bluuebunny/crossref_metadata_2025 huggingface dataset:
Sediment tomography in the Middle Atlantic Bight
Authors: Potty Gopu R. , Miller James H.
Published: July 2002

Sediment properties such as compressional speed and attenuation have been extracted using the modal dispersion of explosive signals in the Middle Atlantic Bight. Data collected during the Shelf Break PRIMER experiment are used to generate sediment sound speed profiles along various propagation paths. Compressional speeds are inverted using traveltime of modes 1 to 9 from 10 Hz to 225 Hz. Compressional attenuation is inverted using modal amplitude ratios. Gravity cores taken at the experimental site give direct mesurements of compressional speed and attenuation for comparison. A posteriori estimates of resolution are evaluated. Nonlinear inversion techniques based on a Genetic Algorithm and Levenberg–Marquardt methods are used. Methods for increasing the efficiency of the inversion algorithm are also investigated. [Work supported by ONR.]
Tonal portrait of a pipe organ
Authors: Pollard Howard F.
Published: July 2002

Measurement techniques are described that enable the steady state tone color (timbre) of a musical instrument to be quantified. The system is applied to sounds from the pipe organ in the Great Hall of Sydney University. A one-third octave normalized loudness spectrum that is independent of pitch is derived for each set of notes from selected ranks of pipes. From the normalized spectrum, sharpness and tristimulus coordinates are computed, the latter being independent of both pitch and loudness. Measurements made on different ranks of pipes or made at different times are compared with the aid of spectrum dissimilarity and tristimulus diagrams.
The Rani Gumpha: A 2nd century B. C. acoustical theatre in India
Authors: Ault C. Thomas , Manthravadi Umashankar
Published: July 2002

The Rani Gumpha is a bi-level theatre, built in ancient Khalinga (now 5 km from Bhubaneswar, Orissa) by King Kharavela circa the 2nd century B.C. It is the first or Vikirsta type of theatre discussed by Bharat Muni in the Natyashastra, and is remarkably similar to the Hellenistic theaters of Greece, except that it has a square, not round, ground-plan. It is unique for its resonating chambers on the upper and lower levels which surround the performance space. We shall present a brief history of the site and, using visual and acoustical materials created from our on-site testing, demonstrate the effects of gain, resonance, and duration in the performance and spectator spaces. We shall also address vocal and instrumental range, harmonics, function of specific chambers and their interaction with the other chambers. Please note that this is a work in progress, not a complete or definitive assessment of the site. We anticipate that our colleagues will enhance our research through their shared expertise.
Determination of density and elastic constants of a thin phosphoric acid-anodized oxide film by acoustic microscopy
Authors: Zinin Pavel , Lefeuvre Odile , Briggs Andrew , Zeller Brent D. , Cawley Peter , Kinloch Anthony , Zhou Xiaorong , Thompson George
Published: July 2002

Quantitative acoustic measurements have been carried out on phosphoric acid-anodized (PAA) aluminum. This process creates a porous oxide layer which varied from 1 to 22 μm thick in the different specimens used here. The elastic properties of the PAA oxide layer were determined by measurements of the dispersion curves in the complex plane [speed of the surface acoustic wave (SAW) and its attenuation] alone. This was possible because two modes were observed on samples with thicker oxide layers. It has also been shown that the dependence of the attenuation on the oxide layer thickness around the cutoff can be used for the determination of the density of the layer. The shape of the attenuation curve measured by the acoustic microscope near the cutoff was smoother than predicted by the theory, and this phenomenon has been discussed.
Exact solution for sound propagation in ducts with an axial mean temperature gradient and particulate damping
Authors: Karthik B. , Mohanraj R. Krishna , Ramakrishnan Rajesh , Sujith R. I.
Published: July 2002

An exact solution for one-dimensional sound propagation in ducts in the presence of axial mean temperature gradient and particulate damping is presented in this paper. The acoustic wave equation is derived starting from the one-dimensional momentum and energy equation. The application of appropriate transformations leads to an analytically solvable Whittaker’s differential equation for the case of a linear mean temperature gradient and Bessel’s differential equation for the case of an exponential mean temperature gradient. The derived analytical solutions are used to investigate the dependence of the acoustic field in a duct on temperature gradient and particulate damping.
Acoustic scattering by a modified Werner method
Authors: Ravel Patrice , Trad Ahmed
Published: July 2002

A modified integral Werner method is used to calculate pressure scattered by an axisymmetric body immersed in a perfect and compressible fluid subject to a harmonic acoustic field. This integral representation is built as the sum of a potential of a simple layer and a potential of volume. It is equivalent to the exterior Helmholtz problem with Neumann boundary condition for all real wave numbers of the incident acoustic field. For elastic structure scattering problems, the modified Werner method is coupled with an elastodynamic integral formulation in order to account for the elastic contribution of the displacement field at the fluid/structure interface. The resulting system of integral equations is solved by the collocation method with a quadratic interpolation. The introduction of a weighting factor in the modified Werner method decreases the number of volume elements necessary for a good convergence of results. This approach becomes very competitive when it is compared with other integral methods that are valid for all wave numbers. A numerical comparison with an experiment on a tungsten carbide end-capped cylinder allows a glimpse of the interesting possibilities for using the coupling of the modified Werner method and the integral elastodynamic equation used in this research.
Predicting acoustic effects of internal waves from the basic climatology of the world ocean
Authors: Noble Kimberly J. , Flatté Stanley M.
Published: July 2002

Internal waves of a given strength will produce acoustic effects that vary from water mass to water mass. Presented here is a means of predicting the strength of acoustic fluctuations due to internal waves, given the basic climatology, that is, measurements of depth, temperature, and salinity of an oceanic region. An acoustic fluctuation strength parameter F is defined as the ratio of the fractional potential sound-speed change to the fractional potential-density change. Here F is calculated at three depth levels (275, 550, and 850 m), on a one-degree grid of latitude and longitude, using NODC/OCL’s World Ocean Atlas 1994. Representative values of F are presented for 15 upper water masses that range from F=5 in the North Pacific to F=34 in the North Atlantic, with a typical value for most of the upper waters being F=15. Results for two depth levels within 12 intermediate water masses range from F=7 in the North Pacific to F=62 in the North Atlantic, with a typical value of F=20, although there is considerable variation. In general, F exhibits higher values in the Atlantic Basin than in the Indian or Pacific, and has a maximum at 550 m. The main use of F will be the prediction of travel-time fluctuations in acoustic propagation experiments, which will be proportional to the value of F, given a universal strength of internal waves.
Hybrid tool for quickly estimating the radiated acoustic power from a vibrating structure in a multiple-source environment
Authors: Beslin Olivier , Foin Olivier , Nicolas Jean
Published: July 2002

This paper presents a new hybrid method for predicting overestimating and underestimating indicators of the acoustic power radiated by a vibrating surface even in the presence of other surrounding acoustic sources. This method is applicable to plates or low curvature surfaces radiating in open acoustic fields. The method is hybrid in the sense that the vibration field is measured and the parietal pressure field is predicted considering two extreme academic cases “baffled” and “unbaffled.” Many simplifications are made and justified in order to save running time. The method is successfully validated in comparison with experimental results on both laboratory and real life structures. This method has led to a quick tool, allowing one to obtain a good approximation of the radiated power in a few minutes. It provides a natural extension of a classical analyzer for vibroacoustics engineering.
Pitch estimation by early-deafened subjects using a multiple-electrode cochlear implant
Authors: Busby P. A. , Clark G. M.
Published: July 2002

Numerical estimates of pitch for stimulation of electrodes along the 22-electrode array of the Cochlear Limited cochlear implant were obtained from 18 subjects who became deaf very early in life. Examined were the relationships between subject differences in pitch estimation, subject variables related to auditory deprivation and experience, and speech-perception scores for closed-set monosyllabic words and open-set Bamford–Kowal–Bench (BKB) sentences. Reliability in the estimation procedure was examined by comparing subject performance in pitch estimation with that for loudness estimation for current levels between hearing threshold and comfortable listening level. For 56% of subjects, a tonotopic order of pitch percepts for electrodes on the array was found. A deviant but reliable order of pitch percepts was found for 22% of subjects, and essentially no pitch order was found for the remaining 22% of subjects. Subject differences in pitch estimation were significantly related to the duration of auditory deprivation prior to implantation, with the poorest performance for subjects who had a longer duration of deafness and a later age at implantation. Subjects with no tonotopic order of pitch percepts had the lowest scores for the BKB sentence test, but there were no differences across subjects for monosyllabic words. Performance in pitch estimation for electrodes did not appear to be related to performance in the estimation procedure, as all subjects were successful in loudness estimation for current level.
Edge diffraction of creeping rays
Authors: Chapman S. J. , Ockendon J. R. , Saward V. H.
Published: July 2002

Explicit formulas are derived for waves modeled by the scalar two-dimensional Helmholtz equation for the field that is diffracted when surface creeping rays encounter an infinitely sharp edge. Both Neumann and Dirichlet boundary conditions are analyzed, and the diffracted field is found to be an order to magnitude smaller in the latter case.
Performance limits of the broadband generalized sidelobe cancelling structure in an isotropic noise field
Authors: Nordholm Sven E. , Leung Yee Hong
Published: July 2002

In acoustic applications, the signal source of interest is generally broadband and the background noise field is predominantly isotropic. In this letter, the performance of the broadband generalized sidelobe canceller, optimized with respect to an isotropic noise field, is analyzed and compared against the performance of the conventional summing beamformer. The comparison is based on an ideal continuous-time infinite-length generalized sidelobe canceller with the aim of determining the performance limits of this beamforming structure.
Surface wave velocity determination by using reflection coefficient method on the liquid–anisotropic–solid interface
Authors: Xu Yang , Aizawa Tatsuhiko
Published: July 2002

Reflection coefficient of a plane wave impinging from liquid onto a liquid–anisotropic–solid interface is useful to theoretically predict the Rayleigh surface wave (RSW) velocity and the pseudo surface wave (PSW) velocity dispersions. In the present letter, several incomplete results proposed by previous investigation are restudied to attempt giving more appropriate physical understanding in theory. It is found that PSW velocity determined by the reflection coefficient analysis is just a nonleaky effect surface wave on the liquid–anisotropic–solid interface but not the leaky one.
Surface area measurement utilizing an acoustic bridge
Authors: Torigoe Ippei , Ishii Yasushi
Published: July 2002

A new method is proposed for measuring the surface area of an object. The acoustic conductance of a cavity is proportional to the surface area of the cavity inner wall. The surface area of an object thus can be known from the measurement of the acoustic impedance of a chamber in which the object is placed. In order to measure the acoustic impedance accurately, the proposed method employs the acoustic bridge technique. The experimental device is composed of the following elements so arranged that their electric equivalents form a bridge circuit: a measuring chamber in which an object under test is placed and whose volume can be adjusted; a reference chamber whose inner surface area can be varied; a loudspeaker (the signal source) mounted between the two chambers; and a bypass channel at the midpoint of which a microphone (the null detector) is installed. This bridge balances when the volume and the inner surface area of each chamber become equal. The surface area of the object can then be known from the inner surface area of the reference chamber. Several experiments were performed with this device and the success of the proposed method was verified.
Effects of acoustic trauma on acoustic enhancement of electrically evoked otoacoustic emissions
Authors: Nakajima Hideko Heidi , Hubbard Allyn E. , Mountain David C.
Published: July 2002

Moderate acoustic trauma results in decreased cochlear sensitivity and frequency selectivity. This decrease is believed to be caused by damage to the cochlear amplifier that is associated with outer hair cells (OHCs) and their nonlinear electromechanical characteristics. A consequence of OHC nonlinearity is the acoustic enhancement effect, in which low-frequency electrically evoked otoacoustic emissions are enhanced by a simultaneous tone. The present study found that acoustic trauma reduced the acoustic enhancement effect and this reduction is correlated with the N1 threshold at the electrode site. This result is consistent with the theory that trauma affects the mechanoelectric transduction process, thus affecting cochlear mechanical nonlinearity. Acoustic trauma also reduced the cochlear microphonic in a way that suggests that the number of functioning tension-gated channels and the stiffness of the gating springs were decreased. In some cases, the electromechanical transduction process was also found to be affected by acoustic trauma.
Acoustic barrier: BEM prediction and experimental verification
Authors: Gerges Samir , Arlinton Calza
Published: July 2002

This paper presents the noise attenuation of a barrier by BEM prediction, analytical formulas, and also experimentally. The analytical formulas used consider the diffraction of semi-infinte barrier, based on source image and phase change caused by the reflection of the sound waves from rigid ground surface. Numerical simulation by BEM and analytical calculation of the barrier model are compared and later validated by experimental tests with a barrier built in a semianechoic chamber. The results obtained by BEM prediction, analytical formulas, and experimental measurements are compared and the divergences between them are discussed.
Sound transmission through perforated panel with internal Helmhotz resonators
Authors: Solana Quiros Pedro E. , Picard Lopez Miguel A. , Arizo Serrulla Juan V.
Published: July 2002

The study of the passive control technique of noise through a perforated panel with resonators is useful in acoustic barrier design for both industrial and traffic noise. The loss mechanisms that reduce the energy of sound have been considered in the method for predicting the TL of compound flat panels containing Helmholtz resonators. A transmission coefficient is obtained for the system that relates the resonance frequency of the resonators for nonlinear resistance at the nozzle. The outer and the interior panels are assumed to act as simple mass reactances. In order to examine the validity of the analytical results, comparisons were made with experimental data. To provide acoustic excitation, a loudspeaker array was used. The excitation and transmitted sound fields were measured with a microphone array located on each side of the panel. The model predicts that a significant increase in TL can be expected at or near the mean resonance frequency of the system multilayer-panel–resonator array. In addition, a significant decrease in the TL is predicted at higher frequency. Also, it has been observed that as the ratio of the nozzle area divided by the resonator surface area increases, the frequency at which the peak TL occurs also increases.
Wave propagation experiments using point load excitation in a multilayered structure
Authors: Zhou Chunnan , Popovics S. John , Achenbach D. Jan
Published: July 2002

Transient wave propagation measurements on a single plate, a two-layer plate, and a two-layer-on-a-half-space structure are reported. The experiments are performed using point load excitation and point detection at the surface of the structure. The experimental results are used to verify the accuracy of a new model for wave propagation in layered structures. The basis of the model is first introduced. Experimental measurements using different wave sources, plate materials, and wave sensors are compared with each other and with theoretical results. The actual source functions for pencil-lead-break wave sources are obtained. Next, experiments performed on an aluminum plate bonded to stainless steel plate are reported. Both cases of stainless steel atop aluminum and aluminum atop stainless steel are considered. The experimental results show good agreement with the theoretical predictions. The effects of the second layer on the transient displacement of the top surface are discussed. Finally, a two-layer-on-a-half-space structure consisting of a stainless steel plate as the top layer, an aluminum plate as the second layer, and a thick acrylic resin block as the half space is studied. The presented experimental transient measurements agree with the predicted results, thus verifying the accuracy of the model.
The effects of airborne vibration on human body vibration response
Authors: Smith Suzanne D.
Published: July 2002

Aircraft ground operations and maintenance personnel can be exposed to whole-body vibration via the airborne transmission of acoustical energy. The purpose of this study was to characterize human body vibration response during exposures to airborne vibration generated by military fighter aircraft during high-power ground engine runs. Miniature triaxial accelerometers were mounted on the head (bitebar), chest, spine, and lower leg of the subject. Measurements were made for selected locations along a line parallel to the longitudinal axis of the aircraft at specified engine-power settings. The highest accelerations occurred in the fore-and-aft (X) chest response. One-third-octave analysis showed a distinct peak in the chest between 50 and 100 Hz not observed in the noise levels, strongly suggesting the presence of a chest resonance. These peaks increased as the subject moved aft of the aircraft. While the noise levels also increased, it was difficult to determine a relationship between acceleration and noise without additional data due to differences in the results between power settings. The subject did report an increased sensation of vibration in the upper torso, which coincided with the increased noise levels. These data will be used in the development of human airborne vibration exposure guidelines.
A study of human response to helicopter interior noise
Authors: Sullivan Brenda M. , Davis Mark W. , Young David L. , MacMartin Douglas G. , Millott Thomas A.
Published: July 2002

Two studies investigating low-frequency tonal content of rotorcraft noise were performed in a joint project between NASA Langley Research Center, United Technologies Research Center, and Sikorsky Aircraft. The first study investigated preference reported by subjects exposed to noise representing that experienced inside helicopters passenger cabins or crew compartments. The second study examined the use of computer-based tools to measure possible fatigue caused by long-term exposure to helicopter interior noise. In the first study subjects heard sounds with modified low-frequency rotor-generated tones, high-frequency gear-mesh tones, and mid-frequency broadband noise. Sounds were presented in pairs and subjects reported degree of preference. The rank ordering of preference shows the perceived benefit of reducing low-frequency tones versus higher-frequency broadband noise. In the second study subjects were exposed for one 6-h period to a helicopter-type sound environment at 88 dBA and for one 6-h period of exposure to a control condition of minimal noise exposure. During each of these test-exposure days, the subjects were required to complete computer-based tests at specified intervals throughout the day, to monitor any change in fatigue or alertness levels. The most relevant conclusions from the tests will be presented in the paper.
Monaural phase effects in the discrimination of the spectral shape of transients
Authors: Wakefield Gregory H. , Heller Laurie M. , Carney Laurel H. , Mellody Maureen
Published: July 2002

Limits on temporal resolution in auditory perception range from 25 ms, for the judgment of temporal order, to a lower limit of 3–4 ms for the discrimination of monaural phase. Results are presented on the discrimination of spectral shape for signals concentrated within this lower bound. A wideband, 4-ms noise was compared with spectrally smoothed versions. The phase spectrum was controlled by assigning the same random phase spectrum to both the original and smoothed signals. Depending on the choice of phase spectrum, discrimination thresholds for spectral shape were found to vary from 2–3 dB to as much as 15–17 dB, at which point the smoothed spectrum is essentially flat. This dependence on phase can be eliminated by presenting a train of transients, rather than a single transient. Such findings do not appear to be accounted for by synthesis artifact, nor by any simple features of either the complex spectrum or waveform envelope of these wideband signals. Phase effects are observed, however, in a computational model of the auditory nerve. [Work supported by the following grants from ONR: 61153.04114.00, MURI Z883402, and US DOD N66604-96-C-H366.]
The vibration of uncertain structures: Random matrix theory and non-Poisson statistical models of the system’s natural frequencies
Authors: Langley Robin S.
Published: July 2002

At medium to high frequencies, the noise and vibration levels in an engineering structure can be sensitive to small changes in the properties of the system. This means that the response of a set of nominally identical units (for example, automobiles) from a production line can be radically different, and knowledge of the response statistics would significantly aid quality assurance and control. Unfortunately, the prediction of the noise and vibration response statistics for a complex built-up random structure is an extremely difficult task, as is the associated problem of determining the statistics of the natural frequencies and mode shapes. In recent years it has been suggested that progress might be made by employing the techniques of random matrix theory previously developed for applications in nuclear physics. In particular, the Gaussian Orthogonal Ensemble (GOE) has been shown to yield good agreement with the statistics of the natural frequencies of various metal blocks. In this paper the applicability or otherwise of random matrix theory to realistic engineering structures is considered, and a comparison is made with other approaches, such as a non-Poisson point process model of the natural frequencies. Several examples are considered to illustrate the theoretical developments.
Phoneme recognition before and after hearing aid fitting
Authors: Neel Amy T. , Rout Ayaskanta
Published: July 2002

Many listeners with sensorineural hearing loss experience only modest increases in speech recognition after receiving their hearing aids and very small increases in hearing aid benefit up to one year after hearing aid fitting. In this study, phoneme recognition patterns before and after hearing aid fitting were examined to determine which phonemes improved most with amplification and which phonemes continued to improve with hearing aid experience. Preliminary results using a nonsense syllable recognition test revealed that voiceless stops and fricatives improved the most immediately after hearing aid fitting although accuracy remained below 50% for these phonemes. Aided recognition for these phonemes, however, improved very little from one month to one year postfitting. Variability in phoneme recognition before and after hearing aid fitting across subjects was large. Phoneme recognition results from an ongoing study of first-time hearing aid users with comparable levels of signal processing will be presented. Differences in phoneme recognition before and after hearing aid fitting can help explain differences in hearing aid benefit across hearing aid users. In addition, phoneme recognition profiles can be used to design individualized, efficient auditory training programs for new hearing aid users.
Recognizing words from optical phonetic signals
Authors: Mattys Sven , Bernstein Lynne E. , Auer Edward T.
Published: July 2002

Lipreading is thought to be extremely difficult, and the difficulty is attributed to lack of perceptual distinctiveness among most visible spoken words. Therefore, it is thought that accurate lipreading requires reliance on postlexical processes, such as guessing. However, we [E. T. Auer and L. E. Bernstein, J. Acoust. Soc. Am. 102, 3704–3710 (1997)] predicted, based on computational modeling of the lexicon, that many words maintain their visual distinctiveness. In this study, we took only visual phoneme confusability and word frequency into account to predict the relative intelligibility of lipread words. We predicted that words without visual lexical competitors can be perceived as readily as heard words, and a systematic change in intelligibility would be observed as a function of word frequency and number of competitors. Predictions of near-100% accuracy for many words were confirmed in a perceptual word identification experiment with skilled deaf American lipreaders. Accuracy was not influenced by word length. When phoneme confusability in words was statistically controlled, the number of lexical competitors correlated significantly with word score, as did word frequency. These results will be compared with those of hearing participants, and the implications discussed with attention to bottom-up processes versus lexical competition in spoken word recognition. [Work supported by NIH/NIDCD 02107.]
Sources of variability for talker and listener effects in auditory–visual speech perception
Authors: Jin Su-Hyun , Carney Arlene E.
Published: July 2002

Carney et al. [J. Acoust. Soc. Am. 106, 2270 (1999)] reported on talker and listener effects for auditory–visual speech perception for syllabic stimuli that were disparate [a visual /gi/ paired with an auditory /bi/ or a visual /bi/ paired with an auditory /gi/]. Listeners varied in the ratios of fused and combination responses (the McGurk effect) to auditory responses, depending upon the talker and their own most frequently observed mode of perception. The purpose of this experiment was to determine if listener and talker variability could be manipulated by recombining talkers’ voices with different talkers’ faces. Green et al. [Percept. Psychophys. 50, 524–536] had demonstrated that the McGurk effect was observed even when voices and faces did not match in gender. The same 11 talkers (5 male and 6 female) were used from the Carney et al. experiment. Twenty-four listeners heard the combination of all male talkers with each other and all female talkers with each other. Similar patterns of listener and talker variability were observed even when voices and faces did not match, supporting the earlier conclusion that the McGurk effect is a graded phenomenon, depending upon listener and talker. [Work supported by NIDCD.]
Model-based and data-based processing of moving sources in a shallow water channel
Authors: Zurk Lisa M. , Ward James
Published: July 2002

Adaptive MFP algorithms are applied to passively detect and localize a moving source while mitigating interference from surface shipping. A model-based motion compensation algorithm is applied to prevent smearing loss from target motion and extend the observation interval for adaptation. Moving interference is removed by applying a time-varying spatial filter at each data snapshot. The time-variation of the filter decreases the size of the instantaneous interference subspace and allows for a larger signal subspace. The interference subspace is formed by one of three methods. In the first method, knowledge of the ship position is combined with a propagation model to predict the time-varying acoustic interference. A sector null is formed to protect against mismatch degradation. In the second method, a data decomposition is used to determine the strong interferers. The third method combines model-based and data-based approaches. For each method, interference rejection is quantified by presenting SINR values for the candidate algorithm and comparing to conventional approaches. The results use data obtained from the Santa Barbara Channel Experiment. [This work was sponsored by DARPA under Air Force Contract F19628-95-C00022E. Opinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the United States Air Force.]
A hybrid plane-wave beamforming/matched-field processing, track-before-detect technique for detection of broadband moving sources with horizontal line arrays
Authors: Baxley Paul A. , Brannan Randall
Published: July 2002

A hybrid plane-wave beamforming/matched-field processing (MFP), track-before-detect (TBD) technique for the automated detection and tracking of broadband moving sources in shallow water is presented. The approach, applicable to bottom-mounted horizontal line arrays (HLAs), provides estimates of the full track parameters (range, depth, course, and speed) with a processing load substantially lower than that required for a fully three-dimensional MFP search. The method begins with the production of a bearing-time record (BTR) for the HLA. By applying a TBD algorithm to the BTR, a detection is made and track bearing as a function of time is estimated with some bias and uncertainty. The MFP range-depth ambiguity surfaces are then produced for an envelope of bearings bracketing the bearing estimate uncertainty at each time. The TBD processing of these surfaces, involving a search over tracks defined by all combinations of bearings in the envelopes at the beginning and end of candidate tracks, allows for an estimation of the full track parameters as well as a reduction of bearing uncertainty and bias. Results of the application of this technique to broadband source-tow data in the Black Sea are presented. [Work supported by the ONR 321US.]
Broadband shallow-water sea-test results with a towed vertical aperture array
Authors: Ianniello John P. , Tattersall John M.
Published: July 2002

We review matched-field processing (MFP) sea test results obtained using a towed vertical aperture array. The array consisted of five horizontal lines towed in a vertical plane, nominally one over the other, with an approximately 5-m separation between the lines. We review results from two tests, one conducted in the Gulf of Mexico in about 120 m of water, and the other conducted southwest of Key West, FL in about 600 m of water. The vertical aperture array was towed on straight-line courses, at various ranges, parallel to a towed sound source. The radiated signal was a Gaussian pseudorandom waveform in the 100–600-Hz band. Results using replica correlation techniques are first used to study the channel transfer function; next, MFP results obtained by treating the signal as a random process are shown. These results demonstrate accurate range and depth localizations from 5 to 20 km as well as the ability to resolve a loud surface interferer from a quieter source at depth which is on the same bearing. These test results demonstrate the inherent robustness of broadband MFP. [Work supported by ONR 321.]
Model-based towed array processor: Experimental results
Authors: Sullivan Edmund J. , Brecht Dieter , Persson Leif
Published: July 2002

Results of a towed array bearing estimation experiment using a model-based processor are presented. The experiment took place in the southern Baltic using an Atlas towed array. The towship was the Swedish corvette Gavle. Results for the case of a 121-Hz source are presented. The towship ran in a straight line, past the source, where the distance of closest approach was 500 m. A short overview of the model-based approach, which is based on a state space formulation using a Kalman estimator, will be presented. By formulating the problem in state space form, it is possible to include sophisticated models in the processor. This, in effect, is a self-consistent means of including a priori information into the processing. It will be shown that the inclusion of the array’s forward motion provides significant improvement in performance over the conventional processor in terms of the variance of the estimate. The improvement in performance arises from the bearing information contained in the forward motion of the array. This information obtains, from the time scale, change in the signal or, in the narrrow-band case, the Doppler. The experimental results clearly show the improvement over the conventional processor.
Array measurements and characterizations with sources in motion
Authors: Carey William M.
Published: July 2002

Traditional processing has treated space and time as independent random variables with assumed ergodicity; however, dynamic-noise fields are produced by moving sources. In these cases, can velocity and range information be used to increase gain, cancel noise, and improve resolution? High-resolution arrays have measured the dynamic ambient noise fields at low frequencies, over long time intervals and at basin/margin spatial scales, and have resolved/tracked shipping. This paper summarizes experiments with arrays which used source-relative velocity as a processing variable, that is, space–time processing. Results from a closed-basin shipping dominated noise field showed the relative velocity acted as a filter that improved the signal-to-noise ratio for sources with known relative velocity and reduced it for sources having different relative velocities. Results from a shallow water experiment with a vertical array, moving source, and the Bessel transform were shown to determine the wave number spectrum and were comparable to the modeled spectrum in both amplitude and phase. Thus the contention that improved array ship-noise measurement and cancellation is possible if the velocity is known may have merit, especially if modal variations can be adaptively modeled.
Measurements of the subjective acoustical parameters on an orchestra platform
Authors: Jeon Jin Yong
Published: July 2002

This paper deals with the relationship between the subjective room-acoustical parameters and the objective properties of the sound field on an orchestra platform. A set of acoustical parameters is investigated and subjective preference tests are conducted both on a real platform and a simulated platform of a concert hall. Parameters EDT, RT, C80, D, Ts, 1-IACC (or LEF) are used for assessments of the quality of the stage acoustics. Advantages and limitations of computer simulations versus field experiments are discussed and both experiments are reviewed, in which the EDT/RT and spatial impressions are investigated. From the subjective preference tests, it is found that musicians form their stage acoustic judgments based on their perception of reverberance, clarity, envelopment, loudness, warmth, brilliance, and overall impression. In addition, the relative reverberance EDT/RT is revealed to have high correlation with the subject-averaged judgments and the spatial impression indices.
The time-domain behavior of coupled resonator scatterers
Authors: Feuillade C.
Published: July 2002

In previous work [J. Acoust. Soc. Am. 98, 1178–1190 (1995)] a coupled oscillator formalism was introduced for describing collective resonances, scattering, and superresonances of multiple air bubbles in a fluid. Subsequent time-domain investigations, of the impulse response of coupled systems, have disclosed the conditions which exactly determine whether the ensemble behavior is properly described using: (a) a multiple scattering paradigm or (b) a collective modal methodology. The important criteria are the Q of the individual scatterers, and their typical separations in the medium. For highly damped or sparse systems, e.g., scattering from loose schools of swimbladder fish, or from a gassy seabed containing entrained bubbles, the scatter counting approach may be applicable. For more strongly coupled systems, e.g., a dense cloud of resonating bubbles in the water column, the individual scattering events are typically not resolvable and a modal approach must be used. The result has implications for both volume and bottom-scattering applications. Theoretical and numerical analysis will be presented. [Work supported by ONR.]
Simultaneous measurements of the bubble size distributions and radiated noise from open-ocean whitecaps
Authors: Deane Grant , Stokes Dale
Published: July 2002

It is now widely acknowledged that wind-induced oceanic ambient noise comes from ringing bubbles formed by breaking waves at the ocean’s surface. The numbers, sizes, creation rates, and spatial distribution of these bubbles are all important in determining the acoustic radiation signature of a breaking wave. Results from an experiment to measure the bubble size distribution within open-ocean whitecaps and simultaneously record the burst of sound radiated by forming whitecaps will be presented. The bubble size distribution measurements were made with an optical instrument mounted within 0.5 m of the ocean’s surface beneath a surface-following frame. The instrument is capable of resolving the time-evolving bubble size distribution on millisecond time scales and centimeter length scales within a whitecap. The simultaneous optical and acoustical measurements are important for modeling the sound of breaking waves in the open ocean and the surf zone. [Work supported by ONR and NSF.]
Detection of land mines in fluid-saturated unconsolidated soil: Numerical modeling
Authors: Zeng Yanqing , Liu Qinghuo
Published: July 2002

Because of the strong interactions of waves with the solid grains and the fluid in the pore space, it is more appropriate to model the soil as a fluid-saturated unconsolidated material than a single-phase elastic medium. A three-dimensional finite-difference method for modeling acoustic waves propagating in fluid-saturated unconsolidated soil has been developed. Instead of the conventional elastic wave equations, Biot’s equations are used for the poroelastic model. Based on the strain–stress relationship, Biot’s equations are reformulated into a first-order hyperbolic system which is equivalent to strain-velocity formulation. A perfectly matched layer (PML) is used to absorb outgoing waves at the truncated boundary of an unbounded medium. The numerical method is validated by comparing numerical results to an analytical solution. Models of a land mine buried in fluid-saturated unconsolidated soil are developed. The numerical method is used to study the interaction of acoustic waves with the buried mines. Comparison of these results is made with those for a buried land mine in a conventional single-phase elastic soil model.
Acoustically induced slow dynamics in nonlinear mesoscopic elastic materials
Authors: Sutin Alexander M. , Johnson Paul A. , TenCate James A.
Published: July 2002

We have known about slow dynamics in rock due to continuous wave excitation drive for several years (http://www.ees4.lanl.gov/nonlinear). TenCate, Smith, and Guyer (see abstract, this meeting) have recently discovered that both the elastic modulus and the wave dissipation display log time recovery in granular solids, and that it may be thermally or mechanically induced. Much to our surprise, we have discovered that a CW or broad-frequency band acoustic source can also induce slow dynamical response. This response was observed as a variation of the ultrasonic probe wave amplitude, the resonance frequency, and Q factor after the action of a pump wave. The slow time recovery took place in materials such as powdered metals, damaged materials, concrete, and rocks as well. The variations of material properties due to the action of pump waves lead to transient amplification and an obscuration of CW probe waves. The observed behavior may be more universal than was first thought. The results have potential implications to many topics, including laboratory wave studies, earthquake strong ground motion, elastic waves emanating from a point source, damage detection, and manufacturing processes. [Work supported by Stevens and by the Department of Energy: Office of Basic Energy Sciences.]
Using Markov models to assess articulation errors in young children
Authors: Bunnell H. Timothy , Yarrington Debra M. , Polikoff James B.
Published: July 2002

Digital recordings of children producing the names ‘‘Rhonda’’ and ‘‘Wanda,’’ and/or ‘‘Toto’’ and ‘‘Coco’’ were made using the microphone input to a Toshiba laptop computer (16-bit samples, 22050-kHz sampling rate) with an AKG C410/B head-mounted condenser microphone. These names were associated with animated characters in a mock video game running on the laptop under the control of a Speech Language Pathologist. The children, ranging in age from four to six years, were undergoing speech therapy at the Alfred I. duPont Hospital for Children for one or both of two common articulation errors: /w/ substituted for /r/; and/or /t/ substituted for /k/. The initial segment in each recorded utterance was classified by laboratory staff as either r/w or t/k, and assigned a goodness rating. Discrete Hidden Markov phoneme Models (DHMMs) trained using data recorded from normally articulating children were then used to classify the same utterances and results of the automatic classification were compared to the human classification. Results indicate that appropriately trained DHMMs can provide accurate classification of utterances from children in speech therapy. This technology could support articulation drill on home computer systems as an adjunct to speech therapy. [Work supported by Nemours Research Programs.]
Compensatory articulatory behavior to immediate structural perturbation of the oral cavity
Authors: Honda Masaaki , Kaburagi Tokihiko , Fujino Akinori
Published: July 2002

Speech compensation to the structural perturbation of the oral cavity was investigated by using an artificial palate whose thickness in the alveolar region is dynamically changeable. The artificial palate was constructed with a base and thin rubber attached to the base, and the rubber balloon was dynamically controlled by means of an external air flow. The articulatory behavior with the structural perturbation was recorded using an electromagnetic articulographic system. A set of VCV syllables uttered in the carrier sentence, containing the consonants /s, sh, t, n/ and the vowels /a, i, u/, was used for the test. Unexpected perturbation of the palate shape, a change in thickness of 1 to 4 mm, caused significant speech articulation errors for the fricative consonants, fictive consonants /s, sh/ changed to the stop consonants /t, ch/. On the contrary, the stop consonant /t/ was very robust to unexpected perturbation. After five to seven speaking trials with the modified palate shape with or without audio feedback, these articulation errors disappeared and the subject could produce correctly perceived consonants. Then, the articulatory compensation in the alveolar region significantly appeared in the tongue tip position but was small in the jaw and the lip positions.
Demonstrating effects of parameter dynamics on gestural timing
Authors: Saltzman Elliot , Byrd Dani
Published: July 2002

Speech movements have been modeled as goal-directed gestures whose activation-gated dynamics are those of critically damped point attractors. Recent work by ourselves and others has suggested that gestural parameter values are not fixed but rather vary as a function of a gesture’s position in the word and phrase. For example, lowering of gestural stiffness values has been hypothesized to underlie gestural lengthening adjacent to phrasal boundaries. Additionally, evidence exists suggesting that prosodic structure affects the relative timing between gestures. In earlier work, we have hypothesized that slowing at phrase boundaries can be implemented using nonconstriction gestures called pi-gestures (prosodic gestures) that act on the parameter values of all concurrently active constriction gestures in proportion to the activation level of the pi-gesture. In order to understand the potentially complex consequences of these parameter dynamics, we present a series of simulations involving different temporal arrangements of two constriction gestures coordinated with one another and with a prosodic gesture. The within- and between-gesture temporal patterning of the constriction gestures will be evaluated under the influence of pi-gestures of greater and lesser strength (activation) and duration. Simulation results will inform interpretation of natural kinematic articulatory data collected in movement tracking experiments. [Work supported by NIH.]
Effects of central dopaminergic stimulation by apomorphine on producing sentence focus in speech production in Parkinson’s disease—a preliminary report
Authors: Wang Q. Emily , Xu Yi , Kompoliti Katie , Goetz Christopher G.
Published: July 2002

It is well documented that when a sentence focus is produced, the f0-range of the word under focus is expanded while the f0-range of the post-focus words is suppressed. It is also a well-known fact that individuals with Parkinson’s disease (PD) exhibit reduced ability in pitch modulation, resulting in a perceptual quality of ‘‘monopitch’’ in connected speech. Although the use of dopaminergic stimulation improves other physical symptoms such as balance and walking in PD, it is unclear whether a similar effect will be found on vocal folds, producing an improvement in patients’ ability in pitch modulation. In this study, five nondemented English-speaking individuals with a clinical diagnosis of idiopathic PD (Hoehn and Yahr stage 3 and 4, off) were examined for their ability in pitch modulation in association with Apomorphine, a nonergot dopamine agonist. Two six-word sentences with four sentence focus variations each were used. Subjects randomly produced three repetitions of each focused version at baseline and two clinical conditions: injected with placebo or apomorphine. Perception tests and acoustic analyses were conducted to determine changes in these patients’ ability to produce sentence focus. Implications of the findings are discussed in terms of speech motor control.