bluuebunny/crossref_metadata_2025 huggingface dataset:
Coupled mode analysis of multiple-rough-surface scattering
Authors: Beills Alan , Tappert Fred D.
Published: October 2005

The range-dependent boundary condition imposed by a rough surface serves to couple the normal modes of an underwater acoustic field. Using a statistical analysis based on a model decomposition of the solution of the parabolic wave equation, we have derived a system of equations for the mean power in each mode describing the transfer of energy between modes. Explicit formulas for the coupling coefficients (transition probabilities) have been obtained in terms of the spectrum of the rough surface [W. J. Pierson, Jr. and L. Moskowitz, J. Geophys. Res. 69, No. 24, 5181–5190 (1964)]. Numerical solutions of the coupled power equations have been obtained for low-frequency long-range propagation and used to calculate the effects of rough-surface scattering on the transmission loss as a function of range and depth. [Work supported by ONR.]
Stochastic inputs for acoustic models
Authors: Barnes A. E. , Solomon L. P.
Published: October 2005

Transmission loss depends on the sound velocity structure. Present models are deterministic, and require deterministic inputs. However, from a given set of sound velocity data generally only one sound velocity profile is generated. The resulting transmission-loss curves are frequently compared to acoustic data for model evaluation purposes, sometimes unsuccessfully. A technique has been developed which, from a given data set, will generate many profiles, obeying certain vigorous mathematical constraints. Unfortunately each profile requires the acoustic model to be rerun, but the process generates transmission-loss fields which can be statistically analyzed. The generation of such fields will allow more realistic appraisals of acoustic models when compared to acoustic data. The sensitivity of acoustic models to small perturbations in the sound velocity field is presented for certain special cases. The technique is applicable to all environmental inputs for any models requiring deterministic inputs.
Numerical calculation of the intensity distribution in sound channels using coherence theory
Authors: Whitman Alan M. , Beran Mark J.
Published: October 2005

We have demonstrated that coherence theory can be applied to the practical computation problem of the propagation of a beam in an infinite half-space with stratified but arbitrarily varying speed of sound variations. The intensity distributions found in this manner are the same as those of an equivalent point source in regions removed from the caustics of the geometrical ray family, but the intensity formula is continuous everywhere in the field and may be used in the vicinity of caustics. The computer time and storage requirements are equivalent to those of a ray program. [Work supported by NSE.]
Existence region of dichotic noise pitch
Authors: Wightman Frederic L. , Grantham D. Wesley , Fowler Cynthia
Published: October 2005

In several forced-choice experiments, listeners were required to discriminate a 400-msec burst of diotic noise from a 400-msec burst of dichotic noise. Both noises were computer synthesized, and were produced by adding (digitally) equal-amplitude, random-phase sinusoids, spaced 10 Hz apart from 100 to 3000 Hz. The dichotic noise was identical to the diotic noise except that one component (the “signal”) was interaurally phase reversed. In some conditions several, harmonically related, components were phase reversed. As is well known, such dichotic noise stimuli produce a pitch that corresponds to the frequency which is phase reversed, and this pitch was presumably the basis of discrimination in our experiments. The aim of the experiments was to determine the frequency limits (existence region) for the dichotic noise pitch. For “signals” between about 200 and 100 Hz, discrimination performance was near perfect, and beyond these limits dropped abruptly to chance. Moreover, it appeared that adding harmonics to the “signal” affected perception of the fundamental pitch only to the extent that the harmonics themselves were within the critical frequency region. These results suggest that the dichotic noise pitch is mediated by the same sort of process that underlies the masking-level-difference (MLD) phenomenon.
Coarticulation effects in Russian VCV utterances
Authors: Purcell Edward T.
Published: October 2005

Öhman [J. Acoust. Soc. Am. 39, 151–168 (1966)], based on the speech of one informant reading a limited corpus, found that coarticulation effects between successive vowels did not occur across consonants in Russian VCV utterances. The present paper reports on an expanded study of Russian formant frequency using the speech of four informants who read nonsense words containing all possible combinations of Russian vowels and voiced stops. The data were analyzed on USC's version of SCRL's Interactive Laboratory System. Evidence regarding the presence or absence of coarticulation effects will be presented in the light of Öhman's findings.
Modified LPC algorithm for the analysis of noisy speech
Authors: Sambur M. R.
Published: October 2005

By altering the basic all-pole structure of a speech signal, an additive noise signal diminishes the effectiveness of the linear prediction (LPC) approach to the analysis of speech. In this paper, a simple modification of the standard LPC method is suggested for combating the deleterious effect of the additive noise. The new method involves the use of the residual signal energy to form an estimate of the noise statistics and to then modify the computed correlation coefficients accordingly. Since the residual signal contains that part of the signal that is not predictable, it can be related to the additive noise. The new method has been tested on synthetic speech utterances and has resulted in significantly more accurate estimates of formants frequencies and bandwidths.
Time course of suppression
Authors: Weber Daniel L.
Published: October 2005

The threshold for a 10-msec, 2-kHz sinusoid was examined in backward and forward masking. The delay between the signal and the 500-msec “critical-band” masker (N0 = 40 dB) was fixed at 0 msec. If a “suppression” band of noise occurs simultaneously with the masker, thresholds are considerably reduced (20 dB in backward masking, 8 dB in forward masking), or “suppressed.” Varying the temporal position of the “suppression” band with respect to the “critical-hand” noise and observing changes in threshold allows one to estimate the time course of suppression. In both backward and forward masking, no suppression can be seen for temporal differences greater than 40 msec, whereas the results of other experiments [ L. L. Elliot, J. Acoust. Soc. Am. 42, 143–153 (1967)] suggest that excitation can be seen for 100–200 msec. The relatively greater suppression observed for backward masking is expected if “suppression” is a more rapid process than “excitation.” [Work supported by NIH.]
Phoneme confusion analyses for evaluating an ear-insert microphone
Authors: Webster J. C. , Schiller E.
Published: October 2005

Analyses were made of the errors made by a panel listening in noise to recordings of 250 PB words picked up by the ear-insert microphone of Ono and Saito [J. Acoust. Soc. Am. 60, S106(A) (1976)]. Since the responses were of the open-set write-down type, errors consisted of no-responses and errors on initial and/or final consonants and/or on the medial vowel of the CVC monosyllabic words. In general errors were made on 160 of the 250 words consisting of 423 phonemic errors of which 68% were from the test vocabulary, 12% were not, and 20% were no-responses. Fifty percent of the phonemic errors were on the initial consonant, 34% on the final, and 16% on the vowel. Unvoiced stop and fricative errors occurred most often and most confusions were between and among them, 66% for initial and 78% for final consonants. The most error-prone vowel was [a]. The similarity between these and conventional-microphone errors says the ear-insert microphone is an acceptable alternative. [Supported by DOD and HEW.]
Bistatic surface scatter experiments at the Azores Fixed Acoustic Range
Authors: Freese H. A. , Buehler B. G.
Published: October 2005

As part of the Azores Fixed Acoustic Range measurement program, a series of experiments was undertaken to study the effects of the ocean surface on the propagation of acoustic signals in the specular direction. In particular, the following signal characteristics were investigated as a function of center frequency in the band 500–5000 Hz: signal time speed, frequency spread, amplitude statistics, phase statistics, and scattering loss. The experiments were carried out over a 1.5-NM path and a 18-NM path. The results appear to be simply related to the Rayleigh parameter of the ocean surface. In conjunction with the acoustic experiments, measurements were made of the ocean surface characteristics. These measured characteristics were then used in the Kirchhoff approximation to the Helmholtz integral to predict the observed characteristics of the acoustic signals. The results show that the agreement between the theory and the measurements is quite good. [Work supported by NAVSEA.]
Technique for measuring the plane-wave reflection coefficient of the ocean bottom
Authors: Frisk George V. , Oppenheim Alan V. , Martinez David R.
Published: October 2005

A technique for measuring the plane-wave reflection coefficient of a horizontally stratified ocean bottom is presented. It is based on the fact that for a point source the bottom-reflected field and the plane-wave reflection coefficient are related through a two-dimensional Fourier transform. Knowing the reflected field as a function of position, one can therefore use the fast Fourier transform to obtain the reflection coefficient as a function of wave number. Examples which illustrate the method are discussed. [Work supported in part by ONR Contract N00014-77-C-0196 and ARPA monitored by ONR under Contract N00014-75-C-0951-NR 049-308.]
Air flow of plosive consonants in the speech of the hearing impaired
Authors: Whitehead R. L. , Jones K. O.
Published: October 2005

The peak rate of oral air flow during production of plosive consonants by five normal-hearing, five moderately to severely hearing-impaired, and five profoundly deaf adult males was investigated. Air flow was measured during production of CV and VCV syllables consisting of the vowel /a/ and the consonants /b/, /p/, /d/, and /t/. All hearing-impaired and deaf subjects had congenital hearing losses and were able to intelligibly produce the syllables. The results indicated that for the normal-hearing and hearing-impaired subjects, in both syllable environments, the voiceless plosives were characterized by significantly greater oral air flow than their voiced cognates. Also for the normal-hearing and hearing-impaired subjects, in both syllable environments, there was a trend for the flow rates for /t/ to exceed those for the other voiceless consonant /p/, and the rates for /d/ to exceed those for the other voiced consonant /b/. In general, the results for the deaf subjects were not consistent with those for the normal-hearing and hearing-impaired groups.
Intonation contour and syntactic structure as predictors of apparent segmentation
Authors: Geers A. E.
Published: October 2005

The relative contributions of intonation and syntax to the segmentation or “chunking” of speech stimuli was examined using the “click migration” technique. In the first experiment normal-hearing subjects perceptually located clicks in syntactic and nonsyntactic stimuli in which intonation pattern was varied. The tendency for the perception of interrupting stimuli to cluster was significantly greater at boundaries that were marked by both syntactic and prosodic cues than at those marked by intonation alone. In the second experiment sentences in which intonation pattern was varied were presented on videotape to deaf and normal-hearing lip readers. Subjects were required to locate a visual flash embedded in the spoken sentence without auditory cues to intonation pattern. The normal-hearing subjects failed to show significant perceptual migration of interrupting flashes. Deaf subjects, however, showed significant perceptual migration toward the major syntactic boundary when it coincided with the intonation boundary. Deaf subjects' performance on the lip-reading task strongly resembled that of normal subjects on the auditory task. [Work supported by NIH.]
High-sensitivity acousto-optic system
Authors: Cole James H. , Johnson R. L. , Bhuta P. G.
Published: October 2005

A Raman-Nath imaging system was operated over a frequency range of 50 kHz to 10 MHz with an experimental sensitivity of −137 dB re 1μ Pa (approximately 10−16 W/cm2) at 500 kHz. An optical heterodyne technique was employed to obtain these sensitivities. Theoretical calculations project that additional laser power can provide sensitivities of approximately −184 dB re 1μ Pa (3 × 10−21 W/cm2) at 500 kHz. Improved resolution measurements as well as the results of the utilization of acousto-optics to analyze specular acoustic reflections from thin metal plates in water is presented. For several materials tested there is strong agreement between theory and experiment in the 1–3 MHz frequency range. [Work supported by DARPA.]
Earthquake simulation and test procedure for communications equipment
Authors: Liu S. C. , DeCapua N. J.
Published: October 2005

A rational procedure for determining a regional earthquake test environment for communications facilities is described. The approach includes examination of a wide range of telephone building responses to arrive at an upper-bound response spectra. An acceleration time history test environment in the form of a synthesized earthquake is generated to match the spectra. The regional test is then established by linearly scaling the time history to the peak acceleration shown on a national earthquake design regionalization map. Further scaling to account for motion amplification for in-building location of equipment was achieved through examination of data gathered from the 1972 San Fernando earthquake. Communications equipment mounted on steel framework are tested for their earthquake vulnerability according to the specified laboratory test environment.
Seismic and dynamic test capabilities at Combustion Engineering, Inc.
Authors: Haslinger K. H.
Published: October 2005

A description of CE's Seismic Test Facility and a discussion of its use for environmental qualification of mechanical and electrical equipment will be presented. The presentation will focus on the Biaxial Seismic Simulation Fixture on the Digital Vibration Control System with Modal Analysis Capabilities. The various electrodynamic shakers and their use for steam generator tube vibration tests, as well as for on-site testing of large cabinet structures (resonance survey and identification of mode shapes and modal damping parameters) also shall be covered. Photographs will be shown which depict the various shaker installations with typical test setups. CE's approach to seismically qualifying some complex structures through combined analysis and test techniques will be demonstrated through work performed on Nuclear fuel assemblies and control element drive mechanisms. A brief outline of CE's analytical capabilities shall be given.
Evaluation of a new protocol for production of hearing-aid-processed signals
Authors: Studebaker Gerald A. , Cox Robyn M.
Published: October 2005

A new protocol for obtaining and utilizing hearing-aid-processed signals in hearing-aid research or hearing-aid selection is described. Data are presented which illustrate the extent to which this procedure may be expected to result in a signal spectrum at the subject's eardrum which is the same as the spectrum the subject would have received if the hearing aid itself had been placed on his ear (a directly aided situation). An earlier investigation (Cox and Studebaker, 1977) indicated that the traditional protocol for the production and utilization of hearing-aid-processed signals resulted in substantial discrepancies between these two spectra. The data presented were obtained using KEMAR as the subject with a Zwislocki coupler as KEMAR's earcanal/eardrum. The discrepancy between directly aided and hearing-aid-processed spectra was typically ±2 dB for ear-level hearing aids fitted using standard, vented, or open earmolds (in open earmold fittings only the amplified component of the directly aided spectrum is reproduced). [Work supported by NIH.]
Multidimensional analysis of electroacoustic distortions in low-fidelity circuitry
Authors: Bickford Barbara Jill , Yonovitz A. , Lozar J. T. , Mitchell C. W.
Published: October 2005

Investigators have recently considered the correlation between electroacoustic characteristics of voice communication circuits and the intelligibility of speech signals passed through them. The detrimental effects on the perception of speech by electroacoustic distortions has not been unanimously ascribed to any one distortion. This study investigated listener perception of hearing-aid transduced speech and music using a posteriori techniques of multidimensional scaling procedures. Evaluative data consisted of judgments of pairs of speech and music samples creating proximity matrices between 12 hearing aids. This perceptual data was submitted to INDSCAL to determine those electroacoustic characteristics germane to the decision process of judging quality in low-fidelity circuitry. Correlational analysis was used to determine the regression structure of these electroacoustic measures on preference and quality judgments. The data indicated interactions were present between the speech and music judgments and electroacoustic distortions. Frequency response and bandwidth were evidenced as features influencing both speech and music with third-harmonic distortion and internal noise being specific to speech quality assessment and transient distortion and phase distortion affecting listener perception of the music stimuli.
Progress in the development of a tactile aid for the deaf
Authors: Scott B. L. , De Filippo C. L.
Published: October 2005

Eight normal-bearing adults learned to lipread with one of two lipreading aids. Both aids consisted of three spectral channels: a fixed high-frequency and a midfrequency channel for sibilants and bursts and a low-frequency channel for coding the first formant of vowels. Both aids relied on changes in sensation rather than locus of stimulation for transmitting spectral information and the amplitude-time envelope. One aid had electrotactile and vibrotactile transducers and the other had only vibrators for transducers. Performance was measured with our “tracking” procedure (delayed shadowing) using ongoing text. Half the subjects performed the tracking task for the first four hours lipreading alone and the other half with one or the other of the aids. Aided subjects then changed to lipreading alone and unaided subjects to an aided condition. Results indicate that the aids can enhance tracking scores and can facilitate the learning of lipreading skills. [Supported by NS 03856.]
Effects of varying total adaptor energy in selective adaptation
Authors: Simon Helen J.
Published: October 2005

Two experiments were designed to examine the effects of varying total adaptor energy in selective adaptation along a synthetic stop consonant continuum. Experiment I considered the effect of the number of adaptors presented in the adaptation sequence preceding each test sequence, with repetition rate held constant: Over the range from 8 to 32 adaptors, the magnitude of the phonetic boundary shift was found to be a linear function of the logarithm of the number of adaptors. Experiment II explored the effect of variations in the repetition rate (or density) of adaptors with the number held constant. A nonmonotonic relation was found between the phoneme boundary shift and the interadaptor interval: A greater shift was observed for a 750-msec interval than for either a 250-msec interval or a 1750-msec interval. These low-level stimulus energy variables (adaptor number and repetition rate) affect the magnitude of the phonetic boundary shift in what may be a trading relationship. [Work supported by NICHD to the Haskins Laboratories.]
Levels of decision in the perception of voicing contrasts
Authors: Dechovitz D. R. , Mandler R.
Published: October 2005

Various types of acoustic cues have been shown to influence the voiced-voiceless decision for initial prestressed consonants. In the present study, a selective adaptation method was used to investigate possible feature extraction devices underlying the perception of voicing. Two [da-tha] continua were constructed, each ranging in voice onset time (VOT) from 0 to 55 msec in 5-msec steps. The total transition duration of each stimulus was 15 msec in one series and 70 msec in the other. Differential effects were obtained for within- and cross-series adaptation along a VOT dimension by presenting an adapting stimulus from each series with the same absolute VOT(25 msec). The present results support the view that models of voicing perception based strictly on absolute VOT detectors are inadequate. Further, they suggest that a sequence of decisions grounded in cue extraction is the basis for the voicing percept.
Some context effects on voice onset time
Authors: Weismer Gary
Published: October 2005

Systematic variance in measures of voice onset time (VOT) has been attributed primarily to place of articulation and position of stress relative to the target segment. Although data are available regarding other influences (e.g., rate) on VOT, we are unaware of any information regarding effects of phonetic contexts on this measure of glottal-supraglottal timing. As a result of post hoc we observations from a previous study [Klee, Weismer, and Ingrisano, J. Acoust. Soc. Am. 60, S63(A) (1976)] concerning context effects on VOT, an experiment was designed in which fluctuations in VOT of the first consonant in CVC target words could be observed as we systematically varied the tense/lax and voicing features of the interconsonantal vowel and final consonant, respectively. Our results indicate that, for the initial consonant in a CVC target word, (1) longer VOT's are associated with tense, as compared with lax, interconsonantal vowels, (2) longer VOT's are associated with voiced, as compared with voiceless, final consonants, and, (3) the interactive effect of interconsonantal vowel and final consonant features on VOT appears to be extremely complex.
Noise-related turbulence measurements for various surface geometries
Authors: Olsen W. A. , Boldman D.
Published: October 2005

Fundamental theories for noise generated by flow over surfaces exist for only a few simple surface shapes. The role of turbulence in noise generation by complex surfaces should be essentially the same as for simple surfaces. Examination of simple-surface theories indicates that the spatial distributions of the mean velocity and turbulence (intensity, spectra, and integral scale length) are sufficient to define the noise emission. Measurements of these flow properties were made for a number of simple and complex (STOL aircraft blown flaps) surfaces. The configurations were selected because their acoustic characteristics (i.e., shape of radiation pattern and velocity power law) are quite different. The spatial distribution of the flow properties around the complex surfaces and approximate theory are used to qualitatively explain the varied acoustic characteristics. The data properties possess some simplifications, which can be used in the theories. The major simplification is that the turbulence spectra are essentially described by the isotropic turbulence relationship, independent of the surface configuration and of the location in the flow field. This result is used to partially explain why the shape of acoustic spectra vary little and why acoustic model data accurately scale to larger size.
The effects of cholinesterase antagonists on stapedial reflex behavior
Authors: Ruth R. A. , Johns M. E. , Cantrell R. W. , Kramer L. D.
Published: October 2005

We have studied acoustic reflex behavior in patients with myasthenia gravis. The underlying defect in this disorder is felt to be a reduction in the postsynaptic acetylcholine (Ach) receptor sites. The increasing weakness of these patients brought on by exercise is thought to be secondary to increased neuromuscular blockade. This affect can be reversed by anticholinesterase agents thereby increasing Ach/receptor ratios hence improving muscular response. At times these drugs can result in increased neuromuscular block if super saturation of the system is reached, i.e., a cholinergic response. The purpose of the present investigation was to evaluate the therapeutic and toxic effects of various anticholinesterase agents on acoustic reflex behavior in patients with a broad spectrum of neuromuscular blockade. Measurements included acoustic reflex threshold, reflex growth function, and fatigibility of the reflex response to both continuous and interrupted acoustic stimulation. In this large population (39) of myasthenic patients in varying stages of therapeutic control, we have observed the effects of edrophonium HCl on the acoustic reflex. We can divide these patients into two groups: those showing facilatory response (e.g., decreased threshold, increased magnitude and growth function, and decreased fatigue) and those exhibiting disintegration of response patterns (e.g., increased threshold or absent response, decreased magnitude and growth function, and increased fatigue).
Comparison of auditory critical bands measured by loudness summation and acoustic reflexes
Authors: Berry Galen W. , Brandt John F.
Published: October 2005

The critical bandwidth in four normal hearing listeners was examined using two different psychophysical methods. Loudness balances and acoustic reflex measures were made to a two-tone stimulus when the components comprising the complex were adjusted to an “equal intensity” level or an “equal reflex” level. Measurements following these adjustments facilitated the comparison of two-tone loudness summation with two-tone acoustic reflex threshold as a function of sound pressure level. Measurements were made centered around 1000 Hz for various bandwidth spacings of the two-tone complex ranging from 100 to 3000 Hz. The results indicate a difference in critical bandwidths which depends upon the method of adjustment of the two-tone complex (equal reflex vs. equal intensity) for both the loudness balance and the acoustic reflex tasks. By using similar durations, similar sound pressure levels, and similar adjustments of the two-tone complex the comparison of the two-tone acoustic reflex to the loudness of the eliciting signal was facilitated. For this procedure the acoustic reflex appeared to be loudness determined, at least at reflex threshold levels.
Coupled piano strings
Authors: Weinreich Gabriel
Published: October 2005

The fact that a piano typically has not one, but two or three strings tuned to a given pitch, and that these sets of strings cross the bridge at (almost) the same point, leads to significant dynamical coupling among their vibrations. Since the dominant dissipation mechanism is the non-rigidity of the bridge, the rate of energy loss by one string is radically affected by the way that its partners are vibrating; for example, an “antisymmetric” vibration of a pair of strings is much longer-lived than a “symmetric” one. This fundamental phenomenon is complicated by a number of factors, including (a) slight differences in the natural frequencies of the individual strings; (b) a bridge admittance which has a reactive as well as a resistive part; (c) two possible polarizations of the string vibration; and (d) hammer irregularities which cause nonidentical initial excitations of the strings. In this paper we develop theoretical predictions of the way that the rate of energy transmission from strings to bridge, as a function of time, depends on the various parameters mentioned; we then compare these predictions with experimental measurements of beats and “aftersound” under various conditions. Our data shows the time-dependence of each polarization of string vibration amplitude, as well as the resulting sound pressure level, covering a dynamic range of 70 dB from the moment of hammer impact until the signal is lost in the noise. The agreement with theory is excellent. On the basis of this understanding we also explain the function of the una corda pedal in controlling the aftersound, point out the stylistic possibilities of a split damper, and explore the way in which an excellent tuner can use the fine tuning of the unisons to make the aftersound more uniform from note to note.
Theoretical low-frequency transmission loss over an attenuating sediment-rock bottom
Authors: Dicus Ronald L. , Diachok Orest I.
Published: October 2005

Computations of transmission loss were made for a shallow source (10 m) and a receiver at 550-m depth in 3600 m of water using the Kutschale Fast Field Program algorithm. The transmission medium consisted of the water column with typical Atlantic sound speed profile; a 200-m-thick sediment layer (d = 200 M) with average sound speed, density and attenuation profiles according to Hamilton; and an elastic half-space with physical properties of rock, including shear attenuation of 5 dB/wavelength as suggested by historical dale [Attewell et al., Geophysics 31, 1049–1056 (1966)] and recent measurements by the authors. For a rock bottom only, shear wave attenuation increased transmission loss dramatically (40 dB at 10 Hz and 500 km). Together with the sediment layer the loss decreased at frequencies where the wavelength λ < d (20 dB at 10 Hz). At sufficiently small wavelengths the process may be viewed as turning rays that avoid interaction with the high-loss rock interface but suffer attenuation losses along refracting paths within the sediment. Sediment enhanced transmission is thus limited at low frequencies by the layer thickness and high frequencies by the frequency-dependent sediment attenuation.
Low-frequency noise and vertical correlation in the North Atlantic
Authors: Merklinger H. M. , Lanham A.
Published: October 2005

During the summer of 1977, the Defence Research Establishment Atlantic (Canada) and the Admiralty Underwater Weapons Establishment (U.K.) conducted joint acoustic investigations at eleven sites in the North Atlantic. Ambient noise data in the frequency range 5–800 Hz were collected using a 360-ft-long vertical array of twelve hydrophones. Noise levels and the vertical spatial correlation results are shown.
Microcomputer control for psychoacoustic experiments
Authors: Klein M. A. , Gable G. A. , Edmunds D. L. , Eicher D. A. , Hartmann W. M.
Published: October 2005

We describe a psychoacoustics laboratory with microcomputer control of stimulus generation and data acquisition. The control hardware is based on a MOS Technology 6502 microprocessor with 6 K of ROM and 13 K of RAM. Interfacing is through programmable circuitry using MOS Technology 6532 chips. Analog signal generating equipment is controlled by 16 logic lines and eight 12-bit DAC's. Interaction with subjects is through 48 input/output logic lines and a 16-channel 12-bit ADC. Experimental data is stored in a fixed, standard format; it can be displayed on a video screen, printed on paper, and/or stored on standard audio cassettes. Software is based around the KIM operating system using subroutine calls rather than a high-level language. The software control package is specialized for counting, timing, and sequencing stimuli and interacting with subjects. The system presently runs forced choice, method of adjustment, and up-down tracking routines. Logical construction of experimental programs from the modular subroutines can be simpler and faster (though less flexible) than FORTRAN programming of a large system.
Further investigation of the relation between aural overload and TTS in man
Authors: Humes L. E. , Wightman F. L.
Published: October 2005

Two experiments investigated the relation between psychophysical aural overload thresholds and noise-induced temporary threshold shift (TTS). In the first experiment, aural overload thresholds were obtained with the method of best beats prior to noise exposure at 500, 1000, and 2000 Hz in 16 normal hearing young adults. Subjects were then exposed to broad-band noise at 100 dB for 10 min after which TTS2 at 4000 Hz was determined. Results confirmed earlier psychophysical and physiological findings in that a significant (p < 0.001) correlation of −.81 was observed between TTS2 and mean aural overload threshold (MAO). The second experiment was conducted with an additional group of ten normal hearers. Each subject participated in two experimental sessions. In the first session, half the subjects were exposed to broad-band noise at a level determined by their overload thresholds (MAO + 40 dB) while the other subjects were exposed to a fixed level of noise (100 dB SPL). In the second session, the exposure conditions were reversed so that the fixed level group received the noise exposure at a level determined by aural overload threshold and vice versa. Results were as follows: (1) the correlation observed in the first experiment was confirmed with these additional ten subjects: and (2) the values of TTS2 observed under the MAO + 40 dB condition were significantly (p < 0.05) less variable than those observed under the fixed level of exposure. The latter finding implies that weighting noise exposure level according to MAO reduces individual differences in TTS. Implications of these findings for hearing conservation strategies will be discussed.
Absence of tonotopic organization in the motion of the basilar membrane of the alligator lizard
Authors: Peake W. T. , Ling A.
Published: October 2005

In the alligator lizard it appears that auditory nerve fibers from the apical end of the receptor organ have low characteristic frequencies (0.2 < CF < 0.8 kHz) and those from the basal end have high CF's (0.9 < CF < 4.0 kHz). [Weiss, Mulroy, Turner, Pike, Brain Res. 115, 71–90 ( 1976)]. We have used the Mössbauer method to measure velocities of radioactive sources on the basilar membrane. Control experiments indicate that (1) placement of Mössbauer source need not alter the response properties of the ear, and (2) the source sticks to the basilar membrane. For the velocity levels we have used, the motion appears to be independent of the longitudinal position of the Mössbauer source on the basilar membrane. The frequency dependence of basilar membrane velocity is similar to that of the columella (stapes) velocity. These results indicate that the frequency selective properties of the auditory nerve fibers are strongly influenced by mechanisms other than basilar membrane motion. [Work supported by NIH.]
The effects of an oceanic frontal system on acoustic propagation as determined by ray modeling
Authors: Flanagan R. P. , Zabalgogeazcoa X. , Weinberg N. L.
Published: October 2005

An oceanic frontal system similar to that found in the Northwest Pacific is modeled. Ray theory is used to calculate the multipath structure as a function of range and determine the effects of the frontal system on ray type, amplitude, and vertical angle for shallow sources and deep receivers located in both warm and cold waters. A hypothetical receiving horizontal line array of varying beamwidth determines the apparent bearing of the source resulting from the changing multipath structure. This bearing is found to be dependent on array orientation, range into the frontal system, and array beamwidth. Optics is used to briefly examine the horizontal refraction effects of the system.
Ocean Acoustic Tomography: Can It Work?
Authors: Munk W. , Wunsch C.
Published: October 2005

We consider the mapping of meso-scale ocean eddies from fluctuations of acoustic travel times between sources and receivers at separations of the order of 1000 km. The procedure for, “inverting” these measurements to form the best linear estimate of the interior eddy field is discussed. The effectiveness of such a system depends on the distribution of the sources and receivers and the precision of the travel time measurements. We do not know whether the system can be made to work.
An environmental-acoustics model for a deep moving ocean
Authors: Watson J. G. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

A ray-acoustics model is derived from the wave equation for a moving inhomogeneous ocean. Validity of the model depends on assumptions concerning the propagation frequency and the Mach number of the oceanic flows. The frequency regime of hundreds of Hertz is emphasized. Effects of oceanic sound speed and current are incorporated in the model equations in a consistent manner. Consistency leads to expressions for travel time and spreading loss which are simplified, in ways depending on quantities such as propagation range. The oceanic flows may be either deterministic or stochastic. For the latter, examples of acoustic statistics considered include single-path phase variance and multipath expected intensity. The model is applied to medium-range propagation through a stochastic internal-wave field. Consistent approximations to the statistics of internal-wave fluctuations are obtained from the authors' previous paper [J. Acoust. Soc. Am., 61, 716–726 (1977)]. A turning-point approximation is used to analyze relevant statistics for refracted/refracted rays. Results reflect the explicit inclusion of internal-wave currents and modal structure. [Work supported by ONR.]
Ultrasonic Fatigue of Commercial Alloys
Authors: Morris W. L. , Buck O.
Published: October 2005

A machine capable of fatigue testing high-strength alloys at 20 kHz and for temperatures up to 900 °C is described. An electrostatic approach used to measure specimen vibration amplitudes at temperature is also discussed, as well as methods to calculate the applied stress. The machine has been used to study the processes of fatigue crack initiation and propagation at 20 kHz on several aluminum alloys, for comparison of fatigue behavior of the same alloys at 10 Hz. The modes of crack initiation at 20 kHz were the same as at 10 Hz for the materials studied. However, localized heating was observed, which is associated with microcrack propagation at 200 kHz. The crack growth rate, therefore, was regarded and the fatigue lifetimes were substantially increased over those at 10 Hz.
Spectrum analysis of elastic wave scattering from cracks in metals
Authors: Lewis Kent , Szilas Peter , Fitting Dale , Adler Laszlo
Published: October 2005

A broadband incident of longitudinal ultrasonic wave is scattered and mode converted at cracks (of different shapes and sizes) in diffusion bonded titanium. The scattered longitudinal and shear waves are analyzed by an analog spectrum analyzer. The RF signal is also digitized and Fourier analyzed. A geometrical theory of diffraction for elastic waves was developed which is based on (1) Keller's diffraction theory [J. Appl. Phys. 28, 426 (1957)] and (2) Maue' solution to the semi-infinite plane for elastic waves [Z. fur Angew. Math. u. Mech. 33, 1 (1953)]. The experimentally observed spectra are compared to theoretical calculations. [This research was sponsored by the Center for Advanced NDE operated by the Science Center, Rockwell International, for the Advanced Research Projects Agency and the Air Force Materials Laboratory under Contract F33615-74-C-5180.]
Identification of the response properties of efferent axons of the dorsal cochlear nucleus
Authors: Young E. D.
Published: October 2005

The response properties of cells in the dorsal cochlear nucleus (DCN) of unanesthetized, decerebrate cats fall into two broad classes: type II/III units are excited by best frequency tones at all levels above threshold; type IV units are inhibited at most levels [Young and Brownell, J. Neurophysiol. 39, 282 (1976)]. By using antidromic stimulation, the response properties of cells whose axons travel in two output pathways of the DCN have been identified. It was possible to antidromically stimulate occasional type II/III cells from the posterior, dorsal part of the AVCN, but never type IV cells. In contrast, almost all type IV cells can be antidromically stimulated from the dorsal acoustic stria (DAS). Most type II/III cells cannot be stimulated from the DAS. Thus, the ascending axons from DCN to higher brainstem nuclei originate largely in type IV cells and the association fibers from DCN to AVCN originate in type II/III cells. These results will be discussed in terms of the known morphological features of the DCN and the previously described response properties of its cells.
Patterns of auditory-nerve fiber responses to steady-state vowels
Authors: Sachs M. B. , Young E. D.
Published: October 2005

Relatively little is known about the responses of auditory-nerve fibers to complex sounds such as speech. Although we and others have studied extensively the responses to two-tone stimuli, the extension of these results to speech stimuli has not been attempted. The purpose of this study has been to examine the encoding of steady-state vowels in the auditory nerve. The vowels were synthesized and had a pitch frequency of 128 Hz. In order to characterize the population response, large numbers of fibers (as many as 350) were studied in individual cats. In each experiment, responses of fibers to one vowel were recorded for a number of sound pressure levels. Average discharge rates, interspike intervals, and period histograms were recorded. Average discharge rate was plotted against characteristic frequency of the fibers for each level of vowel used. At low sound levels, such plots show clear peaks for the first and second formants. At higher levels, formant related peaks are not always present. Effects of two-tone suppression are evident in the reduction of the second formant peak at moderate stimulus levels. [Supported by NIH Grant No. NS12112.]
Hair cell abnormality and auditory-nerve physiology
Authors: Liberman M. C. , Beil D. G.
Published: October 2005

Data are presented from 14 animals: 8 acoustically traumatized animals (with survival times greater than one year) and 6 unexposed animals (born and raised in a low-noise environment [Liberman, J. Acoust. Soc. Am. 61, S27(A) (1977)]). Electrophysiological data include threshold tuning curves and spontaneous discharge rates from several hundred single units in each case. Epon-embedded surface preparations of the cochleas were examined with the light microscope. Most of the cochleas showed minimal hair cell losses. Histological analysis also included an evaluation of hair cell condition performed by observers without knowledge of the physiological data. inner and outer hair cells were rated on the appearance of their stereocilia, cytoplasmic and nuclear outlines, and as to the quantity of subapical lysosomes. The histological parameters were correlated with the electrophysiological data for the appropriate region of characteristic frequency (according to a previously developed length-frequency map for the cat cochlea). Most interesting was the correlation between magnitude of threshold shift at CF and abnormalities of either inner or outer hair cell stereocilia. [Work supported by NIH.]
Some preliminary results on clustering for speaker-independent word recognition
Authors: Levinson S. E. , Wilpon J. G. , Rabiner L. R. , Rosenberg A. E.
Published: October 2005

Recently, Rabiner [J. Acoust. Soc. Am. 62, S64(A) (1977)] demonstrated that clustering is a powerful tool for constructing composite reference templates for speaker independent word recognition. This talk will describe a set of specially designed clustering procedures for identifying the structure in training data for a speaker independent word recognition system. The clustering procedures identify coarse structure, fine structure, overlap among clusters and outliers, and can be used interactively or automatically on either multivariate or metric data. The techniques have been applied to a large data base consisting of four repetitions of a 39-word vocabulary spoken by 50 male and 50 female speakers. Preliminary results show that the data is highly structured in a manner such that composite reference templates can be constructed in a natural way. Corroborating evidence of the structure is derived by means of a multidimensional scaling technique. Statistics of the analyses are given which support the hypothesis that the composite templates produced will form the basis for a reference set for a speaker independent word recognition system.
A lattice filter for determining reflection coefficients from autocorrelation coefficients
Authors: Wiggins R. H.
Published: October 2005

One approach to speed analysis by linear prediction involves computing the autocorrelation terms of a windowed speech signal and then applying a transformation to obtain reflection coefficients. It is shown that a recently proposed procedure for this transformation [J. LeRoux and C. Gueguen, IEEE Acoust. Speech Signal Process ASSP253, 257–259] is equivalent to using a lattice analysis filter whose input at t1 is the ith autocorrelation term. This approach has two primary advantages over the usual Levinson recursion algorithm. First, all intermediate quantities lie between −1 and +1. This allows fixed point fractional arithmetic to be used without scaling or block floating point. The other advantage is that this approach has a very simple structure which allows efficient implementation. The equations are derived, the lattice analysis filter described and comparisons are made with alternative approaches.
Design of speaker identification schemes for large number of speakers
Authors: Sarma V. V. S.
Published: October 2005

Design of speaker identification schemes for a small number of speakers (around 10) with a high degree of accuracy in controlled environment is a practical proposition today. When the number of speakers is large (say 50–100), many of these schemes cannot be directly extended, as both recognition error and computation time increase monotonically with population size. The feature selection problem is also complex for such schemes. Though there were earlier attempts to rank order features based on statistical distance measures, it has been observed only recently that the best two independent measurements are not the same as the combination in two's for pattern classification. We propose here a systematic approach to the problem using the decision tree or hierarchical classifier with the following objectives: (1) Design of optimal policy at each node of the tree given the tree structure i.e., the tree skeleton and the features to be used at each node. (2) Determination of the optimal feature measurement and decision policy given only the tree skeleton. Applicability of optimization procedures such as dynamic programming in the design of such trees is studied. The experimental results deal with the design of a 50 speaker identification scheme based on this approach.
Analysis of pathological voices with a sound spectrograph
Authors: Hiki S. , Imaizumi S. , Hirano M. , Matsushita H.
Published: October 2005

Our previous study demonstrated that some acoustical parameters derived by a computer analysis of pathologic voices were useful to differentiate causative diseases to some extent [S. Hiki, S. Imaizumi, M. Hirano, and H. Matsushita, J. Acoust. Soc. Am. 58, S111(A) (1975)]. In this paper, possibility of utilizing a sound-spectrograph for the same purpose was investigated. Voice materials used were sustained vowels uttered by patients of polyp or nodule (42 cases), sulcus vocalis (20), recurrent laryngeal nerve paralysis (33) and cancer (15), and normal speakers (20). Acoustical parameters, which were revealed to be valuable in our previous study, such as degree of the fluctuation of fundamental frequency and that of amplitude, declination of the spectral envelope of harmonic components, and amount of noise components in various frequency ranges were measured from the pattern, section and amplitude display of the sound-spectrograms. The results indicated that sound-spectrographic analysis was of significant value in differenciating the pathological voice from the normal and also in differentiating the voice of cancer from that of the other pathologies.