bluuebunny/crossref_metadata_2025 huggingface dataset:
Legal issues arising under OSHA's noise standard
Authors: Moran Robert D.
Published: October 2005

At what level, if any, is noise a “harmful” physical agent subject to regulation under § 6(b) (5)? Only § 6(b) (5) standards can include requirements for noise monitoring and audiometric testing. Is the present noise standard such a regulation? Are employees exposed to hazard when they are wearing devices which attenuate surrounding noise to within permissible levels? Can OSHA impose engineering control requirements in such cases? Is a single 8-h exposure to excessive noise legally sufficient to trigger the standard's requirements? Can any part of an employer's obligation be based upon employee hearing loss not caused by that employer's noncompliance? Can OSHA impose any requirement on the basis of 80 and 85 dB noise levels which are admittedly well below the permissible 90 dB limit? Finally, is the imposition of administrative and engineering requirements to control workplace noise “reasonably necessary or appropriate” when hearing protectors are available which will achieve an equal or greater attenuation in such noise? No OSHA requirement is legally permissible unless it is reasonably necessary or appropriate to achieve a safe work environment.
Pitch-relevant patterns of discharge synchronization to two-component signals in cochlear nerve fibers of the cat
Authors: Greenberg Steven , Geisler C. Daniel , Deng L.
Published: October 2005

Over 40 years ago, Jan Schouten proposed that the pitch of complex tones is derived from the activity of peripheral auditory neurons synchronized to the temporal fine structure of the cochlea-filtered signal [J. F. Schouten, Proc. K. Ned. Akad. Wet. 43, 991–999 (1940)]. The present study sought to evaluate Schouten's model by recording the responses of low-frequency cochlear fibers from the cat during presentation of two (iso-amplitude)-component signals which, in human listeners, produce a reliable sensation of low pitch [G. F. Smoorenburg. J. Acoust. Soc. Am. 48, 924–942 (1970)]. Signal frequencies, f1 and f2, arithmetically centered around the fiber's characteristic frequency (CF), conformed to the equations (1) f1 = [2n/(2n + 1)] CF; (2) f2 = [(2n + 2)/(2n + 1)] CF, where n = f1/(f2 − f2) and assumed values between 2.5 and 8.5. A large proportion of cochlear fibers synchronize to both frequency components in approximately equal measure (thus implying synchronization to a half-wave recitified version of the signal's temporal fine structure), even when the signal components are as much as half an octave apart. These data are consistent with the basic tenor (if not the details) of the temporal fine structure model. However, it remains uncertain whether such pitch-relevant information is utilized by higher auditory centers. [Research financially supported by NIH.]
Characterization of tongue shape during normal speech
Authors: Morrish Kathleen A. , Stone Maureen , Shawker Thomas H. , Sonies Barbara C.
Published: October 2005

Averaged tongue shapes and polynomial equations were computed for five phonemes in order to determine aspects of tongue curve which distinguish between phonemes. Five repetitions of each of the phonemes /i/, /u/, /o/, /æ/, and /ɑ/ were produced by a normal volunteer using the carrier phrase “I can say /dVd/ again.” An ultrasound sector scanner was used to obtain midsagittal pictures of the posterior section of the tongue from vertical to 85° back into the throat. The pictures were digitized, and the resulting points were used to generate average tongue shapes and average quadratic and cubic fits for each phoneme. While both techniques provide information which allows the researcher to distinguish between the five phonemes used, only the averaged tongue shapes adequately reflect certain details of tongue shape.
Generalized parabolic wave equation and field-moment equations for random media having spatial variation of mean sound speed
Authors: Hill Reginald J.
Published: October 2005

The wave equation for propagation of sound waves through random oceanic inhomogeneities is expressed in a special coordinate system that follows the ray path of the deterministic wave that would propagate in the absence of randomness. The ratio of the full wave field in the presence of random inhomogeneities to the deterministic wave field is shown to satisfy the parabolic wave equation with acoustic wavelength depending on position along the ray. This approximation requires that the local sound speed be only slightly perturbed from its local deterministic value, although it may be very much different from the sound speed at a distant point on the deterministic ray. No matter how tortuous the path of the deterministic field, this parabolic equation holds provided that the angles between the rays of the full field and rays of the deterministic field are small. The equations for moments of the field (mean field, mutual coherence function, fourth moment) have a form very similar to the case of uniform mean sound speed. The numerical solution of these random-medium propagation equations is conceptually simple.
Critical band analysis of avian vocalizations
Authors: Dooling Robert J. , Bunnell H. Timothy , Clark Christopher
Published: October 2005

In searching for the basis of information encoding in avian vocalizations, conventional analysis techniques fail to take into account what is known about peripheral auditory processing in the avian ear. A spectral analysis of the entire vocal repertoire of the budgerigar is described based on the threshold of hearing and acoustic transformations derived from psychoacoustic studies of masking in this species. Some vocalizations of the budgerigar are matched to the region of best absolute sensitivity and smallest critical bandwidth in this species while others are not. The unusual shape of the critical band function for the budgerigar provides a considerably different view of the spectral differences normally observed between categories of vocalizations and between the vocalizations of other species. These results will be discussed in relation to the probable function of budgerigar vocalizations and the acoustic cues facilitating individual recognition. [Work supported by NICHHD and NINCDS.]
Silator: A small volume resonator
Authors: Laudien E. , Bschorr O.
Published: October 2005

The paper presents an experimental and analytical study of a newly developed small volume resonator element—called Silator—which can be used for sound attenuation wherever a free air passage is required. A Silator consists of two metal diaphragms—shaped like flat calottes—which are joined together to form a single element. The enclosed space is evacuated. The diaphragm represents a spring-mass system which allows very low spring constants due to its nonlinear spring characteristic. Consequently, the resonance frequency of the system depends only on the shape of the Silator and not on its volume. The acoustic impedance becomes a minimum at resonance and can—depending on the amount of Silator damping—reach values which are lower than the characteristic impedance of air. An array of properly spaced Silators with preselected resonance frequencies constitutes an acoustic screen which nevertheless allows free airflow through it. Presented experimental data of Silators in intake and exhaust systems shows that noise reductions of more than 10 dB are obtainable not only for discrete frequencies but also for broadband noise.
Vowel-to-vowel coarticulation in English and Japanese
Authors: Magen Harriet
Published: October 2005

Vowel-to-vowel coarticulation was investigated by analysis of formant trajectories in VCV utterances. Two sets of English utterances were analyzed, one with initial stress and one with final stress. The VCV utterances consisted of all combinations of the labial consonants /b/, /p/, and /m/ and the vowels /a/ and /i/. Preliminary acoustic analyses indicate: (i) There are substantial vowel-to-vowel coarticulatory effects in both English stress patterns not only in transitions but also in steady state portions, and (ii) Stressed vowels in English are more resistant to coarticulation than are unstressed vowels. The effects of transconsonantal vowel are present for the duration of an unstressed vowel, but are small or absent at the beginning of a stressed VC and the end of a stressed CV. A pilot study on Japanese VCV utterances with low pitch accent on initial and final vowels suggests that the magnitude of coarticulation is greater in Japanese than in English throughout the duration of the vowel. [Work supported by NICHD.]
Detection of high-frequency spectral notches as a function of level
Authors: Alves-Pinto Ana , Lopez-Poveda Enrique A.
Published: October 2005

High-frequency spectral notches are important cues for sound localization. Our ability to detect them must depend on their representation as auditory nerve (AN) rate profiles. Because of the low threshold and the narrow dynamic range of most AN fibers, these rate profiles deteriorate at high levels. The system may compensate by using onset rate profiles whose dynamic range is wider, or by using low-spontaneous-rate fibers, whose threshold is higher. To test these hypotheses, the threshold notch depth necessary to discriminate between a flat spectrum broadband noise and a similar noise with a spectral notch centered at 8 kHz was measured at levels from 32 to 100 dB SPL. The importance of the onset rate-profile representation of the notch was estimated by varying the stimulus duration and its rise time. For a large proportion of listeners, threshold notch depth varied nonmonotonically with level, increasing for levels up to 70–80 dB SPL and decreasing thereafter. The nonmonotonic aspect of the function was independent of notch bandwidth and stimulus duration. Thresholds were independent of stimulus rise time but increased for the shorter noise bursts. Results are discussed in terms of the ability of the AN to convey spectral notch information at different levels.
Modeling elastic wave propagation in kidney stones with application to shock wave lithotripsy
Authors: Cleveland Robin O. , Sapozhnikov Oleg A.
Published: October 2005

A time-domain finite-difference solution to the equations of linear elasticity was used to model the propagation of lithotripsy waves in kidney stones. The model was used to determine the loading on the stone (principal stresses and strains and maximum shear stresses and strains) due to the impact of lithotripsy shock waves. The simulations show that the peak loading induced in kidney stones is generated by constructive interference from shear waves launched from the outer edge of the stone with other waves in the stone. Notably the shear wave induced loads were significantly larger than the loads generated by the classic Hopkinson or spall effect. For simulations where the diameter of the focal spot of the lithotripter was smaller than that of the stone the loading decreased by more than 50%. The constructive interference was also sensitive to shock rise time and it was found that the peak tensile stress reduced by 30% as rise time increased from 25to150ns. These results demonstrate that shear waves likely play a critical role in stone comminution and that lithotripters with large focal widths and short rise times should be effective at generating high stresses inside kidney stones.
Source visualization by using statistically optimized near-field acoustical holography in cylindrical coordinates
Authors: Cho Yong Thung , Bolton J. Stuart , Hald Jørgen
Published: October 2005

Nearfield acoustical holography (NAH) is a useful tool for visualizing noise sources. However, to avoid spatial Fourier transform-related truncation effects, the measurement, or hologram, surface must extend beyond the source to a region where the sound pressure drops to a level significantly lower than the peak level within the measurement aperture. Statistically optimized nearfield acoustical holography (SONAH), first derived by Steiner and Hald in planar geometry, is based on a formulation similar to that of NAH. However, in SONAH, surface-to-surface projection of the sound field is performed by using a transfer matrix defined in such a way that all propagating waves and a weighted set of evanescent waves are projected with optimal average accuracy: i.e., no spatial Fourier transforms are performed. Thus the requirement that the measurement surface be extended is eliminated without compromising the accuracy of the procedure. In the present work, SONAH was re-formulated in cylindrical coordinates and was applied to the measurement of the sound field radiated by a refrigeration compressor. It was found that it is possible to visualize source regions accurately by using SONAH while using fewer measurement positions than would be required to achieve a similar level of accuracy when using conventional NAH procedures.
Pattern Playback revisited: Unvoiced stop consonant perception
Authors: Kiefte Michael , Kluender Keith R.
Published: October 2005

Among the most influential publications in speech perception is Liberman, Delattre, and Cooper’s [Am. J. Phys. 65, 497–516 (1952)] report on the identification of synthetic, voiceless stops generated by the Pattern Playback. Their map of stop consonant identification shows a highly complex relationship between acoustics and perception. This complex mapping poses a challenge to many classes of relatively simple pattern recognition models which are unable to capture the original finding of Liberman et al. that identification of ∕k∕ was bimodal for bursts preceding front vowels but otherwise unimodal. A replication of this experiment was conducted in an attempt to reproduce these identification patterns using a simulation of the Pattern Playback device. Examination of spectrographic data from stimuli generated by the Pattern Playback revealed additional spectral peaks that are consistent with harmonic distortion characteristic of tube amplifiers of that era. Only when harmonic distortion was introduced did bimodal ∕k∕ responses in front-vowel context emerge. The acoustic consequence of this distortion is to add, e.g., a high-frequency peak to midfrequency bursts or a midfrequency peak to a low-frequency burst. This likely resulted in additional ∕k∕ responses when the second peak approximated the second formant of front vowels. Although these results do not challenge the main observations made by Liberman et al. that perception of stop bursts is context dependent, they do show that the mapping from acoustics to perception is much less complex without these additional distortion products.
Estimating signal and noise using a random array
Authors: Hinich Melvin J.
Published: October 2005

This paper presents approximations for the rms error of the maximum likelihood estimator of the direction of a plane wave incident on a random array. The sensor locations are assumed to be realizations of independent, identically distributed random vectors. The second part of the paper presents an asymptotically unbiased estimator of the noise wavenumber spectrum from random array data.
Experimental investigation of the response of gas-filled micropores to ultrasound
Authors: Miller Douglas L.
Published: October 2005

Hydrophobic membranes with gas-trapping micropores have been used in ultrasonic bioeffects experiments to determine the efficacy of the cavitation mechanism at low intensities. Membranes were tested with circular pores of about 2.5 to 5.4 μm in diameter and these pores trapped gas when the membranes were immersed in water such that the resulting bubbles were stable against diffusion. Only a few pores remain completely filled with gas upon immersion, however, and the distribution in partial filling apparently results in a distribution of resonance frequencies for the bubbles in a membrane, even when the pores are essentially all identical in size.
Transient voltage across axisymmetrically loaded piezoelectric disks with electroded faces
Authors: Bogy D. B. , Miu D. K-K.
Published: October 2005

A recently derived approximate two-dimensional theory is used to predict the transient output voltage generated in circular PZT disks after sudden release from a static deformation caused by axisymmetric loads applied to the faces. Three specific loading cases are considered (a) a concentrated central normal force on one face with an opposing peripheral ring load on the other, (b) opposing uniform normal pressure, and (c) opposing central normal forces. The theoretical power spectra and time histories are compared with experimental observations for the same loading cases, and they are found to be in good overall agreement. It is found in all loading cases considered that the output voltage is produced by the lowest longitudinal thickness mode of motion together with the first few (up to 12) longitudinal radial modes. The thickness mode contribution decays out after 5–15 μs so that the remainder of the signal is produced by radial modes. The results presented here should contribute to a better understanding of electromechanical transducers made with piezoelectric plates.
Detection threshold microstructure and its effect on temporal integration data
Authors: Cohen Marion F.
Published: October 2005

Auditory detection thresholds were measured at several preselected frequencies using an adaptive 2IFC procedure. Results confirm the existence of shifts in detection threshold ranging from 2 to 14 dB with quite small changes in signal frequency. There does not appear to be a uniform pattern associated with the microstructure of the detection threshold curve. An additional experiment was performed to determine the effect of signal duration on detection threshold microstructure. Results indicate that the temporal integration function is considerably steeper for more sensitive frequencies (3.7 dB/doubling of duration), than for less sensitive frequencies (1.7 dB/doubling). This probably is not due to differences in processing as much as it is to the effect of the energy spread associated with decreasing signal duration.
Temporal order identification: Some parameter dependencies
Authors: Pastore Richard E. , Harris Laura B. , Kaplan Jody K.
Published: October 2005

Temporal order identification thresholds (TOT) for auditory stimuli have long been believed to be independent of the parameters of the stimuli as long as the judgment of order is (apparently) based directly upon the temporal difference rather than modality-specific stimulus interactions associated with the temporal difference. We have found that TOT is a direct function of stimulus duration and, at least for longer rise times, is also a function of the rise time of the stimuli. Finally, adding a new tone to the end of the stimulus complex alters TOT only for short duration stimulus complexes. The relationship between TOT and the perception of speech stimuli contrasted in initial onset characteristics is discussed.
Anticipatory labial coarticulation: Experimental, biological, and linguistic variables
Authors: Lubker James , Gay Thomas
Published: October 2005

The research reported here represents an attempt to resolve the differences between two views of anticipatory labial coarticulation. One of these views contends that a speaker begins labial movement toward a rounded vowel in direct relation to the amount of time available, while the other view posits an onset of movement that is temporally locked to the rounded vowel. Electromyographic signals were sampled from four muscles associated with labial movement while, simultaneously, movements of the upper lip in the anterior–posterior and vertical dimensions were recorded. Four native speakers of American English and five native speakers of Swedish served as subjects. Results suggested that (1) there are a number of purely biological and experimental variables which can intrude upon research of this type, and (2) there are also language-specific differences in the production of rounded vowels which suggest that Swedish and American English speakers have learned different motor-programming goals. This second observation is discussed in terms of acoustic/perceptual needs of the speakers of a language.
Ducted propagation of Concorde-generated shock waves
Authors: Weber Mark E. , Donn William L.
Published: October 2005

Measurements with an array of low-frequency microphones are compared to ray calculations, describing the long range propagation of acoustic energy from the shock cone of the Concorde SST. This energy is ducted between the surface and the strong sound velocity gradient of the upper stratosphere. The measured pressure signatures are composed of one to five distinct wave groups arriving over a period of minutes; the number and sequence of arrivals is different for the Dulles-bound and JFK-bound airplanes. With respect to arrival time and azimuth of phase propagation, we find close correspondence between the highest amplitude wave groups and the refracted arrival predicted by ray calculations. Subsidiary wave groups apparently result from the diffracted ’’ground’’ wave and from volume scattering of acoustic energy into shadow zones.
Drive point impedance of an infinite orthotropic plate under tension
Authors: Busch-Vishniac I. J.
Published: October 2005

In this paper an expression is derived for the drive point impedance of an infinite plate under tension. It is shown that at high frequencies the bending behavior is dominant, and at low frequencies the membrane behavior is dominant. In general an orthotropic plate under tension behaves like a resistance and stiffness combined in parallel.
The case of the missing 6 dB
Authors: Rudmose Wayne
Published: October 2005

In 1933 data were reported which indicated that thresholds of hearing for low frequencies apparently depended upon whether the source was an earphone (MAP) or a loudspeaker (MAF). A decade or so later the same type of discrepancy appeared when loudness balances were made at 100 Hz between an earphone source and a loudspeaker source. In both cases approximately 6 dB more sound pressure level at the eardrum was required when the earphone was the source than when the loudspeaker was the source. Later research added credence to this paradox, namely, the ear should act as a pressure operated device, and there should be no difference between MAP and MAF; yet a difference seemed to exist. Research reported in abstract form and orally by the author in 1962 and 1963 showed that (a) the difference at threshold was due to physiological noise generated in the ear canal by the earphone–cushion–head combination (and could be eliminated with a special earphone-coupling system), and (b) the suprathreshold differences obtained with loudness balancing were due to a number of subtle procedural and experimental techniques (techniques which could be modified so as to avoid all of the problems of past experimenters). This research is reported here for the first time in full detail. A total of 15 different subjects participated in eight experimental comparisons using three to nine subjects each, with sufficient replications so that most subjects’ MAF–MAP and/or loudness differences were determined within 1 or 2 dB at the 95% confidence level. It was often possible to replicate previous results using previous methods, but with the modified methods reported here the average difference across experiments was less than 0.2 dB, and no subject in any experiment exhibited more than a 1.8-dB difference averaged across trials. The case of the missing 6 dB should be considered closed.
Speech intelligibility in noise: Effects of fluency and hearing protector type
Authors: Abel Sharon M. , Alberti Peter W. , Haythornthwaite Caroline , Riko Krista
Published: October 2005

This research investigated the effect of ear protectors on the intelligibility of speech in noise. Listeners with normal hearing, high-frequency, and flat loss were tested. Half the subjects in each group were fluent in English and half poorly conversant. Taped lists of 25 words were presented free field under conditions defined by the speech-to-noise ratio, spectrum of noise background, and presence of ear protection. The results showed that intelligibility decreased with speech-to-noise ratio and was poorer in crowd noise than in white noise. The protector had no effect for the normal listener, but caused a substantial decrement in those with impairment. In all groups nonfluency contributed an additional loss of 10% to 20%. Significant differences in performance were noted for different muff and plug types.
Distributions of volume scattering observed with an 87.5-kHz sonar
Authors: Greenblatt Paul
Published: October 2005

Horizontal spatial and temporal variations of the volume backscattering coefficient were measured with a horizontally aimed 87.5-kHz sonar operating at 87-m depth. Temporal variations between 2 min and 10 h and spatial variations between 17 and 400 m could be resolved with this data set. The wavenumber spectra of the acoustic backscattering coefficient were red, indicating that large scale variations accounted for more of the horizontal variability than smaller scales. Frequency spectra were red at periods greater than 1 h, irregular at periods between 6 min and 1 h, and white at periods less than 6 min. Elevated spectral levels between 1 to 10 c/h are probably due to vertically stratified organisms being lifted into and out of the sonar beam by internal waves. The shape of day spectra were similar to night spectra (both wavenumber and frequency), but total variance of the volume scattering coefficient was greater at night. One can interpret this to mean that the dimensions of scatterer patchiness did not change from night to day but the intensity of variations increased markedly at night. Mean scattering strength increased at sunset and decreased at sunrise due to the diurnal migration of plankton and nekton. Upward migration of scatterers was different than downward migration in two ways. First, the upward migration took only between 12–20 min to complete while the downward migration lasted about 50 min. Second, a scattering stength ’’overshoot’’ (i.e., a local maximum 2–4 dB above ambient night scattering levels) was observed only during the upward migration. The scattering strength ’’overshoot’’ probably occurred because migrating midwater fish and squid are most concentrated during upward migration. These animals either disperse after finishing their migration or descended below the sonar within 12–20 min after reaching 90 m.
Response of a rectangular parallelepiped to a simulated acoustic emission burst
Authors: Hill Eric v. K. , Egle Davis M.
Published: October 2005

The forced vibrational response of the rectangular parallelepiped is of particular interest in the study of wave propagation in three-dimensional solids and especially in the characterization of acoustic emission sources. There has been considerable interest in studying source mechanisms in order to predict, and perhaps eventually control, flaw growth in structural materials. The acoustic emission source waves generated by flaw growth are thought to be pulselike functions of stress (force) which are produced by the step displacements associated with material yielding. Much of this type of emission in solids is produced internally and can, therefore, be modeled as a body force phenomenon; as such, this paper presents an exact, normal mode solution for the response of a rectangular parallelepiped to an impulsive body force. The numerical results prior to any reflections from the boundaries show agreement with the infinite space solution.
Auditory filter shapes in forward masking as a function of level
Authors: Glasberg Brian R. , Moore Brian C. J.
Published: October 2005

Thresholds were measured for 1-kHz, 5-ms sinusoidal signals following noise maskers with a spectral notch of variable width centered at 1 kHz. In one set of conditions threshold was measured as a function of notch width for three fixed noise levels: 30, 40, and 50 dB SPL/Hz. In order to compensate for the decay of masking, each signal threshold was transformed to the level of a flat-spectrum noise which would give the same masking effect. In a second set of conditions the noise level required for threshold was measured as a function of notch width for three fixed signal levels, separated by 5 dB. The auditory filters derived from the data were essentially the same for the two sets of conditions, and did not vary significantly with masker or signal level. The filters had a mean 3-dB bandwidth of 90 Hz.
Modal coupling in the vibration of fluid-loaded cylindrical shells
Authors: Stepanishen Peter R.
Published: October 2005

An approach is presented to evaluate the pressure field and vibratory response of a finite fluid-loaded cylindrical shell with infinite rigid extensions which are connected to the shell. The approach combines a generalized Fourier series or in vacuo eigenfunction expansion of the velocity field of the shell with a Green’s function and integral equation representation of the acoustic loading on the shell. Although modes with different circumferential wavenumbers are decoupled, all modes with identical circumferential wavenumbers are coupled via the fluid. The algebraic equations which account for this coupling include both shell impedances and acoustic impedances which are mode dependent. General integral expressions are presented for the acoustic impedances which include both self radiation and interaction impedances. In order to illustrate the general characteristics of these acoustic impedances, the impedances are investigated for a particular set of eigenfunctions. Low-frequency and asymptotic expressions are presented for both the self and interaction impedances. Extensive numerical results are also presented to illustrate general characteristics of the self and interaction impedances as a function of mode shape and frequency.
Diffraction of sound by a noise barrier in the presence of atmospheric turbulence
Authors: Daigle G. A.
Published: October 2005

Although atmospheric turbulence influences many aspects of sound propagation outdoors, its effects have not previously been studied quantitatively when predicting the attenuation of sound by barriers. Traffic noise attenuated by a barrier alongside a highway has been measured with microphones positioned above an asphalt surface behind the barrier. The sound levels are analyzed and compared with certain aspects of diffraction theory to reveal discrepancies. To investigate these discrepancies, an idealized experiment was performed using a point source and a barrier erected on a flat asphalt surface. Because important discrepancies between theories were found, especially at shorter distances from the barrier, these more precise measurements are first compared with various diffraction theories. When subsequently compared with the diffraction theory that shows the best agreement with the measured points, another discrepancy in sound levels is observed that occurs at the higher frequencies. A calculation is described to estimate the amount of sound energy scattered by atmospheric turbulence above the barrier edge. The levels calculated from the sum of the scattered energy and the energy diffracted at the barrier edge show better agreement with the measurements than diffraction theory alone.
Effect of air cavity on the annular drum
Authors: Gottlieb H. P. W.
Published: October 2005

The effect of the compressibility of the entrapped air on the eigenfrequencies of vibration of the radially symmetric modes of an annular drum with an enclosed air cavity is computed. The frequencies become raised, with the fundamental being most affected, so that the ratios of frequencies of higher modes to first-mode frequency are decreased. The cavity air loading parameter may be utilized to improve still further the harmonicity of the radial modes of the vibrating annular membrane.
Extension of acoustic levitation to include the study of micron-size particles in a more compressible host liquid
Authors: Weiser Mary Ann H. , Apfel Robert E.
Published: October 2005

We discuss the development of a new technique for measuring the mechanical properties, namely density, compressibility, and sound velocity, of biological materials. The technique makes use of acoustic levitation, a phenomenon resulting from the balance of the gravitational force and a time averaged radiation pressure force acting on an object subjected to a sufficiently energetic sound field. The levitation technique is especially suited for studying biological materials, because it requires only very small samples (<1 μ1) and it employs a host liquid which acts as a container whose properties can be controlled to accommodate the material under consideration. Previous applications of acoustic levitation have been concerned with single millimeter diameter size droplets in a less compressible host liquid. Through this study, application of this technique has been extended to include levitation of samples consisting of a large number of micron-size particles in a more compressible host liquid. Application of the technique to this new class of materials required the development of a new apparatus, as well as greater attention to phenomena previously neglected in the theory describing the forces acting on a compressible sphere in a standing wave field. The technique was used to measure the compressibility of red blood cells in several different host environments. Results from the normal red blood cell compressibility measurements were in good agreement with those obtained using a more traditional technique.
Studies in reverberation. II. Scattering of sound by a cylindrical vortex embedded in a fluid at rest
Authors: Pekeris C. L.
Published: October 2005

A solution is obtained for the scattering of a plane sound wave incident normally on a cylinder of fluid rotating uniformly in a fluid at rest. In the long wave approximation, the amplitude of the scattered wave is proportional to the peripheral velocity of the cylinder and vanishes in the forward and backward directions as well as in directions normal to the direction of propagation of the incident wave.
Acoustic resonance frequencies of deformed spherical resonators
Authors: Mehl James B.
Published: October 2005

Spherical acoustic resonators are powerful tools for precision acoustic measurements. The frequencies of the radially symmetric modes of such resonators are determined mainly by the volume of the resonator: the first nonvanishing corrections to the resonance frequencies owing to imperfections in the boundary shape are of second order. In this work, arbitrary axisymmetric deformations are considered. Boundary shape perturbation theory is used to show that the first-order correction vanishes for constant-volume deformations. A general expression for the second-order frequency shift is derived. The results are applied to estimate the effect of machining errors in the construction of spherical resonators. With standard high-quality machining, it is possible to match the mean radii of two hemispheres used to fabricate a spherical resonator to within three parts in 104. Calculations have been carried out for the first seven radial modes for the case of a resonator assembled from hemispheres with mean diameters differing by this amount. The resonance frequencies do not differ from those of a perfect sphere with the same volume by more than 1.3 parts in 106. Other probable shape imperfections are likely to introduce even smaller errors.
On diffuse waves in solid media
Authors: Weaver Richard L.
Published: October 2005

A diffuse field in a solid medium is found to partition its energy between transverse and dilatational waves in a fraction R = 2(cd/ct)3. Energy flow rates from a diffuse field into a surface transducer from dilatational, transverse, and surface waves are compared. The relevance of the diffuse field concept for acoustic emission is discussed.
Shallow-water transmission loss prediction using the Biot sediment model
Authors: Beebe J. H. , McDaniel S. T. , Rubano L. A.
Published: October 2005

Experimental data and predicted propagation loss from three shallow-water test sites with highly varied sediments are compared for frequencies from 25 to 800 Hz. The predicted loss was obtained using normal-mode and adiabatic normal-mode models with the sediment absorption calculated using the theory of Biot. The theory predicted a linear variation of absorption with frequency for a site off Corpus Christi, Texas, having a mud bottom (the mean grain size was 6.37 phi). The absorption was predicted to vary as frequency raised to the 1.76 power for a site off Daytona Beach, Florida having a medium-to-coarse sand bottom (the mean grain size was 0.85 phi). Range-independent propagation was assumed for the sites just noted and the agreement between measured and predicted loss was good for frequencies from 100 to 600 Hz. Range-dependent conditions existed for the third site, off the coast of Nova Scotia, where the sound-speed profile, bottom sediments, and depth varied with range. Good agreement was obtained between measured, 1/3-octave transmission loss values and predicted values for frequencies of 25, 80, and 250 Hz.
Note on the independent sampling of mean-square pressure in reverberant sound fields
Authors: Chu W. T.
Published: October 2005

A discussion of the concept of independent sampling of mean-square pressure in pure-tone reverberant sound fields is presented together with a derivation of Lubman’s result on the covariance function of the mean-square pressure.
Hydrophone nonlinearity measurements
Authors: Moffett Mark B. , Henriquez Theodore A.
Published: October 2005

Measurements of the second-order sensitivity, i.e., nonlinear response, are reported for several hydrophones in common use. The measurement technique utilizes a dual-frequency incident wave with closely spaced frequencies. The difference-frequency output of the hydrophone is then measured to yield the second-order sensitivity. The primary frequencies ranged from 15–300 kHz. Hydrophones of the same type and first-order sensitivity can have quite different second- order sensitivities. The nonlinearities are not electrostrictive in origin and are appreciably larger than pseudosound levels. They may be mechanical nonlinearities of the bond or boot materials.
Slow vertex potentials evoked by whole-body impulsive vibrations in recumbent men
Authors: Miwa Toshisuke , Yonekawa Yoshiharu , Kanada Kazuo
Published: October 2005

Characteristics of slow vertex responses evoked by whole-body vertical and horizontal impulsive vibrations of one cycle of a sinusoid were investigated in recumbent men. Fundamental frequencies were varied from 8 to 100 Hz. The p–p amplitudes and latencies of V potentials were determined as a function of vibration amplitude and fundamental frequency. The response patterns are similar to those evoked by optical and acoustic stimuli to human visual and auditory organs. The thresholds of the evoked potentials were determined by a cross-correlation technique and the perceptional thresholds were measured for the same vibration. It is concluded that the perceptional thresholds can be estimated approximately from the thresholds of the evoked potentials, for example, by subtraction of 14.5 dB from the thresholds of the evoked potentials for vertical vibrations and 10 dB from those for horizontal vibrations from 8 to 100 Hz.
Mapping of a crack edge by ultrasonic methods
Authors: Norris A. N. , Achenbach J. D.
Published: October 2005

Two methods are proposed for the mapping of cracklike flaws in homogeneous, isotropic, elastic media. The methods require as input data the travel times of diffracted ultrasonic signals. The first method maps points on the crack edge by a process of triangulation with the source and receiver as given corner points of the triangle. By the use of travel times for neighboring positions of the source and/or the receiver, the direction of signal propagation, which is the necessary constitutent required to complete the triangle, can be computed. The inverse mapping is global in the sense that no a priori knowledge of the location of the crack is required. The second method is a local edge mapping which determines sets of planes relative to a known point close to the crack edge. Each plane contains a flash point. The intersection of the envelopes of two sets of planes maps an approximation to the crack edge.
Recognition of musical key: Exploratory study
Authors: Terhardt Ernst , Ward W. Dixon
Published: October 2005

The initial 5 s of each of the 12 major-key preludes from J. S. Bach’s Well-Tempered Clavichord was recorded by an expert pianist, either as written or shifted by plus/minus 1, 4, 6, or 7 semitones, and a randomized tape consisting of two repetitions of each of the 108 items was prepared. Twenty musicians, mostly pianists, and two nonmusicians judged whether each item was played in the correct key, transposed up, or transposed down; a simplified version of original (correct) score was printed on the answer sheet. Only four subjects failed to discriminate, at the 5% confidence level, the correct rendition from the transposed ones, even when only the ±1-semitone transpositions are considered. Errors are dependent on the ’’linear distance’’ of transposition (i.e., pitch height offset) rather than ’’harmonic distance’’ (i.e., offset on the circle of fifths). The subjects claiming to possess absolute pitch performed slightly better than the best of the nonpossessors, but the results suggest that absolute identification of tonality is an ability that is more widespread than commonly supposed.
Acoustically evoked activity of single efferent neurons in the guinea pig cochlea
Authors: Cody A. R. , Johnstone B. M.
Published: October 2005

Single auditory units in Rosenthal’s canal in the guinea pig cochlea demonstrate the high degree of frequency selectivity and threshold sensitivity that is generally associated with afferent neurons. However, the response of these units to acoustic stimuli is characteristic of efferent neuron behavior recorded at other locations in the auditory pathway.
Input impedance of the cochlea in cat
Authors: Lynch Thomas J. , Nedzelnitsky Victor , Peake William T.
Published: October 2005

Tones were delivered directly to the stapes in anesthetized cats after removal of the tympanic membrane, malleus, and incus. Measurements were made of the complex amplitudes of the sound pressure on the stapes PS, stapes velocity VS, and sound pressure in the vestibule PV. From these data, acoustic impedance of the stapes and cochlea ZSC-PS/US, and of the cochlea alone ZC-PV/US were computed (US-volume velocity of the stapes = VS×area of the stapes footplate). Some measurements were made on modified preparations in which (1) holes were drilled into the vestibule and scala tympani, (2) the basal end of the basilar membrane was destroyed, (3) cochlear fluid was removed, or (4) static pressure was applied to the stapes. For frequencies between 0.5 and 5 kHz, ZSC?ZC; this impedance is primarily resistive (‖ZC‖?1.2×106dyn-s/cm5) and is determined by the basilar membrane and cochlear fluids. For frequencies below 0.3 kHz, ‖ZSC‖≳‖ZC‖ and ZSC is primarily determined by the stiffness of the annular ligament; drying of the ligament or changes in the static pressure difference across the footplate can produce large changes in ‖ZSC‖. For frequencies below 30 Hz, ZC is apparently controlled by the stiffness of the round-window membrane. All of the results can be represented by an network of eight lumped elements in which some of the elements can be associated with specific anatomical structures. Computations indicate that for the cat the sound pressure at the input to the cochlea at behavioral threshold is constant between 1 and 8 kHz, but increases as frequency is decreased below 1 kHz. Apparently, mechanisms within the cochlea (or more centrally) have an important influence on the frequency dependence of behavioral threshold at low frequencies.
Envelope statistics of partially saturated processes
Authors: Mikhalevsky Peter N.
Published: October 2005

The probability density functions associated with the envelope and phase of a partially saturated process are derived. The derivation assumes that the single path phases are Gaussian random variables with arbitrary means but with identical variances σ2ϑ. The analysis also includes the effects of Gaussian noise on the statistics. It is shown that in the limit as the standard deviation of the single path phases becomes large (≳π/2), the densities approach previously derived results for fully saturated phase random propagation. In the limit as σϑ→0, the densities for unsaturated propagation, namely constant signal plus Gaussian noise, are recovered. The results derived are used for determining the distributions of fades and receiver operating characteristics for a partially saturated process. The fading probability and the signal-to-noise ratio required to detect the partially saturated signal is directly proportional to σϑ.
Loudness, annoyance, and noisiness produced by single-tone-noise complexes
Authors: Hellman Rhona P.
Published: October 2005

Single tones centered within the noise spectrum were added to three different broadband spectra: flat, low pass, and high pass. Judgments of overall loudness, annoyance, and noisiness (perceived magnitude) were obtained by absolute magnitude estimation (AME) supplemented by loudness matching. The data were evaluated to determine how the overall SPL of the noise-tone complex, and tone-to-noise ratio affect judged perceived magnitude. In addition, the relationship among the three judged attributes was assessed. Results obtained with the different noise spectra show that the growth of perceived magnitude is a nonmonotonic function of the overall SPL of the noise-tone complex. More summation between tone and noise was found for relatively small tone- to-noise ratios (+5, +10, +15 dB), as measured in 1/3-octave bands, than for relatively large tone-to-noise ratios (+20 dB and greater). Data analysis suggests that the extent of the increments and decrements in perceived magnitude depends on the absolute loudnesses of the component stimuli, the interaction between a specific tone frequency and noise spectrum, and the attribute judged. An attempt is made to quantify the observed effects and to relate them to the published results of other investigators.
Verification of a one-dimensional analysis of sound propagation in a variable area duct without flow
Authors: Miles J. H.
Published: October 2005

A predicted standing wave pressure and phase angle profile for a hard wall rectangular duct with a region of converging–diverging area variation is compared to published experimental measurements in a study of sound propagation without flow. The factor of 1/2 area variation used is of sufficient magnitude to produce large reflections. The prediction is based on a transmission matrix approach developed for the analysis of sound propagation in a variable area duct with and without flow. The agreement between the measured and predicted results is shown to be excellent.
The attenuation of ultrasound in dilute polymeric fiber suspensions
Authors: Habeger C. C.
Published: October 2005

Experimental data for the attenuation of ultrasound by dilute fiber suspensions are presented. Measurements are taken from 0.6 to 10 MHz using rayon, polyester, and nylon fibers with radii in the 7- to 120-μm range. A theory of attenuation due to isolated, infinite, cylindrical inclusions in a fluid is developed. Theory and experiment are found to be in good agreement.
Sound absorption based on ocean measurements: Part I: Pure water and magnesium sulfate contributions
Authors: Francois R. E. , Garrison G. R.
Published: October 2005

Between 10 and 1000 kHz the absorption of sound in sea water can be considered as the sum of contributions from pure water and magnesium sulfate. Near 10 kHz there is also a small contribution from boric acid. In this paper, the contribution from MgSo4 is treated extensively using the authors’ measurements of absorption in the ocean to construct a quantitative equation for absorption as a function of temperature, salinity, and depth. The frequency region below 10 kHz, where the boric acid contribution predominates, will be reviewed later in Part II which includes an equation for the total absorption in the frequency range 400 Hz to 1 MHz.