bluuebunny/crossref_metadata_2025 huggingface dataset:
Scattering of ultrasonic waves by cotton fibers
Authors: Breazeale M. A.
Published: October 2005

A tone burst of ultrasonic waves in air is scattered on passing through a pad of fibers. The distribution of spatial frequencies within the tone burst is found to be affected by the physical characteristics of the fiber used, and becomes a means of identifying fibers. Known cotton fiber samples whose properties have been studied previously by x-ray diffraction are used to scatter 1-MHz ultrasonic waves in air. Spectrum analysis of the transmitted tone bursts produces characteristic spectra which correlate well with the x-ray diffraction results. Reliable tests can be made with samples weighing as little as 0.36 g.
Dynamic and perceptual constraints of loud speech
Authors: Schulman Richard
Published: October 2005

In an investigation of the production of loud speech, it is found that, in comparison with normal speech, these productions are characterized by a substantially lowered jaw position for all vowels. On the basis of these results, we examine whether, for loud speech, speakers maintain tongue constrictions typical for normal vowel production in spite of the lowered jaw position, or if the tongue follows the jaw using constrictions atypical for the particular vowel. Acoustic analyses of the loud tokens show an increase in F1, thus indicating a lowering of the tongue. Tests show, however, that listeners perceive the intended vowel quality, and not that which might be inferred from the loud formant values. The characteristics of the loud speech targets will be discussed in light of the dynamic constraints of the articulatory system and the perceptual constraints set by the listener.
Articulatory movements—Icebergs revisited
Authors: Fujimura O.
Published: October 2005

In previous meetings, we discussed a hypothesis that there are relatively robust parts of CV and VC (or, more generally, any demisyllabic) movement patterns for the peripheral articulators, that are directly relevant to the place-specifying consonants involved. This paper attempts to clarify the limitation of the phonetic environments in which such an “iceberg” invariance is maintained, to define the crucial and robust articulatory dimensions from this point of view, and to examine the compatibility of this hypothesis with other models of articulatory movements. It is shown that extremely fast (probably inexact) utterances can introduce a remarkable difference in movement patterns, particularly in repeated utterances, whereas rather extreme contrastive emphasis conditions that considerably alter vowel gestures do not. A comparison between isolated words and sentence-embedded words seems to support the invariance notion.
On velopharyngeal articulation in the origin of human CV contrasts
Authors: Bauer Harold R.
Published: October 2005

The origin of human CV contrasts from nonhuman primate sound systems is hypothesized to be, in part, dependent upon effective nasal port valving due to velopharyngeal articulation. Common chimpanzee sound acoustics and associated oral-facial movements were studied. Compared with obstruents found in human infants, chimpanzee sounds suggest no similar post-velum evidence of obstruent production. An ethologic model of phonetic development based upon the production of sensorimotor contrasts [Bauer, J. Acoust. Soc. Am. Suppl. 1 75, S45 (1984)] was used to detail the hypothetical phylogenetic and developmental significance of nasal port articulation in the origin of human speech sound contrasts. Consistent with the hypothesis, the lack of comparative evidence for chimpanzee post-velum obstruent sounds supports the significance of velopharyngeal articulation in the origin of human obstruent-vowel contrasts.
Ambient noise directionality at two locations in the Gulf of Mexico
Authors: Wagstaff Ronald A.
Published: October 2005

Low-frequency ambient noise directionality measurements were made by a towed line array in the Gulf of Mexico at two different sites. The first site was seaward of the continental shelf and north of the Yucatan Peninsula. The second site was near the entrance to the Gulf of Mexico. The presence of a shallow shelf at the first site effectively shields the array from long-range acoustic propagation from the south. This shielding, combined with favorable propagation conditions and high-density shipping to the north, is responsible for the high degree of anisotropy in the measured ambient noise horizontal directionality pattern at the first site. The measured ambient noise directionality pattern at the second site shows the strong influence of the shipping entering and exiting the Gulf of Mexico. Because the acoustic propagation conditions and the shipping in the Gulf of Mexico are approximately repeatable annually, these two directionality measurements are considered to be good estimates for the ambient noise for future years. A discussion of the horizontal directionality as well as additional ambient noise statistics for the two sites will be given.
Nonlinear viscous effects arising near a boundary discontinuity
Authors: Thompson Charles
Published: October 2005

The problem of nonlinear viscous flow generated by an acoustic wave traveling in proximity to a rigid boundary having a rapid variation in shape will be examined. Special attention will be given to the problems of acoustic streaming and instability in the Stokes boundary layer. The acoustic particle velocity amplitude for which instability is observed corresponds to the case where η2R1/2/S2 = O(1). Below this amplitude threshold, acoustic waves generate time-average motion which is called acoustic streaming. Preliminary results show that the boundary geometry plays a major part in the instability mechanism in that an inflection point in the wall geometry gives rise to a bifurcation point according to linear theory. This state of affairs is in marked contrast to Stokes layers generated over flat boundaries, which exhibit no such bifurcation point. By virtue of the compressible character of the base flow, the characteristic acoustic scale (namely, the acoustic wavelength) does influence the spatial development for the vortical disturbance field. Therefore, an analysis of the relative influence of geometric and acoustic length scales in the development of the distribution field will also be presented.
The development of an anechoic termination for thin walled shell structure
Authors: Schapley R. F. , Cuschieri J. M. , Dunn S. E.
Published: October 2005

In a series of experiments on the flow of vibrational energy in pipe structures and on the coupling between the structure and the internal medium during the vibration of the outer shell, it was desired that a structure with similar characteristics to that of an infinite structure be developed. That is, a pipe structure with anechoic terminations was required. It was decided that the best approach would be to embed the pipe structure ends in sand. The required length of sand coverage was obtained through a series of experiments. The effect of different configurations was studied by measuring the loss factor of the structure. The results obtained showed that the sand termination had a significant effect on the longitudinal modes of the pipe although this effect was independent of the coverage area. However, the circumferential modes were not effected at all. In addition, the effect of sand coverage over the ends of the pipe was investigated. It was shown that having the ends of the pipe open to the air or closed by sand had little effect on the modes of vibration of the structure.
Sonically produced heat in a fluid with bulk viscosity and shear viscosity
Authors: Nyborg Wesley L.
Published: October 2005

When a sound field is set up in an absorbing medium, heat is produced in a spatial pattern which, in general, depends on the absorption mechanism. Consider a fluid with bulk viscosity coefficient B′ and shear viscosity coefficient η. In a continuous traveling plane wave the time-averaged volume rate of heat production 〈qv〉 at any point is proportional to the absorption coefficient α which, in turn, is proportional to (B′ + 4η/3). In a more general field, the quantity 〈qv〉 can be calculated from a dissipation function if the components ui of the velocity are known as functions of coordinates xj. For a continuous field one obtains 〈qv〉 in the form (B′T1 + ηT2), where T1 and T2 are two different quadratic combinations of derivatives of the type ∂ui/∂xj. Applying this expression to several examples (crossed plane waves, nearfield of a piston source) it is found that for a given value of a the spatial distribution of 〈qv〉 is strongly dependent on the relative values of the coefficients B′ and η. [Work supported by NIH Grant GM 08209.]
Discrimination of spectral density
Authors: Hartmann W. M. , McAdams Stephen
Published: October 2005

Experiments were performed to determine the ability of human listeners to discriminate between a sound with a large number of spectral components in a band, of given characteristic frequency and bandwidth, and a sound with a smaller number of components in that band. A pseudorandom placement of the components within the band ensured that no two sounds were identical. The data suggested that discrimination is primarily based upon the perception of temporal fluctuations in the amplitude envelope of the sound and secondarily upon a steady-state tone color. Experiments using clusters of complex sounds showed that listeners are able to use the information in harmonic bands to discriminate spectral density. [Work partially supported by NIH, the NSF, and the CNRS.]
Cues in the perception of infinitely clipped speech
Authors: Kahn Daniel
Published: October 2005

“Infinitely clipped” (“IC”) speech is surprisingly intelligible [Licklider and Pollack, J. Acoust. Soc. Am. 20, 42–51 (1948)]. Because infinite clipping so severely distorts the speech spectrum, it is sometimes speculated that a time-domain similarity between natural and IC speech—precise identity of zero-crossing locations—might account for the latter's intelligibility. This hypothesis has practical implications (should speech recognition algorithms look beyond power spectra?) and theoretical ones [cf. Scott, J. Acoust. Soc. Am. 60, 1354–1365 (1976)]. However, the hypothesis would be refuted if it turned out that the small amount of residual similarity between the power spectra of the original and IC signals could alone account for the observed intelligibility. Three types of stimuli—natural vowels, /p,t,k/ in natural-sentence context, and synthetic vowels—were infinitely clipped (“IC stimuli”), then subjected to transformations which preserved the power spectrum but grossly distorted the phase spectrum, thereby destroying the original zero-crossing information. These transformed IC stimuli were no less intelligible than the unaltered IC stimuli, strongly suggesting that power spectrum rather than zero-crossing cues are responsible for IC-speech intelligibility. Further, constant-parameter, synthetic-vowel inteiligibility decreased dramatically upon clipping, natural-vowel intelligibility relatively little, demonstrating the usefulness of spectral change and/or prosodic cues in the absence of accurate formant information.
Application of an adaptive auditory model to speech recognition
Authors: Cohen Jordan R.
Published: October 2005

One approach to designing signal processors for speech recognition has been to model the mammalian auditory system. Most designs have not attempted to capture the time-varying nature of the system, but have focused on the psychophysical aspects of critical bandwidth and loudness estimation. The IBM 5000-word speech recognition system [Bahl et al., IEEE Trans. Pattern Anal. Machine Intell. PAMI-5, 179–190 (1983)] uses an auditory model in which psychophysical critical-band tuning and loudness estimation are combined with a firing-rate model patterned after that of Schroeder and Hall [J. Acoust. Soc. Am. 55, 1055–1060 (1974)]. The signal processing system consists of a critical-bandwidth filter bank, loudness estimation (intensity to the 1/3 power), and a reservoir-type firing-rate model with one internal state for each band. This model enhances transient events in the auditory signal, and causes rapid stimulus offsets to be marked by outputs smaller than the resting rate. The use of this auditory model in the IBM system produces a 4.4% error rate on a standard corpus of four speakers, while the previous filter-bank signal processor produces 7.4% errors on the same data.
Sound intensity measurement in the air and on the surface
Authors: Bjor O. H. , Peppin R. I.
Published: October 2005

Sound intensity measurements require detection of both sound-pressure and sound particle velocity. The sound pressure is easily measured with a condenser microphone. The sound particle velocity can be detected indirectly by the conventional pressure gradient method using two closely spaced microphones, the spacing of which is a function of frequency. Alternatively, particle velocity can be detected directly by a new microphone that uses the interaction of the audible sound field and an ultrasonic wave. This new principle allows the construction of a sound intensity probe with a very broad frequency range (20 Hz-5 kHz) without readjustments to the probe. The particle velocity detection principle may also be used for noncontact measurement of surface velocity. As a result, surfaces of any materials may be explored with the probe without any direct contact, eliminating the limitations (such as surface loading, poor mounting methods, and sensitivity problems) posed by conventional accelerometry techniques.
Numerical study of an area array for nearfield sound-pressure measurement
Authors: Yen N. , Corsaro Robert D.
Published: October 2005

In a previous work [M. P. Hegelberg and R. D. Corsaro, J. Acoust. Soc. Am. 77, 1222–1228 [1985)], we described our experimental experience using a planar polymer hydrophone for area-averaged acoustic pressure measurements in the nearfield of an acoustic source. This present paper addresses theoretically the accuracy of such a measurement. A numerical analysis based on the Rayleigh integral formulation is performed on the nearfield radiation from a circular projector (disk) with ka from 10–40. The spatial average of the acoustic pressure received by an area array in the front of this projector is computed in terms of the covered area parallel to the projector's surface. Its magnitude is shown to vary only slightly with changes in the array's location, even within the projector's nearfield region. The reflected wave from a plate of finite thickness is also investigated within this nearfield region by means of the image method. These simulated results are compared with experimental echo reduction measurements obtained under plane-wave conditions.
The effects of phonation on 133Xenon-inhalation air curves (of the kind used in deriving regional cerebral blood flow
Authors: Formby C. , Thomas R. G. , Brown W. S. , Halsey J. H.
Published: October 2005

Regional cerebral blood flow (rCBF) may be measured by noninvasive inhalation techniques that use end-tidal values of respired air radioactivity to estimate the isotope concentration in arterial blood. These end-tidal data are used as an input function in a mathematical equation for measurement of rCBP. For a subject with normal pulmonary function, end-tidal air is assumed to be in equilibrium with the arterial blood at the alveolar surface of the lung during passive breathing. However, an assumption of equilibrium may not be valid for active breathing conditions such as those during phonation. In light of the important role of the respired air curve in the measurement of rCBF by inhalation methods and the possible confounding effects of phonation, respired air curves have been analyzed and will be presented for three groups of male college students: (1) vocalists trained by the same voice instructor (n = 12); (2) members of the same University choir (n = 13); and (3) nonmusicians (n = 12), for three conditions of phonation (of the national anthem). These conditions are (1) speaking, (2) singing, and (3) humming. The curves have also been analyzed for passive breathing. [Portions of this work were supported by an NIH Grant to UAB.]
Vision in lip positioning skills of children with normal and impaired hearing
Authors: Fletcher S. O.
Published: October 2005

Interplay between visual feedback and lip and jaw positioning skill was studied in twenty 5- to 14-year-aid children with normal hearing, and with severe-to-profound hearing impairment. With visual feedback, the subjects in both groups were similar in response time and in accuracy of matching six visually specified lip separation “targets.” Special skill in processing visual information by the hearing-impaired subjects was suggested by higher velocities in lip movements toward the targets and shorter latencies in reaching the goal positions. In the responses of the hearing children, lip-closing movements were executed more accurately than opening movements, both with and without visual feedback. This was found only in the nonfeedback condition with the HI children, suggesting that the visual information had a greater effect on their responses. In general, the findings showed that, given visually displayed lip position targets and feedback from positioning actions, children can achieve them with high accuracy, regardless of hearing status or amount of prior speaking experience.
Comparison of ultrasonic measurements of acoustic scattering from hard infinitely thick striated surfaces with Twersky theory
Authors: McClanahan T. , Diachok O. , Wales S.
Published: October 2005

Ultrasonic laboratory scale measurements of scattering from an infinitely thick, striated surface were conducted to test the accuracy of the Twersky theory predictions. These measurements represent the first phase of a measurement program that is intended to provide a baseline and stimulus for refined theories of underice reflectivity and scattering, and will, in its next phase, consider randomly distributed and oriented half-cylinders on plates. Results of the initial phase reveal that measured reflection coefficients are in excellent agreement with theory at grazing angles between 10° and 50°, when ka < 1 and when ka> 1, where k is the wavenumber and a is the average half-cylinder depth. At intermediate frequencies, measured losses were substantially greater than predictions due to resonance scattering associated with the physical/geometrical properties of the half-cylinders. These results imply that both theoretical and laboratory scale modeling of scattering from sea ice at intermediate frequencies must consider both geometrical and physical properties of the proturbances. [Work supported by ONR.]
Temporary functional changes in men due to exposure combinations of noise and low-frequency vertical vibrations
Authors: Manninen Olavi J.
Published: October 2005

The main purpose of this study was to produce additional information on the connections between the temporary hearing thresholds, body upright posture sway, and cardiovascular changes induced by complex exposure conditions. Seven healthy male students were exposed consecutively five times to mere noise, to mere whole body vibration, and simultaneously to noise and vibration at 20 °C. The noise categories were: (1) no noise and (2) noise of 90 dBA. The categories of low-frequency whole body vibration (Z axis) were: (1) no vibration, (2) vibration within the range 4.4–5.6 Hz, (3) vibration within the range 2.8–5.6 Hz, (4) vibration within the range 2.8–11.2 Hz, (5) vibration within the range 1.4–11.2 Hz, and (6) sinusoidal vibration with a frequency of 5 Hz. The (rms) acceleration in all the vibration models was 2.12 m/s2. The TTS2 values at 4 and 6 kHz increased as a result of simultaneous exposure to noise and vibration significantly more than as a result of exposure to noise alone. The means of the sway variances in the X and Y directions at 0.1 Hz and within the range 0.06–2.00 Hz increased only when the vibration in the noise-vibration combination was a sinusoidal one. The changes in the heart rate, R-wave amplitude, blood pressure, and the haemodynamic index scores also depended on the bandwidth of the vibration, the number of consecutive exposures, and on whether the subjects were simultaneously exposed to noise in addition to vibration. [Work supported by The Academy of Finland.]
Nonlinear acoustics at low temperature
Authors: Putterman S.
Published: October 2005

The anamolous dispersion, strong nonlinearity, and small transport coefficients of He4 make it an ideal medium for establishing the frontiers of nonlinear acoustics. These properties make it possible for He4 to exhibit a well-defined three-wave interaction, where the high-frequency wave is analogous to the pump in a parametric amplifier (the low-frequency waves are the signal and idler). In fact, a macroscopic coherent sound wave will decay dramatically fast due to the parametric amplification of its first phonon of spontaneous decay [J. S. Foster and S. Putterman, Phys. Rev. Lett. 54, 1810 (1985)]. It should bc possible to observe similar effects with capillary waves (ripplons). The properties of He4 as well as the roton minimum in its dispersion law also make it an ideal medium for searching for two- and three-dimensional localized states which are generalizations of the nonlinear Schrödinger equation and Kadomtsev-Petviashvili solitons. Finally, He4 should be used to probe the spectrum of acoustic turbulence. The self-similarity of the stationary turbulent state is a symmetry which will be broken quantum effects at high frequency.
Effects of changes in absolute signal level on psychophysical tuning curves in quiet and noise in patas monkeys
Authors: Smith D. W. , Moody D. B. , Stebbins W. C.
Published: October 2005

Forward masking PTCs were measured in patas monkeys (Erythrocebus patas) at 500 Hz and 2, 4, and 8 kHz and signal levels of 10, 30, and 60 dB SL in quiet, and at 10 dB above masked threshold in two levels of wideband noise. Noise levels were sufficient to increase masked test-tone thresholds to levels that approximated the absolute signal levels tested at 30 and 60 dB SL in quiet. The background masker was used to control for “off-frequency” listening, which can act to broaden PTCs at higher signal levels, by maintaining a constant signal-to-noise ratio with increases in SPL. Results in quiet are in agreement with those reported in the human literature demonstrating broadening of the PTC as signal level is increased. The PTCs measured in noise also demonstrate a similar broadening, or loss of selectivity, at higher SPLs. These findings are not in agreement with a previous study [Green et al., J. Acoust. Soc. Am. 69, 1758–1762 (1981)] that attempted to control off-frequency listening with background maskers at different signal intensities in humans. Differences in findings might be explained as differences in acoustic or experimental parameters between studies. [Research supported by NIH Grant No. NS 05785.]
Interaural discrimination of phase and level differences of spectral sections of low-frequency noise
Authors: Yost William A.
Published: October 2005

A 2000-Hz, low-passed noise was generated with a band of frequencies either interaurally phase shifted or presented with an interaural level difference. When an interaural level difference was generated, the level of all components at one ear was the same and a band of the noise was reduced in level at the other ear. The level of all the components was the same when an interaural phase shift was introduced for a band of the noise. When a band of frequencies are interaurally phase shifted, a pitch (sometimes referred to as the Huggins pitch) is produced. The just discriminable differences of interaural phase or level were measured as a function of the band width of the interaurally changed frequencies and the spectral location of the band. Listeners were more sensitive to interaural phase differences than to interaural level differences. These discriminations appear to be made on the basis of the pitch produced by the stimuli. The listeners report that when these pitches occur, the pitch is lateralized toward one side of the head while the noise timbre is lateralized on the opposite side. The results will be discussed in relation to the concept of a central spectrum and the mechanisms responsible for pitches similar to the Huggins pitch. [Research supported by grants from the NIH (NINCDS) and the AFOSR).]
Effects of removing the “spectral dominance region” upon noise repetition pitch
Authors: Bashford James A. , Warren Richard M.
Published: October 2005

The results of the present study indicate that the spectral dominance region is neither essential for accurate matching of co-phasic repetition pitch (RP +) nor the sole determinant of matches for antiphasic repetition pitch (RP −). Listeners matched sinusoids to RP + and RP − at delays (t) corresponding to repetition frequencies (1/t) from 110 to 196 Hz. Stimuli were presented as broadband, low-pass filtered from the seventh spectral peak, high-pass filtered from the seventh peak, and notch filtered between the third and seventh peaks. Filtering slopes were 196 dB/oct with rejected components replaced by complementary Gaussian noise. Filtering had little effect upon pitch matching to 1/t Hz for RP +. Depending upon filtering conditions, matches for RP − deviated from 1/t Hz by about 5% to 10%. It is suggested that RP is based upon both the spacing of stimulation maxima (1/t Hz for RP + and RP −) and the loci of stimulation (which correspond to integral multiples of 1/t Hz only for RP +). Pitches heard with RP − correspond to resolution of conflicts between loci and spacing, with different compromise pitches found for different spectral ranges.
Tonal implications of musical chords
Authors: Thompson William F. , Cuddy Lola L.
Published: October 2005

Two experiments examined the tonal implications of three different chord constructions. All chords were derived from the major triad in root position. Triadic chords contained all three notes of the triad; dyadic chords eliminated either the third of the fifth of the triad. In experiment I a triadic chord or dyadic chord was paired with a shepard tone. In experiment II a triadic chord was paired with either another triadic chord or a dyadic chord. In both experiments the second member of the pair was located at one of 12 randomly selected transpositions and listeners rated how well the second member of each pair followed the first. Results of the rating profiles bear on earlier work suggesting that different chord constructions emphasize different aspects of musical key relationships, information that may influence perceived tonal movement.
Duration effects on labeling of tonal analogs to F1-cutback continua
Authors: Pastore R. E. , Morris C. , Layer J. K.
Published: October 2005

F1 cutback has been demonstrated to be at least a contributing cue, and very possibly a major cue, for the perception of voicing contrasts. In an attempt to evaluate the feasibility of there existing an acoustic basis for the role of F1-cutback cues in the perception of voicing stimuli, our recent research has focused on comparing stimulus cue dependencies for voicing boundaries with similar stimulus changes in analogous tonal stimuli varying in complexity. An earlier paper [Pastore et al., J. Acoust. Soc. Am. 75, S65 (1984)], described parallel labeling boundaries as a function of tonal analogs to F1 frequency and F2 transitions, but no stimulus duration. We now have identified conditions under which our F1-cutback analog stimuli exhibit both labeling boundary locations, and changes as a function of duration, which are characteristic of voicing boundaries for speech stimuli. [Supported in part by NSF.]
Time-intensity envelope cues for consonant recognition
Authors: Soli Sigfrid D. , Kirby Virginia M. , Van Tasell Dianne , Widin Gregory P.
Published: October 2005

A primary source of perceptual information for the cochlear implant user in the time-intensity envelope of the speech waveform. The purpose of this study was to estimate the amount and type of information for consonant recognition potentially available in the time-intensity envelope of speech. The experimental stimuli were generated from the time-intensity envelopes of 19 /aCa/ utterances (C = /p, t, k, b, d, g, f, θ, s, ∫, v, ð, z, ȝ, m, n, r, l, j/), spoken by a male talker. The envelopes were obtained by full-wave rectifying and low-pass filtering the speech waveforms at 2000, 200, and 20 Hz. These envelopes were used to multiply noise with a 3-kHz bandwidth, producing three sets of envelope stimuli with identical, flat spectra that differed in the amount of time-varying in their amplitude envelopes. The unprocessed speech waveforms and the three sets of envelope stimuli were presented to 12 normal-hearing subjects in blocked, closed-set consonant recognition tests. Individual and group confusion matrices from each test were submitted to multidimensional scaling analyses (SINDSCAL) and information transmission analyses (SINFA). The results of these analyses revealed that three different envelope features account for most of the consonant information in the time-intensity envelope of speech.
A characterization of room noise levels at telephone locations and the effect upon employees' work and communication
Authors: Auten George R. , Royster Larry H. , Pearson Richard G.
Published: October 2005

Noise surveys were conducted at telephone locations in four types of work environments: State government office buildings, fast-food restaurants, automobile dealers/maintenance shops, and shopping mall retail stores. Two types of surveys were taken. A type I survey was conducted during normal working conditions and a type II survey was conducted at selected sites in order to better define the dominant noise sources. Acoustic measurements made included A-weighted, C-weighted, F-weighted (flat), and octave-band sound pressure levels. General room descriptors were also noted for each survey location. A total of 270 telephone locations were surveyed at 51 sites. The employees were asked to assess their work place with respect to noise and its effect on their work, face-to-face, and telephone communication activities. Summary statistics for each type of sound survey and the responses from the questionnaires given out during the surveys will be presented.
Towards developing a parametric model of dynamics of LPC parameters
Authors: Atal Bishnu S.
Published: October 2005

Acoustic parameters, such as LPC parameters, vary continuously as functions of time. The underlying speech (phonetic) events, however, are discrete. How do we go from continuous acoustic representation to discrete phonetic representation? We will discuss in this paper a parametric model for representing variations of LPC parameters with time. We define a matrix Y to express the LPC parameter values at successive time instants with different columns representing time. We then write matrix Y as a product of three matrices A, Z, and P: a central speech information matrix P representing underlying speech events, a left matrix A relating the speech events to the LPC parameters, and a right matrix P representing the spreading of speech events along the time axis. The number of columns in the matrix Z is equal to the number of speech events in a given speech segment and is much smaller than the number of time frames in that segment. We assume that there is overlap between the spreading functions of only neighboring speech events, that is, the matrix PPt is a tridiagonal matrix. We will discuss procedures to determine the matrices A, Z, and P such that the mean-squared error between the elements of the matrix Y and the product AZP is minimized. We will also discuss conditions under which the selection of the matrices is unique.
Model experiments on normal mode propagation in a wedge
Authors: Hobaek H. , Tindle C. T. , Muir T. G.
Published: October 2005

Experiments to measure normal mode propagation into and out of a shallow-water wedge have been conducted in an indoor tank. The wedge has a plane sand bottom and a slope which can be set up to 9°. A seven-element line source allows individual normal modes of low order to be excited. For downslope propagation, measured attenuation and group velocities are in agreement with simple adiabatic normal mode theory. Dispersion and attenuation are rapidly reduced with increasing slope. For downslope propagation, the usual vertical wavefronts associated with normal modes become curved into spheres centered on the source. Up-slope propagation is dominated by the disappearance of modes as they reach their cutoff depth. The energy of a mode traveling upslope is rapidly lost to the bottom after cutoff with negligible coupling to lower modes. [Work supported by ONR.]
Determination of sediment shear properties by numerical modeling of ocean-bottom interface wave
Authors: Schmidt Henrik , Jensen Finn B.
Published: October 2005

The importance of sediment shear properties for low-frequency, shallow-water propagation is well established. Whereas the compressional properties can be measured directly on collected samples, the shear speeds and attenuations have to be determined indirectly from in situ experiments. This is due to the fact that these properties are highly affected by the deterioration of the chemical and mechanical bindings due to depressurization and change of temperature in the core sampling process. The propagation characteristics of ocean-bottom interface waves (Scholte waves) are almost entirely controlled by the shear properties, and these waves, therefore, form a convenient basis for the inversion process. Here, it is demonstrated how the dispersion characteristics, determined from experimental results by a multiple filtering technique, can be numerically modeled by a full wave field solution code [H. Schmidt and F. B. Jensen, J. Acoust. Soc. Am. 77, 813–825 (1985)], yielding the possibility of determining both shear speed and shear attenuation profiles in the upper sediment layers.
The effects of measurement errors in determining the Green's function for shallow water propagation
Authors: Lynch James F. , Frisk George V. , Doutt James A. , Dunn Christopher E.
Published: October 2005

It has been shown by Frisk and Lynch [J. Acoust. Soc. Am. 76, 205–216 (1984)] that, for a horizontally stratified ocean and bottom, one can perform a simple synthetic aperture array cw experiment which yields high-quality information about the modal structure of a shallow water waveguide. Specifically, one measures the magnitude and phase versus range of the pressure field due to a point cw source and then numerically Hankel transforms these data to obtain a depth-dependent Green's function versus horizontal wavenumber. In shallow water, the Green's function contains prominent peaks at horizontal wavenumbers corresponding to the eigenvalues of any trapped and virtual modes excited in the waveguide. In practice, measurement errors can somewhat degrade the quality of the Green's function obtained, as will be shown using both real and synthetic data. Particular errors and experimental effects to be discussed are: ranging errors, nonconstant bathymetry effects, rough surface scattering effects, aliasing and interpolation errors, and the effects of finite aperture. Comparison with conventional array based techniques will also be included. [Work supported by ONR.]
Measurement of complex shear modulus of marine carbonate sand and coral rock by very small amplitude torsional resonant column apparatus
Authors: Figueroa J. Ludwig , Yamamoto Tokuo
Published: October 2005

The complex shear modulus of marine carbonate sand and coral rock has been mechanically measured for shear strain amplitudes as low as 10−8. A high precision torsional resonant column apparatus, equipped with the latest electronic instrumentation, was used to determine both the shear modulus and attenuation at various shear strain amplitudes and several stress conditions of prepared marine carbonate sand and coral rock specimens. The influence of test parameters such as confining effective stress and stress anisotropy was studied to simulate actual field states of stress. Vibrational wave amplitude was also varied in order to determine its effect on the dynamic properties of these commonly occurring marine sediments and to compare them with values found in the literature. The frequency range covered was from 50–500 Hz. The geoaeoustic data obtained at small shear strain amplitude are of special significance in acoustic wave propagation in the ocean with strong bottom interaction. [Work supported by ONR, Code 425UA.]
Acoustic remote profiling of water interfaces
Authors: Maxwell J. W. , Henderson T. L.
Published: October 2005

Acoustic remote profiling of horizontal surfaces using a monopulse technique has been demonstrated in both a lake and shallow-water ocean environment. Data were taken at a center frequency of 30 kHz using pulses with up to a 5-kHz bandwidth. Excessive variations in the computed profile curves for the lake bottom appeared to be due to penetration of sound into the sediment. Variations in the profile curves decreased when examining an extended planar target deployed on the lake surface. The larger impedance mismatch between the water and air certainly prevented sound penetration beyond the interface. The ocean data profile curves exhibited a bias due to noise effects from surface reverberation. Multiping averaging reduced profile variability.
Effects of nonrigid mounting surfaces on array behavior
Authors: Porter David T.
Published: October 2005

Three problems are considered. (1) The general problem, whereby the transducer array excites the mounting structure, which reradiates, and the resulting acoustic field is diffracted by the transducers. (2) The simplified problem whereby the transducers are much smaller than a wavelength, and scattering off of the transducers can be neglected. (3) The simplified problem whereby the transducers are acoustically connected by mutual coupling through their radiating faces, and mechanically coupled through their tail ports and the mounting surface, but acoustic waves do not strike the mounting surface. For a certain class of mounting surfaces, the third problem can be carried out. Calculations were performed when the mounting structure was an infinite elastic fiat plate, or a simply supported beam. A hypothetical line array of eight elements was considered, driven at 9 kHz; the thickness of the mounting surface was varied, to alter the stiffness of the surface. Large variations in array behavior were seen for thicknesses between 0.5 and 5.0 in.
Finite element study of the farfield limit of symmetrical length expander transducer
Authors: Tocquet B. , Boucher D. , Tierce P. , Decarpigny J. N.
Published: October 2005

The finite element code ATILA which has been described previously [J. Acoust. Soc. Am. Suppl. 1 74, S99 (1983)] and is devoted to the modeling of radiating sonar transducers takes account of the acoustic radiation with the help of a finite element discretization of the fluid domain which surrounds the structure. The fluid domain is limited to a spherical exterior boundary upon which a suitable nonreflexive condition is applied. Due to its simplicity, the nonreflexive condition of a spherical wave is generally used and thus the exterior boundary has to be in the farfield region. This communication describes the numerical determination of the farfield limit in the case of a thick transducer which is composed of a long ceramic stack between two identical head masses and has a classical length expander fundamental mode. Due to the thickness of the source, the classical Rayleigh criterion is incorrect and the farfield limit depends upon the type of housing which is used. The various results are described and discussed, from the physical point of view as well as from its numerical consequence.
Timpani normal modes for arbitrary shaped kettles
Authors: Davis Robert E. , Tubis Arnold
Published: October 2005

Calculations of timpani normal modes based on boundary integral equation methods [R. S. Christian, R. E. Davis, and A. Tubis, J. Acoust. Soc. Am. Suppl. 1 73, S85 (1983)] are carried out for a variety of cylindrically symmetric kettle shapes. The kettle is assumed to be rigid, and room acoustics effects are ignored. The kettle shapes considered include hemispherical, hemispherical cap on a cylindrical sleeve, and parabolic. We extend previous stuidies [R. S. Christian et al., J. Acoust. Soc. Am. 76, 1336–1345 (1984)] of (1) the approximate equivalence of air loading effects for equal membrane radii and kettles of equal volumes; and (2) the minimal kettle volume for producing the musically desirable ratios, f11:f21:f31:f41≈2:3:4:5.
The influence of room transients and traversal on loudness discriminability in room
Authors: Lindevald Ian M. , Benade A. H.
Published: October 2005

Six variants of the generic loudness discrimination experiment were conducted to study the influences of room transients and subject mobility in discrimination in rooms. Subjects judged the louder of a pair of tones as the source level difference Δ was varied. The fraction of wrong judgments was plotted against Δ, and the rms spread σ, and the total percent wrong judgments W were found. The six variants were as follows: (1) stimuli presented via two loudspeakers to subjects moving in a room, σ = 1.87 dB, W = 10%; (2) stimuli produced in room and recorded via moving dummy head, presented via headphones, σ = 1.98 Db, W = 11%; (3) gated signals channeled from oscillator to earphones, σ = 0.50 dB, W = 6%; (4) steady tones played in room, recorded via moving dummy head, then gated, σ = 1.52 dB, W = 8%; (5) gated signals played in room recorded via stationary dummy head, σ = 2.32 dB, W = 12%; and (6) samples of steady tones recorded with a stationary dummy head at different points in the room and then gated, σ = 2.72 dB, W = 33%. The auditory system can discriminate source strength in rooms via data from the on/off transients and also from relatively long term sampling from different locations. Removal of such clues reduces discriminability to levels controlled by ordinary room statistics. [Work supported by NSF.]
Acoustic scattering in an ocean environment
Authors: Hackman Roger H. , Sammelmann Gary S.
Published: October 2005

The transition matrix approach has been extensively applied to the free-field acoustic scattering from elastic solids and shells in the past decade. However, it is not known to what extent the salient features of the free-field scattering problem are altered when the scattering problem is reformulated in a realistic shallow water or ocean environment. The present work is centered on extending the transition matrix approach to the case of acoustic scattering by an elastic obstacle immersed in a stratified ocean environment. The ocean is assumed to be vertically bounded and propagation aspects are treated with a normal mode model. Numerical studies are presented for the acoustic scattering from a solid elastic target in the two simplest oceanic waveguide models of interest. The first is a single homogeneous layer bounded by a pressure-release air-water interface and a rigid bottom. The second is a double-layered waveguide to model a single-channel sound-speed profile with a depth excess. [Work supported by the Office of Naval Research.]
Reflection and transmission characteristics of a periodic array of cylinders embedded in a plane slab or in a homogeneous material space
Authors: Lakhtakia Akhlesh , Varadan Vasundara V. , Varadan Vijay K.
Published: October 2005

A periodic array of identical cylinders, identically oriented, and embedded either inside a plane, infinite slab suspended between two homogeneous half-spaces, or by themselves embedded in a material space, forms an interesting class of gratings whose periodicity is vertically pronounced. A theory based on Fourier-Bessel expansions and the T-matrix method is presented to compute the reflection and transmission characteristics of such a grating. The theory is sufficiently general so as to be applicable to electromagnetic incidence of either polarization or to elastic incidence having the SH polarization. The cylinders may be isotropic or may possess transverse iostropy only. Numerical results presented will show that such a grating reflects and transmits specularly almost perfectly, which is in contrast with more conventional gratings made up of periodic, bimaterial interfaces and whose periodicities are horizontally pronounced.
Speech synthesis of Japanese from written Esperanto
Authors: Sato Shigeru , Kasuya Hideki
Published: October 2005

With a subsystem designed to extract meaning from written Esperanto being added to the speech synthesis system of Japanese generated in the semantic/syntactic base [S. Sato and H. Kasuya, J. Acoust. Soc. Am. Suppl. 1 73, S5 (1983)], we present an overview of this translation-synthesis system including a knowledge base editor for implementing linguistic information needed. Allowing a wide range of data modification and file manipulation operations, the frame editor can edit on a frame/slot basis the rules and dictionaries used in parsing Esperanto and generating Japanese. The main portion of the knowledge base is occupied with descriptions about case structures, selectional restrictions, hierarchial relations among items, etc. for detecting anomaly and ambiguity of a given Esperanto sentence. The semantics gives to the meaning a case frame expression, from which the sentence generator produces a surface form with some trimming with phonological and accentuation rules. The synthesis program further converts the surface into acoustic parameters, rendering a time series of control parameters for the terminal analog synthesizer.
BBN Butterfly applications to signal processing
Authors: Sullivan Francis J. M. , Briscoe H. , Estrada R. , Schmidt E.
Published: October 2005

Modern digital signal processing systems require substantial hardware and software flexibility at a sufficiently low cost. The cost of configuring the hardware and developing the software should be low, and it should be easy to make revisions as requirements such as the number of channels and data rates change. Also important is efficiency for both numerically intensive operations, such as FFT and filter operations, and logical and symbolic manipulation intensive operations such as decision making and display generation. This mixture of computationally intensive operations is ideally suited to concurrent parallel processing. The BBN Butterfly multiprocessor provides a general purpose parallel processor which may be configured for a wide range of applications. It contains up to 256 simultaneously operating asychronous processor nodes, each containing a general purpose microprocessor, local memory, and optional floating-point accelerator, optional high-speed auxiliary processors, and a unique expandable inter-processor communication system. The tight processor coupling and global memory sharing provided by the communication system allows the necessary coordination of the operations in the independent processor nodes, and provides a software environment which dramatically facilitates the ease of programming.
Tomographic images of submerged spheres
Authors: Gaumond Charles F. , Abraham Phillip B.
Published: October 2005

Tomographic imaging algorithms have been derived for cases of weak scattering [C. F. Schueler, H. Lee, and G. Wade, IEEE Trans. Sonics Ultrason. SU-31, 195 (1984)]. In order to study strong scattering effects on tomographic reconstructions, ideal images of rigid and elastic targets in a fluid medium will be related to known series solutions of the appropriate wave equations. Results of numerical simulations and physical experiments with a variety of spheres will also be presented.