the experiment). The application of optimum noise reduced tremor (accelerometric amplitude and EMG activity) and improved the motor performance (reduced mean absolute deviation from zero). These data provide the first evidence of a significant reduction of enhanced physiological tremor in the human sensorimotor system due to application of external stochastic noise. PMID:25397577

  11. Suppression of enhanced physiological tremor via stochastic noise: initial observations.

    PubMed

    Trenado, Carlos; Amtage, Florian; Huethe, Frank; Schulte-Mönting, Jürgen; Mendez-Balbuena, Ignacio; Baker, Stuart N; Baker, Mark; Hepp-Reymond, Marie-Claude; Manjarrez, Elias; Kristeva, Rumyana

    2014-01-01

    Enhanced physiological tremor is a disabling condition that arises because of unstable interactions between central tremor generators and the biomechanics of the spinal stretch reflex. Previous work has shown that peripheral input may push the tremor-related spinal and cortical systems closer to anti-phase firing, potentially leading to a reduction in tremor through phase cancellation. The aim of the present study was to investigate whether peripherally applied mechanical stochastic noise can attenuate enhanced physiological tremor and improve motor performance. Eight subjects with enhanced physiological tremor performed a visuomotor task requiring the right index finger to compensate a static force generated by a manipulandum to which Gaussian noise (3-35 Hz) was applied. The finger position was displayed on-line on a monitor as a small white dot which the subjects had to maintain in the center of a larger green circle. Electromyogram (EMG) from the active hand muscles and finger position were recorded. Performance was measured by the mean absolute deviation of the white dot from the zero position. Tremor was identified by the acceleration in the frequency range 7-12 Hz. Two different conditions were compared: with and without superimposed noise at optimal amplitude (determined at the beginning of the experiment). The application of optimum noise reduced tremor (accelerometric amplitude and EMG activity) and improved the motor performance (reduced mean absolute deviation from zero). These data provide the first evidence of a significant reduction of enhanced physiological tremor in the human sensorimotor system due to application of external stochastic noise.

  12. 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

  13. [Changes of T-SOD activity and MDA, GSH contents in blood of guinea pigs after exposure to narrow-band noise].

    PubMed

    Shi, X; Guo, F; Liang, Z; Zhu, Q; Yang, Y

    1998-08-01

    In order to evaluate the changes of lipid peroxide response induced by free radical after intense noise exposure, levels of T-SOD and MDA in serum and GSH in blood of guinea pigs were determined. Sixty male adult guinea pigs were used. The narrow band noise was centered at 1000Hz with 100Hz band width 126 dB SPL. It was found: 1) SOD activity in serum increased after 5d exposure (P > 0.05), but decreased after 10d exposure (P > 0. 05); 2) contents of MDA in serum increased (P < 0.05) and contents of GSH in blood decreased with increase of exposure time (P < 0.01). It shows that the lipid peroxide response induced by free radicals increased after intense noise exposure and it is possible to use free radical scavengers and/or antioxidant in prevention and treatment of noise induced damage.

  14. Measurement of drag and its cancellation

    NASA Astrophysics Data System (ADS)

    DeBra, D. B.; Conklin, J. W.

    2011-05-01

    The design of drag cancellation missions of the future will take advantage of the technology experience of the past. The importance of data for modeling of the atmosphere led to at least six types of measurement: (a) balloon flights, (b) missile-launched falling spheres, (c) the 'cannonball' satellites of Ken Champion with accelerometers for low-altitude drag measurement (late 1960s and early 1970s), (d) the Agena flight of LOGACS (1967), a Bell MESA accelerometer mounted on a rotating platform to spectrally shift low-frequency errors in the accelerometer, (e) a series of French low-level accelerometers (e.g. CACTUS, 1975), and (f) correction of differential accelerations for drag errors in measuring gravity gradient on a pair of satellites (GRACE, 2002). The independent invention of the drag-free satellite concept by Pugh and Lange (1964) to cancel external disturbance added implementation opportunities. Its first flight application was for ephemeris prediction improvement with the DISCOS flight (1972)—still the only extended free test mass flight. Then successful flights for reduced disturbance environment for science measurement with gyros on GP-B (2004) and for improved accuracy in geodesy and ocean studies (GOCE, 2009) each using accelerometer measurements to control the drag-canceling thrust. LISA, DECIGO, BBO and other gravity wave-measuring satellite systems will push the cancellation of drag to new levels.

  15. 36 CFR 223.116 - Cancellation.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 2 2011-07-01 2011-07-01 false Cancellation. 223.116 Section 223.116 Parks, Forests, and Public Property FOREST SERVICE, DEPARTMENT OF AGRICULTURE SALE AND DISPOSAL OF NATIONAL FOREST SYSTEM TIMBER, SPECIAL FOREST PRODUCTS, AND FOREST BOTANICAL PRODUCTS...

  16. Database Cancellation: The "Hows" and "Whys"

    ERIC Educational Resources Information Center

    Shapiro, Steven

    2012-01-01

    Database cancellation is one of the most difficult tasks performed by a librarian. This may seem counter-intuitive but, psychologically, it is certainly true. When a librarian or a team of librarians has invested a great deal of time doing research, talking to potential users, and conducting trials before deciding to subscribe to a database, they…

  17. 43 CFR 3108.3 - Cancellation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... OF THE INTERIOR MINERALS MANAGEMENT (3000) OIL AND GAS LEASING Relinquishment, Termination... law, the regulations issued thereunder, or the lease, the lease may be canceled by the Secretary, if the leasehold does not contain a well capable of production of oil or gas in paying quantities, or...

  18. Heineman Prize Lecture: Anomaly Cancellation: A Retrospective

    NASA Astrophysics Data System (ADS)

    Schwarz, John

    2002-04-01

    The mechanism by which gauge and gravitational anomalies cancel in certain string theories is reviewed. A few new tricks are introduced to make the derivation a little simpler, and the string-theoretic interpretation a little clearer, than in the original 1984 work.

  19. Experimental Demonstration of Underwater Acoustic Scattering Cancellation

    PubMed Central

    Rohde, Charles A.; Martin, Theodore P.; Guild, Matthew D.; Layman, Christopher N.; Naify, Christina J.; Nicholas, Michael; Thangawng, Abel L.; Calvo, David C.; Orris, Gregory J.

    2015-01-01

    We explore an acoustic scattering cancellation shell for buoyant hollow cylinders submersed in a water background. A thin, low-shear, elastic coating is used to cancel the monopole scattering from an air-filled, neutrally buoyant steel shell for all frequencies where the wavelength is larger than the object diameter. By design, the uncoated shell also has an effective density close to the aqueous background, independently canceling its dipole scattering. Due to the significantly reduced monopole and dipole scattering, the compliant coating results in a hollow cylindrical inclusion that is simultaneously impedance and sound speed matched to the water background. We demonstrate the proposed cancellation method with a specific case, using an array of hollow steel cylinders coated with thin silicone rubber shells. These experimental results are matched to finite element modeling predictions, confirming the scattering reduction. Additional calculations explore the optimization of the silicone coating properties. Using this approach, it is found that scattering cross-sections can be reduced by 20 dB for all wavelengths up to k0a = 0.85. PMID:26282067

  20. 36 CFR 223.116 - Cancellation.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 36 Parks, Forests, and Public Property 2 2012-07-01 2012-07-01 false Cancellation. 223.116 Section 223.116 Parks, Forests, and Public Property FOREST SERVICE, DEPARTMENT OF AGRICULTURE SALE AND DISPOSAL OF NATIONAL FOREST SYSTEM TIMBER, SPECIAL FOREST PRODUCTS, AND FOREST BOTANICAL PRODUCTS...

  1. 36 CFR 223.116 - Cancellation.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 36 Parks, Forests, and Public Property 2 2014-07-01 2014-07-01 false Cancellation. 223.116 Section 223.116 Parks, Forests, and Public Property FOREST SERVICE, DEPARTMENT OF AGRICULTURE SALE AND DISPOSAL OF NATIONAL FOREST SYSTEM TIMBER, SPECIAL FOREST PRODUCTS, AND FOREST BOTANICAL PRODUCTS...

  2. 36 CFR 223.116 - Cancellation.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 2 2013-07-01 2013-07-01 false Cancellation. 223.116 Section 223.116 Parks, Forests, and Public Property FOREST SERVICE, DEPARTMENT OF AGRICULTURE SALE AND DISPOSAL OF NATIONAL FOREST SYSTEM TIMBER, SPECIAL FOREST PRODUCTS, AND FOREST BOTANICAL PRODUCTS...

  3. 25 CFR 213.40 - Cancellations.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... FIVE CIVILIZED TRIBES, OKLAHOMA, FOR MINING Operations § 213.40 Cancellations. (a) When, in the opinion... or of the applicable regulations, or if mining operations are conducted wastefully and without regard to good mining practice, the Secretary of the Interior shall have the right at any time after 30...

  4. 25 CFR 213.40 - Cancellations.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... FIVE CIVILIZED TRIBES, OKLAHOMA, FOR MINING Operations § 213.40 Cancellations. (a) When, in the opinion... or of the applicable regulations, or if mining operations are conducted wastefully and without regard to good mining practice, the Secretary of the Interior shall have the right at any time after 30...

  5. 44 CFR 206.376 - Loan cancellation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 44 Emergency Management and Assistance 1 2013-10-01 2013-10-01 false Loan cancellation. 206.376 Section 206.376 Emergency Management and Assistance FEDERAL EMERGENCY MANAGEMENT AGENCY, DEPARTMENT OF... as a liability is incurred, regardless of the timing of related cash flows. (c) Revenue...

  6. 7 CFR 1956.130 - Cancellation.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... of acceleration by written notice prior to the date of application. (b) Without application by debtor... bankruptcy shall be cancelled by the use of Form FmHA or its successor agency under Public Law 103-354 1956-1... its successor agency under Public Law 103-354 1956-1 will document: (i) The sources of...

  7. 7 CFR 1956.130 - Cancellation.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... of acceleration by written notice prior to the date of application. (b) Without application by debtor... bankruptcy shall be cancelled by the use of Form FmHA or its successor agency under Public Law 103-354 1956-1... its successor agency under Public Law 103-354 1956-1 will document: (i) The sources of...

  8. 7 CFR 1956.70 - Cancellation.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... the note or other instrument, or because of acceleration by written notice prior to the date of application. Debts due the FmHA or its successor agency under Public Law 103-354 may be canceled upon... administrator, subject to the following conditions: (1) The FmHA or its successor agency under Public Law...

  9. 7 CFR 1956.70 - Cancellation.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... the note or other instrument, or because of acceleration by written notice prior to the date of application. Debts due the FmHA or its successor agency under Public Law 103-354 may be canceled upon... administrator, subject to the following conditions: (1) The FmHA or its successor agency under Public Law...

  10. 7 CFR 1956.130 - Cancellation.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... of acceleration by written notice prior to the date of application. (b) Without application by debtor... bankruptcy shall be cancelled by the use of Form FmHA or its successor agency under Public Law 103-354 1956-1... its successor agency under Public Law 103-354 1956-1 will document: (i) The sources of...

  11. 7 CFR 1956.130 - Cancellation.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... of acceleration by written notice prior to the date of application. (b) Without application by debtor... bankruptcy shall be cancelled by the use of Form FmHA or its successor agency under Public Law 103-354 1956-1... its successor agency under Public Law 103-354 1956-1 will document: (i) The sources of...

  12. 7 CFR 1956.70 - Cancellation.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... the note or other instrument, or because of acceleration by written notice prior to the date of application. Debts due the FmHA or its successor agency under Public Law 103-354 may be canceled upon... administrator, subject to the following conditions: (1) The FmHA or its successor agency under Public Law...

  13. 7 CFR 1956.70 - Cancellation.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... the note or other instrument, or because of acceleration by written notice prior to the date of application. Debts due the FmHA or its successor agency under Public Law 103-354 may be canceled upon... administrator, subject to the following conditions: (1) The FmHA or its successor agency under Public Law...

  14. Method for Canceling Ionospheric Doppler Effect

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.

    1982-01-01

    Unified transponder system with hydrogen-maser oscillators at both stations can compensate for both motional and ionospheric components of Doppler shift. Appropriate choices of frequency shift in output of mixer m3. System exploits proportionality between dispersive component of frequency shift and reciprocal of frequency to achieve cancellation of dispersive component at output.

  15. Rotor noise

    NASA Astrophysics Data System (ADS)

    Schmitz, F. H.

    1991-08-01

    The physical characteristics and sources of rotorcraft noise as they exist today are presented. Emphasis is on helicopter-like vehicles, that is, on rotorcraft in nonaxial flight. The mechanisms of rotor noise are reviewed in a simple physical manner for the most dominant sources of rotorcraft noise. With simple models, the characteristic time- and frequency-domain features of these noise sources are presented for idealized cases. Full-scale data on several rotorcraft are then reviewed to allow for the easy identification of the type and extent of the radiating noise. Methods and limitations of using scaled models to test for several noise sources are subsequently presented. Theoretical prediction methods are then discussed and compared with experimental data taken under very controlled conditions. Finally, some promising noise reduction technology is reviewed.

  16. Rotor noise

    NASA Technical Reports Server (NTRS)

    Schmitz, F. H.

    1991-01-01

    The physical characteristics and sources of rotorcraft noise as they exist today are presented. Emphasis is on helicopter-like vehicles, that is, on rotorcraft in nonaxial flight. The mechanisms of rotor noise are reviewed in a simple physical manner for the most dominant sources of rotorcraft noise. With simple models, the characteristic time- and frequency-domain features of these noise sources are presented for idealized cases. Full-scale data on several rotorcraft are then reviewed to allow for the easy identification of the type and extent of the radiating noise. Methods and limitations of using scaled models to test for several noise sources are subsequently presented. Theoretical prediction methods are then discussed and compared with experimental data taken under very controlled conditions. Finally, some promising noise reduction technology is reviewed.

  17. 12 CFR 209.3 - Cancellation of Reserve Bank stock.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 12 Banks and Banking 2 2011-01-01 2011-01-01 false Cancellation of Reserve Bank stock. 209.3 Section 209.3 Banks and Banking FEDERAL RESERVE SYSTEM BOARD OF GOVERNORS OF THE FEDERAL RESERVE SYSTEM ISSUE AND CANCELLATION OF FEDERAL RESERVE BANK CAPITAL STOCK (REGULATION I) § 209.3 Cancellation...

  18. 46 CFR 308.511 - Cancellation of Open Cargo Policy.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 8 2010-10-01 2010-10-01 false Cancellation of Open Cargo Policy. 308.511 Section 308... INSURANCE War Risk Cargo Insurance Ii-Open Policy War Risk Cargo Insurance § 308.511 Cancellation of Open Cargo Policy. An assured may cancel an Open Cargo Policy by delivering to the underwriting agent,...

  19. 25 CFR 273.62 - Cancelling a contract for cause.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 25 Indians 1 2011-04-01 2011-04-01 false Cancelling a contract for cause. 273.62 Section 273.62....62 Cancelling a contract for cause. (a) Any contract entered into under this part may be cancelled for cause when the contractor fails to perform the work called for under the contract or fails...

  20. 25 CFR 273.62 - Cancelling a contract for cause.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Cancelling a contract for cause. 273.62 Section 273.62....62 Cancelling a contract for cause. (a) Any contract entered into under this part may be cancelled for cause when the contractor fails to perform the work called for under the contract or fails...