bluuebunny/crossref_metadata_2025 huggingface dataset:
Velocity and attenuation profiles in the Monterey Deep-Sea Fan
Authors: Brienzo Richard K.
Published: October 2005

Data obtained during a marine refraction experiment are used to estimate velocity and attenuation profiles in an area of thick sediments (2.5–3 km) on the Monterey Deep-Sea Fan. A 20-element vertical hydrophone array was deployed at mid-depth in 2800 m of water. Explosive sources, set to detonate at 1830 m, were launched at ranges between 3.5 and 37 km from the array. Estimates of velocity and attenuation as a function of depth are obtained from an analysis of the pressure time series generated by the explosive charges and received at the array. The sediment is modeled as a horizontally layered, laterally homogeneous medium. A least-squares solution is found for linear velocity gradients in each layer of the model. Velocity as a function of depth is obtained from these gradients. Attenuation coefficients in each layer of the model are found using a method of spectral ratios. The results presented here, valid for frequencies between 10 and 100 Hz, show an increase in attenuation to a depth of about 500 m. The method of spectral ratios and equations used to infer velocity structure from various parametrizations of the traveltime data are derived in appendices.
Ultrasonic down-conversion in canine hearing sensor
Authors: Fink Edward L.
Published: October 2005

Hearing threshold frequency response curves over range 2–100 kHz are reported for a group of dogs. Eight conditioned reflex techniques with different behavior paradigms were utilized. All techniques produced a curve that is unsymmetrical about primary resonance minimum and had a secondary resonance minimum and maximum peak. The position of the peaks varied with the paradigm. Comparison of the curves with models of cochlea dynamics showed that experimental data is best fitted with a model having a 0.35–0.5 power-law generation term which represents subharmonic frequency generation (i.e., down-conversion), by basilar membrane, which is in resonance with a secondary resonance structure. Additional evidence is presented for a subharmonmic generation mechanism comprising the simultaneous impression of 44 kHz and a lower amplitude 22-kHz sound via an ultrasonic transponder collar. The 44-kHz threshold was raised when the 22-kHz sound had a negative phase. Neural center involvement in forming secondary peaks was explored by measurements of EEG evoked potentials and a drug modification effect. EEG measurements revealed an echo which was delayed from the initial nerve pulse, and lithium, which is limbic specific, injection had the effect of smoothing or eliminating secondary peaks in threshold curve. These results suggest two areas of memory being active and interfering with one another, one of them being located in the limbic, instinct center.
A century of acoustics at Brown and elsewhere and the people who made it happen
Authors: Beyer Robert T.
Published: October 2005

Acoustics in the Physics Department at Brown began in the 1870s and faded in the 1970s. Some memories of the way up and the way down, from Eli Whitney Blake and his dealings with Alexander Graham Bell to Bruce Lindsay and the rest of us, with additional remarks about personalities in the subfields of ultrasonics, underwater sound, and nonlinear acoustics in and out of Brown.
Visual focus of attention in adaptive language acquisition
Authors: Sankar Ananth , Gorin Allen L.
Published: October 2005

In this research on adaptive language acquisition, connectionist systems have been investigated that learn the mapping from a message to a meaningful machine action through interaction with a complex environment. Thus far, the only input to these systems has been the message. However, in many cases, the action also depends on the state of the world, motivating the study of systems with multisensory input. In this work, a task is considered where the machine receives both message and visual input. In particular, the machine action is to focus its attention on one of many blocks of different colors and shapes, in response to a message such as ‘‘Lookattheredsquare.’’ This is done by minimizing a time-varying potential function that correlates the message and visual input. The visual input is factored through color and shape sensoryprimitivenodes in an information-theoreticconnectionistnetwork, allowing generalization between different objects having the same color or shape. The system runs in a conversationalmode where the user can provide clarifying messages and error feedback, until the system responds correctly. During the course of performing its task, a vocabulary of 389 words was acquired from approximately 1300 unconstrained natural language inputs, collected from ten users. The average number of inputs for the machine to respond correctly was only 1.4.
A study of Lamb waves in anisotropic plates
Authors: Lin W. , Keer L. M.
Published: October 2005

This paper is concerned with the Lamb wave spectra for layered orthotropic elastic media. The spectra computed from three-dimensional elasticity theory for orthotropic layers are compared with those computed from simpler exact or approximate theories as follows: classical plate theory, plane stress (membrane mode), plane strain, and SV wave analogue. At low frequencies, it is found that there are seven roots of the generalized Rayleigh–Lamb equation for a single layer system. Three of the seven roots are close to the values predicted by the plane stress model for the symmetric mode and by the classical plate theory for the antisymmetric mode. The other three roots are identical to those predicted by the SV analogue and by the plane strain state, and these roots correspond to spurious modes. The spurious wave speeds also represent the limiting values of genuine wave speeds representing guided waves, such as when the frequency tends to infinity. The final root corresponds to a common point of different branches of slowness surfaces. Good agreement is also found between the three-dimensional elasticity analysis and simplified membrane and plate analyses for multilayered media.
Small scale inhomogeneity and intermittency of surface scattering during the 1992 Gulf of Alaska surface scatter and air–sea interaction experiment
Authors: Adair Richard G. , Huster Michael E. , Miklovic Donald W.
Published: October 2005

An experimental and processing technique is described that provides high resolution, broadband estimates of near-surface acoustic scattering variation in time and space. Application of the technique in the 1992 Gulf of Alaska surface scatter and air–sea interaction experiment achieved approximately 1-m×5-m range and cross-range scattering resolution over the frequency range of 100–1400 Hz, with temporal changes measured over intervals of 7 s to 30 min. Results from this experiment clearly show that during high wind, high sea state conditions, the surface scattering was dominated by intense, highly localized events with spatial densities on the order of 10–100 per sq km. A significant fraction of these events endured for time scales of a few minutes only. Some of these discrete scatterers were sufficiently removed from the surface (20–30 m) to generate resolvable multipaths. Also described is the intensity and spatial density of scatterers as a function of the environmental conditions over the several day period of the experiment.
Influence of an internal reference system and cross-modality matching on the subjective rating of speech synthesizers
Authors: Pavlovic Chaslav V. , Rossi Mario , Espesser Robert
Published: October 2005

In previous studies it was concluded that contextual invariance and subject invariance of categorical and magnitude estimates of speech quality could be improved by introducing a reference system and by normalizing the results with respect to it. The reference signal used in the previous studies was natural speech. The use of such a reference system may present problems for applications where cross-language comparisons of synthesizers are made. In particular, this refers to the difficulty of ensuring equal subjective quality of different talkers in different languages. In this study the possibility of substituting an actual reference signal with an ‘‘internal’’ reference defined to the subject as the system of optimal quality is investigated. Another objective of this study is to explore whether a sometimes difficult task of free number production required in magnitude estimations could be replaced by cross-modality matches using lines of various lengths produced by subjects on a computer screen. The main concern here was related to the unknown effects of the limited width of the computer screen on the magnitude estimation task. [This research was made possible by Grant No. 2589 from the EEC Esprit SAM project.]
Elastohydrodynamic waves associated with a thick elastic cylinder immersed in fluid
Authors: Manley Martin G.
Published: October 2005

The behavior of guided flexural waves of an infinite, elastic, thick-walled circular cylinder immersed in fluid is considered in the low-frequency limit. The fluid is of lower density than the solid. The dependence of field quantities on φ, t, and x is of the form einφe−iωteikx, where n is the circumferential wave number, ω is the frequency of vibration, k is the wave number in the axial direction, φ is the circumferential coordinate, t is time, and x is the coordinate in the direction of the cylinder axis. Solutions for the exact dispersion relation based on the full elastodynamic equations will be presented. Appropriate approximations will be shown for a simplified representation of the dispersion relation of the lowest-order flexural wave. It will be shown that standard shell theory results correspond to different limits of the exact result. [Work supported by the PSU Applied Research Laboratory Exploratory and Foundational Research Program. The author acknowledges the advice of A. D. Pierce.]
Environmentally controlled free-field towed array calibration system
Authors: Beason M. K. , Luker L. D. , Deebel M. J.
Published: October 2005

The methodology, design, and capabilities of the long-line hydrophone calibrator (LLHC) are described. Towed-array calibrations normally require a large body of water to insure that the reflections from the sides, surface, and bottom have a negligible effect on the measurement. Additionally, it is difficult to measure directivity patterns on entire array modules. The LLHC will provide an environmentally controlled alternative to open water calibrations as well as the ability to measure directivity patterns and the complex free-field sensitivity of long underwater arrays. Extended projectors inside a closed tube are driven to produce an acoustic pressure field that is equivalent to a free-field plane acoustic wave propagating from any desired angle of incidence. Projector drives are determined by measuring the transfer function between the projectors and monitor hydrophones within the tube. The LLHC will provide complex free-field sensitivities and directivity patterns from 5 to 700 Hz at temperatures from 2 to 35 °C to depths over 650 m. Transducer configuration and mechanical issues will be discussed. Results from a recent prototype demonstration will be presented. [Work supported by NAVSEA.]
Interpretation of in situ logging p-wave velocities in sediments over very young crust
Authors: Lavoie Dawn , Fischer Kathleen
Published: October 2005

Laboratory and downhole logging measurements on sediments in the Lau back arc basin display none of the expected trends in physical and acoustic properties as a function of depth. Insitu, the sediments are underconsolidated, although in the lab the sediments can consolidate normally, as shown by measuring both compressional and shear wave velocity in a controlled laboratory triaxial setting. Both compressional and shear wave velocity, measured in the triaxial cell after consolidation to estimated insitu pressures, are significantly higher than those measured insitu. The primary reason that sediments are not consolidating insitu, and therefore, compressional and shear wave velocity are not decreasing downhole, is that water lost during the consolidation process is rapidly replaced by fluids circulating through the system convectively. The undisturbed microfabrics of these sediments were examined by scanning electron microscopy equipped with energy dispersive x-ray spectral analysis and image analysis systems. This allowed quantitative measurement of pore space and degree (and type) of cementation. In general, compressional and shear wave velocity did not show consistent correlation with grain size distribution. Instead, variations in velocity within lithological units were related to the distribution of pore space and digenetic state of the sediment.
Just noticeable differences for intensity and their relation to loudness
Authors: Johnson Jennifer H. , Turner Christopher W. , Zwislocki Jozef J. , Margolis Robert H.
Published: October 2005

The present study examines the relation between the form of the loudness function and the size of the intensity just noticeable difference (jnd). The hypothesis that equal loudnesses at any given sound frequency yield equal-intensity jnd’s was examined. In addition, Hellman et al.’s [J. Acoust. Soc. Am. 82, 448–453 (1987)] experiment, which showed that jnd’s are independent of the slope of the loudness function was replicated. Threshold shifts and altered loudness-balance functions for 1-kHz tones were produced by using backgrounds of narrow- or wideband noise. The two types of background noise produced intersecting points on loudness-balance functions at which intensity jnd’s were obtained. Intensity jnd’s were also obtained at equal-loudness levels (corresponding to 30, 40, 50, and 60 dB SL in the unmasked ear) under each of the two noise conditions and in quiet. The results indicate that tones of equal loudness produce approximately equal jnd’s and that there is no apparent relation between the slope of the loudness-balance functions and the size of the intensity jnd.
Individual differences in the improvement in spectral shape discrimination due to increasing number of nonsignal tones
Authors: Kidd Gerald
Published: October 2005

The effect of the number of nonsignal tones on the just-discriminable difference in spectral shape was evaluated for 12 naive subjects. The signal was an intensity increment to the center tone of a multitone complex. The tones were spaced at equal frequency ratios and, except for the signal increment, were equal in level. The number of nonsignal tones ranged from 2 to 20. Consistent with previous studies using equally spaced components, group mean thresholds improved monotonically with increasing number of tones. Group mean thresholds improved about 8 dB over the range of reference spectra employed. Large differences were found across subjects in overall performance, and in the magnitude of the improvement with increasing number of nonsignal tones. The greatest intersubject variability was observed for the stimuli composed of the fewest components. It was concluded that the differences reported in the literature concerning the presence and magnitude of the improvement are due both to differences in the procedures used and to the large individual differences that occur among subjects.
Evaluation of angle-dependent spectral distortion for infinite, planar elastic media via angular spectrum decomposition
Authors: Orofino Donald P. , Pedersen Peder C.
Published: October 2005

The angle-dependent spectral distortion for an infinite planar interface (IP-ASD) is examined for the case of fluid–fluid and fluid–solid (elastic) interfaces. The results are based on computation of the angular spectrum (plane wave) decomposition of the acoustic pressure field as radiated by an equivalent image source transducer, for each frequency of interest. The exact incident-angle-dependent reflection coefficient of the interface may thus be used in the computation, versus approximate methods previously required [D. P. Orofino and P. C. Pedersen, J. Acoust. Soc. Am. 92, 2883–2899 (1992)]. Comparisons of the previous approximate IP-ASD results to the current exact results are made. IP-ASD results for elastic parallel plates are also presented for a variety of plate orientations and geometries. For the special case of normal incidence, a comparison of the IP-ASD result to a previously published result is made. The IP-ASD is additionally examined for a reduced subset of plane wave components that approximate the radiated pressure field. The error in the IP-ASD versus the number of plane waves in the subset is discussed.
Relation between surface helical waves and elastic cylinder resonances
Authors: Conoir J. M. , Rembert P. , Lenoir O. , Izbicki J. L.
Published: October 2005

In this paper, the authors deal with theoretical and experimental studies about the acoustic scattering by an elastic solid cylinder immersed in water, at oblique incidence. Comparisons are made between the calculated form function and measured scattered pressure for incidence angles varying from 0° to 30°, in the normalized frequency range 0–30. The behavior of the resonances when the incidence angle increases is shown and the connection between helical surface waves propagation and resonance is explained, using the contributions of the resonance scattering theory and the Sommerfeld–Watson transformation. More accurately, resonances are due to the phase matching of circumnavigating helical surface waves, and a refraction effect is found to take place between the incident and the helical surface wave direction of propagation, which clearly explains the resonance shift with respect to incidence angle variations. Guided waves appear at oblique incidence with a polarization primarily transverse at small incidence angles.
Exact solutions of the Helmholtz equation for plane wave propagation in a medium with variable density and sound speed
Authors: Robins Alvin J.
Published: October 2005

The Helmholtz equation for a variable density medium is considered and solutions are sought for the case of horizontal stratification, both sound speed and density varying continuously with depth. It is shown that the nonlinear density dependence in the Helmholtz equation can be reduced to a linear form by means of appropriate transformations. A general procedure is then outlined by which forms of density profile can be generated permitting analytical solutions for plane wave propagation in a stratified medium. The same procedure is applicable to calculate forms of sound-speed profile permitting exact solutions in the presence of a given density stratification. Some specific examples are considered, for which representative density profiles are calculated in terms of well-known special functions such as Bessel and Airy functions. Comparison with measured data shows that the analytical density and sound-speed profiles derived are capable of giving good agreement with real density and speed profiles in marine sediments.
An expression for time and angle spreading from rough thin sediments
Authors: McCammon Diana F. , Thompson William
Published: October 2005

An approach to modeling the intensity distribution from a rough thin sediment region that uses incoherent facet scattering has been extended to the time domain. This provides a mathematical method for comparing spreading simultaneously in time and angle, as well as computing various measures of these spreads such as the standard deviation or 3 dB down point. It is shown that the relationship between the time-spread standard deviation and the angle-spread standard deviation is approximately linear, enabling one to be predicted from a measurement of the other.
Shape oscillations of bubbles in water driven by modulated ultrasonic radiation pressure: Observations and detection with scattered laser light
Authors: Asaki Thomas J. , Marston Philip L. , Trinh Eugene H.
Published: October 2005

Steady-state quadrupole shape oscillations of air bubbles trapped in water were excited by amplitude modulation of the acoustic radiation pressure used for levitation. This method of exciting controlled shape oscillations may make possible noncontact dynamical measurements of the rheological properties of bubbles. Bubble sizes ranged from 1.6- to 12-mm diameter corresponding to observed quadrupole mode frequenices of 190 to 17 Hz. Small-amplitude oscillations were detected by interference of scattered laser light. Some larger amplitude oscillations were detected by the unaided eye or with a television camera. The structure of the acoustic field in the levitator needed for the levitation of large bubbles is discussed. In the absence of modulation the levitated bubbles had an oblate shape.
Sound-speed profile inversion using a large aperture vertical line array
Authors: Tran Jean-Marie Q. D. , Hodgkiss William S.
Published: October 2005

In this paper, the single vertical slice ocean acoustic tomography problem is investigated with a large aperture vertical line array and a narrow-band low-frequency acoustic source deployed at a known location. Within the framework of matched-field processing and adiabatic normal mode theory, the self-cohering technique of Bucker is shown to provide a smooth measure of sound-speed mismatch. Simple simulation results lead to the development of a minimization procedure to invert for the sound-speed profile using a good starting solution (e.g., based on historical data). The technique then is demonstrated with additional simulations for sound-speed structures characteristic of the NE Pacific.
Absorption and velocity of ultrasound in binary solutions of poly (ethylene glycol) and water
Authors: Esquivel-Sirvent R. , Tan B. , Abdelraziq I. , Yun S. S. , Stumpf F. B.
Published: October 2005

The absorption and velocity of ultrasound were studied for solutions of 10 000 molecular-weight poly (ethylene glycol) and distilled water. The frequency used was 21 MHz and the concentration (by weight) ranged from 1% to 9% of poly (ethylene glycol) in water. The shear viscosity was also measured. Temperatures of 25, 30, 35, 40, 45 °C were used for the measurements. Observations showed that the ultrasonic absorption decreases with increasing temperature at a given concentration and also increases with concentration at a given temperature. The velocity increases with increasing temperature and concentration. Finally, the shear viscosity measurements show it decreasing with temperature but also increasing with concentration.
The state vector approach to the wave analysis of the forced vibration of a cylindrical shell. Part II: Finite cylinders in vacuum
Authors: Borgiotti Giorgio V. , Rosen Erik M.
Published: October 2005

The vibrational response of a circular cylindrical shell of a finite length in vacuum, excited by a point force of arbitrary orientation, is studied by using wave techniques and the state vector formalism. Because of the geometric symmetry, both the point excitation and the resulting vibrational response can be decomposed into Fourier circumferential components. The forced vibration is expressed as a linear superposition of ‘‘waveguide modes’’ with different circumferential numbers both propagating and attenuating. State vector techniques are used to identify the ‘‘reflection matrices,’’ characterizing, for each circumferential number, the linear relationship between the complex amplitudes of the waves ‘‘ingoing’’ to and ‘‘outgoing’’ from the end terminations. The discontinuity conditions at the point excitation provide the last set of equations needed for the complete identification of the vibrational response. A few particular cases, including a termination consisting of rigid disks having masses and moving as rigid bodies, are discussed in detail. Numerical results are presented. Because the approach is essentially analytical, the computational complexity is substantially reduced with respect to purely numerical methods, and largely independent of the cylinder length.
The prediction of ringing noise of a drop hammer in a rectangular enclosure
Authors: Lam Y. W. , Hodgson D. C.
Published: October 2005

The result of the prediction of the ringing noise of a 1/3 scale model of a drop hammer in a rectangular room is presented. The noise prediction uses a numerical technique developed in an earlier work [Y. W. Lam and D. C. Hodgson, J. Acoust. Soc. Am. 88, 1993–2000 (1990)]. The technique is based on the Helmholtz integral equation with a modified Green’s function to account for the effect of the enclosure. The vibration data required by the noise prediction technique was obtained by finite element predictions and impact response experiments. It was found that the noise prediction shows good agreement with measurements in general, but at certain frequencies noise other than the ringing noise was found to contribute significantly towards the measured noise levels.
A simple method of calculating the interaural cross-correlation function for a sound field
Authors: Nakajima Tatsumi , Yoshida Jun , Ando Yoichi
Published: October 2005

A simple equation for calculating the interaural cross-correlation function at the two ears of a dummy head for octave bandpass-filtered noise (125 Hz–8 kHz) was derived. This can be applied for any single sound direction. Superposing such cross-correlation functions (weighted with the spectrum of a source signal), the interaural cross-correlation function and its magnitude for a sound field with multiple reflections may be calculated. This is called the IACC for music and continuous speech. Agreement of calculated IACCs with measured ones is satisfactory for these sound sources. When IACC values are measured with a dummy head and with real human heads, the difference in the size of heads is not critical.
Elastic Helmholtz resonators
Authors: Norris A. N. , Wickham G.
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.
Optical transducer for reception of ultrasonic waves
Authors: Phillips Patrick J. , von Ramm Olaf T. , Swartz John C. , Guenther Bob D.
Published: October 2005

A new optical transducer for the detection of acoustic pressure in the diagnostic ultrasound frequency range is described. This transducer is based on the modulation of an evanescent light field by the incident acoustic energy. Theoretical design considerations are presented for the purpose of developing the most sensitive transducer. Based on these considerations an experimental transducer was constructed. Although less sensitive than predicted this device was capable of transducing ultrasonic pulses with a 1.0-MHz center frequency at diagnostic ultrasound amplitude levels. The techniques developed here are applicable for two-dimensional transduction and may prove a viable alternative to piezoelectric array transducers.
Diffraction of evanescent wave tone bursts on a membrane in air
Authors: Matula Thomas J. , Marston Philip L.
Published: October 2005

A novel electromagnetic acoustic wave transducer (EMAT) was used to generate plane subsonic wave tone bursts on aluminized Mylar membranes. The evanescent wave field in the air surrounding the membrane was studied. Diffraction of the burst by a sharp edge in air was also observed. The diffracted signal was measured using a microphone as a function of the gap h between the membrane and the knife edge. The diffracted pressure decreases exponentially with increasing h as expected from an approximate analysis of edge diffraction of evanescent waves [L. B. Felsen, J. Opt. Soc. Am. 66, 751–760 (1976)]. The importance of such diffraction is that it produces far-field radiation of energy that otherwise would be trapped to a membrane or plate.
Indices of frequency and temporal resolution as a function of level
Authors: Cox Robyn M. , Alexander Genevieve C.
Published: October 2005

Several investigators have suggested that between-subject variations in hearing aid benefit may be related to between-subject variations in auditory resolution. Evaluation of this relationship is complicated by the need to assess resolution at several frequencies and levels in hearing-impaired listeners who may not tolerate lengthy test procedures. This paper reports data from normal-hearing listeners for abbreviated indices of frequency and temporal resolution. For a particular frequency-stimulus level combination, both indices may be derived from three pure-tone thresholds obtained with different masking stimuli. Norms are reported as a function of masker level for each index at four test frequencies. Changes in the indices as a function of masker level were consistent with expectations based on related studies by other investigators. Norms were obtained using a supra-aural earphone. Comparison of results from supra-aural and insert earphones suggested that low-frequency sound leakage substantially affected the norms for 500 Hz. Reliability of individual indices was good to excellent.
Modeling of contextual effects based on spectral peak interaction
Authors: Akagi Masato
Published: October 2005

This paper presents a model of contextual effects able to cope with coarticulation problems, especially vowel neutralization. This model is designed to model the superior recognition ability mechanisms of humans and apply these mechanisms to automatic speech recognition and synthesis. It predicts target spectral peaks in reduced vowels, based on interactions between spectral peak pairs. To construct and substantiate the model, psychoacoustic experiments were carried out to measure the extent of phoneme boundary shift with a single formant stimulus as a preceding anchor. The results of the experiments were compared with the spectral peak interaction results obtained from real speech data using the model. This comparison showed that the obtained spectral peak interactions, measured through perceptual boundary shifts with a single formant anchor, are similar to the spectral peak interactions estimated by the model. Additionally, recovery simulations of reduced spectral peak trajectories with real speech data showed that the spectral peak interactions obtained from the psychoacoustic experiments can be used to predict target spectral peaks from reduced spectral peak trajectories in the same manner as the spectral peak interaction function estimated by the model. These results suggest that the model may be emulating aspects of the human mechanisms, that the contextual effects resulting from the interactions between single formant stimuli can play an important role in improving phoneme neutralization recovery, and that the neutralization recovery model can be formulated as the sum of the interactions between spectral peaks. Furthermore, the model can be implemented as a speech recognition preprocessor to reduce recognition error rates because it can overshoot spectral peak trajectories, shift spectral peaks toward their targets, and increase distances among category centers and Bhattacharyya distances between vowel categories.
On the use of neural networks in articulatory speech synthesis
Authors: Rahim Mazin G. , Goodyear Colin C. , Kleijn W. Bastiaan , Schroeter Juergen , Sondhi M. Mohan
Published: October 2005

A long-standing problem in the analysis and synthesis of speech by articulatory description is the estimation of the vocal tract shape parameters from natural input speech. Methods to relate spectral parameters to articulatory positions are feasible if a sufficiently large amount of data is available. This, however, results in a high computational load and large memory requirements. Further, one needs to accommodate ambiguities in this mapping due to the nonuniqueness problem (i.e., several vocal tract shapes can result in identical spectral envelopes). This paper describes the use of artificial neural networks for acoustic to articulatory parameter mapping. Experimental results show that a single feed-forward neural net is unable to perform this mapping sufficiently well when trained on a large data set. An alternative procedure is proposed, based on an assembly of neural networks. Each network is designated to a specific region in the articulatory space, and performs a mapping from cepstral values into tract areas. The training of this assembly is executed in two stages: In the first stage, a codebook of suitably normalized articulatory parameters is used, and in the second stage, real speech data are used to further improve the mapping. During synthesis, neural networks are selected by dynamic programming using a criterion that ensures smoothly varying vocal tract shapes while maintaining a good spectral match. The method is able to accommodate nonuniqueness in acoustic-to-articulatory mapping and can be bootstrapped efficiently from natural speech. Results on the performance of this procedure compared to other mapping procedures, including codebook look-up and a single multilayered network, are presented.
A theory for the optimal control of the far-field acoustic pressure radiating from submerged structures
Authors: Meirovitch Leonard
Published: October 2005

This paper is concerned with the problem of suppressing the far-field acoustic pressure radiating from a structure interacting with fluid. In particular, it develops a modern control theory for the optimal control of the vibration of a submerged structure in a way that the far-field acoustic radiation pressure is minimized.
Evaluation of high-resolution frequency estimation methods for determining frequencies of eigenmodes in shallow water acoustic field
Authors: Rajan Subramaniam D. , Bhatta Saurav D.
Published: October 2005

In shallow water, the acoustic field in the far field, due to a point source, can be modeled as a sum of contributions from trapped modes propagating in the wave guide. In many applications, it is necessary to estimate the eigenvalues of these modes from a measurement of the acoustic field made on a horizontal array using a monochromatic source. In this paper the performance of two high-resolution methods (MUSIC and ESPRIT) in estimating the eigenvalues of the modes from the measured field is evaluated. In particular, we investigate the ability of these methods to estimate the frequencies accurately for various signal to noise ratios and their ability to resolve closely spaced frequencies using synthetic noisy data. Of the two methods, ESPRIT had the better performance in terms of the variance of the estimates. Simulation performed to study the effect of modeling errors on the performance of the algorithms showed that, for a medium that is weakly range dependent, the performance of the algorithms is not adversely affected. But errors in ranging and the presence of colored noise in data have considerable impact on their performance. The MUSIC algorithm shows marked degradation in performance when there are ranging errors. Taken overall, ESPRIT has the most acceptable performance levels, both in terms of its accuracy of the estimates and its robustness in the presence of modeling errors.
Intensity just-noticeable differences at equal-loudness levels in normal and pathological ears
Authors: Stillman Jennifer A. , Zwislocki Jozef J. , Zhang Minsheng , Cefaratti Lisa K.
Published: October 2005

The relationship between loudness level and intensity discrimination was investigated in the frequency range 0.5–6.5 kHz by comparing the intensity just-noticeable differences (jnd’s) at a number of equal-loudness levels in the better and poorer ears of eight individuals with essentially unilateral hearing loss of cochlear origin. Such hearing loss usually produces loudness recruitment, altering the relationships among the loudness, sound-pressure level (SPL), and sensation-level (SL) variables, so that their effects can be separated. In these experiments, the jnd’s were correlated with loudness level, not SPL or SL. Although, in some listeners, there were significant differences between jnd’s in the two ears at some binaurally equal-loudness levels, they were not systematic over the group of listeners. Statistically, there was no significant difference between equal-loudness jnd’s in the two ears, whereas the corresponding SLs and SPLs were significantly different. The rate of loudness growth had no effect on the jnd’s. As expected from the near-miss to Weber’s law, the mean jnd’s decreased with sound intensity. The corresponding decrease in the mean Weber fraction, ΔI/I, was accompanied by a decrement in its intrasubject standard deviation. The latter was correlated with the mean, independent of its relationship to SPL or SL.
Comodulation masking release in subjects with unilateral and bilateral hearing impairment
Authors: Moore Brian C. J. , Shailer Michael J. , Hall Joseph W. , Schooneveldt Gregory P.
Published: October 2005

Three subjects with unilateral cochlear hearing loss and three subjects with bilateral cochlear hearing loss were tested in three experiments. In the first, their auditory filter shapes were measured for center frequencies of 700 and 2000 Hz, using the notched-noise method. The auditory filters were generally broader for the impaired than for the normal ears. In experiment 2, the threshold for detecting a 2000-Hz signal centered in a band of noise was measured as a function of the noise bandwidth for a Gaussian noise, and for that same noise multiplied (modulated) by a second noise low-pass filtered at 12.5 Hz. For the Gaussian noise, thresholds increased up to a certain noise bandwidth and then flattened off. This bandwidth was usually greater for the impaired than for the normal ears, consistent with the broader auditory filters of the impaired ears. For the modulated noise, thresholds tended to decrease when the noise bandwidth was increased beyond a certain value, indicating comodulation masking release (CMR).

The decrease occurred at wider bandwidths for the impaired than for the normal ears. For the unilaterally impaired subjects, the amount of decrease was smaller for the impaired than for the normal ears when tested at equal SPL, but not when tested at equal SL. In experiment 3, the threshold for detecting a 700-Hz signal centered in a 20-Hz-wide band of noise (the on-frequency band, ONB) was measured in the presence of eight flanking bands (FBs) whose envelopes were either identical with that of the ONB (correlated condition) or were uncorrelated. CMR was defined as the difference in threshold between the correlated and uncorrelated conditions. The ONB and the FBs were presented either to the same ear (monaural condition) or to opposite ears (dichotic condition). CMRs tended to be greatest at high levels of the ONB and the FBs. CMRs in the monaural condition were smaller for hearing-impaired than for normal ears. However, at high levels, CMRs in the dichotic condition were similar for normal, bilaterally impaired, and unilaterally impaired subjects.

In the latter case, CMRs were similar when the ONB was presented to the normal ear and to the impaired ear of each subject. It is concluded that: (1) the small CMRs often found for subjects with cochlear hearing loss can be partly attributed to the low sensation level of the stimuli; (2) reduced frequency selectivity may also contribute to small CMRs; and (3) independence of the output of the auditory filters centered on the ONB and the FBs, as occurs under dichotic conditions, can lead to large CMRs in impaired subjects.
Frequency discrimination in noise: Comparison of cat performances with auditory-nerve models
Authors: Hienz Robert D. , Sachs Murray B. , Aleszczyk Cynthia M.
Published: October 2005

Pure-tone frequency discrimination (ΔF) performances were measured in cats and compared to neural models of these ΔF performances based on auditory-nerve data in cats. Animal psychophysical techniques were used to train cats to discriminate frequency changes for pulsed pure tones in background noise at both 1.0 and 3.0 kHz. A go-left, go-right procedure was employed, and ΔF’s were measured in noise as a function of signal level at a constant signal-to-noise ratio. In contrast to human listeners, cats showed increases in ΔF at 1.0 kHz with increasing signal level. Model estimates of ΔF’s based on rate responses in the cat auditory nerve predict increasing ΔF with increasing signal level, the trend observed in the cat psychophysical data. Model estimates of ΔF’s based on temporal (phase-locking) properties in cat auditory nerve, on the other hand, predict decreases in ΔF that have been observed in previous data from human listeners [Dye and Hafter, J. Acoust. Soc. Am. 67, 1746–1753 (1980)]. These results suggest that for cats, average rate, rather than phase-locking, may be used by the central nervous system in performing frequency discrimination in background noise at 1.0 kHz. At 3.0 kHz cats showed little change in ΔF as a function of signal level, a result similar to the trend for human listeners to show no change or slight increases in ΔF with increases in signal level for tones in the 2- to 3-kHz range.
Focused attention during selective adaptation along a place of articulation continuum
Authors: Sussman Joan E.
Published: October 2005

The current investigation manipulated subjects’ attention to adaptor tokens in five selective adaptation experiments. All stimuli were synthetic consonant–vowel syllables, with the consonant varying from [b] to [d] by formant frequency transitions. Two distractor conditions (auditory and visual) were compared to a more typical endpoint-[da] adaptor condition. Distraction from endpoint-[da] adaptors to phonetically distinct [si] and [1i] was used to observe whether smaller adaptation effects would result when attention was not focused on adaptor stimuli. In contrast, a focused attention condition required subjects to whisper [ba] adaptors right after they were heard. Performance in the focused attention condition was compared to a more typical endpoint-[ba] adaptation condition. Results indicated that focused attention did not affect the size of the adaptation effect. Asymmetrical adaptation results for [da] vs [ba] adaptors, and a larger amount of adaptation with the presence of contralateral ‘‘distractor’’ syllables, resembled findings in psychoacoustic studies of discrimination and loudness adaptation. These results suggest that two levels of auditory processing (not special to speech perception) were responsible for the observed adaptation effects.
Reconstruction of the acoustic field over a limited surface area on a vibrating cylinder
Authors: Sarkissian Angie , Gaumond Charles F. , Williams Earl G. , Houston Brian H.
Published: October 2005

The acoustic field on a small region on the surface of a radiating cylindrical shell is reconstructed from measurements of pressure made on a limited nearby surface. The boundary-element method is applied to compute an operator relating the pressure on a small measurement surface located near the structure to the normal velocity at all points on the structure surface. Since the inverse problem of the reconstruction of the surface field is ill posed, singular value decomposition is applied to invert the operator. It is demonstrated that the surface field may be reconstructed over the portion of the structure surface located under the measurement surface.
Nonlinear vibrations in the air column of a clarinet artificially blown
Authors: Idogawa Tohru , Kobata Tokihiko , Komuro Kouji , Iwaki Masakazu
Published: October 2005

A clarinet with all toneholes closed has been blown artificially and the respective variations of mouthpiece sound pressure, reed opening, and volume flow from the artificial mouth into the instrument have been measured. For a fixed lip adjustment (lip–reed contact position and height of the reed opening under lip pressure), several different vibratory states were found over the complete range of the blowing pressure. The states were stable within their respective regions, but sudden transitions took place from one state to the other when the blowing pressure was varied beyond the stable region. Multiple vibratory states were excitable in some ranges of the blowing pressure, the state excited being dependent upon the manner in which the blowing pressure was varied. The experiment was repeated for different lip adjustments. For the examples discussed, the closed tonehole fundamental of this instrument (D3 on the equally tempered scale) was inevitably produced, but other stable vibratory states were also excited. The vibratory states found for the lip adjustments presented were both periodic states emitting tones of pitch D3 or of much higher pitches, and aperiodic states most of which had an attractor of torus T2. At least one state of torus T3 was identified. Excitation regions of these vibratory states are described.
Auditory demonstrations on compact disk for large N
Authors: Hartmann William Morris
Published: October 2005

The popular compact disk entitled Auditory Demonstrations, sponsored by the Acoustical Society of America, includes a number of demonstrations that lead to quantitative results. Those demonstrations are evaluated here in the context of a sizeable class in a lecture room. Demonstrations concern masking, loudness, and pitch; specifically they are numbers 2, 3, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 20, and 25. The evaluations find that most of the demonstrations successfully illustrate psychoacoustical principles in a classroom context; others are less successful or require special circumstances for success. Explanations for success and failure are offered, together with some suggestions for optimizing the chances of success.
Complex effective depth of the ocean bottom
Authors: Zhang Z. Y. , Tindle C. T.
Published: October 2005

The effective depth approximation is extended to allow for energy loss on reflection at an attenuating, low shear speed, solid ocean bottom. The resulting complex effective depth leads to a novel and efficient algorithm for finding the exact complex eigenvalues for the normal modes in isovelocity water over an attenuating fluid or solid bottom while avoiding numerical searches. The method gives rapid normal mode solutions for shallow water propagation including the effects of leaky modes.
Weakly nonlinear waves radiated by pulsations of a cylinder
Authors: Yano Takeru , Inoue Yoshinori
Published: October 2005

A cylindrical sound wave is radiated into an unbounded ideal gas by an infinite circular cylinder that executes a sinusoidal pulsation uniformly along its axis with small amplitude and moderate frequency for only one period. In the leading order of approximation, the weakly nonlinear propagation of the wave is studied for the case of sufficiently large acoustic Reynolds number up to the stage that its profile develops into a cylindrical N wave with a tail. In the near field, solving the linear wave equation gives the near-field solution, which has a tail following the body part of the wave. The tail of the velocity profile decreases asymptotically in proportion to t*−4 as t*→∞ at a fixed point in the near field and to t*−5/2 at a fixed point in the far field (t* is the time from the beginning of the pulsation). The tail vanishes in a high frequency limit with an acoustic Mach number being fixed. In the far field, an exact solution, which matches with the near-field solution, is obtained for a far-field equation by the method of strained coordinates. The evolution of the two shocks and the tail are then examined by making use of the equal-areas rule. At large distances from the cylinder, the whole profile of the wave approaches to an N wave with a long tail.