bluuebunny/crossref_metadata_2025 huggingface dataset:
A linear inverse scheme for the extraction of ocean bottom geoacoustic parameters from modal eigenvalues
Authors: Rajan S. D. , Wengrovitz M. S. , Lynch J. F. , Frisk G. V.
Published: October 2005

Shallow water theoretical and experimental results recently obtained by Frisk, Lynch, Wengrovitz, and Rajan [G. V. Frisk and J. F. Lynch, J. Acoust. Soc. Am. 76, 205–216 (1984)] indicate that one can perform a relatively simple cw surveying experiment which would, after processing of the data via the Hankel transform, yield both the discrete and continuous modal spectra. Extraction of bottom geoacoustic information can then be accomplished by applying linear inverse theory (e.g., the Backus-Gilbert approach) to the eigenvalues thus obtained. Specifically, one deals with a mathematical form derived from first-order perturbation theory, di = ∫0ZmaxGi(z)m(z)dz (i = 1,2,3,…,N), where di represents data (the modal eigenvalues), Gi(z) is the kernel for some initial guess model (currently taken as a Pekeris waveguide, but not restricted to it), and m(z) stands for a profile of some quantity (such as velocity or density) in our desired earth model minus the profile for our initial model. Results of preliminary inversions for typical bottom velocity profiles will be presented, as well as discussion of other topics of interest such as attenuation, density profiles, and resolution criteria. [Work supported by ONR.]
Cross-linguistic differences in diphthongs
Authors: Lindau Mona , Norlin Kjell , Svantesson Jan-Olof
Published: October 2005

Similar diphthongs may vary cross-linguistically in terms of the relative duration and slope of the transition between the onset and offset of the diphthong. At moderate rates of speech this transition will constitute the major part of the diphthong in some languages, while in other languages it will be quite fast. In /ai/ the transition occupies about 60% of the total duration in American English; about 50% in Peking Chinese; but about 15% in Egyptian Arabic. In the diphthong /au/ the transition takes up the major part (about 75%) of the total duration in American English, while in Arabic and Hausa it is only about 25% of the total duration. The different transitional durations do not correlate with the total duration of the diphthong. Nor is the explanation to be sought in the phonologies of the different languages. We have also found that in Hausa and Arabic, where the diphthongs have sharp transitions, the movements of the first and second formants are not synchronous. The transition of the first formant lags behind the second formant transition by some 15–20 ms. This lag in the first formant is also evident for some speakers of American English and Chinese /ai/ and /au/. [Work supported by NSF and The Swedish Council for the Humanities and the Social Sciences.]
Movements of the mandible and hyoid body during speech
Authors: Westbury John R.
Published: October 2005

The mandible provides a mobile foundation for the tongue and lips, and may move synergistically with them to modulate the length and shape of the vocal tract during speech. It is loosely coupled to both system components, more massive than either, and consequently may significantly influence the character and temporal coordination of their movements. Therefore, it is of general interest to describe mandibular movements during speech, and the means by which they are achieved. A high-speed (100 fps) cinefluorographic film was analyzed to determine sagittal-plane rotational and translational movements of the mandible and hyoid body, relative to other craniofacial bones. These data were then used to derive time functions approximating the lengths and orientations of various muscle resultants which flex and extend the mandible about the skull. The speech inventory, recorded by one adult male speaker of American English, consisted of isolated nonsense disyllables containing intervocalic singletons and selected clusters derived from the consonants /p,t,k,b,d,g,m,n,/ in the frame /pa_at/. Sample observations derived from the data base include: (1) For kinematic purposes, the hyoid bone may generally be represented in terms of a particle, at least during utterances which do not contain a velar consonant. (2) The lengths of suprahyoid muscles rarely differ from their “resting lengths” by more than 10%. Interestingly, their lengths may increase during intervals when the mandible is being “lowered.” Additional observations will be discussed, particularly insofar as they relate to temporal variations in factors affecting the force-generating abilities of the mandibular muscles.
The relationship between jaw muscle activity and jaw movements during speech
Authors: Gentil Michèle , Gay Thomas
Published: October 2005

The activity patterns of the mandibular elevator muscle system were investigated for speech gestures. Intramuscular wire electrodes were placed into the seven elevator muscles of the mandibular system. The activity of these muscles was recorded along with the jaw displacement in two-dimensional space (vertical and anterior-posterior) and the acoustic signal. One adult, native speaker of French, produced different CVC syllables (C = /p/ or /b/, or /t/ and V = /i-ɛ-a-u-o/) each produced in a carrier phrase at two different speaking rates. Results indicated that intraindividual differences exist in the selection of a given muscle or muscle system for a specific function and/or utterance and in the coordination of muscle activity pattern for a particular gesture.
Development of lip and jaw control in the speech of children
Authors: McLean-Muse Ann , Smith Bruce L.
Published: October 2005

Since previously reporting preliminary findings concerning lower lip and jaw velocity and displacement during the production of labial consonants by four children and three adults [B. L. Smith and T. Gartenberg, J. Acoust. Soc. Am. 75, 1599–1605 (1984)], we have collected additional data from ten children in each of three age groups (5, 8, and 11 years of age) and from ten adults. Subjects produced five repetitions of each of the consonants [p, b, f, v, m] in different vowel environments (N = 100 utterances/subject). Velocity and displacement were measured for closing and opening gestures for upper lip, lower lip, and jaw. Based on results from six subjects/group, the children were found to move their articulators about 15%–25% more slowly than the adults, but this was due primarily to differences in mandibular velocity. Offsetting this difference in mandibular velocity was a tendency for the children to move their lower lips somewhat faster than the adults. Two issues raised in the pilot study concerning possible developmental differences between adults' and children's productions were investigated more closely in the present study, but no such differences were observed in this larger set of data. [Work supported by NINCDS.]
Scattering off rough boundaries in ray and normal mode theory with applications to ocean acoustic tomography and shallow water acoustics
Authors: Lynch James F. , Frisk George V. , Miller James H.
Published: October 2005

Two quantities which can be important, both in acoustic tomography and in shallow water acoustics, are the spread and wander in time of received acoustic pulses due to boundary scattering. These effects limit the pulse travel time resolution one may achieve and then ultimately the resolution of features in the water column (tomography) or ocean bottom (shallow water acoustics). In order to calculate these effects, a breakup of the scattering into adiabatic (leading to pulse wander) and coupled (leading to pulse spreading) ray and mode components was made, and moments of the deterministic propagation results were generated. Applications of this work to coherent array processing and further extensions of this work will be discussed. [Work supported by ONR.]
Parabolic equation modeling of bathymetry: Sensitivity to bathymetric irregularity and rough bottom scattering
Authors: Nghiem-Phu Lan , Tappert Fred
Published: October 2005

The split-step Fourier parabolic wave equation model has been used to study the effects of bathymetric irregularity on transmission loss (TL) for CW acoustic sources. In particular, we have examined the variability in predicted TL curves when bathymetry is imperfectly known. Conversely, requirements on the accuracy of bathymetric measurements in order to reliably predict TL have been obtained. Realistic bottom profiles for the Straits of Florida and for the Great Meteor sea mount have been used. TL curves have been computed for various stochastic realizations of random perturbations superimposed on the deterministic bathymetric profile, and statistical analyses of the results have been made.
Scattering from a rough bottom in the presence of a mean velocity profile
Authors: Beran Mark J. , McCoy John J.
Published: October 2005

We present here an approximate method for calculating the intensity fluctuations resulting from scattering from a rough bottom when the medium has a mean speed of sound profile in the depth direction. The method is an extension of the procedure used to calculate coherence loss under similar conditions and may also be used to calculate the fluctuations in coherence.
Narrow-band low-frequency bottom backscattering strength measurements with an omnidirectional source and directional receiver
Authors: Marandino Davide , Goldsberry T. G.
Published: October 2005

Bottom backscattering strength versus grazing angle was measured in a deep water abyssal plain in the Mediterranean Sea. The measurements were made with a narrow-band 365-Hz-omnidirectional towed source and a towed linear array. The measuring method takes advantage of the receiving array beamforming capability to accurately discriminate returns at given grazing angles from other interfering returns. The approximations to the evaluation of the backscattering areas are analyzed and discussed. The results indicate that for high to medium grazing angles a specular (facet) reflection model is appropriate whereas for medium to small grazing angles the data follow approximately a Lambert's law relationship. The crossover angle depends on signal type and geometries specific to the experiment. The measured data are compared to previously reported measurements.
Acoustic scatter from a slightly rough solid elastic surface
Authors: Tolstoy I.
Published: October 2005

Smoothed boundary conditions can be used to describe the scatter of acoustic waves in a liquid, incident upon the rough surface of an elastic solid, in the limit ka≃kh ≲ 1, k,a,h being, respectively, the wavenumber, roughness element height, and spacing. This is feasible in a theory of O(ka) because (1) stress-induced changes in shape of a compact scatterer yield terms O(k3a2) at most [M. J. Lighthill, Waves in Fluids (Cambridge U.P., Cambridge, England, 1978)] and (2) as in the case of fluid-fluid interfaces the use of constraint conditions [I. Tolstoy, J. Acoust. Soc. Am. 75, 1–22 (1984)] applied to solid compact scatterers of any shape effectively attached them to the solid surface; this allows use of an image principle and representation of the acoustic scatter as a superposition of monopole and dipole sources. Of interest are: (a) A fluid half-space of sound velocity c1 overlying a solid elastic half-space of shear wave velocity cs⩾c1; in this model pure boundary-roughness surface waves coexist with the classic smooth-wall Stoneley (Scholte) mode. The former are less strongly attenuated by energy, losses into incoherent (diffuse) scatter and dominate in the farfield. (b) A thin elastic plate with a rough undersurface overlying a compressible fluid, for which a similar attenuation mechanism substantially attenuates the flexural surface model. [Work supported by ONR.]
Thermoacoustic radiation of underwater sound by a moving high-power laser pulse
Authors: Berthelot Yves H. , Busch-Vishniac Ilene J.
Published: October 2005

Directive sound beams can be generated by modulating the intensity of a laser beam illuminating an optically absorbing medium, usually water. The thermal mechanism inducing the acoustic wave can be optimized by moving the laser beam through the water at velocities close to transonic. However, most theories are not valid at transonic source velocity or for nearfield radiation. These limitations can be removed by using a time domain analysis based on the impulse response of the thermoacoustic array. Although this approach requires the use of a computer, it is also suitable for the complicated (but promising) case of a source moving at nonconstant velocity along a curved path. Experimental results have been obtained with a 1-ms laser pulse at two optical wavelengths (ruby and Nd: Glass) inducing a long and a short array. A rotating mirror achieved source velocities up to Mach 2. Experimental results include pressure waveforms, directivity patterns in the vertical, and horizontal planes of the source, and the sound level dependence on range and Mach number. [Work supported by ONR.]
Ultrasonic generation by pulsed UV lasers
Authors: Hutchins D. A.
Published: October 2005

A Q-switched, frequency doubled ruby laser has been used to generate ultrasonic transients in both metals and water. The laser source delivered multimode pulses, of 30-ns duration and energy ⩽200 mJ, at a wavelength of 347 nm in the UV. Displacements generated in metal plates were detected by wideband capacitance transducers, and compared to wave propagation theory. Thermoelastic, ablative, and modified surface sources were examined, and a good correlation between experiment and theory obtained. In addition, wideband directivity patterns in aluminum were obtained for the thermoelastic source. Thermal generation in water with a cylindrical geometry was also examined, and the expected dipolar pressure transients recorded. It was shown that their duration was a function of the multimode laser beam diameter over the 1.5- to 4-mm range.
Electronic cancellation of acoustic feedback to increase hearing-aid stability
Authors: Weaver Kim A. , Egolf David P.
Published: October 2005

The acoustic feedback which causes a hearing aid to become unstable at high gains is effectively reduced by the addition of negative electrical feedback. Electrical feedback is formed by a system estimator which closely matches the open-loop transfer function of an in situ hearing aid. The system estimator is produced by correlating the estimator signal with the hearing-aid signal. Because the estimator does not affect the characteristics of the hearing aid, speech intelligibility is not degraded by this feedback suppression circuit as it is by most other schemes. Thus 10 to 15 dB of additional stable gain have been achieved through the use of stabilizing negative electrical feedback.
Toward improving speech intelligibility
Authors: Bunnell H. Timothy , Martin James G.
Published: October 2005

One difference observed between conversational and clear speech appears to be the presence of greater amounts of vowel reduction and target formant frequency “undershoot” in conversational speech. Thus vowel formant frequencies in clear speech more closely reach targetlike values, and transitions out of semivowels are steeper in slope [Picheny and Durlach (1979)]. To begin examining the contribution of such effects to the overall improvement in intelligibility of clear speech, an algorithm has been developed which, approximately, inverts the effects of reduction and undershoot in conversational speech. The algorithm is applied to the parameters used by an LPC vocoder program so that, in three steps, synthesis parameters are obtained via LPC analysis, changes in the time course of each synthesis parameter are magnified, and a synthetic utterance is generated which contains enhanced time-changing information. Thus the algorithm operates on spectral change in the original version of an utterance, and magnifies these effects in the new version. Analyses of speech stimuli computed from LPC parameters before and after application of the algorithm reveal differences in formant frequencies and transition slopes similar to those observed between conversational and clear speech. Perception studies to date have compared stop-consonant identification in trisyllabic utterances passed through the vocoder with and without the change algorithm. The results were lower error rates for the change enhanced version.
Acoustic distinctions between intelligible and unintelligible vowels in the speech of the deaf
Authors: Osberger Mary J. , Neely Stephen T.
Published: October 2005

The purpose of this study was to determine if systematic differences in F1,F2, and duration distinguished intelligible and unintelligible vowels in the speech of the deaf. Five deaf speakers produced 35 tokens of selected vowels in CVC monosyllabic words. The intelligibility of the vowel was rated on a 1–5 scale by three listeners familiar with the speech of the deaf. Differences between the deaf speakers and a control group of speakers with normal hearing were noted in mean formant values and token-to-token variability in F1 and F2. These differences were present even in the most intelligible samples produced by the deaf subjects. In general, relatively large differences in F1 and F2 were present for intelligible and unintelligible productions in the speech of the deaf talkers. Further, token-to-token variability in F1 and F2 was greater for the unintelligible than the intelligible productions. There was, however, some overlap of the distribution of intelligible and unintelligible tokens, suggesting that other acoustic dimensions in addition to formant values contributed to perceived intelligibility. No obvious relationship between duration and intelligibility was noted. [Work supported in part by the Easter Seal Research Foundation.]
Relationships between vocal quality estimates and selected acoustic/physiological variables in normally hearing and hearing-impaired persons
Authors: Metz Dale E. , Whitehead Robert L. , Baer Thomas , McGarr Nancy S.
Published: October 2005

The relationship between direct magnitude estimates (DME) of voice quality and ten acoustic and physiologic parameters associated with sustained vowel productions of two normally hearing and four hearing-impaired persons were explored by collecting simultaneous high quality audio and high-speed laryngeal film data. Analysis of the data provided the following variables associated with each subject's vowel productions: (1) harmonic-to-noise ratio (H/N), (2) frequency perturbation quotient (FPQ), (3) amplitude perturbation quotient (APQ), (4) pitch period (T), (5) open quotient (OQ), (6) speed quotient (SQ), (7) mean vocal-fold velocity during glottal closing, (8) mean vocal-fold velocity during glottal opening, (9) mean maximum glottal area during the open phase, and (10) mean glottal area during the closed phase. DMEs of each subject's voice quality were obtained from an experienced judge. Multiple regression analysis revealed that only the FPQ variable significantly predicted the DMEs of voice quality [R = 0.82; R2 = 0.67; F(1,4) = 7.99; p = 0.04]. Correlational analysis revealed that FPQ demonstrated a strong inverse relationship to SQ (r = −0.90) and OQ (r = −0.89). These and other relationships will be discussed in detail. [Work supported by US Department of Education and NINCDS.]
Measurement of speech feature perception in subjects with limited hearing
Authors: Boothroyd Arthur
Published: October 2005

Many profoundly deaf subjects, aided by hearing aids or cochlear implants, are unable to recognize words or comprehend sentences by hearing alone but can perceive some phonologically significant contrasts, and thereby lipread more effectively. Measurement of this limited auditory ability typically requires the use of forced-choice tests with their attendant problems of low efficiency, and the possibility of responses to cues that do not remain invariant across phonetic context. This paper describes a Speech Pattern Contrast (SPAC) test that measures the perception of four suprasegmental and eight segmental contrasts in a changing phonetic context. To improve efficiency, the binary contrasts are tested in pairs, and the test has been automated using a computer-controlled, interactive system that also provides the option of feedback and replay. Evaluation of the SPAC test with hearing-impaired subjects has shown only small, task-dependent, learning effects. The interleaving of two-binary choice tests does, however, produce a decrement of performance. Normally hearing subjects listening only to fundamental frequency (F0) pass all the suprasegmental subtests and the final consonant voicing subtest. The performance of one subject, recently fitted with a cochlear implant that transmits F0, was almost identical to that of the normal subjects listening to F0. [Work supported by NIHR grant G008302511.]
Low bit rate real-time half duplex LPC vocoder utilizing minimal random access memory
Authors: Moore Morris , Keba James M.
Published: October 2005

A low bit rate real-time half duplex LPC vocoder was constructed based upon the Texas Instruments TMS32010 digital signal processor IC. Approximately 2700 words of external ROM were used for program and tables. The 144 words of onboard RAM were the only words of RAM used. The analysis was performed on preemphasized windowed speech using autocorrelation accumulation and the LeRoux-Gueguen method to generate reflection coefficients and gain. A modified Rabiner-Gold pitch algorithm was used for pitch and voicing. The software was split into foreground computations done on each speech sample and background computations done on each frame. There were 54 LPC information bits generated per frame.
The relationship between intelligibility and naturalness in high quality synthetic speech
Authors: Carrell Thomas D.
Published: October 2005

The relationship between intelligibility and naturalness in synthetic speech was examined. There has been evidence that in extreme cases very unnatural speech may be intelligible [R. E. Remez et al., Science 212, 947–950 (1981)] and very natural sounding speech may be unintelligible [E. Abberton and A. J. Fourcin, Lang. Speech 21, 305–318 (1978)]. However, there is little evidence regarding the independence of naturalness and intelligibility in relatively high quality synthetic speech. This relationship was investigated in the present experiment using a paired-rating design, in which listeners were required to rate the intelligibility and naturalness of a pair of words on each trial. The first item was always a digitized natural token of a word and the second item was always a synthetic version of the same word. The synthetic stimuli were designed to mimic the specific acoustic correlates of three male and three female talkers. Overall, the listeners rated the synthetic speech as highly intelligible and natural. In addition, a principal component analysis indicated that the naturalness and intelligibility of the different synthetic talkers were independent factors. These results argue that even in the case of high quality synthetic speech, these two attributes of the signal are separate. [Work supported by NIH (NINCDS).]
The intelligiblity of nonvocoded and vocoded semantically anomalous sentences
Authors: Mack Molly , Gold Bernard
Published: October 2005

This study consisted of an analysis of the intelligibility of semantically anomalous sentences presented to 28 subjects in four conditions (seven subjects per condition): (1) natural speech, no noise; (2) vocoded speech, no noise; (3) vocoded speech, noise added to the pitch track; (4) vocoded speech, noise added to the spectrum. Results revealed that intelligibility was quite good in conditions (1) and (2), relatively poor in (3), and quite poor in (4)—results consistent with previously obtained Diagnostic Rhyme Test (DRT) data [B. Gold and J. Tierney, Lincoln Laboratory Tech. Rep. No. 670 (1983)]. Specifically, subjects averaged 10, 25, 47, and 141 errors each in conditions (1), (2), (3), and (4), respectively. Further, about 60% of all errors were phonemic, while 40% were syntactic and semantic. We concluded that information in the spectrum is more critical than information in the pitch track, that most errors affect the phonological component when intelligibility is poor and context is uncertain, and that the DRT is an appropriate though perhaps insufficient test of speech intelligibility. [Work sponsored by the Department of the Air Force.]
Multipulse linear predictive synthesis in text-to-speech systems
Authors: Varga Andrew , Fallside Frank
Published: October 2005

Multipulse linear prediction is a coding technique that can provide extremely high quality speech synthesis [B. S. Atal and J. R. Remde, IEEE Proc. ICASSP82, 614–617 (1982)]. It is therefore of interest to examine whether the technique can be used to provide correspondingly good quality in a text-to-speech system. In such a system a prosodic contour is imposed on a set of concentrated speech units. Various speech units (e.g., words and diphones) have been tried. First results suggest that the word is the appropriate unit to be used in such a system. The techniques for pitch and timing alteration, speech unit concatention, and the effects on the resulting synthetic speech will be discussed and demonstrated.
A versatile dictionary for speech synthesis by rule
Authors: Hertz Susan R.
Published: October 2005

All synthesis rule developers are faced with the problem of handling phenomena that cannot easily be captured in rules. The Delta System [J. Acoust. Soc. Am. Suppl. 1 75, S60 (1984)] provides the rule writer with an especially versatile exception dictionary. The dictionary has two parts: the active dictionary and sets. The active dictionary can store token sequences representing units of any kind (e.g., phrases, words, demisyllables) and associate arbitrary actions with them. For example, an action might specify a pronunciation, as in conventional dictionaries, or it might invoke a rule. An action can be restricted to the portion of an entry that is an exception. Sets contain token sequences but no actions. They provide an especially compact way to group together items that behave similarly. Rules can test a token sequence for membership in a set to determine whether to apply to the sequence. Delta's dictionary is fully integrated into the rule system it accompanies. It can set variables for the rule program, influence the program's flow of control, and manipulate the utterance being synthesized.
Network representation of templates in word recognition
Authors: Lee Kai-Fu
Published: October 2005

Reference set generation is a crucial step in template-based isolated word recognition. Some common techniques include casual training, selection, clustering, and averaging. These single-template systems do not capture the variations in speech. Alternatively, multiple-template techniques lead to additional storage and recognition time. Network representation combines the performance of multiple-template techniques and the efficiency of single-template techniques. Using the network approach, words are divided into segments, and different examples of the same or different words can share segments. This not only reduces storage required, but also enables the system to focus on acoustically dissimilar segments. Network representation has not been popular because of the difficulties in (1) segmenting correctly and recovering from segmentation errors, and (2) creating and modifying the network automatically. A word recognition system has been designed and implemented to facilitate network training by providing (1) relatively reliable segmentation, (2) segment-based warping algorithm that tolerates inexact segmentation, and (3) incremental network generation. Preliminary results show that network training is superior to all of the above-mentioned methods for speaker-dependent and independent recognition. [Work supported by NSF.]
Computation of normal modes for the seismo-acoustic problem
Authors: Porter Michael B. , Reiss Edward L.
Published: October 2005

In a recent paper the authors presented a fast and accurate method for computing the normal modes in a stratified ocean with a perfectly rigid bottom [M. Porter and E. L. Reiss, J. Acoust. Soc. Am. 76, 244–252 (1984)]. We describe the extensions which allow for the computation of modes in an ocean overlying a subbottom with depth-dependent P- and S-wave velocities. The effect of the ocean sub-bottom is incorporated by replacing the rigid bottom boundary condition by a numerically computed impedance condition which is a function of frequency, horizontal wavenumber, and the material properties of the ocean sub-bottom. We illustrate the method by computing the modes for an ocean with a Munk sound speed profile overlying an ocean sub-bottom with linearly increasing P- and S-wave velocities and terminated by a rigid basement. [Work supported by NSF and ONR.]
Propagation loss measurements in a region of complex bathymetry over the continental slope
Authors: Syck J. , Chapman R.
Published: October 2005

Measurements of propagation loss over a sloping bottom have been obtained in experiments on the continental slope off the west coast of Vancouver Island. Shot runs were carried out to ranges of 100 km using 18 m and 180 m SUS charges in upslope and downslope geometries. The data were processed in 1/3-oct bands from 12.5–630 Hz. The 18-m shots were bottom-limited in these experiments, and the effect of the interaction with the seafloor was observed for these charges in both experimental geometries. An enhancement in the propagation loss was observed for the downslope run, with the loss decreasing by up to 10 dB for shots at the crest of the slope, whereas the loss increased with range faster than cylindrical spreading for the upslope run. Also, an optimum frequency of propagation was observed at 50 Hz for both geometries. In contrast, the propagation loss increased with both range and frequency for the deeper shots. The measurements have been modeled using a wide-angle parabolic equation method which is capable of accounting for the interaction with the sloping bottom. The modeled results provide an accurate description of the features observed in the measurements.
Shallow water propagation with variable depth
Authors: Dixon Daniel N. , Mitchell Stephen K.
Published: October 2005

This paper presents calculations of acoustic propagation in a shallow depth-varying ocean environment using both the simple adiabatic and the uniformly valid adiabatic (UVA) normal mode theory of Desaubies [J. Acoust. Soc. Am. 76, 624–626 (1984)]. In the UVA approximation, modal coupling effects are accounted for through a second order correction term in the phase of the sound field; only the phase relationships between the modes are affected, and the modal amplitudes remain unchanged. Consequently, the approximation is adiabatic in that no energy is exchanged between modes. This expansion technique, which Desaubies applied to a range-varying sound speed profile, is generalized here to the variable depth waveguide problem. In the shallow water example considered, it was found that the phasing effects can significantly change the interference patterns of propagation loss curves. In general, the phase changes are found to become more significant with greater bottom slopes and higher frequencies. Comparisons of calculations and data are presented. [This work was supported by the ARL:UT IR&D Program.]
Piezoelectric transducers for electronic telephone sets
Authors: Ichinose Yutaka , Tobita Mizuhiro
Published: October 2005

Three kinds of piezoelectric transducers, a transmitter, a receiver, and a tone ringer sounder, have been developed for electronic telephone sets. The transducer's diameter is 33.3 mm and is less than 6.3 mm thick. Compared with other types of transducers used in conventional telephone sets, the volume of the new transducers is reduced to about 1/10 and the number of parts is reduced to about 1/2. Although each transducer requires a different frequency response, each uses the same bimorph diaphragm, constructed of a piezoelectric ceramic plate and a brass plate. This bimorph diaphragm converts acoustic power into electric power and vice versa. To design transducers, it is necessary to obtain diaphragm constants such as fundamental resonance frequency, effective mass, effective stiffness, and effective area. Approximate values for these constants are calculated without using Bessel functions (essential in the calculation of exact values). The optimum dimensions of the diaphragm found to maximize sensitivities of the transducers are: a diameter ratio of the ceramic plate to the brass plate, of about 0.8 and a thickness ratio of about 1.0. At 1 kHz, the sensitivities of the transmitter, receiver, and sounder are −54 dB (0 dB:IV/Pa), 44 dB (0 dB:1 Pa/W), and 5 dB (0 dB:1 Pa/W at 0.5 m), respectively.
A PVDF touch sensor for robotics
Authors: Chang Mark , Busch-Vishniac Ilene
Published: October 2005

Because of the flexibility of PVDF piezoelectric material, it is an attractive material for use in constructing a robotics touch sensor. Although PVDF sensor arrays have been discussed in the literature, little attention has been paid to the possibility of using a single PVDF sensor for determining the force of contact between the sensor and a smaller surface. This research examines the possibility of a single PVDF sensor of circular geometry by using a normal mode expansion to predict the film displacement as a function of location when a force is applied over a selected urea of the transducer. The sensor output voltage is obtained from the piezoelectric constitutive relations which relate the strain and electric field. Laboratory measurements were used to obtain the damping coefficient as a function of frequency. Measurements of film displacement and predictions are in good agreement. Attempts are currently under way to outfit an IBM 7510 RS1 robot with this touch sensor.
Mathematical model for a free-flooded piezoelectric cylinder transducer
Authors: Rogers Peter H.
Published: October 2005

A mathematical model for the transmitting response of a free-flooded, thickness-polarized piezoelectric cylinder transducer has been developed. The elasticity of the cylinder is described using thin shell equations which have been modified to account for piezoelectric effects. An additional consequence of the piezoelectricity of the shell is a significant alteration in the boundary conditions for the ends of the cylinder. A particular solution to the thin shell equations which satisfies these modified boundary conditions is obtained. The complete solution for the vibration of the cylinder is then found in the form of a sum of the particular solution and the normal modes appropriate to a nonpiezoelectric cylinder with free ends. The acoustic field loads the solution, couples the normal modes, further couples the particular solution and the normal modes, and changes the boundary conditions. The acoustic influence coefficients needed to incorporate these effects are calculated using the SHIP computer program (a fast Helmholtz integral radiation program). The water-loaded normal surface velocities are determined and the surface pressures and farfield radiation characteristics are calculated using SHIP. The model fully accounts for such effects as the cavity resonance, the velocity of the ends of the cylinder, distribution of velocity along the length of the cylinder, and the difference between the velocity on the inner and outer surfaces of the cylinder. Comparisons between theoretical and experimental results are presented.
An analysis of the loss of sensitivity in porous ceramic hydrophones
Authors: Rittenmyer K. M. , Ting R. Y.
Published: October 2005

Porous ceramics of the PZT type have been found to exhibit very high values of piezoelectric g constant when compared with the conventional PZT. The material also showed no hysteresis effect upon pressure cycling. These features suggested that porous ceramics may be potentially useful for hydrophone applications. Early prototypes of high-frequency hydrophone designs containing porous PZT elements were found to have a constant free-field voltage sensitivity (FFVS) up to about 100 kHz. Above this frequency, however, a sharp decrease in the FFVS was observed. Since variations in the hydrophone design did not improve the high-frequency response of the hydrophones, the loss in FFVS was attributed to the material itself. A theoretical model was developed to analyze this loss phenomenon in porous ceramic hydrophones. The effect of the porosity was found to reduce the frequency constant NR of the piezoelectric ceramic. The frequency dependence of the strain produced in the porous ceramic by a longitudinal wave was further determined. The general feature of the strain-versus-frequency calculation agreed very well with the measured FFVS-versus-frequency relation. Since the voltage generated is proportional to the strain in the piezoelectric element, this result is used to explain the observed loss in the FFVS of porous ceramic hydrophones. [This work was supported by the ONR Acoustic Transduction Metrology Program.]
A ρc hydrophone
Authors: Moffett Mark B. , Powers James M. , McGrath John C.
Published: October 2005

Traditional piezoelectric materials have much higher impedances than water, and so most hydrophones are hard compared to the surrounding water medium. This “hardness” is the cause of internal and external reflections which manifest themselves as resonance and diffraction factor effects, respectively. Even nonvoided polyvinylidene fluoride (PVDF), a piezoelectric polymer, has a characteristic acoustic impedance (ρc) about 2.5 times that of water. With the advent of voided PVDF, however, it is possible to match water's impedance as closely as desired. Through the use of ρc window material and ρc PVDF, we have constructed a ρc hydrophone whose response is essentially free of resonance and diffraction factor effects. [Work supported by Naval Material Command via NUSC's Independent Exploratory Development program.]
The mechanical and acoustical properties of some optically clear silicone rubbers
Authors: Cuomo Frank W.
Published: October 2005

It has been recently found that the distal end of a bifurcated fiber optic lever hydrophone can be effectively coupled to a reflective surface by means of elastomers. Compounds having suitable optical, acoustical, and mechanical properties for this application are clear silicone rubbers. Among the parameters most useful for transducer evaluation the index of refraction, the compressibility, the sound speed, and the absorption coefficient predominate. In particular, the sound speed and absorption coefficient are obtained from pulse-echo methods in the 500 kHz–2 MHz frequency range. Since the linear behavior of these materials when subject to submicron motion is relevant to the operation of the fiber-optic lever device, a quad diode bridge arrangement for capacitive transducers is used to establish its linear characteristics within the micron displacement range. Utilizing these measurement techniques several optically clear silicone elastomers are evaluated. [Work supported in part by NUSC.]
Quantifying the effects of noise reduction
Authors: Hattis Dale B. , Ashford Nicholas A.
Published: October 2005

Quantifying the benefits of noise reduction presents complex methodological difficulties. Appropriate measures of hearing loss at equilibrium as well as adjustment periods need to be expressed in appropriate terms. Nonaudiometric effects of noise exposure, though difficult to quantify, must not be ignored. The effect of worker mobility must be accounted for explicitly. The presentation of the benefits of noise reduction in juxtaposition to the costs must occur in ways which reflect a realistic appreciation of the health problem for which policy alternatives can be designed.
Short- and long-term benefits of noise control programs
Authors: O'Keefe Jack V.
Published: October 2005

Immediate or short-term benefits of industrial noise control and reduction are coupled to estimates of potential technical accomplishments within the current state-of-the-art. Source noise control and reduction within these guidelines are generally small versus the projected gross cost. Manufacturing methods or material processing techniques or machinery which perhaps already demanded de-facto change frequently are the bandwagon auxiliaries that may be included in total cash outflow attributed to industrial noise abatement programs. Long-range benefits are coupled with the basic research and applied research to exploit noise source control advances and furthering the SOA to improve methodology and materials. Some government funding for advancing and implementing this SOA may be required. Rewards for accomplishing these tasks are to decrease and eventually eliminate hearing damage risk, hearing damage per se, hearing effects claims, hearing compensation payments, physiological effects, and to improve work-force morale, overall efficiency, and productivity. Quantification of the effects of administrative and engineering controls, technical feasibility limits for some major noise source problems and total integrated costs balanced with short- and long-range corporate cost estimates will be covered. Estimates of efficiency/productivity versus noise reduction will be presented.
Industrial noise, the future
Authors: Stewart Noral D.
Published: October 2005

Past emphasis in industrial noise in the United States has been on reducing the noise of existing machines and plants. This was a direct result of OSHA regulations requiring feasible controls. Much has been accomplished even though the regulations left questions as to what was feasible. The new emphasis on the purchase of more productive machinery and construction of new plants requires that more attention be shifted to the development of quiet new machines and consideration of noise in new plant layout. It is often not feasible to later implement controls which could have been incorporated in new machine or plant designs. Failure to give proper attention to noise of new plants and machines during a period of economic growth will greatly delay the eventual quieting of the workplace. Outside of a few leading companies which have recognized the benefits of noise reduction and active noise control programs, there appears to be little effort to assure quiet in new construction. Those companies which are attempting to buy quieter machines are encountering difficulty as they “go it alone.” This paper will discuss the reasons why more is not being accomplished and actions which could be taken by manufacturers, machine builders, industry organizations, and government to make greater progress possible.
Occupational noise regulations. How good can they be?
Authors: Benwell Deirdre A.
Published: October 2005

Ideally, occupational noise regulations would provide all workers with protection from any measurable degradation of hearing acuity. Practically speaking, most present occupational noise regulations are set at levels that primarily protect hearing in the speech frequency range. Consequently, if the regulation is enforced, workers are prevented from becoming so deaf that they are a burden to society. This is true whether the limit is 90 or 85 dBA and whether 3- or 5-dB time trading relations are used. There has been much discussion over the appropriate limits to set in occupational noise regulations. However a close examination of the facts on which these limits are based makes the actual limit seem less important. This paper examines these facts which include:—the scatter in the internationally accepted data base and its effect on the accuracy of the 0-dB hearing level; the large apparent variation in individuals susceptibility; the difficulty in assessing the effects of sociocusis; the accuracy of the audiometric test (test conditions and the test itself); and the question of how best to measure occupational noise levels. The need for continuing research to develop better methods of hearing measurement and the development of new data bases relating noise exposure, age, and hearing loss, is elaborated. It is concluded that limits must be set and enforced, and workers educated, to reduce occupational noise-induced hearing loss.
Is occupational noise exposure during pregnancy a risk factor for the inner ear damage of the fetus?
Authors: Lalande Nicole M. , Hétu Raymond
Published: October 2005

In Quebec, the occupational health and safety administration has adopted regulations for the pregnant woman. For noise exposure, the permissible limit is 90 dBA-8 h. In our opinion, such an exposure could have an adverse effect on the hearing of the unborn baby, especially in cases of low-frequency noise. An epidemiological study was undertaken to verify this possibility. Pure tone thresholds were obtained from 167 children (4–10 years of age) whose mothers had worked during pregnancy in various noise conditions (65–95 dBA-8 h). The effect of noise exposure during pregnancy was tested on 131 children who had no history of sensorineural or mixed hearing loss, no exposure to firearm noises, and no middle ear problem at the time of the test. Results show a threefold increase in the risk of high-frequency loss when the long term daily exposure (LAeq, 9 m) ranged between 85 and 95 dB.
Predicting auditory and nonauditory system effects of noise
Authors: Kryter Karl D.
Published: October 2005

Analyses of some recent and older data on damage to auditory and nonauditory systems of the body indicate that some noise measurement and impact assessment procedures promulgated by governmental agencies and technical standards organizations should be modified. Specifically, factors not adequately (state-of-the-art) considered in existing noise exposure guidelines are: (a) the biasing contributions of sociocusis and nosocusis to the interpretation of hearing loss from low-level noise exposures; (b) the effects of climate and type of noise source on the effective dosage received indoors from noise from transportation vehicles; (c) relative weights for day-evening-night time exposures; (d) nonauditory system health disorders as a function of environmental noise exposure level. Modified procedures for quantifying noise exposures and their relation to auditory and nonauditory health disorders and existing standards and guidelines will be presented. Some scientific problems involved in ascribing auditory and nonauditory health disorders to noise will also be discussed.
How do we arrive at noise standards?
Authors: Eldred Kenneth McK.
Published: October 2005

This paper describes the principal organizations responsible for the development of noise standards, discusses processes through which they are generated, and identifies the principal types of standards that exist. The majority of standards are developed voluntarily by the private sector, both in the USA and abroad. The American National Standards Institute (ANSI) coordinates American federated national standards system which in acoustics includes professional societies such as ASA, SAE, and ASTM and industry organizations such as NEMA, CAGI, and OPEI. ANSI also is the U.S. member of the organizations responsible for developing voluntary international standards. Participation in the development of ANSI and international standards in acoustics is open to all who have a direct and material interest. Voluntary standards cover all aspects of acoustics, including measurement, instrumentation, propagation, noise control devices, and human response criteria. In the USA, government standards or regulations are promulgated by all levels of government, federal, state, and local. Participation in their development is determined by the rules appropriate to the promulgation entity. Other countries also promulgate regulations in which opportunities for comment by individual interested persons are usually announced in the USA. Government standards and regulations cover many major sources of noise such as transportation vehicles, and various environments such as noise in the community and in the workplace.