bluuebunny/crossref_metadata_2025 huggingface dataset:
Ambient noise imaging simulation using Gaussian beams
Authors: Chitre Mandar A. , Potter John R.
Published: July 2002

Ambient noise imaging at high frequencies (10–100 kHz) and over short ranges (10–100 m) has been successfully simulated in the past using conventional ray tracing, combined with a Helmholtz–Kirchhoff integral approach to evaluate scattering from relatively large targets. This worked well for the design of ADONIS, the first Acoustic Daylight camera, but lacked realistic diffraction and surface roughness effects which were thought to be important in some scenarios. Furthermore, data acquired using ADONIS and other coastal ambient noise measurements have indicated that more attention should be paid to snapping shrimp as sources in warm shallow water. These sources have a rich spatial and temporal statistical behavior which have been exploited in a new generation of imaging algorithms, and now designing a second-generation ambient noise imaging (ANI) system is possible. We have an improved simulation algorithm which has therefore been developed using Gaussian beams, to investigate the feasibility and performance of a second generation ANI camera. The new simulation includes diffractive corrections and rough surface effects. The results confirm that ANI cameras can be expected to work well in warm coastal environments out to distances of at least several hundred meters. The algorithm design and some simulations will be presented.
The law against fetal protection policies for reproductive health hazards in the workplace: Implications for noise and vibration exposure
Authors: Feitshans Ilise L.
Published: July 2002

Is there a legal basis for employing special risk assessments or other preventive strategies to protect fetal health when pregnant women are exposed to potentially dangerous levels of occupational noise and vibration that may cause adverse effects on pregnancy outcome or cause hearing loss? A fetus in utero is highly susceptible to risks from toxic or hazardous agents in the workplace. Yet, complex litigation before the U.S. Supreme Court in IUAW v Johnson Controls held that fetal protection policies are illegal. The Court held that despite the risks to female employees of ‘‘childbearing age and capability’’ the law prohibits excluding women from well-paying jobs that have high lead exposure. While articulating women’s equal opportunity to work in high-risk occupations during or before pregnancy, the Court did not require risk assessment or state guidelines regarding possible maternal or fetal exposures to workplace harms. This paper will explore legal underpinnings of fetal protection policies under Title VII discrimination law, the Occupational Safety and Health Act of 1970, and the related precedents concerning fetal protection to consider for the first time, the implications of these laws in workplaces where pregnant women are exposed to hazardous levels of noise and vibration.
Sound velocity measurements in partially water saturated sand
Authors: Velea Doru , Sabatier James M. , Shields F. Douglas
Published: July 2002

The addition of small amounts of gas into a fully saturated sand drastically reduces the sound velocities in that material. The technique used to wet the sand in a series of experiments was to allow the water to be pulled into the granular material by capillary action. This process can entrap various amounts of air, depending on the grain size and the negative tension under which the water is allowed into the sand. The moisture content was measured using the time domain reflectometry method. Compressional and shear-wave velocities were measured as a function of water content in the sand. An average of 15% decrease in velocity was observed as the water content was increased from room dry state to 97% saturation. The change in velocities over this saturation range can be largely attributed to the change in bulk material density. The saturating technique used in these experiments did not achieve a high enough saturation range where a significant increase in compressional velocity has been observed. [Work supported by ONR.]
Comparison of BEM and FEM for computation of acoustic resonant response in a laser chamber
Authors: Baker Mary , Blelloch Paul
Published: July 2002

For lasers used in the computer chip etching process, laser performance, as measured by uniformity in the energy output for etching, is affected by the density of the chamber gas at the laser electrode. The laser produces longitudinal shock waves that propagate transverse acoustic pulses. Acoustic modes of the gas within the laser chamber respond to these pulses and can create a resonant response resulting in a very nonuniform energy output of the laser. These phenomena have been studied using finite-element (FEM) and boundary-element (BEM) methods to model the laser chamber and to predict the forced response. The effectiveness of these two approaches is compared. Accuracy, computing efficiency, and ease of modeling have been considered. The challenge that is addressed is the representation of the internal structure within the chamber. The baffling effects of the internal structure provide the means to shape the response either exaggerating or attenuating the resonance. BEM and FEM methods are explored as design tools to predict the response and achieve the desired uniformity of pressure and density.
Sensory and cognitive sources of individual differences in the ability to recognize speech
Authors: Watson Charles S.
Published: July 2002

Evidence in support of several generalizations about individual differences in speech recognition will be reviewed. First, the range of these abilities among normal-hearing adults appears to be reliable and large enough to be of some functional significance. Second, auditory spectral and temporal acuity, as measured with nonspeech sounds, fail to account for individual differences in speech recognition, although they may be weakly related to them. Third, a portion of the speech recognition variance among listeners is measurable with both speechreading (vision-only) and with auditory-only tasks, suggesting a central or cognitive origin. Fourth, the variety of types of distortion or transformation that fail to render speech unintelligible implies that very little necessary information is encoded in the fine structure of the speech waveform. Last, low correlations with general intelligence and with the ability to recognize environmental sounds suggest that speech recognition may be a relatively independent cognitive skill. Relevance of these conclusions to speech recognition by impaired listeners also will be considered. [Research supported by NIDCD and AFOSR.]
Localization with artificial head recordings
Authors: Sandvad Jesper , Christensen Flemming , Olesen Soeren K. , Moeller Henrik
Published: July 2002

Twelve artificial heads, of which one was designed at the authors’ laboratory, were evaluated in a localization test. The localization performance was compared in two situations: First, the subjects localized sound sources in a real sound field, then the localization test was repeated with artificial head recordings of the same sound field. The sounds to be localized were loudspeaker reproductions of female speech at natural level, from 19 different positions in a standard listening room. The artificial head recordings were reproduced by carefully equalized headphones. Results from eight of the heads showed an increased number of localization errors compared to real-life performance. The directions in the median plane were most often confused, not only with nearby directions, but also with directions further away. The number of errors was significantly higher than what can be obtained with recordings from a carefully selected human head. Results from the last four heads, including the one from the authors’ laboratory, were not available at the time of abstract submission.
Three-dimensional forward look sonar system
Authors: Cuschieri Joe M. , LeBlanc Lester
Published: July 2002

As part of an ongoing research effort related to new sonar systems, a system that can directly generate 3-D images of the underwater terrain has been developed. This 3-D forward-look (3-D FL) sonar consists of a separate projector and receiver hydrophone. The projector has a 1 deg fan beam, which is electronically scanned in 1-deg steps within the forward sector of view (±60 deg). The receiver hydrophone array oriented crosswise to the projector array can simultaneously form 100 beams within ±50 deg, generating a profile for each of the positions of the projector fan beams. The sequence of profiles thus generated constitute a 3-D image of the underwater terrain or bottom targets. The system operates at 230 kHz with a 20% bandwidth. To speed the generation rate of the profiles a pseudorandom signal is used. The level of data processing required to generate the profiles is, however, significant. Test tank and stationary at-sea image data have been collected and will be presented. [Work sponsored by ONR.]
Recent results from the DARPA synthetic aperture sonar
Authors: Nelson Matthew A.
Published: July 2002

A synthetic aperture sonar (SAS) system has been developed by Dynamics Technology, Inc. (processing lead), and Hughes Aircraft Naval and Maritime Systems (hardware and operation). The system operates at 50 kHz and features a 3.2-m-long, 16-element linear array and a data acquisition system that records phase and amplitude information for each element. Towbody motion is estimated from information contained in the sonar data through the use of a type of long-track interferometry, aided by data from a simple motion compensation suite consisting of Doppler sonar and a single gyro. This combination compensates motion to levels correctable by standard SAR autofocus techniques modified for SAS. The system has demonstrated, at long ranges (up to 1000 m), high-resolution images (better than 20 cm), previously achievable only with high-frequency sonars at close range. The low-carrier frequency allows high-resolution imaging of the interior structures of submerged objects, recently demonstrated by SAS imagery revealing the rib and spar structure inside a wrecked PB4Y-2 airplane in Lake Washington. [Work supported by DARPA.]
Fiber-optic sensors for acoustic array applications
Authors: Dandridge Anthony
Published: July 2002

Over the past 7 years there have been a number of impressive demonstrations of fiber-optic acoustic sensor systems with surveillance grade capabilities. These demonstrations range from single-element and small six-element arrays tests conducted in the Arctic (1990 and 1992), to a 128-channel capacity (64-populated channels), horizontal line array deployed off Point Loma in 1996. These fixed, surveillance arrays have wider bandwidths and larger dynamic ranges that their piezoceramic counterparts. As well as fixed arrays, hull-mounted array demonstrations (such as the lightweight wide aperture array) have met the stringent Navy performance specifications while eliminating all the outboard electronics to reduce the systems life-cycle costs. The lightweight planar array approach is a viable candidate for the NSSN WAA. To reduce system costs further, planar array approaches using fiber optics appear to be the candidate of choice for the next generation of submarine mounted arrays. The other area attracting attention is that of the all-optical towed array, where the reduction in wet-end cost is the prime driver. In this system concept, engineering functions required for the operation of the array are accomplished by a suite of fiber-optic sensors for temperature, pressure, heading, roll, pitch, and strain.
Fiber-optic sensors for underwater sonar applications
Authors: Berliner Marilyn J.
Published: July 2002

An overview of fiber-optic sensor designs and performance for underwater sonar applications will be discussed. The sensor designs range from simple, coated fibers to mandrels wrapped with single or multiple layers of fiber. The measurable response of fiber-optic sensors is through changes in the phase of light in the fiber due to the internal components of strain. The assumed strain in models of the acoustic response of optical fiber sensors differs for the various sensor designs and often are derived from an analysis of deformations of a complex, composite structure. Another consideration in the design of fiber-optic sensors is structural resonances, which may interfere with acoustic performance. Comparisons of modeled and measured acoustic and static pressure sensitivities of various fiber-optic sensor designs will be presented along with laboratory measurements of vibration response.
Research projects in acoustics for high school mentorship students
Authors: Korman Murray S. , Dixon Bonnie S.
Published: July 2002

Since 1983, the Anne Arundel County Public Schools’ Gifted/Talented/Advanced Program Office and the Naval Academy staff have developed a partnership in a program that is commonly called ‘‘Mentorship at the U.S. Naval Academy.’’ The program joins two special needs: the students need for advanced academic experiences and research projects along with the Naval Academy’s (an undergraduate school) need for research assistants to help the professors. The mentorship program is an intentional nurturing process for high school students working in an academic, scientific, and authentic research project environment. These projects require skills that are beyond what the classroom teachers and the curriculum can offer to advanced students. The process involves an optimal match between student and mentor—involving applications, interviews, selection, project involvement, and growth. Students are expected to work 132 h over a full year, receiving 1/2 a Carnegie credit unit for every 66 h worked—that counts as additional credit only. The Physics Dept. ‘‘mentees’’ do research in acoustics. Over the years, seniors have performed experiments involving sound generation by turbulent jets, scattering of sound by turbulence or by bubbly flow, nonlinear acoustics, chaos, Fourier analysis, electronic or computer projects, music acoustics, and sonar projects like ray tracing.
Making decisions about populations’ and individuals’ hearing thresholds in terms of their life-long noise exposure histories
Authors: Royster Larry H.
Published: July 2002

Industrial safety and health personnel and professionals with various backgrounds often have to make decisions as to the potential correlations between populations’ and individuals’ hearing characteristics for either an assumed or known on-the-job noise exposure and either an assumed or known off-the-job noise exposure. The recently published ANSI S3.44 standard provides an additional tool in making these types of decisions. This paper will present several case history examples of using ANSI S3.44 in judging the level of protection that had been provided by the company’s hearing conservation program for the noise exposed population. The paper will also present the expected changes over time in the hearing of a population or an individual (using a more-likely-than-not judgment criterion).
A proposed method for allocation of compensation for noise-induced hearing loss
Authors: Johnson Daniel L.
Published: July 2002

The method proposed uses the area under a statistical distribution of hearing levels in which the hearing threshold level is above 25 dB. These areas, normalized to 100 individuals, can be calculated for both non-noise-exposed populations as well as populations with various noise exposures. The statistical distributions are calculated by the procedures outlined in ANSI Standard S3.44. One minus the ratio of the non-noise-exposed area to the noise-exposed area provides a fair means for the allocation of hearing loss between noise and presbycusis. This approach considers an individual as representative of a group of exposed workers. This idea was first proposed in Air Force Medical Research Laboratory Technical Report No. TR-80-032, September 1983, Wright–Patterson Air Force Base, OH.
Reliable cues to gender and talker identity are present in a short vowel segment recorded in running speech
Authors: Owren Michael J. , Bachorowski Jo-Anne
Published: July 2002

Based on the source-filter model, individual variation in vocal-tract anatomy has long been proposed to influence the acoustic realization of phonetic gestures. It is therefore noteworthy that humans are sexually dimorphic, with individuals being uniquely marked through variation in many anatomical features. Both observations apply to vocal-production structures, and sounds whose characteristics produce a high-fidelity ‘‘off-print’’ of underlying anatomy should therefore provide clear cues to gender and identity. Vowels are arguably optimal in this regard, as they reflect details of both source and filter components. This conception was tested using 15 instances of the utterance ‘‘Test n Test’’ recorded from each of 50 males and 75 females. Measurements of the vowel in the first ‘‘Test’’ were entered in discriminant-function classification. Using only fundamental frequency and a formant-based estimate of vocal-tract length, 1852 of 1875 (99%) tokens were correctly classified by talker gender. Using all variables, 593 of 750 (79%) tokens recorded from males were sorted by talker, while the comparable figures were 729 of 1125 (65%) for females. These results underscore the importance of differences in vocal- tract anatomy for individual variation in speech production and suggest a prominent role of vocalic sounds in indexical cuing. [Work supported by NIMH.]
Contrastive and noncontrastive nonmodal phonation
Authors: Blankenship Barbara
Published: July 2002

This study explores three manners of vocal fold vibration: modal (the standard mode of vibration), breathy (where the folds are held apart so that the glottis fully closes for only a very small portion of the vibration cycle), and laryngealized (where the folds are held stiffly and vibration is inhibited). Data from languages with contrasting modal and nonmodal vowels were compared with matching data from languages where nonmodal phonation on vowels is not contrastive, but rather is an effect of the preceding consonant. Three acoustic measures were used to determine the nature and duration of nonmodal phonation in Mazatec, Tagalog, Chong, Mpi, and Navajo. In the contrastive cases, nonmodal phonation never persisted through the entire vowel. It was proportionally longer, however, than in the noncontrastive cases. Results offer insights into articulator limitations, perceptually driven contrasts, and gender differences.
Acoustic comparison of the effects of coarticulation on the production of Japanese and American English vowels
Authors: Jenkins James J. , Strange Winifred , Nishi Kanae , Fitzgerald Brett H. , Trent Sonja A. , Thornton David H.
Published: July 2002

Cross-language similarities and differences in the acoustic variability of vowels as a function of speaking ‘‘style’’ (citation versus sentences) and phonetic context were explored by comparing the productions of four adult male native speakers each of American English (AE) and Japanese. Multiple instances of the 11 AE vowels /i, ■, e■̆, ε, æ, ■, ■, ■, o■̆, ■, u/ and the 10 Japanese vowels /i, ii, e, ee, a, aa, o, oo, ■, ■■/ produced in citation-form bisyllables in /hVba/ and in CVC syllables /bVb, bVp, dVd, gVg, gVk/ imbedded in a carrier sentence were analyzed. Formant values at three temporal locations within the vocalic nucleus (25%, 50%, 75%) of the CVC syllables were compared with ‘‘canonical’’ /hVba/ values to determine the amount of ‘‘target undershoot’’ and changes in dynamic formant structure as a function of consonantal context. Vocalic durations were measured to determine the extent to which speaking style and consonantal context influenced relative vowel length information in the two languages. Linear discriminant analyses were conducted to quantify the acoustic overlap within and across languages. Implications of these results for cross-language studies of vowel perception will be discussed. [Work supported by NIDCD and ATR.]
Computational approaches to relating consonant and sentence recognition test scores
Authors: Seitz Philip F. , Grant Ken W.
Published: July 2002

Several recent studies have investigated the predictive relations among phoneme, word, and sentence recognition tests [e.g., Olsen et al., Ear Hear. 18, 175–188 (1997)]. The present study addressed this issue computationally, using data from 29 older hearing-impaired subjects who performed audio–visual recognition of 18 consonants in VCV syllables, and key words in IEEE/Harvard sentences. It was hypothesized that the predictive relation between consonant and sentence test scores should be made stronger by explicitly modeling and adjusting for differences between the test materials. Two approaches were tested: (1) weighting scores for the consonants based on their frequency of occurrence in the sentence materials, and (2) using a large computerized English lexicon to obtain estimates of possible lexical confusions for the IEEE/Harvard key words based on the consonant confusion matrices. The coefficient of determination (r2) for the overall consonant and key word scores was 0.56 [Grant et al., J. Acoust. Soc. Am. 97, 3308 (1995)]. Neither the frequency weighting nor the lexical weighting of the consonant scores increased the r2. These results suggest that consonant and sentence recognition performance are related by a very general property of speech recognition, which is not subject to lexical mediation. [Work supported by NIH-NIDCD.]
Resolution of lexical ambiguity by emotional tone of voice
Authors: Nygaard Lynne C.
Published: July 2002

The present study was designed to evaluate effects of emotional tone of voice on perception of word meaning. In two experiments, listeners were presented with emotional homophones that had one affective meaning (happy or sad) and one neutral meaning and were spoken in either a happy, sad, or neutral tone of voice. In the first experiment, listeners were asked to make tone of voice judgments for homophones that had been low-pass filtered (condition 1) or were presented unaltered (condition 2). The results showed that the affective meaning of the homophone affected tone of voice judgments, but only when homophones were not low-pass filtered. When presented unaltered, tone of voice identification was more accurate when affective tone and meaning were congruent. In the second experiment, listeners were asked to transcribe the emotional homophones in three tone of voice conditions: happy, neutral, and sad. The results showed that listeners provided more affective transcriptions when the tone of voice was congruent. That is, listeners reported more happy transcriptions when the tone of voice was happy and more sad transcriptions when the tone of voice was sad. These findings suggest that emotional tone of voice can affect the selection of word meaning.
Yellow Shark ’95: Experimental and inversion results for broadband acoustic propagation over a soft clay bottom
Authors: Hermand Jean-Pierre , Siderius Martin
Published: July 2002

In May 1995, Saclant Centre performed broadband (200–800 Hz) acoustic measurements near Elba Island off the coast of Italy as part of the Yellow Shark ’95 experiments. The experimental site has a soft clay layer bottom that varies in thickness from 3 to 10 m and has a sound speed less than the water column. The data presented here are from a range-dependent transect where the water depth varies from 67 m at the source location to approximately 120 m at the vertical arrays located every 8 km from 8 to 40 km from the source. The vertical arrays were sparsely populated with just four hydrophones positioned throughout the water column. A modal analysis is given to explain the frequency bands where high transmission loss is observed in the data. The observed data are inverted by matching the fields with modeling results. That is, using range-dependent modeling, the bottom type was varied in a search to fit the large-scale features of the modeled and observed transmission loss data. The results show that large-scale features can be used to identify some properties of the bottom such as the existence and thickness of the slow clay layer.
Source localization bias due to forward model uncertainties in matched-field processing
Authors: Chapman N. Ross , Kessel Ronald T.
Published: July 2002

Matched-field source localization (MFSL) in range-dependent media requires fast realistic forward models of sound propagation. No model replicates the real environment in all its detail, however, which effectively means that the source is being localized in the wrong environment, at a position that may not agree with the actual. As a rule, the agreement improves as the model is made more realistic, but this usually increases the computation time and complexity of the model, especially in range-dependent environments. MFSL must, therefore, balance accuracy and speed against model realism. The objective here is to demonstrate and account for consistent errors in the estimated range and depth of a source when the forward model differs from the actual environment. Range bias is demonstrated for data collected in the Pacific Shelf sea trials, for example, when bathymetric variation was at first ignored for speed and simplicity in the MFSL analysis, and then taken into account using a simple bias rule. Range and depth biases due to incorrectly modeled sediment properties and bathymetry in range-dependent media are explored more generally using the theory of adiabatic modes and numerical simulations. [Work supported by ONR and Department of National Defence, Canada.]
Robert W. Young’s contributions to acoustical standards
Authors: Marsh Alan H.
Published: July 2002

The citation for the award to Robert W. Young of Honorary Fellowship in the Acoustical Society of America, and the accompanying encomium, mention Bob’s contributions to the development of national and international standards. The contributions were many, sustained, and important. Over a span of five decades since the 1940s, his contributions to acoustical standards cover a range of acoustical instruments; measurement and evaluation of sound fields in rooms, outdoors, and in the ocean; and acoustical terminology. The quality of acoustical standards produced through the Acoustical Society of America, the International Electrotechnical Commission, and the International Organization for Standardization has been enhanced through the efforts of Robert Young.
Target localization aboard a tone emitting robotic echolocation system with mobile receivers
Authors: Walker V. Ashley , Peremans Herbert , Hallam John C. T.
Published: July 2002

Using only two receivers, animals are able to determine the location of a target in three dimensions. Echolocating bats, which employ broadband calls, have access to spectral cues that may be used, in conjunction with interaural disparities of intensity (IIDs) and/or time (ITDs), to encode a 3-D target angle. This work addresses the question: what cues might a tone-emitting echolocator employ to determine target azimuth and elevation? To this end, a 6-degree-of-freedom robotic sensor head was built to investigate the direction cues that might be generated by the systematic pinnae scanning movements used by many species of tone emitting bats. The first strategy investigated was the use of receiver motion to rotate the SONAR horizon through discrete IID sampling positions so that a 3-D target angle can be resolved across IID readings taken at two or more receiver positions. Next, the change in amplitude measured by continuously scanning pinnae was used to create temporal cues, which vary systematically with the target angle. In this scheme, angular resolution depends upon scan speed (ms) rather than interaural separation (microsecond). Finally, the use of Doppler shifts to encode the target angle through the cosine law was investigated.
Estimating acoustic flow parameters for multiple echoes within a biologically motivated signal processing framework
Authors: Müller Rolf , Schnitzler Hans-Ulrich
Published: July 2002

It is hypothesized that proportional changes in echo amplitude and carrier frequency might aid obstacle avoidance in cf bats by means of acoustic flow perception. This approach appears to be feasible in principle for single targets, however, obstacle avoidance, unlike prey capture in midair, is invariably prone to constitute a multiple target problem, which has to be addressed in assessing the hypothesis’ validity. In order to map a compound excitation pattern formed by superposition of responses to multiple echoes back into target space by means of an acoustic flow approach, instantaneous (carrier) frequency and amplitude together with their first-order derivatives must be recovered individually for each echo to be perceived as a separate entity. The primal sketch serving as a substrate for this operation is impoverished in that it is only preserving response envelopes. At the same time, the system design might capitalize on knowledge about the transfer functions of the filter bank’s channels as well as at least a rough guess about the echo spectrum. Consequently, it is attempted to explain compound excitation patterns as a sum of superimposed responses to individual echoes, which are known for any given frequency location to a scaling constant.
Collapse of cavitation bubble induced during extracorporeal shock wave lithotripsy
Authors: Kodama Tetsuya , Takayama Kazuyoshi
Published: July 2002

The interaction of air bubbles attached to gelatin surfaces, rat’s livers, or rat’s abdominal aortas with underwater shock waves was investigated to clarify the tissue damage mechanism by cavitation bubbles induced during extracorporeal shock wave lithotripsy. The overpressure of the shock wave was 10.2±0.5 MPa (n=4). The initial bubble radii varied from 0.12– 3.06 mm. The subsequent collapse of the bubbles was recorded by a high-speed framing camera. The liver cell damage was histochemically evaluated. The bubble attached to the gelatin or rat’s liver surface migrates away from the surface with an oscillatory growth/collapse behavior after the shock wave interaction. The penetration depth of the liquid jet into the gelatin and the diameter of the subsequent damage pit on the surface depend on the initial bubble radius. The bubble near the rat’s liver surface or aorta surface tends to show the same behavior as for the gelatin. The elongation and split of the nuclei in the liver parenchyma in the direction of the liquid jet and the increase in the cell density within the circumference of the injured region are histochemically revealed.
Remote generation of shear wave in soft tissue by pulsed radiation pressure
Authors: Andreev Victor G. , Dmitriev Vladimir N. , Rudenko Oleg V. , Sarvazyan Armen P.
Published: July 2002

Remote generation of shear waves in tissues by a focused ultrasonic beam is the basis of a new acoustic method of medical diagnostics, namely, shear wave elasticity imaging [A. P. Sarvazyan, U.S. Patent No. 5,606,971, 1997]. The feasibility of SWEI was demonstrated recently in experiments with optical and NMR detection of ultrasonically induced shear waves in tissue phantoms. In the present study an SWEI system with ultrasonic detection of shear waves was designed and tested. The shear wave was excited inside an inhomogeneous tissue phantom using radiation force generated by the reflection of ultrasound from internal inhomogeneity. A focusing transducer of 6 cm in diameter and with 6-cm focal length was used. The carrier frequency was 2 MHz, and the intensity was varied in range from 10–30 W/cm2. The rectangular envelope was 0.2 ms in duration. Induced shear motion was evaluated using a 10-μs-long 3-MHz ultrasonic pulse by measuring the time delay for the pulse backscattered by moving inhomogeneities in the tissue. Maximum displacement in the propagating shear wave was over 10 μm, which agrees with theoretical predictions.
Acoustic systems for well logging at extreme temperature and pressure
Authors: Squire W. D. , Whitehouse H. J.
Published: July 2002

Various acoustic systems will be described briefly that have been studied and developed by one or both of the authors for use in well logging. Most of these systems have been developed with the goal of operating at extreme temperature (in some cases as high as 200 °C). A few of them have been developed with the additional goal of operating at extreme pressure (in some cases as high as 20 000 psi). A list of the systems to be discussed follows: a wireless telemetry system to transmit data from the bottom of the well to the surface, utilizing the drill pipe as an acoustic wave guide with zero-order torsional waves on the drill pipe as the data carrier; an oil and gas well passive listening device or an acoustisonde (a stethoscope or, as called by the petroleum industry, a noise tool); a wireless telemetry system to transmit data from the bottom of the well to the surface, utilizing the drill pipe as an acoustic wave guide with acoustic pulses in the drilling fluid (drilling mud) inside the drill pipe as the data carrier, with a data rate greater than existing mud pulse systems; an acoustic borehole televiewer technology with an order of magnitude finer resolution than existing systems; and advanced pressure release materials for use in acoustic transducers at extreme temperature and pressure.
Perspective directions of vector-phase methods application in acoustic-seismic environmental monitoring
Authors: Mit’ko Valery B.
Published: July 2002

Estimation of harmful influence parameters of acoustic-seismic fields is important in environmental complex monitoring to decide such problems as the determination of infrasound harbinger of tsunami, earthquake. Such enormous engineering structures as dams, power stations heat changers, and main pipelines are also infrasound sources and should be under control. Theoretical methods of sound field estimation are noneffective in low and underlow frequencies because of the simplifying assumptions. The mathematical model of vector-phase methods is based, for example, on solving for the integral on the closed surface. It permits one to define vector-kinematic characteristics of an acoustic field and its spatially-temporary distribution in controllable volume. The development of elastic wave-field parameter measurements and the creation of multicomponent receiver parks allow one to carry out background parameter measurement or responses to pulse influences with the purpose of heterogeneity localization in sedimental or radical layers of the researched area with minimal expense of energy and means for nature measurement realization. The presence of spectral composites as a result of local heterogeneities in the research area was established. It was noted that stream of power measurements provide the increasing signal/noise ratio up to 16–20 dB in different conditions.
Methods of correlating measured sound levels from an aircraft noise monitoring system with aircraft operations
Authors: Alverson Steve
Published: July 2002

The Port of San Diego, owner and operator of San Diego International Airport (SAN), maintains a comprehensive aircraft noise control program that is designed to minimize noise impacts from aircraft operations at San Diego International Airport—Lindbergh Field. One element of this program involves continuous monitoring of noise at 24 remote monitoring terminals in the neighborhoods surrounding SAN and the acquisition of aircraft flight track data. This paper explores methods used by the SAN Noise Information Department staff to correlate, using algorithms in the aircraft noise and operations monitoring system (ANOMS), measured aircraft sound levels with actual aircraft operations. The paper will discuss the use of sound level rise and decay times, frequency filters, timing of noise events between monitors, passive secondary surveillance radar (PASSUR) to acquire aircraft flight tracks, and aircraft situation display (ASD) information to identify aircraft only noise events. The paper will also discuss how measured aircraft noise levels are compared to computed aircraft noise levels to verify the accuracy of the annual community noise equivalent level (CNEL) contours. The CNEL contours are submitted to the State Department of Transportation in response to the State of California aircraft noise regulation reporting requirements.
Effect of temporal gaps on informational and energy-based masking
Authors: Sadralodabai Toktam , Neff Donna L. , Gleason Traci R.
Published: July 2002

The effect of a temporal gap on detecting a 1000-Hz tone in the presence of 60-dB SPL simultaneous maskers was examined. Ten-component, random-frequency maskers and broadband-noise maskers were used in a 2-AFC adaptive task. Random-frequency components were drawn from 300 to 3000 Hz, excluding a 160-Hz band around the signal. Temporal gaps of 10, 20, 40, 80, and 160 ms were tested, positioned either at the onset, center, or offset of either the signal or the masker. Without gaps, both signal and masker durations were 200 ms. To maintain equal energy across all conditions, level compensation was applied when gaps were employed. For temporal gaps in either the multicomponent or noise masker, masked thresholds consistently decreased as gap duration increased. Gaps in the masker appeared to provide a temporal window for detection of the signal. However, for gaps in the signal, masked thresholds decreased with the multicomponent masker, but remained constant with broadband noise masker. With multicomponent maskers, the gaps appeared to reduce informational masking by perceptually segregating the signal from the masker. With broadband noise maskers, there was little informational masking and therefore the temporal gaps did not improve performance. [Work supported by NIDCD.]
Neural responses to the onset of voicing are unrelated to other measures of temporal sensitivity
Authors: Sinex Donal G. , Chen Guang-Di
Published: July 2002

Voice onset time (VOT) is a temporal cue that can distinguish consonants such as /d/ from /t/. We have previously shown that neurons’ responses to the onset of voicing are strongly dependent on their spectral sensitivity. This study examined the relation between neurons’ temporal sensitivity, determined from responses to amplitude-modulated tones, and the same neurons’ responses to the onset of voicing. Responses to VOT syllables and two types of modulated tones were obtained from low-frequency neurons in the inferior colliculus (IC) of the chinchilla. Both VOT and the modulation period varied from 10–70 ms in 10-ms steps. Neurons that respond selectively to modulated tones might be expected to respond strongly to the syllables whose VOTs match the preferred modulation periods. However, for most neurons the correlation between discharge rate to modulated tones and voicing onset was low. Some neurons exhibited moderate selectivity for certain modulation periods, but this selectivity was usually unrelated or even inversely related to the same neurons’ selectivity for VOT syllables. Overall, responses to modulated tones did not account for the responses of IC neurons to the complex temporal cues associated with the onset of voicing. [Work supported by NIDCD.]
A study of speaker adaptation of continuous density hidden Markov models
Authors: Raghavan Prabhu , Che Chiwei
Published: July 2002

Considerable research in the area of speech recognition, in the past two decades, using HMMs has led to successful reduction in word error rates (WER). Owing to their statistical nature, HMMs require large amounts of data to get good estimates of the model parameters. It has been shown that a speaker dependent (SD) model has about 2–3 times less WERs compared to a speaker independent (SI) model. But the heavy data requirement from one speaker is quite unreasonable. Speaker adaptation techniques mitigate this problem by the use of SI data to obtain robust estimates and then use small amounts of SD data to adjust these parameters so that they are optimal to that speaker (in some optimality criterionlike ML). In this paper, the different techniques of adaptation are studied. The salient methods, namely MLLR and MAP, of each type are discussed in detail. A method of constrained unsupervised adaptation, which discards parts of the original hypothesis that are deemed to be incorrect, is proposed. This decision is made on past experience obtained on training data. This decision making module uses a neural network and a CART tree.
An aeroacoustic fricative source model
Authors: Sinder D. , Krane M. , Flanagan J.
Published: July 2002

A model for fricative sound generation based on aeroacoustic theory is implemented in an articulatory synthesizer. The aeroacoustic model is based upon Howe’s reformulation of the acoustic analogy, which allows the source to be specified in terms of the jet formed at a constriction, the shape of the vocal tract walls, and the acoustic loading due to the lip termination. As such, the model uses existing acoustic models for the vocal tract combined with an approximate model for the behavior of the jet based on turbulence theory and experiment. This allows the fricative source strength, impedance, and temporal characteristics to be specified using the lung pressure, the constriction diameter, and the shape of the vocal tract downstream of the constriction. Evaluation of the source model is presented. Computed estimates of fricative source characteristics are presented and compared to source models used by other investigators. A comparison of synthetic fricative sounds generated using these models is also presented. [Research supported by NSF/ARPA IRI-9314946 and ARPA DAST 63-93-C-0064.]
An HMM-based measure for evaluating the quality of foreign-accented speech
Authors: Smith Robert , Aikawa Kiyoaki , Takahashi Satoshi
Published: July 2002

A new criterion for measuring the quality of foreign-accented speech is proposed. The proposed criterion uses both the absolute and relative quality scores produced by an HMM speech recognizer. An absolute scoring function is determined by the difference of likelihood distributions between the correct phone HMM and an incorrect phone HMM for a speech segment. A relative scoring function is established to discriminate a delta-self value distribution from a delta-sub value distribution. A delta-self value is obtained by the likelihood score difference between the correct model and an incorrect model for a speech segment. A delta-sub value is obtained by the likelihood score difference between two incorrect phone models against the speech segment. The new idea is motivated by the following evidences. It is sometimes found that the absolute score is low, even if the speech segment sounds correct. In that case, however, the relative score is still high for the speech segment. This may happen because the HMM parameters were not chosen for evaluating voice quality. The best speech quality meets a condition that both the absolute and the relative scores are high. A practical integrated measure is the linear combination of the absolute and the relative scoring functions.
Parsing the contribution of lip and tongue position to fricative noise frequency
Authors: Whalen D. H. , Gick Bryan
Published: July 2002

The English alveolar and palatal fricatives have, as part of their realization, high-frequency noises that are shaped both by the rounding and protrusion of the lips and the position of the tongue on the hard palate. The acoustic effects are of two main types, influence on the main spectral resonance of the noise, and the frequency and intensity of a second formant resonance within the noise. However, the exact contribution of each of these articulatory factors to the two acoustic effects is not known. The present study used electromagnetometer measures of tongue and lip location and video-based measures of lip aperture, area, and protrusion. Initial data indicate that area of the lip opening correlates significantly with F2 resonance, while tongue position correlates with fricative pole. Surprisingly, upper lip protrusion correlates with both the F2 resonance and the fricative poles. These preliminary results suggest that both lip and tongue configuration contribute to the shape of the fricative poles, while the F2 resonance is primarily dependent on the lip configuration. Implications for perceptual parsing will be discussed. [Work supported by NIH grant DC-02717.]
Predicting pharynx shape from the tongue during vowel production
Authors: Kang Min , Whalen D. H. , Magen Harriet
Published: July 2002

The shape of the pharynx greatly affects the formants of vowels, yet the measurement of pharyngeal shape is relatively difficult. Using midsagittal MRI images of a male speaker producing eleven English vowels, the predictability of pharyngeal shape during vowel production was assessed. There were two categories of predictors: measured and categorical. Measured predictors were four points on the tongue representing the points likely to be locations for receiver coils in an electromagnetometer system. Categorical predictors were vowel frontness and height, and the typical position of the epiglottis relative to the base of the tongue (as seen in MRI images). Midsagittal distance was measured at 3-mm intervals along the vocal tract length. A stepwise regression using measured and categorical variables gave good predictions for all distances along the vocal tract (r greater than 0.80), except near the uvula. (Using just the categorical predictors resulted in surprisingly good estimations.) Position of the uvula varied across repetitions of the vowels, and so exclusion of the uvula increased predictability in the uvular region. For static vowel patterns in English, then, pharynx shape is fairly predictable from tongue shape. [Supported by NIH grant DC-02717.]
An automatic speech recognition system using time-delays self-organizing maps with physiological parametric extraction
Authors: Ferrandez Jose M. , del Valle Daniel , Rodellar Victoria , Gomez Pedro
Published: July 2002

Physiological parametric extraction uses auditory models as a front end for speech recognition. These last methods assume that if speech signals are coded in the same way that the auditory system does, speech could be later identified showing the main properties that biological systems do: robustness and accuracy. The proposed system consists of a cochlear model implemented by gammatone filterbanks as proposed by Patterson [J. Acoust. Soc. Am. 96, 1409–1418 (1994)]. This stage will feed a nonlinear mechanical-to-neural transduction module based on the Meddis hair-cell model [J. Acoust. Soc. Am. 79, 702–711 (1986)], which will compute auditory-nerve firings. Finally, a temporal integration/component–extraction module will integrate neural patterns for identifying the relevant components embedded in the speech signals [characteristic frequency (CF), frequency modulation (FM) and noise burst (NB)], which are shared by human speech and animal sounds for communication. The model adopts a spatiotemporal strategy, which uses temporal information in low CF fibers (phase-locking mechanism) and spatial information for the higher ones. The recognizing module consists in a time-delay self-organizing map, which will capture not only the spectral variability contained in the signal, but also the temporal one, providing better generalization properties. [Work supported by NATO CRG-960053.]