bluuebunny/crossref_metadata_2025 huggingface dataset:
Some figural properties of auditory patterns
Authors: Divenyi Pierre L. , Hirsh Ira J.
Published: October 2005

Listeners identified one of six permutations of three frequencies, presented as brief three-note melodies. Identification performance remained high in spite of transposition of the original three frequencies throughout a two-octave range, so long as the musical intervals or frequency ratios between the adjacent pairs of frequencies remained constant. Even when those intervals were compressed or expanded, while remaining about equal to each other, identification was quite good for the range between the lowest and highest frequency of no more than approximately 1/3 octave. Performance decreased sharply when the span was much wider. Unequal intervals, where the low and middle frequencies were closer together or farther apart than the middle and high frequencies, did not retain good identification performance. When the three-tone patterns were embedded in longer sequences of seven or eight tones, the identification performance was best when the pattern occurred at the beginning or the end of the sequence, and when the range of frequencies from which the irrelevant background tones were chosen lay outside the range of pattern frequencies. Under conditions where the background frequencies were fixed and the pattern frequencies were moved, thus combining the manipulation of embedding with that of transposition of the pattern, overlap of pattern and background frequencies was still the principal cause of deterioration in performance. The findings are related to some analogies to the perceptual rules of Gestalt theory, as well as to certain aspects of musical practice.
Stimulated acoustic emissions from within the human auditory system
Authors: Kemp D. T.
Published: October 2005

A new auditory phenomenon has been identified in the acoustic impulse response of the human ear. Using a signal averaging technique, a study has been made of the response of the closed external acoustic meatus to acoustic impulses near to the threshold of audibility. Particular attention has been paid to the waveform of the response at post excitation times in excess of 5 ms. No previous worker appears to have extended observations into this region. The response observed after about 5 ms is not a simple extension of the initial response attributable to the middle ear. The oscillatory response decay time constant was found to change from approximately 1 ms to over 12 ms at about this time. The slowly decaying response conponent was present in all normal ears tested, but was not present in ears with cochlear deafness. This component of the response appears to have its origin in some nonlinear mechanism probably located in the cochlea, responding mechanically to auditory stimulation, and dependent upon the normal functioning of the cochlea transduction process. A cochlear reflection hypothesis received some support from these results.
Action potentials in the cat at low sound intensities: Thresholds, latencies, and rates of change
Authors: Price G. Richard
Published: October 2005

The interpretation of whole-nerve action potentials is a topic of increasing importance in both clinical and research settings. This effort has been hampered by a lack of data on the action potential that are theoretically interpretable and systematically measured over a wide range of frequencies and at low sound intensities. Therefore, the present study was designed to measure the thresholds, latencies, and rates of change in the whole-nerve action potential in response to constant-spectral-width tone pips at eight frequencies between 0.5 and 20 kHz in the cat ear. These quantities were calculated by a linear regression technique from round-window potentials in 28 normal ears. They were found to be consistently within approximately 18 dB of previously published behavioral measures, a difference attributable to temporal integration. The interanimal variability had a standard deviation of about 5 dB and the intra-animal variability was extremely low. The growth of amplitude across frequencies, the rate of change of latency with intensity changes, and the latency at threshold all demonstrated orderly relationships which are presented. The data were all consistent with contention that the potentials were being produced by a single population of cells located at a place consistent with the frequency of the eliciting tone. The methods used provide exceedingly stable measures and should be applicable in both clinical and research settings.
Linear prediction analysis of speech based on a pole-zero representation
Authors: Atal Bishnu S. , Schroeder M. R.
Published: October 2005

Speech analysis and synthesis by linear prediction is based on the assumption that the short-time spectral envelope of speech can be represented by a number of poles. An all-pole representation does not provide an accurate description of speech spectra, particularly for nasals and nasalized sounds. This paper presents a method for characterizing speech in terms of the parameters of a pole-zero model. In this method,an impulse response representing the composite filtering action of the glottal wave, the vocal tract, the radiation, and the speech recording system is first constructed from the speech signal.This impulse response is obtained by performing several stages of all-pole LPC analysis. The pole-zero parameters are determined from the impulse response by solving a set of simultaneous linear equations. The method, being noniterative, is very suitable for automatic analysis of speech. The method has been applied to real speech data and the results show that the speech spectra derived from the pole-zero model agree very closely with the actual spectra derived by direct Fourier analysis.
A mixed-source model for speech compression and synthesis
Authors: Makhoul John , Viswanathan R. , Schwartz Richard , Huggins A. W. F.
Published: October 2005

This paper presents an excitation source model for speech compression and synthesis that allows the degree of voicing to be varied continuously by mixing voiced (pulse) and unvoiced (noise) excitations in a frequency-selective manner. The mix is achieved by dividing the speech spectrum into two regions, with the pulse source exciting the low-frequency region and the noise source exciting the high-frequency region. The degree of voicing is specified by a parameter Fc, which corresponds to the cut-off frequency between the voiced and unvoiced regions. For speech compression applications, Fc can be extracted automatically from the speech spectrum and transmitted. Experiments performed with the new model indicate its power in synthesizing natural sounding voiced fricatives and in largely eliminating the ’’buzzy’’ quality of vocoded speech. A functional definition of buzziness and naturalness is given in terms of the model.
Acoustic determinants of phrase boundary perception
Authors: Streeter Lynn A.
Published: October 2005

How three supersegmental variables (amplitude, pitch contour, and duration pattern) influence phrase boundary perception was investigated in two studies. Listeners located the phrase boundary in ambiguous algebraic expressions, such as ’’(A plus E) times O’’ and ’’A plus (E times O).’’ In one experiment, two values of each of three variables (appropriate or neutral) were orthogonally varied, using linear predictive coding analysis–synthesis procedures. There was a total of eight manipulations for each expression. In the other, the three suprasegmental variables were exchanged between the two alternative meanings of an expression, yielding a total of eight manipulations for each expression. Results from the two studies were consistent in showing that listeners use all three cues, and just these three to parse such utterances. That is, it was possible to completely shift the meaning of an expression uttered with one meaning into its alternate meaning by exchanging all three variables. In both studies, the effects of duration pattern and pitch contour were additive in total proportion correct. Possible models of how listeners process pitch and duration information independently in making a parsing decision are discussed.
Longitudinal study of hearing in children: Baseline data concerning auditory thresholds, noise exposure, and biological factors
Authors: Roche A. F. , Siervogel R. M. , Himes J. H. , Johnson D. L.
Published: October 2005

Serial auditory thresholds are being recorded at six-month intervals from 224 children and youths aged 4–18 years. The data from the first year show girls have lower threshold levels than boys, especially from 12–17 years, and, in both sexes, those aged 12–17 years have lower thresholds than those aged 6–11 years. Median total noise exposure scores tend to be higher in boys than girls, especially after 10 years of age, but these scores are not significantly correlated with auditory threshold levels. The incidence of exposure to events associated with noise increases markedly in teenage boys and is related to auditory threshold levels. There are no significant associations between auditory threshold levels and responses to general health questions or attained stature, but there are associations with meatal abnormalities. There is suggestive evidence, particularly in girls, that rapid maturation is associated with lower threshold levels, especially at lower frequencies.
Acoustic bulk parameters in distributions of pair-correlated scatterers
Authors: Twersky Victor
Published: October 2005

We develop simple approximations for the bulk acoustic parameters associated with coherent waves in pair-correlated random distributions of scatterers small compared to wavelength, and indicate their relations to earlier forms. Our initial functional equation for the bulk index of refraction applies for dense gas and liquid-state statistics in terms of integral analogs of lattice sums involving appropriate pair-correlation functions. For small-spaced scatterers (average separation of closest neighbors small compared to wavelength) we obtain explicit closed forms for the radiation loss effects by reducing the integrals to simple correlation-packing functions based on the scaled-particle equations of state for impenetrable particles. For uncorrelated sparse distributions, the present results reduce to those obtained by elementary procedures for small perturbations in the properties of the imbedding medium. For random lattice-gas statistics (a model for uncorrelated distributions which takes into account the space-occupying property of the obstacles), the results reduce, in general, to those obtained before for scatterers excited by the coherent wave and radiating into the imbedding medium.
Stiffness gradient along the basilar membrane as a basis for spatial frequency analysis within the cochlea
Authors: Ehret Günter
Published: October 2005

Stiffness z of the basilar membrane of the house mouse against a displacement by sound was calculated from data on width and thickness of the membrane. Three functions of the kind log10z=ax+b were obtained which equally express the stiffness change in dependence on the locus x on the basilar membrane. These functions were compared with the one for frequency representation. The result is that the spatial distribution of displacement maxima for frequencies and of stiffness follows the same kind of place-dependent functions over a large portion of the basilar membrane. From this it can be concluded empirically that the frequency and stiffness (calculated from width and thickness of the basilar membrane) scales along the cochlea are generally proportional to each other and that stiffness is a dominant factor for the determination of the locus of the displacement maximum for a given frequency.
Exploratory laboratory studies of the relative aversiveness of traffic sounds
Authors: Cermak Gregory W.
Published: October 2005

Two experiments examined the acoustical correlates of traffic sound aversiveness. In experiment I all pairs of 13 45-s traffic sound recordings were presented; subjects chose the sound of each pair to which they would rather be exposed and judged the relative similarity of the sounds. The energy equivalent sound level, Leq, accounted for choice and similarity judgments better than any other noise index, and there was no substantial improvement in ability to account for subjective judgments when other indices were used in conjunction with Leq. In experiment II subjects judged the same sounds which had been made equal in Leq level. Responses were nonrandom, showing that Leq is not the only subjectively important information in traffic sounds, but no acoustical measure employed in the study captured that information. Instead, two subjective measures of information content accounted best for the data of experiment II. Response data for the equal Leq sounds were less structured than for the sounds differing in Leq. The data of the two experiments were statistically related; it is argued that the data sets were related via the measure of information content. Experiment I replicated a previously reported study, while experiment II failed to replicate the results of a second study.
Adaptation, saturation, and physiological masking in single auditory-nerve fibers
Authors: Smith R. L.
Published: October 2005

Results are reviewed concerning some effects, at a units’s characteristic frequency, of a short-term conditioning stimulus on the responses to perstimulatory and poststimulatory test tones. A phenomenological equation is developed from the poststimulatory results and shown to be consistent with the perstimulatory results. According to the results and equation, the response to a test tone equals the unconditioned or unadapted response minus the decrement produced by adaptation to the conditioning tone. Furthermore, the decrement is proportional to the driven response to the conditioning tone and does not depend on sound intensity per se. The equation has a simple interpretation in terms of two processes in cascade—a static saturating nonlinearity followed by additive adaptation. Results are presented to show that this functional model is sufficient to account for the ’’physiological masking’’ produced by wide-band backgrounds. According to this interpretation, a sufficiently intense background produces saturation. Consequently, a superimposed test tone causes no change in response. In addition, when the onset of the background precedes the onset of the test tone, the total firing rate is reduced by adaptation. Evidence is reviewed concerning the possible correspondence between the variables in the model and intracellular events in the auditory periphery.
A corrected ray theory for acoustic velocimetry
Authors: McCartney Michael L. , Mudd Courtney P. , Livengood Ross D.
Published: October 2005

Acoustic velocimeters for fluids traditionally assume a straight ray between transmitter and receiver, and use acoustic phase velocity for calculating fluid speed or velocity from upstream and downstream transit times. Corrected ray theory which uses group or signal velocity yields a relation between fluid velocity and differential transit time which differs from the traditional expressions. Fluid velocities calculated from differential transit times in the range 0.1–50 μs over a short path (5 cm) in air differ by as much as 1.4% using the traditional and corrected ray methods.
Acoustic emission and transient waves in an elastic plate
Authors: Pao Yih-Hsing , Gajewski Ralph R. , Ceranoglu Ahmet N.
Published: October 2005

To study the mechanism of the source of acoustic emission, we analyze the transient waves which are generated by four kinds of point sources, a single force, double force, and center of dilatation, all inside an infinite plate, and a single force on the surface of the plate. Some of these forces or a combination of them could be used to model the dynamic process of material defects. The analysis is based on the generalized ray theory and Cagniard’s method. Transient solutions are obtained by evaluating the ray integrals with a complex algorithm. Numerical results are shown for receivers that are located at a distance up to six plate thickness, and for a duration less than ten transit time for a P-wave to cross the thickness of a plate.
Acoustical designing for performers
Authors: Shankland Robert S.
Published: October 2005

The normal procedure in acoustical designs usually emphasizes audience acceptance. This approach often results in unfavorable acoustical conditions for performing artists, both instrumental and vocal. The imbalance occurs form neglect of the musicians’ need for mutual communication, and too great an emphasis on achieving ’’optimum’’ reverberation conditions. There have been notable examples of halls meeting accepted reverberation criteria which have nevertheless proved to be unsatisfactory, and many of these gave trouble because of performance difficulties as transmitted to the audience. Conversely, reverberation conditions can differ considerably from the norm, and still provide a satisfactory hall if the stage is properly designed. Study of a variety of halls strongly suggest that an essential requirement for music is that conditions should be suitable for performers. Architectural designs that provide ample sound reflecting and diffusing structures on stage to enable artists to hear each other well, blend the sound, and achieve favorable ’’local reverberation’’ are usually judged to be excellent by both performers and audience. This essential result can be achieved even in rooms which depart appreciably from standard reverberation time criteria.
Comments on ’’Conformal array beam patterns and directivity indices’’ [J. Acoust. Soc. Am. 63, 841–847 (1978)]
Authors: Kelly J. G. , Sullivan E. J. , Salisbury J. I.
Published: October 2005

Several comments are presented in response to an article by Frank, Kesner, and Gruen which concern their calculation of the Directivity Index (DI) of a particular conformal array. In addition, independent results of calculations of the DI for a similar conformal array (elements distributed on a conical surface) are presented. These results include optimal (maximal DI) weighting of the array’s elements, as well as comparison with an appropriate planar array serving as a reference.
Lamb wave device for amplitude modulation
Authors: Shinoda Yoshiaki , Toda Kohji
Published: October 2005

Experimental results are presented for the influence of electrical termination affecting the performance of a transducer for Lamb wave devices. The transducer consists of three electrode groups, including one on the bottom surface. The others are interdigital electrode groups on the top surface and are terminated with resistances, respectively. The extraction of acoustic energy from the transducer depends strongly upon the values of load resistances connected with two interdigital electrode groups. By using this fact, a device for amplitude modulation is demonstrated.
A study of the effects of ocean bottom roughness on low-frequency sound propagation
Authors: Rutherford Steven R. , Hawker Kenneth E. , Payne Susan G.
Published: October 2005

The effects of bottom (water–sediment interface) roughness on low-frequency sound propagation is examined using a theory of scattering based on boundary conditions applied at the mean boundary. Boundary roughness effects on normal mode attenuation coefficients are examined for two sediment types and two frequencies. For the cases studied it was found that, for fixed bottom roughness, the attenuation coefficients increased with frequency as expected, but showed insensitivity to the correlation length of the bottom roughness. It was also determined that, for fixed bottom roughness, a harder sand-type bottom produced more scattering attenuation than a clay-type bottom.
On the classification of underwater acoustic signals. II. Experimental applications involving fish
Authors: Deuser Larry M. , Middleton David , Plemons Terry D. , Vaughan J. Kenneth
Published: October 2005

In a previous paper (Part I) a general approach to adaptive classification has been presented. That approach is applied here (Part II) to classification of waveforms obtained in a number of illustrative experiments. Experiments at 116 kHz (in the ARL Test Tank Facility) have provided backscattered waveforms (echoes) from known types of scatterers, randomly located and with random acoustic cross sections. Scatterers of primary interest here are a variety of small fish. Signals which form competing categories are scattering from seaweed (aquarium grass), surface reverberation, and artifacts (glass bottles). The data obtained are representative of three classification problems that have some practical significance in underwater acoustics. These three problems require distinguishing between the received signals which result from scattering by: (1) fish versus air–water surface, seaweed, and/or artifacts; (2) fish and air–water surface versus air–water surface only; and (3) ’’low density’’ versus ’’medium density’’ versus ’’high density’’ of fish. In each case the waveforms are analyzed and features appropriate to the classification task are extracted from a portion of the data. These features are then used to design a classification algorithm for the environmentally adaptive approach and for its conventional counterpart. These algorithms are then used on the remaining data to make classifications. The superiority and usefulness of the proposed environmentally adaptive approach is demonstrated here by the noticeable improvement in quantitative classification which results from the exploitation of environmental state data.
A rapid approximation to optimal array processing for the case of strong localized interferences
Authors: Keating P. N.
Published: October 2005

The application of adaptive beamforming to the problem of a finite number of strong localized interferences is addressed. It is shown that (a) the general, complex optimal array processing problem reduces to a simpler problem in this case: specifically, the problem of optimizing J(N−1) free parameters (where N is the number of array elements and J is the number of frequency bands of interest) is formally reduced to one of optimizing only n free parameters, where n is the number of interferences; (b) the problem of signal cancellation which exists in classical optimal processing, where the filter output power is minimized, can be avoided by minimizing the total power in all directions, instead; (c) simulations using an existing target scenario (the Frost scenario)[Proc. IEEE 60 926–935 (1972)] indicate that methods based upon the above findings are at least as good as classical optimal processing for appropriate target scenarios. This paper can also be regarded as providing a relatively rigorous basis for methods which were developed earlier [J. Acoust Soc. Am. 59 106–111 (1976)] on more intuitive grounds, and as relating these methods to the better-known classical optimal processing techniques.
Narrow-band AP latencies in normal and recruiting human ears
Authors: Eggermont J. J.
Published: October 2005

Derived narrow-band action potential latencies increase monotonically with decreasing central frequency, and can be interpreted as reflecting the traveling wave delay in the cochlea. It was found that, for recruiting human ears with average flat hearing losses around 40 dB, this accumulating latency increase was smaller than for normal ears. A comparison of 15 normal ears and 37 recruiting ears showed, however, that in only half of the recruiting ears this difference was significant. These recruiting ears were therefore divided in two groups based on the waveform of the narrow-band action potential AP, which correlated well with the subdivision according to latency. The findings have been explained on the basis that latency of the narrow-band APs is not determined solely by the mechanical traveling-wave delay, but also by the response time of the (second?) cochlear filter. When this filter broadens, one expects a decrease in its impulse response time. Since this impulse response time actually depends on the sum of the high- and low-frequency slope values of the cochlear filter, one expects only a latency decrease when the steep high-frequency slope also becomes more shallow. A support for the influence of the response times of the cochlear filter is found in the narrow-band AP latencies for restricted cochlear losses (e.g., in a 4-kHz noise dip). It appears that the latency in that area actually is shorter than for the higher central frequencies, a fact which cannot be explained solely on the basis of a traveling wave phenomenon.
The relationship between collagen and ultrasonic attenuation in myocardial tissue
Authors: O’Donnell M. , Mimbs J. W. , Miller J. G.
Published: October 2005

The relationship between ultrasonic attenuation and collagen content is examined in hearts from normal dogs and in hearts from dogs subjected to ischemic injury by coronary occlusion as an approach toward elucidating the physical mechanisms responsible for the attenuation of soft tissue. Increased ultrasonic attenuation is shown to correlate well with increased collagen concentration determined biochemically in regions of ischemic injury studied 2, 4, and 6 weeks following occlusion. Extrapolation of the experimentally determined relationship between attenuation and collagen concentration suggests that collagen is responsible for not more than 15% of the attenuation observed in normal myocardium. These results indicate that collagen appears to be the principal determinant of the elevated attenuation detected in regions of myocardial infarction, but is apparently not the primary determinant of the attenuation of normal myocardium.
Numerical spatial marching techniques in duct acoustics
Authors: Baumeister K. J.
Published: October 2005

A numerical method is developed that could predict the pressure distribution of a ducted source from farfield pressure inputs. Using an initial value formulation, the two-dimensional homogeneous Helmholtz wave equation (no steady flow) is solved using explicit marching techniques. The Von Neumann method is used to develop relationships which describe how sound frequency and grid spacing effect numerical stability. Stability considerations limit the approach to high-frequency sound. Sample calculations for both hard and soft wall ducts compare favorably to known boundary value solutions. In addition, assuming that reflections in the duct are small, this initial value approach is successfully used to determine the attenuation of a straight soft wall duct. Compared to conventional finite difference or finite element boundary value approaches, the numerical marching technique is orders of magnitude shorter in computation time and required computer storage and can be easily employed in problems involving high-frequency sound.
Measurement of fundamental and second harmonic pressures in the field of a circular piston source
Authors: Moffett Mark B.
Published: October 2005

Measurements were made at various ranges between 1 and 131 m of the fundamental and second harmonic components of a finite-amplitude sound wave produced by a 10.2-cm diam projector driven at 450 kHz in fresh water. Various levels were used, so that nonsaturated, as well as saturated, conditions were obtained. The nonsaturated nearfield levels are in good agreement with the theory of Ingenito and Williams [J. Acoust. Soc. Am. 49, 319–328 (1971)], while the nonsaturated farfield levels agree with the theory of Safar [J. Sound Vib. 13, 1–7 (1970)]. Because the second harmonic component becomes locally generated at ranges of the order of 1/α (α=fundamental absorption coefficient), the Safar theory can be modified to fit the saturated levels at such ranges by correction of the fundamental levels for finite-amplitude losses. The second harmonic beam patterns at such ranges closely approximate the square of the measured fundamental beam patterns.
Excitation of nonlinear acoustic resonances by unsteady heat input
Authors: Whitehead D. S. , Holger D. K.
Published: October 2005

Experiments have been carried out on a cylindrical cavity containing hydrogen, the unsteady heat input being supplied by a modulated electric arc. A nonlinear acoustic theory due to Chester [J. Fluid Mech. 18,44–64 (1964)] has been extended to deal with unsteady heat input. the experimental resonance curves are found to be highly distorted, and this distortion is not predicted by the nonlinear theory. The damping appears to be about double the theoretical damping, and the peak amplitude is less than half the theoretical prediction. An approximate theoretical criterion for the appearance of shock waves is derived. No shock waves were observed in the experiments, and this is shown to be consistent with the theoretical criterion.
An experimental investigation of acoustic radiation from a source inside a large turbulent free jet
Authors: Ozkul A. , Yu J. C.
Published: October 2005

An experiment has been conducted in NASA Langley’s free-jet anechoic facility to assess the effect of a free-jet shear layer on sound radiation from an acoustic source placed inside the jet: The nozzle diameter was 1.22 m and operated at an exit velocity of 35 m/s. Two different types of sources were used; one was a compact source with a nearly uniform radiation pattern, the other was a noncompact source with highly directional radiation pattern. The acoustic source was driven by by pure tone and 1/3-octave band white noise. Acoustic measurements were made both inside the jet flow in the potential core region and outside the jet in the acoustic farfield. The effects of mean flow convection and mean shear refraction on sound radiation were determined. The experimental results compared favorably with analytical predictions. The effect of free-jet turbulence on sound scattering was found to be insignificant.
Isolation of the resonant component in acoustic scattering from fluid-loaded elastic spherical shells
Authors: Murphy J. Diarmuid , George Jacob , Nagl Anton , Überall Herbert
Published: October 2005

We investigate the process of resonance excitation of a spherical, fluid (or gas) filled elastic shell imbedded in another fluid, in the course of scattering of a plane incident sound wave from the shell, using the recently developed formalism of resonance scattering theory. Numerical studies are performed for air-filled aluminum shells immersed in water. We isolate the resonant component in the scattering amplitude by subtracting a nonresonant ’’intermediate’’ background, thus exhibiting the pure resonance peaks in the frequency region 0<ka?100, for shell thicknesses (inner-to-outer ratio) b/a=0.2, 0.7, and 0.9, and for the normal modes up to n=3. It is found that up to b/a=0.7, the background amplitude is adequately represented by that of a rigid body, but that above b/a=0.9, intermediate-background theory must be used. A physical explanation of the existence of the shell resonances is presented in terms of elastic circumferential waves created on the shell during the scattering process; each of these will build up to a resonance in the nth mode if n+1/2 of its wavelengths span the circumference of the sphere, the half-integer stemming from the fact that the circumferential wave loses 1/4 wavelength at each of the convergence points at the north and south pole.
Measurements of acoustic backscattering from very rough water surfaces
Authors: Boehme Hollis
Published: October 2005

Measurements were made of the reverberation resulting from surface backscattering of incident monochromatic acoustic waves at operating frequencies of 175 and 455 kHz. These measurements were used to determine the frequency shift and frequency spreading of the backscattered acoustic field. The frequency shift was found to be in qualitative agreement with simple models of the surface scattering mechanism except that the magnitude of frequency shift was proportional to wind speed only for the lower range of wind speeds. The frequency spreading was observed to increase with decreasing grazing angle in contrast with simple model predictions. Asymmetry in the spectrum envelopes, inferred from the measurements made, is attributed to the wide beamwidth in the aximuthal plane of the sonar used.
A dynamic model for elastic wave propagation in a material containing rigid spheres
Authors: Beltzer A.
Published: October 2005

For prediction of the low-frequency average response of material containing randomly distributed rigid spheres, the material is replaced by an effective homogeneous medium. The parameters of this medium are determined from the conditions that its specific deformation energy, attenuation and impulse are equal to those of the material of interest. The solution is applicable to the case of reinforcement by rigid ’’light’’ inclusions, among others.
A normal mode theory of acoustic Doppler effects in the oceanic waveguide
Authors: Hawker Kenneth E.
Published: October 2005

This paper considers the problem of computing the acoustic field generated by a moving point source. In particular, the acoustic field is obtained in terms of the normal modes of a horizontally stratified ocean. The source motion is assumed to be uniform (unaccelerated), but is not restricted to a path radial to the receiver. The structure of the Fourier inversion integral is carefully analyzed and an evaluation is carried out by the method of stationary phase. The stationary phase point is explicitly computed as an expansion in powers of the ratio of the source speed to the mode group velocity. The resulting expression for the velocity potential is examined for Doppler effects for both instantaneous (modal) Doppler as well as Doppler determined by a finite bandwidth Fourier transform.
Measurements of the radiation impedance presented to a source in a reverberant room containing a rotating diffuser
Authors: Bies David Alan , Hansen Colin H.
Published: October 2005

The radiation impedance of a stationary sound source mounted in the side wall of a reverberant chamber has been investigated using three separate sources over the frequency range from 100 to 2000 Hz. The effect of a rotating diffuser on the measured radiation impedance has been investigated over a range of diffuser rotational speeds up to 50 rpm. The measurements show that a rotating diffuser is necessary to achieve an average radiation impedance equal to or approaching free field, and a rotational speed of between 20 and 30 rpm is sufficient for this purpose. The measurements suggest that the average radiation impedance may in part be dependent upon the source size and that the rotating diffuser has more effect on the radiation impedance for large sources.
Source extraction in a random medium
Authors: Vasholz David P.
Published: October 2005

A general formulation of the problem of extracting information about nontransient sources immersed in a randomly fluctuating medium is presented. The formulation is based upon a Green’s function approach in which the medium is treated as a random linear system. It is shown that the problem may be cast into two possible forms, each involving an integral equation the solution of which describes the locations and spectral content of all sources. One of these integral equations is time independent and consists exclusively of deterministic quantities. The other equation is time dependent, consists of stochastic as well as deterministic quantities, and contains considerably more detail. Approximate solutions to the second equation enable one to study image undulations as explicit functions of time. Examples are presented which illustrate some of the difficulties induced by the medium fluctuations when one attempts to solve the basic integral equations.
Selective adaptation effects in infant speech perception paradigms
Authors: Miller Cynthia L. , Morse Philip A.
Published: October 2005

The present studies were conducted to explore the possible role of selective adaptation in infant speech perception. In the first study, in which the growth of adaptation was examined by presenting adult listeners with successive blocks of 20 repeating stimuli, reliable adaptation effects were observed after only 80 stimulus presentations. In addition, recovery following adaptation was relatively rapid and complete by the end of a postadaptation identification sequence. Experiment II constituted a more direct investigation of the possible role of adaptation in infant speech perception in which actual protocols from heart-rate (HR) and non-nutritive high-amplitude sucking (HAS) infant testing sessions were presented to adult listeners. Reliable adaptation effects were obtained within the HAS protocol, but not within the HR format. This pattern of results was consistent with that observed in experiment I. The implications of these adult adaptation results for the processes underlying the infant’s responsiveness to these stimuli were discussed.
Near and farfield of strip-shaped acoustic radiators
Authors: Drost C. J.
Published: October 2005

The acoustic radiation produced by baffled flat strip-shaped sources of infinite length is treated in detail. The nearfield intensity distribution, nearfield to farfield transition, and cylindrical farfield radiation is calculated for homogeneous radiator surface excitation; such beams are shown to partially focus at their last maximum of intensity. Farfield radiation is calculated for radiators with a Gaussian surface velocity distribution, for shaded transducers, and for arrays of strip-shaped sources. The use of such radiators in Doppler flow measuring systems is discussed.
Giant monopole resonances in the scattering of waves from gas-filled spherical cavities and bubbles
Authors: Gaunaurd G. , Scharnhorst K. P. , Überall H.
Published: October 2005

Continuing our previous work on viscoelastic scattering of p waves from fluid-filled spherical cavities in sound-absorbing materials, we now perform the theoretical analysis needed for the complete study of the monopole mode of vibration. Our approach is based on the Breit–Wigner formulation of nuclear scattering theory, and from it we show how the scattering amplitudes consist of two parts, the smooth background of the evacuated cavity and the resonance contribution of the filler fluid. We present a complete analytical study of the giant fundamental resonance and its overtones in the monopole case. The results are then particularized to the Rayleigh region and also to the case of evacuated cavities in lossless rubber and to gas bubbles in water, recovering and extending previous results available in the literature. Studying the sound pressure level at the center of air-filled cavities in lossy materials, we quantitatively determine how absorption shifts the resonance peaks and broadens their width. Using our theory we find that the width of the resonance peaks depends linearly on the resonance frequencies, and we show how this important result can be used to determine the shear absorption parameter of viscoelastic materials. We also find that the giant monopole resonance for air-filled cavities in rubber contains a contribution from the shear waves in the cavity wall and another from the resonance oscillations of the air-filling in a 15:1 ratio, for this particular material combination. We display numerous plots, some obtained from the analytic monopole formulas developed here, and some numerically obtained by computer for dipoles and quadrupoles. Finally, we show graphs of the summed scattering amplitudes fpp and fps accounting for the first twenty multipole contributions, and the dominance of the monopole term emerges again from this result. We have assumed ’’weak’’ absorption to simplify the analytical treatment, but any viscosity level can be handled by computer using this method.
Piston radiator: Some extensions of the theory
Authors: Greenspan Martin
Published: October 2005

Those results of the theory of the baffled, uniform-piston radiator that can be calculated exactly are extended to some other cases, especially the simplest case of a simply supported radiator, the simplest case of a clamped-edge radiator and a Gaussian radiator. It is also shown that from the solution to a problem with boundary conditions framed in terms of velocity, the solution to a corresponding problem, having boundary conditons framed in terms of pressure, can be obtained very easily.
Prediction of the sound field radiated from axisymmetric surfaces
Authors: Meyer W. L. , Bell W. A. , Stallybrass M. P. , Zinn B. T.
Published: October 2005

A general analytical method for determining the radiated sound fields from axisymmetric surfaces of arbitrary cross section with general boundary conditions is developed. The method is based on an integral representation for the external solutions of the Helmholtz equation. An integral equation is developed governing the surface potential distribution which gives unique solutions at all wavenumbers. The axisymmetric formulation of the problem reduces its solution to the numerical evaluation of line integrals by Gaussian quadrature. The applicability of the solution approach for both a sphere and finite cylinder is demontrated by comparing the numerical results with exact analytical solutions for both discontinuous and continuous boundary conditions. The method is then applied to a jet-engine-inlet configuration and the computed results are in good agreement with exact values.
Wide-frequency response of type J-9 underwater sound projector in a typical experimental tank
Authors: Curtis George D.
Published: October 2005

The characteristics and use of the Type J-9 transducer at frequencies up to ten times its calibrated range are discussed, and described quantitatively. Problems and precautions in using this and other projectors in reverberant experimental test tanks are covered. Examples of temporal, spatial, and directive effects are presented. Recommendations for effective use of high-frequency sound projectors such as this, experiment design, and valid interpretation of results are made.
Precision ac-voltage-level measuring system for acoustics
Authors: Wong G. S. K.
Published: October 2005

A precision acoustical measuring system is described. By means of an attenuation compensation technique, errors due to attenuators are reduced to a second order of magnitude. Systematic errors are analyzed in depth. Experimental verification indicates that the maximum system error over a 120-dB dynamic range is within ±0.1 dB.
Laser-induced Rayleigh waves in aluminum
Authors: Ledbetter H. M. , Moulder J. C.
Published: October 2005

A bulk aluminum-alloy irradiated with a Q-switched Nd-glass laser shows three distinct elastic waves: longitudinal, transverse, and Rayleigh (surface) waves. The elastic-wave velocities agree with those measured by more familiar methods.
Estimating bearing when the source is endfire to an array
Authors: Hinich Melvin J.
Published: October 2005

Consider the problem of estimating the direction of arrival of a plane wave using a linear array when the source is endfire to the array. An estimator of ϑ, the direction of arrival with respect to the array axis, is presented with a small mean square error when ϑ is small and the number of sensors or the array gain is large.
Comparison of WKB calculations and experimental results for three-dimensional cochlear models
Authors: Steele Charles R. , Taber Larry A.
Published: October 2005

The WKB asymptotic method is applied to the calculation of cochlear models with square scala cross section, for which the fluid motion is fully three dimensional. The analysis begins with the exact solution for wave propagation in a duct with constant properties. This solution is somewhat tedious but straightforward, since it requires a Fourier series expansion across the duct. Then with the formulation of Whitham [Linear and Nonlinear Waves (Wiley, New York, 1974)], the approximate solution is readily generated for the duct with properties which vary slowly along the length. Numerical calculations are carried out for the experimental models of Cannel [Ph.D. thesis, Univ. of Warwick (1969)] and Helle [Dr.-Ing. disser.,Thechnische Univ., Müchen (1974)] who furnish quantitative details of both ’’basilar membrane’’ response and model parameters. Without any free parameters for adjusting, the present WKB solution shows quite satisfactory agreement with the experimental model results. Computer time is reasonable; the calculation of displacement envelope and phase at a number of stations along the cochlea for a given frequency requires only one second of CPU time. Thus the credibility and practicality of the approach is established for the investigation of yet more realistic and more elaborate cochlear models.
Pedestal experiments: Amplitude versus power
Authors: Jeffress Lloyd A.
Published: October 2005

Data from three pedestal experiments show a uniformity of improvement in detection as signal duration increases to fairly long durations—an improvement close to 3 dB per doubling. They also show that an increase of 20 dB in pedestal level requires an increase of only 10 dB in signal level for equal detection. Two formulas are developed, one empirical and one based on a simple Poisson counting model, that predict the effect on detection of signal duration, pedestal level, and the quadrature addition of a signal.
Role of distinctive features in dichotic perception of 21 English consonants
Authors: Hayden Mary Ellen , Kirstein Emily , Singh Sadanand
Published: October 2005

The role distinctive features played in the identification of 21 dichotically presented syllable initial English consonants was evaluated. Results were analyzed for the entire stimulus set and for various intra- and inter-manner class comparisons. Consistent with previous dichotic studies of stops alone, stops as a subgroup showed a large right ear advantage, a high incidence of blend errors, and greater accuracy in identification when the competing stimuli contrasted on one (rather than two) distinctive features. Results for manner classes other than stops, for inter-manner comparisons and for the total stimulus set indicated increased correct identification with increasing numbers of distinctive feature differences between the two syllables. Analysis of error patterns revealed that, in addition to the stops, continuants, and stop–continuant, stop–affricate, and stop–nasal pairs revealed significant numbers of blend errors. Error responses also showed a tendency for unmarked feature specifications to predominate significantly over marked feature specifications. Finally, the magnitude of the right ear advantage varied significantly as a function of manner class, but not as a function of number of feature contrasts.
Transient response of two fluid-coupled spherical elastic shells to an incident pressure pulse
Authors: Huang H.
Published: October 2005

The transient response of a system of two initially concentric spherical elastic shells coupled by an ideal fluid and impinged upon by an incident plane pressure pulse is analyzed. The classical techniques of separation of variables and Laplace transforms are employed for solving the wave equations governing the fluid motions and the shell equations of motion. A scheme of iterative convolution was devised for the inversion of the Laplace transforms that facilitates the calculation of accurate transient solutions of the response of the shells. A sample calculation of shell responses was performed and results are compared to the case in which the outer shell is absent. This set of results demonstrates that a thin outer shell tends to be transparent to the incident pulse.
Diffraction by a thick slitted screen
Authors: Tinti Stefano
Published: October 2005

The diffraction induced on a plane wave by an aperture in a thick rigid screen is investigated through the use of an expedient numerical method based upon Green’s function theory, quite convenient when the slit is few wavelengths large. The results show that the screen thickness is a parameter widely influencing the diffracted wave patterns. Particularly, it has been found that the transmission factor curves are characterized by resonance peaks. By thickening the screen, sharper and stronger peaks are obtained. Further, if resonances involve slit transversal modes, the farfield energy angular distribution undergoes strong variations when the wavenumber is moved from one to the other side of the peak.