bluuebunny/crossref_metadata_2025 huggingface dataset:
Deep ocean noise measurements in the Philippine Sea.
Authors: Dzieciuch Matthew , Worcester Peter
Published: March 2010

In the spring of 2009, a newly developed distributed vertical line array (DVLA) receiver made up of two, 1000-m-long subarrays with 30 hydrophones each was deployed for approximately 1 month in the northern Philippine Sea. One subarray spanned the sound-channel axis, and the second subarray spanned the surface conjugate depth (about 4200 m). Twenty of the 30 hydrophones in the deep subarray were spaced 5 m apart (half-lambda at 150 Hz), allowing the vertical directionality of the ambient noise below the surface conjugate depth to be determined. The minimum omnidirectional ambient noise levels decreased significantly below the surface conjugate depth at frequencies from 50 to 500 Hz, similar to behavior previously observed in the central North Pacific Ocean. The minimum noise levels presumably correspond to times when wind speeds are low and surface conditions are calm so that there is little locally generated, low-frequency noise.
Horizontal noise directionality in deep water measurements and modeling.
Authors: Campbell Richard , Heaney Kevin D. , Baggeroer Arthur B.
Published: March 2010

Low-frequency, less than 100 Hz, sound is dominated by surface shipping, particularly in the northern hemisphere. With low-volume attenuation sound can propagate significant distances. For periods of time not dominated by a particular nearby interferer, the low-frequency ambient noise field is dominated by distant shipping and is expected to be anisotropic due to various bathymetric effects such as downslope conversion and seamount or ocean ridge blockage. In this paper, the authors present horizontal array measurements from a 100 m towed line array (towed at 100 m) in very deep water in the Philippine Sea. The northern Philippine Sea has several ridges and seamounts and significant bathymetric interaction for surface ships in the main Singapore Shanghai shipping lane. A rapid range bearing dependent N×2D parabolic equation approach will be described and used to evaluate the bathymetric effects on the horizontal directionality of low-frequency noise. Comparisons of measurements and models will be done using both Monte-Carlo realizations of surface ship positions (from the HITS database) as well as measured AIS from research vessels in the vicinity.
Blue whale vocalizations and the seasonal variability of ambient noise levels at the Aloha Observatory.
Authors: Diachok Orest , Duennebier Fred
Published: March 2010

In February, 2007 the Aloha Observatory added a cabled, bottom mounted hydrophone, which supplied a 20-month continuous recording of ambient noise from 0.02 Hz to 11 kHz. This observatory is situated at a depth of 4700 m, 100 km north of Oahu. This site is known to be close to (possibly within) one of the primary habitats of NE Pacific and NW Pacific blues, and other whales during the winter. Numerous previously reported measurements throughout the NE Pacific Ocean have demonstrated that the fundamental frequencies of NE blues vocalizations have systematically decreased from about 22.5 Hz in 1958 to about 16.5 Hz in 2007 (the cause of the frequency shift is unknown). Limited measurements suggest that the fundamental frequencies of NW blues vocalizations have also decreased with time and were about 18 Hz in 2007. Ambient noise levels from the Aloha site were analyzed in 1-Hz bands for 1 year to permit observation of the seasonal dependence of ambient noise levels as a function of frequency. The data reveal distinct peaks in noise levels at 16.5 and 18.5 Hz between November and March, consistent with observations of the fundamental frequencies of NE and NW blue whale vocalizations. Since blues and other whales repertoire of vocalizations cover a broad frequency range, the contributions of their vocalizations to noise levels at other frequencies will be considered.
Invariant features of deep ocean ambient noise.
Authors: Guralnik Zachary S.
Published: March 2010

Very low-frequency, deep ocean ambient noise is generated by non-linear interactions (collisions) between surface waves with nearly equal frequency, propagating in nearly opposite direction. It is shown that the usual “standing wave” approximation used to compute this noise predicts that the ratios of entries in the power spectral density matrix, obtained from auto and cross-correlations of acoustic velocity and pressure fluctuations, are universal constants. This prediction is too strong and not observed. A careful consideration of bottom effects invalidates the standing wave approximation. Nevertheless a weak version of the standing wave approximation still holds and has interesting implications. While the ratios of entries in the power spectral density matrix due to surface wave generated noise are not universal constants, they are insensitive to the details of the surface wave spectrum. This theoretical prediction is borne out by data from the Hawaii-2 Observatory. [Work supported by ONR.]
Animal hearing.
Authors: Dooling Robert J.
Published: March 2010

The auditory world of animals is, in many cases, quite different from our own due to evolutionary pressures that have created anatomical and physiological differences in auditory structures. However, there are a number of commonalities of function and mechanisms across many species that point to general concepts of auditory perception. This tutorial lecture explores the field of animal hearing, also known as comparative psychoacoustics. Because the diversity in hearing organs among animals is considerable, the hearing of many animals is quite different from our own. We will review some of these differences in hearing across animal groups, from household pets to more exotic animals. This tutorial also highlights the specific advantages of the comparative approach and illustrates the many creative methods used for behavioral testing of hearing in animals. Species comparisons contribute to our understanding of the evolution of the auditory system and can often clarify the relationship between structure and function in the auditory system as well as the effects of damage and repair. The study of animal hearing can lead to improved understanding of human auditory capabilities and invites speculation about how human speech is adapted for intraspecies communication.
Acoustic ducting and refraction by sea bottom relief in shallow water.
Authors: Lynch James F. , Shmelev Alexey A. , Lin Ying-Tsong , Newhall Arthur E.
Published: March 2010

Observations show that shallow water bottom relief often has a band-limited directional spectrum produced by various oceanographic and geological processes. This directional bottom feature is shown to have a noticeable effect on three-dimensional low-frequency acoustic propagation. An analytical study with an idealized model of straight sea bottom ripples has shown that acoustic energy can be partially ducted between neighboring ripples, and this ducting will affect acoustic propagation in shallow water. In our work, we also study ducting and refracting due to idealized curved sea bottom ripples. Previous research has shown that non-linear internal waves can also create acoustical ducts. Comparative analysis of these two different ducts is performed using our idealized model. The combined effects of internal waves and bathymetry are studied for various relative directions of internal wave front and bottom ripples. A numerical simulation of three-dimensional sound propagation across realistic bathymetry and internal wave fluctuations is performed. In conclusion, both water column fluctuations and bathymetry variability need to be taken into account when studying three-dimensional acoustic propagation in shallow water.
Spatial and temporal sound fluctuations in shallow water in presence of internal soliton in transition areas.
Authors: Katsnelson Boris , Malikhin Andrey
Published: March 2010

Behavior of the sound field is considered in a 1–2-h time interval in presence of train of internal soliton (IS) crossing an acoustic track. During this period moving ISs pass through several stages: approaching an acoustic track, consequent covering source (receiver) only, both source and receiver, receiver (source) only, and receding from an acoustic track. Correspondingly there are different regimes of interaction of the sound field with IS: horizontal reflection, capture of signals in horizontal waveguide, adiabatic variations, and transition areas between these regimes. So, rather complex spatial and temporal structure of the sound field takes place, including frequency and modal dependence of its parameters. Theoretical analysis of variations in the sound field on the basis of techniques of vertical modes and horizontal rays (PE in horizontal plane) is carried out, and estimation of feasibility of an experimental setup is presented. [Work was supported by CRDF.]
Arrival structure variability of single-bounce paths for high-frequency transmissions during the experiment KAM08 (Kauai acoustics communications multidisciplinary research initative 2008).
Authors: Senne Joseph M. , Song Aijun , Smith Kevin B.
Published: March 2010

During the summer of 2008 an experiment was conducted that included both chirp and M-sequence transmissions at 16-kHz center frequency. Source and receiver arrays were located west of Kauai Island HI, along an isobath of about 100 m. Moored thermistor strings and a wave-rider buoy provided detailed oceanographic data, while shipboard measurements recorded wind variations. Micro-multi-paths were observed from single surface bounces, and their variability has been examined for a variety of surface wave conditions. A surface wave model has been integrated into a parabolic equation model (MMPE) to approximate variations in the micro-multi-path structure over geotime. Model results are used to examine the correlation between environmental variability and observed single-bounce signal fluctuations. Comparisons are made with a variety of surface wave conditions, including both calm and rough seas. [Work supported by ONR 321OA.]
Blast induced electromagnetic pulses in the brain from bone piezolectricity.
Authors: Johnson Steven G. , Lee K. Y. Karen , Nyein Michelle K. , Moore David F. , Joannopoulos John D. , Socrate Simona , Radovitsky Raul
Published: March 2010

The mechanisms that might lead to in-brain electromagnetic pulses from an IED-scale explosive are considered, along with whether the resulting fields might have timescales and magnitudes relevant to neurological processes. In particular, due to known piezeoelectric properties of bone, it is possible for a shock wave incident on the skull to directly induce large electric fields within the brain. Using experimental data on the piezoelectric properties of bone combined with stresses from full-head-model blast simulations, the resulting in-brain electric fields shown to have timescales and magnitudes that exceed IEEE safety standards are comparable to procedures such as transcranial magnetic stimulation that are known to have neurological effects. Not only are such electromagnetic fields at least potentially relevant to the understanding of blast-induced traumatic brain injury but they may also lead to diagnostic tools in the form of blast dosimeters that measure blast-induced head stresses via the piezoelectric fields produced just outside the skull. [This work was supported by financial aid from the Joint Improvised Explosive Device Defeat Organization (JIEDDO) through the Army Research Office.]
Experimental and numerical evaluation of the effect of shock waves on the brain.
Authors: King Albert I.
Published: March 2010

A combined experimental and numerical study was conducted to elucidate the mechanical response of a head surrogate under air shock loading. A gel-filled egg-shaped skull/brain surrogate was exposed to blast overpressure in a shock tube environment, and static pressures within the shock tube and the surrogate were recorded throughout the event. A numerical model of the shock tube was developed using the Eulerian approach and it was validated against experimental data. An arbitrary Lagrangian–Eulerian (ALE) based fluid-structure coupling algorithm was then utilized to simulate the interaction of the shock wave with the head surrogate. A comprehensive parametric study was carried out to assess the effect of several key parameters on model response. The curvature of the surface facing the shock wave significantly affected both peak positive and negative pressures. Biological experiments exposing anesthetized rats to shock waves, using the same shock tube, produced brain injury in the form glial cell activation which in turn can adversely affect the function of axons and neurons. This injury mechanism is not the same as that for blunt impacts to the head which causes direct diffuse axonal injury.
Development of NASA Glenn Research Center auditory demonstration laboratory facility and operational capabilities.
Authors: Cooper Beth , Schmitt Jeff G. , Nelson David A.
Published: March 2010

The NASA Glenn Research Center Auditory Demonstration Laboratory (ADL) is a dual purpose facility, constructed in 2007 to support hearing conservation programs across the agency. Configured as a reverberant room, the ADL is an appropriate space for evaluating the performance of personal hearing protectors, using either human subjects or a test fixture. Hearing protector evaluations are conducted using NASA REATMASTER software, developed in partnership with the National Institute for Occupational Safety and Health. This software is available free on request to qualified laboratories, which are encouraged to participate in a collaborative program to fund continued software development. The ADL can also be configured as a free-field room to support the development of auditory demonstrations, widely used for a variety of training purposes within NASA and externally. The ADL provides an environment, sound system, and audio engineering tools for presenting and developing calibrated demonstrations of various acoustical and auditory phenomena that include fundamental acoustical and concepts, noise control principles, and simulations of hearing loss. Current work at the ADL will establish the capability of making three-dimensional surround sound recordings, which will expand the scope of the laboratory’s educational products into additional areas of psychoacoustics such as binaural hearing and localization.
Anechoic chamber verification for calibration of reference sound sources.
Authors: Herreman Kevin
Published: March 2010

Confidence in the capability of a testing facility to perform repeatable/reproducible product testing mandates study of each test chamber utilized by the facility. The Owens Corning Acoustic Research Center (OCARC) provides product sound power level determination for many differing product types ranging from the power generation, appliance, automotive, to medical equipment industry utilizing a fully anechoic chamber with a removable horizontal reflecting plane. Recently the OARC completed a verification study identifying the performance of the chamber relative to the requirements of test standard ISO 6926: Requirements for the performance and calibration of reference sound sources used for determination of sound power levels and ANSI S12.5: Requirements for the performance and calibration of reference sound sources. These standards provide strict guidelines for the repeatability/reproducibility of test results. This paper will review the verification testing process and present results from the study.
A cochlear analog bio-mimetic muffler.
Authors: Ramamoorthy Sripriya
Published: March 2010

A noise control device, the structural acoustic silencer, is designed by adopting the tailored structural acoustic filtering exhibited by the mammalian cochlea. In the cochlea, a flexible plate of gradually varying width and thickness separates the upper and lower fluid-filled ducts. Tailoring of the flexible plate properties enables frequency-specific localization of traveling waves, which are slowed down significantly at and near the site of resonance. While such slowing of the traveling wave leads to efficient energy coupling to the flexible plate thereby reducing transmitted acoustic fluctuations, the gradually varying impedance reduces reflections and allows the frequency-component to travel to its resonance site. The design of the bio-mimetic muffler employing non-biological materials is performed using three dimensional finite element analysis and validated against experimental data. The relation between coupled dispersion and transmission loss in the noise control device is explored. The coupled wave propagation in the engineered device is compared with the wave propagation in a passive cochlea.
Soundscape research in networking across countries: COST Action TD0804.
Authors: Schulte-Fortkamp Brigitte , Kang Jian
Published: March 2010

Soundscape, different from noise control engineering, is about relationships between human beings, sound environments, and society. Research in soundscape covers science, engineering, social science, humanity, and art, and it is related to many disciplines including among others acoustics, anthropology, architecture, ecology, landscape, noise control engineering, psychology, sociology, and technology. Soundscape research represents a paradigm shift in the field of environmental noise in that it combines physical, social, and psychological approaches and considers environmental sounds as a “resource” rather than a “waste.” The COST Action has built a vibrant international network and delivers the foundations for soundscape indicators, an integrated database of experimental and field data, publications, and tools to support design and decision making. Therefore, the paper will discuss the underpinning science and practical guidance that supports the measurement tools and their implementation in “Soundscapes.”
Harbor seals respond with aversion to 69-kHz pings: Implications for weighting procedures for marine mammal noise metrics.
Authors: Bowles Ann E. , Graves Stephanie K. , Shane Michael , Denes Samuel L.
Published: March 2010

Author Shane tracked cultured white seabass (Atractoscion nobilis) instrumented with 69-kHz ultrasonic coded transmitters (UCTs) in the vicinity of harbor seals (Phoca vitulina), later finding the bones of fish associated with UCTs. This led the authors to suspect that seals had targeted and eaten instrumented fish. To determine whether seals could detect pings, four harbor seals and a ringed seal at SeaWorld San Diego were exposed to pings from two 69-kHz and one 83-kHz UCTs and their spontaneous responses observed. The seals were not expected to respond strongly because most of the energy in the pings was close to the upper limit of hearing, but three of the four harbor seals reacted with aversion to the 69-kHz pinger with the highest source level (147 dB re 1 μPa), swimming into a refuge pool or jumping out of the water. The received level at the closest point of approach was estimated at 20 dB above sensation level or less. The results suggest that seals may be especially responsive to high-frequency tonal signals, and that broadband weighting functions may not consistently yield efficient exposure metrics. [Funded by NOAA; in-kind support from SeaWorld San Diego.]
Impact of building design on inpatient nursing unit noise levels: A case study of evidence based design.
Authors: Sevener Nathan
Published: March 2010

In spring 2006, the evidence-based design process was being applied to the design of the new inpatient pavilion at Lakeland Hospital. Because of survey feedback, the hospital was aware that noise detracted from patients satisfaction with the existing facility and therefore noise level became one of the 77 metrics used in the design of the new pavilion. To help create an improved acoustical environment, the sound levels in the existing facility were monitored, the design of the new pavilion was reviewed with respect to noise control, and follow-up measurements were made after occupation. The results of that effort are presented here.
Further studies in hospital noise control at the Johns Hopkins Hospital: Part 1.
Authors: Barnhill Colin , West James E. , Hsu Timothy , Ryherd Erica E.
Published: March 2010

Hospital noise levels remain well above World Health Organization guidelines. One of the main difficulties in treating hospital noise is the inability to use conventional sound absorption techniques. In intensive care units, the hospital does not allow any materials that can harbor bacteria or produce a high level of dust. This criterion prohibits conventional drop ceilings and conventional sound absorbing panels and carpet. Based on our previous panel design [M. MacLeod et al., “Weinberg 5C: A case study in hospital noise control, J. Acoust. Soc. Am. 119, 3327 (2006)] a lower cost version of our hospital noise panels was implemented by replacing the wrapping with DuPont™ Tyvek©. The lowered cost makes implementation of these new panels more feasible for hospitals. In this talk, it will be shown that this new implementation produces comparable results to the original panel design. The performance of a modified DL2 measurement will be investigated as a new way to characterize hospital noise.
Further studies of hospital noise control at the Johns Hopkins Hospital: Part 2.
Authors: Hsu Timothy Y. , Ryherd Erica E. , West James E. , Barnhill Colin L. , Swisher Marie , Levit Natalia
Published: March 2010

It has been shown through previous research that hospital noise levels continue to rise and that there exist potential health and occupational hazards due to the soundscape. Previous studies have examined parameters such as overall average sound levels, statistical distributions of levels, and frequency content in a variety of wards. However, studying the impact of sound absorbing materials in medical facilities is still very challenging due to strict infectious control requirements. We will present a case study on installing various sound absorbing treatments in four hematological cancer wards. Four units in the Weinberg Building of the Johns Hopkins Hospital were selected due to their identical geometries, similar staff activities, and similar patient acuity levels. Researchers installed different acoustical treatments in each ward, from untreated to fully treated with prototype materials. The prototype materials tested consisted of a layer of DuPont™ Tyvek® covering a panel of fiberglass acoustic absorbing material. In each ward, extensive acoustical measurements were taken and a questionnaire survey was administered to the registered nurses on staff. Preliminary results will be presented that compare and contrast attributes such as background noise, reverberation, speech intelligibility, and subjective perception in the four different wards.
Simulation of nonlinear acoustic waves based on the semi-Lagrangian method.
Authors: Silva Glauber T. , Nachbin Andre
Published: March 2010

In this work, we introduce the semi-Lagrangian numerical method for one-dimensional nonlinear wave propagation in acoustics. The method is suitable to simulate interacting waves in fluid media. In the method, the acoustic fields are expressed in terms of Riemann invariants. These variables are computed along the characteristic curves one step back in time. The unknown characteristics are obtained by the Runge–Kutta method. The Riemann invariants are evaluated in the grid points using cubic interpolation. The method is validated comparing the numerical solution to the Earnshaw solution for simple waves. Results show that the proposed method excels the Courant–Frederich–Lewy condition at least fourfold. The total numerical error is 12% and 3% using 16 and 32 points per wavelength, respectively. The proposed method is applied to simulate the interaction between a finite-amplitude tone with a Gaussian noise. Solutions are in qualitative agreement with earlier studies on tone and noise interaction [D. A. Webster and D. T. Blackstock, J. Acoust. Soc. Am. 64, 687–693 (1978)]. [Work partially supported by CNPq.]
The speech-critical band for vowels in steady and fluctuating backgrounds.
Authors: Healy Eric W. , Crass Kimberlee A. , Apoux Frederic
Published: March 2010

Previous work investigating the frequency resolution employed to process English vowels indicated that the speech-critical band (S-CB) for vowels was greater than the psychophysical critical band. This result suggests that the density of information in the acoustic signal is below the resolving power of the auditory system, and therefore functional resolution is limited by the signal. In the current investigation, the S-CB for vowels was measured in steady and fluctuating backgrounds. Thirty-six normal-hearing listeners heard vowels in /hVd/ context. The stimuli were restricted in overall bandwidth to 1.5 octaves centered at 1500 Hz and presented using vocoder-like processing as 1, 3, 5, 7, 9, or 11 low-noise noise carrier bands. Recognition increased and reached asymptote as the number of constituent bands increased. The carrier bandwidth at performance asymptote was again found to be larger than the psychophysical critical band. Moreover, the resolution of the acoustic signal at performance asymptote was similar across conditions in which the stimuli were presented (i) in quiet, (ii) in steady noise, or (iii) in four-talker babble at various signal-to-noise ratios. These results suggest that the current measure of speech frequency resolution is robust across a number of adverse listening conditions. [Work supported by NIDCD.]
Release from speech-on-speech masking under degraded signal conditions.
Authors: Best Virginia , Marrone Nicole , Mason Christine , Kidd Gerald
Published: March 2010

Previously, Marrone et al. [J. Acoust. Soc. Am. (2008)] compared spatial release from masking (SRM) for a three-talker mixture of similar sentences in normal-hearing (NH) listeners and listeners with sensorineural hearing loss (HL). The HL group showed significantly less SRM. In an earlier study [Marrone et al., J. Acoust. Soc. Am. (2008)] the NH group showed less SRM when the masker sentences were time-reversed while in the colocated case a large “reversed-masker release” (RMR) was also found. To investigate these findings, some listeners from the HL group were tested in the reversed-masker conditions. The difference in SRM between listener groups was much smaller for reversed speech. However, the HL group also had much less RMR. Both the overall target-to-masker ratios (TMRs) at which comparisons are made and the spectral smearing associated with sensorineural hearing loss were likely factors, perhaps affecting amounts of energetic and informational masking. We explored these factors in a new group of NH listeners in a similar task with both forward and reversed speech systematically degraded. Performance was measured at seven TMRs for unprocessed as well as 32-, 16- or 8-channel vocoder speech. The results provide qualified support for an influence of TMR and spectral degradation on both SRM and RMR.
On the possible influence of spectral- and temporal-envelope cues in tests of sensitivity to temporal fine structure.
Authors: Micheyl Christophe , Dai Huanping , Oxenham Andrew J.
Published: March 2010

The role of temporal fine structure (TFS) in speech and pitch perception has attracted considerable attention. Recent studies have suggested sensitivity to TFS even at high frequencies (8 kHz), well beyond the known limits of phase-locking in mammals, and a reduced ability to use TFS in hearing-impaired listeners. These conclusions were based on tasks involving the discrimination of complex tones or iterated-rippled noise, which had different power spectra but were (a) bandpass-filtered in a way that reduced tonotopic excitation-pattern (EP) cues and (b) had random component phases to eliminate temporal-envelope (TE) cues. In this study, we examine the possibility that residual EP and/or TE cues may have been available to the listeners in these experiments. Analytical and computational analyses indicated that although systematic TE differences were absent at the level of the stimuli, they were likely present at the output of the cochlea. Empirical studies tested whether the available TE and EP information might have influenced performance. Preliminary results suggest that although listeners may not have been sensitive to the available TE cues, performance may have been influenced by EP cues in a way that could also explain the deficits shown by hearing-impaired listeners. [Work supported by NIH R01 DC05216.]
An overview of unmanned underwater vehicle noise in the low to mid frequency bands.
Authors: Holmes Jason D. , Carey William M. , Lynch James F.
Published: March 2010

Unmanned (autonomous) underwater vehicles offer a unique, cost-effective platform for performing ocean acoustic measurements and surveys because multiple systems can be deployed from a single research vessel. Various data surveys can be performed including on-the-bottom geo-acoustic surveys over large areas, sub-sea-surface turbulence and microbubble structure surveys, and bi-static fish population surveys. To take advantage of the autonomous survey capabilities of underwater vehicles, sufficient signal-to-noise ratio and acoustic aperture (resolution) are required for acoustic measurements. The most commonly used vehicle sonar systems provide images utilizing high frequency hull mounted arrays and sources. In the lower-frequency band (100 Hz–10 kHz), however, vehicle noise levels and aperture remain the two most significant challenges, especially for passive systems. Previous experimental and analytical work has shown that a towed array with synthetic aperture processing can be used to obtain the necessary aperture. The major challenge of vehicle radiated noise is the focus of this paper, and both measured and archival results on vehicle noise are presented including an overview of levels, spectral character, and noise mechanisms for several vehicles. In particular, fundamental vehicle propulsion system noise is discussed along with implications on measurement performance and possible mitigation strategies.
Vibro-acoustic analysis of aerospace structures and issues with the available commercial prediction tools.
Authors: Kolaini Ali R. , Kern Dennis L.
Published: March 2010

The results of vibro-acoustic modeling using the boundary element method (BEM) that predicts the acceleration responses at critical locations and at the interfaces of selected test articles are discussed. High fidelity acoustic tests were performed in a couple of cases and the results are used to validate the BEM predictions. The accuracy of the BEM and its ability to correctly predict the acceleration responses of lightweight structures are discussed in some detail. Also a combined system level BEM, consisting of structures very responsive to acoustic pressures, and force-limited base shake random vibration analysis was performed. We will discuss how these results may be used to derive random vibration specifications for the purpose of qualifying large and lightweight structures for flight. In this paper, we also discuss the commercially available vibro-acoustic tools that are used to predict the acoustic transmission losses and vibration responses of flight structures for lift-off (assumed to be diffuse) and transonic (turbulent boundary layer) acoustic fields. The pros and cons of using the statistical energy analysis, finite element analysis, BEM, and newly developed hybrid methods within these vibro-acoustic tools are discussed in some detail.
Noise control in Space Shuttle Orbiter.
Authors: Goodman Jerry R.
Published: March 2010

Acoustic limits in habitable space enclosures are required to ensure crew safety, comfort, and habitability. Noise control is implemented to ensure compliance with the acoustic requirements. The purpose of this paper is to describe problems with establishing acoustic requirements and noise control efforts, and to present examples of noise control treatments and design applications used in the Space Shuttle Orbiter. Included is the need to implement the design discipline of acoustics early in the design process and noise control throughout a program to ensure that limits are met. The use of dedicated personnel to provide expertise and oversight of acoustic requirements and noise control implementation has shown to be of value in the Space Shuttle Orbiter program. It is concluded that to achieve acceptable and safe noise levels in the crew habitable space, early resolution of acoustic requirements and implementation of effective noise control efforts are needed. Management support of established acoustic requirements and noise control efforts is essential.
Speech recognition in loud noise using an ear-insert microphone.
Authors: Pruthi Tarun , Despa Mihai , Juneja Amit
Published: March 2010

Think A Move, Ltd. has developed a patented ear-insert microphone which captures speech as acoustic vibrations inside the ear canal. These vibrations propagate to the ear canal through the flesh and bones in the human skull. A high density foam on the earpiece seals the ear canal when the earpiece is inserted. Tests show that this earpiece provides an average passive noise cancellation (PNC) of around 38 dB for noises in Aurora database. Using an in-house speech command recognizer, with a short enrollment phase, on a database of 19 speakers (11 females, 8 males), speaking a vocabulary of 56 commands, an average accuracy of 85% has been observed in 90 dBA of tank, military vehicle, and machine gun noises. To further demonstrate the noise robustness of the earpiece as compared to external microphones, pilot tests were conducted on a small set of speakers to recognize speech commands recorded simultaneously with an external microphone and our ear-insert microphone with our recognizer. Results show that while the accuracy of the recognizer drops to 27% in 90 dBA noise from 96% in quiet for external microphone, it only drops to 92% in 90 dBA of noise from 95% in quiet for internal microphone.
Voice conversion for enhancing various types of body-conducted speech detected with non-audible murmur microphone.
Authors: Toda Tomoki
Published: March 2010

Our proposed statistical voice conversion approach to enhancing various types of body-conducted speech detected with Non-Audible Murmur (NAM) microphone is presented in this talk. NAM microphone, one of the body-conductive microphones [Nakajima et al., IEICE Trans. Inf. and Syst., E89-D, 1–8 (2006)], enables us to detect various types of body-conducted speech such as extremely soft whisper, normal speech, and so on. Moreover, it is robust against external noise due to its noise-proof structure. To make speech communication more universal by effectively using these properties of NAM microphone, body-conducted speech enhancement techniques have been developed with a state-of-the-art statistical voice conversion algorithm [Toda et al., IEEE Trans. ASLP, 15, 2222–2235 (2007)]. The proposed techniques would bring a new paradigm to human-to-human speech communication: e.g., the use of body-conducted voiced speech for noise robust speech communication, the use of body-conducted unvoiced speech for silent speech communication, and the use of body-conducted artificial speech for speaking aid [T Toda et al., Proc. ICASSP (2009) pp. 3601–3604]. This talk gives an overview of these promising techniques and presents their applications. [This research was supported in part by MIC SCOPE.]
Using speech models for separation in monaural and binaural contexts.
Authors: Ellis Daniel P. , Weiss Ron J. , Mandel Michael I.
Published: March 2010

When the number of sources exceeds the number of microphones, acoustic source separation is an underconstrained problem that must rely on additional constraints for solution. In a single-channel environment the expected behavior of the source—i.e., an acoustic model—is the only feasible basis for separation. We have developed an approach to monaural speech separation based on fitting parametric “eigenvoice” speaker-adapted models to both voices in a mixture. In a binaural, reverberant environment, the interaural characteristics of an acoustic source exhibit structure that can be used to separate even without prior knowledge of location or room characteristics. For this scenario, we have developed MESSL, an EM-based system for source separation and localization. MESSL’s probabilistic foundation facilitates the incorporation of more specific source models; MESSL-EV incorporates the eigenvoice speech models for improved binaural separation in reverberant environments.
Dual stage probabilistic voice activity detector.
Authors: Tashev Ivan , Lovitt Andrew , Acero Alex
Published: March 2010

Voice activity detectors (VADs) are critical part of every speech enhancement and speech processing system. One of the major problems in practical realizations is to achieve robust VAD in conditions of background noise. Most of the statistical model-based approaches employ the Gaussian assumption in the discrete Fourier transform domain, which deviates from the real observation. In this paper, we propose a class of VAD algorithms based on several statistical models of the probability density functions of the magnitudes. In addition, we evaluate several approaches for time smoothing the magnitude response to achieve a more robust estimate. A large data corpus of in-car noise conditions is then used to optimize the parameters of the VAD, and the results are discussed.
The role of temporal modulation processing in speech/non-speech discrimination tasks.
Authors: You Hong , Alwan Abeer
Published: March 2010

In this paper, temporal modulation characteristics of speech and noise from the point of view of speech/non-speech discrimination are analyzed. Although previous psychoacoustic studies have shown that temporal modulation components below 16 Hz are important for speech intelligibility, there is no reported analysis of modulation components from the point of view of speech/noise discrimination. Our data-driven analysis of modulation components of speech and noise reveals that speech and noise are more accurately classified by low-pass modulation frequencies than band-pass ones [H. You and A. Alwan, in Interspeech Proceedings (2009) pp. 36–39]. Effects of additive noise on the modulation characteristics of speech signals are also analyzed. Based on the analysis, a frequency adaptive modulation processing algorithm for a noise robust automatic speech recognition task is proposed. Speech recognition experiments are performed to compare the proposed algorithm with other noise robust front-ends, including RASTA and ETSI-AFE. Recognition results show that the frequency adaptive modulation processing algorithm is promising and is of low complexity. [Work supported in part by NSF.]
Results of hermetic transform signal processing to enhance the resolution and array gain of underwater acoustic arrays.
Authors: Woodsum Harvey C.
Published: March 2010

Results of applying the discrete hermetic transform (DHT) to the beamforming of underwater acoustic arrays are presented in terms of measured reductions in beam mainlobe width as well as the associated improvement in directivity index/array gain for practical cases of interest. Application of the DHT to array beamforming is shown to produce substantially enhanced resolution relative to the conventional beamforming diffraction limit as well as significant enhancement in array gain against ambient noise, without the use of data adaptive or nonlinear processing. As a result, enhanced sonar signal detection and/or the ability to use substantially smaller than normal arrays can be accomplished through the judicious use of DHT based beamforming algorithms. Results are favorably compared to theoretical predictions of algorithm performance.
Mode filters and energy conservation.
Authors: Udovydchenkov Ilya A. , Brown Michael G. , Rypina Irina I.
Published: March 2010

The discrete form of the mode filtering problem is considered. The relevant equations constitute a linear inverse problem. Solutions to problems of this type, including the mode filtering problem, are subject to a well-known trade-off between resolution and precision. But, unlike the typical linear inverse problem, the correctly formulated mode filtering problem is subject to an energy conservation constraint. This work focuses on the importance of satisfying, approximately at least, the energy conservation constraint when mode filtering is performed. [Work supported by ONR.]
An ultra-low-frequency acoustic vector sensor.
Authors: Donskoy Dimitri M. , Cray Benjamin A.
Published: March 2010

Passive underwater acoustic surveillance and oceanographic studies, for the most, have not been conducted at ultra-low frequencies (ULFs), from 0.01 Hz to a few hertz. One of the primary reasons for neglecting ULF has been the lack of sensitive, and directional, ULF acoustic sensors. Existing, and many prototyped, vector sensor designs are inertia based and thus not well suited to ULF, typically these sensors that operate at frequencies well above 100 Hz. A new type of acoustic vector sensor, capable of operating within the ULF range and possessing unsurpassed sensitivity (minimal detectable signal levels well below 1 nm/s) was built, tested, and calibrated at the Naval Undersea Warfare Center, Newport, RI. The measurements have validated the proposed detection concept, provided initial performance parameters, and have set forth the foundation for designing the next generation of fieldable prototypes.
Modeling the acoustic vector field using parabolic equation and normal mode models.
Authors: Smith Kevin B.
Published: March 2010

Numerical algorithms for computing the acoustic vector field, i.e., particle velocity and pressure from an acoustic propagation model, are introduced. Implementation using both a parabolic equation and normal mode approach is considered. The parabolic equation model employed uses a split-step Fourier algorithm, although application of the technique is general to other parabolic equation models. Expressions for the normal mode equations are also presented for both coupled and adiabatic mode models. Results for a Pekeris waveguide are presented for a point source, prompting a brief discussion of multipath influence on the estimation of the direction of energy flow. Approximate analytic solutions are used to validate the general results of both models. Results for the range-dependent benchmark wedge are then presented and show generally good agreement between the two types of models. The results from the two-way, coupled normal mode model provide potential benchmark solutions for the wedge and a means of confirming the accuracy of other models. [Work supported by ONR 321OA.]
Determination of the location of a sound source in three dimensional based on acoustic vector sensors on the ground.
Authors: de Bree Hans Elias
Published: March 2010

An acoustic vector sensor (AVS) consists of three orthogonal particle velocity sensors in combination with a sound pressure microphone. In several publications it has been proven that multiple sources can be located in three dimensions with a single AVS. In this paper it will be shown that it is possible to measure the instantaneous location (this means bearing, elevation, and range) of a single dominant sound source in three dimensional space as well as the angle dependent local ground impedance. Theory as well as results of experiments will be presented.
Estimating density from single hydrophones by means of propagation modeling.
Authors: Küsel Elizabeth T. , Mellinger David K. , Thomas Len , Marques Tiago A. , Moretti David J. , Ward Jessica
Published: March 2010

A density estimation method developed under the project Density Estimation for Cetaceans from passive Acoustic Fixed sensors is presented. It uses sound propagation modeling to estimate the probability of detecting an animal as a function of its distance from the receiving sensor. Two case studies involving Blainville’s beaked whales (Mesoplodon densirostris) and sperm whales (Physeter macrocephalus) are analyzed. The study area is the Atlantic Undersea Test and Evaluation Center in the Tongue of the Ocean, Bahamas. A ray-tracing acoustic propagation model is used to estimate the environmental transmission loss as a function of depth and range in several directions away from a single hydrophone. The computed transmission loss is compared to ambient noise levels, source level, and beam pattern distributions available in the literature to estimate detection probability as a function of range. Detection threshold is characterized from the signal-to-noise ratio of detected clicks. Information on click production rate is also taken into account by the density estimation model. Beaked whale detection probability function provides a relevant comparison to both the detection function and the spatial density of whales derived empirically from the DTag data by Marques et al. [(2009)].
Population density of sperm whales in the Bahamas estimated using propagation modeling.
Authors: Mellinger David K. , Küsel Elizabeth T. , Thomas Len , Marques Tiago , Moretti David , Baggenstoss Paul , Ward Jessica , DiMarzio Nancy , Morrissey Ron
Published: March 2010

The population density of sperm whales is estimated using an acoustic model to calculate the probability of receiving their clicks. The model uses estimates of (1) the source level of clicks, (2) the beampattern of the whales’ emitted clicks, (3) the distribution of whale orientations, (4) the loss between source and receiver (derived from acoustic propagation modeling), (5) noise levels at the receiver, (6) the detector’s rates of missed calls and false detections, and (7) sperm whales’ average click rate. These data are combined in a model that propagates simulated clicks from whales at various simulated positions to the receiving hydrophone to estimate the detection function—the probability of receiving a click as a function of distance. This function is then combined with information on whale click rates (performed at a chosen time of day when sperm whales appear to click at a measurably predictable rate) to estimate the population density corresponding to the number of received clicks in a given period of time. Data from the U.S. Navy’s Atlantic Undersea Test and Evaluation Center (AUTEC) in the Bahamas are used to estimate sperm whale population density there. [Thanks to ONR, NOAA, and the Navy’s Environmental Readiness Division for funding.]
Density estimation of leopard seals using a single stationary passive acoustic sensor.
Authors: Klinck Holger , Constantinou Nadine , Mellinger David K. , Rogers Tracey
Published: March 2010

The objective of this study is to estimate the spatial density of leopard seals using data recorded with a single stationary passive acoustic recording system in the Bransfield Strait, Antarctica, between 2005 and 2007. The most prominent vocalization of the leopard seal—the low double trill (LDT)—is used as a proxy for the presence of the species in the vicinity of the recording system. Because of the stereotypic nature and high frequency of occurrence of the LDT, a long-term spectrogram approach can be applied to the data sets to reliably detect the presence of the target species. Energy levels in the target frequency band (200–400 Hz) as derived by the long-term spectrogram analysis are related to number of manually counted calls extracted for selected periods. A linear regression analysis showed that energy levels are highly correlated with the number of manually counted calls. The number of recorded calls per unit time is converted into number of vocalizing animals per unit time by applying published calling rates for this species. In a last step of the analysis, the detection area is defined and leopard seal densities estimated. Opportunities and challenges of the method will be discussed.