bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of ray theory to downwind propagation of low-frequency noise in the atmosphere
Authors: Hawkins James A. , Blackstock David T.
Published: October 2005

Willshire [J. Acoust. Soc. Am. Suppl. 1 77, S91–S92 (1985)] and NASA Tech. Mem. 86409 (April 1985) have reported measurements of downwind propagation for very low-frequency noise from a large wind turbine generator. The source height was 40 m, and ground measurements were taken out to 10 000 m. The noise was found to spread spherically near the source (out to 450 m) but cylindrically thereafter. We present ray theory calculations of the propagation loss for this experiment. Our computer program is adapted to the atmosphere from MEDUSA, a ray theory program developed for underwater sound [T. L. Foreman, Tech. Rep. ARL-TR-83-41, Applied Research Laboratories, The University of Texas at Austin, 1983, ADA-137202]. We assume a realistic ground impedance to calculate reflections at the ground and a logarithmic wind velocity profile to account for sound-speed variation. Results for 8 Hz show that channeling caused by downwind refraction is responsible for the cylindrical spreading observed downrange of the source. Near the source, spherical spreading occurs because channeling has not yet been established. The results are in quantitative agreement with Wilshire's data. [Work supported by NASA.]
Field experience in measuring and evaluating acoustical parameters for motion picture theatre environments
Authors: Cavanaugh William J. , Batton Phil D.
Published: October 2005

Since early 1983, the General Cinema Corporation has been engaged in a major expansion and renovation program of its movie theatre complexes throughout the United States. Furthermore, recent developments in motion picture presentation technology involving films with extended dynamic and frequency ranges have led to reconsideration of and, in some cases, adaptation of conventional criteria for evaluating the acceptability of theatres for viewing and listening to films. The results of field measurements (octave-band reverberation times, room-to-room NR'S, and background sound-pressure levels) are reported for a large number of facilities including data for the often disregarded 31.5-, 63-, and 8K-Hz bands. The considerations in obtaining adequate field data and in developing criteria, as well as practical cost effective acoustical control measures developed for new generation theatres, are reviewed.
Noise control of banking business equipment
Authors: Ying S. P.
Published: October 2005

Noise control of three kinds of business equipment, namely, document printer, currency dispenser, and endorser/encoder, was investigated. These machines which use microprocessors as the control devices were developed recently for use in banking. During the development or improvement stage, an acoustic improvement program for each kind of equipment was initiated with sound power level determination, followed by noise diagnostic tests using the coherence function technique. One of the common noise sources in the equipment was the broadband printing noise which was radiated directly from the printing head and through machine structures. The currency dispenser had gear noise which resonated with the machine structure at the gear mesh frequency. Recommendations for noise reduction included utilization of sound absorption foam inside cabinets, increase of sound transmission loss of machine cases, sound isolation for structure-borne noise, and treatments of openings. Test results of some of these improvements are presented.
Low-frequency noise in jet engine test facilities
Authors: Boe Rollin O. , Boe Mark S.
Published: October 2005

Jet aircraft and engine test facilities are being designed to operate using air cooling only in the exhaust system. Many of these facilities are experiencing low-frequency noise due to aerodynamic instability. The presentation will include a discussion of low-frequency noise generation in jet engine test facilities and measured data. Data are measured down to 2 Hz since much of the noise energy is in the infrasonic frequency range.
Binaural detection and discrimination: Impaired listeners
Authors: Koehnke Janet , Colburn H. Steven
Published: October 2005

The experimental tasks, techniques, and stimuli for this study are the same as those described for normal listeners (see preceding abstract), except for the choice of levels at each ear. A set of reference interaural intensity differences (IID's) were chosen based on IID's corresponding to equal SPL, equal sensation level (20 dB SL), equal loudness (ABLB measurements), and a centered perception. Performance in the four binaural tasks was measured at reference interaural conditions that include all combination of these IID's and interaural time difference of −300, 0 and +300 μs. Subjects in these experiments have varying degrees and configurations of hearing loss, and thus far binaural performance shows no clear relation to these audiometric measures. Data from illustrative subjects are discussed in terms of the dependence of performance on the reference interaural condition and in terms of the ability to predict results in one task from performance in the other tasks. The consistency of performance and predictions for the relation between NoSπ detection and interaural correlation discrimination is observed in the impaired listeners as well as in the normal listeners. [Work supported by NIH.]
Detectability of tonal signals with changing interaural phase differences in the presence of diotic or interaurally uncorrelated noise
Authors: Grantham D. Wesley
Published: October 2005

Detectability of binaurally presented 400- and 800-Hz tonal signals was investigated in an adaptive, two-interval, forced-choice experiment. A continuous 3150-Hz low-pass noise masker was employed, which was presented either diotically (No) or interaurally uncorrelated (NU) at an overall level of 70 dB SPL. Signal duration was either 100 or 1000 ms. In part 1 of the experiment thresholds were determined for several values of signal interaural phase difference between 0° (So) and 180° (Sπ) [e.g., Jeffress, Blodgett, and Deatherage, J. Acoust. Soc. Am. 24, 523–527 (1952)]. In part 2 the interaural phase difference varied dynamically during the signal presentation (slightly different frequencies were presented to the two ears). The range of interaural phase variations was selected to yield the same varying interaural temporal differences that would be produced if real auditory targets traversed various arcs in the horizontal plane. The data will be discussed in terms of previous data related to dynamic binaural processing, with particular regard to the potential effect of an auditory object's movement on its detectability. [Supported by NIH.]
What are fish listening to?—A possible answer
Authors: Rogers Peter H.
Published: October 2005

Although all fish hear, relatively few species are known to vocalize. The biological relevance of hearing in fish is thus somewhat of an enigma. In this paper, we suggest that what fish may be listening to is ambient noise scattered from the swim bladders of nearby fish. This is in some ways analogous to the role of the visual system in most animals, where the relevant stimulus is ambient light scattered by objects rather than light emitted by luminous objects. Although the scattered noise signal is much weaker than the unscattered ambient noise signal, it was demonstrated that a relatively simple processing scheme could greatly enchance the S/N and enable a fish to detect and unambiguously localize a nearby fish from the scattered noise. The processing scheme, which relies on the nearfield properties of the scattered signal, is shown to be consistent with the known capabilities of the fish auditory system and may well explain many of them. [Work supported by ONR Code 420.]
The effect of four types of filtering on the intelligibility and quality of speech-in-noise for hearing-impaired listeners
Authors: Neuman Arlene C. , Schwander Teresa
Published: October 2005

A common complaint among hearing aid users is of difficulty in using amplification in noisy situations. In this study, subjective judgments of quality and intelligibility of speech-in-noise, as well as speech recognition scores, were obtained from sensorineural listeners through four different filters (1) flat frequency response, (2) a frequency response which places the rms level of the speech at the listener's comfort level, (3) a high-pass filter in combination with filter ♯2, and (4) a filter designed to keep the noise spectrum parallel to the listener's thresholds for one-third octave bands of noise. Preliminary results indicate that for individual listeners the four filters were ranked similarly, whether the criterion used was intelligibility or quality. Speech recognition performance was in agreement with subjective judgments of intelligibility. [Work supported by NIHR Grant No. G008302511.]
On spontaneous speech and fluently spoken text: Production differences and perceptual distinctions
Authors: Remez Robert E. , Rubin Philip E. , Nygaard Lynne C.
Published: October 2005

Our initial study [J. Acoust. Soc. Soc. Am. Suppl. 1 77, S38 (1985)] of spontaneously produced speech and fluently read speech found that these two kinds of utterance were distinguishable by untrained listeners, and may represent different modes of speech production. The perceptual differentiation of these types of utterance, which we tested using well-formed sentences free from gross metrical dysfluencies, seemed not to depend on a single acoustic emblem of spontaneity or reading, neither the presence or absence of pitch downdrift, nor average vocal pitch, nor average duration. The simplest acoustic correlate of perceptual success in identifying instances of spontaneous production, and of misidentifying read speech as spontaneous, was the variance of the phonatory frequency. Our present study again employs a perceptual test of the differences between spontaneous and read speech, using partial sentences. Listeners identified a test set composed either of the initial portions of sentence-size utterances or of the final portions. Partial sentences appear to offer information inferior to complete sentences about this distinction in most cases, though final portions are better sources than initial portions. The results are discussed with reference to speech production. [Research supported by NINCDS and NICHHD.]
Acoustic propagation phenomena in time domain
Authors: Mellen R. H.
Published: October 2005

Despite the intuitive appeal of ray theory, the associated time-domain properties remain largely neglected. Rays retain memory of “catastrophic” encounters along the path. A well-known example is polarity reversal at a pressure-release surface. Similarly, spherical waves resolve into an incoming and an outgoing impulse of reversed polarity, the waveform at the focus being the time derivative. Distortion of explosion waves, caused by refractive focusing, was first observed experimentally 25 years ago. For a cylindrical focus, phases advance π/2 and the outgoing impulse is Hilbert transformed while, on the caustic, the waveform is the Heaviside fractional derivative. Reflection at a fluid-fluid interface, for grazing angles less than critical, can also be expresed by Hilbert pairs δ(t) and −1/πt. For an elastic solid, the transmitted signal resolves into a shear and a compressional impulse. At the critical angle of total reflection, the two impulses merge to become partially evanescent. Comprehensive mathematical methods of treating all such phenomena have only recently begun to appear.
Eigenray calculations in n uniformly stratified mutilayer medium
Authors: Arvelo J. I.
Published: October 2005

This paper presents the equations to be solved in order to calculate the travel time of an eigenray in a uniformly stratified refractive medium. The data required are the sound-speed profile and the relative position of the source and receiver. It has been proved that in a bilinear profile there exists up to three direct path eigenrays which can be calculated in a closed form by solving a cubic equation. However, in an N-layered media, it is not possible to predict the number of direct path eigenrays, nor calculate them, in a closed form. Ray tracing iteratively could be used to calculate these eigenrays. This eigenray method usually takes one to five iterations (less than 3 s) to obtain an accuracy in the horizontal range of one microfoot, and an uncertainty in the travel time of less than one microsecond, in a media of forty layers. Calculations were done on an HP9845B, 16 bit, 8 MHz, with interpretive BASIC language. The method described here is particularly useful in calculating the travel time difference of a system of one source (receiver) and a distribution of receivers (sources). A rapid and accurate travel time calculation is now possible with this method.
Curved surface diffraction theory derived and extended using the method of matched asymptotic expansions
Authors: Pierce Allan D. , Main Geoffrey L. , Kearns James A.
Published: October 2005

Consideration is given to the top of a wide barrier with variable radius of curvature R. The surface has finite acoustic surface impedance Z. Because kR is assumed large, the illuminated region can be approximated by geometric acoustics, such that plane wave reflection rules apply locally. The intricate interference pattern between incident and reflected ray fields assumes a tractable analytical form near the barrier top, which is subsequently used in a MAE solution of the overall diffraction problem. Unambiguous length scales result for radial and tangential distances along the barrier top. The inner solution is developed by expressing the wave equation in terms of such scales, subsequently identifying the expansion parameter as (kR)−1/3. A parabolic equation emerges, with a boundary condition involving a scaled impedance (Z/ρc)(kR)−1/3; the outer boundary condition results from matching to the geometric acoustics solution. Outer expansion of the solution of the parabolic equation into the shadow zone yields an inner boundary condition on the ray theory solution for the diffracted wave. Results are similar to those previously derived for electromagnetic diffraction problems by V. A. Fock, but the MAE interpretation facilitates an extension to problems of multiple barriers. [Work supported by NASA-Langley.]
Relationship between near and farfield effects in second harmonic generation in the piston beam
Authors: Foda M. A. , Ginsberg J. H.
Published: October 2005

An earlier analysis [J. H. Ginsberg, J. Acoust. Soc. Am. 76, 1201–1214 (1984)] of the infinite baffle problem for an axisymmetric harmonic excitation derived a nonlinear King integral describing signal distortion in sound beams. That analysis, which considered only the contribution to the cumulative distortion process associated with secular source terms, agreed with experiments at high frequencies at ranges beyond approximately one quarter the Rayleigh length. However, there was significant discrepancy with measurements very close the transducer face. Such differences will be shown to result from neglecting nonsecular second-order terms that do not carry into the farfield. In the present work, the nonsecular contribution to the second harmonic is evaluated as a numerical inversion of a multiple integral transform for the second-order potential. The composite effects of secular distortion, which is calculated using the renormalized King integral, and the nonsecular contribution are calculated. The results obtained from the analytical model compare favorably with previoius nearfield measurements. [Work supported by ONR, Code 425-UA.]
Computerized Schlieren visualization
Authors: Nagy Peter B. , Adler Laszlo , Greguss Pal
Published: October 2005

In everyday scientific research, the sought information about the acoustical phenomenon under study is often conveyed by the beam profile, or more generally, by the spatial distribution of the acoustic field. In many cases, such as Rayleigh phenomena, diffraction, scattering, leaky surface wave, etc., the acoustic field of interest can be observed conveniently in an optically transparent media by Schlieren visualization. This method readily gives a qualitative picture of the overall phenomenon, but often we need more precise quantitative results. An easy-to-use laser based system which works in cw as well as pulsed operation up to a considerable speed of 15 ns. The real-time video display offers a convenient way of direct evaluation, but the whole picture or part of it can be digitalized and fed into a PDP 11/34 computer. Examples are presented showing how this technique can substitute troublesome hydrophone mapping by mechanical scanning, and how the accuracy and reliability of the result can be increased by such digital signal processing methods as time and/or spatial averaging, image subtracting, smoothening, contouring, etc. In addition, the cross section of axisymmetrical beams can be reconstructed by a simple computerized tomography technique from the measured projection.
The role of discharge history effects in rapid adaptation of auditory-nerve fibers
Authors: Lutkenhoner Bernd , Smith Robert L.
Published: October 2005

PST histograms reflecting the response of auditory-nerve fibers to high-intensity bursts show a high initial peak followed by an exponential decay with a time constant of a few milliseconds (“rapid adaptation”). The role discharge history effects play in this phenomenon is being investigated. It is assumed that the probability for a spike in the infinitesimal interval (t,t + dt) is given by the expression s(t)r1(x1)…rm (xm) dt, where s is the “excitation function,” r, is the ith order recovery function, and xi = xi (t) is the time since the ith prior discharge (i = 1,2,…,m). Higher-order recovery functions have been suggested by Gaumond [Doctoral thesis, Washington University, St. Louis, MO (1980)] who also demonstrated the existence of the second-order function r2. Our experimental investigations confirm his results and furthermore reveal third- and fourth-order effects. Monte Carlo simulations show that the first-order recovery term can explain only the initial peak of the rapid adaptation phenomenon. In contrast, higher-order effects can contribute substantially to the exponential decay. [Work supported by the Deutsche Forschungsgemeinschaft, NSF and NIH.]
A scanning microphone implementation of nearfield acoustical holography
Authors: Strong William Y. , Ebbitt Gordon
Published: October 2005

A system that implements the nearfield acoustical holography (NAH) technique in air has been designed and placed into operation at the CBS Technology Center. The system utilizes a scanning microphone that may be positioned within a 3.7×3.7×1.2 m volume by a computer controlled robot. Sound pressure data from the scanning microphone and a reference are stored in a mini computer and subsequently processed using nearfield holographic techniques. The resulting reconstructions of the pressure, velocity, and vector intensity fields may be displayed using either a 3-D video graphics system or a digital plotter. A detailed discussion of this NAH system will be presented and reconstructions of the sound field generated by a simple source will be shown.
Vibrational characteristics of an infinite flat plate with varying properties
Authors: Pierucci Mauro , Le Tuan
Published: October 2005

A theory to study the vibrational characteristics of a structure with properties varying along its length is developed. The analysis consists of assuming that the plate thickness and plate stiffness are functions of the axial distance x. The resulting thin plate equation becomes a fourth-order differential equation with variable coefficients. The equation is solved by Fourier transform techniques and a solution in the transformed plane is obtained. The analysis is then applied to a constant thickness plate with sinusoidally varying stiffness. For simplicity, the effect of fluid loading is neglected and the forcing function is assumed to be given by a distributed load. Results in the form of plate displacement disribution are presented.
Effects of stress and final consonant voicing on vowel articulation and formant patterns
Authors: Summers Walter V.
Published: October 2005

Stress level and voicing of a postvocalic consonant are two factors known to influence vowel duration. In the present study, vowel durations, jaw and lower lip movement data, and formant data were examined for a set of b-vowel-consonant utterances differing in stress and final consonant voicing. As expected, vowel durations were greater for stressed utterances and for utterances containing voiced final consonants (voiced utterances). Articulator lowering and raising gestures were more rapid and more extensive for stressed versus unstressed utterances. At the acoustic level, stressed uterances demonstrated more rapid initial formant transitions and more extreme steady-state frequencies than unstressed utterances. In contrast, increases in vowel duration due to voicing were not accompanied by increases in the velocity or magnitude of articulatory gestures. In addition, voiced utterances did not demonstrate steeper formant transitions or more extreme steady-state frequencies than voiceless utterances. The results demonstrate that stress-related and voicing-related changes in vowel duraton are accomplished by separate and distinct transformations with observable consequences at both the articulatory and acoustic level. [Work supported by NINCDS and the Stuttering Center, Baylor College of Medicine.]
Interaction of phonemic quantity with speech rate and emphasis
Authors: Välimaa-Blum Riitta
Published: October 2005

Finnish has a quantity contrast in both consonants and vowels. It also has primary stress on the word-initial syllable. But, unlike in Czech, there is no neutralization of vowel length in stressed positions, i.e., a stressed syllable may contain either a phonemically short or long vowel. Vowel length is one of the major stress cues in a language like English but obviously in Finnish this use would conflict to some extent with its use in contrasting phonemes. In comparing word structures CVCV, CVVCV, and CVCCV in Finnish it was found that the final vowel in CVCV words was significantly longer than in the other two where the first syllable is long. It would appear as if the effect of the stress were spread over the two syllables in the CVCV words. The same lengthening has been found in an earlier study in normal speech rates in nonemphatic positions. The present study found this effect in both normal and fast speech rates, in two different sentence positions and in three different emphasis conditions.
Patterns of coarticulation in English
Authors: Huffman Marie K.
Published: October 2005

Recent work on vowel-to-vowel coarticulation [e.g., Krakow and Manuel (1984), Magen (1984)] has identified language specific coarticulatory patterns. These include differences in relative strength of carryover versus anticipatory coarticulation (sometimes called “directionality”) and differences in the freedom of vowels to vary. Such results suggest that coarticulatory patterns of individual language are more complicated than was thought previously. The present study examines vowel-to-vowel coarticulation in English with respect to several variables, primarily stress and consonant manner of articulation. Tokens recorded were of the form VCV and bVCəCVb, where the vowel was one of /i,a,u/ and the consonant was one of /l,d,r/. These nonsense words were said in a frame, with stress on the first or the last syllable. Formant frequencies were measured, using LPC analysis, at several points in these tokens. Our data suggest that stress of the affected vowel influences amount of carryover coarticulation more than stress of the affecting vowel does. Other results include indications that coarticulatory directionality can vary within a single language; here both identity of the consonant and stress play a role. [Work supported by NSF.]
Articulatory reorganization in deaf talkers
Authors: Osberger Mary Joe , Netsell Ronald , Goldgar David
Published: October 2005

The ability of five intelligible deaf talkers to reorganize articulatory gestures was examined with the use of a bite block. Each subject produced the phrase “say a pVp again” (where V = [i, a, u, æ, ı] or [ɛ]), with 14 repetitions of each vowel in random order. The speech samples were obtained with and without the subjects wearing their hearing aids. Measures of VOT, vowel duration, F1, and F2 were obtained from wideband spectrograms. The speech of the two subjects with an early onset of deafness was affected by the presence of the bite block whereas the speech of the remaining three subjects, whose deafness occurred in adulthood, was not. Performance was similar for all subjects irrespective of whether they were wearing their hearing aids. The role of auditory information in the formative years of speech motor control is discussed. [Research supported by the Easter Seal Research Foundation and a Biomedical Research Support Grant from the NIH.]
Correlation of SPINE test scores with measures of tongue deviancy computed from formant frequencies in hearing-impaired speakers
Authors: Wold Donald C. , Evans Christy R. , Dancer Jesse E. , Montague James C.
Published: October 2005

When the first three formant frequencies are given in vowel production, plausible midsagittal vocal tract shapes may be generated easily [D. C. Wold, J. Acoust. Soc. Am. Suppl. 1 78, S55 (1985)]. As a measure of tongue deviancy, this technique was used to compute the root-mean-square deviation with vocal-tract widths computed from measured formant frequencies and the standard widths computed from average formant frequencies for adults. The vowels selected for analysis were /i/,/u/, and /a/. A perceptual speech intelligibility test for the hearing-impaired, called SPINE for speech intelligibility evaluation, was administered to 28 hearing-impaired speakers. The Pearson product-moment correlation was computed between the SPINE test scores of the subjects and the inverse of the tongue deviancy. The preliminary results were positive with r equal to 0.53 (p<0.01), 0.02, 0.27, and 0.54 (p<0.01) for /i/,/u/,/a/, and the vowels combined, respectively. Thus verbal speech intelligibility scores for the hearing-impaired group were inversely related to a simple measure of tongue deviancy.
Intra-speaker analysis of the nasal consonant [m]
Authors: Oyer H. J. , Qi Y. , Lambert C. , Crowe B.
Published: October 2005

The acoustic spectrum of the nasal consonant [m] was analyzed from utterances of subjects as they produced it (1) in monosyllables, (2) in the reading of a paragraph, and (3) in attempts to disguise their voices while speaking a sentence. Findings indicate that although there is considerable intra-subject variability in the overall spectrum of the [m] consonant, the first formant remains remarkably constant. LPC analysis was employed in extracting acoustic characteristics. The results of this study have implications for speaker identification.
Age-related differences in phoneme durations among females
Authors: Brown W. S. , Morris Richard J.
Published: October 2005

Reduced speech rate has been consistently reported for geriatric speakers when compared to the speech of younger adults. Only recently have the specific aspects of the speech signal associated with reduced rate been identified. The purpose of this study was to examine vowel and consonant durations using certain physiologic measures to determine their effect on age-related differences in speech rate. Two groups of 25 women—one 20–30 years old and another 75 years and older—who had no history of speech disorders and exhibited normal hearing (for age level) served as subjects. They repeated a series of CV, VCV, and VC syllables using the consonants /p/, /b/, /t/, /d/, /s/, and /z/ combined with the vowel /ɑ/, which were spoken in the carrier phrase “Speak 3♯ again.” Intraoral air pressure and the voicing signal were recorded to provide vowel and consonant temporal information. Consonant duration did not differ significantly between the two age groups. Conversely, vowel durations were greater for the older females. These results are in agreement with previous studies and will be discussed in relation to a general model of aging.
Analysis for synthesis of arabic pharyngealized sound
Authors: Rajouani A. , Najim M. , Mouradi A. , Chiadmi D.
Published: October 2005

Our interest in extracting relevant acoustic parameters and formulating phonological rules for a project oriented towards realization of text-to-speech synthesis by rule system for the Modern Standard Arabic (MSA) language. The present work includes the parametrization of the MSA pharyngealized consonants /Ṡ/, /sṠ/, /ḍ/, /ðṠ/ according a Klatt serial/parallel formant synthesizer. Emphasis is made on the phonological level to define an adequate vowel system for the MSA by adding the pharyngealized vowels and to establish a set of rules dealing with the propagation of the pharyngealization feature. Evaluation of the synthesis strategy attests that the transition rules are independent of the presence of the pharyngealization. Synthetic speech generated from the developed synthesis-by-rule program is validated by Moroccan native informants. [Work partially supported by UNESCO.]
Liquid metal thermoacoustic engine
Authors: Swift G. W. , Migliori A. , Wheatley J. C.
Published: October 2005

A liquid metal thermoacoustic engine is studied both theoretically and experimentally. This type of engine promises to produce large quantities of electrical energy from heat at modest efficiency with no moving parts except the acoustic oscillations in the liquid metal. In the engine, heat flow from a high-temperature source to a low-temperature sink amplifies a standing acoustic wave in liquid sodium. This acoustic power is simply converted to electric power by means of a magnetohydrodynamic effect at the acoustic oscillation frequency. A detailed thermoacoustic theory applicable to this engine is developed, and it is found that a reasonably designed liquid sodium engine operating between 700 °C and 100 °C should generate about 60 W/cm2 of acoustic power at about 1/3 of Carnot's efficiency. Construction of a 3000-W thermal laboratory model engine is almost complete. A 1-kW, 1-kHz liquid sodium magnetohydrodynamic transducer has also been designed and built. It is now very well characterized both experimentally and theoretically. The first generator of its kind, it already converts acoustic power to electric power with 40% efficiency.
Effects of sediment parameters on data analysis of low-frequency beamformed bottom-propagating modes
Authors: Ioup G. E. , Werby M. F. , Tango G. J.
Published: October 2005

It has been previously shown [Tango, Werby, and Wooten, J. Acoust. Soc. Am. Suppl. 1 78, S71 (1985)] that shallow water sediments typically exhibit characteristic mode angular spectra when sampled by a towed or synthetic aperture array. In this paper, we further examine systematic effects of shallow layer thickness, compressional and shear velocity values, and depth distribution on simulated FFT-beamformed array responses. For a given source frequency and geobottom model, an increase in layer thickness simply increases the trapped mode response from the layer in question at the expense of leaky modes, and trapped modes from other depths. For sufficiently large numbers of layers and/or strong velocity gradients, clear critical angle information is complicated or lost in the beamformed pressure field response. Mode angular spectra are essentially independent of sediment shear rigidity for vS < vwater; for larger shear velocity values, an additional attenuation as well as shear specific modes can result. Although effects of increased P and S wave sediment attenuation will effect observed mode amplitude [Frisk and Lynch, J. Acoust. Soc. Am. 76, 205–216 (1984)], these effects are generally below the side lobe noise and resolution of the present beamforming algorithm. By using an alternative mode sampling strategy, as well as additional beamformed signal attributes, it is possible that improved accuracy and resolution can be obtained.
Full-wave modeling of comparative deep sea bottom-interacting propagation to ocean bottom and sub-bottom receivers
Authors: Tango G. J. , Wooten R. P. , Werby M. F.
Published: October 2005

A full-wave FFP reflectivity method [Schmidt and Tango, Geophys. J. R. Astron. Soc. (December 1985)] is applied to the problem of determining the characteristics of long-range, low-frequency signal propagation levels, at and beneath the seafloor, as seen by comparative horizontal and vertical arrays of hydrophones and geophones. Seisacoustically equivalent deep sea models for real variations in both fine scale shallow sediment and gross deep crustal velocity/depth structure are examined, to determine their effect on predicted signal level versus range and depth. Synthetic cw transmission loss and broadband horizontal and vertical seismic profile data reveal an overall trend of monotonically decreasing signal level with depth, interrupted by localized zones of relatively lower signal loss (3–7 dB), in agreement with synthetic and experimental borehole data for exploration seismic scenarios [Ganley and Kanasewich, J. Geophys. Res. (1981)]. Environmental and experimental factors controlling signal strength versus depth behavior are presented, and problems for further study are outlined.
In-situ measurements of selected geo-acoustic properties of carbonate sediments at the Great Bahama Bank
Authors: Bennett Richard H. , Yamamoto Tokuo
Published: October 2005

In-situ measurements were made of geo-acoustic properties of the various marine sediments at the Great Bahama Bank in November 1985. The depth profiles of density and porosity of the sediment were measured by an electrical conductivity probe. The depth profile of permeability was measured by an in-situ parameter. The water-wave-induced pressure and ground motion were measured by a bottom shear modulus profiler. Continuous cores of sediments were also taken for laboratory analyses. This paper presents the experimental techniques and the measurements. Two separate papers in this meeting present measurements of the complex velocities of compressional and shear waves and propagation of acoustic normal modes using in-situ and laboratory measurements from this field test. An ELAC sub-bottom profiler was used to survey the carbonate sediments to determine lateral and vertical variability. [The work was sponsored by ONR Code A25GG and Code 425UA.]
Economic trends in the U. S. industry
Authors: Kutscher Ron E.
Published: October 2005

Is the U.S. losing its industrial base? This paper presents evidence that the industrial sector as a whole is in healthy shape, but a small number of manufacturing industries are in deep trouble. Our findings indicate that the well-reported shift to service industries is not really evidence of a declining industrial base or “de-industrialization,” but rather part of a long-term structural change in the U.S. economy. That structural change may have accelerated in the last business cycle trough but goods producing industries including manufacturing have bounced back during the recent upswing and have reached a new peak.
Research needs for standards development regarding noise in the workplace
Authors: Eldred Kenneth McK.
Published: October 2005

The methodology for measurement and evaluation of noise in the workplace has evolved from the work of many organizations in the USA and abroad. In the 1950s the Department of Defense initiated major hearing conservation programs in the services. In the late 1960s the Department of Labor promulgated its first noise standards under the Walsh Healy Act, and in the early 1970s other agencies including the Environmental Protection Agency, Department of Transportation, and the Bureau of Mines initiated programs in these areas of responsibility. Also, during the 1970s the national and international voluntary standards sectors began the development of a set of standards for measurement and evaluation of noise in the workplace. In the initial planning of these standards it became apparent that research would be needed to develop meaningful standards, particularly in areas outside DOD. This paper outlines the current and proposed future plans for voluntary standards in this area and identifies a set of research tasks and objectives that are required to support a comprehensive standards development effort.
Ultrasonic tissue characterization: A Review
Authors: Jones Joie Pierce
Published: October 2005

Present medical ultrasound systems are based on envelope detection methods and therefore display only echo intensity information. However, phase information is also recorded by the transducer which is a pressure-sensitive device, but is not utilized in commercial display or measurement schemes. This additional information may be of diagnostic significance since the interaction between sound and tissue acoustical properties can be correlated with specific pathological states. Thus, in principle, in vivo techniques could be devised which would extract and separate the medically significant features of the ultrasound interactions with tissue and would display ultrasonic tissue signatures appropriate for a differential diagnosis. The development of such quantitative techniques for the measurement of ultrasonic tissue parameters and/or the display of ultrasonic tissue signatures has become known as ultrasonic tissue characterization. In this paper we review the physical basis for ultrasonic tissue characterization, describe several characterization schemes currently being explored, and attempt to assess likely future developments in the field as well as the importance such techniques may play in the future of diagnostic medicine.
Medical flow imaging with ultrasound
Authors: Johnson Richard K.
Published: October 2005

Recent technology advances have made possible commercial machines which produce real-time images of blood flow for medical applications. Design approaches will be discussed for the issues of velocity range and resolution, tissue and flow differentiation, two-component image processing, and frame rate. A videotape of clinical flow images will be shown.
Acoustic study of artificial blood substitutes
Authors: Gultepe M. A. Barrett , Gultepe M. E. , McCarthy J. L. , Yeager E.
Published: October 2005

Absorption and velocity of sound were measured in various submicron size perfluorochemical (PFC) emulsions in water of the types considered for use as artificial blood substitutes. The attenuation of sound was measured in the frequency range 1 to 95 MHz with computer-assisted VHF and UHF send-receive apparatus. Concentrated aqueous emulsions of F-decalin, F-tributylamine, and F-phenanthrene stabilized by various surfactants including fluorinated surfactants were studied as well as Fluosol-43 emulsion, a commercially produced emulsion for use as an artificial blood substitute. The attenuation of sound waves in the abovementioned PFC emulsions can be theoretically described by heat conduction losses, viscous drag losses, and scattering of sound. In contrast to the majority of hydrocarbon/water emulsions, in PFC emulsions the contribution to acoustic absorption of the viscous drag losses and heat conduction losses are approximately equal to magnitude, though shifted in frequency. This is a result of the high density of perfluorochemicals. [Work partially supported by Advanced Biosystems Inc.]
Nucleation of acoustic cavitation from a gas-filled crevice
Authors: Atchley Anthony A. , Prosperetti Andrea
Published: October 2005

The nature of the cavitation nucleus, although the subject of considerable attention by physical acousticians in the past, continues to be important, in part because of the recent increased investigation of cavitation in biological systems. At a previous meeting Atchley and Crum [J. Acoust. Soc. Am. Suppl. 1 76, S64 (1984)] presented some preliminary results of a rederivation of the crevice model of cavitation nucleation. In the present paper, the final results of this work are discussed. According to the model, a gas pocket stabilized at the bottom of a conical crevice residing on a hydrophobic solid impurity acts as the cavitation nucleus. In order for cavitation to occur, the nucleus must be mechanically unstable and the liquid-gas interface must reach the receding contact angle. The theoretical predictions of this model agree quite well with the results of measurements made in water. [Work supported by ONR and NSF. AAA would like to acknowledge the support of the Hunt Fellowship.]
Evaluation by computer simulation of stopping rules for audiological ascending test procedures
Authors: Marshall Lynne , Hanna Thomas E.
Published: October 2005

Stopping rules for ascending audiological test procedures were evaluated by Monte Carlo simulation. The stopping rules differed in the minimum number of correct responses required at a level, whether these responses occurred on half or a majority of the ascents, whether a limit was placed on the number of ascents, and whether all or only the most recent ascents were considered. Simulated threshold values ranged from − 12 to 92 dB SPL in steps of 1 dB. Slopes of the psychometric functions ranged from 0.1 to 1.0 in steps of 0.1. For each procedure, 200 threshold determinations were simulated for each combination of slope and threshold value. For all procedures, shallow slopes resulted in thresholds closer to the level giving 50% detection than did higher slopes, which were roughly 2.5 dB above 50% on the psychometric function. Shallow slopes also resulted in decreased consistency across threshold measurements, an increased number of trials required for threshold estimates, and a higher proportion of estimates that had to be repeated to obtain threshold. Stopping rules using a two-response criterion were faster than those using a three-response criterion, with only a small decrease in consistency. Among stopping rules using the same number of responses for criterion, differences were seen primarily in efficiency at shallow slopes, particularly for procedures using a three-response rather than a two-response criterion fur stopping.
Human tone detection in continous- and pulsed-noise maskers
Authors: Pressel David M. , Sachs Murray B.
Published: October 2005

A two-interval, forced-choice paradigm was used to measure the critical ratio of human subjects detecting a tone burst in continuous noise and noise gated simultaneously with the tone bursts. Noise spectrum levels of 35, 15, and − 5 dB SPL/Hz were used; tone frequencies were 500, 1000, 2000, 4000, and 8000 Hz. At 4000 and 8000 Hz, critical ratios were significantly larger for the simultaneously gated noise than for continuous noise. There were no significant differences between the critical ratios for continuous and gated noise at frequencies of 500, 1000, and 2000 Hz. These results are consistent with those of Wier et al. [J. Acoust. Soc. Am. 61, 1298–1300 (1977)] and extend those results to higher frequencies where differences between the continuous and simultaneously gated masking cases are greater.
Temporary threshold shifts from attendance at a rock concert
Authors: Clark William W. , Bohne Barbara A.
Published: October 2005

The relation between exposure level and hearing loss in rock concert attendees was studied. Six volunteer subjects, ages 16–44, participated. All except the 44-year-old had normal hearing sensitivity, as revealed by audiometric evaluations made immediately before the concert. They attended a Bruce Springsteen concert at the St. Louis Arena and returned to CID for another hearing test within 30 min following the concert. Noise exposure was assessed by having two subjects, seated at different locations in the arena, wear calibrated dosimeters during the event. Sixteen hours after the concert all subjects returned for a final audiometric evaluation. Results indicated that the average exposure level was 100–100.6 dBA during the 412-h concert. Five of the six attendees had significant threshold shifts (< 50 dB) predominately in the 4-kHz region. Measures made 16 h after the concert and thereafter indicated that hearing returned to normal in all subjects. Although no PTS was observed, comparison of these data with studies of hearing loss and cochlear damage in animal models suggests that these subjects may have sustained some sensory cell loss from this exposure. [Work supported by NIOSH and NINCDS.]
PET measurement of regional cerebral blood flow changes during noise stimulation
Authors: Sidtis J. J. , Dhawan V. , Jarden J. O. , Strother S. C. , Rottenberg D. A.
Published: October 2005

Positron emission tomographic (PET) studies of regional cerebral blood flow (rCBF) using the steady-state 0–15 carbon dioxide (CO2) method allows within-subject stimulation and control studies to be performed in the same session. Using this technique, we previously reported data suggesting that broadband white noise increased rCBF significantly. In the present study, we examined the temporal course of these changes. Six normal volunteers were studied with eyes covered while CO2 was inhaled through nasal prongs. Fourteen serial 1-min images were acquired in the following sequence: 2-min quiet, 6-min auditory stimulation, 6-min quiet. Arterial blood was automatically sampled every 18 s. The stimulation protocols replicated conditions used previously to study the physiological effects of noise [J. Meyer-Delius, Automobile Tech. J. 59, 293 (1957)], with broadband white noise presented binaurally through earphones at 90 dBA with an on/off cycle of 30 s. Region of interest (ROI) data were obtained for at least 30 regions across 9 planes for each of the 14 time frames using a thresholding technique. Transient rCBF increases occurred in most ROI's within the first 1–3 min. Increased rCBF was also observed after the stimulation period ended, most consistently in cerebellum and paracentral regions where 10%–30% increases were seen in all subjects. These results suggest that rCBF changes with auditory stimulation have a significant temporal component that is not uniform across brain regions. This component must be defined when regional brain response to auditory stimulation is studied.
Low noise microphone for cochlear emissions
Authors: Killion Mead C. , Stewart Jonathan K.
Published: October 2005

A specialized microphone for use in measuring cochlear emissions contains four modified Knowles microphones mounted in mechanical opposition for minimum vibration sensitivity in their summed output. That output is electrically equalized to provide a flat frequency response from 100 Hz to 12 kHz when measured with a disposable foam eartip containing 10 mm of 3.8-mm-i.d. probe tubing. To facilitate measurement of stimulated emissions, and especially cochlear distortion products, the construction includes two 1.35-mm-i.d. earphone coupling tubes mounted to pass through the 3.8-mm-i.d. probe tubing, permitting the delivery of stimuli from two independent ER-2 insert earphones, each providing a flat eardrum-pressure frequency response to 12 kHz. The complete microphone exhibits a typical noise spectrum level of − 20 dB SPL at 1 kHz decreasing to − 26 dB at 5 kHz, 8 to 10 dB below that of a single Knowles EA-1954 microphone and 5 to 10 dB below the apparent noise level of good young ears based on the estimate of Killion [J. Acoust. Soc. Am. 59, 424–433 (1976)].