bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal processing in water and air: Developmental changes in synchronized response to AM signals across metamorphosis in the bullfrog
Authors: Boatright-Horowitz Seth S. , Simmons Andrea M.
Published: July 2002

Acoustic limitations on propagation of low-frequency complex communication sounds make the amplitude modulation (AM) rate an important auditory feature for both aquatic larval (tadpole) and partly terrestrial (adult) bullfrogs. Phase-locked responses to AM signals were recorded from neurons in the auditory midbrain during metamorphic and postmetamorphic development. The best modulation frequency (BMF) and maximal significant AM rate are significantly negatively correlated with the developmental stage. Pre- and early prometamorphic tadpoles show phase locking to higher AM rates than postmetamorphic animals. Late prometamorphic (deaf period) tadpoles show a substantial reduction in auditory sensitivity, lower BMFs, reduced bandwidths of modulation transfer functions (MTF), and loss of significant phase locking. By the onset of the metamorphic climax, there is a recovery of auditory sensitivity and phase-locked responding, with late climax tadpoles showing auditory sensitivity similar to that of postmetamorphic frogs. The changes in neural responding across metamorphosis are correlated with morphological changes in the auditory periphery and central auditory nuclei, and match differences in the acoustic environment as the animal shifts from an aquatic to a more terrestrial lifestyle. [Research supported in part by an NIH research Grant NS28565 (AMS) and an NSF Graduate Fellowship (SBH).]
Selection of instrumentation for monitoring undersea animal sounds
Authors: Raichel Daniel R.
Published: July 2002

In order to properly select instrumentation for bioacoustic studies, a list of measurable criteria must be drawn up, but even that may not suffice unless some genuine thought is given to the possibility of mapping addi- tional criteria, such as frequencies beyond the range usually considered. In the planning and design of the experiment, some of the criteria include: frequency and dynamic ranges, the number of channels desired (not necessarily always available!), compatibility of components (as exemplified by the matching of acoustical and electrical impedances), setup of sensing/receiving transducer arrays, mode of recording, statistical methodologies, usable computer prowess, etc. Environment constitutes an extremely important factor from two aspects: (1) It should not be adversely affected by the use and operation of the equipment; and (2) the equipment should be able to withstand rigors of temperature, humidity, vibration, and shock. Provision should be made for instrument calibration at proper intervals to ensure the integrity of obtained data. Cost is another factor that can determine the reliability of the equipment, quality of performance, ruggedness, and ease of operation.
Measurement and empirical prediction of bottom surface acoustic pressures on a hover aircraft model
Authors: Kuntz Herbert L. , Hickmon Floyd O. , Feltz Edward P.
Published: July 2002

Acoustic measurements were made on the bottom surface of the 86% scale large-scale propulsion model (LSPM) of an advanced short takeoff and vertical landing (ASTOVL) airplane. The measurements were ob-tained during fixed hover heights where the lower wing surface varied from 5 ft (airplane’s wheels on the ground) through 36 ft above the ground for a wide range of propulsion thrust mixes and airplane control surface configurations. The complete propulsion system provided four exhausts through an integrated unit consisting of an aft located main jet engine, which powered a forward located shaft driven lift fan and was completed with two main engine bleed high-pressure bypass roll jets (in the wings). Flush surface measurements were made at 12 locations on the bottom surfaces and time correlated with the operating propulsion parameters. An empirical acoustic model was made through analyses of the geometry and the data, and was used to predict contours on the bottom of the aircraft. [This work was performed by Lockheed Martin Skunk Works at the NASA-Ames Research Center.]
GenJam: An interactive genetic algorithm jazz improviser
Authors: Biles John A.
Published: July 2002

GenJam is an interactive genetic algorithm that learns jazz improvisation. It uses two hierarchically related populations to represent melodic ideas at the measure and phrase levels. These populations are evolved using tournament selection, single-point crossover, musically meaningful mutation, and replacement with a 50% generation gap. Fitness for the individual measures and phrases is derived from real-time feedback, which is provided by a human mentor while GenJam improvises to the accompaniment of a synthesized rhythm section. GenJam has been used for actual gigs under the billing Al Biles Virtual Quintet, which features the author on trumpet and GenJam on a variety of synthesized instruments, playing a repertoire of over 90 tunes in a variety of jazz, Latin, and new-age styles. Recent enhancements to GenJam include a pitch-to-MIDI capability that allows GenJam to listen to a human soloist, map his four-bar phrases to the GenJam genetic representation for phrases, apply selected mutation operators to these phrases, and play them back in real time as it trades fours or eights with a human soloist. In this way GenJam is truly interactive in performance, as well as during training. The lecture will feature a live demonstration of GenJam.
Scaling analysis for single-bubble cavitation
Authors: Simonenko Vadim A. , Karlykhanov Nikolay G. , Kovalenko Gennady V. , Nogin Vladimir N. , Moss William C.
Published: July 2002

There is a new interest to study caviation phenomena for gas-filled bubble in liquid basing on recent experimental and theoretical results on single-bubble sonoluminescence. Scaling analysis is applied to these phenomena. It allows a role of main control parameters to be clarified which have an influence on energy transfer to central gas-filled cavity and on energy dissipation in gas. The main parameters are linear dimensions, initial equilibrium pressure, initial temperature, rate and amplitude of pressure change. Of principle importance are convergent symmetry parameters and time-shape for external pressure. The most important are phenomena which provide maximum energy transfer to a central bubble, and to internal gas layers in the bubble. Factors decreasing efficiency of energy transfer are shown. The main factors are (1) compressibility of liquid caused by additional energy dissipation in layers adjacent to bubble; (2) early origin of shock wave near gas–liquid boundary. Theoretical estimations are confirmed by simulations calibrated on single bubble sonoluminescence. Criteria are shown to optimize gas compression in bubble. There are proposed prospective experiments to study large-scale effects in systems with external size of few meters and equilibrium pressure of several kilobars. [Work supported by the CRDF.]
Psychometric functions for two-transient dichotic stimuli
Authors: Petrosyan Agavni , Saberi Kourosh
Published: July 2002

To better understand the parameters that limit interaural-delay sensitivity in a precedence-effect task, psychometric functions were measured for the detection of an interaural time difference (ITD) in the second transient of a two-transient binaural stimulus. The stimuli were broadband 1-ms Gaussian pulses centered on the cosine phase of a 6-kHz carrier. Twenty-point psychometric functions were obtained using a 2IFC method of constant stimuli, with each point based on a minimum of 500 trials. Four functions were obtained for each observer at interclick intervals (ICI) of 3, 6, and 12 ms, in addition to a single-transient control condition. Proportion of correct responses were transformed to d′ units and linearly fitted with ln(d′)=ln β+υ ln(ΔITD), where ln β and υ are the parameters of the fit. The slope parameter υ was independent of ICI and remained near unity, discounting nonlinear transformations of the stimulus scale [J. P. Egan, J. Acoust. Soc. Am. 38, 1043–1049 (1965)]. However, ln β decreased with decreasing ICI, suggesting linear changes in either the variance or expected value of the perceived lateral position. Further experiments examined the contribution of each of these latter factors to changes in ln β. Implications for causes that underlie the precedence effect are discussed.
Effects of changes of the spectral masking slope on sound quality and clarity of music sounds in the normal and impaired ear
Authors: Laback Bernhard , Versfeld Niek , Deutsch Werner
Published: July 2002

Reduced frequency selectivity as occurs in the cochlear impaired ear has been shown to be a main factor for degraded speech perception [J. M. Festen and R. Plomp, J. Acoust. Soc. Am. 76, 652–662 (1983)]. It is also assumed to have negative effects on music perception. In this paper the hypothesis is tested that the loudness relations between spectral peaks and nonmasked lower-level components, which depend on the individual fre- quency selectivity, are important for (a) subjective sound quality (listening comfort) and (b) clarity, as measured in terms of detectability of altered notes in music excerpts. In order to test this hypothesis a signal processing algorithm has been utilized which enhances or suppresses the lower-level spectral components of a complex signal according to a masking function. Processed signals have been presented to normal-hearing and cochlear-impaired subjects. Results revealed that subjects with reduced frequency selectivity—as measured with psychoacoustical tuning curves—tend to prefer music signals with enhanced lower-level components. In the clarity experiment, results obtained with hearing-impaired subjects show improved detectability with suppression of the lower-level components (increase of spectral contrasts). [Work supported by Austrian Academy of Sciences.]
Calibration of sound quality recording and playback systems
Authors: Ladegaard Poul
Published: July 2002

In sound quality, a head and torso simulator (HATS) plays as important a role as the recording media. Used with playback of the signals through headphones, it allows the most accurate substitute for actually having the listener in the live situation. The human perception of sounds is very sensitive to changes in sound level, frequency response, and directional information. The value of a subjective sound quality evaluation is directly dependent on how well these parameters are maintained correctly. The paper describes the design methods and goals for a good HATS. Also the requirements for choice of headphones is discussed. In the complete recording/playback process, there is a need for some carefully selected frequency equalizations; these will be treated in some detail. Special attention will be given to the level calibration of the entire system. Here, the CIC check facility comes in as a very attractive and relevant tool. Finally, the summary will discuss the few limitations of the entire recording/playback system. Hints on how to overcome these will be given.
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M EAP: An environmentally sensitive adaptive fluctuation-based processing algorithm that exploits amplitude and phase
Authors: Wagstaff Ronald A. , Mobbs Jackson A.
Published: July 2002

Signals that propagate from submerged sources to deep receivers in the ocean generally interact less with the fluctuation generation mechanisms near the sea surface than do clutter signals and noise which originate near the surface. As a result, signals from submerged sources generally have smaller fluctuations than clutter signals and noise. The order dependence in the amplitudes of fluctuations has been used to devise an environmentally adaptive signal processing algorithm that provides preferential gains for signals having smaller fluctuation amplitudes than those of clutter and noise [R. A. Wagstaff and J. A. Mobbs, J. Acoust. Soc. Am. 101, 3027 (1997)]. Gains include increases in signal-to-noise ratio, clutter suppression, and unalerted automatic detection. Similar gains can be achieved by exploiting the fluctuations in the phases of the acoustic pressures in the same manner that the order dependence was exploited. By replacing the order dependence with phase dependence, a similar algorithm has been devised that is sensitive to both amplitude and phase fluctuations and still adapts to the input data. The resulting algorithm, designated the AWSUM environmentally adaptive phase (EAP) is described, and results from measured data are presented. [Work supported by ONR and NRL.]
Array beamforming in long-range deep-water environments
Authors: Gorodetskaya Elena Yu. , Malekhanov Alexander I. , Sazontov Alexander G. , Vdovicheva Nadezhda K.
Published: July 2002

Realistic estimations of the deep-water acoustic coherence effects on the array gain for linear and quadratic beamformers, optimal ones included, were obtained for the North-West Pacific environments. An advanced technique was developed to calculate the signal coherence under the basic assumption that the long-range acoustic fluctuations are caused by internal waves in the summer channel or surface wind waves in the winter channel. Simulations were carried out both for horizontal and vertical arrays for the frequency of 250 Hz and ranges 500–1000 km. The following effects were shown to be the most essential points: (i) angular displacement and degradation of the plane-wave beampattern; (ii) large-array gain loss; (iii) coherence-induced gain ‘‘gap’’ between the optimal quadratic and linear beamformers; and (iv) gain dependence on the ambient modal noise. The optimal quadratic beamformer was shown to reduce the gain loss at a cost of increased processor complexity: The number of partial weight-sum channels is equal to the number of the largest signal eigenvalues. In some environments, a proper performance/complexity was realized using suboptimal beamformers which are, therefore, of particular interest for large-array applications. [Work supported by RFBR.]
Bioacoustics measurement system control and coordination using LABVIEW
Authors: Finneran James J. , Hastings Mardi C.
Published: July 2002

Although LABVIEW is well known for its ability to generate custom applications with graphical user interfaces, its main strength lies in its compatibility with a wide variety of third-party hardware and software. LABVIEW instrument drivers exist for hundreds of devices from manufacturers such as Hewlett–Packard, Tektronix, Keithley, B&K, Wavetek, and Tucker–Davis. These instrument drivers and its support for OLE, DDE, and the GPIB protocol enable LABVIEW to control complex measurement systems containing a wide variety of devices. Data analysis is facilitated by built-in functions for digital filtering, signal processing, and many common statistical operations. This paper discusses some of the basic features of LABVIEW as well as a specific application: the use of LABVIEW to control an integrated testing environment developed to measure the acoustically-induced motions of the peripheral auditory organs in bony fishes using a noninvasive ultrasonic measurement system. In this application, a personal computer running LABVIEW was used to control and coordinate the measurement system, which included a DSP board, motorized positioning system, and video capture board. The PC also contained a GPIB interface, which was used to interface LABVIEW with a spectrum analyzer, lock-in amplifier, oscilloscope, digital multimeter, and function generator. [Work supported by ONR.]
Investigation of low frequency aircraft noise near airports
Authors: Lind Stephen , Pearsons Karl
Published: July 2002

Noise levels due to aircraft departures were measured at four locations near Minneapolis–Saint Paul International Airport and at seven locations near Los Angeles International Airport. A-weighted overall levels and one-third octave band levels between 25 and 80 Hz were obtained. Levels for 46 aircraft were analyzed for Minneapolis and 122 for Los Angeles. A linear regression was performed on the low-frequency levels versus the A-weighted levels for the locations to the sidelines of the active runways. The relationship between low-frequency noise and A-weighted sound pressure level for different distances was applied to A-weighted levels obtained from INM to estimate the low-frequency noise levels from a proposed runway. Estimates were made regarding which parts of the community would experience perceptible vibrations.
Comparison of pitch reset characteristics between children’s filler syllable and starter syllable productions
Authors: Seymour P. J. , Speer Shari R. , Fey Marc E. , Frome Loeb Diane
Published: July 2002

Children’s filler syllables may assist in maintaining rhythmic envelopes and intonational phrasing, and may be markers of potential or actual morphosyntactic information. Therefore, they should exhibit pitch characteristics indicating coherence with other constituents in the same intonational phrase. They contrast with starter syllables, which serve more pragmatic functions such as discourse place holders. An acoustical analysis of pitch reset is presented which distinguishes between filler and starter productions. Pitch reset was evaluated through two measures: the difference in intensity (decibels) between syllable initiation and syllable termination, and boundary duration (milliseconds) from the offset of the targeted syllable to the onset of the next syllable or constituent. Results demonstrated that fillers and starters could be differentiated using pitch reset measures. Typically, fillers did not exhibit pitch reset, described here as a boundary duration less than 200 ms and intensity difference scores ranging from −15 to +17 dB. Starters, however, did typically exhibit pitch reset, described here as a boundary duration greater than 200 ms and intensity difference scores ranging from 0 to +17 dB. This pilot investigation suggests that fillers exhibit similar pitch reset acoustical characteristics to other syntactic constituents in the intonational phrase in which they are located. [Work supported by NIH.]
Native language determines the parsing of nonlinguistic rhythmic stimuli
Authors: Kusumoto Kiyomi , Moreton Elliott
Published: July 2002

Given a rhythmic sound stimulus, the hearer automatically parses it into recurrent units. Researchers since Woodrow [Arch. Psych. 14, 1–66 (1909)] have consistently found that stimulus elements differing in duration are parsed iambically, while those differing in intensity are parsed trochaically. In an extensive typological survey, Hayes [Metrical Stress Theory (1995)] observes that no language has quantity-insensitive iambic feet, and suggests that the nonlinguistic parsing tendencies may be at the root of this language universal (the ‘‘iambic-trochaic law’’). However, the relevant nonlinguistic parsing experiments were done with native English speakers. We compared parsing behavior in native speakers of English and in two dialects of Japanese. Our findings suggest that native language (specifically, the structure of the minimal intonational phrase) determines parsing preference, not the other way around. The lack of quantity-insensitive iambs must have another source.
Word timing in a counting task and perceived severity of impairment in spasmodicdysphonia
Authors: Kumada Masanobu , Bell-Berti Fredericka , Kobayashi Takeo , Makiyama Kiyoshi , Niimi Seiji
Published: July 2002

Since the mora is the phonologically isochronic unit in Japanese, the proportion of impaired morae may be used as an indicator of the temporal impairment of speech. In spasmodicdysphonia (SD), symptoms occur sporadically and at three levels: (1) voice quality, (2) phonological, and (3) fluency. In previous work [Kumada et al., Jpn. J. Logoped. Phoniatr. 38, 176–181 (1997)], the ‘‘Mora Method’’ was proposed to evaluate the severity of SD in Japanese-speaking patients, with the severity represented by the proportion of impaired morae in a 25-morae sentence. Since counting aloud is a fairly rhythmic task, this paper studies using a proportion of impaired syllables in a counting task to characterize the severity of impairment in English-peaking SD patients. In addition to perceptual syllable-by-syllable judgments, the paper also examines timing relations of number-to-number and syllable-to-syllable intervals for comparison with syllable-impairment and overall-quality rating scale judgments. These comparisons should help establish the usefulness of perceptual syllable-by-syllable judgments to represent the severity of fluency impairment in English-speaking SD patients. [Work supported by NIH DC-00865 to Haskins Laboratories and by St. John’s University.]
Semicoherent technique to improve sonar processor performance for signals with small fluctuations
Authors: Wagstaff Ronald A. , Mobbs Jackson
Published: July 2002

A signal processing algorithm that utilizes coherent addition of the acoustic pressures usually provides greater noise suppression with a corresponding increase in signal-to-noise ratio (SNR) than one that uses incoherent addition. Furthermore, fluctuation based processing (FBP) algorithms that are designed to operate on signals from submerged sources (i.e., small fluctuations) generally utilize incoherent averaging techniques to provide various enhancements over conventional algorithms that are also incoherent, including greater SNR, increased resolution, clutter suppression/elimination, and unalerted auto-detection/classification (submerged/not-submerged). An algorithm that combines the desirable features of the coherent approach and the incoherent FBP approach could possess desirable features of both types of algorithms and be very useful for enhancing the processor’s performance. Such an algorithm has been devised. It operates on the combined amplitude and phase fluctuations in the acoustic pressures in a semicoherent manner to substantially improve the processor’s performance. The algorithm will be defined, and results from measured undersea data will be presented to illustrate the gains that are achieved by this new algorithm. [Work supported by ONR and NRL.]
AWSUM III434: A coherent fluctuation based processor for enhanced resolution and unalerted autodetection
Authors: Wagstaff Ronald A. , George Jacob
Published: July 2002

A new coherent fluctuation based processor for enhancing spatial resolution, suppression of clutter, and unalerted autodetection, designated AWSUM III434, is described and results are presented. The processor is a combination of the Wagstaff’s Integration Silencing Processor (WISPR) III [R. A. Wagstaff and J. George, SPIE Aerospace/Defense Sensing and Controls ’96 Symposium, Targets and Background: Characterizations and Representation II Conference, Proc. SPIE 2751, 132–141 (1996)] and the Advanced WISPR Summation (AWSUM) processor [R. A. Wagstaff, IEEE J. Ocean. Eng. 22, 110–118 (1997)]. While WISPR III achieves signal-to-noise ratio (SNR) gains of about 14 dB, AWSUM III434 achieves gains of about 24 dB. In addition, the spatial resolution of AWSUM III434 is significantly enhanced, and the unaltered autodetection/identification capability for signals from submerged sources is measurably increased, e.g., by 10 dB. [Work supported by ONR and NRL.]
Reflection coefficient of marine sediment covered with liquid pollutants
Authors: Harms Henning , Matuschek Rainer , Mellert Volker
Published: July 2002

Acoustic sounding of sediment properties is usually carried out with waves at more or less normal incidence. This method, however, fails to detect thin layers (d≪λ) of undissolved fluid covering the sea-bottom due to the small difference in impedance compared to water. But the spherical wave reflection coefficient is strongly affected at grazing incidence and allows for the detection of these layers. Laboratory measurements in model scale as well as model calculations are carried out in order to determine the capabilities of the new measuring method. Experiments were done in a water tank with a hydrophone as a spherical broadband sound source. Various liquid chemicals of density greater than water are poured on the sand in small amounts, forming layers of less than 3-mm thickness. Measured excess attenuation of the pure sediment is in very good agreement with simulations carried out with a fast field program (FFLAGS) that incorporates Biot theory [S. Tooms et al., J. Acoust. Soc. Am. 93, 173–181 (1993)]. The excess attenuation of the sediment coated by a thin layer differs significantly. In particular, the interference pattern is broadened and shifted toward lower frequencies. This behavior is explainable by FFLAGS as well. [Work supported by BMBF.]
The low-frequency radiation and scattering of sound from bubbly mixtures near the sea surface
Authors: Carey William M. , Roy Ronald A.
Published: July 2002

Microbubble plumes are produced when waves break and are convected to depth. What role these microbubble plumes have in the production of sound and the scattering of sound near the sea surface from the low- (20-Hz) to mid- (2-kHz) frequency range? Ocean ambient noise shows a dramatic increase in midfrequency levels when wave breaking occurs. Measurements of scattering from the sea surface have a different characteristic than expected by Bragg scattering from gravity waves, i.e., a large zero Doppler component. If microbubble clouds and plumes with void fractions greater than 0.0001 act as collective resonant oscillators, then noise can be produced and scattering can occur with little Doppler shift but ample spread. This hypothesis was based on the theory that the mixture properties determine the radiation and scattering from such a compact region. Experimental results show that the far field radiation of sound from a compact region can be described by monopole volume pulsation beneath a pressure release surface with the natural frequency described by a modified Minneart formula. Scattering measurements from submerged bubble clouds show a significant low frequency scattering. Experimental evidence and theoretical formulations are consistent with collective phenomenon. [Work supported by ONR.]
Acoustic scattering by a three-dimensional elastic obstacle near a rough fluid–fluid interface
Authors: Lim Raymond , Williams Kevin L. , Thorsos Eric I.
Published: July 2002

The ensemble-averaged coherent and incoherent intensities are formulated for acoustic scattering by a smooth, bounded, elastic obstacle under the interface between two immiscible fluids with small-scale random roughness imposed. The formulation consists of combining Rayleigh-Rice perturbation theory for modeling propagation through the rough surface with a transition matrix solution for scattering by the obstacle near a planar surface. Results are applied to a spherical steel shell buried in a rough sediment bottom modeled with fluid parameters. It is demonstrated that the average incoherent field backscattered by the shell illuminated with shallow-grazing-angle acoustic sources can be well enhanced over field predictions based on scattering models where environmental surfaces are planar. Interestingly, the coherent intensity is also enhanced over flat interface predictions although not to the degree of the incoherent intensity. Implications to the acoustic detection and classification of buried obstacles are discussed. [Work supported by ONR.]
Scattering from fluid loaded targets in proximity to a sediment interface: Numerical results
Authors: Bishop Garner C. , Smith Judy
Published: July 2002

A null-field T-matrix formalism developed for plane-wave scattering from a fluid-loaded elastic spherical shell in proximity to a rough fluid elastic interface [J. Acoust. Soc. Am. 101, 767–788 (1997)] is extended to include scattering from sound-hard and -soft spherical targets and a sound-hard finite cylinder with hemispherical end caps and, for a planar interface, sound-hard, sound-soft, and fluid-saturated poroelastic sediments. A variety of numerical results are obtained that demonstrate some of the effects of target and sediment parameters on target–boundary acoustic coupling and target strength. Then, for small amplitude surface roughness, a perturbation formalism is used to indicate some of the effects of interface roughness.
In-situ acousto-optical imaging of zooplankton with the OASIS system
Authors: Jaffe Jules S. , Ohman Mark D. , De Robertis Alex
Published: July 2002

A new instrument has recently been developed: OASIS (optical-acoustical submersible imaging system), for recording in-situ acoustic target strengths (TS) of crustacean zooplankton with concurrent optical imaging of the animals. The system consists of a three-dimensional acoustic imaging system (Fish TV) and a sensitive optical CCD camera with a red-filtered strobe. The sonar triggers the acquisition of an optical image when it detects the presence of a significant target in the precise location where the camera and strobe are co-registered. Acoustic TS can then be related to the optical image which permits the identification of the animal and its 3-D orientation. The system was deployed in Saanich Inlet, BC, Canada in the summers of ’86 and ’87. Target strengths of many acoustic reflectors were recorded in parallel with the optical images triggered by the presence of an animal in the correct location of the sonar system. Inspection of the optical images revealed that the primary zooplankton taxa at the site were euphausiids [esp. Euphausia pacifica] and [gammarid] amphipods [esp. Cyphocaris challengeri] and permitted an exact correlation of TS and taxa. Extrapolation of this information to many other acoustic targets, imaged by the Fish TV system will allow more precise interpretation of both abundance and behavior.
Broadband bottom scattering, loss, and reverberation measurements near Elba Island
Authors: Holland Charles W.
Published: July 2002

The prediction of low- to midfrequency shallow-water reverberation is still in its infancy. This is due, in large part, to the unpredictability of the bottom-scattering kernel, and particularly, its dependence upon frequency. The bottom-scattering kernel is difficult to measure directly and even more problematic to extract from the reverberation. An experiment was conducted in a complex shallow-water area to test novel coherent and incoherent direct-path bottom-scatter measurement techniques (400–4000 Hz). Advantages and disadvantages of each technique are discussed. Analyses of the bottom-scatter data in conjunction with collocated bottom loss and high-resolution seismic data shed light on the underlying mechanisms (e.g., interface roughness, sub-bottom volume inhomogeneities, or basement roughness) that give rise to the scattering. It is hypothesized that the frequency dependence of the scattering kernel can be linked to the dominant scattering mechanism.
Wall pressure and acoustic modeling from boundary-layer bursts and sweeps
Authors: Witting James M.
Published: July 2002

Explicit treatment of discrete, transitory, momentum-transporting features in boundary layers (bursts and sweeps) can generate acoustic models [e.g., J. M. Witting, ‘‘A spectral model of pressure fluctuations at a rigid wall bounding an incompressible fluid, based on turbulent structures in the boundary layer,’’ Noise Control Eng. J. 26, 28–43 (1986)]. This presentation addresses the following topics: (1) the relationships between the properties of the microscopic structures (such as their sizes, strengths, and durations) and the details of the wall-pressure spectrum; (2) estimating actual microscopic properties from measured data, either directly or from empirical models that have been compared to measured data; (3) extensions to more complex geometries; and (4) the role of the boundary-layer structures as direct sources of sound in the fluid.
Stochastic linear regression analysis of speech production data
Authors: Kollia H. Betty , Jorgenson Jay
Published: July 2002

Dynamic models in speech production have been traditionally based on linear regression analysis of articulatory data. The purpose of this work is to introduce a stochastic calculus methodology to the analysis of such data in speech production models. The issue of variability encountered in the analysis and description of articulatory movements during speech may be addressed with the implementation of a stochastic term, thus placing the variability in a controlled probabilistic framework. Upper lip, lower lip, jaw, and velum movements tracked optoelectronically at Haskins Laboratories [Kollia et al. J. Acoust. Soc. Am. 98, 1313–1327 (1995)] during production of a test utterance are described in this manner. The authors believe that this algorithm has wide applicability since it yields confidence interval rather than point value estimates for kinematic data description. [Work supported by NSF.]
Application of head-related transfer functions for binaural synthesis
Authors: Hammershoei Dorte , Sandvad Jesper , Moeller Henrik
Published: July 2002

Binaural synthesis offers a method for creating a truly immersive three-dimensional auditory environment. The sound output is produced by convolving a sound input with sets of head-related transfer functions (HRTFs). The result is a set of two signals typically reproduced by means of headphones, and the technique is therefore well suited for systems with limited hardware for sound reproduction, such as most multimedia systems. In the present paper, HRTFs are presented in the time and frequency domains, and are commented upon in relation to their application for binaural synthesis using digital signal processing. Results obtained from experiments conducted at the Acoustics Laboratory at Aalborg University in Denmark are reviewed, giving hints for the selection of filter lengths, update rate, and spatial resolution for dynamic environments.
Language, context, and speaker effects in the identification and discrimination of English /r/ and /l/ by Japanese and Korean listeners
Authors: Ingram John C. L. , Park See-Gyoon
Published: July 2002

Japanese and Korean listeners’ identification and discrimination of English /r/ and /l/ were compared using a common set of minimal pair stimuli. The effects of speakers (two native speakers of Australian English), position of the contrast within the word (word initial, initial consonant cluster, and medial positions), and listening task (forced choice identification versus oddball discrimination) were examined, with a view to assessing the relative importance of language-specific and language-independent factors operating at the acoustic–phonetic and phonological levels of signal processing in “foreign sound” speech perception. Both prior phonological learning and the relative acoustic discriminability of the items affected subjects’ performance on the identification test. Where both factors were engaged, phonological learning effects predominated over the effects of acoustic discriminability. The extent to which a speaker encoded critical acoustic cues for the /r–l/ distinction was found to affect /r–l/ identification. Dynamic spectral features known to be relevant for the /r–l/ contrast were effective in predicting (in a linear regression analysis) speaker-dependent differences in identification scores. Although the discrimination test may have been influenced by ceiling effects, the performance profiles on the identification and discrimination tests were quite different, indicating that the identification and discrimination tests imposed quite different task demands upon listeners and that phonological processing of the signal was more engaged by the former task.
Effect of overpressure on dissolution and cavitation of bubbles stabilized on a metal surface
Authors: Cleveland Robin O. , Bailey Michael R. , Crum Lawrence A. , Stonehill Mark A. , Williams James C. , McAteer James A.
Published: July 2002

Recent experimental evidence indicates that static overpressure dramatically reduces lithotripsy-induced cell damage or stone comminution [Delius, Ultrasound Med. Biol. 24, 611–617]. The hypothesis is that the damage and comminution are due to cavitation and that overpressure dissolves the small gas bubbles which act as cavitation nuclei. Delius observed, however, that the overpressure to protect cells (1 atm) was significantly lower than for stones (10 atm). In similar experiments cell lysis and pitting of aluminum foil as indicators of cavitation are used; the thresholds were 1 and 30 atm, respectively. In addition, the authors observed that pitting of foils increased for overpressures up to 20 atm. It is proposed that crevices in the foil stabilize cavitation nuclei whereas the bubbles dissolve in fluids. Foil damage increased because overpressure is small relative to the shock wave pressures that drive bubble expansion but is the dominant driving force at bubble collapse. Calculations using the Gilmore equation predict that overpressures up to 30 atm hasten and intensify cavitation collapses and over 60 atm eliminate cavitation, in qualitative agreement with our foil data. The calculated collapse time was confirmed experimentally by passive cavitation detection. If bubbles are stabilized in crevices in kidney stones, overpressure may provide a safer, more effective lithotripsy treatment. [Work supported by NIH-PO1-DK43881.]
Amplitude and period discrimination of haptic stimuli
Authors: Rinker Martha A. , Craig James C. , Bernstein Lynne E.
Published: July 2002

As part of a project to examine the ability of the hand to receive speech information, the present study examined subjects’ ability to discriminate finger movements along the dimensions of amplitude and period (movement duration). The movements consisted of single-cycle, sinewave movements and single-cycle, cosine movements presented to the index finger. Difference thresholds were collected using an adaptive, two-interval, temporal forced-choice procedure. Amplitudes from 6 to 19 mm were examined, and the difference thresholds ranged from 10% to 18%. The thresholds were unaffected by the period of the movement. Periods from 3000 to 111 ms (0.33–9 Hz) were examined, and thresholds ranged from 6% to 16%. The thresholds were unaffected by the amplitude of the movement. Further measurements in which period was varied in the amplitude discrimination task and amplitude was varied in the period discrimination task indicated that subjects were not using peak velocity as the basis for discrimination. These measurements were collected using a display specifically designed for the examination of haptic stimulation and capable of presenting controlled patterns of movement and vibration to the fingers.
Coherence functions of plane and spherical waves in a turbulent medium with the von Karman spectrum of medium inhomogeneities
Authors: Ostashev V. E. , Brähler B. , Mellert V. , Goedecke G. H.
Published: July 2002

This paper deals with line-of-sight sound propagation in a medium with the von Karman spectra of temperature and medium velocity fluctuations. The mean sound field, the coherence functions of plane and spherical waves and their coherence radii in such a medium are calculated analytically and numerically. It is found that the temperature and medium velocity contributions to these statistical moments of a sound field may differ significantly. The coherence functions of plane and spherical waves for the von Karman spectrum of medium inhomogeneities have been compared with those for the Kolmogorov and Gaussian spectra. The latter two spectra have been used widely in theories of sound propagation in random media. It is shown that, in limiting cases, the coherence functions calculated for the von Karman spectrum coincide with those calculated for the Kolmogorov and Gaussian spectra. This result supports the use of the Gaussian spectrum in theories of sound propagation in random media.
Effect of orientation on broadband acoustic scattering of Antarctic krill Euphausia superba: Implications for inverting zooplankton spectral acoustic signatures for angle of orientation
Authors: Martin Traykovski L. V. , O’Driscoll R. L. , McGehee D. E.
Published: July 2002

Acoustic scattering experiments involving simultaneous acquisition of broadband echoes and video footage from several Antarctic krill were carried out to determine the effect of animal orientation on echo spectral structure. A novel video analysis technique, applied to extract krill angle of orientation corresponding to each insonification, revealed that echo spectra from krill near broadside incidence relative to the incident acoustic wave exhibited widely spaced, deep nulls, whereas off-broadside echo spectra had a more erratic structure, with several closely spaced nulls of variable depth. The pattern of changes in echo spectra with orientation for the experimentally measured acoustic returns was very similar to theoretically predicted patterns based on a distorted wave Born approximation (DWBA) model. Information contained in the broadband echo spectra of the krill was exploited to invert the acoustic returns for angle of orientation by applying a newly developed Covariance Mean Variance Classification (CMVC) approach, using generic and animal-specific theoretical and empirical model spaces. The animal-specific empirical model space was best able to invert for angle of orientation. The CMVC inversion technique can be implemented using a generic empirical model space to determine angle of orientation based on broadband echoes from individual zooplankton in the field.
Ultrasonic tomographic imaging of temperature and flow fields in gases using air-coupled capacitance transducers
Authors: Wright William M. D. , Schindel David W. , Hutchins David A. , Carpenter Peter W. , Jansen Dion P.
Published: July 2002

A pair of air-coupled ultrasonic capacitance transducers with polished metal backplates have been used to image temperature and flow fields in gases using ultrasonic tomography. Using a filtered back-projection algorithm and a difference technique, cross-sectional images of spatially variant changes in ultrasonic attenuation and slowness caused by the presence of temperature and flow fields were reconstructed. Temperature fields were produced in air by a commercial soldering iron, and the subsequent images of slowness variations used to reconstruct the air temperature at various heights above the iron. When compared to measurements made with a thermocouple, the tomographically reconstructed temperatures were found to be accurate to within 5%. The technique was also able to resolve multiple heat sources within the scan area. Attenuation and velocity images were likewise produced for flow fields created by an air-jet from a 1-mm-diam nozzle, at both 90 and 45 degrees to the scanning plane. The fact that temperature and flow fields can be measured in a gas without the need to insert any measuring devices into the image region is an advantage that may have many useful applications.
Some lengthening factors in English speech combine additively at most rates
Authors: Cummins Fred
Published: July 2002

The known lengthening effects of phrase-final position and of contrastive emphasis have been predicted by Klatt to combine superadditively. In a new experiment, texts elicited at a wide range of speaking rates were measured and the separate and combined effects of these lengthening factors were found to combine approximately additively at all rates studied. The proportion of lengthening attributable to each factor was found to be relatively invariant except at the fastest speaking rates, where lengthening was eventually eliminated. The results support the interpretation of absolute speaking rate as an inessential variable for characterizing speech at a range of moderate rates.
Generation of partials due to nonlinear mixing in a stringed instrument
Authors: Conklin Harold A.
Published: July 2002

Nonlinear mixing appears to account for the production of “phantom partials” in piano tones. “Phantom partials” are those that appear at frequencies exactly harmonic to normal inharmonic string partials, and at frequencies equal to the sums of the frequencies of normal inharmonic partials. Nonlinear mixing can occur because tension varies during transverse vibration. This produces longitudinal string forces of phantom-partial frequency that appear at the soundboard bridge and are coupled to the soundboard. “Phantom partials” were found in piano tones, in the motion of a piano bridge, in the longitudinal vibrations of a monochord string, in the acoustical output of a soundboard coupled to a monochord string, and in the acoustical output of a guitar. Any plucked-string or struck-string instrument having appreciable acoustical response to longitudinal string forces could be expected to produce phantom partials. The relation in frequency between phantom partials and normal partials, which varies with inharmonicity, may play a part in differentiating the timbre of tones at the same fundamental frequency in pianos of different size and design.
One-channel time-reversal in chaotic cavities: Experimental results
Authors: Draeger Carsten , Aime Jean-Christian , Fink Mathias
Published: July 2002

Experiments are presented that show the feasibility of reconstructing a point source using acoustic time-reversal with a single transmitter/receiver. The propagation medium is a closed 2-D silicon cavity with chaotic ray dynamics and negligible absorption. Injection of a short pulse at one point yields a long signal at a second one; by reversing a part of this signal, we obtain a focus at the initial injection point. The characterization of the focus was observed by scanning with an optical interferometer and by measuring the signal at the focal spot. With circular converging wavefronts, the reconstructed focus was excellent (corresponding to an aperture of 360°), but not perfect. The increase in quality of the focus with growing length of the reversed signal is described by a statistical ray model. Despite the irreversibility in classical chaos (due to strong sensitivity to initial conditions), the underlying chaotic ray dynamics is useful in this case.
Coarticulation of tongue and jaw movements in speech
Authors: Gracco Vincent L. , Shiller Douglas M. , Ostry David J.
Published: July 2002

Coarticulatory patterns in speech movements arise from the interaction of neural control signals with mechanical and geometrical properties of vocal tract structures. By determining those aspects of the biomechanical system that are compensated for in neural signals, it can be learned what the nervous system ‘‘knows’’ abouts its own dynamics. Previous work has shown that coarticulatory patterns in jaw movement may arise as a consequence of muscle properties and dynamics rather than characteristics of the neural code [Ostry, Gribble, and Gracco, J. Neurosci. (1996)]. This finding suggests that the nervous system may take limited account of orofacial dynamics in planning speech movements. However, in the case of interarticulator coarticulation, mechanical interaction among articulators may necessitate a more complex pattern of control. As a first step in assessing the characteristics of control signals that underlie interarticulator patterning, kinematic patterns of coarticulation in the tongue and jaw are reported on. Patterns of individual articulator motion as well as interarticulator spatial and temporal relationships will be described. [Research supported by National Institute of Deafness and Other Communication Disorders Grant No. DC-00594, NSERC (Canada), and FCAR (Quebec).]