bluuebunny/crossref_metadata_2025 huggingface dataset:
Complete gradient optimization of a recurrent network applied to /b/,/d/,/g/ discrimination
Authors: Watrous Raymond L. , Ladendorf Bruce , Kuhn Gary
Published: October 2005

Two techniques for complete gradient optimization of a given connectionist network with recurrent links are described. The first technique computes network outputs on the forward pass, and contributions to the complete (or truncated) gradient on a backward pass. The second technique computes both network outputs and contributions to the complete gradient on the forward pass. The two techniques are demonstrated by being used to train the given network for talker-dependent discrimination of /b/, /d/, and /g/ in the context of a following /i/, /a/, or /u/. Consonant discrimination was as high as 98% on test syllables.
Surface waves at an interface between air and an air-filled poroelastic ground
Authors: Attenborough Keith , Chen Yu
Published: October 2005

Using a modified Biot theory, employing open pore boundary conditions at the interfaces, and by seeking plane-wave solutions, dispersion equations are derived for a rigid porous half-space, for a poroelastic half-space, and for a layered poroelastic half-space. That for the rigid porous boundary has a single solution. Numerical search shows that, for parameter values characteristic of a dry soil, the dispersion equation for the interface between air and an air-filled poroelastic half-space has three possible solutions corresponding, respectively, to that for the rigid porous case, an air-coupled pseudo-Rayleigh wave, and a new fast surface wave with a speed slightly less than the bulk P-wave speed. The sensitivities of these three surface waves to porosity and elastic parameters are investigated. Of the solutions to the dispersion equation for a system consisting of a single poroelastic layer above a poroelastic half-space, with parameters typical of a dry soil, one is identifiable as an air-coupled pseudo-Rayleigh wave with a phase velocity near to the speed of sound in air. Slower and faster surface waves are predicted also on the layered system when the input parameters for the upper layer are relevant to either a soil or thick snow.
Detectability of interaural delays over select spectral regions: Effects of flanking noise
Authors: Trahiotis Constantine , Bernstein Leslie R.
Published: October 2005

Zurek [P. M. Zurek, J. Acoust. Soc. Am. Suppl. 1 78, S18 (1985)] noted what he termed ‘‘spectral dominance’’ in sensitivity to interaural delay for broadband stimuli. He found that interaural delays presented solely within high-frequency spectral regions were difficult, if not impossible, to detect in the presence of spectrally flanking, gated, diotic noise. In order to see if spectral dominance is a general result of the processing of interaural delays in broadband stimuli, similar experiments were conducted utilizing both gated and continuous flanking noises that were interaurally identical (diotic) or completely uncorrelated. Beyond replicating Zurek’s basic findings, the data strongly suggest that the processing of interaural delays was largely unaffected when the flanking sounds were continuous and diotic. When the flanking sounds were interaurally uncorrelated, sensitivity was affected, but not drastically, for both gated and continuous conditions. Consequently, it appears that any inability to cope with conflicting interaural cues across spectral regions may be observed only under restricted conditions.
A comparison among three measures of cross-spectral processing of amplitude modulation with tonal signals
Authors: Yost William A. , Sheft Stanley
Published: October 2005

Results were obtained from three paradigms used to study cross-spectral processing of envelope modulation [comodulation masking release (CMR), comodulation detection difference (CDD), and modulation detection interference (MDI)]. When tonal carriers separated by two octaves (flanking tone at 1000 Hz and target tone at 4000 Hz) were amplitude modulated at 20 Hz, there was no evidence of a CMR or CDD effect, but there was substantial MDI.
Determination of blocking locations and cross-sectional area in a duct by eigenfrequency shifts
Authors: Qunli Wu , Fricke Fergus
Published: October 2005

A theoretical determination of the location and size of blockages in the one-dimensional duct has been carried out. It is found that the blockage cross-section area function can be calculated from the measured eigenfrequencies obtained using two boundary conditions, i.e., closed–closed (or open–open) and closed–open ends. When the blockages are small, the area function of the blocked duct can be expressed as a one-dimensional spatial Fourier transform, whose spatial frequencies are related to the eigenfrequency shifts caused by the blockages in the duct. The method developed can be applied to the detection of the multiple blockages. The experimental results show that the accuracy of the calculated blockage area function is dependent on the number of the eigenfrequencies used. The agreements between the calculated blockage area and the actual blockage are excellent when the half-wavelength of the eigenfrequency used is greater than the length of the blockage.
Three-dimensional Green’s function for fluid-loaded thin elastic cylindrical shell: Formulation and solution
Authors: Felsen L. B. , Ho J. M. , Lu I. T.
Published: October 2005

This paper treats sound radiation from a time-harmonic point pressure source located either inside or outside a thin, homogeneous, infinitely long circular cylindrical elastic shell, which is immersed in different interior and exterior fluid media. This Green’s function problem is attacked by a combination of the method of separation of variables and the method of images applied to an infinitely extended azimuthal (φ) domain. The reduced one-dimensional problems in the cylindrical (r,φ,z) coordinates are solved by general spectral techniques in terms of one-dimensional characteristic Green’s functions gr, gφ, gz, which depend on one or both of the two complex spectral separation parameters (spatial wavenumbers) λ1 and λ2. While the one-dimensional problems in the φ and z domains are straightforward, the presence of the shell in the radial domain introduces substantial complexity. The solution is obtained by defining the discontinuities in the pressure and normal displacement across the shell via recourse to the dynamical equations of motion inside the shell. The synthesis problem is made unique through a complete analysis of the spectral singularities of gr,φ,z in their respective complex planes, which permits selection of appropriate integration contours. A host of alternative representations, whose choice (concerning utility) is motivated by the parameter range of interest, can be derived from the fundamental spectral form. This is addressed in a companion paper [Felsen et al., J. Acoust. Soc. Am. 87, xxx–xxx (1990)], which also treats asymptotic reductions that lead to a variety of ray acoustic and other fundamental wave processes.
Three-dimensional Green’s function for fluid-loaded thin elastic cylindrical shell: Alternative representations and ray acoustic forms
Authors: Felsen L. B. , Ho J. M. , Lu I. T.
Published: October 2005

In this paper, the general spectral integral form of the three-dimensional pressure Green’s function for a fluid-loaded thin elastic cylindrical shell [Felsen et al., J. Acoust. Soc. Am. 87, xxx–xxx (1990)] is reduced to furnish two alternative representations that emphasize propagation phenomena associated essentially with the radial–azimuthal (r,φ) and the radial–longitudinal (r,z) coordinates, respectively. For the former, a decomposition of the point source field into a continuum of linearly phased z-directed line sources defines the problem parametrization, whereas for the latter, the decomposition is into a discrete infinity of ring sources with azimuthally periodic (angular harmonic) linear phasing. The reduced forms obtained in this manner are then examined in appropriate parameter regimes. For external phenomena in the (r,φ)-favored formulation, asymptotics leads to ray acoustic interpretations for the total field in terms of the conventional incident and reflected waves, augmented by shell-guided creeping waves and leaky waves that are excited by phase matching on the shell surface, as well as trapped waves in the shell excited by evanescent tunneling from the source. The shell-guided ray fields, which represent quasicompressional, quasiflexural, and quasishear phenomena, exhibit anisotropic behavior. In parameter regimes that emphasize axial guiding along the shell and the interior fluid [favoring (r,z)], the trapped waves, which are less important for the external processes, become the dominant constituents.
Bubble noise spectra
Authors: Longuet-Higgins Michael S.
Published: October 2005

When bubbles are formed by the enclosure of pockets of air, they must first undergo extreme distortions before settling down into a spherical shape. In two recent papers [M. S. Longuet-Higgins, J. Fluid Mech. 201, 525–541 (1989); 201, 543–565 (1989)] it has been shown that the shape oscillations of bubbles will, at second order, contain radially symmetric ‘‘monopole’’ terms, having double the fundamental frequency. These terms can resonate with the radial, ‘‘breathing’’ mode to produce significant levels of sound in the ocean. In the present paper it is shown that any broad spectrum of bubble-generated sound may be expected to show peaks at the corresponding resonance frequencies. A first examination of the available oceanic data does indeed show evidence of such resonances, particularly at the even-numbered mode frequencies. The same mechanism may also help to explain certain resonances observed in laboratory experiments by Medwin and Beaky [J. Acoust. Soc. Am. 86, 1124–1130 (1989)].
Modal shading coefficients for high-resolution source depth localization
Authors: Yang T. C.
Published: October 2005

In this article the minimum variance principle is applied to the modal shading coefficients to improve source depth localization. It is shown that for a long, well-populated vertical array, the source depth localization function based on the minimum variance principle is approximately the same as the depth function based on normal mode theory. For a limited aperture vertical array, the modes are spatially undersampled. In this case, the modal shading coefficients based on the minimum variance principle are shown to significantly improve the depth resolution assuming sufficient signal-to-noise ratio. But, as the signal-to-noise ratio decreases, the depth resolution for the minimum variance case approaches the (conventional) modal beamformer result.
Nondestructive characterization of texture and plastic strain ratio of metal sheets with electromagnetic acoustic transducers
Authors: Kawashima Katsuhiro
Published: October 2005

All the lowest-order independent CODF (crystallite orientation distribution function) coefficients W400, W420, and W440 of rolled steel sheets, with thickness less than 1 mm, have been obtained nondestructively by using the known single-crystal elastic constants and the relative ultrasonic velocities measured with EMATs (electromagnetic acoustic transducers). The ultrasonic velocities of all the waves, longitudinal waves, shear waves propagating in the through thickness direction, and SH0 (shear horizontal) plate waves, were measured by the EMATs. No acoustic coupling medium was necessary, making possible quick, accurate, and reproducible measurements. It is shown that the CODF coefficients can be obtained as the solutions of three linear equations in which the measured relative ultrasonic velocities are included. There was an overall correspondence between the ultrasonic pole figures drawn using the obtained CODF coefficients and x-ray pole figures. All nine elastic constants of a steel sheet were also calculated. Average Young’s modulus Ē and planar variation in Young’s modulus dE calculated using the nine elastic constants were consistent with average plastic strain ratio r̄ and planar variation in plastic strain ratio dr, respectively, showing that the ultrasonic method here is well adapted for practical use.
The effect of fluid–structural coupling on sound waves in an enclosure—Experimental part
Authors: Pan Jie , Bies David Alan
Published: October 2005

The acoustic properties of individual normal modes in a rectangular panel–cavity system were investigated experimentally. The system consisted of a heavy five-sided concrete box closed on the sixth side with a test panel. Experimental evidence in this paper reveals the dependence of the modal decay time of sound waves in the enclosure upon the modal characteristics of the test panel, such as the modal coupling factors, resonance frequencies, and modal decay times. The results of experimental measurements are used to verify some previous theoretical predictions. The agreement between measured and calculated enclosure modal decay times shows that modal coupling theory can be used to evaluate the sound wave behavior in those enclosures in which the coupling between fluid-borne and structure-borne acoustical waves is modal and where the classical model based upon the locally reactive boundary assumption does not apply. The phenomenon of maximum sound energy absorption by the panel was also observed in the experiment.
The effect of ocean inhomogeneities on array output
Authors: Uscinski B. J. , Reeve D. E.
Published: October 2005

The performance of line arrays is significantly affected by the irregular spatial variations that develop in acoustic waves when they propagate in the ocean. A numerical technique that has been successful in simulating the spatial variations observed in ocean acoustic experiments has been used to study their effect on array performance. Analytical expressions, helpful for describing the output of an array in such a spatially varying sound field, have been derived on the basis of the parabolic second- and fourth-moment equations. The present paper is confined to treating vertically deployed arrays.
Doublet broadband cross detectors in the frequency domain
Authors: Williams Jack R. , Lauter Frederick B.
Published: October 2005

This paper defines the frequency domain implementation of several doublet cross detectors for broadband signals. The analytic correlator and the analytic coherence transform processes on real signals are introduced that have certain advantages as detectors over their real forms. The detectability of these cross detectors is predicted in comparison to optimal detectors.
Psychoacoustical and ear canal cancellation of (2f1−f2)-distortion products
Authors: Zwicker Eberhard , Harris Frances P.
Published: October 2005

Level and phase of the (2f1−f2)-difference tone were measured as a function of primary-tone level using the psychoacoustical method of cancellation and the objective method of emission cancellation for four frequency separations of f1=1620 Hz and f2 in four subjects. Differences between hearing- and emission-cancellation levels ranged from 60–33 dB as Δf=f2−f1 increased from 180 to 432 Hz. For smaller separations of the primaries, phase changes for emission cancellation covered a wide range and had sharp ‘‘steps,’’ whereas for hearing cancellation, the phase varied only slightly. With wider separations of the primaries, the phase became more varied for hearing cancellation and more homogeneous for emission cancellation. Both emission- and hearing-cancellation level functions were nonmonotonic as a function of constant SL1 and varied SL2. Remarkable phase shifts always appeared near minima in level at all separations of the primaries for emission cancellation. Four sources may be contributing to the differences in results: (a) the frequency-dependent attenuation of the middle-ear transfer function, (b) the frequency-dependent mismatch of the acoustical impedances at the eardrum, (c) the frequency dependence of the microphone’s sensitivity mounted within the probe, and (d) the different reaction of active nonlinear cochlear processes on the hearing- and emission-cancellation tones.
Jaw and lip movements of deaf talkers producing utterances with known stress patterns
Authors: Tye-Murray Nancy , Folkins John W.
Published: October 2005

This investigation determined whether prelingually deaf talkers could correctly produce stressed and unstressed syllables across known changes in stress patterning and phonetic composition. Three deaf and three hearing adults spoke sets of homogeneous syllable strings with stress patterns that they could tap successfully with a finger. Strain gauge transduction of lower lip and jaw movement indicated that both deaf and hearing subjects produced different displacements and durations for the stressed and unstressed syllables, regardless of the stress pattern. Jaw movement did not become more variable with changes in phonetic composition of the syllables. The results show no evidence that motoric abilities (as assessed in lip and jaw movements) limit deaf talkers in producing desired stress patterns.
Context effects in phoneme and word recognition by young children and older adults
Authors: Nittrouer Susan , Boothroyd Arthur
Published: October 2005

Perception is influenced both by characteristics of the stimulus, and by the context in which it is presented. The relative contributions of each of these factors depend, to some extent, on perceiver characteristics. The contributions of word and sentence context to the perception of phonemes within words and words within sentences, respectively, have been well studied for normal, young adults. However, far less is known about these context effects for much younger and older listeners. In the present study, measures of these context effects were obtained from young children (ages 4 years 6 months to 6 years 6 months) and from older adults (over 62 years), and compared with those of the young adults in an earlier study [A. Boothroyd and S. Nittrouer, J. Acoust. Soc. Am. 84, 101–114 (1988)]. Both children and older adults demonstrated poorer overall recognition scores than did young adults. However, responses of children and older adults demonstrated similar context effects, with two exceptions: Children used the semantic constraints of sentences to a lesser extent than did young or older adults, and older adults used lexical constraints to a greater extent than either of the other two groups.
Temperature elevation generated by a focused Gaussian ultrasonic beam at a tissue–bone interface
Authors: Wu Junru , Du Gonghuan
Published: October 2005

When a focused Gaussian ultrasonic beam in soft tissue normally impinges on the boundary of a contiguous bone, reflection and transmission occur. Taking account of the reflection, the steady-state temperature elevation along the beam axis for this case was calculated. The effect of perfusion is also included.
Wave equation for sound in fluids with unsteady inhomogeneous flow
Authors: Pierce Allan D.
Published: October 2005

An approximate wave equation is derived for sound propagation in an inhomogeneous fluid with ambient properties and flow that vary both with position and time. The derivation assumes that the characteristic length scale and characteristic time scale for the ambient medium are larger than the corresponding scales for the acoustic disturbance. For such a circumstance, it is argued that accumulative effects of inhomogeneities and the ambient unsteadiness are satisfactorily taken into account by a wave equation that is correct to first order in the derivatives of the ambient quantities. A derivation that consistently neglects second- and higher-order terms leads to a concise wave equation similar to the familiar ordinary wave equation of acoustics. The wide applicability of this equation is established by showing that it reduces to previously known wave equations for special cases and by showing, with the eikonal approximation, that it yields the geometrical acoustics equations for ray propagation in moving inhomogeneous media.
Reflection of elastic plane waves at a planar achiral–chiral interface
Authors: Lakhtakia Akhlesh , Varadan Vijay K. , Varadan Vasundara V.
Published: October 2005

In an isotropic, noncentrosymmetric (chiral) elastic solid, the displacement field u has to be supplemented by the independent microrotation field φ. Since such a medium is mirror asymmetric or chiral, six different wavenumbers are possible: of these, two represent longitudinal fields, and the remaining four are circularly polarized. This paper is concerned with the scattering of elastic plane waves by a planar interface between an achiral elastic solid half-space and a chiral elastic solid half-space.
Mechanical characterization of microparticles by scattered ultrasound
Authors: Roy Ronald A. , Apfel Robert E.
Published: October 2005

A technique for determining the compressibility and density of individual microparticles in suspension is described. The particles have diameters on the order of 10 μm. Ultrasonic tone bursts of 2-μs duration and 30-MHz center frequency scatter from individual particles as they traverse the confocal zone of two transducers. The resulting scattered tone bursts are detected at 90° and 180° (backscattering). The received rf signals are demodulated, peak detected, digitized, and stored in computer memory. Using Rayleigh scattering theory, the compressibility and density of a particle can be computed given knowledge of the particle size and host fluid properties. Results of experiments with latex microspheres are presented and compared with calculations based on long-wavelength (Rayleigh) and elastic scattering theory.
Active control of low-frequency random sound in enclosures
Authors: Joplin P. M. , Nelson P. A.
Published: October 2005

This paper evaluates the degree to which active methods can be used to reduce the level of sound-pressure fluctuations in an enclosure excited at low frequencies by a stationary random source. The spectral density of the total acoustic potential energy in the enclosure is used as a cost function for evaluating the global effectiveness of the technique. The enclosure is controlled by a secondary source whose output is constrained to act causally with respect to the primary source. The optimal causal filter relating the secondary source output to the primary source output can be deduced using classical Wiener filter theory. A numerical approach is adopted for the solution of the resulting Wiener–Hopf integral equation. It is shown that the resonances of the enclosure can be successfully suppressed by the action of the active control.
Eccentric dipole sources in fluid-filled boreholes: Numerical and experimental results
Authors: Leslie H. D. , Randall C. J.
Published: October 2005

A frequency-wavenumber (ω−k) representation is given for the response of eccentric multipole sensors in a fluid-filled borehole. Specializing to eccentric dipole sensors, synthetic time-domain waveforms from an array of receivers deployed along the axis of the borehole are displayed for a range of eccentricity magnitude and orientation, formation slowness, and borehole radius. Flexural wave slowness estimates within several frequency bands are extracted from the synthetic waveforms using a semblance technique. For eccentricity small relative to the borehole radius, the character of dipole waveforms and the estimated flexural slowness are little changed. When the eccentricity is a substantial fraction of the borehole radius, flexural wave amplitude is greatly increased, and strong nonmonotonic trends are introduced due to interference with other modes. If eccentricity is not parallel to the transmitting dipole axis, substantial signals are detected on cross-dipole receivers, perpendicular to that of the transmitting dipole. Eccentricity effects decrease with frequency. Even for large eccentricity, flexural slowness estimates are affected only slightly. Scaled laboratory experiments confirm the numerical results. Comparison of the experimental and numerical waveforms is made for both centered and eccentric dipoles in several model formations. The predicted increase and nonmonotonic variation of flexural wave amplitude versus receiver offset for eccentric sensors is observed. Experimental and numerical waveforms overlay with excellent agreement.
Boundary conditions for the parabolic equation in a range-dependent duct
Authors: Abrahamsson Leif , Kreiss Heinz-Otto
Published: October 2005

The parabolic wave equation in a range-dependent duct with a rigid bottom is considered. The range dependence will introduce amplitude errors in addition to the usual phase error of the local modes. It is shown that the amplitude error increases by local mode angle and slope of the bottom, and is inversely proportional to the depth. Imposing the vanishing of the normal derivative of the pressure at the bottom, which is the physically correct boundary condition, might also lead to ill conditioning of the parabolic model. Various ways to replace the boundary condition ∂u/∂n=0 are discussed, and their accuracy is assessed both numerically and theoretically.
An acoustic backscattering technique for the detection of transient cavitation produced by microsecond pulses of ultrasound
Authors: Roy Ronald A. , Madanshetty Sameer I. , Apfel Robert E.
Published: October 2005

An acoustic backscattering technique for detecting transient cavitation produced by 10-μs-long pulses of 757-kHz ultrasound is described. The system employs 10-μs-long, 30-MHz center frequency tone bursts that scatter from cavitation microbubbles. Experiments were performed with suspensions of hydrophobic polystyrene spheres in ultraclean water. Transient cavitation threshold pressures measured with the active cavitation detector (ACD) were always less than or equal to those measured using a passive acoustic detection scheme. The measured cavitation thresholds decreased with increasing dissolved gas content and increasing suspended particle concentration. Results also show that ultrasonic irradiation of the polystyrene sphere suspensions by the ACD lowered the threshold pressure measured with the passive detector. A possible mechanism through which suspensions of hydrophobic particles might nucleate bubbles is presented.
Underwater acoustic signal analysis with wavelet process
Authors: David Pascal M. , Chapron Bertrand
Published: October 2005

A recently developed mathematical method (wavelet transform) of signal processing has provided potential new options for underwater signal study. It is a time-frequency mathematical process that analyzes high-frequency signals. Signal frequency instabilities are identified, calculated, and compared with the chosen wavelet. The mathematical process is applied to underwater acoustic signals received by sonar. It is shown how this mathematical process analyzes: (1) a pulse emitted by a source with part of the return signal; (2) a sonar signal that travels through important subsurface biological sea realms; and (3) an echo coming from a target [a CTD (conductivity, temperature, depth) Guildline] located at a depth of 800 m.
Informational processing of complex sound. II. Cross-dimensional analysis
Authors: Lutfi Robert A.
Published: October 2005

A series of experiments investigated listeners’ ability simultaneously to process information across different acoustic dimensions. On each trial, the listener heard a pair of brief n-tone sequences (n=1 to 12). The frequency, intensity, and duration of each tone in the sequence varied randomly from trial to trial. On average, the values of these three parameters were greater for one sequence, the target, than the other, the nontarget. The listener’s task was to identify the target on each trial. For an ideal observer in this task, d′ performance grows as the square root n. Obtained d′ grew at a rate slightly less than the square root of n. Close to cube root of n growth was observed when the average difference occurred in only one of the three tone parameter values within a block of trials. Although performance fell short of ideal, optimum weights were consistently given to each tone and each parameter. The results are consistent with a model in which performance depends predominantly on the information content of the sounds regardless of how the information is ‘‘packaged’’ in the stimulus. Transmitted information is estimated to be 0.9–2.0 bits within a single acoustic dimension, 2.1–3.0 bits when distributed across dimensions.
Temporal window shape as a function of frequency and level
Authors: Plack Christopher J. , Moore Brian C. J.
Published: October 2005

In an earlier article [Moore et al., J. Acoust. Soc. Am. 83, 1102–1116 (1988)], preliminary work on the temporal-window model of temporal resolution in the auditory system was described. The temporal window is conceived of as a temporal integrator that slides in time and that is implemented as an intensity-weighting function. The shape of the temporal window was estimated by measuring the threshold for a brief sinusoidal signal presented in a temporal gap between two bursts of noise as a function of the duration of the gap and the position of the signal within the gap. In this paper, a much more thorough examination of the effects of level and frequency on the shape of the window is presented, using the same basic technique. Temporal window shapes were measured at four different frequencies (300, 900, 2700, and 8100 Hz) and at three different masker levels covering a 20-dB range at each frequency. The shape of the temporal window was well described by modeling each side as the sum of two rounded-exponential (roex) functions. The equivalent rectangular duration (ERD) of the window decreased from about 13 to 9 ms as the center frequency increased from 300 to 900 Hz, but decreased only slightly, to 7 ms, as the center frequency increased to 8100. The greater ERD at 300 Hz does not seem to be explicable in terms of ‘‘ringing’’ in the auditory filter. The ERD decreased somewhat with increasing level, for example, having a value of about 10 ms at 2700 Hz with a 20-dB masker spectrum level and about 7 ms with a 40-dB masker spectrum level.
Vibrotactile temporal gap detection as a function of age
Authors: Van Doren Clayton L. , Gescheider George A. , Verrillo Ronald T.
Published: October 2005

The ability of subjects to detect temporal gaps between bursts of sinusoids or bursts of bandlimited noise was measured to evaluate the phenomenon of tactile ‘‘sensory persistence’’ in older persons. Vibratory stimuli were delivered to the right thenar eminence of 27 subjects ranging in age from 8–75 years. The subjects’ task was to detect the presence of a silent interval or ‘‘gap’’ between flanking 350-ms vibrotactile stimuli. The gap-detection threshold, expressed as the amplitude of vibration relative to the absolute detection threshold, decreased as the gap duration increased and was higher for gaps in noise than for gaps in sinusoids. The threshold for detecting short gaps increased with age for noise stimuli, but not for sinusoidal stimuli. Furthermore, the gap-detection threshold recovered more rapidly in older subjects for noise stimuli, but less rapidly in older subjects for sinusoidal stimuli. Because of these differences, it appears that the effects of age on gap detection cannot be due to a simple increase in sensory persistence, but may be due to multiple processes.
Acoustic recognition of voice disorders: A comparative study of running speech v
e
r
s
u
s sustained vowels
Authors: Klingholtz F.
Published: October 2005

The signals of running speech and sustained vowels of normals and subjects suffering from dysphonia were analyzed statistically with respect to the signal-to-noise ratio (SNR). The distribution of the SNR measured in multiple overlapping frames in the speech signal was described by a linear combination of the distribution frequencies for SNR=0 dB, 0 dB<SNR<15 dB, and SNR≥15 dB. The values of the linear combination, the SNR of the vowels, and clinical assignment of the voices to normal and pathologic populations based on laryngoscopic and stroboscopic investigation parameters were used to compare the different evaluations of the voices. The SNR distribution in speech remained stable over signal lengths of more than 30 s. The correlation coefficient between the SNR measure for running speech and the SNR of sustained vowels amounted to only 0.63. The error rate in the discrimination between normal and dysphonic voices amounted to 22.6% in application to sustained vowels and 5.6% when the SNR distribution was used. Possible reasons for the observed discrepancies are discussed, and the results are compared to those of other studies.
Relational spectral features for place of articulation in nasal consonants
Authors: Seitz Philip F. , McCormick Marianne M. , Watson Ian M. C. , Bladon R. Anthony
Published: October 2005

Much recent research on acoustic cues for consonants’ places of articulation has focused upon the nature of the rapid spectral changes that take place between signal portions corresponding to consonantal closure and adjacent vowels. The study reported here builds on the foundation laid by earlier studies that have explored techniques for representing spectral change and for classifying place of articulation of nasal consonants using features extracted from rapid spectral changes that take place over murmur-to-vowel transitions. A new procedure is reported that avoids the use of predetermined absolute frequency bands in deriving parameters of spectral change in nasals. In experiments using the speech of 20 female and 20 male talkers, in a variety of physical and perceptual spectral scalings, application of the new procedure results in 77% correct classification of place of articulation of syllable-initial nasals and 51% correct classification of place of articulation of syllable-final nasals (for which there is a three-way contrast). Tested on the same data, a technique using predetermined absolute frequency bands produced 72% correct classification of syllable-initial nasals.
Algorithms for separating the speech of interfering talkers: Evaluations with voiced sentences, and normal-hearing and hearing-impaired listeners
Authors: Stubbs Richard J. , Summerfield Quentin
Published: October 2005

Two signal-processing algorithms, derived from those described by Stubbs and Summerfield [R. J. Stubbs and Q. Summerfield, J. Acoust. Soc. Am. 84, 1236–1249 (1988)], were used to separate the voiced speech of two talkers speaking simultaneously, at similar intensities, in a single channel. Both algorithms use fundamental frequency (F0) as the basis for segregation. One attenuates the interfering voice by filtering the cepstrum of the signal. The other is a hybrid algorithm that combines cepstral filtering with the technique of harmonic selection [T. W. Parsons, J. Acoust. Soc. Am. 60, 911–918 (1976)]. The algorithms were evaluated and compared in perceptual experiments involving listeners with normal hearing and listeners with cochlear hearing impairments. In experiment 1 the processing was used to separate voiced sentences spoken on a monotone. Both algorithms gave significant increases in intelligibility to both groups of listeners. The improvements were equivalent to an increase of 3–4 dB in the effective signal-to-noise ratio (SNR). In experiment 2 the processing was used to separate voiced sentences spoken with time-varying intonation. For normal-hearing listeners, cepstral filtering gave a significant increase in intelligibility, while the hybrid algorithm gave an increase that was on the margins of significance (p=0.06). The improvements were equivalent to an increase of 2–3 dB in the effective SNR. For impaired listeners, no intelligibility improvements were demonstrated with intoned sentences. The decrease in performance for intoned material is attributed to limitations of the algorithms when F0 is nonstationary.
A study of the cavity resonances of a violin and their effects on its tone and playing qualities
Authors: Hutchins Carleen M.
Published: October 2005

This work provides experimental evidence showing that the motions of the air inside the violin cavity and through the f holes have important effects on the tone and playing qualities of the instrument. Experiments are described in which the cavity resonances of a violin with 65 holes in its ribs are explored and altered, and their effects charted without markedly distorting its corpus resonances. Response curves show the changes in the resonance structure when all holes are open, all plugged with corks, and all plugged with foam. Performance tests indicate the changes in tone and playing qualities under the same three conditions. Findings are reported using internal gas to lower the cavity modes and ‘‘buried in sand’’ to inhibit the corpus modes. Results compare favorably with theoretical modeling of the effects of these changes on the two lowest cavity modes [E. A. G. Shaw, J. Acoust. Soc. Am. 87, XXX–XXX (1990)].
Modal vibration control of large ultrasonic tools with the use of wave-trapped horns
Authors: Adachi Kazunari , Ueha Sadayuki
Published: October 2005

A method for modal vibration control of elastic systems using additional vibrators called ‘‘wave-trapped horns’’ is proposed. Experimental verification of the method has been done for many large ultrasonic tools whose shapes are often adopted in ultrasonic plastic welding. Uniform amplitude distributions have been realized at the radiating faces of the tools. Effects of both the thickness and the number of the horns have also been investigated, with bending vibration of the horns found to diminish the effectiveness of the method. The validity of the method is finally confirmed under certain conditions.
Auditory correlates of perceived mallet hardness for a set of recorded percussive sound events
Authors: Freed Daniel J.
Published: October 2005

A psychophysical investigation of timbre was undertaken with the intent of deriving quantitative results that could be useful in musical applications. Recordings of metal objects being struck with percussion mallets were rated by subjects on a unidimensional perceptual scale of perceived mallet hardness. Four acoustical parameters of the attack portion (first 325 ms) were defined and evaluated as predictors of perceived mallet hardness rating. To measure these parameters, a critical-band filter bank was employed. Two curves were extracted from the filter-bank output: (1) spectral level (log of area under spectrum) over time, and (2) spectral centroid over time. For each curve, two parameters were measured: the mean and the slope of the spectral level curve, and the mean and the time-weighted average of the spectral centroid curve. Multiple regression analysis was used to relate the perceptual ratings to these four acoustical parameters, and a good fit was achieved (multiple R-squared=0.725, F=1135.8, p<0.01). The resulting function is suitable for quantitatively predicting the perceptual dimension of perceived mallet hardness.
Attenuation in a saddle-point analysis of the reflected acoustic field
Authors: Tindle C. T. , Plumpton N. G.
Published: October 2005

Bottom attenuation is included in a saddle-point analysis of the acoustic field formed by reflection of sound at the interface between two fluids. The loci of the saddle points as a function of range are substantially changed when attenuation is included, but previous approximate analytic expressions in terms of the saddle points can still be used and give a good approximation to the field. The suggestion made elsewhere that the inclusion of attenuation simplifies a beam displacement analysis of bottom reflection is shown to lead to poor results.
Acoustic navigation of a large-aperture array
Authors: Sotirin Barbara J. , Hildebrand John A.
Published: October 2005

Acoustic travel time measurements were used to navigate the elements of a large-aperture (900 m) acoustic array. Array navigation system performance was evaluated during a vertical deployment in the northeast Pacific from the Research Platform FLIP. A network of bottom-moored acoustic transponders were interrogated from FLIP and their 12-kHz replies were detected by receivers at 75-m intervals along the array. A nonlinear least-squares algorithm was used to estimate FLIP and array element positions from the travel time measurements. The FLIP positions derived from this procedure agreed with positions obtained from global positioning system (GPS) satellite navigation to within a 10-m rms error. Navigated positions for FLIP were internally consistent with a 0.5-m mean rms error and standard deviation of 1.1 m, and, for an array element, were consistent with a 2.8-m mean rms error and standard deviation of 0.8 m. The resulting time series of array and FLIP motions were analyzed with respect to wind, tidal, and internal wave forcing functions. Wind and tidal forcing had the greatest influence on FLIP motion, whereas array motion was governed by FLIP movement, tides, and higher frequency sources. Low-frequency array motion, with periods on the order of hours, was a result of FLIP towing the array over a horizontal range of 300 m in response to the wind and the semidiurnal tidal oscillations; the array remained within a 30-m horizontal range of FLIP’s position. Higher frequency array motion had apparent internal wave and surface-coupled components. The array shape was primarily straight and nearly vertical, to within approximately a 2° tilt, responding as a simple pendulum with small displacements.
Sound scattering of a spherical wave incident on a cylinder
Authors: Li Tai-bao , Ueda Mitsuhiro
Published: October 2005

The problem of the scattering of a spherical acoustic wave by an elastic circular cylinder of infinite length is investigated theoretically in this paper. In a cylindrical coordinate system, the mathematical form of a spherical wave is similar to that of a plane wave. Thus it is not necessary to solve the relevant differential equations and boundary conditions. An exact solution to the present problem can be directly formulated by using the already known solution for plane-wave incidence. This solution is expressed by an integral, which always involves a numerical treatment. The scattered pressure is calculated for an aluminum cylinder in water. A detailed discussion of the results reveals the features of the scattering of a spherical wave.
Elastic wave radiation and diffraction of a piston source
Authors: Tang X. M. , Toksöz M. N. , Cheng C. H.
Published: October 2005

The radiation of an elastic field from a plane piston source is formulated using the representation theorem, in which the Green’s function for an elastic half-space is employed. On the basis of this formulation, the radiated elastic wave field for both compressional and shear cylindrical wave sources is derived. The diffraction of elastic waves incident on a receiver that has the same geometry as that of the source and is coaxially aligned with it is studied. The authors present a procedure in which both numerical and asymptotic techniques are employed to allow them to evaluate the diffraction effects in any frequency range of interest. The elastic diffraction is compared with the acoustic diffraction and it is discovered that they differ only in the nearfield of the piston source because of the coupling between shear and compressional components in the elastic case. In the farfield, however, the elastic diffraction approaches the acoustic diffraction. With the help of ultrasonic laboratory measurements, the authors test the theoretical results and find that the theory and experiments agree well for the elastic solution. An important application of the results of this study is in attenuation measurements using pulse propagation techniques, where spectral ratio of a sample relative to a standard sample, or ratio of samples of the same material but different length is used. In the former case, the attenuation can be overestimated. While in the latter case, the attenuation can be significantly underestimated, if corrections for diffraction effects are not made.
An aid in the numerical integration for i
n s
i
t
u acoustic impedance and absorption coefficient measurements
Authors: Champoux Yvan , Richarz Werner G.
Published: October 2005

A method to measure in situ the surface acoustic impedance of a material was recently introduced by Allard and Champoux [Noise Control Eng. J. 32 (1), 15–23 (1988)]. It requires the utilization of a numerical method based on the well-known fixed-point method. This numerical method is shown to yield sufficiently precise results regardless of the value of the surface impedance. Using an alternative expression for the complex integral that is evaluated numerically, values for the upper integration and summation limits are determined to make the in situ method viable in practice.
Identification of the acoustic ocean transfer function in the Tyrrhenian Sea. I: Statistical considerations
Authors: Fradkin Larissa Ju.
Published: October 2005

In the process of statistical analysis of signature/response pairs collected in the Tyrrhenian Sea during the Napoli 85 Trial, a novel method has been developed for identifying the ocean transfer function (OTF). This method allows for the first-order diffraction effects, multipath propagation, and the signal bandwidth narrow compared to the bandwidth of the OTF. It is based on deconvolution of the received pulse with the signature of the emitted broadband pulse. The deconvolution is carried out under several physically reasonable constraints. One of them restricts the method to situations when no phase reversal takes place along any of the paths or, alternatively, when all the paths deliver the signal with a reversed phase. When applied to the Napoli 85 data, the method appears to indicate the presence of two direct (deep sea) paths between the experimental source and receiver with quite distinct times of propagation. In this paper, exploratory statistical data analysis is used to validate both the method and the underlying constraints.
Estimation of dorsal aspect target strength of deep-water fish using a simple model of swimbladder backscattering
Authors: Do Manh A. , Surti Aspi M.
Published: October 2005

A practical model for estimating target strength of gas-filled swimbladdered fish is described using the scattering function of a finite cylinder. Two equivalent cylinders are derived from measurements of swimbladder length, surface area, and volume. The scattering functions of both equivalent cylinders were tested using data available for gadoids, then applied in the estimation of target strength of deep-water hoki (Macruronus novaezelandie). Molds of 23 hoki swimbladders were constructed for measurements of their internal dimensions. Estimates of target strength using the scattering function of the equivalent surface area cylinder agree closely with estimates by other methods for gadoids. Estimates using the scattering function of the equivalent volume cylinder are lower, but approach the former estimates when the swimbladders are fully inflated. The advantage of using the latter method is the simplicity in measuring the swimbladder volume. The dorsal aspect target strength of hoki were estimated at four frequencies, 38, 49, 70, and 120 kHz for several distribution functions of fish tilt angle.