bluuebunny/crossref_metadata_2025 huggingface dataset:
Complex eigenfrequencies of rigid and soft spheroids
Authors: D’Archangelo J. M. , Savage P. , Überall H. , Yoo K. B. , Brown S. H. , Dickey J. W.
Published: October 2005

The complex eigenfrequencies of impenetrable or penetrable target objects form a pattern which is characteristic for a given target, as far as its shape and/or composition is concerned; they manifest themselves as poles (resonances) in the amplitude of waves scattered from the object. We here obtain the eigenfrequency patterns of acoustically rigid and soft spheroids in the complex frequency plane, and study their displacements when the eccentricity of the spheroids is varied. The eigenfrequencies were obtained numerically by subjecting spheroidal wavefunctions to the Neumann or Dirichlet boundary conditions, respectively.
A multiple scattering theory for elastic wave propagation in discrete random media
Authors: Varadan V. K. , Ma Y. , Varadan V. V.
Published: October 2005

A multiple scattering theory for elastic wave propagation in a discrete random medium is presented. A self-consistent multiple scattering formalism using the T matrix of a single scatterer in conjunction with the quasicrystalline approximation (QCA) and a self-consistent pair correlation function is employed to study the phase velocity and coherent attenuation of elastic waves by a random distribution of cavities and elastic inclusions embedded in an elastic matrix. Both uniform and Gaussian size distributions are assumed. The theoretical results obtained in this study are shown to be in excellent agreement with experimental observations.
Experimental determination of the variation of specific heat ratio in air with humidity
Authors: Wong George S. K. , Embleton Tony F. W.
Published: October 2005

This paper describes a precise and direct acoustical method for experimental verification of the variation of γ in air with humidity. The experimental results are within 100 to 250 ppm of the theoretical predictions. The experimental arrangement may be used to assess the specific heat ratio of other gases or gas mixtures by a comparison method.
Force on a heated sphere in a horizontal plane acoustic standing wave field
Authors: Leung Emily W. , Wang Taylor G.
Published: October 2005

The force on a heated sphere in a horizontal plane acoustic standing wave field is the subject of this investigation. The heated sphere produces a thermal gradient in the resonance chamber. The force on the sphere in a direction perpendicular to that of gravity is measured. This force is enhanced in the region near the pressure node, and is weakened in the region near the pressure antinode. Measurements of the force on a heated sphere with sound pressure levels between 148 and 156 dB are presented.
Numerical studies of the spectrum of low-intensity ultrasound scattered by bubbles
Authors: Eatock Brian C. , Nishi Ronald Y. , Johnston Gordon W.
Published: October 2005

The magnitude of the nonlinear effect in the scattering of ultrasound by nitrogen bubbles in water is examined numerically, for ultrasonic frequencies and amplitudes typical of diagnostic medical devices, to determine the suitability of this effect for the detection of bubbles in blood or tissue for application in decompression research. Numerical solutions of the modified ‘‘Rayleigh’’ equation, including the effects of acoustic, thermal, and viscous damping, and the dependence of the polytropic exponent on frequency are presented for pulsed ultrasound. For the chosen conditions, it is shown that nonlinear scattering is significant only for the population of bubbles which are smaller than, or close to, resonance size, and primarily for those bubbles that are one-half resonance size.
Diffraction of a baffled dipole: Frequency dependence
Authors: McInerny S. A. , Meecham W. C. , Ngo T. V. , Liu S. C.
Published: October 2005

In the theory of trailing edge noise there has been some disagreement concerning the correct power dependence of the radiated acoustic intensity on the flow velocity. Different theoretical investigations, incorporating various implicit assumptions, viz., the turbulence intensity depends upon the Mach number, and using different forms of the Green’s function for the problem, have led to fifth and sixth power dependencies. Experimental evidence supports the fifth power dependence, but has not provided information on the validity of the various assumptions underlying the theory. This paper presents the results of experiments performed in the UCLA Aerosonics Laboratory that confirm the diffraction effects predicted by MacDonald’s form of the Green’s function for the baffled field. Using this Green’s function, Ffowcs-Williams and Hall [J. Fluid Mech. 40(4), 657–670 (1970)], Chase [J. Acoust. Soc. Am. 70, 1531–1533 (1981)], and Hayden et al. [NASA CR-145073 (1976)] have predicted the acoustic intensity of noise generated by flow over a trailing edge to be proportional to the fifth power of the flow velocity.
Current and current shear effects in the parabolic approximation for underwater sound channels
Authors: Robertson J. S. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

The effect of currents on the acoustic pressure field in an underwater sound channel is investigated. Based on fundamental fluid equations, model equations are formulated for sound pressure while including nonuniform currents in the source–receiver plane. Application of parabolic-type approximations yields a collection of parabolic equations. Each of these is valid in a different domain determined by the magnitudes of current speed, current shear, and depth variation of sound speed. Under certain conditions, it is possible to interpret current effects in terms of an effective sound speed. Using this effective sound speed in an existing numerical code, we examine sound speed in a shallow water isospeed channel with a simple shear flow and a lossy bottom. It is found that even small currents can induce very substantial variations in relative intensity. The degree of variation depends upon current speed, source and receiver geometry, and acoustic frequency. Particular emphasis is placed on intensity-difference predictions in reciprocal sound transmissions in the presence of an ocean current.
Wave reflection from a sediment layer with depth-dependent properties
Authors: Stern M. , Bedford A. , Millwater H. R.
Published: October 2005

The reflection of plane acoustic waves at the water–sediment interface is analyzed. The sediments are modeled using Biot’s equations with depth-dependent coefficients. Computations are made of the reflection coefficient as a function of the incident wave frequency and angle for representative sediment properties. The results are compared to those obtained by modeling the sediments as a homogeneous viscoelastic material and as a viscoelastic material with depth-dependent properties. It is shown that both of these models yield predictions of the reflection coefficient that can differ substantially from the Biot model.
Marine sediment acoustics
Authors: Stoll Robert D.
Published: October 2005

New field and laboratory data indicate that the assumption of a constant ‘‘Q,’’ or equivalently, an attenuation coefficient, α, that depends on the first power of frequency, is unacceptable in the case of nearly all marine sediments. The fluid component of marine sediments causes various forms of viscous damping that are always frequency dependent. In coarser sediments, overall motion of the fluid field relative to the skeletal frame, causes a strong frequency dependence that depends on permeability and the tortuosity of the intergranular pores. In the finer sediments, local viscous losses occur near the intergranular contacts producing a viscoelastic response similar to the ‘‘squeeze film’’ phenomenon that is well known in lubrication theory. Both kinds of viscous damping, as well as frictional losses at the grain contacts, can be included in the generalized Biot model which has been used to describe the acoustical response of marine sediments. In this paper we summarize recent field data which illustrate the wide spread of ‘‘Q’’ values that are to be expected and present some new experimental data that demonstrate both kinds of viscous damping mentioned above. Finally we use the model to estimate the response of a p wave based on laboratory measurements of torsional vibrations. A simple mathematical model is used to establish the connection between these two modes of motion.
Wave propagation in a rod with an arbitrarily shaped outer boundary and a cylindrical cavity of arbitrary shape
Authors: Nagaya Kosuke , Watanabe Tatsuya
Published: October 2005

This paper presents a method for solving wave propagation problems of an infinitely long bar of arbitrary cross section with an arbitrarily shaped cylindrical cavity. The boundary conditions of the inner and the outer arbitrarily shaped surfaces of the bar are satisfied by use of the Fourier expansion collocation method. The analysis derives the frequency equation for determining the phase velocities of the bar of arbitrary cross section with the cavity. As an example numerical calculations have been carried out for elliptical and hexagonal cross-section bars with various cavities.
Free vibration of an oblique circular cylindrical shell
Authors: Irie Toshihiro , Yamada Gen , Muramoto Yasushi
Published: October 2005

An analysis is presented for the free vibration of an oblique circular cylindrical shell. For this purpose, the shell is transformed into a circular cylindrical shell of unit axial length by a transformation of variables. The deflection displacements of the transformed shell are expressed in a series of the products of the eigenfunctions of an axial beam and the trigonometric functions of angular coordinate. The dynamical energies of the shell are evaluated, and the frequency equation is derived by the Ritz method. This method is applied to free-clamped oblique shells truncated at the free edge, and the natural frequencies and the mode shapes are calculated numerically up to higher modes.
Resolution enhancement of backward propagated images by wavefield orthogonalization
Authors: Lee Hua
Published: October 2005

Backward propagation is a convolution-type reconstruction algorithm designed for coherent holographic imaging which is commonly performed by frequency-domain filtering. When the size of the receiving apertures is small, image resolution is degraded due to the uncertainty caused by the incomplete measurement of the wavefield in addition to the limitation corresponding to the narrow spatial-frequency bandwidth. In this paper, the ambiguity of target identification is regarded as a result of nonorthogonal correlations of the wavefield signatures corresponding to distinct target locations. A resolution enhancement algorithm is presented by wavefield orthogonalization to uncorrelate the wavefield patterns to achieve resolution improvement on backward propagated images.
Lateralization of low-frequency, complex waveforms: The use of envelope-based temporal disparities
Authors: Bernstein Leslie R. , Trahiotis Constantine
Published: October 2005

Several recent investigations suggest that listeners either cannot or do not use envelope-based interaural temporal disparities (ITDs) to lateralize low-frequency sounds [G.B. Henning, J. Acoust. Soc. Am. 68, 446–453 (1980); G.B. Henning and J. Ashton, Hear. Res. 4, 185–194 (1981); G.B. Henning, Hear. Res. 9, 153–172 (1983)]. We believe listeners in those studies may have been unable to process envelope-based ITDs principally because of the types of stimuli utilized. In this study we employed an acoustic ‘‘pointing’’ task in which listeners varied the interaural intensitive difference of a 500-Hz narrow-band noise (the pointer) so that it matched the intracranial position of a second, experimenter-controlled stimulus (the target). Targets were sinusoidally amplitude-modulated tones centered on 500 Hz or 1 kHz, and modulated at 25, 50, or 100 Hz. Targets were presented with either the entire waveform delayed or with only the envelope delayed. The results suggest that delays of the envelope do affect the lateral position of low-frequency targets. However, the envelope-based cues appear to interact with those provided by the dominant fine structure.
Speech quality evaluation using ‘‘phoneme-specific’’ sentences
Authors: Huggins A. W. F. , Nickerson R. S.
Published: October 2005

A new approach is described for the design of speech materials used in subjective speech quality evaluation. Speech sounds are classified by their acoustic properties, and sentences are composed so as to concentrate all sounds with similar properties within one sentence. As a test of the method, subjective quality data were collected, using both a rank ordering and a rating task, from a set of 12 linear predictive vocoders, whose parameters were chosen so as to equate their bit rates at 2600 bps. The results show that the method can reliably reveal small differences in quality, and also yields information that can be of diagnostic help in determining the causes of quality degradation by a particular vocoder. A set of phoneme-specific sentences is appended.
Determination of the complex dynamic bulk modulus of elastomers by inverse scattering
Authors: Piquette Jean C.
Published: October 2005

The results of an investigation of a technique for determining the complex dynamic bulk modulus of elastomers via inversion of acoustic scattering data obtained in water are described. Least-squares fitting determines the set of expansion coefficients which is most consistent with measured scattered pressures. The zeroth expansion coefficient is further expressed in terms of a truncated Taylor series about an approximate value for the unknown bulk modulus. The required approximate value is calculated from an approximate relationship between the bulk modulus and a parameter related to the zeroth scattering coefficient. The Taylor series is used iteratively to obtain an improved value for the bulk modulus. The results of an experimental investigation to verify the technique are described. The complex bulk moduli of neoprene and butyl rubbers configured in 5.08-and 10.16-cm-diam spheres were measured at 5, 10, and 15 kHz using this technique. Agreement between the real part of the bulk moduli obtained in this investigation and those obtained via impedance-tube measurements is good. A significant conclusion of the present research is that the measured bulk moduli of the samples are quite sensitive to the molding technique used in their fabrication.
Impact noise and the equal energy hypothesis
Authors: Roberto M. , Hamernik R. P. , Salvi R. J. , Henderson D. , Milone R.
Published: October 2005

The equal energy hypothesis (EEH) was evaluated over a limited range of conditions by exposing four groups of chinchillas to impact noise (200-ms B duration) presented at a fixed rate of four impacts per second. The intensity of the impacts (107–125 dB peak SPL) and the duration (120–1.87 h) of the four exposure conditions were counterbalanced so that the four groups received the same total energy. The traumatic power of the exposures was assessed by measuring the threshold shift of the auditory evoked response and the amount of hair cell loss. Exposures between 107 and 119 dB were consistent with the EEH in that they produced roughly the same amount of permanent threshold shift (less than 20 dB) and hair cell loss (less than 20%). However, the 125-dB exposure produced substantially more threshold shift and hair cell loss than the three lower intensities. Thus, the EEH may be applicable only at lower impact intensities; above a ‘‘critical intensity’’ the amount of damage increases significantly.
Infant pitch perception: Evidence for responding to pitch categories and the missing fundamental
Authors: Clarkson Marsha G. , Clifton Rachel K.
Published: October 2005

While numerous studies on infant perception have demonstrated the infant’s ability to discriminate sounds having different frequencies, little research has evaluated more sophisticated pitch perception abilities such as perceptual constancy and perception of the missing fundamental. In the present study 7–8-month-old infants demonstrated the ability to discriminate harmonic complexes from two pitch categories that differed in pitch by approximately 20% (e.g., 160 vs 200 Hz). Using a visually reinforced conditioned head-turning paradigm, a number of spectrally different tonal complexes that contained varying harmonic components but signaled the same two pitch categories were presented. After learning the basic pitch discrimination, the same infants learned to categorize spectrally different tonal complexes according to the pitches signaled by their fundamental frequencies. That is, the infants showed evidence of perceptual constancy for the pitch of harmonic complexes. Finally, infants heard tonal complexes that signaled the same pitch categories but for which the fundamental frequency was removed. Infants were still able to categorize the harmonic complexes according to their pitch categories. These results suggest that by 7 months of age infants show fairly sophisticated pitch perception abilities similar to those demonstrated by adults.
A central spectrum model for the perception of coloration in filtered Gaussian noise
Authors: Kates James M.
Published: October 2005

In this paper we describe a monaural auditory signal-processing model for the perception of coloration. The model gives a central spectrum display of a stationary input signal. The central spectrum level for a nerve fiber tuned to a given frequency is computed as a combination of the average firing rate and the firing synchronized to the center frequency of the nerve. The model incorporates a critical-band filter bank, steady-state representations of the average and synchronized firing rates, and temporal integration. The central spectrum model, when used to process simulated data, accurately predicts the perception of coloration in filtered Gaussian noise.
Spectral analysis of sung vowels. II. The effect of fundamental frequency on vowel spectra
Authors: Bloothooft Gerrit , Plomp Reinier
Published: October 2005

One-third-oct bandfilter spectra of nine different vowels, each obtained as the average spectrum of vowels sung by professional male and female singers in nine modes of singing, were obtained at six fundamental frequencies (F0), ranging from 98–880 Hz. For F0=98 Hz both an empirical and a theoretical comparison were made between the representation of vowels in the formant space and the representation in the spectrum space. A first-order correspondence between both approaches was demonstrated. The vowel configurations in the spectrum space showed that, apart from differences in the grand-average spectrum, (1) for F0<220 Hz, vowel configurations were similar for males and females; (2) for F0=392 Hz, the variability in dimensions related to F1 and F2 was smaller than for lower F0 values, and variability related to F1 in male falsetto register was greater than in modal register (vowel spectra were similar in male falsetto register and female singing); (3) for F0=659 Hz, the vowel configuration had shrunk to clusters of front and back vowels; and (4) for F0=880 Hz, vowel differences were only marginal. The relation between the average sound level of the so-called singer’s formant and F0 appeared to be vowel dependent. Up to F0=392 Hz, the singer’s formant was on the average equally prominent for male and female singers, but for higher F0 its level, relative to overall sound-pressure level, dropped for females. Differences between average spectra of sung and spoken vowels are discussed.
A single-pole model for the propagation of ultrasound in soft tissue
Authors: Arthur R. Martin , Gurumurthy K. V.
Published: October 2005

A minimum-phase function, which characterizes the velocity dispersion in tissue was calculated from measured attenuation. This function was incorporated into a causal tissue model. Predictions of attenuation using the minimum-phase function with just a single pole matched measured attenuation in the 1- to 10-MHz range within a few percent. Dispersion of phase velocity predicted by the single-pole model was comparable to measured dispersion. The frequency associated with the single pole, which is a relaxation frequency, decreased with hemoglobin concentration and collagen content but increased with temperature. The electrical equivalent circuit for this model is a delay coupled with a low-pass filter which can be configured as a resistance in series with a parallel combination of resistance and capacitance.
In-air and underwater sounds of the Ross seal, O
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Authors: Watkins William A. , Ray G. Carleton
Published: October 2005

In-air and underwater sounds were recorded from Ross seals, Ommatophoca rossi, during January 1966 in the western Ross Sea, Antarctica, from Cape Hallet to Cape Adare. In-air sounds from seals hauled out on ice ranged from 100–1000 Hz and included short (0.05–0.1 s) tonal pulses with downward sweeping frequency, and longer (1–1.5 s) calls with downward and upward sweeping frequency, somewhat like a police siren. Underwater vocalizations included pulses and siren calls that were similar to the in-air sounds except that they had greater and mostly higher-frequency ranges (1–4 kHz). The underwater calls were pulse modulated at a consistent rate of about 650/s, and usually were formed of two independently varying tones, each with separate sideband harmonics. Overlapping underwater sound sequences were heard from seals scattered throughout the areas sampled. The distinctive springtime siren calls would be useful for locating groups of these elusive seals.
Comments on ‘‘A different look at the anechoic wedge’’ [J. Acoust. Soc. Am. 75, 855–858 (1984)]
Authors: Ballagh K. O. , Wassilieff C.
Published: October 2005

We present measurements to show that the reversed wedge design has limitations for anechoic room linings. Measurements of the low-frequency performance differ significantly from Warnaka’s and we question the value of reverberation room measurements of the absorption coefficient of anechoic room linings.
Measurements of acoustic impedance in a free field with two microphones and a spectrum analyzer
Authors: Allard Jean F. , Sieben Benita
Published: October 2005

A technique is presented for evaluating the normal acoustic impedance at the surface of a panel of absorbing material in a free field. The evaluation is achieved by measuring the pressure and the acoustic velocity with two microphones set very close to the panel. This technique allows measurements of impedance for panels of area about 1 m2, the two microphones being located very close to the panel so that, contrary to other methods, the effect of the finite dimension of the panel is negligible. Because of the very small spacing between both microphones, this technique allows precise measurements only for frequencies higher than 500 Hz.
Origins of magnetic recording concepts
Authors: Camras Marvin
Published: October 2005

Many brand new ideas in modern magnetic recording are quite ancient. Case histories in basic foundations of this art are good examples. Metal particle tape was proposed 95 years ago. High-frequency bias has its roots in the Marconi wireless detector of 1902. Digital recording goes back at least to Morse’s telegraph of 1838. The rotating-head principle used for video recorders dates back about two decades before it became practical. Sendust used in the latest recording heads was invented in 1936. Magnetic disks, the important memory of computers, were demonstrated in 1903. Soundstriping for motion picture film was advertised in 1917. Personal experiences in nearly a half-century of magnetic recording are related.
Fifty years of stereo phonograph pickups: A capsule history
Authors: Anderson C. Roger
Published: October 2005

From the 45° disk recording system shown in the 1933 benchmark stereo work of Blumlein to the present-day generations of pickups with ultrasonic capabilities is a long evolution of analytic and engineering effort. This paper is a recognition of advances along the way, such as the theory of tracing distortion, stylus contours, transducer principles, light and stiff moving systems, tracking requirements, and the design insight that led to contemporary pickups which perform superbly at 1-g stylus force.
Engineering highlights of the LP record
Authors: Gravereaux Daniel W.
Published: October 2005

For 35 years, the long playing microgroove 33-1/3 rpm disk record has brought to the consumer the highest fidelity programming of any mass media. This is due to the valued efforts of many engineers, scientists, and technicians in the development and implementation of microgroove mastering techniques, cutting and playing transducers, electroplating, stamping techniques, lacquer blanks, cutting styli, mastering lathes, presses, and vinyl formulation. This paper presents those developments which greatly augmented the information capacity of the record. It emphasizes a few of the highlights in the engineering of the most standardized sound medium in the world—the LP.
Resonances of plates and cylinders: Guided waves
Authors: Maze G. , Izbicki J. L. , Ripoche J.
Published: October 2005

The study of the normal diffusion of an ultrasonic plane wave by cylinders and plates imbedded in the water shows resonances which are the natural modes of vibration. When a natural mode of an elastic target is excited, the energy which is stored during the forced excitation is emitted after the end of the forced excitation. The observation of backscattered spectra obtained by the Resonance Isolation and Identification Method (RIIM) from an aluminum cylinder shows supplementary resonances. The directivity pattern of the transducer is the cause of these supplementary resonances. The behavior of these resonances is analogous to the resonances of the plate. This leads us to study the natural modes of the cylinder. All the resonances which are experimentally detected may be considered as normal modes of the target. The results obtained on plates and cylinders have a common point: the generation of a guided wave by the excitation of a resonance.
Sea surface scattering: Echo peak PDF
Authors: Stanton T. K.
Published: October 2005

We examine the statistical nature of the backscattered acoustic echo from the sea surface. In particular, the probability density function (PDF) of the maximum value of the echo achieved in a time gate is studied. We compare data from a 70-kHz sonar at near grazing angles to a recently developed statistical model that was employed in the context of (biological) volume backscattering [T. K. Stanton, J. Acoust. Soc. Am. 77, xxx–xxx (1985)]. The model fits the data quite well which implies that, like with volume scatterers in the ocean, the backscattered signal from the sea surface is effectively composed of many scatterers that each produce random phase, random amplitude echoes. The results can be applied to sidescan sonars where ‘‘clutter’’ from the sea surface may interfere with the detection of near surface biological organisms. From the theoretical model a probability of false alarm may be derived to aid in the detection.
Computation of velocity and density profiles of acoustic media with vertical inhomogeneities using the method of characteristics applied to the slant stacked data
Authors: Carrion Philip M.
Published: October 2005

An algorithm which is based on a discrete version of the method of characteristics is presented. The procedure consists of the transformation of the measured data into the slant stack domain (the domain of intercept time τ and horizontal slowness p) following application of the one-dimensional inverse method of characteristics to an arbitrary pair of traces in the (τ-p) domain. The result of the inversion is a pair of acoustic impedance functions which are used for separate computation of the velocity and density profiles in the acoustic medium. Advantages of the method are that (1) it can be directly applied to the data in the time domain, (2) it appears to be efficient in terms of computations, and (3) it does not require the acoustic impedance to be smoooth. A synthetic example illustrates the accuracy of the method.
Diffraction of Rayleigh waves in a half-space. I. Normal edge crack
Authors: Vu Bien Q. , Kinra Vikram K.
Published: October 2005

This paper is concerned with the diffraction of Rayleigh surface waves by an edge-crack normal to the free surface of a half-space. An experimental technique was developed to yield accurate and reproducible measurements of the scattered field on the free surface both in the vicinity of the crack and far away from it. The results show that the nearfield scattered field is very sensitive to the crack length and possesses many characteristic features which are shown to be potentially useful in the area of nondestructive testing and evaluation. The farfield transmission and reflection coefficients AT and AR were measured under both the steady time-harmonic motion and the transient motion of the half-space. In the short-wavelength limit (l/λR≥2), both AR and AT achieve the crack-length-independent values, namely AR=0.41 and AT=0.06; the former agrees with the reflection coefficient of a quarter-space and the latter agrees with the combined transmission coefficient through the leading corner, the tip, and the trailing corner of the crack. For l/λR≤2, AR and AT were found to agree very well with a recent theoretical solution of Achenbach and his co-workers [D. A. Mendelson et al., Wave Motion 2, 277–292 (1980); Y. C. Angel and J. D. Achenbach, J. Acoust. Soc. Am. 75, 313–319 (1984)].
Reverberation time in enclosures: The surface reflection law and the dependence of the absorption coefficient on the angle of incidence
Authors: Benedetto Giuliana , Spagnolo Renato
Published: October 2005

The sound decay and reverberation time of enclosures depend on the amount of randomization achieved during the decay. The randomization is determined by the degree of surface roughness and absorptivity and is also related to the shape of the enclosure. Many authors showed that, even in the hypothesis of a memoryless reflection law, the reverberation time largely varies when the absorptivity is nonuniformly distributed on the surfaces, for a fixed value of the sound absorption coefficient. In this paper, applying a ray-tracing simulation procedure to a simple two-dimensional enclosure, the effect is shown to be still stronger when a certain fraction of specular reflection is taken into account. In this case, it is also proved that one cannot neglect the effects connected to the dependence of the sound absorption coefficient on the incidence angle, which seems to introduce additional sound randomization.
Central auditory processing of peripheral vowel spectra
Authors: Chistovich Ludmilla A.
Published: October 2005

This paper presents a review of recent experiments in vowel perception done at the Pavlov Institute of Physiology in Leningrad. The data concern three topics: experimental procedures appropriate for the study of phonetic quality perception, processing of the auditory spectral shape of a vowel, and processing of the auditory dynamic spectrum of a vowel.
The k-space formulation of the scattering problem in the time domain: An improved single propagator formulation
Authors: Bojarski Norbert N.
Published: October 2005

The storage allocation requirement and solution speed of the k-space formulation of the scattering problem in the time domain developed by this author [N. Bojarski, J. Acoust. Soc. Am. 72, 570–584 (1982)] were improved by a factor of 2 and 4, respectively, by the replacement of the earlier two temporal propagators by a single more accurate propagator and the utilization of the special case real to complex FFT algorithm. It is shown that for problems of the size of about one million spatially discretized cells this method is about five times slower than an ideal solution, and requires about five times as much in core storage allocation as an ideal solution. It is shown that for a modern array processor this solution is I/O bound. It is pointed out that this method is ideally suited for parallel array processor implementation, resulting in even greater speed.
The scattering of ultrasonic waves in polycrystalline materials with texture
Authors: Hirsekorn Sigrun
Published: October 2005

The theory of ultrasonic propagation in polycrystals with independent and uniformly distributed orientations of the grains presented in previous papers [J. Acoust. Soc. Am. 72, 1021–1031 (1982); 73, 1160–1163 (1983)] is generalized to calculate the scattering coefficients and the phase and group velocities of plane compressional and shear waves in textured polycrystals. The calculation was done for plane waves in polycrystals of cubic symmetry with rolling texture in second-order perturbation theory using the assumption that the changes in the material constants from grain to grain are small. In the limit texture equal to zero the analytical results are exactly the same as those for untextured polycrystals previously presented. Numerical calculations are carried out for some examples.
Fourier series solution of Burger’s equation for nonlinear acoustics in relaxing media
Authors: Du Gonghuan
Published: October 2005

This paper modifies Burger’s equation, presented by previous authors, for nonlinear acoustics in relaxing media. Based on the forms of the Fourier series solution of the equation in the case of lossless media, the author solves successfully the extended Burger’s equation including various types of relaxation mechanisms. The solutions are obtained in the separate cases—before and after shock formation. It has been found that the results of previous authors can be derived from our solutions if certain approximations are made.
On the oscillation mode of gas-filled micropores
Authors: Miller Douglas L. , Neppiras E. A.
Published: October 2005

Small pores in hydrophobic membranes trap gas when the membrane is immersed in aqueous media, and the resulting ‘‘gas bodies’’ may be used for studying biophysical effects of ultrasonic cavitation. In a previous study [D. L. Miller and W. L. Nyborg, J. Acoust. Soc. Am. 73, 1537–1544 (1983)], two modes of oscillation, a ‘‘pistonlike’’ and a ‘‘membranelike’’ mode, were described theoretically, and either model appears capable of qualitatively explaining observations of the linear behavior of the gas-filled micropores. In this study, low-amplitude nonlinear theory is employed with observations of second harmonic emissions to show that the membranelike model is the more appropriate model for the 3.4- and 4.0-μm-diam micropores tested at 0.81 and 1.62 MHz. In addition, this model is expanded to include the case for which the gas is asymmetrically situated in a pore, to discuss the motion of the three-phase line at the periphery of an air–water interface in a pore, and to suggest an explanation of the phenomenon of gas loss from the pores when the incident field intensity is raised. Knowledge of the behavior of the gas-filled micropores in an ultrasonic field should allow a more complete understanding of biological effects on cells exposed to this form of cavitation activity.
Acoustic backscattering at low grazing angles from the ocean bottom. Part II. Statistical characteristics of bottom backscatter at a shallow water site
Authors: Chotiros N. P. , Boehme H. , Goldsberry T. G. , Pitt S. P. , Lamb R. A. , Garcia A. L. , Altenburg R. A.
Published: October 2005

Analyses of the statistical characteristics of bottom backscatter, measured in shallow water off San Diego, California, are presented. (The initial results of the experiment were presented by T. G. Goldsberry, S. P. Pitt, and R. A. Lamb at the 104th Meeting of the Acoustical Society of America, Orlando, FL, 8–12 November 1983.) The experimental sonar, mounted on the sea bottom, was operated at 30 kHz to gather data over a wide sector of the bottom. The bottom was patches of coarse and fine sand. The distribution function and probability of false alarm function of the detected envelope of widebeam and narrowbeam signals were measured. Some spatial and temporal correlation functions of the signal amplitudes were measured. A limited attempt was made to compare the results with existing theoretical models.
Steps in loudness summation
Authors: Mulligan B. E. , Goodman L. S. , Gleisner D. P. , Faupel M. L.
Published: October 2005

The dependence of binaural loudness summation on interaural phase of tones ranging between 250 and 1400 Hz was investigated in a series of experiments using a loudness-matching procedure. Observers matched loudnesses of monaural–binaural and binaural–binaural pairs of alternating tones by adjusting the amplitude of one of the two. Adjustable and reference components of each tone pair were equal in frequency and were varied independently in interaural phase angle through the range ±177°. For each tone frequency, steps in loudness summation of approximately 3 dB were obtained in the vicinity of a constant value of phase angle, θt , which depends on the Hornbostel–Wertheimer constant (τH) according to the relations θt=2πfτH for tones of low frequency (f≤1/2τH), and θt=2π(1−fτH) for tones of higher frequency (1/2τH≤f≤1/τH). Spatial relationships among alternating tones observed in the above conditions covaried with relative loudness in a complex manner, but exhibited qualitative changes in the vicinity of θt .
Development of absolute thresholds in chickens
Authors: Gray Lincoln , Rubel Edwin W.
Published: October 2005

Absolute auditory thresholds were estimated in chickens at 0 and 4 days after hatching. Momentary suppressions of the chicks’ regular peeping, following the onset of a tone, were used as indications of stimulus detection. In the first experiment a staircase procedure was used to estimate thresholds. The absolute thresholds of both ages were the same at low frequencies (250–500 Hz), but at higher frequencies (1–2 kHz) 4-day-old chicks had lower thresholds than the 0-day-old chicks. The estimates of thresholds at 1 kHz were corroborated in the second experiment with a method of constant stimuli. A more efficient modified method of limits was used to replicate the age by frequency interaction in the third experiment. These changing thresholds are likely to reflect a developmental process somewhere in the auditory system and not some nonsensory artifact for two reasons: (a) similar thresholds at low frequencies show that developmental differences are not due to differences in the sensitivity of the testing procedure at the two ages and (b) thresholds obtained from the 4-day-old birds are similar to estimates from mature birds. In conclusion, responsiveness to low frequencies develops before responsiveness to higher frequencies, showing that the development of absolute thresholds is correlated with other measures of functional maturation in the auditory system.
The effect of frequency change on discrimination of pulse bursts in an electrocutaneous tactual vocoder
Authors: Bull Dale , Eilers Rebecca E. , Oller D. Kimbrough , Mandalia Baiju D.
Published: October 2005

Tactual vocoders (artificial hearing systems) transduce the acoustic energy of speech into patterns of stimulation that are presented to the skin. In an electrocutaneous tactual vocoder, energy within an acoustic-frequency band is generally represented at a particular skin locus by the rate or frequency of brief electrical pulse bursts. At present little is known about tactual sensitivity for changes in the frequency of brief, bipolar electrical pulses used in several current electrocutaneous vocoder designs. Accordingly, discrimination of frequency change of electrocutaneous bipolar signals was evaluated for standard frequencies of 48, 100, 148, 200, and 248 Hz at signal durations of 50, 100, and 250 ms. Bipolar pulses (height=10 mA, width=13 μs) were presented on a single electrode placed slightly above and 8 cm to either the left or right of the navel. In a same–different task, three practiced subjects judged pairs of stimuli separated by an interstimulus interval (ISI) of 300 ms. For standard frequencies of 48 and 100 Hz, psychometric functions were similar for all subjects and all signal durations. For these frequencies, Δ f/f was constant at approximately 0.3. By contrast, for standard stimuli greater than 100 Hz, the Weber fraction was found to increase dramatically as a function of both standard frequency and signal duration. In a second, similar experiment the Weber fraction for a 248-Hz standard increased as ISI was decreased below 300 ms. By contrast, ISI had little effect on sensitivity for standard stimuli of 48 and 100 Hz. Overall, these results suggest guidelines for possible intensity coding schemes for future electrocutaneous vocoder designs.
The pursuit of invariance in speech signals
Authors: Lisker Leigh
Published: October 2005

The search for the acoustic properties useful to the listener in extracting the linguistic message from a speech signal is often construed as the task of matching invariant physical properties to invariant phonological percepts; the discovery of the former will explain the latter. These phonological percepts are essentially the phonemes of pregenerative phonology, and they are more or less faithfully reflected in standard alphabetic writing. Thus English deep and doom are supposed to be perceptually identical in their initial /d/s; the orthographic similarity is in agreement with the linguist‘s ‘‘representation’’ of these forms. The partial identity in spelling is only weak evidence for perceptual invariance, however. First, while some phonemes may comprise a single ‘‘sound,’’ others are said by linguists to include phonetically distinct ones. Thus English /p/ includes both aspirated and unaspirated voiceless labial stops. The view that it is not the phoneme, but rather the phonetic feature, to which an acoustic invariant might be attributed, raises two questions: (a) Since segments sharing a feature are rarely judged to constitute a single sound, the search for a feature-specific invariant, whose function is to explain perceptual constancy, is deprived of its essential motivation, and (2) there is no more reason to expect the acoustic cues to a feature to be context-independent than is the case with the phoneme. What seems more likely is to find that some phonemes, and some features, are more invariantly marked in the speech signal than others.
On some issues in the pursuit of acoustic invariance in speech: A reply to Lisker
Authors: Blumstein Sheila E. , Stevens Kenneth N.
Published: October 2005

This paper presents an alternative view of acoustic invariance in speech to that discussed by Lisker [J. Acoust. Soc. Am. 77, xxx–xxx(1985)]. Three points are considered—the minimal unit for acoustic invariance, the level of linguistic representation over which this unit operates, and the role that acoustic invariance plays in speech and language. Our position emphasizes the role of phonetic features in a theory of acoustic invariance, and we propose a series of working hypotheses to guide research in this area.
Comment on ‘‘Propagation of axisymmetric free waves in a circular cylindrical shell’’ [J. Acoust. Soc. Am. Suppl. 1 7
5, S77 (1984)]
Authors: Rumerman M. L.
Published: October 2005

In a paper presented at the meeting of the Acoustical Society of America in May 1984, D. H. Trivett presented results for axisymmetric wave propagation in circular cylindrical shells having traction-free lateral surfaces which indicated a mode of the infinite shell not found by others. A key feature of this mode is that its phase speed varies approximately linearly with frequency at low frequencies, leading to a limiting finite wavelength at low frequencies. It is argued in this letter that such a behavior implies consequences which contradict resonance frequency–size relationships for linear systems.
Estimate of a thermal time constant in highly porous layered fine fibers
Authors: Lambert Robert F.
Published: October 2005

A method for estimating the value of the universe thermal time constant associated with sound pressure fluctuations within a highly porous fibrous material is outlined. This value can be used in turn to determine the transition frequency between an isothermal process at low frequencies and an adiabatic process at high frequencies. Employing a Rayleigh tube model, the characteristic thermal length LT is proportional to the mean pore size ap and inversely proportional to the Kozeny number K.
A Exact transition from two- to one-dimensional internal-wave power spectra
Authors: Brill Michael H. , Dozier Lewis B.
Published: October 2005

An exact expression is derived for the one-dimensional power spectra in the Karhunen–Loève expansion for the sound-speed fluctuations due to internal waves used by Dozier and Tappert [J. Acoust. Soc. Am. 63, 353–365 (1978); 64, 533–547 (1978)]. The exact power spectra are always less than the approximate spectra, the difference being greatest at low internal wavenumbers. Hence the effects of the model internal waves on the mode statistics were overestimated in the earlier papers; however, the qualitative conclusions of these papers remain unchanged.
Effect of reverberation on the identification of stationary vowels
Authors: Plomp R. , Langhout G.
Published: October 2005

In a diffuse sound field, the amplitudes of the individual harmonics of a stationary vowel have an uncertainty with a standard deviation of 5.57 dB. It is shown that this phenomenon slightly reduces the identification score for a set of eight synthetic vowels derived from male utterances. In terms of variance in the one-third octave band-filter levels, the spectral differences introduced by reverberation are of about the same magnitude as the differences among the spectra of the same vowels pronounced by different male speakers.
Ipsilateral versus bilateral placement of a tactile vocoder display
Authors: Craig James C. , Green Barry G. , Rhodes Roger P.
Published: October 2005

A tactile vocoder was evaluated in a word recognition task. The vocoder consisted of a pair of two-dimensional vibrotactile arrays on which subjects placed their fingers. For one group of subjects, the two arrays contacted two fingers on the same hand (ipsilateral condition); for the second group, the arrays contacted two fingers on opposite hands (bilateral condition). Performance was better in the bilateral condition; however, the rate at which words were acquired, even in the bilateral condition, was less than that reported by Brooks and Frost [J. Acoust. Soc. Am. 74, 34–39 (1983)] with a tactile vocoder placed on the arm.
Aircraft noise annoyance at three joint air carrier and general aviation airports
Authors: Fidell Sanford , Horonjeff Richard , Mills John , Baldwin Edward , Teffeteller Sherri , Pearsons Karl
Published: October 2005

The results of social surveys conducted near three airports that support both general aviation and scheduled air carrier operations are presented and discussed. Inferences supported by these data include: (1) The nature of noise exposure and community reaction at smaller airports may differ from that at larger airports; (2) survey techniques are capable of identifying changes in annoyance associated with numerically small changes in noise exposure; (3) changes in the prevalence of annoyance are causally produced by changes in noise exposure; and (4) changes in annoyance associated with changes in exposure vary with time.