bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of practice on speeded classification of natural and synthetic speech
Authors: Slowiaczek Louisa M. , Pisoni David B.
Published: October 2005

At the last meeting of the Society in Miami, one of us (Pisoni) presented results from a speeded classification task demonstrating increased processing time for recognition of synthetic speech. In a lexical decision task, we showed an overall increase in response time of 145 ms for synthetically produced words and nonwords over naturally produced control items. Moreover, there was no interaction between signal type and classification response suggesting that the observed differences were due to early stages of perceptual analysis in which the segmental representation is developed from the acoustic-phonetic input. In the present investigation, we were interested in determining whether the observed differences in processing time between natural and synthetic speech could be attenuated or possibly eliminated by practice with the experimental materials and task over several days. We ran ten undergraduate subjects for five days in the lexical decision task. As expected, accuracy improved and latency decreased over the test sessions. However, the relative differences in response latency between natural and synthetic items remained roughly constant. Thus, the earlier differences observed in this speeded classification task are not due to short-term familiarity effects. Rather they seem to reflect real differences in the perceptual and cognitive processes used to extract segmental information from the speech signal. [Supported by a research grant from NINCDS to Indiana University.]
Comprehension of fluent synthetic speech produced by rule
Authors: Luce Paul A.
Published: October 2005

Recent research presented to the Society by Feustel, Luce, and Pisoni [J. Acoust. Soc. Am. Suppl. 1 70, S98 (1981)] showed that recall of synthetic word lists under conditions of increased stress on short-term memory is consistently poorer than recall of natural word lists. In an attempt to extend these findings to the perception and comprehension of continuous synthetic speech, we carried out an experiment in which subjects were presented short meaningful passages of fluent synthetic or natural speech. After presentation of each passage, the subjects were required to answer questions keyed to various levels of linguistic information represented in the passages. The results showed that the synthetically produced passages forced subjects to attend more closely to the physical properties of the speech signal itself. These findings indicate that synthetic speech places increased demands on the cognitive processes involved in comprehension and understanding of meaningful connected speech. [Work supported by grants from NIMH and NINCDS.]
Learning to identify visual displays of speech: A first report
Authors: Greene B. G. , Pisoni D. B. , Carrell T. D.
Published: October 2005

The performance of eight naive undergraduates in learning to identify speech spectrograms was studied over a four-month period. Single tokens from a 50-word PB list were recorded by a male talker. Items were displayed on a Spectraphonics Speech Spectrographic Display system. Identification testing occurred immediately after daily training sessions. With approximately 15 h of training, our subjects could correctly identify the 50 PB words over 95% of the time. Generalization tests with the same words were then carried out with a second token from the original talker, new tokens from another male talker, a female talker, and a synthetic talker. The results showed relatively high levels of generalization performance. Finally, generalization tests to a novel set of PB words using the original talker were carried out. Our initial results demonstrate that even without any training in phonetics or acoustics naive subjects can learn to identify visual displays of speech at very high levels of accuracy. Implications for theories of speech perception and potential applications for the hearing impaired will be discussed. [Supported by NSF.]
An empirical model of the neural output of the cochlea
Authors: Dolan D. F. , Teas D. C.
Published: October 2005

An empirical summation model of estimated Elemental Waveforms (EW) occurring at latencies dependent on Characteristic Frequency (CF) show similarities to the whole-nerve response recorded from the Round Window (RW) of the cat. The cochlear partition is treated as a set of contiguous independent segments. The estimated neural output from each segment is based on the number of discharges from a fiber to a standard stimulus and the number of fibers innervating that segment. The model waveform is generated by the addition of the weighted, summed segmental outputs from 0.5-mm increments along the cochlear partition. The effect of deleting certain segments along the partition upon the output waveform can be compared to the RW response when groups of VIIIth nerve fibers with restricted ranges of CFs are suppressed in Forward Masking experiments. Our initial EWs were diphasic, following the observations reported by Kiang, Moxon, and Kahn (Electrocochleography, edited by Ruben, Elberling, and Salomon, 1976). The effects of varying the duration and shape of the EW will be presented.
ABR measurements in a forward-masking paradigm
Authors: Gorga Michael P. , McGee JoAnn , Walsh Edward J. , Javel Eric , Farley Glenn R.
Published: October 2005

Growth of masking and tuning curves were measured in the cat, using a forward-masking paradigm in conjunction with farfield recording techniques. Probe tones of 3-ms duration (20 dB above ABR threshold) were presented subsequent to 99-ms duration maskers. Masker frequency and level were varied parametrically. Masker and probe were separated by 10 ms and were repeated every 400 ms until 500 responses to the probe had been averaged. The amplitude of the largest component of the ABR (presumably wave V) was measured for each masking condition and then was normalized to the probe response amplitude in quiet. Previous AP data indicated that plots of the decrement in probe response as a function of masker level are similar to single-unit rate-level functions [Abbas and Gorga, J. Acoust. Soc. Am. 69, 492–499 (1981)]. The present ABR decrement functions were steepest for frequencies below probe frequency. This effect is similar to the frequency dependence observed for AP masking data. ABR tuning curves (threshold = 50% decrement) were similar in shape to AP tuning curves although they tended to be less sharply tuned. Still, these data indicate that farfield techniques can be used to estimate response growth and frequency resolution. [Supported by NIH Grants NS14880 and NS07147.]
Sound reflection from a fluid-loaded and masked elastic plate
Authors: Jackins P. D. , Gaunaurd G. C.
Published: October 2005

We have extended available computer codes that predict the classical reflections and transmissions of sound fields through sets of plane elastic layers [i.e., D. Folds and C. Loggins, J. Acoust. Soc. Am. 62, 1102–1115 (1977)]. The present layers separate possibly dissimilar fluids, are possibly viscoelastic, and are insonified from one side. The results we display include reflection (R) and transmission (T) coefficients as functions of frequency f and incidence angles θ. This computational tool has been used to predict the reflections from a single fluid-loaded elastic plate ideally covered with a lossy layer of homogeneous viscoelastic material, insonified from the coated side. Resonances in the coefficients are analyzed in the light of the resonance scattering theory (RST), which has not yet been applied to coated plates. The present model serves to assess the effectiveness of the masking layer to reduce the reflections from the metal plate. The predicted displays of calculations are presented for values of the material parameters in the ranges commonly found in practice. The lossy nature of the absorbing layer complicates the otherwise real parameters present in the analysis, and we quantitatively determine the shifts in resonance locations, the widening of the resonance peaks, and the overall reduction of the returned reflections caused by the masker's viscoelasticity.
Some acoustic aspects of early imitation of speech: F0 and vowels
Authors: Lieberman Philip , Ryalls John , Rabson Steve
Published: October 2005

A Japanese mother and her infant son were recorded on high quality equipment in the home setting. The imitative utterances of the infant were analyzed acoustically and compared to the mother's. The intonation contours from age five weeks were found to reproduce acoustic characteristics of F0 frequency, pattern, and duration; apparently in that order of acquisition. It was also found that the mother raised her F0 from an average of 185 Hz to an average of 325 Hz when interacting with her child. 325 Hz is within the infant's own F0 range, apparently facilitating imitation. At approximately 11 weeks the child also began to spontaneously produce vowel sounds, and to imitate his mother's vowels. The infant vowels were frequency scaled, and not simple acoustic matches. The child could have reproduced some of his mother's vowels almost exactly, but instead finds a phonetic equivalence in an acoustic vowel space that is appropriate to his smaller supralaryngeal vocal tract. [Work supported by NICHHD.]
Final-word lengthening in Spanish
Authors: de Manrique A. M. B.
Published: October 2005

In an ongoing work about segmental duration and rhythm in Spanish it was observed that not only final vowels were lengthened but also many final-word segments seemed to be elongated. The present paper was undertaken in order to quantify this effect. A set of words which occurred in utterance final position, in utterance nonfinal position, and prior to a major constituent boundary were chosen. All syllables were open, bearing the penult syllable the stress. Results showed that the elongation was of different magnitude across the final-word segments. The greater increment was observed in the final-syllable vowel (mean final-nonfinal ratio: 2.03). The lengthening of the penult syllable may be attributed to the stress, to the positional condition or to both factors. Results showed that penult-syllable elongation was due to a positional factor in the consonant case and to both factors, stress and position, in the vowel case. It was also observed that preboundary words were longer than nonfinal but somewhat shorter than final words. Preboundary words also showed various degrees of lengthening.
The functional specificity of articulatory control and coordination
Authors: Kelso J. A. Scott , Tuller Betty , Fowler Carol A.
Published: October 2005

Favored interpretations of “compensatory” movements of the lips to unanticipated resistances applied to the jaw during a closing gesture have focused on afferent feedback control [e.g., Folkins and Abbs (1975)] or feedforward, open-loop control processes [e.g., Abbs and Cole (1982)]. The present experiments sought to identify and analyze, using dynamic perturbation techniques, functional constraints among several articulators when they cooperate to produce n desired utterance. A brushless DC torque motor coupled to the subject's lower teeth via a custom-made prosthesis was programmed to inject a 500-g torque load to the jaw for 1.5 s during the vowel-consonant transition in /baeb/ and /baez/ on 20%–25% of trials. Infrared L.E.D.s were attached to the lips and jaw and monitored using a modified SELSPOT optical tracking system. In experiment 1, increased downward displacement of the upper lip occurred in perturbed conditions for /b/ (p < 0.01) but not for /z/. Experiment 2 replicated this result and also showed, through hooked wire electrode recordings from a tongue muscle, a significant increase in electromyographic activity for /z/ prior to occlusion, but not for /b/. Closure and frication were attained on all trials without any obvious changes in timing. These highly distinctive patterns suggest that the jaw, lips, and tongue may be controlled and coordinated as a single, functional unit (a coordinative structure) that is unique and specific to the intended act. [Work supported by NINCDS and BRSG.]
Variability of tongue muscle activities and its implications
Authors: Honda Kiyoshi , Baer Thomas , Alfonso Peter J.
Published: October 2005

We have collected a large amount of simultanenusly recorded tongue EMG data [P. J. Alfonso et al., J. Acoust. Soc. Am. Suppl. I 71, S54 (1982)]. The study reported here is based on these data and further investigates the coordination of the tongue muscles in static and dynamic conditions during vowel production. We examine the variability of the data associated with F0 change. We also examine the intercorrelations among these muscles in terms of token-to-token EMG variability. Since the tongue consists of a network of muscles, an articulatory gesture uses coordinated activities of multiple muscles. In repetitions of tokens, relative activities of the muscles vary with each other. These variabilities provide a view on the organization of muscular control of the tongue. The preliminary analysis demonstrated that when the genioglossus showed increased activity during high-pitched /i/, the antagonistic muscles (the hyoglossus and the styloglossus) showed some increased activities while the agonistic muscles (the mylohyoid and the geniohyoid) sometimes showed relatively low activities. This implies that these variabilities are regulated in order to maintain the noncompressive approximation of the tongue. [Research supported by NINCDS.]
Lingual kinematics and acoustic durations
Authors: Parush Avraham , Munhall Kevin G.
Published: October 2005

In a previous paper [J. Acoust. Soc. Am. Suppl. I 71, S105 (1982)] we showed that in /pVCVp/sequences, the duration of the lingual V1C transition was inversely related to the lingual displacement for the CV2 transition, while the displacement and maximum velocity of CV2 were inversely related to the displacement of V1C. Relationships among acoustic durations and these kinematic variables were examined further. The acoustic duration of V1 was related to the duration of the V1C transition, while the duration of V2 was related, less consistently, to both the duration and displacement of the CV2 transition. The duration of V1 (V1 = /a/) was negatively related to the displacement of CV2, but the duration of V2 was not systematically related to the displacement of V1C. In addition, movements toward closure, relative to V1 acoustic onset, started earlier for greater V1C displacements. Movements toward V2, relative to V1 acoustic offset, started earlier for greater CV2 displacements and maximum velocities. Further, closure duration was negatively related to the displacement and maximum velocity of the CV2 transition. Coproduction of vowels and consonants will be discussed.
Focusing and diffraction of backscattering from fluid spheres: Comparison of the partial-wave sum with a model
Authors: Marston Philip L. , Langley Dean S.
Published: October 2005

Consider the scattering of a plane wave from a sphere of radius a imbedded in a fluid with a sound speed c0 = Mci. Backscattered rays with impact parameters b ≠ 0 are known as glory rays; their contributions fn to the total normalized form function f are enhanced due to axial focusing. Naive application of ray acoustics predicts that |fn|→∞ as γ→0 where γ is the angle relative to the backward axis. We derive an approximation which removes this divergence and describes the effect of diffraction on axial focusing. It is similar to our model for the optical glory of bobbles [D. S. Langley and P. L. Marston, Phys. Rev. Lett. 47, 213–916 (1981)] and it gives |fn| = (ka)1/2Gn|J0(kb sinγ)|, where k is the wavenumber and Gn is a function of the number of internal chords n and of fluid properties. The modeled f is obtained by interfering several fn with axial reflections. It was compared with an exact partial-wave sum for f with ka = 100 and 1000 and various M < 1; our model correctly describes the main features. A strong additional enhancement of f(γ = 0) is present when. M≈1.180 due to a coincidence of n = 3 glory and rainbow rays. [Work supported by ONR. Marston is an Alfred P. Sloan Research Fellow.]
Convergence and the choice of expansion functions in the T-matrix approach
Authors: Green L. H. , Werby M. , Flax L.
Published: October 2005

In the context of electromagnetic scattering problems, Waterman [P. C. Waterman, Survey of T-Matrix Methods, in Acoustic, Electromagnetic and Elastic Wave Scattering, edited by V. K. Varadan and V. V. Varadan (Pergamon, New York, 1980)] has considered several different choices of expansion functions for the surface currents, when applying the T-matrix approach. We will consider the scattering of plane acoustic waves incident upon finite elastic bodies. How different choices of the expansion functions for the surface displacements affect the rate of convergence of the elements of the T matrix and the form function will be presented. Both spherical and nonspherical elastic bodies will be considered.
Extended high tone hearing performance (0.25 to 20 kHz) in orchestral musicians with unremarkable hearing health histories
Authors: Johnson David W. , Aidridge Jeffrey H. , Sherman Robert E. , Lorraine Adele
Published: October 2005

Thirty-four members of the Minnesota Orchestra were evaluated otologically and audiologically for hearing acuity for the frequency range 0.25 to 20 kHz. Members were grouped by age and sex. Median hearing thresholds for each group for each frequency were calculated and compared to currently available presbycusis tables for the frequencies 0.25 to 8 kHz and to statistically generated age/sex thresholds for the frequencies 9 to 20 kHz. An analysis of individual and median audiometric configurations for each age/sex group explored potential relationships between instrument and position in the orchestra and audiogram. Generally, median performance curves showed a “noise notch” at 6 kHz and decrease of hearing acuity with age for all frequencies, but decrease was most dramatic in the extended high tones (9 to 20 kHz). Certain musician types did demonstrate greater characteristics of noise induced hearing loss. [Work Supported by the Minnesota Foundation for Acoustical Education and Research.]
Perceptual errors arising from the use of multiband nonlinear hearing aids
Authors: Dillon Harvey , Walker Gary , Byrne Denis
Published: October 2005

Tests were performed of the intelligibility of nonsense monosyllables processed by a computer-simulated multiband hearing aid incorporating compression for high level signals and expansion for low level signals in each band. The overall results indicated that the nonlinear system led to slightly better intelligibility for some subjects at some presentation levels, but otherwise led to equal performance or was even disadvantageous. A traditional examination of the confusions (place/manner, initial/final, vowel context) only revealed that all such subclasses were affected to a similar extent. Examination of the responses to individual items, however, revealed that the perception of a considerable number of items was made consistently better by the processing, while that of others was made consistently worse. Acoustical analysis of these items before and after processing indicated that band-edge effects (which modified formant transitions), and the time dependent frequency response (which either enhanced or degraded the characteristic spectral shapes of bursts and fricatives) were responsible for many of the changes in perception. A processing scheme which uses parametric serial filtering and cross-band gain control signals, which may overcome these problems, has been developed.
The use of a control microphone in reverberent sound field audiometric testing
Authors: Dillon Harvey
Published: October 2005

Traditionally, sound field stimuli are “pre-calibrated” at a particular point in the room. Head diffraction effects are thus automatically taken into account when measurements are performed. However, the method is potentially innacurate for two reasons. First, the head diffraction effects measured are dependent on the particular test situation. Second, subjects tend to move away from the pre-calibrated point. An alternative technique is to continuously monitor the SPL in the vicinity of the subject by using a control microphone attached to the subject's head. The method has the advantage that the calibration point then moves with the subject. However, it has the disadvantages that the SPL at the control microphone is not the same as the SPL at the point of interest (hearing aid microphone or eardrum), and that average head diffraction effects must be assumed. Experiments were performed using probe microphones and control microphones in various locations on six adults and a manikin (KEMAR) using both calibration techniques. A quantitative examination of the sources of error in both procedures revealed the control microphone technique to be superior, especially when assessing aided hearing.
Contributions of sub-audio frequency modulation and spectral envelope constancy to spectral fusion in complex harmonic tones
Authors: McAdams Stephen
Published: October 2005

Spectral fusion is a process by which elements of sound are grouped into unified auditory source percepts. The grouping processes use acoustic cues such as the presence of sub-audio frequency modulation, its coherence among spectral components and the constancy of the spectral envelope. Both periodic (vibrato) and random (jitter) modulation can contribute to fusion. The rms deviation of modulation must be greater than the modulation detection threshold found for these complex tones (16 harmonies of 220 Hz). When the modulation imposed on the ensemble of spectral components is incoherent or does not maintain the harmonic relation (i.e., is not proportional to frequency for all harmonics), less fusion is perceived. There are indications that the detection of coherence of modulation occurs in the higher harmonic numbers. Those modulations which mitigate against fusion also contribute to an increase in spectral resolution. The spectral resolution indicated in these experiments appears to bc greater than that for unmodulated signals classically reported. With more complex spectral envelopes, like vowels, a greater degree of fusion is reported when the spectral envelope is constant, i.e., a concurrent amplitude modulation accompanies frequency modulation and “traces out” the spectral envelope. This may indicate that grouping processes favor fixed-resonance structures. Musical examples illustrating the use of these principles in computer synthesis will be played.
Chrome and interval in melody recognition: Effects of acquiring a tonal schema
Authors: Dowling W. Jay
Published: October 2005

Pitch intervals of melodies in long-term memory are produced and recognized quite accurately by both musicians and nonmusicians. This could be either because memory represents intervals directly, or because pitches are represented as chromas in a tonal scale schema (a do-re-mi-like representation). Changing chromes (but not intervals) of test melodies should disrupt recognition in the latter case, but not the former. Here I controlled chrome by introducing each melody with a chord sequence that ended with either a tonic (do-mi-sol) or dominant (sol-ti-re) chord. The melody was constructed around the root of that chord (do or sol). Recognition was tested with transpositions that either preserved or changed chord context. Listeners tried to distinguish between exact (interval-preserving) transpositions and near transpositions having one pitch altered. Inexperienced listeners succeeded whether chroma changed or not. Moderately experienced listeners succeeded only when chroma was preserved. The latter store melodies in terms of chromas and have difficulty recognizing them when chromas are changed. This result converges with others relating schema use and musical experience.
Intrinsically irreversible acoustic heat engine
Authors: Wheatley John C.
Published: October 2005

Thermodynamic effects will be described associated with structures placed within a gas contained in an acoustically resonant tube. For suitable geometries and frequencies substantial temperature differences, perhaps 50 times the adiabatic temperature changes in the gas, can be produced. The experiments can be understood in a context of certain principles, including the principle of broken thermodynamic symmetry, which describe intrinsically irreversible reciprocating heat engines. [Work supported by LANL and by the D.O.E.]
Ultrasonic studies of mechanical properties of materials
Authors: Granato A. V.
Published: October 2005

In recent studies, the close relationship between ultrasonic attenuation and the plastic flow of solids has become more explicit. Both depend sensitively upon the details of dislocation-defect interactions. The interactions can be separated into those producing pinning and those producing viscous drag. Deformation behavior can be classified according to the strength of the drag. For small drag, as in superconductors, inertial effects become important. For intermediate drag, traditional theories resting on rate theory treatments become applicable. For large drag, viscoelastic behavior is obtained. Measurements are examined for information concerning the basic nature of different sources of short- and long-range pinning and of drag.
When is a [p] a [t], and when is it not
Authors: Pastore Richard E. , Szczesiul Rosemary , Rosenblum Lawrence D. , Schmuckler Mark A.
Published: October 2005

Under certain dichotic listening conditions the initial stop [p] in a naturally spoken word may be perceived as [t]. The words were monaural with Gaussian noise in the contralateral earphone. Both naive subjects and knowledgeable subjects provided a psychophysical mapping of the conditions necessary for the transformation. The transformation occurs only in the context of certain vowels (occurring consistently in the words “pam,” “pat,” and “par”). The intensity, relative temporal onset, and to a lesser extent, the duration of the contralateral noise, are important parameters. The phenomenon clearly is dependent upon dichotic fusion. When the stimuli were mixed and presented monaurally, subjects either correctly reported the nature of the mixed stimuli (for low noise intensities) or reported hearing the noise plus the word without an initial consonant (for higher noise intensities acting as a masking stimulus). There are considerable individual differences in the tendency to perceive the transformation. To date we have not found any conditions where the dichotic noise will alter the perception of an initial [t] or [b] other than in a strictly masking-type fashion. [Research supported by NSF grant BNS-8003704.]
Multidimensional scaling analysis of symmetric and nonsymmetric consonant confusion matrices: A comparison of different proximity measures
Authors: Yuchtman Moshe , Bilger Robert C.
Published: October 2005

In a recent paper [Yuchtman and Bilger, J. Acoust. Soc. Am. Suppl. 1 71, S75 (1982)] we reported that two proximity measures, namely, Ln S [Soli and Arabie, J. Acoust. Soc. Am. 66, 46–59 (1979)] and the index of sensitivity, d′, yielded similar multidimensional solutions in SINDSCL analysis of consonant confusion matrices. We have now studied these measures in a comparative analysis of symmetric and nonsymmetric consonant confusion matrices, expecting differences between Ln S and d′, since the first measure, unlike the second assumes matrix symmetry. 48 consonant confusion matrices of 24 subjects were analyzed. For each subject stimuli were presented with presence of noise or in the quiet in procedure similar to the one described by Wang and Bilger [J. Acoust. Soc. Am. 69, 832–845 (1973)]. An index of symmetry was obtained for each matrix by using the procedure suggested by Hubert and Baker [Qual. Quant. 13, 77–84 (1979)]. The 12 matrices with the highest or lowest symmetry scores were subjected to further analysis. For each of these matrices we calculated three proximity measures: S, Ln S, and d′. They were then analyzed using the SINDSCL program. The results indicate that: (1) for all of these measures, a given n-dimensional configuration accounted for larger proportion of the variance in the high-symmetry than in the low symmetry matrices; and (2) for both types of matrices, d′ and Ln S accounted for roughly the same proportion of variance which was higher than that yielded for S. We are now analyzing the specific solutions obtained for each of these measures. [This work was supported by NINCDS.]
Monitoring strategies for acoustic remote sensing of the Florida Current
Authors: Palmer D. R. , Lawson L. M. , Chong Y. H.
Published: October 2005

In designing an acoustic system of monitoring the mass transport of the Florida Current, one is immediately faced with two, intimately related, problems. First, how does one determine which source/receiver configuration is optimal? And, second, what role does supplementary observations from nonacoustic systems play in the design and use of an acoustic system? This paper reports on our progress in developing a methodology for answering questions of this type. We describe an observational system, acoustic and/or nonacoustic, in terms of its “sampling region,” i.e., the portion of the cross-sectional area of the Straits that it monitors. A very fast, specialized ray-tracing computer program is used to determine the sampling region for an acoustic system. Within the sampling region a system is assumed to provide an estimate of the current. Given these estimates, linear optimization theory is used to obtain an estimate for the transport. The linear coefficients which appear are determined by requiring that the mean-square error in the transport be a minimum. This minimum error, which serves as a measure of performance for the system, depends on the sampling region and sampling errors as well as on the environment through the covariance matrix for the current fluctuations.
Ocean features observed from manned spacecraft that influence acoustics in the upper ocean
Authors: Stevenson Robert E.
Published: October 2005

Ocean fronts, eddies, and internal waves have been observed, photographed, and imaged by synthetic aperture radar during the first four orbital missions of the space shuttle, Columbia. Supporting data show that the visual features correspond to thermal discontinuities, have significant vertical extensions, act as barriers to underwater acoustics, and can be detected by synthetic aperture radar regardless of sky conditions or time of day. Although one thinks of these sea-surface manifestations as having a certain ubiquity, presently available information seems to show that they are concentrated both generically and geographically. This concept is to be addressed from Columbia and Challenger during 1983.
Connection between acoustic and electromagnetic sea-surface backscatter
Authors: McDaniel Suzanne T.
Published: October 2005

The performance of active high-frequency acoustic systems operating under water is, in many cases, limited by backscattering from the sea surface. The strength of surface reverberation has been experimentally found to depend on the speed of the wind driving the ocean waves, while the Doppler spread of the scattered signals has been related to the waveheight. Electromagnetic sea-surface backscatter may be used to remotely sense the ocean surface and, hence, provides a means of empirically predicting the properties of acoustic reverberation. We investigate the relationship between acoustic and electromagnetic surface backscatter. The physical mechanisms responsible for acoustic backscatter are discussed and the extent to which the relevant oceanic parameters may be extracted from electromagnetic backscatter data is assessed. It is concluded that electromagnetic remote sensing of the ocean surface provides a viable means of predicting both the strength and Doppler characteristics of underwater reverberation.
Holographic measurement of tympanic membrane vibrations
Authors: von Bally G.
Published: October 2005

Different holographic methods have been used for high resolving, contactless, 3 D analysis of tympanic membrane vibrations [G. von Bally, Ed., Holography in Medicine and Biology (Springer, Berlin, 1979)]. Most experiments have been performed in-vitro for basic research on the transfer function of the middle ear. We have chosen double-exposure holography using a Q-switched ruby laser system, a (vibration-) phase sensitive technique which allows applications in-vivo. For simultaneous sound presentation and holographic recording of the elicited tympanic membrane vibration through the outer ear canal in humans, special closed acoustic systems were developed. Thus, it was possible to determine a vibration pattern in patients with regular middle ear status, which characteristicly depends on amplitude, frequency, and phase of the stimulus. Specific deviations from this “normal” vibration pattern were determined in investigations on patients with pathologically altered middle ear mechanics, proving the applicability of this method for diagnostic purposes. Increased feasibility for clinical use was achieved with flexible fiber optics for convenient positioning of the acousto-optical system and the use of otoscopic optics for easy optical access to the tympanic membrane. [Supported by Deutsche Forschungsgemeinschaft SFB 88/B3.]
Optimum transducer parameters for broadband applications
Authors: Marshall William J.
Published: October 2005

A general method for making top-level sizing and design decisions for broadband transducers is presented. The realm of application is that of body force transducers having small radiating area at resonance. By “broadband applications” we mean that the system requirement driving the design is the shape and magnitude of the constant-voltage acoustic spectrum. The design method yields the optimum Qm and resonance frequency to meet the specified acoustic performance for given constraints on transducing material. The theory is illustrated by applying it to two common spectral shapes: white and pink noise of arbitrary bandwidth.
Development of a dual mode transducer array
Authors: Schmidt Richard L. , Lindberg Jan F.
Published: October 2005

A task was initiated to develop a sonar system sensor which permitted both conventional and parametric beam formation. Available space constraints and required acoustic power densities demanded that the conventional and parameteric signals be generated from the same transducer array. Extensive studies are reported that document simulations and experiments undertaken to determine the best parametric primary frequencies. A dual-mode transducer was developed to generate both conventional and parametric signals. The transducer has the capability of high power transmission at two separate frequencies almost 2.5 octaves apart with broad bandwidth at both frequencies. The low-frequency transducer is a traditional Tonpliz with its head mass comprised of a multitude of nodally mounted high-frequency transducers which generate the parameteric signal. The nodal plate of the high-frequency transducer permits the low-frequency transducer to transmit acoustic energy to the medium without transversing the acoustic pressure release of the high-frequency transducers. Data are shown of the performance of a small partial array of these transducers.
Analytical formulation and experimental study of the properties of piezopolymer transducers using shell-or membrane-dome structures
Authors: Ravinet P. , Micheron F. , Guillou D. , Claudepierre C.
Published: October 2005

Dome shaped piezopolymer transducers can be considered as membrane or shell structures, depending on the thickness of the thermoformed film. We report an analysis of the mechanical behavior of such structures, taking into account both the extensional and flexural effects, and leading to a formulation of their acoustic mass and compliance and of the frequency of their first resonance mode. The microphone sensitivity and the transmitter efficiency are then, respectively, derived from the stress field induced by an applied pressure and from the relative change of radius of curvature due to an applied electrical field. These predictions are more specifically applied to the optimization of telephone microphones and receivers. It is shown that the product of the microphone sensitivity by the square of the resonance frequency and the radius of curvature is a function of material parameters only. Maximal receiver efficiency is ascribed to the piezoelectric coupling factor of the material. Experimental results will be presented, concerning such transducers using home made piezopolymer PVF2 in shell or membrane structures. [Work sponsored by DAII.]
A-weighting for assessment of highway noise impact
Authors: Wilson Charles E.
Published: October 2005

Exposure to transportation noise sometimes results in unacceptable noise levels inside residential and office buildings. Underprediction of intrusive noise can result from the frequency characteristics of building attenuation and from room effects when low-frequency tones are prominent at the source. The significance of A-weighting in relation to this problem is investigated through simultaneous measurements of indoor and outdoor noise.
Self-de-excitation of water vapor: Monomer and dimer contributions
Authors: Zuckerwar Allan J.
Published: October 2005

Past efforts to interpret experimental data on the de-excitation rate of the v2(1→0) vibrational mode of water vapor have been thwarted because of the attempt to fit the data to a single relaxation time. In a phenomenological theory proposed here the de-excitation takes place by means of two parallel reactions: (1) the conventional collisional de-excitation of the monomer and (2) a two-step reaction involving association and re-dissociation of the dimer. The resulting relaxation equation yields two coupled relaxation times. In pure H2O and in mixtures without O2, the reaction rate for dimer association is taken to be very slow, and the relaxation modes are effectively decoupled: the first corresponding to de-excitation of the monomer and the second to spontaneous dissociation of the dimer. In mixtures of H2O-air and H2O-O2, the association rate of the dimer is found to increase strongly, suggesting that O2 serves as an effective “chaperon” for this reaction, and the relaxation modes of the monomer and dimer become strongly coupled. Fourteen sets of past data, representing a wide variety of test conditions and experimental methods, both acoustical and nonacoustical, are organized into three groups—each corresponding to a relaxation mode predicted by the theory.
The effect of polymer additives on cavitation inception in water
Authors: Brosey James E. , Crum Lawrence A.
Published: October 2005

Measurements are presented of the variation of the acoustic cavitation threshold of water with concentration of the polymer additives polyethylene oxide and guar gum. It was found that small amounts of these additives could significantly increase the cavitation threshold. A theoretical model, based upon nucleation of a gas bubble from a Harvey-type crevice in a mote or solid particle, is developed that gives good agreement with the measurements. The applicability of this approach to an explanation of cavitation index reduction in flow-generated or confined jet cavitation, when polymer additives are introduced, is discussed. [Work supported in part by the ONR and the NSF.]
Stress waves induced in graphite-epoxy composite structures by current pulses
Authors: Chamuel Jacques R.
Published: October 2005

A technique to generate ultrasonic waves in graphite-epoxy composite structures using electrical current pulses flowing in the structure is described. The difference between the thermal expansion coefficients of graphite and epoxy create large stress waves in response to localized heating by current pulses flowing in the individual graphite fibers. Experimental results are presented demonstrating the applicability of the method to nondestructive testing problems. The anisotropic elastic and electrical properties of a T-300 graphite/DER-332 epoxy composite plate were determined. In the experiments, a piezoelectric receiver transducer was used to detect the thermoelastic waves in the composite plate. Distinct ultrasonic waves were detected with 20 μsec current pulses below 50 mA.
Theory of ultrasonic harmonic generation in hexagonal crystals
Authors: Philip Jacob , Breazeale M. A.
Published: October 2005

The expressions for ultrasonic wave propagation in nonlinear hexagonal crystals are derived. Specialization of the equations reveals that in the linear approximation the waves propagate as pure modes in the basal plane and along the symmetry axis. Introduction of the nonlinear terms causes the transverse modes to couple to the longitudinal modes, so that they are no longer pure. Hence, the transverse modes would be difficult to measure. The longitudinal modes, on the other hand, remain pure modes but are coupled to their higher harmonics. Measurement of longitudinal harmonic generation, then, is an interesting possibility. The equations are solved for different directions in the basal plane as well as along the c axis, and expressions are obtained for the nonlinearity parameters in terms of third-order elastic constants. In the basal plane, the amplitude of the second harmonic is maximum in the [100] direction and minimum in the [010] direction with the average of the two in the [110] direction. Comparison of these results with cubic symmetry is presented. [Research supported by the Office of Naval Research.]
A variational method for wave propagation and scattering in discrete random media: The coherent field for scalar waves
Authors: Andreo Robert H.
Published: October 2005

The propagation and scattering of scalar waves in a random medium of particles is analyzed from a variational point of view. Using an arbitrary set of basis functions, multiple scattering equations are obtained for the multipole coefficients in terms of the single-particle transition matrix elements and the matrix elements of the Helmholtz-Green function. Comparison is made with the method of moments and the method of weighted residuals. Closure hypothesis lead to algebraic equations for the coherent scattered field and integral equations for the coherent exciting field. With suitable assumptions on the pair correlation function, dispersion relations can be obtained which characterize the effective macroscopic random medium in terms of an experimentally measurable phase velocity and attenuation coefficient. Examples are discussed, with emphasis on the physical role of the pair correlation function and the mathematical role of the closure hypothesis. [Work supported by NAVSEA and ARO.].
Current developments in automatic adaptive control of noise
Authors: Warnaka Glenn E.
Published: October 2005

Modern solid-state electronics and control theory allow active control of noise by the carefully controlled generation of out-of-phase cancellation signals from loudspeakers. Active control of noise is rather easily applied to the problem of noise in ducts where the waves are constrained to be one dimensional. However, with careful consideration of the acoustical parameters, active noise control can also be applied to two- and three-dimensional problems.
Adaptive active sound control
Authors: Burgess John C.
Published: October 2005

Adaptive signal processing has been used to cancel echoes in telephone networks and to improve signal-to-noise ratios in measurement systems. Adaptive methods offer the potential for significant improvement over existing methods for active sound and vibration control. Adaptive methods can accommodate feedback with transport delay, operate over a broad frequency range, and adjust to uncontrollable system parameters such as changes in fluid velocity, fluid temperature, and component aging. A computer simulation shows feasibility for adaptive active sound control in a duct [J. C. Burgess, “Active adaptive sound control in a duct: A computer simulation,” J. Acoust. Soc. Am. 70, 715–726 (1981)].
A new digital technique for the measurement of mechanical vibration
Authors: Rasmussen Gunnar
Published: October 2005

The two-channel FFT analyzers have revolutionized the measurement technique used for mechanical measurements. Recursive digital filter technique is in general use within acoustics. However, the true real time capability, eliminating the use of window functions like f.ex. Hanning along with born logarithmic frequency scale, offers great advantages for the measurement of mechanical vibrations. The measurement of vibrational net power flow, vibration modes and stress intensity by mechanical transducers will be discussed.
The use of satellite data for the detection and estimation of large acoustic anomalies caused by ocean currents
Authors: White James V. , Brammer Robert F.
Published: October 2005

The Seasat-A satellite carried a radar altimeter and a microwave scatterometer that provided nearly global data sets on sea surface height, significant wave height, and sea-surface wind velocity. These data, and similar data from future satellite missions, can be used to estimate ocean parameters that effect underwater sound generation, propogation, and surface scattering. This paper describes a matched-filter technique for using altimeter data to detect, locate, and estimate the sizes of large coherent acoustic anomalies caused by mesoscale (50 km–500 km) rotating current rings. These ring currents are spawned by the Gulf Stream, have lifetimes ranging from several months to two years, and produce characteristic sea-surface height signatures in the altimeter data. A technique for processing the altimeter data to estimate sound-speed profiles in cold-core current rings is discussed, and results for representative ring currents are presented.
A syllable parsing algorithm for telephone-quality speech
Authors: Kahn D.
Published: October 2005

This paper describes an algorithm for the automatic parsing of continuous speech into a string of syllables, intended for use as the “front end” of a demisyllable-based continuous speech recognizer. The algorithm takes an input an autocorrelation coefficient (ACC) parameterization of speech, an analysis independently required for our recognition process; it makes use of only the zeroth-order ACC (energy) and normalized first-order ACC. Local maxima in a severely low-pass-filtered representation of the energy signal determine potential syllabic nuclei. Some of these first-pass syllables are discarded on the basis of further tests. Compared to other syllable parsers described in the literature, this algorithm (1) was designed and tested for use with telephone speech, i.e., utterances spoken into a carbon microphone over a dialed-up phone line and bandpass filtered to 200–3200 Hz; (2) locates potential syllabic nuclei by reference to the simple energy signal, rather than to a spectrally weighted “loudness” transformation of energy; (3) differs in many details of the true/spurious syllable decision process. Performance data for the algorithm will be presented, as will a tape recording of examples of the rather carefully spoken but truly continuous speech used to evaluate it.