bluuebunny/crossref_metadata_2025 huggingface dataset:
On identifying syllable boundaries
Authors: Bell-Berti F. , Raphael L. J.
Published: October 2005

The interposition of a constant between vowels has been shown to affect systematically the formant frequencies of those vowels. The nature of these effects appears to depend on the extent to which the vowels and consonants share the tongue and lips as articulators. Traditional articulatory descriptions suggest two alternatives concerning the status of [h] and of [?] as consonants. On the one hand, since they are classified as consonants, we would expect them to produce the same coarticulatory effects as other fricatives and stops. On the other hand, since they are described as nonlingual/labial in their articulation, we would expect them to produce minimal coarticulatory effects. Indeed, results of some recent studies of speech production suggest that neither [h] nor [?] interrupts V-to-V articulations in the way that other consonants do (Harris and Bell-Berti, 1982). The present study employed spectrographic analysis of VV, VhV, V?V, and VCV sequences. Results revealed that there was minimal coarticulation between [h] or [?] and the surrounding vowels. Indeed, the formant structure of the vowels in VhV and V?V sequences were more similar to those of VV sequences than to those of other VCV sequences. Since consonants are often portrayed as the units that delimit syllables, these results raise the question of functional homogeneity within the class of consonants. [Research supported by NINCDS.]
Impact wave transmission through the lower skeletal extremity
Authors: Chu M. L. , Gradisar L. A.
Published: October 2005

Previous studies have revealed that strong relationships do exist between articular cartilage deterioration and prolonged exposure of the joint to impulsive mechanical stress. However, the phenomena of impact wave transmission through the human skeletal system is, at present, not fully understood. This study is an attempt to determine the impact wave propagating properties of the lower skeletal extremity, i.e., the tibia, knee joint, and femur. An abbreviated (cut at the lower tibia and upper femur ends) cadaveric lower extremity is suspended vertically by long steel wires. The upper femur end is subjected to a 150-lb load (to simulate body weight) and the lower tibia end rests on a 100-lb shaker. The skeletal system is subjected to a 3-g impulsive load at a frequency range of 1–3 Hz to simulate walking and jogging. Preliminary results revealed that impact wave propagation speed varies significantly at different portions of the skeletal system, and that the subchondral region of the knee joint attenuates the impact stress drastically by approximately 50%. The effect of total knee prosthesis, shoe inserts, in the propagation of impact wave is also being investigated.
Tone and noiseband masking: Level and bandwidth dependence
Authors: Greenwood D. D.
Published: October 2005

Earlier findings indicated a decrease of about 4 dB in the ratio of signal level to masker level at a masker level of about 50 dB SL when noisebands were subcritical but not when supercritical [Greenwood, J. Acoust. Soc. Am. 33, 484–502 (1961)]. Schlauch, Weir, and Norton [J. Acoust. Soc. Am. Suppl. 1 71, 573 (1982)] reported a related result. The early data suggested a masking study in which both masker and signal were the minimum width subcritical stimulus, namely pure tones of the same frequency in-phase, to see if consistent change would occur. Pilot tone-on-tone experiments in 1960 [Greenwood, Harvard P. A. L. Status Rpt. 37, 8–9 (1961)] showed a larger drop in ratio since signal and masker were coherent. Further detailed tone-on-tone growth of masking curves from over a dozen subjects were obtained in 1967–69 and, with the 1960 results, are reported here. A clear break in slope, of variable abruptness, usually occurs at about 50 dB SL, either rapidly or gradually dropping 5/M ratio by 6 to 8 dB. [c.f. Rabinowitz et al., J. Acoust. Soc. Am. 59, 1506–1509 (1976) for a similar result.] Addition of low-level wideband and high-pass noise was found to counteract the change, i.e., to raise the high level section of the growth of masking curve [see also Zwicker, Acustica 6, 365–396 (19561; Viemeister, J. Acoust. Soc. Am. 51, 1265–1269 (1972); Moore and Raab, J. Acoust. Soc. Am. 55, 1049–1054 (1974) for consistent results.] However, use of added narrow bandpass noise at variable frequencies indicates the most effective region in which to add the noise lies, at a frequency ratio of band to masking tone of 1.3 to 1.5, between masking tone and its second harmonic. These results and others [Green, J. Acoust. Soc. Am. 41, 1517–1525 (1967)] appear consistent with the results of increasing bandwidth from subcritical to supercritical widths cited above.
Detection of amplitude modulation by normal-hearing and hearing-impaired subjects
Authors: Bacon Sid P. , Viemeister Neal F.
Published: October 2005

Modulation thresholds for sinusoidally amplitude-modulated (SAM) broadband noise were obtained as a function of modulation frequency from normal-hearing subjects and from subjects with primarily high-frequency hearing losses. The resulting Temporal Modulation Transfer Functions (TMTFs) indicated that the impaired subjects were generally less sensitive to modulation. In addition, unlike previously published data for normal-hearing subjects, a level effect was observed in the impaired subjects: sensitivity decreased, particularly at high modulation frequencies, as noise level decreased. TMTFs were also obtained from normal-hearing subjects for SAM noise that was lowpass filtered at 1.6 kHz after modulation, and presented with a continuous, 1.6-kHz highpass masker. These TMTFs were similar to the broadband TMTFs in the impaired subjects; this suggests that the impaired temporal processing in the hearing-impaired subjects is a result of a narrower effective bandwidth. [Supported by NIH NS 12125.]
Sound in a periodically stratified alternating fluid-solid medium
Authors: Schoenberg Michael , Plona T. J.
Published: October 2005

The exact solution for plane-wave propagation in a periodically stratified medium composed of ideal fluid, elastic solid layers is derived for all values of frequency and wavenumber parallel to the stratification. As in other periodic medium proparation problems, the field variation normal to the layering is characterized by the eigenvalues of the transfer matrix that relates values of stress and velocity across one period. In the low frequency limit, expressions for the slowness surfaces are found explicitly. At any angle of propagation except normal to the layering there are two possible propagating waves, one fast and one slow. Motion parallel to the layering in adjacent solid and fluid layers for the fast wave is in phase while for the slow wave it is 180° out of phase. As the wavenumber parallel to the stratification becomes large, additional propagatory modes appear.
Numerical solution of coupled mode equations for rough surface scattering
Authors: Dozier Lewis B.
Published: October 2005

Theories of underwater acoustic signal propagation based on normal modes become quite complicated when the modes are coupled via inhomogeneities in the medium or its boundaries. The usual derivation of coupled mode equations from the Helmholtz equation, e.g., along the lines of Pierce [J. Acoust. Soc. Am. 37, 21 (1965)] leads to a coupled second-order system of differential equations which is not amenable to numerical solution as a two-point boundary value problem. However, C. A. Boyles [J. Acoust. Soc. Am. 73, 800 (1983)] has recently shown that, in the case of rough surface scattering, this system can be transformed into a coupled first-order system for both forward and backward wave amplitudes. In this paper we show that this system can be further transformed into a system which can be efficiently integrated numerically using the state-of-the-art software packages EISPACK and LINPACK for matrix exponentiation and inversion. Thus we are able to obtain the numerical solution of the full elliptic reduced wave equation for any realization of a frozen, one-dimensionally [z = h(r)] rough surface. Extension to include Doppler effects due to a time-varying surface is straightforward.
Signal coherence in shallow water with rough boundaries
Authors: Ozard John M. , Zelt Barry C.
Published: October 2005

A normal mode model to predict signal coherence for a source moving in shallow water with rough boundaries has been described previously [J. M. Ozard, G. H. Brooke, M. J. Wilmut, and M. V. Greening, J. Acoust. Soc. Am. Suppl. I 69, S19 (1981)]. The model assumes that mode amplitude or mode phase fluctuate. We have extended this model to widely spaced sensors by permitting the fluctuations to be independent from sensor to sensor. This new model has been used to calculate signal coherence for a variety of sensor configurations. Coherences have been calculated for low frequencies for which only a few modes are present. When source receiver range is changing rapidly it is found that for closely spaced sensors coherence depends only on receiver separation, mode shape, and mode excitation. However, for widely spaced sensors or sources that maintain a constant source receiver range the roughness parameters have a profound effect on coherence. Sensor configurations that give consistently high signal coherence, and those suitable for measuring signal coherence as a means to evaluating model parameters, are discussed.
Bottom backscatter in shallow water
Authors: Goldsberry T. G. , Pitt S. P. , Rolleigh L. D. , Garcia A. L.
Published: October 2005

At the 104th Meeting of The Acoustical Society of America, we described recent experiments conducted at the shallow water site near San Diego, California, that extend the range of bottom backscattering measurements to smaller grazing angles and narrower beamwidths than previously reported [J. Acoust. Soc. Am. Suppl. I 72, S74 (1982)]. Preliminary results of analysis of 30-kHz data were reported and an anomaly between backscatter coefficient calculated from a broad beam and a narrow beam sensor was noted. The effect of measurement system beamwidths on backscatter coefficient estimation will be discussed and results of measurements at other frequencies will be presented. [This work was supported by the Naval Ocean Research and Development Activity.]
Study of acoustical scattering from submerged elastic spheroidal shells
Authors: Werby M. F. , Green L. H.
Published: October 2005

We perform theoretical studies of acoustical backscattering from submerged elastic shells of variable thickness and material. We calculate both form functions and monostatic backscattering patterns. The theoretical calculations were performed using the T-matrix formalism developed at NCSC. Calculations will be presented for thicknesses varying from 5% to 20%. Preliminary results illustrate the strong dependence of both form function and scattering on shell thickness which suggests an interference phenomenon. Patterns associated with material differences will also be discussed. It will also be noted that as objects become more elongated the monostatic scattering patterns exhibit more detailed structures.
A study of acoustical scattering from axially symmetric fluid loaded elastic objects with ridges
Authors: Werby Michael F. , Hackman Roger H.
Published: October 2005

We perform theoretical studies of acoustical scattering from submerged axially symmetric elastic objects with ridges. The ridges are uniformly distributed over the objects to maintain axial symmetry and are of Gaussian shape normal to the surface of the object and are allowed to vary with respect to the number, height, and width. A T-matrix approach is employed which easily incorporates the ridges exactly. Calculations are performed for both back scattering form functions along the axis of symmetry and for monostatic distributions. The effects on resonances and monostatic distributions are discussed through comparisons with objects with no ridges.
Perception of French vowel contrasts by native and non-native French speakers
Authors: Sitaras Katherine M. , Gottfried Terry L.
Published: October 2005

Three native speakers of French produced, in carrier sentence context, seven minimal pairs (CV or CVC words) using vowel contrasts /i/-/e/, /e/-/ɛ/, /ɛ/-/a/, /ɑ/-/ɔ/, /ɔ/-/o/, /u/-/y/, and /y/-/ø/. These contrasting word pairs were presented in two perceptual tests: forced-choice identification, and categorial ABX discrimination (in which each word token was spoken by a different speaker). The performance of three American English groups (non-French-speaking, beginning, and intermediate French students) was compared to that of native French speakers on both tests. There were significant differences in identification and discrimination accuracy between native French and American groups. However, American groups were not significantly different from each other in identification and discrimination, despite their differences in exposure to French. Although the lack of differences between American groups might suggest that vowel perception is difficult to alter by second language instruction, more data are needed to determine whether vowel perception accuracy may be improved with further or different kinds of French instruction. Production data from the French learners are currently being analyzed to ascertain whether there is a relation between accurate vowel perception and good pronunciation. [Supported by NIH Grant MH-37924 and SUNY Research Foundation.]
Variability in anticipatory and carryover vowel-to-vowel coarticulation
Authors: Magen Harriet
Published: October 2005

Acoustic measurements of medial schwa in CVCəCV utterances were made in order to determine the coarticulatory effect of preceding and following vowels. Previous work [C. Fowler, J. Speech Hear. Res. 46, 127–139 (1981); Phonetica 38, 35–50 (1981)] indicated greater carryover than anticipatory vowel-to-vowel coarticulation in similar sequences. The principal finding of the preset study is that the relationship between anticipatory and carryover coarticulation varies according to whether the utterance is produced in isolation or in a carrier phrase. While there is generally more measured coarticulation on the schwa of utterances produced in a carrier phrase than in isolation, anticipatory coarticulation is especially variable according to such contexts. [Work supported by NIH grant HD-01994.]
Source localization in a waveguide using a matched-field technique
Authors: Feuillade C. , Kinney Wayne A.
Published: October 2005

The ability to localize a source in a waveguide by correlating measured and predicted acoustic field values at a vertical array of receivers depends at least on (1) the number of dominant acoustic modes that have been adequately sampled and (2) the accuracy of the field predictions. Several attempts to localize sound sources, using experimental and model data for shallow and deep water environments, are discussed. The results of these attempts are presented as well as observations regarding the number of depth/range replica source points required to localize the source for complicated (many modes) versus simple (few modes) acoustic environments. [Work supported by NORDA.]
Treation ranging utilizing a conditional beta input error density
Authors: Perruzzi J. J. , Hilliard E. J. , Pereira D.
Published: October 2005

Triangulation ranging is a method of estimating range to an acoustic source by utilizing the measured difference in arrival time (time delays) of spherical wave fronts at two receiving sensors. Errors in the measured time dray values yield inaccurate range estimates. If these errors are unrealistically large, negative range values will result, and in practice are eliminated. A symmetrical beta density function is employed to model time-delay measurement errors. In order to insure that all range estimates are physically realistic, the end points of this beta density are dipped, which leads to a conditional distribution. The resulting distribution is subsequently used to obtain the triangulation range density along with its mean and standard deviation.
Modeling of a piano hammer
Authors: Suzuki Hideo
Published: October 2005

From the measurement of the force-time pattern and the acceleration-time pattern, a simple model that describes the action of the hammer, when it hits an ideally rigid string, was established. It was found that the relation between the force (f) and the deformation (x) is approximated by the form f = kX4 for the specific hammer used for the measurement, where k is a constant. This shows that the hammer stiffness S(x) has a nonlinearity of the third order. Then, the effective mass Mh was calculated using a single mass-spring model. It is fairly constant during the time when the hammer is moving toward the string. The force-time patterns of this model were calculated using S(x) and Mh for different hammer velocities. The agreement between the measured and calculated force-time patterns is good (within 15% near their peaks). As a second model, a double mass-spring system was considered. The force-time patterns calculated from this model are in better agreement with the measured curves.
The digital bow
Authors: Weinreich Gabriel , Caussé René
Published: October 2005

The “digital bow” is a device that senses the instantaneous velocity of a chosen point on a string and, by looking up an equivalent frictional characteristic stored in a computer table, exerts an electrodynamic force on the string corresponding to what a physical bow would do under the same circumstances. The process is repeated at a high sampling rate in real time. Under such conditions, we observe the string breaking into spontaneous Helmholtz motion. The arrangement is of great interest to the physicist because it provides exact control of the frictional characteristic of the “bow,” allowing one to investigate details of the bowing process to a degree hitherto unattainable. It may also have considerable musical potential, since the behavior of this “bow” is not limited by the properties of Siberian horse hair or of the secretions of dripping evergreens. Video and audio tapes will be presented. [Work supported in part by NSF.]
Beam excitation of doubly leaky Rayleigh wave on layered viscoelastic half-space
Authors: Jensen Finn B. , Schmidt Henrik
Published: October 2005

The problem of nonspecular reflection of an ultrasonic beam incident at or near the Rayleigh angle onto a thin surface layer overlying a homogeneous viscoelastic half-space is investigated. An approximate solution to this problem was recently published by Nayfeh and Chimenti [J. Acoust. Soc. Am. 75 1360–1368 (1984)], who presented detailed computational results for a low-velocity surface layer (loaded half-space). We concentrate on the case of a high-velocity surface layer (stiffened half-space), where propagation is characterized by a leaky Rayleigh wave, which, however, will become doubly leaky (energy leaking into the water as well as into the lower half-space) when its phase velocity exceeds the shear velocity of the half-space. For an incident Gaussian beam, we present exact solutions for the reflected field using a recently developed numerical model [H. Schmidt and F. B. Jensen, J. Acoust. Soc. Am. 77, 813–825 (1985)] providing full wave field solutions for incident beams of arbitrary width, reflected off a multilayered viscoelastic structure. It is shown that the surface-layer thickness can be determined from the reflectivity pattern for layer thicknesses up to 1.5 times the shear wavelength in the surface layer.
Transmission and reflection of acoustic waves through a combination of elastic and liquid layers
Authors: George Jacob
Published: October 2005

We extend the formalism of Folds and Loggins [J. Acoust. Soc. Am. 62, 1102 (1977)] to calculate acoustic transmission and reflection coefficients for a plane wave at oblique incidence on a combination of elastic and liquid layers of plane parallel plates. We discuss the modified boundary conditions and show how the acoustic field is calculated at any point inside an elastic or liquid layer. We present numerical results for the case of steel and water layers.
Labial articulation patterns associated with segmental featares and syllable structure in English
Authors: Macchi Marian J.
Published: October 2005

Linguistic contrasts in syllable structure were compared with contrasts in segmental structure by studying lower lip movement data obtained with the University of Tokyo x-ray microbeam system [Kiritani et al., J. Acoust. Soc. Am. 57, 1516–1520 {1975)]. Intervocalic |p| and |s| in three syllabic structures (V$CV, VC$V, VC$CV) with different vowel environments (combinations of |i|, |a|, |u|) were analyzed for two speakers. More complex structures (V$|pl|V, V|p|$l|V, V|pl|$V, V$|sp|V, V|s|$|p|V, V$|spl|V , V|s|$|pl|V) were also analyzed for one of the speakers. Lower lip height was separated into jaw and lip-proper components [Edwards et al., J. Acoust. Soc. Am. Suppl. 1 74, Sl17 (1983)]. Several relationships between jaw height and lip-proper height were observed. Segmental contrasts (e.g., |p| vs |s|; |p| in |ipi| vs |apa|) were realized by height differences in both the jaw and the lip proper, whereas syllable structure contrasts {e.g., syllable-initial |p| vs syllable-final |p|) were realized primarily by jaw height differences. Thus the phonological distinction between segmental and suprasegmental contrasts was maintained at the level of articulatory representation.
Coal cutting noise control
Authors: Pettitt Mark R. , Aljoe William
Published: October 2005

The noise level near coal cutting operations in underground coal mines presently presents a significant health hazard to the miners. Hearing loss claims are a growing source of litigation in the industry. Through a series of research programs, the U.S. Bureau of Mines has developed methods to significantly reduce the noise generated during coal cutting. The noise control methods take full advantage of the dynamic characteristics of the forces generated during coal cutting. The spectrum of the cutting force was shown to be proportional to about one over the square of the frequency. Resonant response could, therefore, be significantly reduced by increasing the stiffness of the mining machine structures. Novel and effective techniques of achieving increased stiffness and damping without interfering with the machine's mining functions were developed and then demonstrated on selected types of coal mining machines. Finally, the feasibility of achieving cutting force isolation was established through laboratory cutting tool tests. In-mine viable isolated cutting tool designs were then developed and demonstrated through in-mine tests. As a result of this research work, the machine design concepts and techniques required to significantly reduce coal cutting noise and vibration, are now available to the coal mining industry.
Octave- and fractional-octave-band digital filtering based on the proposed ANSI standard
Authors: Davis Steven B.
Published: October 2005

A software implementation has been developed which is based on the proposed ANSI standard “Specification for Octave-Band and Fractional-Octave-Band Analog and Digital Filters.” This standard is a revision of S1.11-1966(1976) “Octave, Haft-Octave, and Third-Octave Band Filter Sets.” Significant changes to the standard are the inclusion of digital filters, definition of octaves based on powers of 2 in addition to powers of 100.3, and relaxation of filter symmetry requirements. The implementation is divided into three parts: (1) fractional-octave-band filter design, (2) an efficient decimation-in-time algorithm to perform the filtering operation on sampled signals, and (3) application of A-, B-, C-, and D-weighting curves. Numerical calculations and graphical displays of the output of the filters for white noise input verify the efficacy of the implementation. An evaluation of the digital filter design compared to the proposed standard, elucidates the difficulties in maintaining similar specifications in the analog and digital domains.
An exact formulation for the internal pressure of a cavitation bubble
Authors: Commander Kerry W. , Crum Lawrence A. , Prosperetti Andrea
Published: October 2005

Recent experiments have shown that when the acoustic driving frequency is near one of the bubble's harmonic resonances, the theoretical values predicted by the Rayleigh-Plesset equation are inconsistent with observed values. This inconsistency lead Prosperetti to consider the internal pressure term in the Rayleigh-Plesset equation in a more general manner. In the past, the internal pressure of a bubble was assumed to be accurately predicted by a polytropic approximation. The internal pressure is computed from the conservation equations, resulting in a more accurate formulation. The new method also provides additional information about the internal thermodynamics of a bubble, which is explored in some detail. The two models are examined using some of the recent techniques in dynamical systems. “Feigenbaum trees” are shown for the two models of interest. This method for analyzing an equation is shown to be very sensitive to the internal pressure term, and thus it is an appropriate method for comparing different acoustic cavitation theories. [Work supported in part by NSF and ONR.]
Simple models for underwater shock based on modal analysis and DAA
Authors: Ginsberg Jerry H.
Published: October 2005

A general algorithm for evaluating the response of submerged structures to incident shock waves is developed based on a modal expansion version of the doubly asymptotic approximation (DAA) for fluid-structure interaction. A general procedure is outlined, in which the addition of substructures is treated in modular form. The structural motion is described in terms of the modes of in-vacuo free vibration of each substructure. Simple criteria for the companion fluid modes, which represent the effects of scattering and radiation, are developed. The nature of the modal coupling in this scheme, in combination with the fact that modal expansion techniques generally involve a comparitively small number of degrees of freedom, makes the approach very attractive for systems analysis. The procedure is illustrated by the case of a slender circular cylinder with spherical caps that is subjected to an exponential shock wave that arrives at an arbitrary angle of incidence. Such incidence, which was not considered in previous studies, is shown to lead to rigid body translation and rotation, as well as asymmetrical axial and bending deformations. [Work performed under the auspices of the U.S. Dept. of Energy by Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.]
Root-power sums and spectral slope distortion measures for all-pole models of speech
Authors: Hanson Brian A. , Hermansky Hynek , Wakita Hisashi
Published: October 2005

Distortion measures for use in speech processing are presented with emphasis on improvement of efficiency and recognition performance for noisy speech. Good results have been obtained from measures calculated from differences of root-power sums (i.e., differences of index-weighted cepstral coefficients: k *ck). This type of distortion measure can be derived as an approximation to the spectral slope distortion measure, which expresses slope differences between test and reference logarithmic spectra. However, when used on all-pole model spectra, the root-power sum distortion is computationally more efficient. It is well-suited for use with both linear predictive (LP) analysis and the recently proposed perceptually based LP [H. Hermansky, B. A. Hanson, and H. Wakita, IEEE Proc. ICASSP 85, 509–512 (1985)]. The proposed distortion measures are shown to provide equal or better recognition scores compared to standard LP-cepstral matching in low noise conditions and substantial improvements in noisy conditions.
Experiments on reduction of aircraft interior noise using active control of fuselage vibration
Authors: Fuller Chris R.
Published: October 2005

Interior sound in aircraft fuselages is directly coupled to fuselage vibration. This suggests the use of active vibration control of the fuselage vibration to reduce interior noise levels. In this paper, preliminary experiments to investigate this new technique are discussed. The experiments were performed on a closed cylindrical shell excited by an external acoustic source, representative of an aircraft fuselage. Active vibration control of the shell was achieved by a single minishaker attached pointwise to the exterior wall of the cylinder. Sound levels throughout the cylinder were measured by a moveable microphone traverse. The interior levels were found to be attenuated at most locations between 10 and 35 dB by the active vibration control with a constant control amplitude and phase, i.e., global attenuation was achieved. The physical mechanisms behind the effect are discussed. The new method shows much potential for reduction of propeller interior noise in aircraft, without the penalty of large added weight.
Diagnostic imaging of the nonlinear acoustic parameter B/A
Authors: Lewin Peter A.
Published: October 2005

One of the most promising applications of ultrasound in medicine, currently in the experimental trial stage, is imaging based on the nonlinear propagation parameter B/A. Evidence is currently emerging that B/A is related to the structural characteristics of tissue and information on B/A variations in tissue may provide a new avenue in diagnostic ultrasound tissue characterization. This presentation will briefly outline the theoretical background and operation principles of real-time nonlinear parameter imaging systems, including both pulsed and cw devices. Subsequently, the differences between conventional, real-time B-scan imaging and the B/A imaging will be presented. Different nonlinear imaging algorithms, including those for the more desirable pulse-echo mode of operation, will be discussed and the fundamental limitations of this novel imaging facility will be reviewed. Possible modifications in the currently used B/A imaging procedures to improve B/A picture quality will also be discussed, and the potential applications of B/A imaging in ultrasound tissue characterization will be pointed out.
Detection of simple and complex tones in fixed and random conditions
Authors: Buus Søren , Schorer Edwin , Florentine Mary , Zwicker Eberhard
Published: October 2005

Psychometric functions for detection of pure (220, 1100, or 3850 Hz) and complex tones in the presence of a 64 dB SPL uniformly masking noise were measured in a 21, 2AFC paradigm. The complex tone consisted of 18 equally intense components spaced about one critical band apart between 110 and 7260 Hz. In experiment 1, all levels for a single signal were presented in mixed order within a block of trials. Results for eight normal listeners show parallel psychometric functions for simple and complex tones. Thresholds are 43–44 dB SPL for the pure tones and about 37 dB SPL per tone for the complex tone. In experiment 2, all levels and signals were presented in random order within each block of trials. Results for four normal listeners show psychometric functions parallel to those in experiment 1. Thresholds are about 46 dB for the pure tones and 40.5 dB for the complex tone. These results are consistent with a multiband energy-detector model in which the decision is based on an unweighted sum of decision variables across an optimum selection of channels. [Supported by Deutsche Forschungsgemeinschaft and NIH-NINCDS R0 1NS 18280.]
Development of a finite difference model for arbitrary axisymmetric acoustic pulses applicable in investigating finite ground impedance effects
Authors: Sparrow Victor W. , Raspet Richard
Published: October 2005

With the advent of supercomputers, accurate modeling of sound propagation over a finite impedance ground via finite difference (FD) techniques is becoming possible. In this preliminary investigation, FD solutions to the fundamental hyperbolic partial differential equations governing acoustics which agree with analytic solutions are sought. The particular numerical techniques are similar to those of computational compressible fluid flow, modified for spherical waves in a cylindrical coordinate system to correctly model boundary conditions. Results for acoustic simple sources will be provided.
Interactions in the labial musculature during speech
Authors: Folkins John W. , Linville Raymond N. , Garrett J. David , Brown Carl Kice
Published: October 2005

Interactions in electromyographic activity of the upper and lower lips during speech were studied by manipulating the magnitude of bursts of activity related to bilabial closure. Four pairs of electrodes were placed in the labial musculature in each of four normal-speaking young adults. Activity from both the upper and the lower lip was manipulated with the jaw free and then the procedures were repeated with the jaw fixed with a bite block. Manipulation of muscle activity usually resulted in positively correlated changes in activity recorded from the other three electrode pairs. Contrary to expectations, no significant negative correlations were found. The positive correlations may be due to (a) sensitivity of the electrode placements to the same motor units, (b) sensitivity of the electrode placements to motor units participating in common recruitment orders, or (c) functional interactions among muscles or muscle compartments that constrain them to maintain task-specific proportional relations. [Work supported by NINCDS.]
Simulations of matched-field processing in a deep-water Pacific environment
Authors: Porter Michael B. , Dicus Ronald L. , Fizell Richard
Published: October 2005

Matched-field processing is a signal processing technique for arrays in which field vectors for assumed source positions (range and depth) are substituted for plane-wave steering vectors in conventional linear and nonlinear beamformers. The field vectors are computed by standard acoustic field models (FFP, normal mode, etc.) which take into account propagation effects in an oceanic waveguide. The output is an ambiguity surface over possible source positions in which a peak is expected at the true source position. Accuracy of the computed fields is limited in large part by our knowledge of the environment. This environmental mismatch causes degradation in localization performance, sometimes leading to large errors in estimation of source position. In order to assess the significance of this effect, simulations were performed in which a measured field is synthesized using a slightly different environmental model from that used for the steering vectors. The differences were introduced to simulate expected errors in sound-speed profile, sediment thickness, and elastic wave speed. Calculations were made for a cw source operating at 10 Hz and depths of 25 and 250 m in a 500 m-deep ocean. The receiver was a 16-element vertical array at ranges of 25 (shadow zone) and 100 km (second convergence zone). A typical Pacific sound velocity profile was assumed. The bottom was modeled by a thin (50-m) sediment layer overlying an elastic subbottom. Degradation in localization performance due to environmental mismatch will be discussed both quantitatively and qualitatively.
Doubly asymptotic approximations in acoustics, elastodynamic, and electromagnetic scattering
Authors: Geers Thomas L.
Published: October 2005

Doubly asymptotic approximations (DDAs) are differential equations that describe the dynamic interaction between a scatterer and a surrounding wave-propagating medium. They find application in problems of acoustic, elastodynamic, and electromagnetic scattering by bodies of complex geometry and structure through the utilization of boundary element and finite element techniques. DAAs have been successfully developed and applied for acoustic scattering, have been developed for elastodynamic scattering, and are under development for electromagnetic scattering. In this paper, systematic formulations of DAAs for the various field equations are presented, and their behavior in canonical problems is examined. The utilization of increasingly higher-order DAAs is explored and the point of diminishing returns is sought.
A talker recognition based on vector quantization codebooks
Authors: Rosenberg Aaron E. , Soong Frank K.
Published: October 2005

Highly efficient and effective short-term spectral representations of talkers can be obtained using vector quantization (VQ) codebook construction techniques. A talker recognition system has been implemented in which each talker is represented by a VQ codebook constructed from a large set of short-term spectral vectors obtained from a series of training utterances provided by the talker. In operation, the utterances of an unknown talker are analyzed and “encoded” using the codebook of a specified talker. The accumulated distortion between the input utterances and the specified talker's codebook is used to carry out a talker recognition decision. This technique can be said to be text independent to the extent that the training utterances adequately represent each talker's speech sound repertoire. The system can be extended to text-dependent operation with an additional training procedure in which specified utterances provided by a given talker are represented as encoded vector sequences using the talker's codebook. In use, an unknown talker is prompted to provide specified utterances which are analyzed and compared with the encoded prototypes for a specified talker. The system has been evaluated using a 100-talker database of 20 000 digits spoken in isolation. In a talker verification mode, average equal-error rate performance of 2.2% for text-independent operation and 0.3% for text-dependent operation is obtained for seven-digit-long test utterances.
A fully quantized stochastic coder for low-bit-rate speech coding
Authors: Kroon Peter
Published: October 2005

Stochastic coding has the potential of providing high-quality speech at low bit rates [Schroeder and Atal, ICASSP (1985), pp. 937–940]. In this scheme linear predictive techniques are used to model both the long-term and short-term correlations in the speech signal. The remaining residual signal (excitation) is modeled by a codebook populated with samples from a Gaussian source. The whole procedure is based on an analysis-by-synthesis approach that minimizes the error between the original and the reconstructed signal. In the coder described by Schroeder and Atal, the excitation was coded at 2 kbps and the remaining parameters were left unquantized. To assess the usefulness of the stochastic coding approach for low-bit-rate speech coding, the performance of the coder with all the parameters quantized was investigated. A scalar quantizer was used to encode the short-term predictor coefficients at 1.8 kbps. Different vector quantization procedures for the long-term predictor coefficients resulting in bit rates varying from 1 to 2 kbps were investigated. It was found that a total of 8 kbps were required to produce results undistinguishable from the unquantized version. Speech coded at different rates between 4.8 and 8 kbps will be played at the conference. [Work supported by NSA.]
On comparing tree and codebook coding of LPC residuals at very low bit rates
Authors: Lin Daniel
Published: October 2005

It has been suggested that codebook coding of LPC residuals offers significant performance advantage over tree coding at very low rates [cf. M. R. Schroeder and B. S. Atal, Proc. ICASSP 85]. An innovation codebook provides a better coveting of the LPC innovation space (in the sense of having a smaller covering radius) than an innovation tree of the corresponding rate. These comparisons usually assume that the branches of the innovation tree are populated with independent identically distributed random variates (i.e., a stochastic tree). In this paper, the methods of selecting the innovation elements on a binary innovation tree such that the branches contain “complementary” sequences are examined. The covering properties of these “complementary” tree codes are compared with the covering properties of stochastic trees and stochastic codebooks. The results on the “complementary” tree codes indicate that (1) the performance of an innovation code did not correlate with its covering radius and (2) tree coding of LPC residuals at very low bit rate (rate 1/4 code) did not result in any performance degradation.
The multilayer expansion as a benchmark for range-independent propagation loss models
Authors: Weinberg Henry
Published: October 2005

In today's world of normal mode, FFP, and parabolic equation codes, one seldom thinks of ray tracing as a benchmark for propagation loss models. However, the former are often inappropriate in bottom-bounce regions, and do not readily provide physically significant quantities such as arrival angle and travel time. The multilayer expansion of the reduced wave equation is a theoretically exact ray model for range-independent environments. The numerical implementation approximates the ocean sound-speed profile by layers in which inverse sound speed squared is linear and the density is constant. The depth-dependent Green's function is then expanded into a finite geometriclike series plus a remainder. In many applications the remainder is small and may be neglected. For benchmark purposes, one must integrate the remainder over wavenumbers of interest in order to obtain the total field. [Work supported by the Naval Research Laboratory.]
Measurement of panel reflection using acoustical scale modeling techniques—Part II: Measured results
Authors: Ortega Jose C. , Veneklasen Paul S.
Published: October 2005

The importance of early reflected sound from side wall and ceiling reflecting panels in auditoria and other spaces used for musical presentation has been recognized for some 25 years. Quantitative data on the size, shape, and orientation of reflecting panels to achieve wideband spectral reflections have not been widely available. This paper presents some results on the effect of size and aspect ratio on the reflection characteristics of hard panels measured using scale modeling techniques.
The noncorrelated sound-pressure level: A quantifiable metric for spatial characteristics in performance spaces
Authors: Blair Christopher N.
Published: October 2005

Recent research at MIT's Experimental Music Studio in binaural signal processing has led to a simple technique for separating the correlated portion of an audio signal received by a listener (the quasimonophonic portion related to the direct sound path, nondiffuse first-order ceiling reflections, etc.) from that portion of the signal in which the amplitude and/or phase relationships differ at each ear (due to lateral reflections of different path length, randomly arriving diffuse reflections, etc.). The noncorrelated sound-pressure level is easily measured by comparison of the relative voltage outputs of the microphones in the binaural head using a sound level meter. Real heads exhibit unsystematic amplitude and phase anomalies which render perfect cancellation of monophonic signals impossible. However, for the unequalized head used in this study, the noncorrelated sound-pressure level of monophonically presented pink noise is more than 10 dB below the sound-pressure level measured in octave bands by each ear separately. Future work and applications are discussed. [Work supported by MIT Provost Fund.]
Hybrid ray-PE analysis of guided high-frequency propagation
Authors: Ishihara T. , Felsen L. B.
Published: October 2005

Surface guiding of high-frequency sound fields may take place near a concave boundary in a homogeneous medium or near a plane boundary in a refracting medium. Multiple reflected ray fields excited by a source near the boundary form caustics that pile up at long ranges around the source depth. Conventional caustic corrections are inadequate to deal with this catastrophe. It is shown here that the narrow angular spectrum interval occupied by the troublesome caustic-forming rays can be filled alternatively by a narrow-angle parabolically approximated (PE) wavefield. The hybrid combination of legitimate rays and narrow-angle PE can be regarded either as correcting via PE the failure of ray acoustics at long ranges near the source depth, or as removing the narrow-angle restriction from PE by filling the wide-angle spectra with rays. The theory is illustrated with calculations for a range-independent ducting environment, and also for a range-dependent ducting-to-antiducting transition. [Work supported by ONR.]
Comparison of a fan-shaped and a rectangular hall
Authors: Bradley J. S.
Published: October 2005

Newer auditorium acoustics measures were used to evaluate and compare a fan-shaped and a rectangular auditorium. Measurements included reverberation times, early decay times, clarity C80, overall strength, and lateral fractions each measured in octave bands from 125 to 8000 Hz. Measurements were made at combinations of 3–5 source positions and 12 receiver positions. The results indicate that the shape of the hall influences the within-hall variation of these acoustical quantities. The fan-shaped hall is thought to have a less diffuse early sound field that causes larger seat-to-seat variations in acoustical quality and a systematic variation in acoustical characteristics from the front to the rear of the hall.
Theoretical functions of transient diffusibility in reverberant rooms
Authors: Rao Yu-an , Carterette Edward C.
Published: October 2005

Much effort has been spent in investigating the relationship between the physical properties of reverberant sound fields and the parameters of sound qualities. A single form of parameter, which is a function of both space and time, that might help in establishing a relationship between its real-time value and subjective criteria is sought. Based on a simplified model of spatially directional diffusibility, a general solution to the differential equation of transient diffusibility d(t) and the definiteness ratio D(t) is given. Computed and measured curves are consistent with each other; in particular, an explanation of the nonmonotonic V shape of d(t) curves by means of theoretical calculations and mathematical derivations is provided. It is suggested that d(t) and D(t) could serve as quantitative, predictive parameters in applications to architectural acoustics and the control of sound quality in acoustic engineering.
Measurements of vowels in isolation and in sonorant context
Authors: Fourakis Marios , Miller James D.
Published: October 2005

In Miller's auditory-perceptual theory vowels are hypothesized to occupy nonoverlapping zones in a three-dimensional space defined by the relative positions of the first three spectral prominences of the short-term spectrum and by a reference related to the speaker's characteristics. In order to validate target zones drawn on the basis of the data available in the literature, we have recorded two male and two female speakers of American English producing the nine pure vowels of English in isolation and in sonorant context. The recordings were digitized at 20 000 Hz with 14-bit precision and analyzed using ILS. The formant and fundamental frequency information was extracted from the ILS analysis files. The data are now in the process of being smoothed in the log-frequency domain and are being transformed into paths in the three-dimensional auditory perceptual space. By examining not only the pure vowels but also vowels in sohorant context, the aim is to establish the coarticulatory effects on relative spectral prominence positions of preceding and following [1] and [w]. [Work supported by NINCDS and AFOSR.]