bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-frequency volume scatter and accompanying bioacoustic measurements in the Gulf of Alaska
Authors: Vaccaro Mark J. , Monti Joseph M. , Brooks Al
Published: October 2005

Volume scattering from 200 to 1500 Hz was measured during the Gulf of Alaska surface scatter and air/sea interaction experiment occurring in February 1992. Scattering strength as a function of frequency and depth was measured and layer strength and column strength were calculated using a vertically bistatic measurement technique developed by Stockhausen and Figoli [SACLANT ASW Research Center Technical Report No. 225, 15 May 1973]. These measurements were accompanied by concurrent measurements of size/depth distributions of the fish population present using a dual beam echosounder system. Fish distributions were used to predict layer and column strength by employing the NUWC Interval Column Strength Model developed by Saenger etal. [Naval Underwater Systems Center Technical Report No. 9001 (31 December 1991)]. Comparisons of the measured and predicted results show that low-frequency scattering resonances may be related to biologics.
Modeling low-frequency volume reverberation from fish for the February–March 1992 Gulf of Alaska surface scatter experiment
Authors: Nero Redwood W.
Published: October 2005

Pelagic fish contribute to the overall level of reverberation in the near-surface ocean. At low sea states, biological reverberation can be greater than low grazing angle surface scattering and can impact the success of surface scattering experiments. This impact has been shown to occur both by model estimates of biological volume reverberation and direct measurements. Estimates of volume reverberation for the Gulf of Alaska during February–March were made using a model of swimbladder resonance applied to data on fish size, abundance, school characteristics, and vertical migratory behavior. The model reproduces features of low-frequency scattering, a characteristic resonant frequency for fish of different type, size, and depth, using parameters that influence swimbladder size and gas density. Knowledge of fish was derived from bioacoustic measurements made using fisheries sonar and information obtained from fisheries agencies. Results are compared with several direct measurements of near-surface scattering at low frequency and show that fish can impact surface scattering experiments. [Work supported by SPAWAR and ONR.]
Gulf of Alaska air-deployed SUS surface reverberation measurements
Authors: Bedford Nancy R. , Stotts Steven A. , Mitchell Stephen K.
Published: October 2005

During the February/March 1992 Gulf of Alaska surface scatter and air–sea interaction experiment, air-deployed explosive charges (SUS) and sonobuoys were used to obtain surface scattering and reverberation data during three flights. At each of the surface scattering measurements sites, sonobuoys of different acoustic sensitivities were dropped within a 200-m circle to cover the wide dynamic range of the received SUS signals. SUS charges were then dropped at the location of these sonobuoys, providing monostatic reverberation measurements. On two of the flights, separated by 3 days in time, environmental measurements made from surface ships involved in the experiment indicates similar wind speeds. However, the measurement time periods were preceded by very high winds on one day and lower winds on the other day. Reverberation levels and surface scattering strength are addressed using the data from these two flights. [Work supported by the AEAS Program of the Office of Naval Research.]
Environmental forcing and water column properties as related to acoustic measurements in the Gulf of Alaska
Authors: Hanson Jeffrey L. , White Larry H. , D’Anna Michele E.
Published: October 2005

During the February–March 1992 Gulf of Alaska surface scatter and air–sea interaction experiment a series of detailed air–sea boundary zone measurements were closely coordinated with numerous acoustic scatter and reverberation experiments. A primary scientific objective was to evaluate the influence of various physical features of the ocean environment on subsurface bubbles and near-surface backscatter. The background meteorology, wind history, directional wave field, and mixed layer variability were carefully measured. The results allowed estimation of other air–sea boundary features including wind stress, heat flux, and surface buoyancy flux. A wide variety of surface weather conditions were experienced, including two events with winds ≥18 m/s and peak significant wave heights of approximately 5 m. Air temperatures mostly remained 1–3 °C cooler than the ocean surface and calculations show the average daily heat flux was negative (upwards). These unstable atmospheric conditions, coupled with a notably deep mixed layer extending to ≥100 m, resulted in an ideal environment for exceptionally deep penetration of subsurface bubbles.
Predicted surface zone scattering from measured bubble clouds in the Gulf of Alaska
Authors: Vagle Svein , Farmer David M. , Henyey Frank S.
Published: October 2005

Using previously described techniques, the tenuous bubble cloud field was measured during the 1992 Gulf of Alaska reverberation experimental program. These measurements are used to predict the low-frequency reverberation, which was simultaneously measured nearby. The predictions show a great deal of variability, consistent with the reverberation measurements. Most often the predictions are considerably less than the average scattering strength, but one measurement was obtained during stormy conditions, that, when averaged with all the small values obtained during stormy conditions, still exceeds the phenomenological Ogden–Erskine formula. The conclusion from this work is that there is probably adequate scattering from the tenuous clouds to explain the reverberation measurements, but that the more deterministic comparisons of planned experiments are required. [Work supported by ONR.]
Development of a female voice for a concatenative synthesis text-to-speech system
Authors: Syrdal Ann K.
Published: October 2005

In response to telecommunication customer demand, a female voice was developed for a concatenative synthesis text-to-speech system. The voice was initially developed for a 1000-element diphone concatenation system [J. P. Olive and M. Y. Liberman, J. Acoust. Soc. Am. Suppl. 1 78, S6 (1985)] and then extended to a 2500-element acoustic inventory with units of variable size [J. P. Olive, Workshop on Speech Synthesis, Autrans, France, ESCA, 25–30 (1990)], both originally developed with male voices. In these synthesis-by-rule systems, segments used for synthesis are obtained from natural speech and concatenated to synthesize any English utterance. Difficulties for a female voice are (1) better performance of analysis and synthesis algorithms for male than for female speech, and (2) telephone bandwidth constraints, which filter out more phonetically relevant high-frequency acoustic information for female speakers than for males. Intelligibility testing was used to identify and replace problematic acoustic elements, and the introduction of new analysis and synthesis techniques resulted in improved intelligibility and quality.
Synthesis of names using careful speech style
Authors: Bladon Anthony
Published: October 2005

A high-quality formant synthesizer, optimized for the transfer characteristics of the telephone network, has been implemented to provide real-time text-to-speech performance on a fraction of a TMS 320C25 processor. A version optimized for the pronunciation of American names (‘‘Name-to-Speech’’) has been created which incorporates phonetic level changes characteristic of acarefulspeech style. Examples of the careful speech adaptations include a brief inter-word silence, a wider use of vowel-onset glottal stop, the restoration of plosive releases and of various elisions, the strengthening of some weak vowels, stress changes, reductions in formant coarticulation, and various segmental acoustic adjustments such as fricative gain. These careful speech features were determined after observing corresponding behaviors in an initial study of the way telephone users speak their own names (for the purpose of annotating their voice mail). In a follow-up study, users showed an overwhelming preference for the pronunciation of their own name in the careful style of synthesis, rather than in a fluent style typical of synthesized running text.
Vein diagram: A simplified version of time-frequency display for acoustic structure response
Authors: Yen Nai-chyuan , Dragonette Louis R. , Ross Christopher A.
Published: October 2005

The application of time and frequency displays to depict the wave packet components of the acoustic response from a submerged object is a useful analysis tool in the study of scattering phenomena. However, such representations are generally obtained from processing algorithms that rely on some controlled parameters (special windows or shading kernals), which may not provide correct interpretations of scattering physics. The technique considered here places emphasis on the correlation property of the structure’s response and expresses it in terms of the conventional ambiguity function. The vein diagram sums up the reduced highlights from a 2-D Fourier transform of this ambiguity function. To focus on the essential wave packet components, the technique allows flexibility in the choice of windows and an adjustable feature selection threshold. Because the vein diagram is derived from the energy distribution of the structure’s response, it provides a more concise and meaningful association with the physics of wave packet formation. Implementation of our processing technique in a graphics working station (IRIS) will be described, and its relationship to other well-known processing methods such as the Wigner distribution function, Gabor transform, and wavelet decomposition will be described.
E
6 diffraction catastrophe in light scattered near the rainbow region of an acoustically levitated spheroidal water drop
Authors: Kaduchak Gregory , Marston Philip L.
Published: October 2005

Light scattering by oblate acoustically levitated drops of water gives a method of exploring a variety of weak foci known as diffraction catastrophes. The present research concerns laser light observations of a formerly unidentified caustic exhibited by white light scattering of a highly oblate drop [H. J. Simpson and P. L. Marston, Appl. Opt. 30, 3468–3473 (1991), plate 16]. The scattering pattern exhibits a rich structure that changes rapidly over a narrow range of drop aspect ratio D/H. The caustic patterns are those predicted of an E6 catastrophe in the range of D/H explored [J. F. Nye, Proc. R. Soc. London (accepted for publication)]. The focal section of the E6 is observed though the E6 has a control space of five dimensions while the experiment explores only three dimensions. The observations illustrate how special symmetrics and geometries can constrain the caustics produced in far-field scattering from a penetrable spheroid. [Work support by ONR.]
A study of the premonitions of chaos
Authors: Vaidya P. G. , Doughty Tim , He Rong
Published: October 2005

There are two unrelated developments that form the basis for research. One of these is the work by Weisenfeld [J. Stat. Phys. (1985)]. He showed that a small amount of noise would have a profound effect on the output spectrum of a nonlinear system undergoing bifurcations. These modifications thus serve as the precursors of these bifurcations. The second is the development of the trans-spectral coherence technique for the analysis of nonlinear signals, developed by Vaidya and Anderson [J. Acoust. Soc. Am. 89, 2370–2378 (1991)]. This technique has been used to educe small signals out of noise and to show inherent structure in chaos. These two ideas are put together to show that such precursors of chaos could be detected, even earlier, using the trans-spectral coherence technique. Such detection, would have a wide range of applications, from cardiology to oceanography.
On the applicability of VQ codebooks to connected digit recognition
Authors: Rabiner Lawrence R. , Wilpon Jay G. , Chou Wu , Juang Biing-Hwang
Published: October 2005

Connected digit recognition is a problem that has received a lot of attention over the past several years because of its importance in providing speech recognition services (e.g., catalog ordering, credit card entry, all digit dialing of telephone numbers, etc.). Although a number of systems have been described that provide very high string accuracy on a standard database of connected digits (i.e., the TI database), most of these systems require a great deal of computation to provide high performance. Most recently, there has been a renewed interest in connected digit recognition systems based on discrete density models using VQ codebooks (e.g., the work of Normandin and colleagues at CRIM in Montreal) where the computation is significantly lower than that required for continuous density models, and the robustness to variations in talkers, background, microphones, etc., has the potential to be high. In this study, the effect of multiple codebooks, multiple models, and codebook weighting on the performance of a standard hidden Markov model recognizer using the TI connected digits database is examined. It is shown that a single codebook can provide high string recognition accuracy, and that multiple codebooks provide accuracy comparable to that of continuous density models.
Robust speech recognition in a multimedia teleconferencing environment
Authors: Che Chi Wei , Rahim Mazin , Flanagan James
Published: October 2005

In many speech recognition systems, inconsistency between the training and testing conditions (i.e., effects related to noise, reverberation, microphone type, and characteristics, etc.) typically results in an unacceptable degradation in the recognition accuracy. For example, an experiment conducted in our multimedia laboratory demonstrated that the word accuracy of the Sphinx recognition system degrades from 96% to 71% when the close-talking Senheiser microphone (CLS) at 5 in., used in training, is replaced by a hands-free wideband line array (ARR) at 10 ft. This paper describes a neural network architecture for improving the robustness of speech recognizers in a multimedia teleconferencing environment. A multi-layer perception (MLP) is trained to map cepstral parameters from the ARR to the CLS. An experiment conducted on three male speakers using the ARR shows that a MLP with a hidden layer of eight nodes improves the recognition accuracy of the Sphinx system from 71% to 90%. Furthermore, cross-speaker validation (i.e., training on one speaker and testing on others) provided an 84% word accuracy. The encouraging result implies that the neural network ‘‘learns’’ the room reverberation characteristics and performs the environment adaptation largely irrespective of the speaker or the spoken text.
Speaker adaptation for segment-based isolated-word recognition
Authors: Yamazaki Yasushi , Sanada Toru , Kimura Shinta
Published: October 2005

Our speaker-dependent recognition method (SD) requires 184 training words. To reduce this number, three types of speaker adaptation were studied. Using smaller training words, they adapt segment spectrum templates to a new speaker. The first, SA1, learns a transfer function for converting templates for an existing speaker to those for a new speaker. The second, SA2, is based on the idea that the system uses templates for multiple speakers whose voices resemble to that of the new speaker. The third, SA3, adds templates extracted from training words to speaker-independent templates for many speakers. For reference, a speaker-independent method (SI) and a method using other speaker’s templates (SO) were evaluated. All the methods were tested using a hard-to-recognize 100-word vocabulary by five speakers. The average recognition rates of SD, SI, and SO are 95.6%, 92.8%, and 85.3%. Those of SA1, SA2, and SA3 with 18 training words are 88.6%, 91.6%, and 93.8%. The performance of speaker adaptation from other speakers’ templates, such as SA1 and SA2, is worse than that of SI, and the adaptation from speaker-independent templates (SA3) is promising. In an evaluation using some ordinary 100-word vocabularies, the average recognition rates of SD and SA3 are 98.4% and 98.0%.
Acoustical power flow from a room into flexible walls
Authors: Pan Jie
Published: October 2005

The reverberation time of a room is related to the ratio between the power flow into the walls and the total sound energy in the room. If the walls of the room in constructed by flexible structures, this power flow can be determined by the interaction between the sound waves in the room and structural waves in the walls. In this paper, the power flow from the sound field into one flexible wall is calculated in the whole frequency range. The characteristics of the power flow is demonstrated and its relation with the reverberation time in the room is discussed. The sound absorption characteristics of the modally reactive and locally reactive boundaries are also compared.
Liquid-filled spherical reflectors: Analysis of glory ray amplitudes
Authors: Marston P. L. , Sun N. H.
Published: October 2005

Thin spherical shells filled with a liquid having a low speed of sound ci are known to have enhanced high-frequency backscattering. It is generally recognized that when the acoustic refractive index N=c/ci is between √2 and 2, the enhancement is associated with a two-chord off-axis backscattered ray. A geometrical analysis of the amplitude diverges since the Gaussian curvature of the outgoing wave front vanishes. In the present research, a physical-optics analysis of glory ray scattering [P. L. Marston and D. S. Langley, J. Acoust. Soc. Am. 73, 1464–1475 (1983)] was applied to the ray of interest. Attention was limited to neutrally buoyant spheres and shell effects were neglected in both the analysis and the partial-wave series (PWS) calculations. The form function contribution is proportional to (ka)1/2, where a is the sphere radius and k=ω/c. For large ka, the analysis gives the major contribution to the PWS calculations except for N near √2 and 2. In this range for N the contribution has a concise analytical approximation that depends on the ray impact parameter b = a(N/2)√4−N2. [Work supported by ONR.] a)Present address: EXP Group, Inc., 44063 Fremont Blvd., Fremont, CA 94538.
Liquid-filled spherical reflectors: The exceptional case of refractive index approaching two
Authors: Marston P. L. , Sun N. H.
Published: October 2005

Thin spherical shells filled with a liquid having a low speed of sound ci are known to have enhanced high-frequency backscattering that generally increases with ka and depends on the acoustics refractive index N=c/ci. Here, a is the radius of the sphere. For N between √2 and 2 there is a backscattered two-chord ray with a nonzero impact parameter b. A physical-optics analysis [P. L. Marston and D. S. Langley, J. Acoust. Soc. Am. 73, 1464–1475 (1983)] is applicable except near N of √2 and 2. The present analysis concerns the strong scattering case of N approaching 2 that corresponds to a vanishing value of b. The outgoing wave front is a surface of revolution W≊a4s4−a2s2, where s is the distance from the optic axis and the coefficient a2 vanishes as N approaches 2. For N=2, a novel physical-optics analysis shows the amplitude contribution increases as (ka)1/2 and is proportional to a Pearcy–Fock function. That function is also used in scattering theory for bubbles [C. E. Dean and P. L. Marston, Appl. Opt. 30, 4764–4776 (1991)]. The analysis was confirmed by comparison with the partial-wave series for the case of a neutrally buoyant liquid neglecting any effects of the shell. The analysis shows that while N=2 has no major advantage, there are special aspects of the scattering. [Work supported by ONR.] a)Present address: EXP Group, Inc., 44063 Fremont Blvd., Fremont, CA 94538.
A T matrix for scattering from a doubly infinite fluid–solid interface with doubly periodic surface roughness
Authors: Smith Judy , Bishop Garner C.
Published: October 2005

The T-matrix formalism is used to calculate scattering of a pressure wave from a doubly infinite fluid–solid interface with doubly periodic surface roughness. The Helmholtz–Kirchhoff integral equations are used to represent the scattered pressure field in the fluid and the displacement field in the solid. The boundary conditions are applied and a system of four coupled integral equations is obtained. The incident field, the surface fields, and scattered pressure field in the fluid and displacement field in the solid, are represented by infinite series of Floquet plane waves. This process discretizes the integral equations and transforms them into a system of four coupled doubly infinite linear equations. The extended boundary condition is applied and the T matrix that relates the spectral amplitudes of the incident field to the spectral amplitudes of the scattered fields is constructed. An exact analytic solution and numerical results are obtained for scattering from a doubly periodic rough surface constructed by superposing two sinusoids each of which depends on a single but different orthogonal coordinate.
Application of the finite-element method to low-frequency mode conversion and reflection
Authors: Murphy Joseph E. , Li Gongqin , Chin-Bing Stanley A.
Published: October 2005

A finite-element model is used to compute acoustic pressure in an inhomogeneous region, and coupled to mode expansions on the left and right boundaries of that region. By allowing the incident field to consist of a single mode, one can determine a mode scattering matrix, i.e., the amplitudes for backscattered modes and amplitudes for modes transmitted through the far boundary. The modal expansions used on the two boundaries need not be the same. Examples with rapid bathemetry changes and strong range-dependent changes in sound speed and density will be shown. [Work supported by ONR and the ONR Acoustic Reverberation SRP.]
Application of finite-element models to backscatter from shallow water internal waves
Authors: Chin-Bing Stanley A. , King David B. , Murphy Joseph E. , Li Gongqin
Published: October 2005

The acoustics effects of shallow-water, solitary, internal-wave packets (solitons) have been simulated using finite-element computer models (foam, fframe, and safe). The coupled effects of the total shallow-water waveguide with its range-dependent boundaries and penetrable, shear-supporting ocean-bottom properties were included in the simulations. Our previous numerical studies at 75 Hz (and lower) had shown recognizable, although extremely weak, backscatter from the solitons with the influence of shear waves being significant only in the forward propagation. If combined effects of backscatter and shear wave conversion are significant, it is likely at higher frequencies. Examples at higher frequencies (100–250 Hz) that investigate backscatter from solitons and its possible conversion into ocean-bottom shear waves will be presented. [Work supported by ONR/NRL and ONR Acoustic Reverberation SRP.]
Three-dimensional ocean bottom reverberation computed with the adiabatic normal mode model
Authors: Dacol Dalcio K.
Published: October 2005

The adiabatic normal mode model is a full wave propagation model that is computationally efficient in the modeling of long distance propagation in range-dependent environments. Its usual formulation does not include bottom backscattering thus precluding its use in reverberation modeling. How to include such effects in the adiabatic normal mode model is the subject of this presentation; both theoretical developments and numerical examples will be presented. [Work supported by ONR.]
Numerical model of the transmit–receive response of an active sonar
Authors: Straney Cynthia B. , Forbes Michael J.
Published: October 2005

The transmit–receive response of an active sonar system measuring volume reverberation is numerically calculated as a sum of time-delayed, phase-shifted replicas of the transmitted signal. The sonar system can consist of any combination of projectors and hydrophones. The scattering volume of interest is modeled as a distribution of cylindrical and spherical scatterers of different maximum target strengths. The propagation path between projector and scatterer and scatterer and receiver is assumed to be a straight line. Temperature and density fluctuations are modeled as sound-speed changes along the propagation path and spreading and absorption are included. The sonar system and each of the scatterers in the volume are allowed to move continuously, both translationally and rotationally. Output consists of raw amplitude data received by the hydrophone(s) at a predetermined sampling rate. Calculated results are in excellent agreement with experimentally measured scattering values from a collection of hard spheres. [Work supported by ONR.]
Derivation of fricative source-filter characteristics by analysis of VCV sequences
Authors: Shadle Christine H.
Published: October 2005

Much progress has been made towards establishing source and filter characteristics of fricative consonants by comparing the sound output by a human sustaining a fricative and by a mechanical model of that subject’s static vocal tract shape. The problem can also be attacked by analysis of unsustained utterances, namely, repeated /pVFV/ sequences, using an analysis tool described elsewhere [Shadle etal., J. Phys. IV, Coll. C1 2, C1-295–C1-298 (1992)] that gives fine time resolution on the acoustic signal, and a variety of articulatory and aerodynamic data for the subjects. The repeated syllables form an ensemble, and ensemble averaging is performed across several tokens rather than the usual time-averaging within a single fricative. The resulting spectra show clear evidence of the expected changes in source (increase in high-frequency energy) and filter (format shift and pole-zero cancellation) during aVF transition. But unexpected changes are also apparent, e.g., evidence of a rounded vowel context enabling a different source strategy requiring less airflow in /pusu/compared to /pasa/. Phenomena such as devoicing in voiced fricatives can also be closely examined. Results for two subjects will be discussed. [Work supported in part by a collaborative EC SCIENCE award, CEC-SCI*0147C(EDB).]
Long-range reverberation from the seafloor in the Mid-Atlantic Ridge area
Authors: Berkson J. M. , Makris N. C. , Menis R. , Healey M. R. , Gibian G. L.
Published: October 2005

Long-range measurements of reverberation from the seafloor were made in the Mid-Atlantic Ridge area during the Acoustic Reverberation Special Research Program Reconnaissance Experiment in August 1991. Sound from a low-frequency source array at 210 to 290 Hz was scattered by the seafloor at basin-wide ranges and then received by a towed array. Reverberation images show strong returns in the direct-path region followed by strong returns within concentric bands corresponding to bottom convergence zones. Diffuse and discrete returns occur in both regions. Reverberation images from HFM pulses of differing frequency exhibit similar behavior as do CWs. Discrete features exhibit constant or decreasing relative reverberation level with frequency. Cross correlation between reverberation beam/time series for different frequency CW subpulses over these features exhibited high but variable correlation throughout the band. [Work supported by ONR.]
Influence of stud type and spacing, screw spacing, and sound absorbing material on the sound transmission through a double panel wall specimen
Authors: Quirt J. D. , Warnock A. C. C. , Halliwell R. E. , Birta J. A.
Published: October 2005

The work to be presented is part of a large series of measurements studying sound transmission through double panel walls. The wall surfaces in this work were of 16-mm gypsum board. Studs of 38-×89-mm wood or 90-mm light steel were used with spacing between stud centerlines varying from 30 to 120 cm. The spacing between screws used to attach the gypsum board was varied with the smallest separation used being 20 cm. Transmission loss was also measured for studless constructions. Transmission loss contours showed prominent dips at frequencies influenced by stud and screw spacing. Sound absorbing material added to the cavity had only a minor effect on these resonances suggesting that they are associated with panel resonances and not with the cavity between the panels. A selection of the data from this work will be presented and discussed.
Time domain analysis of internally loaded cylindrical shells at axial incidence
Authors: Conti Matthew , Dyer Ira
Published: October 2005

Internal structures can significantly modify the scattered field of an elastic shell. The influence of such internal structures within a cylindrical shell are shown to change the backscattered time-domain signal at or near axial incidence. To further elucidate this influence, bistatic measurements have been performed on two cylindrical shell models: an empty shell and a duplicate shell with unequally spaced ribs with resiliently mounted wave-bearing structures. A line source provided wideband excitation in the range 2.5<ka<10 corresponding to 3/4 to 3 times the shell ring frequency. Time domain representations of the data are presented that illuminate basic scattering processes and that emphasize the primary role of the shell compressional waves. [The authors acknowledge assistance of NRL for acquisition of data. Work supported by ONR.]
Backscattering of chirped bursts by a thin spherical shell near the coincidence frequency
Authors: Kaduchak Gregory
Published: October 2005

Previous calculations and observations [Zhang etal., J. Acoust. Soc. Am. 91, 1862–1874 (1992); G. Kaduchak, J. Acoust. Soc. Am. 91, 2400–2401(A) (1992)] have shown that tone bursts with a carrier frequency ka close to the coincidence frequency of a thin spherical shell in water exhibit a backscattering enhancement. A distinct feature associated with the a0-guided wave was enhanced relative to the specular reflection by a factor close to 3.1. In the present research, a Fourier synthesis from the partial wave series is used to investigate how chirping the frequency of the incidence burst influences the enhancement. An enhancement is still evident even when the incident burst is swept through the entire ka range of interest sufficiently rapidly for the specular and guided wave echoes to remain distinct. The enhancement is larger when ka is swept from high-to-low than from low-to-high. This is a consequence of a decrease in the group velocity with ka resulting in a localization of the echo for the high-to-low sweep. The enhancement can now exceed the aforementioned value of 3.1 and should increase the signal-to-noise ratio. [Work supported by ONR. The author acknowledges the advice of P. L. Marston.]
Perception of voicing in syllable-initial stops at different intensities: Does neural synchrony encode voice-onset?
Authors: Kluender Keith R. , Lotto Andrew J. , Jenison Rich L.
Published: October 2005

In response to stop consonants differing in voice onset time (VOT), the dominant synchronization of mid-CF chinchilla auditory nerve fibers changes from the frequencyof F2 to the frequency of F1 at onset of voicing [D. G. Sinex and J. P. McDonald, J. Acoust. Soc. Am. 85, 1995–2004 (1987)]. If this change in neutral synchronization is perceptually relevant for human listeners, changes in stimulus intensity and changes in the frequency difference between F1 and F2 should both affect perception of voicing. In a series of experiments, several continua of synthesized CV’s varying in VOT were played to listeners at levels ranging from 40 to 80 dB SPL. The frequency difference between F1 and F2 was manipulated through the use of different places of articulation and different following vowels. Subjects labeled more CV’s as voiceless as a function of increasing stimulus level and of deceasing F1–F2 frequency difference. There was also an interaction between stimulus intensity and F1–F2 frequency difference such that the effect of intensity was greater for smaller F1–F2 differences. These effects were reliable across a number of synthetic VOT series, and the effect of intensity extended to a computer edited series of hybrid CV’s in which VOT was varied by cross-splicing a naturally produced /da/ and /ta/. The effect of overall stimulus intensity was not affected by amplitude of aspiration energy or by the presence or absence of release bursts. The results provide evidence for synchrony encoding of voicing for stop consonants. [Work supported by NIDCD/NIH Grant No. DC-00719.]
Labeling of the voiceless affricate/fricative contrast and an analogous nonspeech continuum by hooded rats
Authors: Howell Peter , Reed Philip , Rosen Stuart
Published: October 2005

The voiceless affricate/fricative contrast has played an important role in auditory theories of speech perception. This type of theory draws its support from, among others, experimental data on animals. However, nothing is known about differential responding of affricate/fricative continua by animals. Preliminary results were obtained regarding the ability of hooded rats to ‘‘label’’ affricate–fricative and an analogous nonspeech continua where the nonspeech continuum was created by randomly flipping the polarity of each sample in the digitized speech waveforms with a probability 1/2. The rats were trained on the endpoints of a ‘‘cha’’–‘‘sha’’continuum (using positive reinforcement in a two-level choice experiment) cued by covariations in rise time and frication duration (0–80 ms rise time). Differential labeling was similar to humans. The animals were switched to the nonspeech continuum without further training. Once again, performance was similar to humans. The implications for auditory theories are discussed. [Work supported by MRC and CRF.]
Perception of Canadian French unvoiced stops
Authors: Jacques Benoît , Toledo Guillermo
Published: October 2005

The aim of this paper was to determine the trade-off relationship among acoustic cues, i.e., the transitions of the preceding vowel, the burst, the transitions of the following vowel, or the relevance of an acoustic cue on the perception of Canadian French unvoiced stops. To that end utterances of two segments containing VCV sequences of two different unvoiced stops and the same type of vowel were produced by a native speaker of Canadian French. Stimuli integrated by two acoustic cues of a place of articulation and a conflicting cue of another place of articulation were made up through the splicing and editing of these VCV sequences. In addition, stimuli obtained by the splicing of the second syllable in each segment were carried out in order to test the role of the transitions of the preceding vowel. Listening tests through a panel comprising of 14 French Canadian subjects were performed. Results showed that the trade-off relation of acoustic cues was the main information for the recognition of Canadian French unvoiced stops, although in a few vowel contexts, listeners might be able to identify through one acoustic cue. [Work supported by an ICCS grant to the second author.]
Telepresence
Authors: Held Richard
Published: October 2005

The feeling of being present as observer and performer in some environment is hardly ever absent except in cases of pathology. The difficulty in achieving telepresence (or virtual reality) consists in making the observer feel his/her presence in the ‘‘remote’’ environment accessed by means of machine interfaces and not in the local and immediate surround. One feels present in a perceived environment when one can anticipate actions that access it. Sensory stimulation evokes these anticipations via an internal model that includes representations of both the observer’s body and its parts, objects in the environment, and the consequences of movements of the observer. Utilization of this model by performing actions to verify the anticipated consequences either confirms or disconfirms them. To the extent that the sensory consequences are not anticipated by the model, the sense of presence will suffer. But transmission through this motor-sensory loop informs the model about transforms in space and/or time that may be interposed and in some cases at least adaptation may allow the re-establishment of the feeling of presence.
Scaling laws for sonoluminescence
Authors: Löfstedt Ritva , Barber Bradley P. , Putterman Seth
Published: October 2005

The extremely nonlinear dynamics of bubble motion is described by the Navier–Stokes equations of fluid mechanics, as coupled to the laws of heat conduction and mass diffusion. In order to gain insight into the limitations of the hydrodynamic theory of bubble collapse, scaling laws have been derived for the maximum radius, collapse temperature, hot spot lifetime, collapse pressure, and ambient radius in terms of the applied sound field and the assumption that the bubble is a gas-filled cavity. In order to match the scaling laws to the experimental observations of collapse temperature and flash width requires that the Mach number for bubble motion exceed unity. In conclusion, a description of sonoluminescence must include the properties of imploding shock waves. [Work supported by the US DOE Division of Engineering and Geophysics; R. L. is supported by an A.T.&T. fellowship.]
Characteristics of sonoluminescence at ambient temperatures near 0 °C
Authors: Barber Bradley P. , Hiller Robert , Putterman Seth
Published: October 2005

At ambient water temperatures near 0 °C, the intensity of sonoluminescence (SL) increases by over a factor of 10. This talk reports on efforts to understand and measure this effect. Issues to be discussed include the solubility of air in water as well as the flash width, quality factor, acoustic pressure, pulse height distribution, and synchronicity of these bright SL pulses. [Work supported by the US DOE Division of Advanced Energy Projects.]
Elastic Helmholtz resonators
Authors: Norris Andrew , Wickham Gerry
Published: October 2005

The influence of wall elasticity on the response of a Helmholtz resonator is examined by analyzing the canonical case of a thin elastic spherical shell with a circular aperture subject to plane-wave excitation. By neglecting the thickness of the wall and representing the elasticity via a thin shell theory the problem is reduced to one of solving an integral equation over the aperture for the polarization velocity, which is related to, but distinct from, the radial particle velocity of the fluid. The integral equation can be solved by asymptotic methods for small apertures, yielding closed-form expressions for the major resonator parameters. In general, wall compliance reduces the resonance frequency in comparison with an identically shaped rigid cavity. The Q value of the resonance is increased and the scattering strength of the cavity at resonance is enhanced by wall compliance. The asymptotic results are supported and supplemented by numerical calculations for thin steel shells in water. [Work supported by ONR.]
Acoustic radiation pressure
Authors: Lee C. P. , Wang T. G.
Published: October 2005

Acoustic radiation pressure is an area in nonlinear acoustics that has been associated with a lot of confusion and controversy since the work by Lord Rayleigh. From the more recent works, it seems that all the pieces necessary for a complete understanding of this topic are there. The purpose of this work is to put the pieces together and systematically present a coherent picture of the subject, starting from the first principles. Self-consistency will be emphasized. Therefore, although the Eulerian coordinates will be used to formulate the problem, which will be shown to be very simple and straightforward, it will also be demonstrated how the same results can easily be obtained by using the more traditional Lagrangian coordinates, if the latter are applicable. It will be argued that it is simpler to define Rayleigh and Langevin radiation pressures according to whether the system is subjected to a constraint or not. [Work supported by NASA.]
Investigation of the periodicity of sonoluminescing from a single bubble
Authors: Gaitan D. Felipe , Holt Glynn , Atchley Anthony A.
Published: October 2005

Sonoluminescence from a single bubble is produced when a sound field is used to drive a gas bubble at very large amplitudes (maximum radius≊4×equilibrium radius). At its minimum radius, the bubble interior is compressed, raising the gas temperature by as much as 5000 °K and generating a short pulse of light once every acoustic cycle. This light has been measured to be ≤50 ps in duration and repeats every cycle (∼30 μs) with a precision of 50 ps or better (Barber etal., J. Acoust. Soc. Am. 91, 3061–3063 (1992)]. Under certain conditions, however, the time interval between pulses becomes at times subharmonic (integer multiple of the driving period), pseudo-periodic (infinite period), or even chaotic (??). In this paper, preliminary measurements of this phenomena will be presented. [Work supported in part by ONR and the NPS Research Program.]
Reasonable choices for material constants in seismic modeling
Authors: Rosenbaum J. H.
Published: October 2005

The assumption that the earth is made up of homogeneous elastic layers, which can exhibit transverse isotropy and moderate constant-Q attenuation, leads to an effective method of modeling the response from a point source into a long spread of seismometer stations [J. H. Rosenbaum, Geophysics 36, 1276–1277 (1971)]. A difficulty experienced by users of such programs is the necessity of furnishing consistent elastic constants and absorption values for the formations. An extension of the long-wavelength-equivalent-medium theory [G. E. Backus, J. Geophys. Res. 67, 4427–4440 (1962)] to the anelastic case has been used to derive default options, which require minimal information from the user, appear reasonable for many earth materials, and reduce to a proper description for the case of isotropy. A very simple earth model demonstrates that parasitic modes are excited and the computations may become unstable when anelastic model parameters violate stability conditions or are inconsistent. [Work done at Shell Development Co.]
Dissipation effects on finite amplitude waves using a nonlinear progressive wave equation (NPE)
Authors: Too Gee-Pinn James , Ginsberg Jerry H.
Published: October 2005

The nonlinear progressive wave equation (NPE) computer code developed by McDonald and Kuperman [J. Acoust. Soc. Am. 81, 1406–1417 (1987)] was used to evaluate a time domain solution in acoustic waveguides. In earlier works, modified versions of NPE [Too and Ginsberg, J. Acoust. Soc. Am. 91, 59–68 (1992)], which omitted dissipation effects, were described to evaluate continuous waves as well as transient waves radiated from a circular baffled piston. In the present work, dissipation due to thermoviscous effect is added to the earlier NPE model by assuming the dissipation effect is small in the transverse direction. Dissipation effects on finite amplitude sound beams are compared with the result of nondissipated NPE model at different locations in the sound field. In addition, dissipation effects on transient waves are shown by including different wavelengths in the initial tone burst of the transient wave. [Work supported by National Science Council and the George W. Woodruff endowment.]
Generation of nondiffracting X waves using annular-array transducers
Authors: Fatemi Mostafa , Ghaseminejad K.
Published: October 2005

Nondiffracting beams have been suggested for ultrasonic imaging and tissue characterization applications because of their long depth of field. Recently, a new class of nondiffracting beams, termed the X waves, has been discovered. An advantage of these beams over the J0 Bessel beam is that the X waves are nondispersive. An ideal zero-order X wave has infinite time duration and requires infinitely large aperture area, excited by a spatially nonuniform, circular-symmetric, input, h(r,t), where r and t are the radial distance and time, respectively. In practice, X waves can be generated employing a finite size annular-array transducer. In this paper, annular-array implementation of the X waves is investigated and the errors introduced in the field due to such implementation are analyzed. Each ring in the array is excited by a different time-limited waveform. Quantitative comparisons between the field of the array and the ideal X wave is made possible by computer simulations. Results indicate that, in the range of parameters usually encountered in medical diagnosis, the errors introduced due to array implementation of the X wave can be made negligible, if a reasonable number of rings is used. The relative error is presented in terms of the ratio of element width to spacing, number of elements, and radius of the transducer. Simulation results at various observation points will be presented.
A unified approach to acoustical reflection imaging
Authors: Berkhout A. J.
Published: October 2005

A discrete theory is proposed that represents acoustical reflection measurements in terms of a so-called data matrix. One column of the data matrix is related to one source position; one row is related to one detector position. In the proposed theory, the data matrix is expressed in a sequence of matrix operators. Those operators quantify the physical processes of emission, downward propagation, reflection, upward propagation, and detection in inhomogeneous media. The concept of optimum ‘‘illumination’’ is introduced. Using the matrix formulation, it is shown how to design an experiment that is optimum for a specific target area. The imaging process is formulated in terms of double inversion: one inversion for the downward propagation operator and one inversion for the upward propagation operator. It is shown that double focusing (in emission and in detection) represents an economic version of the double inversion process. The proposed theory is pre-eminently suited to discuss imaging technology on a conceptual level.
Matched-field source localization using incoherent frequency averaging for sound-speed mismatch and array element location errors in a shallow-water environment
Authors: Akundi M. A. , Garrel S. , Smith G. B. , Chandler H. A.
Published: October 2005

Matched-field processing is a parameter estimation technique for localizing a source from the acoustic field propagating in a waveguide. The signal is observed at an array in the presence of spatially correlated noise that also propagates in the same ocean environment as the signal. Incoherent broadband averaging is a method that uses the broadband nature of an acoustic source to acquire additional gain against ambient noise and to decrease background variance common to matched-field ambiguity surfaces. Incoherent broadband averaging has been applied earlier [J. Acoust. Soc. Am. Suppl. 1 88, S27 (1990)] for source localization in the presence of random phase error in a Pekeris environment. In this paper, this method is applied using a more general environmental model (SNAP) for source localization in the presence of sound-speed mismatch and array element location errors. Preliminary results indicate that frequency averaging may have some value for localizing a source when these types of mismatch are present. [This work was supported by the Naval Research Laboratory through U.S. NAVY/ASEE Summer Faculty Research Program.] a)Summer Faculty Research Fellow, NAVY/ASEE Summer Program. b)Undergraduate student, William Penn Foundation Grant.