bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative studies of masking by harmonic complexes in several species of birds
Authors: Dent Micheal L. , Dooling Robert J. , Leek Marjorie R. , Mavilia Melonie R. , Lohr Bernard
Published: July 2002

Studies of masking by harmonic complexes have been useful in identifying some of the mechanisms that may contribute to the processing of complex sounds. In humans, for instance, harmonic complexes constructed in positive and negative Schroeder phase are differentially effective as maskers even though they have identical temporal envelopes and long-term spectra — a result that may reflect the phase response of the mammalian basilar membrane. Recent experiments on budgerigars show significant differences from the responses observed in humans [Dent et al., J. Acoust. Soc. Am. 104, 1811 (1998)]. Here, we extend the generality of the budgerigar masking results to three other bird species. Masked thresholds for tones embedded in Schroeder-phase maskers were measured in budgerigars, canaries, zebra finches, and fire finches using operant conditioning and the method of constant stimuli. All species produced similar masking results to those reported earlier for budgerigars: none of the birds showed greater masking by the negative than the positive-phase waveforms, and in some cases the positive waveform was the more effective masker. These results may reflect general differences in the processing of complex sounds in avian versus mammalian cochleas. [Supported by NIH R01 DC00198 and NRSA DC00046.]
Masked hearing thresholds and critical bandwidths for dolphins and a white whale at 20 and 30 kHz
Authors: Schlundt Carolyn E. , Finneran James J. , Carder Donald A. , Ridgway Sam H.
Published: July 2002

Critical bandwidth is an important measure of the frequency selectivity within the auditory filters of the ear. In studies of masked hearing thresholds, the bandwidth of the masking noise must be greater than the subject’s critical bandwidth for the frequency of interest. There have been few direct measurements of critical bandwidths for dolphins and none exist for white whales. Underwater pure-tone hearing thresholds were estimated for three dolphins, Tursiops truncatus, and one white whale, Delphinapterus leucas, at 20 and 30 kHz. Band-limited Gaussian masking noise projected at 80 and 90 dB re: 1 μPa2/Hz was centered around the test frequencies. Six different noise bandwidths were used in threshold estimation and were presented in a quasi-random order. Bandwidths had Q values of 0.8, 1, 1.3, 2, 4 and 10, where Q is the ratio of the center frequency to bandwidth. Thresholds were estimated using the method of free response paradigm and an up–down staircase psychophysical procedure for stimulus presentation. Results of the present study add to the existing knowledge of critical bandwidths for dolphins and provide the first data on critical bandwidths for white whales. [Work supported by the Office of Naval Research.]
Modeling of transient scattered field
Authors: Lesniewski P. , Nafalski A.
Published: July 2002

The spatial impulse response approach has been used to formulate an analytical model which could be helpful in predicting transient distortion by rigid scattering objects with regular/simple forms. The transient field is obtained as a linear convolution of the spatial impulse response (related to the Huygen’s construction and object’s geometry) with the free-field acoustic signal. The time-domain description is attractive since it allows for an easy separation of the incident and scattered field, for a strict representation of the wavefront and it may also allow for a closed—rather than integral—form of the solution for the scattered wave. Experimental results in which transients scattered by a large metal sheet were recorded at various positions near its edge in an anechoic chamber and which are in agreement with the classical harmonic integral description have been compared with approximate transient solutions obtained for a rigid half-plane scatterer. Possible closed-form solutions for the above scatterer are also discussed and related to the boundary conditions concluded from the experiment. [Acknowledgments: to Professor Harry Green for his intellectual support of this research and to Professor Richard Thorn for his long-term support and advice.]
Dan Martin...architectural acoustician
Authors: Cavanaugh William J.
Published: July 2002

Dan Martin’s interest in architectural acoustics was aroused early in his academic years and remained for his entire professional life. While a graduate student and teaching assistant in the Physics Department at the University of Illinois, 1937–41, he worked closely with the pioneering acoustical consultant, Dr. Floyd R. Watson, on acoustical testing at the Purdue Music Hall, the Indianapolis Coliseum, the Indiana University Auditorium among others. During a period of eight years while working on research assignments for various divisions of RCA, Dan did part-time consultations on hundreds of applications of sound amplification equipment in motion picture theaters and auditoriums as well as applications in broadcast and recording studios. During Dan’s long career at the Baldwin Piano and Organ Company, from which he retired in 1983 as Director of Engineering and Research, he consulted on the development and installation of Baldwin electronic organs in a multitude of architectural spaces and was Baldwin’s premier in-house consultant on all matters acoustical. After Baldwin, Dan continued and intensified his consulting in architectural acoustics and noise control joining the National Council of Acoustical Consultants in 1983 at the urging of his many consulting colleagues. During his long and prolific consulting career, circa 1957 through 1998, Dan had over 500 projects many in worship and music performance spaces for which he had special interest. For Dan Martin, consulting in architectural acoustics was challenging and enormous fun. This paper highlights some of those joyful moments and it is hoped that any and all who have recollections of Dan’s consulting experiences over the years will spontaneously share them with us at this special tribute session to a friend and colleague who has marked our Society so indelibly.
Challenges of modeling aircraft noise in national parks
Authors: Plotkin Kenneth J.
Published: July 2002

Aircraft noise in national parks has become a matter of concern in recent years. Modeling that noise for purposes of impact assessment and decision making poses challenges that are generally not present for conventional airport noise analysis. People present in parks are not residents, so conventional annual DNL analysis cannot be assumed to be appropriate. The concept of natural soundscape as a resource requires that noise be quantified on a much broader basis than for the conventional people-animals-structures perspective. Parks can also have a variety of ground cover and terrain, with terrain quite extreme in places. Despite the differences, and obvious extended capabilities required, any noise model must have a solid relation to existing standard practices. This paper reviews the issues which must be addressed in a model which is suitable for modeling of noise in national parks.
Acoustic methods for classification of fluids in sealed containers for identification of hazardous chemicals
Authors: Sinha Dipen N. , Kaduchak Gregory
Published: July 2002

There are many situations where it is necessary to be able to determine information about the liquid contents inside sealed or otherwise inaccessible containers. Typically for classification of a liquid filler, one needs to determine some simple properties of the liquid contents, such as the sound speed, density, and attenuation of the liquid. This information is often sufficient to identify and characterize various subclasses of chemicals. In cases where the containers are to contain hazardous chemicals (e.g., chemical warfare agents, highly toxic chemicals, highly flammable liquids, etc.) it may be unsafe for operators to make measurements using traditional techniques which require direct contact with the contents. This talk will address several techniques which address fluid classification for situations where direct contact with the fluid is not feasible. It will concentrate on methods which couple acoustic energy into the interior container cavity (by means of direct contact or stand-off methods) to extract frequency dependent acoustic information to serve as classification clues to identify the filler.
Temperature dependence of diffuse field phase
Authors: Weaver Richard L. , Lobkis Oleg
Published: July 2002

We report on a new method for ultrasonic interrogation of solids. Diffuse fields are usually examined by means of the time evolution of their spectral energy density. The phase information is usually discarded as resisting analysis. The phase, while unpredictable, is, however, robust; according to theory it remains constant if source, medium, and receiver are not disturbed. Nevertheless, slow drifts of phase are observed over time scales of minutes. It is hypothesized that the phase changes are due to temperature fluctuations. A wideband 1-MHz transient source in an aluminum block was used to generate a complex waveform whose phase changes on cooling from 40°C to room temperature were monitored. The waveform was found to undergo a virtually pure dilation, by a factor of order 0.00025/°C, a figure which is in accord with published data on the temperature dependence of ultrasonic velocity in aluminum. Due to the low dissipation in the sample, the precision with which changes are measured exceeded a part in ten million, a figure which could be improved by employing a stronger source. The possibilities that this parameter is a measure of residual stress or other NDE parameter, is explored.
Leaky integrators, Fletcher curves, and period histograms: A new link
Authors: Berg Bruce G.
Published: July 2002

Fletcher curves, thresholds from tone-in-noise detection tasks plotted as a function of masker bandwidth, are thought to reflect characteristics of peripheral filters. This notion, however, is compromised by the finding that a roving level procedure affects thresholds only for very narrow bandwidths [Kidd et al., J. Acoust. Soc. Am. 86, 1310–1317 (1989)]. Alternatively, a three-stage, leaky integrator (i.e., initial, relatively broad bandpass filter, followed by half-wave rectification and low-pass filtering) yields frequency-dependent, level-invariant Fletcher curves, thus entertaining the possibility that sensitivity to envelope cues underlies detection at all masker bandwidths. The decision statistic is a measure of similarity (Mahalanobis distance) between the observed amplitude spectrum of the leaky integrator output and expected spectra with and without a signal. Regarding physiological plausibility, the model also describes the temporal response of auditory nerve fibers to complex stimuli. Horst et al. [J. Acoust. Soc. Am. 85, 1898–1901 (1985)] used multicomponent, periodic stimuli to obtain period histograms from auditory nerve recordings. Fourier transforms of the histograms were used to assess temporal responses of fibers. For various stimulus configurations, the spectra of the period histogram and leaky integrator output are nearly identical. Theoretical implications are discussed. [Work supported by ONR.]
Magnetic field responses of auditory cortex to produced speech
Authors: Nagarajan Srikantan , Houde John , Merzenich Michael
Published: July 2002

Several behavioral and brain imaging studies have demonstrated a significant interaction between speech reception and speech production. In this study, the dynamics of modulation of auditory cortical responses to speech during self-production and feedback alteration were examined. Magnetic field recordings were obtained from both hemispheres of subjects who spoke while hearing controlled versions of their feedback via earphones. These responses were compared to magnetic field recordings made while subjects listened to a tape recording of their production. The amplitude of the tape playback was adjusted to be equal to the amplitude of produced speech. Successful recordings of evoked responses to both self-produced and tape-recorded speech were obtained free of movement-related artifacts. In all subjects, a progressive differentiation in the dynamics of the responses to self-produced speech and to recorded speech was observed. In several subjects, a clear bilateral suppression of amplitude of the peak response 100 ms after stimulus onset was also observed. Feedback alteration enhanced the evoked response to produced speech. [Work supported by the McDonnell-Pew Foundation, the Coleman Fund, HRI, and Scientific Learning Corp.]
Peripheral factors in loudness adaptation with OAE effects
Authors: Dou Hongwei , Weiler Ernest M. , Kretschmer Laura , Sandman David E. , Goldman Thomas
Published: July 2002

Tone decay (TD), the ipsilateral comparison paradigm (ICP), and the monaural simple adaptation (SA) procedure assess loudness adaptation differently; this may all be peripheral but it has not been previously compared in one study. Transient evoked oto-acoustic emissions (TEOAE) have their source in the outer hair cells of the cochlear periphery. A significant correlation (r=−0.60) between contralateral suppression of transient evoked OAEs and tone decay adaptation (r=−0.60) has been reported [Collet et al., Audiology 31, 1–7 (1992)]. A significant correlation (r=−0.36) between ICP adaptation and contralateral suppression of TEOAEs has been found [Ernest M. Weiler, Hongwei Dou et al., J. Acoust. Soc. Am. 103, 3052 (1998)]. Comparison of TD, ICP, and SA with suppression of TEOAEs used repeated measures testing of 75 students (20–35 yrs) of mixed nationalities. Significant correlations were found, but not at all values, between TD, ICP, SA, and suppression of TEOAEs at 80, 60, and 70 dB. A principle components factor analysis found factor I based on suppression, and factor II based on monaural adaptation. It was concluded that the ICP, TD, and SA are primarily peripheral in origin. TD and ICP each include variation in stimulus intensity which may play a role in triggering perception of loudness adaptation.
Validity of the small perturbation method for volume scattering from marine sediments
Authors: Jones Christopher D. , Jackson Darrell R.
Published: July 2002

For high-frequency volume scattering and propagation in marine sediments (at 10–500 kHz), the validity of single scattering methods (e.g., Born approximation) is not well established. Insight into whether single or multiple scattering is significant in a medium can be gained using effective medium theory (bilocal approximation to Dyson’s equation). An alternative analysis can be made using exact numerical Monte Carlo simulations. In this talk, both multiple scattering theory and numerical methods will be used to investigate the applicability of the small perturbation method for volume scattering from a sediment half-space. Parameters of the sediment are limited to marine sand and mud modeled as an acoustic fluid with Gaussian random fluctuations in density and compressibility. Sediment properties (from core sampling) are taken from published data on four experiment sites: Orcas Island; Eckernfoerde Bay; STRESS Midshelf; and Panama City. It is shown that strong scattering may be significant at the Panama City site (assuming the core estimates are accurate). However, even when strong scattering is predicted, the presence of a ‘‘transition layer’’ near the sediment–water interface reduces the effect of multiple scattering on the far-field scattering strength, and the first-order small perturbation approximation may still be applicable.
A boundary element method for pressure and intensity of broadband high-frequency, nonuniform, nondiffuse sound fields in enclosures
Authors: Franzoni Linda P. , Bliss Donald B. , Rouse Jerry W.
Published: July 2002

A boundary element method for high-frequency sound fields in enclosures is formulated in terms of time-averaged energy and intensity variables. The approach is applicable to high modal density fields, but is not restricted to usual low absorption, diffuse, and quasi-uniform assumptions. The basic building block for the method is a broadband intensity/pressure source. This source has directivity characteristics that are related to the surface correlation distance and the spatial distribution of the incident field falling on the source location. These sources are distributed over the enclosure surfaces to satisfy boundary conditions on normal intensity. The boundary elements are constructed by integrating intensity/pressure sources over local panels. Sample calculations are performed for rectangular enclosures with different absorption levels and source positions. Results for spatially varying mean square pressures are compared with computationally intensive exact solutions and are found to give reasonable agreement at a small fraction of the computational cost. Some interestingissues in the modeling of spatially varying reverbrant fields are also discussed. [This work was supported by NSF.]
Uniform error distribution in one-third octave band frequency analysis
Authors: Martin Alberto , Recuero Manuel , de Arcas Guillermo , Ruiz Mariano
Published: July 2002

In this paper an algorithm for obtaining a uniform error distribution in one-third octave band frequency analysis is presented. The algorithm is a digital signal processing implementation of the ANSI S1.11-1986 standard based on digital filters. First the effects of constant integration time over error distribution are discussed and then a solution is presented based on a statistical signal processing interpretation of the problem. The power distribution measurement is analyzed and studied as a variance estimation problem to establish the requirements of the analysis algorithm that will guarantee a uniform error distribution. The object of the algorithm is to obtain a uniform error distribution maintaining the total number of operations as low as possible in order to be efficient enough to be implemented in real time. The discussion is completed with several simulation results and a performance comparison with other popular alternatives.
Biological perspectives on noise annoyance
Authors: Bowles Ann E.
Published: July 2002

For humans, annoying noise is any sound that ‘‘disturbs, displeases, troubles, or irritates.’’ In humans, the experience of annoyance is a metric, obtained by self-reporting. In animals, however, biologists can only measure behavioral reactions or physiological events. Based on such measures, three classes of negative reactions to noise have been identified. The first is aversion caused by relatively automatic physical reactions, such as the startle. Unequivocal measures of aversion include learned avoidance, behavioral suppression, and irritability. The second can best be described as motivation to eliminate interference with function. Noise masking is an example of interference with function, and the response can be quantified by work animals are willing to do to overcome the masking noise. Finally, animals can become more defensive in the presence of noise. This change in psychological state is measured by increased levels of vigilance or arousal, increased activity, species-typical defensive behaviors, or attacks on the noise source. Although humans typically empathize most with the first reaction, aversion, interference with function or perpetual defensiveness have similar, if not greater, impact in the long-term. Predictions of impact on both humans and animals will improve with accurate measurements of these biologically meaningful responses to annoying noise.
Physiological responses of harbor seals, California sea lions, and northern elephant seals to simulated sonic booms, air-puffs, and white-noise bursts
Authors: Wolski Lawrence F.
Published: July 2002

As part of a study examining auditory effects of simulated sonic booms on pinnipeds, changes in heart rate, orbicularis muscle activity, and respiration rate were measured. Four harbor seals, four sea lions and three elephant seals were exposed to simulated sonic booms (100 or 300 ms, 1, 3, or 6 psf). Two harbor seals and a sea lion were exposed to 50-ms air-puffs, and a harbor seal and sea lion were exposed to 300-ms white-noise bursts for comparison. Harbor seals responded to simulated booms with bradycardia, reduced movement, and brief apneas, consistent with an orienting response. Elephant seals showed similar responses, but of smaller magnitude. Harbor seal and sea lion responses to air-puffs included increased heart rates and muscle contractions (harbor seals), consistent with the startle response. Harbor seal responses to white-noise included muscle contractions and a brief increase, then decrease, in heart rate. Responses of sea lions to sounds were individually variable. While air-puffs stimulated increases in heart rate and muscle contractions, sounds stimulated both increases and decreases in heart rate, movement, and respiration. These results suggest that pinniped species react similarly to air-puffs, but variably to acoustic stimuli, possilby due to inter-species differences in perception. [Work supported by NASA: NAS1-20101.]
Military training noise impacts on the endangered Red-Cockaded Woodpecker: Preliminary results
Authors: Pater Larry , Delaney David , Hayden Timothy , Dooling Robert , Lohr Bernard
Published: July 2002

A new three-year study has been initiated to determine the degree of impact of military training noise on the endangered Red-Cockaded Woodpecker (RCW). The study is being conducted on an Army installation. The study design and preliminary results from the first nesting season are presented. Noise sources of interest include artillery and tank live fire blast noise, small arms live fire noise, small arms blanks noise and artillery simulator noise that occurs during maneuver training, and helicopter noise. Response criteria include proximate responses such as flushing from a nest and fitness measures such as nesting success. The objective of the study is to determine, for each type of noise, a dose-response relation and/or response thresholds. The study includes a determination of an audiogram for woodpeckers, which will provide the basis for selecting stimulus characterization metrics that include appropriate frequency weighting and will facilitate interpretation of response data. [Work supported by SERDP.]
Sound solutions for cellular phones
Authors: Kjeldsen Morten
Published: July 2002

The ongoing miniaturization of cellular phones during the last years has led to the development of smaller and smaller speakers for these products. Today’s size of a typical speaker for GSM and CDMA phones is of a diameter of 15 and 13 mm, and we are about to see even smaller speakers on the market. In the design and type approval of the receiving part of the cellular phone, the reference is a standardized measuring ear, which seals toward the ear cap plane of the phone. Under these conditions, it is possible to achieve a flat frequency response representing the whole telephone band, even with speakers in small sizes. However, such a tiny speaker in combination with a very small cellular phone having a poor surface of contact to the human ear leads to heavily reduced speech quality, which cannot be reflected in the measurement result. In other words, there is a very poor correlation between the type real life telephone user situation. This presentation gives the guidelines on how to design smaller cellular phones prepared for type approval using small speakers and at the same time improve sound quality.
New approaches in acoustical signal processing
Authors: Candy James V.
Published: July 2002

Signal processing is an integral part of most applications throughout the entire spectrum of acoustical applications, whether it is attempting to extract a resonant vibrational frequency of a structure to canceling noise in an active system or concert hall. Simply, signal processing is aimed at extracting the useful information from data, whether measured or simulated, while discarding the extraneous. Such simplistic ideas as time reversal in ultrasound have led to some rather astounding results in nondestructive evaluation. More sophisticated time-frequency representations incorporating wavelets are routinely applied in animal acoustics, while even more sophisticated techniques like matched-field processing incorporate a sophisticated oceanic propagation model as part of the scheme to localize submarines. In this paper we discuss the broad spectrum of approaches available to solve the basic acoustic processing problem with applications from various disciplines to emphasize the result. Processors discussed range from the simple to the sophisticated as dictated by the application. It is demonstrated how signal processing techniques are crucial to extracting the required information for success of the underlying application.
Hot topics in physical acoustics
Authors: Keolian Robert M.
Published: July 2002

A small fraction of the interesting work being performed in physical acoustics will be highlighted in this talk. From among the topics that could be chosen, two stand out in this author’s mind, as of this writing. Dramatic improvements, by nearly a factor of 2, have been made in the efficiency of thermoacoustic engines by the thermoacoustics group at Los Alamos National Laboratory. Their new geometry brings the efficiency of thermoacoustic devices in line with conventional technologies, without sacrificing simplicity. Another innovative concept has been developed at the University of Mississippi. James Sabatier has invented a very successful method for the detection of buried land mines using acoustic-seismic coupling. This has the potential for saving a tremendous number of lives worldwide.
Focal regions in spectrograms of long range propagation
Authors: Kuperman William A. , D’Spain Gerald L. , Heaney Kevin D.
Published: July 2002

A source near the deep sound channel axis excites mode groups (or paths) that involve both deep sound channel and boundary interacting propagation. Modal group speeds have a functional transition when passing through purely refractive to boundary reflecting phase speed regions. The result is that arrivals in this transition region line up in time across frequency. The combination of this alignment together with a similar, though broader coincidence of the last deep sound channel arrivals provide two time markers on a single phone spectrogram (intensity as a function of arrival time and frequency). Indeed, data from the Acoustic Thermometry of the Ocean (ATOC) program [ATOC Consortium, Science 281, 1327 (1998)] show this effect. These time markers, depending on auxiliary information provide source localization or inversion capability. [Work supported by ONR and DTRA.]
Changes of the acoustic modal phase velocity, group velocity, and interference distance in an eddy
Authors: Tianfu Gao , Yaoming Chen
Published: July 2002

In this paper, by using the modal dispersion equation with the phase-integral approximation, and considering an eddy (or water mass) as a sound channel disturbance, the effects of the undisturbed channel, cold-core eddy, and warm-core eddy on the acoustic propagation characteristics are discussed. According to the solutions of the dispersion equation, the relation is obtained between the modal phase velocity (Cn), group velocity (Un), and interference distance (Ln), and the eddy intensity. When the plane wave (with an incident angle α) travels toward the center of a warm-core eddy (disturbed intensity BM), ‘‘double channel phenomenon’’ will take place in case of sin2α<BM<2(1−cosα), and then the modal phase velocity and interference distance will have anomalous changes. The interference distance of normal mode has a minimum. The larger the number of modes and the higher the source frequency, then the more obvious the ‘‘hollow case’’ for interference distance. However, for any cold-core eddy, the modal phase velocity or the interference distance will be monotonically changed.
Experimental studies of the use of a split-beam transducer for prostate cancer therapy in comparison to a single-beam transducer
Authors: Wu Jimmy S. J. , Sanghvi Narendra T. , Phillips Michael , Kuznetzov M.
Published: July 2002

The therapy of prostate cancer by high-intensity focused ultrasound (HIFU) requires the treatment of whole prostate tissue. Single-beam HIFU results in treatment time of about 3 to 4 h. However, the treatment time can be reduced by the use of multiple HIFU beams that are generated simultaneously. We have approached this problem by splitting the main ultrasound beam into one main beam that is surrounded by multiple sidelobes (coined ‘‘split-beam transducer’’). In our split-beam transducer by means of geometrical configuration of the transducer, the main beam is surrounded by four sidelobes, producing a focal area about three times larger compared to that of a single beam. The step size between two adjacent ablative exposures can be increased using SBT. Experiments were designed to understand the use of ‘‘split-beam transducer (SBT)’’ on the Sonablate 200 device (Focus Surgery Inc.). Test objects, (1) Mylar strip, (2) Plexiglass block, and (3) turkey breast tissue were used. Temperature measurements using multiple thermocouples were made in the tissue near the beam entrance and about 5 mm deep into the samples. Results show that the split beam creates a larger volume of lesion than the single beam in turkey breast tissue. For the single beam used in BPH treatment step size was set at 1.8 mm to create connected necrosis. In the current study a step size of 2.5 mm can be used to create a connected lesion in turkey breast tissue, leading to a 30% reduction in treatment time for the same volume of tissue.
In vivo ultrasound-induced occlusion of arteries and veins
Authors: Hynynen Kullervo , Colucci Vincent
Published: July 2002

In this study rabbit ear vessels were sonicated in vivo with focused spherically curved ultrasound transducer (diameter 100 mm, radius of curvature 80 mm, frequency 2 MHz). The sonication duration was varied from 0.2 to 5 s. The acoustic power was between about 50 and 200 acoustic watts. The vessels were visualized under microscope during and after the sonication to follow the blood flow and the vessel diameter. A video camera on the microscope was used to record the observations. The sonication caused blood vessels to contract temporarily at low powers and at high powers the vessels occluded and remained closed over the 2-h follow-up. However, the x-ray angiograms performed by injecting x-ray contrast agent in the ear vessels after the animal was sacrificed showed often that complete occlusion was not achieved. A further increase in the power caused the skin to coagulate and these effects had less effect on the blood flow. The vessels were completely sealed by performing a follow-up sonication at about 34 W for 10 s. This coagulated the tissue around the blood vessels and stopped the flow.
A hemisphere transducer array for transskull ultrasound therapy and surgery
Authors: Sun Jie , Clement Greg , Hynynen Kullervo
Published: July 2002

Recently, it has been shown that it is feasible to generate a focused ultrasound field through an intact human skull for therapeutic purposes. Also it is clear that, in order to minimize the skull heating, a large 2-D array should be adopted to maximize the penetration area on the skull. With this in mind, an unconventional hemisphere transducer array is studied and developed. The radius of the transducer is chosen to be 15 cm in order to accommodate most head sizes and mechanical shifting while the transducer can still be fit into an NMR magnet coil to monitor treatments. The transducer’s operating frequency, total number of elements (and the associated element size), and element geometry are determined based on numerical studies. The numerical results are presented for the transskull ultrasound field when the transducer is divided into 228 elements. The transducer is constructed and tested in water bath. The preliminary experimental results using this transducer are also presented.
Ultrasonic spectroscopy inversion method for the determination of thicknesses and acoustical properties in a thin-layered medium
Authors: Lévesque D. , Choquet M. , Massabki M. , Néron C. , Monchalin J-P.
Published: July 2002

Ultrasonic waves reflected from the front and back surfaces of a thin-layered medium (<2 mm) overlap and interfere in the time domain. A spectroscopy approach has been proposed in the past, collecting and analyzing a large number of echoes together in the frequency domain to measure resonance frequencies and determine properties of the layered medium. With the presence of a fluid between layers, the resonance modes are mainly those of individual layers in the vacuum and an inversion algorithm has been successfully applied to recover some properties. For adhesively bonded layers, the resonance modes of the different layers are strongly coupled and important frequency shifts are observed. In this paper, a characteristic equation which includes an adhesion parameter has been derived and a numerical inversion technique has been used to simultaneously obtain thickness maps of the individual layers from measured resonance frequencies. One application is the laser-ultrasonic detection of hidden corrosion in aircraft lap joints where the paint layer has a significant impact on the resonance frequencies of the paint/metal–skin structure. Results will be presented for samples simulating aircraft lap joints with various levels of metal loss. [Work funded by the U.S. Department of Defense under Contract F33615-98-C-5200.]
Estimation of model-parameter errors
Authors: Serbyn M. Roman
Published: July 2002

The linear time-invariant two-port, characterized by four complex parameters, has established itself as a reliable model for a variety of physical systems. It has been studied in two aspects: as the ‘‘forward’’ problem (analysis) and the ‘‘inverse’’ problem (synthesis). The focus of the research here reported is on the latter, that is, on inferring the values of the model parameters from the results of measurements at the input and output ports. In particular, the goal of this investigation has been to quantify the relationship between uncertainties in the measured values and the resulting errors in the parameter estimates. Two physical systems have been used in the present study: an electrical circuit with known component values and an uncalibrated electromechanical transducer. Mathematically, each device was modeled as a Moebius transformation, w=(az+b)/(cz+d), whose parameters, (a,b,c,d), were estimated from least-squares fits to measured values of the variables (z,w). The a priori known electrical circuit provided a base line for checking the validity of the computation algorithms. maple, matlab, and spice programs were utilized. [Work supported by HUD Special Projects Grant No. B98SPMD0074.]
Smart structures and microelectromechanical systems (MEMS)
Authors: Khuri-Yakub B. T.
Published: July 2002

Capacitor transducers have been around for as long as piezoelectric transducers. They have not presented much competition for piezoelectric transducers as transmitters and receivers because the method of their manufacture did not optimize and highlight their performance. With the advent of silicon micromachining, it is now possible to make capacitors with very thin gaps that sustain electric fields of the order of 109 V/m or more. At these levels of electric field, the transformer coupling between the electrical and mechanical parts of the capacitor transducer, and thus its performance, become comparable to that of piezoelectric transducers. Advantages such as practically infinite bandwidth, ease of manufacture, and the ability to integrate electronic circuitry make this type of transducer a very important candidate for many ultrasonic applications. We will review the design and performance of capacitor transducers for both immersion and airborne ultrasound applications. Single-element, 1-D, and 2-D arrays of transducers will be presented along with imaging results. The overall dynamic range of systems with these transducers will be shown to be over 140 dB/V/vHz. We will also present a design for making surface-wave and Lamb-wave transducers using the same capacitor concept. [This work was sponsored by the Office of Naval Research, the Defense Advanced Research Projects Agency, and the Air Force Office of Scientific Research.]
Issues in music, rhythm, and development
Authors: Riess Jones Mari
Published: July 2002

Some general issues pertaining to the response of infants and children to auditory patterns will be discussed. One issue concerns the tempo of simple auditory sequences used as stimuli in perception and production experiments with subjects of different ages. Is there any evidence that children exhibit preferences for certain tempi? If so, do these preferences change with age? What implications can we draw from such findings? A second issue concerns children’s sensitivity to relative time structure, including hierarchical time relationships. To what extent are children of different ages responsive to higher-order time relationships, e.g., as in metrical time relationships? A third issue also concerns relative timing. Are young children and/or infants preferentially sensitive to certain kinds of rhythmic relationships? If so, what might these be and what does this imply for understanding the development of rhythmic competencies? This talk will selectively review research addressed to these topics. The aim is to suggest a few general themes that are emerging in the field.
Recognition of prosodic cues in music performance
Authors: Palmer Caroline , Blakeslee Melissa K. , Jusczyk Peter W.
Published: July 2002

As early as infancy, humans are sensitive to prosodic cues that can aid recognition of words embedded in sentence contexts. We addressed the question of whether similar cues formed by expressive nuances in music performances aid listeners in recognition of musical phrases embedded in melodic contexts. Utilizing a task similar to infant-research habituation paradigms, we report experiments with musically experienced and inexperienced listeners who are familiarized with performances of musical phrases that were identical in pitch/duration contents but differed in their intensity and articulation cues. Listeners then completed a recognition task for performances of the same musical excerpt whose cues either matched or did not match the performances at familiarization, and whose cues were either consistent or inconsistent with the rhythmic context in which the excerpts were embedded. Findings show that listeners can distinguish musical phrases that differ only in expressive nuances, and a mismatch of expressive nuances to the rhythmic context can facilitate recognition. These findings suggest that the prosodic cues that differentiate human performances are part of listeners’ memory for melodies, and similar acoustic features may enable the recognition of auditory events in music as in speech. [Work supported by NIMH.]
Modulation gap detection: Effects of modulation rate, carrier separation, and mode of presentation
Authors: Grose John H. , Hall Joseph W. , Buss Emily
Published: July 2002

Modulation gap detection (MGD) is a procedure that measures the sensitivity to an interruption in the modulation pattern imposed upon one or more carrier frequencies. The MGD task was developed to test conditions where a temporal event traverses frequency, but without a concomitant interruption in the spectral continuity of the stimulus. This contrasts with across-frequency gap detection where there is an inherent spectral discontinuity associated with the temporal gap, and where there is a marked decline in performance when the markers of the temporal gap are widely separated in frequency. The purpose of this study was to test the hypothesis that a wideband temporal analysis will be facilitated if there exists a spectral continuity throughout the temporal event. Experiment 1 established the procedure of MGD and indicated that a modulation rate of 8 Hz was optimal for the task. Experiment 2 showed that performance declined markedly when the carrier frequencies of the modulation markers were widely separated in frequency. This finding indicates that spectral continuity across the temporal event is not a sufficient prerequisite for the auditory system to undertake a wideband temporal analysis. Experiment 3 revealed that dichotic MGD also results in poor performance, similar to that seen for widely separated carrier frequencies in the monaural case. This supports the hypothesis that the “channels” across which temporal events are poorly processed do not necessarily correspond to peripheral frequency channels.
Contextual influences on the internal structure of phonetic categories: A distinction between lexical status and speaking rate
Authors: Allen J. Sean , Miller Joanne L.
Published: July 2002

A series of experiments examined the effects of an acoustic-phonetic contextual factor, speaking rate, and a higher-order linguistic contextual factor, lexical status, on the internal structure of a voicing category, specified by voice-onset-time (VOT). In keeping with previous results, speaking rate fundamentally altered the structure of the voiceless category, not only affecting the perception of stimuli in the voiced–voiceless category boundary region but also altering which tokens were rated as the best exemplars of the voiceless category. In contrast, the effect of lexical status was more limited. Although (as expected) lexical status also affected the perception of stimuli in the category boundary region, this effect disappeared in the region of the best-rated exemplars. This distinction between the effects of speaking rate and lexical status on the internal structure of the voiceless category mirrors the effects of these factors in speech production: It is well known that speaking rate alters the VOT values of voiceless consonants, whereas we confirmed in a speech production experiment that lexical status has no such effect. Based on these findings, we argue that higher-order contextual factors such as lexical status operate differentialy in processing from production-based, acoustic-phonetic factors such as speaking rate. [Work suppported by NIH/NIDCD.]
Effects of speech rhythm on timing accuracy of stressed syllable beats
Authors: Port Robert F. , Kitahara Mafuyu , de Jong Kenneth , Collins David R. , Burleson Deborah Felkins
Published: July 2002

It has been shown that English speakers have a strong tendency to locate stressed syllable onsets (that is, ‘‘beats’’ or ‘‘P centers’’) near harmonic fractions (like 1/2, 1/3, 2/3) of the repetition cycle of a repeated phrase [Cummins and Port, J. Phonetics (1999)]. These results were interpreted as evidence of a role for frequencies at multiples of the repetition cycle creating temporal attractors for stressed syllable onsets at harmonic fractions of that cycle. If harmonic oscillators account for temporal attractors, then, having an attractor at 2/3 should necessarily imply the existence of an attractor at 1/3, whereas an attractor at 1/2 would not similarly imply an attractor at 1/4 (since a third oscillator would be required). Thus, if a phrase like take a pack of cards is repeated with card onset at phase 1/2, there should be a weaker attractor controlling the timing accuracy for pack onset than if card onset is at 2/3. Four speakers were tested using various text materials and speaking rates. Preliminary results support the hypothesis predicting greater temporal variability for pack with card beginning at 1/2 than at 2/3.
Evidence from /k/ versus /t/ burst spectra for variable lingual contact precision in normal versus atypical phonological development
Authors: Edwards Jan , Fourakis Marios , Beckman Mary E. , Welby Pauline , Katagiri Satoko
Published: July 2002

Almost universally, phoneme inventories include at least one pair of lingual consonants contrasting an apical ‘‘front’’ contact to a dorsal ‘‘back’’ contact. Studies of infant productions across languages suggest that control of this contrast is acquired later than that between lingual and labial contact, and ‘‘velar fronting’’ (apparent substitution of /t/, /d/ for /k/, /g/) is a commonly observed pattern of functional misarticulation in English-acquiring children. This study uses spectral moments analysis of the burst to examine the patterns of emerging differentiation of alveolar and velar voiceless stops in eight pairs of preschool children with phonological disorder and normal age peers. Productions of four adults showed consistently higher skewness values and lower center of gravity for /k/ as compared to /t/. The children showed considerable intersubject variability, with some exaggerating the adult distinction and others showing substantial overlap. There was especially extreme overlap in the productions by children with ‘‘velar fronting.’’ However, the spectral moments values for these children did not suggest a categorical substitution. Instead, values were in the middle of the distribution on both dimensions, as if the child were making an ‘‘undifferentiated lingual gesture’’ [F. E. Gibbon, J. Speech. Hear. Language Res. 42, 382–397 (1999)]. [Work funded by NIDCD No. DC02932.]
Masked temporary threshold shift for impulsive sounds in dolphins and white whales
Authors: Carder Donald A. , Finneran James J. , Ridgway Sam H. , Schlundt Carolyn E.
Published: July 2002

In an effort to develop acoustic safety criteria for marine mammals that may be exposed to impulsive sounds a masked temporary threshold shift (MTTS) experimental approach was used. Two dolphins, Tursiops truncatus, and two white whales, Delphinapterus leucas, were systematically exposed to increasing levels of impulsive sound (S-1) under water, then tested to threshold at three pure-tone frequencies (S-2) under water in the presence of controlled masking noise. One hearing frequency tested was at the pulse peak frequency, with the other two S-2 test tones at higher frequencies. Behavioral responses were monitored and hearing thresholds were ascertained to determine if criterion (6-dB increase over baseline) was reached. Thresholds were estimated using the free response paradigm method and an up–down staircase psychophysical procedure for stimulus presentation in open water in San Diego Bay. These data suggest that the rapid rise time of the leading edge in 1-s tones used in a previous study is not responsible for producing MTTS. Results of the present study add to the existing knowledge of MTTS for marine mammals and provide the first data on MTTS in cetaceans for impulsive sounds. [Work supported by the Office of Naval Research.]
Acoustics of ancient Chinese bells
Authors: Rossing Thomas D.
Published: July 2002

Many ancient Chinese bells, some more than 3000 years old, remain from the time of the Shang and Zhou dynasties. Most of these bells, being oval or almond shaped, sound two distinctly different musical tones, depending upon where they are struck. Studies of these bells have provided us with much knowledge about the musical culture of Bronze age China. Results are reported from our investigations of original bells in the Shanghai Museum and the Sackler Gallery at the Smithsonian Institution, as well as replica bells in our own laboratory. Modes of vibration in original bells, obtained by experimental modal testing in the museum, compare very well with holographic interferograms of replica bells. Our results are compared with our catalogue of data on ancient Chinese bells gathered by other investigators. Although acoustical studies have revealed a great deal about ancient Chinese music and casting practices, several questions still remain unanswered.