bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the performance of a model-based optimal auditory processor on a simultaneous masking task
Authors: Gresham Lisa C. , Collins Leslie M.
Published: July 2002

Psychoacoustic experiments indicate that the human auditory system is less sensitive than predicted by classical signal detection theory on a simultaneous masking task [C. M. Reed et al., J. Acoust. Soc. Am. 53, 1039–1044 (1973)]. Traditionally, the difference between the matched filter and the experimental performance has been compensated for by assuming an additional internal additive noise. However, this noise has not been completely explained in physiological terms. The inconsistency may also partially be the result of the suboptimal application of signal detection theory. To investigate this discrepancy, signal detection theory is integrated with Patterson’s model of the human auditory system [R. D. Patterson et al., J. Acoust. Soc. Am. 98, 1890–1895 (1995)]. The performance of the optimal detector for a simultaneous masking task is compared to experimental data, allowing the theoretical performance bounds to be determined and the model to be verified. The results of this work suggest that with a more appropriate application of signal detection theory it is possible to partially explain the difference in performance between the matched filter and experimental data as the result of physical processes inherent in the auditory system. Utilizing a priori information regarding these processes results in an approach which more accurately predicts psychophysical behavior.
Effects of masker uncertainty on masking by familiar sounds
Authors: Oh Eunmi , Lutfi Robert A.
Published: July 2002

Detection thresholds for a tone in an unfamiliar tonal pattern are greatly elevated under conditions of masker uncertainty [D. L. Neff and D. M. Green, Percept. Psychophys. 41, 409–415 (1987)]. The present experiment was undertaken to determine whether a similar result is obtained when the masker is a familiar sound. Fifty common environmental sounds served as familiar maskers (e.g., dog bark, door slam, phone ring, etc.). Fifty Gaussian noise samples served as unfamiliar maskers. The magnitude and phase spectra of each masker were analyzed into 906 spectral components. Masker uncertainty was introduced by using fewer than 906 components to synthesize each sound, and by selecting the frequencies of these components at random on each presentation. Masked thresholds for a 1.0-kHz signal were obtained using an adaptive, two-interval, forced-choice procedure. Results with noise replicate earlier results showing largest elevations in threshold for 10–20 spectral components. Results with familiar sounds showed a similar pattern but with even larger elevations in threshold. Trial-by-trial analyses showed a small detection advantage for sounds rated as highly familiar by listeners. Overall the results fail to provide strong evidence that listeners use stimulus familiarity to overcome the effects of masker uncertainty. [Research supported by NIDCD.]
Broadband mine detection and classification—Target responses from a set of 2- to 20-kHz shallow-water experiments
Authors: Kaczkowski Peter J. , Eggen Christian J. , Luby James C.
Published: July 2002

The problem of discriminating between underwater mines and similarly sized false targets at ranges of several hundred meters remains a challenge. The Applied Physics Laboratory, University of Washington, in conjunction with Arete Engineering and Technologies Corporation, San Diego, have been developing detection and classification signal processing schemes using data collected in several shallow-water experiments with a broadband (2–20 kHz) sonar. The use of relatively low frequencies for mine hunting permits greater penetration into bottom sediments for improved detection of buried or partially buried mines. Wide bandwidth signals mitigate the lack of spatial resolution expected from a narrow-band analysis at such frequencies, and provide a wealth of information for classification. A brief description of the sonar and of the experiments conducted in Puget Sound using mines and minelike false targets will be given. Target responses as a function of time, frequency, and aspect angle will be presented, as will results of using several feature extraction methods to reduce the dimensionality of the data.
Measurements of differential scattering cross section using a ring transducer
Authors: Mast T. Douglas , Jansson Tomas T. , Waag Robert C.
Published: July 2002

A method for the measurement of intrinsic scattering object properties is presented. This procedure is based on the measurement of the scattered acoustic field as a function of scattering angle and frequency. Measurements are normalized using analytically determined expressions for emitter and detector beams resulting from a combination of unfocused linear elements arranged in a circular configuration. The spatial effects of finite emitter pulse length and detector gate length are represented by a convolution formula valid for narrow-band signals and long receiver gates. The method includes correction for target absorption as well as measurement of the directly transmitted acoustic power in the free field, yielding the average differential scattering cross section per unit volume. Measured results for two phantoms consisting of glass microspheres embedded in agar show good relative agreement with theory for varying angle, frequency, and phantom properties. For the phantoms employed, scattering effects, rather than increased absorption, are shown to account for most of the difference in transmission loss between pure agar and agar with glass spheres.
Efficient SAS image-reconstruction algorithms
Authors: Hawkins David , Gough Peter
Published: July 2002

Now that several prototype strip-map synthetic aperture sonar (SAS) systems are in operation and producing images (albeit on an irregular basis), much of the focus of current research is on the efficiency of the various strip-map image reconstruction algorithms. Although sometimes still used by several sonar groups, the old ‘‘delay-and-sum’’ beamforming, or exact algorithm, is clearly inadequate for high throughput imaging. Newer algorithms such as the range/Doppler, wave number, and chirp-scaling algorithms are considered. Using a simulated target field of point reflectors, the results from all of these algorithms are compared and the relative computational loads given. As well, the more recently developed (em accelerated) chirp-scaling algorithm is explained.
Space-time signal processing for complicatedly moving antennas
Authors: Gorban Igor I.
Published: July 2002

The results of the author’s last work in the field of space-time signal processing (STSP) were presented at the 132nd Meeting of the Acoustical Society of America [I. I. Gorban, ‘‘Space-time signal processing algorithms for moving antennae,’’ J. Acoust. Soc. Am. 100, 2638(A) (1996)]. It touched the two problems of STSP in complicated dynamic conditions, where there was antenna motion with variable velocity and angle rotations, and modifying of the form of the antenna. The first problem is STSP optimization in conjunction with the complicated antenna motion, the noises, and the medium together. The second is the problem of super-multichannel STSP with low calculating efforts. New approaches were proposed for solving these problems. It was found that complicated antenna motion, often regarded as a destabilizing factor, may play a greatly positive role for increasing space-time selectivity and noise immunity of the systems. Rather than struggle with this destabilized factor it was proposed that one should use it. Ways to essentially reduce calculations for complicated STSP in dynamic conditions were also found. At the 133rd Meeting, the new results of the research developing the proposed approaches, for towed arrays in particular, will be presented.
A survey of research on low-frequency acoustic communication in elephants
Authors: Payne Katharine
Published: July 2002

Research projects by K. Payne, W. Langbauer, E. Thomas, and J. Poole have shown that Asian and African elephants make powerful infrasonic calls, some of which are used in long-distance communication. Although full classification has not been achieved, some of these calls are social, others reproductive; behavioral responses show individual recognition. Playback experiments yielded a measure of the distances over which conspecifics respond during daylight hours (Langbauer et al.) and of the social information imbedded in certain clearly definable calls (K. McCoun). Long-distance communication appears to be implicated in the coordinated movements between separated elephant families; a field study using radio collars with implanted voice-activated microphones yielded suggestive results (Langbauer et al.). A meteorological study by meteorologists M. Garstang and D. Larom led them to predict large-scale diurnal fluctuations in low-frequency sound propagation in dry season savannas. They and Payne plan to collaborate in research on the relation between these phenomena and calling behaviors of savanna animals. [Support for the presenter’s projects came from World Wildlife, National Geographic, NSF, and a Guggenheim fellowship.]
Comparisons between tone-in-noise and phase sensitivity tasks
Authors: Branstetter Brian , Berg Bruce G. , Southworth Curt , Khuu Lisa
Published: July 2002

According to critical band theory, phase sensitivity as a function of stimulus bandwidth and detection thresholds for a tone masked by noise are both indicators of the frequency resolution of peripheral auditory filters. The relation between these two measures is examined. For the phase sensitivity task, stimuli consist of three tones with constant intensity and randomly sampled phases. Two identical sounds are played on each trial together with a third having different randomly sampled phases. Listeners identify the odd sound. The frequency separation between tones is varied according to an adaptive staircase procedure which yields an estimate of the bandwidth at which the odd sound is identified with 71% accuracy. Estimates are obtained for center frequencies of 500, 1000, 2000, and 4000 Hz. For the second task, thresholds for 500, 1000, 2000, and 4000 Hz tones masked by broadband Gaussian noise are estimated. Results show that performance levels for different conditions within each task are highly correlated, whereas across-task correlations are either zero or slightly negative. These finding demonstrate that predictions from critical band theory do not generalize to the level of individual listeners. [Work supported by ONR.]
Psychophysical suppression as a function of signal frequency
Authors: Lee Jungmee , Bacon Sid P.
Published: July 2002

Psychophysical suppression was investigated across signal frequency (250, 500, 1000, 2000, and 4000 Hz) in a forward-masking paradigm. Masker duration was 200 ms, signal duration was 20 or 40 ms, and signal delay was 0 or 20 ms. When using a noise masker (spectrum level of 40 dB), the amount of suppression was determined by subtracting threshold in the presence of a broadband masker from that in the presence of a critical band masker. When using a tonal masker (masker level of 50 dB SPL, suppressor level of 70 dB SPL, with the suppressor frequency being 1.2 times the masker/signal frequency), the amount of suppression was determined by subtracting the threshold in the presence of the masker plus suppressor from that in the presence of masker alone. For both masker types, the amount of suppression increased as signal frequency increased up to 1000 Hz, but then reached an asymptote or decreased somewhat as signal frequency increased to 4000 Hz. [Work supported by NIDCD.]
Cluster-based probability model for musical instrument identification
Authors: Brown Judith C.
Published: July 2002

Mel based cepstral coefficients have been calculated for 30 short (1–2 s) segments of oboe sounds and 30 short saxophone sounds. These were used as features in a pattern analysis to determine for each of these sounds comprising the test set whether it belongs to the oboe or to the sax class. The training set consisted of longer sound segments of 1 min or more for each of the instruments. A k means algorithm was used to calculate clusters for the training data, and Gaussian probability density functions were formed from the mean and variance of each of the clusters. Each member of the test set was then analyzed to determine the probability that it belonged to each of the two classes, and a Bayes decision rule was invoked to assign it to one of the classes. Initial results classifying the oboe sounds have been very good, but are less impressive for the saxophone set. Results of a human perception experiment identifying these same sound segments will be reported.
The effect of temporal fringes on the fundamental-frequency discrimination of resolved and unresolved harmonic complexes
Authors: Micheyl Christophe , Carlyon Robert P.
Published: July 2002

Three experiments investigated the finding that F0 discrimination for a harmonic complex can be impaired by temporal fringes [R. P. Carlyon, J. Acoust. Soc. Am. 99, 525–533 (1996)]. The 100-ms target and the 200-ms forward and backward fringes were filtered (1375–1875 Hz) and presented in a pink noise background. Two F0’s were used: 88 Hz, where the harmonics were unresolved by the peripheral auditory system, and 250 Hz, where the harmonics were unresolved. The fringe produced a larger deterioration when it had a similar F0 to the target than when the F0’s differed. Experiment 2 showed that adding off-frequency components to the fringe did not affect this pattern of results, thereby ruling out interpretations based on spectral confusion between the target and the fringe. Experiment 3 further examined the dependence of the deterioration on the similarity between target and fringe F0’s. It showed that FDLs for an 88-Hz target were not reduced when the components of an 88-Hz fringe were set to alternating phase, thereby doubling their pitch without affecting resolvability of the components. The implications for single- and dual-mechanism models of pitch will be discussed.
Puzzles of loudness constancy, loudness adaptation, and speech frequencies
Authors: Weiler Ernest M. , Sandman David E. , Dou Hongwei
Published: July 2002

Loudness constancy is suggested as a term for the failure to observe simple adaptation above 30 dB, noting however that Miskiewicz et al. [J. Acoust. Soc. Am. 94, 1281–1286 (1993)] indicated that simple adaptation is found at higher intensities above 4 kHz. Conversely, using the ipsilateral comparison paradigm (ICP), Dange et al. [J. Gen. Psychol. 120, 217–243 (1993)] found adaptation at 1000 Hz, from 45 to 75 dB. They saw this as revealing underlying neural adaptation, normally concealed by processes of loudness constancy. As a further test, Hellman [personal communication (1996)] urged that ICP adaptation be attempted without the usual designated modulus. In the present study (N=20), strong ICP loudness adaptation was indeed found with and without the designated modulus. Recently, Janson et al. [Br. J. Audiol. 29, 288–297 (1996)] found that ICP adaptation at 1 kHz was much less consistent for subjects with higher frequency loss than for nonimpaired listeners. Discussion of the possible value of loudness constancy in the speech frequencies will be discussed in light of current data and previous studies.
The interaction of lexical competition and semantic context in spoken word recognition by younger and older adults
Authors: Sommers Mitchell S. , Danielson Stephanie M.
Published: July 2002

The present study examined the interaction of two operations, discrimination of lexical candidates and use of semantic context, that are central to the early stages of spoken word recognition. In addition, the investigation was designed to evaluate age differences in the interaction of these two processes. Identification scores were obtained for lexically hard (items phonetically similar to many high-frequency words) and easy (items phonetically similar to only a few low-frequency words) stimuli in three contexts: single words, low-predictability (LP) sentences, and high-predictability (HP) sentences. Although significant differences between easy and hard words were observed in all three contexts, the effects of lexical difficulty were attenuated in the HP, relative to the SW and LP conditions. The principal finding with respect to age was that older adults exhibited greater benefits of contextual information for hard, but not for easy words. The findings are discussed in terms of their implications for the interactive nature of spoken word recognition and for understanding age-related declines in speech processing. [This research was supported by the Brookdale Foundation.]
Hearing-impaired perceivers’ encoding and retrieval speeds for auditory, visual, and audiovisual spoken words
Authors: Seitz Philip F.
Published: July 2002

Perceptual encoding and memory retrieval processing speeds were assessed for spoken words in 26 subjects, mean age 66, with mild to moderate acquired sensorineural hearing loss. Subjects were trained to achieve error-free recognition of a set of ten spoken words in auditory, visual (speech reading), and audiovisual conditions. They then performed the Sternberg item recognition task in each of the modality conditions using the same set of ten words. The task involved presenting memory sets of one to four words, followed by a probe word to which subjects made a speeded ‘‘YES’’ or ‘‘NO’’ button response to indicate whether the probe matched any of the memory set items. Least-squares linear models provided good fits to subjects’ memory-set size by reaction time functions (mean r2>0.90 for all three conditions). Using the models’ intercepts and slopes to represent encoding and retrieval times, respectively, Wilcoxon tests showed significant differences among the conditions with respect to both encoding and retrieval speed, with audiovisual fastest and visual slowest. These results are interpreted as evidence for: (1) audiovisual ‘‘benefit’’ to processing speed in hearing-impaired speech perception; (2) relativeinefficiency of encoding visual speech; and (3) representation differences associated with the modalities. [Work supported by NIH-NIDCD.]
Performance limits on underwater acoustic matched-field processing
Authors: Tabrikian Joseph , Krolik Jeffrey L.
Published: July 2002

Sensor array processing methods which use full-wave models of complex multipath propagation to facilitate estimation of underwater source locations and channel parameters are known to be prone to ambiguities and environmental variability. Particularly at low signal-to-noise ratios, the performance of matched-field methods may therefore deviate radically from the Cramer–Rao bound which assumes estimation errors are small. To study matched-field processing in the presence of anomalies, this paper considers the Barankin bound. The Barankin bound is particularly useful for determining the threshold signal-to-noise ratio below which any unbiased estimate of the source location or environmental parameters will be prone to large errors. In this paper, the Barankin bound is compared with a maximum likelihood (ML) estimator of source location in an uncertain shallow-water scenario. The results indicate that the Barankin bound predicts the threshold signal-to-diffuse-noise ratio of the ML method to within 3 dB. Further, in the presence of surface shipping, the impact of both vertical and horizontal spatial decorrelation of the interference on matched-field performance is studied for different array geometries. [Work supported by ONR.]
A normal decomposition technique for fully coupled problems in structural acoustics
Authors: Basu Debashis , Kumar S. Suresh
Published: July 2002

Problems in structural acoustics are inherently coupled. Whenever a structure vibrates, there is a noise associated to it. Similarly, any noise would induce vibrations in the structure, however small, depending on how thin it is. The indirect boundary element technique has been used for quite some time now to model the acoustic domain. Again, plate/shell formulations for thin structures using finite elements are well known. Usually, for a coupled structural acoustic problem, the associated eigenvalue problem of the structure is solved first, and then the acoustic system is coupled using a predetermined number of modal participation. For weak coupling, this technique gives accurate results considering a few modes, while a greater number of modes are necessary for problems with strong coupling. An alternate technique is presented in this paper, where the structural degrees of freedom are condensed to couple directly with the acoustic system. For the frequency under consideration, there are absolutely no assumptions involved and the coupling is exact. Several examples illustrate the validity of the method. For problems where the level of coupling (weak or strong) and the number of modes to be included are difficult to ascertain, the current technique provides an excellent alternative. With noise control playing a major role in developed and developing countries, a better simulation of the field problem clearly identifies areas for noise reduction measures.
Energy balance for radiated waves and propagating vibration in a fluid-loaded beam under point excitation
Authors: Kovinskaya Svetlana I.
Published: July 2002

Using a compensating solution method [S. Kovinskaya and I. Krasnov, Acta Acust. 82, 237 (1996)] a field of flexural waves propagating along a submerged beam under a point excitation and a radiated acoustical field are represented analytically. The method is based on the Fourier integral transform of the vibration equation and is similar to the hybrid method [J. M. Cuschieri and D. Feit, J. Acoust. Soc. Am. 95, 1998–2005 (1994)]. The main and compensating solutions are determined as a result of the inverse Fourier transform along a real wave number axis of nonuniform and uniform equations, correspondingly. A sum of the main and compensating solutions must supply the vibration radiation condition. Let the last equation determine an indefinite coefficient in the compensating solution. The energy balance equation based on the solution of the problem leads to an energetic equivalence between a decreasing vibration and radiated spherical wave and the same between a cylindrical acoustical wave and an energy difference in the excitation point and infinity for propagating flexural wave.
The effect of task manipulation on the temporal ordering of articulatory events
Authors: Shaiman Susan
Published: July 2002

This investigation examined the sequencing of lip and jaw movement onsets and peak velocities for bilabial closure as a function of speaking rate, phonetic context, and position of the closing gesture within the utterance. Articulatory movements were transduced using head-mounted strain gauge transducers. Five normal speakers repeated the target words /paep/, /paeps/, and /paepst/, within the carrier phrase, ‘‘Now say ———— again.’’ Speaking rate (normal, fast, and slow) was manipulated using a magnitude production scale with no external time constraints. Most subjects demonstrated consistency in the sequencing of articulatory events at fast speaking rates, while normal and slow rates evidenced increasing variability. The position of the closing gesture within the utterance also affected the sequencing, with the closing gesture for the first /p/ usually exhibiting greater consistency than the closing gesture for the second /p/. The production of a single consonant versus consonant clusters appeared to have little impact on the sequencing of articulatory events for bilabial closure. Despite these general trends, individual subject differences were evident, with some speakers demonstrating greater consistency than others. These findings suggest that temporal ordering of articulatory events is flexibly organized based on the specific task demands. [Work supported in part by NSERC.]
Finite-element and experimental study of ultrasonic beam pattern characterization
Authors: Draheim Mark , Cao Wenwu
Published: July 2002

In this paper a study on the characterization of the acoustic beam pattern for two PZT-5H, 3.5-MHz transducers using both experimental and FEA methods is reported. To obtain actual pressure-field measurements, a three-axis positioning system was constructed. The transducers were submerged in an acoustic test tank and the positioning system was used to maneuver a 200-micron PVDF hydrophone within the pressure field. At each location the output voltage of the hydrophone was measured along with the corresponding location. Using SPYGLASS■, these data were plotted to yield a two-dimensional ‘‘slice’’ of the actual pressure field. A finite-element model of the water-loaded ultrasonic transducer was created using ANSYS■. Material properties that were needed to model the piezoceramic and polymers properly in the transducer were measured via pulse–echo technique. To validate the FEM results the electrical impedance of the transducers was calculated and compared to the actual measured values. The frequency-dependence of the impedance curves match closely. Using harmonic analysis, the pressure field in the water generated by the transducer was calculated and compared to the measured pressure-field data. Excellent agreement was obtained.
Universal equivalent circuit for transducers driven by a plate-shaped actuator
Authors: Piquette Jean C.
Published: July 2002

In recent years interest in the use of electrostrictive materials in transducers has increased greatly, in view of the development of materials such as lead magnesium niobate (PMN) and lead magnesium niobate/lead titanate (PMN/PT). These materials produce approximately an order of magnitude greater strain than that produced by piezoelectric materials when subjected to a comparable electric field level. Unfortunately, the behavior of these materials cannot be linearized by the usual procedure, since they will not retain a significant remanent pole for more than a short time. Hence, it is necessary to develop methods for predicting transducer performance based directly on the electrostrictive properties of these materials. This paper presents an equivalent circuit useful for predicting the first-order behavior of a transducer incorporating an electrostrictive mamterial in the form of a plate-shaped actuator. The methods used are sufficiently general that the resulting circuit is also applicable to piezoelectric and electrostatic transducers. Thus, in this sense, the equivalent circuit presented is ‘‘universal,’’ since it is equally applicable to electrostrictive, piezoelectric, and electrostatic transducers which utilize a plate-shaped actuator.
Modeling perforates
Authors: Dickey N. S. , Selamet A.
Published: July 2002

A number of computational and analytical tools are available to model perforated elements by treating the perforate interface as a distribution of localized reacting sources. Since the unsteady flow through an orifice exhibits a wide range of behavior, the results of such analyses depend strongly on the perforate model. Frequency-domain techniques are the most common approach for perforated element analysis and, correspondingly, nearly all available experimental data are presented in terms of frequency-domain parameters. Nonlinear behavior is generally addressed through a nonlinear orifice impedance, defined at a single frequency. While the frequency-domain approach is clearly justified for linear physics, or for nonlinear cases with a single driving frequency (the frequency is a natural scaling parameter), the use of this technique for nonlinear behavior caused by multifrequency disturbances may become questionable. The present study investigates unsteady flow through a circular orifice from a time-domain perspective. Development of an empirical perforate model based on relationships obtained from time-domain experimental data is discussed. The orifice model is incorporated into a time-domain computational scheme for perforated tube silencers and numerical predictions are compared to experimental data. The relative benefits and limitations of the present approach are addressed.
Surface stress waves when the elastic constants are functions of depth
Authors: Hazony Dov
Published: July 2002

Of concern are distortionless surface stress waves propagating in a medium which may be nonuniform relative to depth. A similar problem was posed by Burke et al. [Q. Appl. Math. 183–194 (1976)] where a unidimensional electrical ladder network model, nonuniform along the principle axis, was used in the investigation. Presently, a two-dimensional development is given based on Hooke’s law and Newton’s law leading to the well-known Rayleigh-waves formulation in a uniform medium. It will be seen that broadband high-pass propagation modes exist along the principle surface. As these propagate along the surface, they are accompanied by a phase change, linear with distance, in the frequency domain, and an associated symmetry change, periodic with distance, in the time domain. Applications may be found in high-frequency acousto-optics, in situ ultrasonic monitoring of elongated bodies, high-frequency SAW filters, and whenever surface acoustic waves are employed in an environment of high precision or relatively large distances. [Work supported by ONR.]
A numerical solution of acoustic scattering by an aircraft wake vortex
Authors: Shieh Chingwei M. , Morris Philip J.
Published: July 2002

Monostatic and bistatic acoustic scattering has been used in studies of the characteristics and motions of the atmosphere. This technique has been successfully implemented in the Monostatic Acoustic Vortex Sensing System (MAVSS) for the measurement of the characteristics of aircraft wake vortices during landing and take-off. In the present study, calculations are performed to simulate the MAVSS. The results of this study are giving information about the acoustic scattering by the vortex, as well as providing a controlled test bed for the instrument’s operation. Since the Doppler shifts, characteristic of the vortex velocity, are dependent on the incoherent scattering of the acoustic waves by turbulence advected by the vortex, a statistical model is proposed that describes the turbulence imbedded in the vortex. The simulations are performed using high-order accuracy finite-difference algorithms that have been developed for computational aero-acoustic (CAA) and wave propagation problems.
A resistance probe based on the lumped parameter model for the acoustic power output of a vibrating structure
Authors: Fahnline John B. , Koopmann Gary H. , Chen Weicheng
Published: July 2002

Previous papers by the authors addressed the analytical derivation and the numerical implementation of a lumped parameter model for the acoustic power output of a vibrating structure. Here the experimental measurement of the resistance is addressed. The acoustic resistance, which is related to the Green’s function of the second kind, can be determined experimentally by: (1) constructing an acoustically hard physical model of the boundary surface; (2) representing the discrete simple source with a small loudspeaker; and (3) measuring the acoustic field at a receiver location with a small microphone. The design of an acoustic resistance probe is described, along with an analysis of both the calibration procedure and the subsequent calculation of the resistance matrix. The analysis is validated through several example problems, with the accuracy of the measured acoustic resistance assessed by direct comparison to analytical or numerical solutions. For most of the cases considered, the experimental measurements and numerical predictions agree very well, but for some of the example problems discrepancies occur due to the limited dynamic range of the probe and acoustic excitation of structural vibrations.
Energy-conserving spectral solutions
Authors: Collins Michael D. , Schmidt Henrik , Siegmann William L.
Published: July 2002

Energy conservation is an important issue in range-dependent propagation modeling. Energy-conserving coupled mode and parabolic equation solutions have been developed [J. Acoust. Soc. Am. 89, 1058–1075 (1991)]. This presentation will describe an energy-conserving solution based on the wave-number spectrum. Range dependence is handled by dividing the medium into a sequence of range-independent regions and enforcing the complete energy-conservation condition [J. Acoust. Soc. Am. 94, 975–982 (1993)] at the vertical interfaces between regions. This condition involves the square root of the horizontal wave number in the forcing function of the spectral equation and in the spectral integral. This approach has been implemented and tested for both fluid and elastic media. [Work supported by ONR.]
Parabolic equation models for anisotropic sediments
Authors: Fredricks Andrew J. , Siegmann William L. , Collins Michael D.
Published: July 2002

Because of the current interest in shallow water, propagation model capabilities have been developed for elastic, poro-elastic, and poro-acoustic sediments. These models incorporate depth and range heterogeneities in the sediments, which are assumed to be spatially isotropic. However, many shallow environments have a layered structure which often is more appropriately characterized as transversely isotropic. This feature arises from deposition and layering processes influenced by gravity, for example. Transversely isotropic sediments have elastic properties with considerable variations perpendicular to their natural plane, in which relatively little variation occurs. Efficient and accurate two-dimensional PE models are available for a variety of spatially isotropic sediments, and generalizations are needed for transversely isotropic cases. Our initial two-dimensional development assumes that the plane of the sediment is approximately horizontal. The PE formulation is presented for an elastic sediment and then extended to poro-elastic cases. An initial high-order implementation will be described. [Work supported by ONR.]
Source modeling for the axial fan noise
Authors: Kang Jongmin , Park Seungchul
Published: July 2002

A program for predicting the sound power level from earth-moving equipment is under development in SHI. Fan noise is one of the major sources, whose contribution is greater than 40% of the total radiated noise power. The experiments show that both the blade passing frequency (BPF) component and the broadband component are important, and the directivity pattern is not symmetric with respect to the plane between the upstream and downstream flow. A noise source model of the fan radiator combination for predicting both the directivity and the frequency spectrum is developed from the experimental measurements. In this paper, a physical interpretation is made for modeling the types, shapes, and locations of the simple sources depending on the fan noise generating mechanisms. The minimum number of measurements for the cross-spectral approach are also considered based on the tolerable accuracy and the physically interpretable simplicity.
The role of infant speech perception capacities in discovering the sound structure of the native language
Authors: Jusczyk Peter W.
Published: July 2002

The past quarter century of research on the development of speech perception has documented a number of important capacities that infants possess for recovering information from the speech signal. Such capacities provide the infant with the means to initially categorize speech input. Yet, because individual languages differ greatly in their sound structures, any language-general capacities for processing speech must eventually give way to ones that are more appropriately tailored to the specific language spoken in the infant’s native environment. Recent studies suggest that during the second half of their first year, infants are learning about the specific properties and organization of native language sound patterns. Moreover, there is evidence that infants begin to adapt and adjust their capacities to the structure of their language input. In addition to outlining some of the landmarks observed in the development of speech perception capacities during the first year, some consideration will be given to how these capacities interact with the input to facilitate the acquisition of a native language.
Further studies of perception of speech and music in children
Authors: Castro-Sierra Eduardo , Paredes-Diaz Eliseo , Lastra Yolanda , Gómez-Gama Martha , Perez-Ruiz Santiago J.
Published: July 2002

The present research is a continuation of an investigation carried out at C.C.R.M.A., Stanford University [J. Acoust. Soc. Am. 93, 2403(A) (1993)], on the perception of the pitch of speech and music in children. Experiments sought to determine whether male and female subjects [N=120 (40×3)] 6 to 14 years of age, monolingual speakers of either Spanish, a tongue with prosodic pitch contrasts, or Otomi or Zapotec, Otomanguean tongues with lexical pitch contrasts between words, and having training in singing or in diverse musical instruments would perceive the pitch of speech as they perceived the pitch of musical sounds. Data obtained provide information that Spanish-speaking subjects at all ages and younger Otomi- and Zapotec-speaking subjects perceived the pitch of samples of their language in a manner that was similar to their perception of the pitch of synthesized musical samples. These results applied irrespective of musical background. On the other hand, older subjects speaking Otomanguean tongues seemed to perceive the lexical pitch shifts in words of their language in a manner contrasting with the perception of musical pitch. Neurosurgical studies are in progress to assess whether these differences are due to changes in the cerebral localization of pitch perception in the course of central auditory development.
The prosody of broad and narrow focus within noun phrases
Authors: Hoskins Steven R.
Published: July 2002

Linguistic focus is an important factor in determining nuclear and prenuclear accents, according to current phonological theories [E. O. Selkirk, Phonology and Syntax (MIT, Cambridge, MA, 1984); E. O. Selkirk, ‘‘Sentence prosody: Intonation, stress, and phrasing,’’ in Handbook of Phonological Theory, edited by J. Goldsmith (Blackwell, Oxford, UK, 1995), pp. 550–569]. In some cases, one prosodic realization of a sentence may correspond to more than one focus [E. O. Selkirk, Phonology and Syntax (MIT, Cambridge, MA, 1984); E. O. Selkirk, ‘‘Sentence prosody: Intonation, stress, and phrasing,’’ in Handbook of Phonological Theory, edited by J. Goldsmith (Blackwell, Oxford, UK, 1995), pp. 550–569]. There is little experimental data that directly bear on this issue, however. This study presents a speech production experiment on broad and narrow focus within one structure predicted to allow prosodic ambiguity: noun phrases (NPs) with an adjectival modifier. Sentences were read by 15 subjects under three focus conditions: (1) broad (on NP); (2) narrow-final (on noun); (3) narrow-early (on adjective). Speech and electroglottographic (EGG) data were recorded and analyzed. Acoustic measurements (duration, f0, rms amplitude) and a prosodic transcription revealed the following results: (1) Accents were more likely to be present on prenuclear adjectives under broad focus; (2) broad and narrow focus were often distinguished by the nuclear accent type. [Work supported by NIDRR Grant No. H133E30010.]
Modal mapping in a complex shallow water environment
Authors: Frisk George V. , Connor Laurence N. , Becker Kyle M. , Doust Barry J.
Published: July 2002

An experimental method is described for mapping the wave-number spectrum of the normal-mode field as a function of position in a complex, shallow-water waveguide environment whose acoustic properties vary in three spatial dimensions. The experimental configuration consists of a fixed source radiating one or more pure tones to a field of freely drifting buoys, each containing a hydrophone, GPS and acoustic navigation, and radio telemetry. The precisely navigated, drifting hydrophones form a two-dimensional, synthetic aperture planar array that can be used to determine the evolution of the normal modes in range and azimuth. By describing the spatially varying spectral content of the modal field, the method provides a direct measure of the propagation characteristics of the waveguide. The resulting modal maps can also be used as input data to inversion techniques for obtaining the acoustic properties of the waveguide. [Work supported by ONR and ARL Penn State Univ.]
Whistle matching in wild bottlenose dolphins
Authors: Janik Vincent M.
Published: July 2002

Bottlenose dolphins (Tursiops truncatus) produce individually distinctive signature whistles when they are in isolation. These whistles have been hypothesized to be important in individual recognition and group cohesion. However, captive individuals are known sometimes to imitate each other’s signature whistles. Imitation could either lead to confusion over the caller’s identity and act against individual recognition or could be used to address specific individuals in a communication network. In this study a hydrophone array with three transducers was used to investigate whether whistle copying also occurs in the wild. Recordings were made in a 500- m-wide channel in the Moray Firth, Scotland. Caller position was determined by comparing differences in the time of arrival of a sound at different hydrophones. Since signature whistles could not be determined by isolating individuals, exact whistle matching in vocal interactions was used to study copying. The results showed that whistle matching occurred in 17% of all whistle interactions. An analysis of the variability of matched whistles showed similar degrees of stereotypy as reported for signature whistles. Thus signature whistle matching seems to be an important feature of bottlenose dolphin communication in the wild. [This study was funded by a DAAD-Doktorandenstipendium HSPII/AUFE.]
Acoustic streaming at high Reynolds numbers due to focused piston radiation in real fluids
Authors: Younghouse S. J. , Hamilton M. F. , Il’inskii Yu. A. , Zabolotskaya E. A.
Published: July 2002

In an earlier presentation [Hamilton et al., J. Acoust. Soc. Am. 97, 3376(A) (1995)], a theoretical model for acoustic streaming at high Reynolds numbers (based on streaming velocities) in thermoviscous fluids was used for analytical and numerical predictions based on the assumption of weakly nonlinear focused Gaussian beams. Here, numerical calculations of streaming are presented for radiation from circular pistons, both focused and unfocused, and at amplitudes for which shock formation occurs. The forcing function for the streaming equations is evaluated with time-domain numerical solutions of the nonlinear parabolic wave equation. Effects of thermoviscous dissipation on the acoustic waveforms, and in particular on shock structures, are taken into account explicitly. The calculations provide a consistent description of acoustic streaming generated in real fluids by sound beams at moderate amplitudes, either with or without shocks. Because the shocks are not considered to be discontinuous features of the solutions, uniformly valid predictions of streaming are obtained in the transition region encompassing the birth and death of shocks amid the competing effects of dissipation and diffraction. The model accommodates both continuous and pulsed sources. Comparisons are made with experiments reported in the literature. [Work supported by the Office of Naval Research.]
The creation of audible sound from ultrasonic energy: A fundamental paradigm shift
Authors: Norris Elwood G.
Published: July 2002

The author presents HSSTM Technology, the creation of audible sound waves derived as difference information from ultrasonic energy. It will be demonstrated that the original experiments of German physicist, Hermann von Helmholtz, regarding the creation of difference frequencies by sounding two tones loudly in air, can be dramatically enhanced and applied to audio reproduction using ultrasonic frequencies. It will be shown that by emitting a complex ultrasonic wave into air from a single transducer, it is possible to produce difference frequency sound waves. Further, it will be shown that this audible ‘‘difference’’ sound is propagated as an independent wave once it is created in air. The technique eliminates the traditional need for multiple transducers, crossovers, and enclosures. The ability to ‘‘project or shine’’ sound in a particular direction is shown to be an inherent benefit of this technique. The reproduction of broadband music using this methodology will be demonstrated. An overview of the underlying science, physics, and mathematics supporting this technology will be presented.
Guidelines for reporting community noise-reaction studies
Authors: Fields James M.
Published: July 2002

Difficulties in comparing studies that use inconsistent reporting and measurement procedures have long been recognized as major impediments to the accumulation of knowledge about community response to noise. Gaps in the information presented in publications have been especially serious problems for combined social and acoustical surveys of residents’ responses to environmental noise. In an attempt to alleviate this problem an ICBEN team, Community Response to Noise, recommends guidelines for reporting on combined social/acoustical surveys of residents’ reactions to noise. The guidelines are the result of a 3-year development process that involved consultation with more than 70 experts from 12 countries. If implemented, the reporting guidelines would contribute to the development of cumulative, scientific findings from combined social and acoustical community noise surveys. The guidelines have been developed for three types of publications for information on 18 topics that come under the general headings of overall survey design, survey sample description, data collection methods, acoustical parameters, dose/response reporting, and explanatory variable reporting.
Comparison of low-frequency communication by footdrumming in three species of solitary, desert rodent, kangaroo rats (Dipodomys)
Authors: Randall Jan A.
Published: July 2002

The ears of desert rodents are well adapted for receiving low-frequency vibrations created during footdrumming. Kangaroo rats drum species-specific patterns, ranging from single thumps to individual footdrumming signatures. The desert kangaroo rat, D. deserti, drums single thumps spaced 0.25 to 0.30 s apart. The giant kangaroo rat, D. ingens, drums long footrolls that can average over 100 drums at 18 drum/s. The banner-tailed kangaroo rat, D. spectabilis, drums footdrumming signatures consisting of 3–38 footdrums in a footroll combined into sequences of 2–13 footrolls. In playback tests, all three species stood alert and entered the burrow in response to footdrumming of their own and other species. The rats also responded in species-specific ways. D. spectabilis drummed to its own species’ footdrumming, but not to playbacks of single drums of D. deserti. D. deserti did not footdrum in response to the playbacks, but approached the speaker more frequently than either of the other two species. D. ingens footdrummed equally to all footdrumming playbacks. The species’ differences reflect differences in social tolerance and spacing. D. deserti chases visitors from the burrow, D. spectabilis engages in frequent footdrumming exchanges, and D. ingens tolerates close neighbors and footdrums periodically.