bluuebunny/crossref_metadata_2025 huggingface dataset:
Coupled piano strings
Authors: Weinreich Gabriel
Published: October 2005

The admittance of the piano bridge has a crucial effect on piano tone by coupling together the strings belonging to one note into a single dynamical system. In this paper, we first develop theoretical expressions that show how the rate of energy transmission to the bridge as a function of time (including the phenomena of beats and ’’aftersound’’) depends on bridge admittance, hammr irregularities, and the exact state in which the piano is tuned. We then present experimental data showing the effects of mutual string coupling on beats and aftersound, as well as the great importance of the two polarizations of the string motion. The function of the una corda pedal in controlling the aftersound is explained, and the stylistic possibilities of a split damper are pointed out. The way in which an excellent tuner can use fine tuning of the unisons to make the aftersound more uniform is discussed.
Generalized Fourier transform diffraction theory for parabolically anisotropic media
Authors: Szabo Thomas L.
Published: October 2005

A convenient diffraction formalism is presented for a planar ultrasonic source of arbitrary shape radiating into a medium which is parabolically anisotropic (or isotropic). Under the Fresnel approximation, the field amplitude is shown to be a Fourier transform of the aperture source function for both the nearfield and farfield. For the two-dimensional (surface-wave) case, closed-form field expressions were obtained for the following source shapes: rectangular, Gaussian, truncated cosine, and truncated Gaussian. Diffraction loss and phase advance curves for equal and unequal apertures show that the nearly ideal characteristics of a Gaussian source can be approximated well by truncated source shapes.
Measurement of acoustic fields using schlieren and holographic techniques
Authors: Moore W. E. , Bucaro J. A.
Published: October 2005

Two methods, schlieren imaging and acoustical holography, are shown to be useful for quantitatively measuring detailed nearfield and farfield acoustic radiation patterns from a submerged cylindrical target. The two imaging methods are discussed so as to illustrate the fundamental mechanisms of imaging involved. The advantages and limitations of each are made clear, and examples of typical laboratory acoustic field measurements are shown for a cylindrical aluminum target. The farfield of the target is computed from an emerging theory for nonrigid cylinders, and the experimental farfield data obtained holographically is shown to agree with that theory. The nearfield of the same target is plotted directly from the photo intensity of the schlieren image.
Optimum detection of signals in non-Gaussian noise
Authors: Sheehy Jerome J.
Published: October 2005

The purpose of this paper is to derive optimum processing structures for use in the detection of signals in additive non-Gaussian noise. The cases chosen for analysis are of particular interest in sonar detection problems since it has been reported that ambient ocean noise may, under sone conditions, deviate from the Gaussian model. The processing structures are considered to be models of the likelihood ratio which is an optimum test no matter what the signal and noise statistics, and optimum single channel and array processors are derived for the small signal-to-noise ratio cases where (1) the signal is completely known, and (2) the signal is a noiselike, not necessarily Gaussian, zero-mean process. Expressions are derived which compare the performance of processors optimized for non-Gaussian noise with those optimized for Gaussian noise for each of the two cases, with transfer functions for the required optimum nonlinear filters and the expected improvements in performance determined using some ’’typical’’ non-Gaussian probability density functions. Justification of these particular density functions is beyond the scope of this paper except to note that very good agreement is obtained with some published experimental data. New results include the derivation of optimum array processors for the detection of plane wave signals when the array is steered at the signal arrival angle, in a non-Gaussian noise field and the development of expressions to predict their performance for the case where the signal is a zero-mean, noiselike process.
Passive bearing estimation: The removal of bias and 2π ambiguities
Authors: Shensa M. , Black C.
Published: October 2005

Averaging across frequency presents one means of combating noise in split-beam bearing estimation. Unfortunately, simple phase averaging is a biased estimator, and, in the case of split-beam analysis, suffers as well from spatial aliasing. Both of these difficulties arise from the 2πn uncertainty inherent in any phase angle observation. This paper provides several algorithms utilizing an iterative averaging technique which circumvents these problems. Convergence theorems are provided for the algorithms and an evaluation on synthetic data shows them to be highly successful. The techniques developed are quite general and should find use in many situatios in which angle averaging or averaging of functions of angles is pertinent.
Remote detection of turbulence from observations of reverberation spectra
Authors: Rasmussen Robert A.
Published: October 2005

The narrowness of normally occurring, oceanic high-frequency reverberation spectra is attributed to scatterers at rest relative to the water. Turbulent scatterer motion induced by any mechanism is revealed in a broadening of these spectra, and its localization is afforded by comparisons of spectra obtained from contiguous portions of the insonified volume. Fundamental constraints are imposed on turbulence detection and localization processes by the instrumentation geometry and signal waveform, and their delineation is a primary goal of the present investigations. Methods for overcoming these constraints through modifications of the signal waveform, refinement of the receiver and application of postdetection processing schemes are considered. Limitations arising from platform motion and their circumvention are also examined.
Rejection of sonar interference of finite bandwidth by amplitude shading of transducer arrays
Authors: Wang H. S. C.
Published: October 2005

Following the work reported in an earlier paper, the possibility of rejecting coherent interference of finite bandwidth and distributed direction of incidence by purely amplitude shading of a transducer array is investigated. Using the same linear transducer array immersed in the same distributed interference and ambient noise fields, it is demonstrated that, if the array shading is optimized by assuming all the interference power to be concentrated at its band center, interference of bandwidths up to 10% of its center frequency and intensity 70 dB above ambient noise field can be effectively rejected. This confirms that the theroy reported earlier is adequate for applications in narrow-band receiving systems. If a broadband interference power quadratic is used in the process of shading optimization, the above interference-rejecting capability can be extended to a bandwidth equal to 40% of its center frequency. These results further suggest that an optimum/adaptive broadband beamformer for passive sonar typically needs to be amplitude shaded in only eight bands.
Variance of the wave amplitude in a random medium with a nonuniform background
Authors: Chen Kenneth C.
Published: October 2005

Variance of the wave amplitude in a random medium with a nonuniform background is obtained by the method of geometrical optics. A minor discrepancy of earlier results is clarified.
The Typical Noise: first step in the development of a short procedure for estimating performance of hearing protectors
Authors: Tobias Jerry V. , Johnson Daniel L.
Published: October 2005

An exact measurement of the effectiveness of a hearing protector requires the determination of how well it works in the specific noise in which it is to be worn. As a practical matter, though, people do not generally remain in a single noise spectrum throughout a working career or even throughout a working day, so it does not matter so much that most measurers are not likely to be equipped to perform spectrum analyses. Other techniques for judging earplugs and earmuffs are obviously necessary. Previous research has tried to find the average attenuation given by a particular device in several (or many) noises, or it has tried to deal with the attenuation given in noises with particular C-minus-A values. In this paper, a procedure is developed for compressing these multiple-spectra calculations into a single-spectrum computation that proves to be at least as accurate as the more complex methods.
Effect of speaking rate on vowel formant movements
Authors: Gay Thomas
Published: October 2005

The purpose of this experiment was to study the effects of changes in speaking rate on both the attainment of acoustic vowel targets and the relative time and speed of movements toward these presumed targets. Four speakers produced a number of different CVC and CVCVC utterances at slow and fast speaking rates. Spectrographic measurements showed that the midpoint format frequencies of the different vowels did not vary as a function of rate. However, for fast speech the onset frequencies of second formant transitions were closer to their target frequencies while CV transition rates remained essentially unchanged, indicating that movement toward the vowel simply began earlier for fast speech. Changes in both speaking rate and lexical stress had different effects. For stressed vowels, an increase in speaking rate was accompanied primarily by a decrease in duration. However, destressed vowels, even if they were of the same duration as quickly produced stressed vowels, were reduced in overall amplitude, fundamental frequency, and to some extent, vowel color. These results suggest that speaking rate and lexical stress are controlled by two different mechanisms.
Use of nonsense-syllable mimicry in the study of prosodic phenomena
Authors: Liberman Mark Y. , Streeter Lynn A.
Published: October 2005

The technique of nonsense-syllable mimicry of natural utterances has many advantages in the study of prosodic phenomena, especially duration. In analytic studies, the elimination of segmental effects as a factor makes data collection much more efficient, and requires only one segmentation criterion. In perceptual studies, the technique eliminates lexical information without unnatural distortions of the signal. In a series of validation experiments, we have found that (1) the patterns of duration obtained by using this technique were stable and reproducible within and across speakers; and (2) mimicry of different natural models with identical stress patterns and constituent structures produced nearly indistinguishable nonsense-syllable duration patterns.
Hearing ’’words’’ without words: Prosodic cues for word perception
Authors: Nakatani Lloyd H. , Schaffer Judith A.
Published: October 2005

We found that the stress pattern and rhythm of speech were prosodic cues for word perception in trisyllabic adjective–noun phrases. When listeners heard a ’’ma mama’’ nonsense phrase that mimicked an actual English adjective–noun sequence such as ’’new result,’’ they correctly parsed (divided) the phrase into the words ’’ma’’ and ’’mama’’ corresponding to ’’new’’ and ’’result.’’ Listeners must have used prosodic features to parse the phrases because the speech had the stress pattern, rhythm, and pitch prosody of normal speech, but had none of the usual meaning and sound cues for words. The stress pattern was a prosodic cue for word perception because the phrases were easy or hard to parse depending on their stress pattern. And rhythm was also a prosodic cue for word perception because the parsing of a phrase was changed when its rhythm was changed via synthetic speech. But the pitch and amplitude contours were not prosodic cues for word perception because the parsing of a phrase remained unchanged when its pitch and amplitude contours were changed via synthetic speech. The results suggest that, in the rule synthesis of speech, the rules for stress and rhythm must be carefully formulated because they affect not only the naturalness of the speech, but also the ease with which it can be understood.
Investigating the MESA (Multipoint Electrotactile Speech Aid): The transmission of segmental features of speech
Authors: Sparks David W. , Kuhl Patricia K. , Edmonds Alice E. , Gray Gary P.
Published: October 2005

Four normal-hearing young adults have been extensively trained in the use of a tactile speech-transmission system. Subjects were tested in the recognition of various phonetic elements including vowels, and stop, nasal, and fricative consonants under three receiving conditions; visual reception alone (lipreading), tactile reception alone, and tactile plus visual reception. Subjects were artificially deafened using earplugs and white noise and all speech tokens were presented live voice. Analysis of the data demonstrates that the tactile transform enables receivers to achieve excellent recognition of vowels in CVC context and the consonantal features of voicing and nasality. This, in combination with high recognition of vowels and the consonantal feature place of articulation through visual reception, leads to recognition performance in the combined condition (visual plus tactual) which far exceeds either reception condition in isolation.
’’1/f noise’’ in music: Music from 1/f noise
Authors: Voss Richard F. , Clarke John
Published: October 2005

The spectral density of fluctuations in the audio power of many musical selections and of English speech varies approximately as 1/f (f is the frequency) down to a frequency of 5×10−4 Hz. This result implies that the audio-power fluctuations are correlated over all times in the same manner as ’’1/f noise’’ in electronic components. The frequency fluctuations of music also have a 1/f spectral density at frequencies down to the inverse of the length of the piece of music. The frequency fluctuations of English speech have a quite different behavior, with a single characteristic time of about 0.1 s, the average length of a syllable. The observations on music suggest that 1/f noise is a good choice for stochastic composition. Compositions in which the frequency and duration of each note were determined by 1/f noise sources sounded pleasing. Those generated by white-noise sources sounded too random, while those generated by 1/f2 noise sounded too correlated.
Characteristic wave numbers for simple source formulations of acoustic radiation and diffraction problems
Authors: Murphy Joseph E.
Published: October 2005

It is shown that the characteristic wave numbers for which the simple source formulation of acoustic diffraction problems fails can be obtained directly by use of the model’s integral equation. Characteristic wave numbers for diffraction by a rigid cylinder and by a rigid sphere are determined.
Noncombination of pitch and loudness in multidimensional scaling
Authors: Zagorski M. A.
Published: October 2005

Carvellas and Schneider [J. Acoust. Soc. Am. 51, 1839–1848 (1972)], using magnitude estimates of the dissimilarity of sinusoidal tones in a multidimensional scaling program, found that their data fit a city-block and a Euclidean metric equally well, but other research has indicated that subjects do not combine dimensions of sinusoidal tones to arrive at an overall estimate of stimulus similarity. Yet multidimensional scaling seems to require subjects to combine dimensions of similarity. In this letter a model is put forward to demonstrate that subjects need not combine dimensions directly in order to generate dissimilarity judgments that are very close to either the city-block or Euclidean metrics. Thus it is possible that while subjects do not combine the dimensions perceptually they can adopt a cognitive strategy that leads one to believe they do.
Condenser electret hydrophones
Authors: Hennion C. , Lewiner J.
Published: October 2005

Condenser electret transducers, which are greatly used in the aerial field, have not yet been developed for underwater acoustics. In this paper we describe various condenser electret hydrophones using multisupported foils. Sensitivities as high as 1 mV/Pa, i.e.,−180 dB (re 1 V/μPa) have been obtained, from a fraction of 1 Hz up to 10 kHz. The pressure level equivalent to noise level is below the sea-state zero level.
Signal speed in long-range propagation
Authors: Mitchell Stephen K. , Hampton Loyd D.
Published: October 2005

The speed of acoustic signals traveling from a large number of explosive sources in the Northeast Pacific and North Atlantic oceans has been measured and compared with the predictions of ray theory. Signal speed is defined here as the horizontal source-to-receiver range divided by the time from source detonation to the earliest detection of the signal at the receiver. The ray-tracing predictions show that signal speed may vary by as much as 1% or more; changes of 15 m/s may occur within a 1.8-km range interval. The nature of the signal-speed-versus-range curve depends on the sound-velocity profile and the source and receiver depths. The measurements show that the predicted features, in particular the regular fluctuation of signal speed, are readily observed.
Categorical perception—phenomenon or epiphenomenon: Evidence from experiments in the perception of melodic musical intervals
Authors: Burns Edward M. , Ward W. Dixon
Published: October 2005

Categorical perception was investigated in a series of experiments on the perception of melodic musical intervals (sequential frequency ratios). When procedures equivalent to those typically used in speech-perception experiments were employed, (i.e., determination of identification and discrimination functions for stimuli separated by equal physical increments), musical intervals were perceived categorically by trained musicians. When a variable-step-size (adaptive) discrimination procedure was used, evidence of categorical perception (in the form of smaller interval-width DL’s for ratios at identification category boundaries than for ratios within categories), although present initially, largely disappeared after subjects had reached asymptotic performance. However, equal-step-size discrimination functions obtained after observers had reached asymptotic performance in the adaptive paradigm were not substantially different from those initially obtained. The results of other experiments imply that this dependence of categorical perception on procedure may be related to differences in stimulus uncertainty between the procedures. An experiment on the perception of melodic intervals by musically untrained observers showed no evidence for the existence of ’’natural’’ categories for musical intervals.
Theory of scattering by rigid bodies with thin liquid coatings
Authors: Eisler Thomas J.
Published: October 2005

A plane wave is incident on a rigid body which is partially or totally surrounded by a thin liquid coating whose (possibly variable) density and sound velocity differ from those of the ambient medium. By assuming the incident wavelength to be large compared with coating thickness, approximate expressions for the scattered field are obtained in integral form. By further assuming incident wavelength to be small compared with typical dimensions of the rigid body, the integrals are evaluated asymptotically and the scattered field is expressed in terms of contributions from certain scattering centers of the coating, viz., the specular point and points at which incident rays are perpendicular to the edge of the coating. As an example the method is applied to the problem of a partially coated sphere.
Nonlinear attenuation of an N wave propagating in a tube, including dissipation due to wall effects
Authors: Nakamura Akira , Takeuchi Ryoichi , Oie Samon
Published: October 2005

Theoretical computations are made for the variation of waveform of an N wave propagating in a circular tube. The change with distance of the slope of the straight-line segment of the waveform at its axis crossing is calculated. Various assumptions are made in the calculation to isolate the separate contributions of weak-shock theory and tube-wall effects. The change in slope is as predicted by weak-shock theory. The slope is affected by tube-wall dissipation, but virtually unaffected by velocity dispersion. Measurements are reported pressure profiles of N waves at various distances in a tube. Experiments were done with several different gases. The agreement between theoretical and observed values is fairly good.
Sound velocity–density relations in sea-floor sediments and rocks
Authors: Hamilton Edwin L.
Published: October 2005

In studies in underwater acoustics, geophysics, and geology, the relations between sound velocity and density allow assignment of approximate values of density to sediment and rock layers of the earth’s crust and mantle, given a seismic measurement of velocity. In the past, single curves of velocity versus density represented all sediment and rock types. A large amount of recent data from the Deep Sea Drilling Project (DSDP), and reflection and refraction measurements of sound velocity, allow construction of separate velocity–density curves for the principal marine sediment and rock types. The paper uses carefully selected data from laboratory and in situ measurements to present empirical sound velocity–density relations (in the form of regression curves and equations) in terrigenous silt clays, turbidites, and shale, in calcareous materials (sediments, chalk, and limestone), and in siliceous materials (sediments, porcelanite, and chert); a published curve for DSDP basalts is included. Speculative curves are presented for composite sections of basalt and sediments. These velocity–density relations, with seismic measurements of velocity, should be useful in assigning approximate densities to sea-floor sediment and rock layers for studies in marine geophysics, and in forming geoacoustic models of the sea floor for underwater acoustic studies.
Detectability of varying interaural temporal differencesa)
Authors: Grantham D. Wesley , Wightman Frederic L.
Published: October 2005

Dectectability and salience of time-varying interaural temporal differences (IATD’s) were measured in three experiments by determining observers’ ability to follow the temporal fluctuations of a ’’moving stimulus’’—a 3000-Hz low-pass computer-generated noise presented binaurally with a sinusoidally varying IATD. In the first two experiments the peak IATD (Δt the ’’extent of movement’’) was manipulated to determine, for different rates of interaural variation (fm), threshold discriminability of the ’’moving’’ stimulus from a reference (two-interval forced-choice paradigm). The nonmoving reference was either a dichotic noise stimulus (experiment 1) or a diotic noise stimulus whose ’’image width’’ matched that of the excursions traced by the ’’moving stimulus’’ (experiment 2). Threshold Δt’s in the two experiments were similar, increasing from 30 μs at fm=0 Hz to 90 μs at fm=20 Hz, indicating a ’’low-pass characteristic’’ for the binaural system. Thresholds decreased again for fm≳50 Hz, apparently because at these high rates of ’’movement’’ observers used other cues than the varying IATD’s to perform the task. The third experiment measured the threshold of a binaural click in the presence of a ’’moving noise’’ masker as a function of ’ifm and of the instantaneous IATD of the masker when the click was presented. As fm increased, click threshold gradually became independent of the masker’s instantaneous IATD, again suggesting a ’’low-pass’’ characteristic for the binaural system; additionally, there was some evidence for a lag in the system’s response for fm≳5 Hz. The data from the three experiments are discussed in terms of results from other studies which have investigated temporal aspects of the binaural system. The possible existence of movement detectors in the auditory system is discussed.
Swept-frequency diffraction of ultrasound by cylinders and arrays
Authors: Lee Paul P. K. , Waag Robert C. , Hunter Lloyd P.
Published: October 2005

Diffraction of ultrasound in water by single cylinders and arrays of equally spaced cylinders is studied experimentally using a swept-frequency technique and the results are compared with theoretical predictions. Scattering by single metallic cylinders is computed from a model which includes the effect of reverberations within the cylinder. A one-dimensional, single-scattering approximation is used for data reduction in the case of the regular array where Fourier inversion of the data is used to determine the scatterer spacing of the array. Swept-frequency measurements were made in a fixed geometry using long pulses of a sinusoidal signal whose center frequency was essentially constant during the pulse interval but was varied over the total sequence of pulses. The observed scattering spectrum of a single metallic cylinder agrees closely with the calculated prediction. The Fourier transformation spectra of the array scattering data shows good agreement with the known scatterer spacing even when the data were taken in the nearfield and the data are reduced using a plane wave, farfield assumption. This investigation provides a foundation for additional studies of factors involved in the use of ultrasound diffraction in tissue characterization.
Underwater Doppler tracking using optimization techniques
Authors: Wilcox Roland E.
Published: October 2005

A new method is presented for passively tracking a submarine with respect to N omnidirectional sonabuoys by utilizing the noise perturbed Doppler shifts in one or more frequencies emitted by the target. In contrast to contemporary approaches to this problem such as Kalman filtering techniques, the approach adopted here requires no a priori assumptions of a Gaussian noise field or straight-line motion and constant target speed. An algorithm based on accelerated-gradient optimization techniques is used to track the target by outputting a position and velocity estimate for every time period τ that the FFT processor forms an output. Thus, the algorithm is fast enough to follow the target in real time with a nonincreasing lag. Computer simulation shows this method holds much promise in competing with other alternatives, particularly in following maneuvering targets such as a sinusoid trajectory through a buoy field.
Asymptotic threshold shift in chinchillas exposed to impulse noise
Authors: Blakeslee E. A. , Hynson K. , Hamernik R. P. , Henderson D.
Published: October 2005

Five monaural chinchillas were exposed to a repetitive, reverberant, impulse noise for ten days. The impulse-noise source was a mechanized hammer hitting a steel plate at a rate of 1/s. The average, peak over pressure within the holding cage was 113 dB SPL. Auditory thresholds were determined before and after exposure at 0.5, 1, 1.4, 2, 2.8, 4, 8, and 16 kHz utilizing shock-avoidance conditioning. During exposure, thresholds were monitored on a daily basis at 0.5 and 8 kHz. Within one hour from the start of the exposure, threshold shift at 8 kHz had reached an asymptotic level, while threshold shift at 0.5 kHz leveled off after 24 h of exposure. Asymptotic threshold shift (ATS) levels for both frequencies varied between 30 and 50 dB across animals. Median threshold shift for both frequencies recovered to within 10 dB of normal after 40 days of recovery. Maximum permanent threshold shift (PTS) was at 2 and 2.8 kHz with median PTS of 17 and 13 dB, respectively. After final thresholds were obtained (50–70 days), the cochleas were examined histologically using the surface preparation technique. A comparison is made between impulse-noise-induced ATS and ATS produced by continuous-noise sources.
Cross-language study of speech-pattern learning
Authors: Simon Claude , Fourcin Adrian J.
Published: October 2005

In order to investigate the nature of some processes in speech acquisition, synthetic speechlike stimuli were played to groups of English and French children between two and fourteen years of age. The acoustic parameters varied were voice onset time and first-formant transition. Three stages were observed in the development of children’s labeling behavior. These were called scattered labeling, progressive labeling, and categorical labeling, respectively. Individual response patterns were examined. The first stage (scattered labeling) includes mostly children of two to three years of age for the English and up to about four for the French. Children label most confidently those stimuli closest in physical terms to those of their natural speech environment. All stimuli with intermediate VOT values are labeled quasirandomly. Progressive labeling behavior is found mostly amongst children aged three and four for the English, up to about seven for the French. Children’s response curves go progressively—almost linearly—from one type of label (voiced) to the other (voiceless): response follows stimulus continuum. Categorical labeling becomes the dominant pattern only at the age of five to six for the English, one or two years later for the French. This development was found to be highly significant (p smaller than 0.003 for both English and French, using Kendall’s tau measure of correlation). English children learn to make use of the F1 transition feature around five years, whereas French children never use it as a voicing cue. French children will have fewer features than English children at their disposal: This may account for the later age at which French children, as a group, reach the various labeling behavior stages, and for labeling curves being less sharply categorical for French than for English children. These findings indicate that categorical labeling for speech sounds is not innate but learned through a relatively slow process which is to a certain extent language specific. The implications of the results are discussed in the light of previous work in the field.
Syncopated auditory polyrhythms: Discontinuous reversals in meter interpretation
Authors: Oshinsky James S. , Handel Stephen
Published: October 2005

Subjects tapped the beat (i.e., meter) of a polyrhythm in which one tone occurred three times per pattern repitition while the second tone occurred four times per pattern repitition. At one presentation rate, the polyrhythm underwent a figure-ground reversal —the beat shifted from one tone to the other. Rhythmic organization is thus a function of the absolute tempo.
A modal perspective of lung response
Authors: Fredberg Jeffrey J.
Published: October 2005

The qualitative modal structure of lung response is investigated. Asymmetry of the branching airway network of the lung leads to clumping of system eigenvalues into distinct and well-separated clusters at low frequency. The breadth of the eigenvalue clusters increases with the degree of asymmetry and frequency. At high frequency the breadth of the clusters exceeds the cluster spacing so that distinct eigenvalue clusters are no longer observed. Symmetric airway networks lead to degenerate mode clusters with large eigenvalue redundancy. The average density of eigenvalues of the undamped system is estimated to be higher than 0.5 per Hz. All modes appear to be in modal overlap.
Sensitivity of the schlieren method for the visualization of low-frequency ultrasonic waves
Authors: Bucaro J. A. , Dardy H. D.
Published: October 2005

Schlieren visualization of ultrasonic waves is usually carried out at megahertz frequencies since it is generally realized that lower-frequency waves are much more difficult to observe. This paper considers the factors involved in the frequency dependence of the sensitivity of an ideal diffraction-limited schlieren system. The results indicate that relatively low-amplitude sound waves can be visualized even at low-kilohertz frequencies. A techique is suggested which would make the sensitivity at these low frequencies comparable to that at the higher frequencies.
Method for the measurement of the sound velocity in metastable liquids, with an application to water
Authors: Trinh Eugene , Apfel Robert E.
Published: October 2005

A standard optical Schlieren method has been adapted to the problem of measuring the speed of sound in moderately supercooled and in superheated liquids under atmospheric pressure. The estimated accuracy is ±3 m/s. Results in supercooled water down to −16.75 °C and in superheated water up to 176.5 °C are reported.
Frequency analysis of two types of simulated acoustic emissions
Authors: Pardee W. J. , Graham L. J.
Published: October 2005

It has been suggested that the frequency spectrum of an acoustic emission burst may be a partial ’’signature,’’ identifying the source. To explore this possibility we have studied in some detail, theoretically and experimentally, two qualitatively different simulated acoustic emissions. The first is the fracture of small (20–40 μm) silicon carbide grains on a steel slab. The second is the impact of a small elastic sphere of various materials on the same slab. Our primary objective has been to test our understanding of the medium response, and, consequently, the extent to which we can determine the source spectrum from the observed spectrum.
Effect of an expansion chamber on the propagation of sound in circular ducts
Authors: El-Sharkawy A. I. , Nayfeh Ali H.
Published: October 2005

An analytical and experimental study is presented of sound propagation through a circular duct in the presence of an expansion chamber. Results are presented for various sound frequencies, expansion ratios, and chamber lengths. It is found that the analytical results are in good agreement with the experimental results.
Propagation of sound in a curved bend containing a curved axial partition
Authors: Fuller Christopher R. , Bies David A.
Published: October 2005

Sound transmission in a 180° bend containing a curved partition positioned on the axial center line is investigated theoretically and experimentally using equations for sound propagation in straight and curved ducts. Good agreement is obtained and small discrepancies are discussed. The partition is found to significantly alter the sound propagation through the bend and reasons for the different acoustic behavior are given.
Underwater acoustic backscattering and echo structure characteristics for a thin stiffened plate
Authors: Alkier K. W.
Published: October 2005

Underwater acoustic reflection characteristics for a thin stiffened aluminum plate were investigated. The thin stiffening rib extends parallel to the edge across the entire width of the plate. A plain plate without the stiffening rib was used as a control. The targets were sequentially suspended in water during the experiments. The stiffening rib on the experimental target was positioned in the acoustic shadow of the plate to avoid specular returns from its edges. Internally guided longitudinal stress waves were detected in both targets for a critical angle of incidence of 15.8°, at a frequency of 60 kHz and a 30-μsec pulse width. Based on ray theory and the assumption that these stress waves were reflected at the reinforcing rib, theoretical travel times, and pulse-reflection periods were calculated. Good agreement between theoretical and experimental results was achieved. Pulse decay rates in the form of logarithmic decrement of internally guided longitudinal stress waves are shown to be a significant clue to the presence and location of a reinforcing rib in thin plates.
Propagation of sound in underwater surface channels with rough boundaries
Authors: Barnard G. R. , Deavenport R. L.
Published: October 2005

A study is made of sound propagation in surface channels with rough boundaries. A generalized phase integral approach is formulated for calculating the complex eigenvalues due to leakage and surface roughness. Calculations of propagation loss versus range are given for the bilinear profile and compared with experimental data.
Effect of line-discontinuity admittance on sound scattered by plate vibration
Authors: Chandiramani K. L.
Published: October 2005

We investigate how the force and moment impedance of a line discontinuity on a plate influences the sound scattered by impingement of plate flexural waves on the line discontinuity. Effects of fluid loading are accounted for. For a specific high-frequency situation, we numerically evaluate three line-discontinuity models: a simple support, a clamped support, and a support whose force and moment susceptances cancel out the corresponding susceptances of the plate driving-point admittances. Calculated are total acoustic powers radiated and farfield pressure patterns. We also calculate, for two angular locations, contours of constant radiated pressure in the line-discontinuity force-admittance–moment-admittance plane. It is shown that under certain circumstances slight changes in the line-discontinuity admittance can cause relatively large changes in the radiated pressure.
Insulating buildings from aircraft noise
Authors: Quirt J. D.
Published: October 2005

Field measurements of insulation against aircraft noise were made for a wide range of building components. Single-figure ratings of noise insulation were derived, and a design procedure for use of these ratings is presented. The dependence of the effective sound insulation on the spectral balance of aircraft noise is examined.
Holographic acoustical lens
Authors: Stephanis C. G. , Hampsas G. D.
Published: October 2005

The theory of an acoustical lens is presented and the construction of such a lens is described. In the present work three experiments are described, in which images of acoustical objects are formed. With the acosutical lens the intermediate step of the conventional acoustical holography of transfering the acoustical hologram to an optical system is avoided.
Correlational study of speakers’ heights, weights, body surface areas, and speaking fundamental frequencies
Authors: Lass Norman J. , Brown William S.
Published: October 2005

The purpose of this investigation was to determine the relationship among speakers’ heights, weights, body surface areas, and speaking fundamental frequencies. The recordings of 30 speakers’ readings of a standard prose passage were analyzed by means of the Fundamental Frequency Indicator (FFI) to obtain their speaking fundamental frequency characteristics. The speakers’ heights and weights were obtained by means of standard measurement procedures, and their body surface areas were calculated. Pearson product-moment correlation coefficients, computed separately for men and women, indicated that speakers’ heights, weights, and body surface areas were not significantly correlated with their speaking fundamental frequencies; female speakers showed a slight negative correlation while male speakers showed a low, positive trend. Implications of these findings and suggestions for future research are discussed.
A new principle for the design of condenser electret transducers
Authors: Hennion C. , Lewiner J.
Published: October 2005

In this paper we describe a new principle which can be used to design condenser electret transducers. Contrarily to previously described systems, it does not require an air gap between the moving element (electret or electrode) and the back electrode. It utilizes the relative displacement of electrical charges imbedded in the electret during a nonhomogeneous deformation of the system, with respect to the electrodes of the condenser. This inhomogeneous deformation is obtained through the use of superimposed layers of different tensile moduli. We first describe this general principle and present some preliminary sensitivities.
Ultrasonic imaging system using a moving random phase mask with asymmetric thickness distribution and third-order correlation-function analysis
Authors: Wadaka Shusou , Sato Takuso
Published: October 2005

A new ultrasonic imaging system is proposed which uses a moving asymmetric random phase mask with a δ correlated property. It is shown that the system can achieve higher resolution and less attenuation compared with a conventional system using second-order correlation-function analysis. The system presented in this letter also has the advantage that it is not affected by additive Gaussian noises which are independent of the signal. The usefulness of the system is demonstrated by experimental results for one-dimensional objects.
Effects of particle shape and orientation on propagation of sound in suspensions
Authors: Ahuja Avtar S. , Hendee William R.
Published: October 2005

Particles are assumed to have oblate and prolate spheroidal, spherical, disklike, and needlelike shapes, with symmetry axes for oblate and prolate spheroids assumed to be either parallel or perpendicular to the acoustic field. The disk-shaped and needle-shaped particles are assumed to be either broadside or edgewise (or end on) to the acoustic field. A wave equation is developed for dilute suspensions of the particles which yields a formula for sound velocity and viscous absorption coefficient. For large differences in densities between suspension components, computations indicate substantial effects of particle shape, orientation, and ultrasound frequency on the velocity of sound through the suspension. A particle moving edgewise or end-on to the acoustic field causes a greater loss of sound energy than a particle moving broadside to the acoustic field.
Some simple models describing the transition from weak to strong coupling in statistical energy analysis
Authors: Chandiramani K. L.
Published: October 2005

Two simple situations are considered of N mutually coupled oscillators excited at resonance by external random sources. Formulas are derived for oscillator energies that display explicitly the transition from weak to strong coupling between the oscillators. Average oscillator energy E, the average uncoupled oscillator energy Eu, and the coupled energy Ec are defined. In one situation, E, Eu, and Ec are equal; in the second situation, E is bounded by Eu and Ec.
Analysis of the click-evoked brainstem potentials in man using high-pass noise masking
Authors: Don M. , Eggermont J. J.
Published: October 2005

Brainstem electrical responses (BSER) to 60-dB-SL click in noise high passed at various cutoff frequencies separated by 1/2-octave steps were recorded in normal-hearing adult subjects. By applying a derived response technique, narrow-band contributions to the BSER from specific portions of the basilar membrane were revealed. Latencies and amplitudes of the various waves in the derived BSER were recorded. Results indicate that nearly the whole cochlear partition can contribute to the brainstem response. The shifts in latency of waves I, III, and V and amplitude changes of waves I and III as a function of CF appear to be fully comparable to those of the AP. In contrast, the amplitude behavior of wave V as a function of CF is different from waves I and III depending upon the frequency range. The discrepency in the behavior of wave V with respect to the earlier waves suggests some sort of neural reorganization at the level where wave V is generated. The fact that there are contributions to the brainstem response from apical portions of the cochlea opens the possibility for extending the brainstem technique in assessing the higher cochlear turn function.
Noise-induced threshold shift and cochlear pathology in the mongolian gerbil
Authors: Ryan Allen , Bone Robert C.
Published: October 2005

Groups of six mongolian gerbils were exposed to two-octave (1414–5656 Hz) band noise for 1 h at 100, 110, and 120 dB SPL. Threshold shift at several frequencies was measured 0.5, 3, 6, and 12 h, and 1–28 days after exposure. Final thresholds were determined at least two months postexposure. Extensive threshold shift was observed in all groups 0.5 h after exposure (TS0.5h). Where threshold shift increased in the initial hours after exposure, such increases were correlated with eventual permanent threshold shift (PTS). Recovery of thresholds from 1–28 days after exposure was approximately exponential, and slowest at the edges of the exposure band. PTS was seen in the 110 and 120 dB SPL groups. With TS0.5h of 50 dB or less, no PTS resulted. With TS0.5h above 50–60 dB, eventual PTS increased linearly with a slope of about 1.25 PTS/TS0.5h. Cochlear damage was evaluated by light microscopy. The relationship between hair cell loss and PTS was consistent with an inner hair cell threshold about 40 dB higher that that of outer hair cells. It is suggested that recovery from noise-induced threshold shift may involve different mechanisms in the two types of hair cells.
New cephalostat for speech physiology research
Authors: Abbs James H. , Stivers Daniel
Published: October 2005

A device for stablizing a subject’s head is described which does not depend on earposts, allows for voluntary evacuation by the subject, and can be constructed at low cost. This particular cephalostat is used currently for stabilizing the head in studies of speech production where lip and jaw transduction devices, mounted external to the subject, are employed.
Imitation of synthesized vowels by preschool children
Authors: Kent R. D.
Published: October 2005

Preschool children (mean age of 4 years, 6 months) imitated 15 synthesized formant patterns representing both English and alien vowels. The first three formant frequencies of the imitations were measured from spectrograms. Generally, the children were successful in reproducing the relative formant patterns of the stimuli, although they tended to produce alien vowels as proximal English vowels. The reliability of imitation was better for stimuli modeled on English vowels. Combined with earlier results for men, women, and six-year-old children, the data are consistent with nearly straight isovowel lines in the F– F and F–F planes. The most linear relationship, with a good separation of the mean data for four age–sex groups, was noted for vowel [i]. The results for preschoolers, like those for adult subjects, indicate that the precision of vowel imitation is limited as much, if not more, by auditory resolution as by motor-articulatory performance, because the formant variability in imitation is commensurate with data on difference limens for vowel formant frequency.
Auditory responses in cats produced by pulsed ultrasound
Authors: Foster Kenneth R. , Wiederhold Michael L.
Published: October 2005

Auditory-nerve responses and cochlear microphonics are produced in cats by pulsed 5-MHz ultrasonic energy from a transducer placed against the dura mater. The pulses must be relatively intense (∠30 W/cm2) to produce a response, but can be sufficiently brief (less than 70 μs) that the brain tissue is not observably heated. The cats apparently respond to radiation pressure transients accompanying the absorption of the ultrasound in the brain tissue. Both the amplitude and latency of the N1 neural responses to the ultrasound can be matched to those produced by relatively weak tone pips or clicks from an external source. The cochlear microphonic (CM) produced by a pulse shows a prominent ringing at 5–10 kHz in different cats; the amplitude of the N1 response exhibits broad maximum, for constant amplitude pulses, at pulse widths of 20–60 μs. This variation of N1 response amplitude with pulse width is similar to that of a high-pass filter with a cutoff frequency at the dominent frequency of the CM, which is tentatively identified with a ringing frequency of the skull.
Scattering matrix for elastic waves. II. Application to elliptic cylinders
Authors: Varadan Vasundara V.
Published: October 2005

Using the scattering-matrix approach to elastic wave scattering, numerical results are presented for the scattering of P, SV, and SH waves from a cylinder of elliptic cross section for ratios of minor to major axis ranging from 0.25 to 1.0 and for nondimensional wave numbers in the range 0.1–3.2. Calculations were made for a tungsten cylinder embedded in aluminum and also for a cylindrical cavity in aluminum. The incident waves are taken to be plane waves incident obliquely with respect to the major axis of the ellipse.