bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustically induced depolarization of light diffracted by surface acoustic waves
Authors: Graver William R. , Ngoc Tran D. K. , Mayer Walter G.
Published: October 2005

Depolarization of light upon interacting with an interface is reviewed for two cases: with and without the presence of surface acoustic waves (SAW's). The characteristics of depolarization in the case of light diffraction by SAW's are examined oin the basis of a phenomenological model developed by Stegeman [G. I. Stegeman, J. Appl. Phys. 49, 5624–5637 (1978)]. This model was constructed by considering the two scattering mechanisms associated with the surface corrugation and elastoptic effects. Specifically, the s- and p-polarized electric field components are investigated as functions of the incident angle, acoustic intensity and acoustic frequency. [Work was supported by the Office of Naval Research.]
The effect of laser beam oblique incidence and optical refraction on the characteristics of an optoacoustic source in a liquid
Authors: Berthelot Yves H.
Published: October 2005

The generation of underwater sound by a laser beam is very attractive because the laser path can be accurately controlled by means of optical components (rotating mirrors, grating, lenses, etc.) so that a virtually unlimited number of source configurations are, in fact, achievable. In most practical designs, the laser beam illuminates at oblique incidence a body of water so that optical refraction actually occurs at the air-water interface. This effect is now investigated by extending the analysis presented previously [J. Acoust. Soc. Am. 78, 2074–2082 (1985)]. It is shown that the impulse response of a laser-induced thermoacoustic source is strongly dependent upon the angle of incidence of the laser beam, although optical refraction tends to minimize this effect. Directivity patterns and propagation curves are also found by taking the Fourier transform of the modified impulse response of the optoacoustic system; it is found that they can be significantly affected by an oblique incidence of the laser beam.
Acoustic resonance of a cylindrical cell in an optoacoustic spectrometer
Authors: Wright Wayne M. , Gardner Edward A. , Hays Paul B.
Published: October 2005

The optoacoustic spectrometer is an instrument with which one can study the absorption of light by a sample of gas. Thermal energy provided by a periodically interrupted laser beam is converted to an acoustic signal of the same frequency, and the amplitude of this signal often is increased through operation at an acoustic resonance frequency of the sample cell. The construction of one such spectrometer and its use to study the variation of acoustical properties of a cylindrical cell with ambient pressure are described. Measurements have been made with the monochromatic light produced by a tunable dye laser, with atmospheric oxygen as the optically absorbing gas, and over the pressure range 0.05–1.0 atm. The acoustic “Q” for the 4.1-kHz first azimuthal mode of the 5-cm-diam cylindrical sample cell is found to decrease by less than 10% (from approximately 100) as the pressure is reduced from 1 to 0.5 atm, and then to fall off much more rapidly. The position of the commercial 1-in. condenser microphone on the cylindrical cell wall is shown to have a significant effect on the cell resonance frequency. [Work supported, in part, by NSF.]
Intensity jnd's for equally loud tones in quiet and noise backgrounds
Authors: Rankovic C. M. , Cheesman M. F. , Fantini D. A. , Uchiyama C. , Viemeister N. F.
Published: October 2005

Recent studies of the relation between loudness and intensity jnd's suggest that the size of the jnd corresponds to loudness magnitude rather than to the slope of the loudness function. Specifically, Zwislocki and Jordan [J. Acoust. Soc. Am. Suppl. 1 77, S64 (1985)] conclude that the intensity jnd's for a pure tone are equal in recruiting and normal ears when the loudnesses of the tones are equal. Similarly, Hellman et al. [J. Acoust. Soc. Am. Suppl. 1 77, S64 (1985)] conclude that when a pure tone in narrow-band noise is judged to be equally loud to a tone in wideband noise, the jnd's for those tones are the same. We show exception to these studies. Loudness matches and intensity jnd's for a 1000-Hz pure tone in quiet and in a 40-dB spectrum level broadband noise were obtained for four normal-hearing subjects. The data indicate that equally loud tones yield equal jnd's only at intensities near threshold and at high intensities where equal loudness corresponds to equal SPL. At other intensities, the jnd is larger in noise than in quiet. [Supported by NIH NS12125, NS07889, and by a training grant, NICHHD T32 HD-07151, awarded to CMR by the Center for Research in Human Learning.]
Level discrimination as a function of level and frequency between 0.25 and 16 kHz
Authors: Florentine Mary , Buus Soren , Mason Christine R.
Published: October 2005

Difference limens, DLs, for the level of tones were measured at 0.25, 0.5, 1, 2, 4, 8, 10, 12, 14, and 16 kHz as a function of level. Approximately ten levels ranging from near threshold to about 100 dB SPL were used. The stimuli were 500-ms tones with an interstimulus interval of 250 ms. An adaptive 2I, 2AFC procedure with feedback was used. The results show rather large consistent individual differences among normal listeners, but some patterns can be observed in the average DLs. First, DLs at all frequencies are generally better at high levels than at low ones, but the DLs above 8 kHz often are larger at moderate levels than at high and low levels. Second, the DLs at any fixed SPL are largely independent of frequency up to 4 kHz, but increase with frequency above 4 kHz. The behavior of the DLs at high frequencies presents a challenge to current models of level discrimination. [Supported by NIH-NINCDS RO1NS18280.]
Four factors in loudness change
Authors: Smith Laurie , Weiler Ernest M.
Published: October 2005

The use of direct magnitude estimation (ME) of loudness has recently been very useful in the study of auditory adaptation effects. The current study proposed to compare ME loudness adaptation to the widely studied adaptation effects measured by the classic simultaneous dichotic loudness balance technique. Three conditions were administered to each of 18 SS at 60 dB SPL, 1000 Hz. Condition I consisted of 7 min of the stimulus with ME judgments taken at the beginning and end. Condition II consisted of the SDLB procedure with binaural pretest balance values determined in dB, 7 min of monaural stimulation in the second stage, and dB balance determined binaurally in the final stage. ME loudness values were also taken at each stage. Condition III consisted of a parallel to condition II, but without the dB adjustments or balances that are normally found in SDLB procedures. Only ME judgments were taken during the three stages of condition III. Results of ten dependent measures were subject to factor analysis, with four factors identified. These independent factors appear to account for the reported disagreements between ME loudness adaptation and SDLB related effects.
Structural intensity flow in and acoustic radiation from thin plates with damped structural discontinuities
Authors: Washburn Karl B. , Williams Earl G.
Published: October 2005

SIMMAP (structural intensity mapping from measurement of acoustic pressure), an outgrowth of nearfield acoustical holography, provides two-dimensional mappings on the surface of a vibrating plate of the structural intensity, mechanical injected power, and acoustic power radiated into the fluid [E. G. Williams et al., J. Acoust. Soc. Am. 78, 2061–2068 (1985)]. The relationship between mechanical injected power (into the plate), radiated acoustic power (from the plate), and the effects of structural discontinuities on both are demonstrated over the surface region of the plates. The data from the four experimental configurations confirm that, while acoustic intensity mapping effectively pinpoints radiation sources, SIMMAP is more dependable in locating mechanical sources (e.g., a shaker) and sinks (e.g., damped structural discontinuities). The technique clearly reveals net mechanical power extraction by damped discontinuities and preferential acoustic radiation from regions where they are attached, indicating a powerful tool for analysis of vibration damping. [Work supported by DTNSRDC, Annapolis, MD.]
Wavenumber/frequency response of free beams to multiple-point excitation
Authors: Hutto Frederick M. , Burroughs Courtney B. , Hughes W. Jack , Grosh Karl
Published: October 2005

Using Timoshenko beam theory, an analytic model for the free response of a thick free-free beam and the forced response of the beam to a continuous drive and an array of point drives is presented. To validate the model, comparisons of predictions are made to measurements of the free response of a beam, the magnitude and phase of the point and transfer admittances of a beam driven by point drives of one, two, and three locations, and the wavenumber/frequency response of a beam driven at point drives at one, two, and three locations. The excellent agreement shown validates the analytic model, which is then used to show the wavenumber response of a beam as a function of the wavenumber of a continuous drive and the steered wavenumber of an array of point drives.
Application of a variational principle to acoustic radiation from a vibrating finite cylinder
Authors: Wu X.-F. , Pierce A. D. , Ginsberg J. H.
Published: October 2005

A variational principle derived from the Kirchhoff-Helmholtz integral corollary is applied to a rigid cylinder; previous applications have been to acoustic radiation and diffraction from an infinitely thin disk [J. H. Ginsberg et al., J. Acoust. Soc. Am. Suppl. 1 77, S60 (1985)]. For a finite length circular cylinder, additional complications are encountered because of the need to consider the cylindrical sides as well as ends. The basis functions for a Rayleigh-Ritz solution have different analytical forms on the sides and ends, although they must be continuous at the edges. A larger number of functions are required to get a good representation of the surface pressure. Calculation of the resulting matrix elements for the determination of the expansion coefficients is nontrivial because of the logrithmic singularities presented by the Green's function integrals. The surface pressure is expected to be finite, but the tangential derivative of the surface pressure is a priori known to have a s−2/3 singularity at the edges separating the side wall and ends. It is not necessary that trial functions exhibit the latter behavior, but if they are so chosen, a good convengence is expected for a smaller number of basis functions. A numerical method based on splitting each integrand into a simple singularity term plus a nonsimple but bounded term is described. Numerical results are compared with those obtained by an alternative technique developed by P. H. Rogers [NRL Report 7240 (19 June 1972)].
Comparison of different methods for the dynamic analysis of beam surfaces
Authors: Tavakoli Massoud S.
Published: October 2005

Beam structures such as multispan beams and frames are used to compare the dynamic analysis methods. The first method is the receptance technique in which the precalculated receptance coefficients are used to model the junction of the beam segments. The second method is concerned with the component mode synthesis where simple polynomials are utilized as mode shapes. Some or all of the joint conditions are then enforced and hence the natural frequencies and mode shapes are approximated. The third method takes advantage of the energy approach. The Lagrangian for the entire system is obtained by adding the Lagrangians of individual components. Minimization of the overall Lagrangian results in the natural frequencies and mode shapes. Finally, the advantages and disadvantages of these methods are discussed.
Tone and intonation in Cantonese
Authors: Johnson Keith
Published: October 2005

The phenomenon known as an F0 downtrend has recently been attributed to local phonological rules (such as downstep and final lowering) in English. A preliminary study of Cantonese seemed to indicate that a back-drop F0 decline is an important aspect of the Cantonese intonational system. In that study it was found that the preservation of lexical tones in Cantonese sentences could best be accounted for when declination was included in the description. In the study to be reported in this paper the method used in the preliminary investigation is refined and two tests of a possible declination effect are employed. The refinements include: (1) recording sentences in utterance medial position, and (2) using pragmatically neutral sentences (i.e., the target sentences neither introduce nor conclude a discourse topic). The first test for declination is the tone preservaton criterion used in the preliminary study. The second has to do with the presence or absence of a correlation between the ratio of F0 measurements of early and late occurrences of a tone and the number of syllables intervening between the two occurrences. Such a correlation between F0 ratio and number of intervening syllables would indicate a declination effect (if the slope is negative). If no evidence for declination is found then the approach which attributes downtrend to local phonological rules is supported. If evidence for declination is found then declination must be included among the possible methods of accounting for downtrend.
Coarticulation across secondary articulations
Authors: Keating Patricia A.
Published: October 2005

Consonants with secondary articulations, which involve simultaneous consonant and vowel-like articulations, are found as contextual allophones in many languages and as independent phonemes in some languages. These consonants show special behavior with respect to vowel-to-vowel coarticulation, as determined from acoustic measurements. Phonemic secondary articulations in stops, fricatives, and liquids of Russian, Bulgarian, and Arabic generally block any vowel-to-vowel influence across the consonant. However, contextual secondary articulations in Russian, Bulgarian, Polish, and English generally propagate extreme effects of one vowel onto the other. Both of these differ from the usual coarticulation across consonants without secondary articulations. These results can be accounted for if we distinguish the representations of phonemic secondary articulations (as consonants with their own vowel features), from contextual secondary articulations (as consonants acquiring features from adjacent vowels), from lack of secondary articulation (as consonants with no vowel features). Given such a distribution of vowel features, phonetic interpolation can proceed straightforwardly between adjacent feature values.
Long consonants versus geminate consonants in Arabic
Authors: Miller Ann M.
Published: October 2005

If a phonetic distinction can be made between long consonants and geminate consonants (a cluster of two like consonants), it should be cued by durational differences in the absence of a distinctive release. Arabic provides a means for comparing these types of consonants since it has phonemically distinct long consonants word initially and medially, and clusters of like consonants across word boundaries. We performed an experiment with speakers of Levantine Arabic to compare these conditions. We also tested clusters which result from assimilation of the /l/ in the definite article /ʔil/ to following dental consonants to see whether these patterned like true clusters or like long consonants, indicating cliticization. Surprisingly, no differences in duration occurred between these conditions. Moreover, one occurrence of a medial long consonant had an apparent release, as did several of the clusters across word boundaries and one of the clusters involving the definite article. These results suggest that medial lengthened consonants in Arabic are not long consonants as in Japanese and Finnish but are actually clusters.
Declination in Toishan
Authors: Lee Gina M.
Published: October 2005

Many have noted a tendency for fundamental frequency to gradually lower during the production of an utterance. This downtrend has sometimes been attributed to declination, a phonologically unmotivated lowering of F0 that is independent of tone. Recently, Johnson [Meeting Handbook, LSA, 21 (1985)] discovered data consistent with the view that declination exists in Cantonese. Like Cantonese, Toishan (another Yue dialect) exhibits little, if any tone sandhi. To see whether Toishan likewise exhibits declination, we had native speakers produce sentences containing high level tones, with varying amounts of material between the target high tones. The sentences are organized into passages so that, in addition to an examination of declination at the sentence level, an examination can be made at the discourse level as well (since it is possible that the degree of declination within a sentence depends on the position of the sentence within the discourse unit).
Palatoglossus activity during oral/nasal vowels of Hindi
Authors: Dixit R. Prakash , Bell-Berti Fredericka , Harris Katherine S.
Published: October 2005

Palatoglossus EMG potentials and voice were recorded while a native speaker of Hindi produced CVC nonsense utterances where C was /s/ and V was one of the vowels /iιeɛəɑɔoɷu,ĩι̃ẽɛ̃ə̃ɑ̃õñɷ̃Ũ/. Preliminary results show low levels of EMG activity for the front oral vowels, whereas for the central and back oral vowels the EMG activity is considerable. All nasal vowels exhibit a high level of EMG activity, except /ẽ, ɛ̃/ for which the EMG activity is minimal. EMG levels for the central and back nasal vowels are considerably higher than those for the front nasal vowels. EMB levels for the nasal vowels /õ, ñ, ɷ̃, Ũ/ are comparable to those for the oral vowels /ɔ, o, ɷ, u/, respectively. However, the EMG levels for the nasal vowels /ĩ, ι̃, ə̃, ã/ are considerably greater than for the comparable oral vowels /i, ι, ə, ɑ/. Furthermore, the patterns of EMG potentials for the long vowels differ from those for the short vowels irrespective of their being oral or nasal. [Work supported by NIH Grant NS-13617 and BRS Grant PR-05596 to Haskins Laboratories.]
Lip-jaw coordination in hearing-impaired speakers
Authors: McGarr N. S. , Seider R. A. , Löfqvist A.
Published: October 2005

The question posed is whether interarticulator timing relationships are preserved in deaf speakers across speech transformations such as those induced by phonetic context and stress. Acoustic recordings were obtained simultaneously with kinematic records of lip and jaw motions using the Selspot infrared tracking device. The experimental corpus included real word utterances with a medial labial consonant (p,b,m,w,f,v) flanked by one high and one low vowel (e.g., “And Bea pops it”). The stimuli were produced by one hearing and three hearing-impaired talkers. Measures of jaw and lip displacement and velocity of movement were made in order to address questions of kinematics as a function of stress, phonetics, and vowel effects. Results for the hearing speaker showed the expected systematic differentiation of stressed and unstressed syllables. Preliminary results for the hearing-impaired speakers showed the relative interarticulator timing was more variable than the normal. However, the deaf speakers were like normal in that they differentiated vowels on the basis of jaw placement. These and other measures to investigate phonetic effects will be presented. [Work supported by NIH Grants NS-13617 and NS-13870.]
The effects of contrastive stress on stutterers' speech
Authors: Klouda G. V. , Cooper W. E.
Published: October 2005

Acoustic analyses were performed on the utterances of nine stutterers to examine the influence of sentence focus on frequency of stuttering and fundamental voice frequency (F0) patterns. The speakers orally read sentences containing contrastive stress prompted by preceding questions. The application of focus on a word led to a statistically significant increase in the frequency of stuttering on that word in all but sentence-final position. In nonfinal positions, the frequency of stutterers averaged 53% for focused words and 25% for nonfocused words. While previous results have indicated that stuttering is generally more likely on the first few words of a sentence than on later words, we found that the number of stuttering episodes decreased on successive words only if the later words in the sentence do not receive contrastive stress. The influence of sentence focus on F0 peaks throughout the course of the test sentences was found to be essentially the same as has previously been reported for normal speakers. The effects of contrastive stress on the F0 patterns were similar to those found for stuttering frequency, suggesting the possibility of a common underlying factor.
Acoustic analysis of amyotrophic lateral sclerosis speech
Authors: Caruso Anthony J. , Wilcox A. , Seikel J. Anthony , Haight Patti
Published: October 2005

Seventeen victims of amyotrophic lateral sclerosis (ALS), were recorded as they produced /p t k b d g/ in a CVC syllable embedded in a carrier phrase. The duration of the stop consonant closure period, the release burst, and the aspirated phase of each of the stops, as well as the total duration of all pre- and post-stop vowels was determined spectrographically. In general, the ALS speakers produced highly varied speech which included numerous instances of voicing throughout voiceless segments, frication of voiced and voiceless stops, and multiple release bursts. Comparisons of group mean durations, to those of normal speakers, indicates that the effects of decreased speaking rate in ALS are not evenly distributed across segments or portions of segments. Instead, some segment durations in ALS speech remain within normal limits while others increase relative to those seen in normal speech. Thus, the most sensitive acoustic/articulatory measure of the speech deterioration associated with ALS is achieved by comparing two or more durational measures with speakers. [Work supported by Kansas City Regional ALS Research Center, and NIH.]
Using speech as an index of alcohol intoxication
Authors: Martin Chris S. , Yuchtman Moshe
Published: October 2005

Although laypersons and low-enforcement officers routinely use perceived speech quality as an index of alcohol intoxication, there has been little research on the accuracy and limitations of this ability. In a recent study, we found that listeners could reliably discriminate between sentences produced by talkers speaking under sober and intoxicated conditions and that experienced listeners performed significantly better than naive listeners [Pisoni, Hathaway, and Yuchtman, SRL-PR ♯11, 109–172 (1985)]. In the present study, we compared the performance of college students and law-enforcement officers who were instructed to determine whether recorded sentences were produced under intoxication. In addition, digital signal processing techniques were used in an attempt to define changes in the acoustic-phonetic structure of speech under intoxication. The implications of this study for the role of speech as a reliable index of intoxication will be discussed. [Work supported by General Motors Research Laboratories.]
Age-related differences in speech intensity among females
Authors: Morris Richard J. , Brown W. S.
Published: October 2005

Among the physiologic consequences of aging is a reduction of vital capacity. Since the volume of air available may influence speech output, studies of age-related speech differences have included intensity as a variable. These studies have produced conflicting results, some experimenters have reported that intensity range and maximum intensity are reduced as a function of age, while others reported increased mean conversational intensity associated with aged speech. The purpose of this study was to compare the intensity range, maximum intensity, and mean conversational intensity between a population of geriatric women and a population of younger women. Two groups of 25 women—one 20–30 years old and another 75 years and over—who had no history of speech problems and exhibited normal hearing (for age level) served as subjects. They performed three repetitions of /ɑ/ for 5 s each at a typical, maximum, and minimum intensity level. Recordings of these productions were digitized and analyzed for mean intensity, intensity mode, and intensity distribution. Results will be discussed in relation to a general model of aging.
Probing the interior of the sun and stars wtth acoustic modes of oscillation
Authors: Ulrich Roger K.
Published: October 2005

For reasons which are, at present, poorly understood, the sun and presumably stars like the sun undergo continuous oscillations. The most prominant of these have been identified as normal modes which are gravity-modified acoustic resonances involving the whole sun. The spatial structure of the modes is described as the product of spherical harmonics Ylm (θ,φ) and a radial eigenfunction. The value of l determines the depth of mode penetration for each value of n. The identification of the modes with l and n permits a comparison of the observed frequencies with theoretical ones and tests the adequacy of our solar models. The frequency degeneracy in m is broken by rotation, and the measurement of the fine structure of the frequencies permits a determination of the depth dependence of the solar rotation rate. Present results indicate that the sun does not deviate substantially from a condition of uniform rotation. These results appear to rule out the hypothesis that the solar gravitational potential could have a large enough quadrapole term due to solar internal rotation to invalidate tests of general relativity.
Acoustic pressure meusurement at high temperatures
Authors: Mahan J. R.
Published: October 2005

It is often necessary to measure the acoustic pressure in a high-temperature environment as, for example, in the study of combustion noise. High-temperature microphones have been developed, and techniques have been devised for adapting “room temperature” microphones for use in the high-temperature environment. The unique features of this measurement problem are identified, and state-of-the-art methods for its solution are presented and discussed. Particular attention is paid to the acoustic waveguide probe system, in which a common room temperature microphone is thermally isolated from the high-temperature environment through a pressure transmitting tube. Results of a recent analysis of such a system are presented and compared with new measurements. It is suggested that the probe system, when used with the model to correct for axial temperature gradients along the probe, may be the optimum solution to this difficult measurement problem.
Elastic constants of steel as a function of heat treatment
Authors: Yost W. T.
Published: October 2005

The velocity of sound and the nonlinearity parameters of HY80 3.25% NiCrMoV steel samples which were heat treated at 538 °C for periods ranging from 0–100 h were measured. Elastic constants (c11 and c111) associated with these measurements were reported, and they were compared with values obtained from other steels. It was found that the difference between measured values among the samples is larger than one would expect. Possible reasons for the discrepancies are discussed.
Resonant cavity techniques for accurate measurements of the ratio of the speed of sound to the speed of light
Authors: Mehl James B. , Moldover Michael R.
Published: October 2005

In principle, measurements of the resonance frequencies of both the acoustic and the microwave modes of a single cavity can determine the ratio of the speed of sound u of a monatomic gas to the speed of light c. Such measurements, carried out with high accuracy, could determine the universal gas constant R and the thermodynamic temperature T with unprecedented accuracy. The realization of these possibilities can be greatly facilitated by judicious choices of cavity geometry and resonance modes. The present state of the art suggests that the ratio u/c can be measured to parts per million accuracy using cavities whose geometry is known only to parts per thousand. Recent experimental and theoretical results will be presented.
Effect of nonlinear frequency dependence of seabottom sound attenuation on low-frequency acoustic response in shallow water
Authors: Zhou Ji-xun , Rogers Peter
Published: October 2005

In recent years several papers have been written on the existence and nature of the so-called “optimum frequency” (Fopt) for acoustic propagation in shallow water. These papers characterize the effects of various basic physical and environmental parameters that influence Fopt (such as water depth, sound velocity profile, sediment type, the depth and separation of the source-receiver pair, sediment sound-speed gradient, shear wave couple loss, etc.), but do not consider the frequency and the depth dependence of seabottom sound attenuation. In this paper, some experimental data on low-frequency response (30–2000 Hz) in shallow water are presented. The interesting result is that over the frequency range where Fopt should occur according to the existing theories, no apparent optimum frequency is observed. In order to explain these experimental results, this paper uses a normal mode computer program to examine the frequency dependence of sound propagation for various canonical models of seabottom structure in shallow-water regions (including thin top surface transition layer with strong positive sound-speed gradient of 1000 s−1 and negative attenuation gradient) allowing for the possibility that attenuation in the sediments may have a nonlinear frequency dependence. The results show that the experimental low-frequency responses, including the disappearance of the optimum frequency, are consistent with the earlier results of J. X. Zhou [J. Acoust. Soc. Am. 78, 1003–1009 (1985)], i.e., that bottom attenuation in the low-frequency range has frequency power law of fn, with values of n ranging from 1.5 to 2.0, although the results could also be explained to some degree by a seabed top transition layer.
An investigation of the measurement sensitivities of acoustic remote profiling to bottom type and frequency
Authors: Bailey R. S. , Henderson T. L. , Maxwell J. W. , Tschoepe E. A.
Published: October 2005

A method for remote geometric profiling of rough interfaces, which makes use of angular information obtained with a broadband monopulse sonar operating at low grazing angles, has been previously demonstrated in the analysis of backscattering data taken in lake and ocean environments [J. W. Maxwell and T. L Henderson, J. Acoust. Soc. Am. Suppl. 1 78, S72 (1985)]. Since this method is sensitive to multiple scattering from different scattering centers and interference such as glint, sound penetration will produce false variations in the estimated profile. Analysis of data has often revealed such variations to exceed predicted values, frequently exaggerating the bottom irregularities to a marked degree. A remote profiling system was developed to conduct laboratory experiments to simulate remote profiling of the ocean bottom. Water tank experiments were conducted at selected frequencies from 30 to 100 Khz and pulse widths from 0.1 to 1.0 ms. The bottom types simulated consist of a sandy bottom, gravel over sand, gravel over a hard bottom, and a rough hard bottom. The variation of the profiles was analyzed with respect to the presumed degree of penetration of the sound into the bottom. As expected, the profiles were markedly smoother when frequency diversity was exploited.
Propagator matrix method for calculation of normal modes in a stratified ocean overlying inhomogeneous anisotropic porous beds
Authors: Badiey Mohsen
Published: October 2005

A practical algorithm for the calculation of acoustic normal modes at excitation frequencies of 50 to 5000 Hz in a shallow stratified ocean overlying a transverse isotropic poroelastic sediment bed is developed. The Biot-Willis stiffness matrix which describes poroelastic anisotropy in terms of physical properties of sediments is used to model the bed. The propagator matrix method is used to solve the differential equations for the motion stress vectors in both layered sediment and water. The method of impedance matching is used to obtain the eigenvalues of the system numerically. Using measured in-situ properties of sediment (presented separately in this meeting), the effect of sediment anisotropy and inhomogeniety on acoustic wave propagation is studied for shallow water propagation at the Great Bahama Bank. [The work was sponsored by ONR Codes 425UA.]
Laboratory measurements of selected geo-acoustic properties of carbonate sediments at the Great Bahama Bank
Authors: Yamamoto Tokuo , Bennett Richard H.
Published: October 2005

The complex shear modulus of various carbonate sediments taken from the Great Bahama Bank was measured mechanically at very low shear strain amplitudes of the order of 10−7 using a high-precision torsional resonant column apparatus. Permeability and porosity of the sediments were also measured. The measurements were made under simulated in-situ stress conditions. The data from the laboratory measurements were compared with those from the in-situ measurements which are presented separately in this meeting. Finally, the depth profiles of the velocities and the attenuation of the compressional waves and the shear waves were delivered as a function of frequency ranging from 50–5000 Hz. Our velocity and attenuation profiles were compared with the profiles recommended by E. Hamilton. [The work was sponsored by ONR Codes 425UA and 425GG.]
Clinical, medical, and behvioral research needs to foster improved hearing conservation
Authors: Alberti P. W.
Published: October 2005

Outstanding medical problems include the identification of noise susceptible individuals; development of new medical management for acute noise exposure, the relationship of tinnitus to noise type and level, and continuing study of the relationship between noise and other diseases; detailed studies of the interaction of peripheral and central lesions, particularly the central aging effects, is also required. What is the relationship of noise exposure and hearing loss on speech? Definition of appropriate presbycusis corrections are required which are related to cutoff levels for compensation. The effect of differing noise exposures and, in particular, intermittency of exposure is not clear. What is the effect of currently popular eccentric work weeks with 3 × 12-h shifts and 4 days off?. Is there need to control overtime from total exposure in noise industries? How important is sociocusis? What are the long-term outcomes of the hearing conservation programs? What is the safety risk associated with hearing protectors? What stratagem of hearing conservation should be used on an already hearing-impaired work force? The problems of monitoring hearing protectors and the need to service hearing protectors regularly will be stressed.
Ultrasonic assessment of burn injury
Authors: Cantrell John H. , Yost William T.
Published: October 2005

The quantitative assessment of burn depth for victims of severe thermal injury is one of the most challenging problems facing the burn surgeon today. We have developed a high-resolution, ultrasonic system that is capable of measuring the depth of skin burns that agrees to within 5% of the values obtained independently from histological sectioning. Such accuracy is well within surgical requirements. Ultrasonic measurements of the time-temperature dependence of cutaneous burn depth together with a theoretical model of the burning process reveals collagen denaturation to be the progenitor of thermal necrosis. This finding provides an objective basis upon which to diagnose burn injury and establishes the ultrasonic technique as a viable alternative to subjective diagnostic methodologies currently in use.
The cause of the focus artifact in clinical sonography
Authors: LaFollette Paul S. , Ziskin Marvin C.
Published: October 2005

The focus artifact is commonly observed spurious echo enhancement that is seen as a linear band in clinical sonograms. It occurs at a distance from the transducer equaling the focal length, and although believed to be related to a focusing effect of the sound beam, its production has never been adequately explained. The notion that focusing concentrates the energy producing a more intense reflection in the focal region, although correct, is an inadequate explanation because the number of reflectors irradiated is reduced proportionally to the intensity increase to those receiving the ultrasound. If this was all there is to the focusing effect, the transducer would record the same amount of sound in either the focused or unfocused case. In order to provide an adequate explanation, a mathematical model has been developed that predicts the geometric and intensity distortions that occur in a sonogram produced by a clinical instrument when the sound beam passes through a converging lens. By considering a focusing transducer as a plane transducer with a converging lens placed in contact with its surface, this model does show a marked relative echo enhancement occurring at a distance from the lens equaling the focal length. In addition to the theoretical analysis and prediction, this artifactual echo enhancement has been demonstrated in several test objects in the laboratory and also in clinical sonograms.
Ultrasonic assessment of skin and wound with the scanning laser acoustic microscope
Authors: Steiger D. L. , Olerud J. E. , Riederer-Henderson M. A. , O'Brien W. D.
Published: October 2005

The ultrasonic attenuation coefficient and speed of canine wound tissue and adjacent skin have been studied at wound ages between 7 and 50 days with the scanning laser acoustic microscope at 100 MHz. Water, total collagen, and acid soluble collagen contents were determined for both wound and skin. Attenuation coefficient and speed were consistently greater for the skin than for the wound. Water content was generally higher and total collagen was generally lower in the wound tissue. Total collagen increased in the wound and its difference between wound and skin decreased with maturation. Attenuation coefficient (A in dB/mm) and speed (c in m/s) were highly significant with both total collagen and water. Mathematically, via least-squares analysis, A = 1.67C + 6.3, A = − 1.77W + 154, c = 6.5C + 1460, and c = − 5.2W + 1923, where C is the total collagen (as percentage on a wet weight basis) and W is the percent water. [This work supported by NIH AM 21557 and CA 36029.]
Measurement of low-intensity highly focused ultrasound
Authors: Myers George H. , Lewin Peter A. , Schafer Mark E.
Published: October 2005

The requirements for precise determination of acoustic output for different types of medical diagnostic equipment have made it important to develop methods of measuring ultrasonic field parameters at high megahertz range of frequencies. More specifically, of particular interest here is the measurement of pulsed beams of small focal diameters (of the order of a wavelength), generated by the low total power output devices. These low power levels are in general on the order of 50 μW, which is below the sensitivity of current acoustic power measurements methods including radiation force balances and calorimeters. While the miniature wideband polymer hydrophones have the requisite voltage sensitivity and bandwidth to correctly record the pressure waveforms, their finite dimensions, typically 0.5 to 1.0 mm in diameter, lead to spatial averaging effects. To overcome this problem, a technique has been developed, and is now being tested which permits hydrophones to be used in these applications. The measurement procedure is based on the fact that: (a) the entire beam is intercepted by the hydrophone and, (b) the beam profile can be accurately determined by pulse-echo techniques. The pressure waveform is recorded from a calibrated hydrophone of known effective area, located at the focus of the beam. The total force on the hydrophone is determined by numerically integrating the beam profile. The peak pressure, intensity, and total transmitted power can then be directly determined. Experimental results will be presented and both the advantages and limitations of the proposed measurement procedure will be discussed.
The use of frequency weighting in multifrequency holography
Authors: Teo T. J. , Reid J. M.
Published: October 2005

Backpropagating an acoustical field that is measured on a planar surface using angular spectrum decomposition [J. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968)] can be used to reconstruct a source region or a scattering region. The reconstruction algorithm is inherently monochromatic and hence the range resolution is typically worse than the lateral resolution. In diffraction tomography, the same backpropagation algorithm is used and the summation over views is used to improve the overall resolutions [A. Devaney, Ultrason. Imag. 4, 336–350 (1982)]. In the case of B-scan imaging, the reverse is true. The use of short pulse provides a good range resolution while the lateral resolution is limited by the beamwidth. It is therefore advantageous to combine the wideband approach with the backpropagation. The use of multiple frequencies in backpropagating the acoustical field has shown to improve the range roolution [e.g., T. J. Teo and J. M. Reid, Acoust. Imag. 14, 143–153 (1985)]. The two techniques can therefore be combined by suitably weighting the frequency distribution with the amplitude and phase spectra of a pulse. We will also show the effect of pulse shape on the image reconstructed and range resolution in particular.
Application of the sinc basis moment method to the reconstruction of infinite circular cylinders
Authors: Cavicchi T. J. , Johnson S. A. , O'Brian W. D.
Published: October 2005

A solution to the ultrasonic scattering and inverse scattering problem has been obtained by solving the exact inhomogeneous Helmholtz wave equation via the sinc basis moment method. In this numerical study, the algorithm of Johnson and Tracy [Ultrason. Imag. 5, 361–375 (1983)] has been applied to the reconstruction of an infinite circular cylinder which is subject to an incident cylindrical ultrasonic wave and is surrounded by a homogeneous coupling medium. For weak scatterers, successful reconstructions have been obtained using the known exact solution for the scattered field in the case of a circular object function as the input data for the algorithm. Five percent noise does not affect performance, nor does transmitter and receiver distance to the object for a loss-less coupling medium. Also for weak scatterers and exact field data, the reconstruction quality improves for cylinders when the grid size increases because the discretized shape becomes more nearly circular. Use of either the discrete scattered field equations or the exact Bessel function series solution yielded identical results, verifying the validity of the sinc function expansions. [This work is supported by CA 09067.]
A method to estimate fluctuations in criterion and sensitivity
Authors: Hanna Thomas E.
Published: October 2005

The theory of signal detection (TSD) typically assumes variable sensory information and a fixed criterion. A fixed criterion is assumed because of our inability to distinguish sensory variance from criterion variance based only on a summary of hit, false alarm, miss, and correct rejection percentages. The present paper develops a model which distinguishes sources of variance by considering two-trial response patterns. The model assumes that criterion and sensitivity are normally distributed over the course of an experiment but are relatively constant over successive trials, i.e., they vary slowly. By computing statistics over pairs of successive trials it is possible to estimate the proportion of variance that is attributable to fluctuations in criterion and that is attributable to fluctuations in sensitivity.
Uncertainty and response time in identifying nonspeech sounds
Authors: Ballas James A. , Sliwinski Martin J. , Harding John P.
Published: October 2005

The identification of short duration (< 500 ms) sounds taken from sound effects records was studied to determine if measures of causal uncertainty would be related to identification time. Twenty-five sounds were randomly presented to listeners who were instructed to respond as soon as they had a reasonable guess about the cause of the sound. Identification times averaged across listeners ranged from 921 ms for a doorbell to 5982 ms for a monkey cry. All identifications for a sound were combined, sorted for similar responses, and used to compute the uncertainty metric from information theory. For the sounds used, the uncertainty metric was significantly correlated with the log of the average response time (r = + 0.59). Correlations for individual subjects ranged from + 0.15 to + 0.71.
The effect of amplitude and spectral uncertainty on masking produced by small numbers of sinusoids
Authors: Neff Donna L. , Callaghan Brian P.
Published: October 2005

Threshold for a 1000-Hz sinusoidal signal in the presence of multicomponent maskers was measured for four normal-hearing listeners. Masker and signal were 200 ms, presented simultaneously. Maskers were composed of 2 to 200 sinusoids whose frequencies were drawn at random from a range of 300–3000 Hz, excluding the signal frequency. Component frequencies, amplitudes, or both were either fixed or randomized across the two intervals of the 2AFC trials; new frequencies were drawn for each trial. For maskers with more than ten components, there was little effect of randomizing either component frequency or amplitude. For maskers with ten or fewer components, randomizing frequency across intervals produced large amounts of masking but there was little effect of randomizing amplitude. Similar results were obtained when components were eliminated from the critical band around the signal frequency. Under some conditions, listeners apparently cannot use a single-filter detection strategy even when it is advantangeous to do so. [Work supported by NIH.]
“Confusion effects” in simultaneous masking
Authors: Mott John B. , Feth Lawrence L.
Published: October 2005

A “confusion effect,” the inability to discriminate the probe from the masker in certain stimulus configurations, has been well-documented in forward masking [e.g., D. Neff, J. Acoust. Soc. Am. 78, 1966–1976 (1985)]. Similar effects are reported for simultaneous masking. Bimodal thresholds in simultaneous masking are observed when the masker envelope fluctuates and the probe duration is shorter than the mean interval between envelope peaks. The magnitude of the confusion effect, as measured by the difference between threshold estimates for a given masker and probe combination, is similar in simultaneous and forward masking. However, while confusion effects in forward masking are typically observed when the probe is near the masker frequency, bimodal thresholds in simultaneous masking are observed across a wider frequency region. This result does not favor a confusion hypothesis, since the spectral difference between masker and probe should reduce or eliminate confusion effects. [Work supported by NINCDS grant ♯T-32-NS07257.]