bluuebunny/crossref_metadata_2025 huggingface dataset:
Roughness scaling of complex tones.
Authors: Feng B. John , Wakefield Gregory H.
Published: October 2005

The term roughness has been proposed to describe a sensation elicited by sinusoidal amplitude modulation (SAM) of pure tones and modulated wideband noise [E. Terhardt, Acustica 30, 201–213 (1974)]. Roughness of SAM tones is known to exhibit a close relationship to modulation depth. It is hypothesized that roughness of complex tones, as scaled against modulation depth of a SAM tone, can be predicted from the magnitude of the envelope spectrum. Subjects were asked to scale complex tones on the dimension of roughness by matching a test stimulus to a reference SAM tone of subjectively equivalent roughness. The test stimuli were drawn from complex tones consisting of a variable number of equal amplitude, harmonically related components. The reference set was 12 SAM tones with modulation depths spanning the range from detection threshold to 100 [Viemeister, J. Acoust. Soc. Am. 88, 1367–1373 (1990)]. The modulation frequency of the reference set varied across tests conditions according to the minimum component spacing of the tests stimulus. Results of the scaling experiments suggest roughness can be predicted as a function of the narrow-band peaks in the magnitude spectrum of the envelope. [Work supported by Ford Motor Company.]
Methods of isolation of modal resonances (a review).
Authors: Veksler Naum , Conoir Jean-Mark , Izbicki Jean-Louis , Rembert Pascal
Published: October 2005

The analytical methods of isolation and description of the resonance components of partial modes in scattering problems of acoustic, elastic, and electromagnetic waves are set forth. The results of these methods’ applications are presented and their effectiveness is discussed. For some particular cases the exactness of the results obtained can be estimated as well. The following methods are considered: gradient of the phase, utilization of impedance type intermediate backgrounds, Argand diagram method, and pole evaluation on the frequency complex plane for a fixed mode order. The methods can be even used for rather complicated situations: for very narrow and rather broad resonances, near the point of intersection of the dispersion curves of phase velocities, and for very close situated resonances. The illustrative examples are given for the problems of scattering of bodies of spherical and cylindrical shape. The resonances are isolated for waves of different physical nature: diffracted (Franz type), normal (Lamb type), shear, Rayleigh type, and whispering gallery. With the properly computed modal resonances one can immediately obtain the dispersion curves of the phase and group velocities of every wave, and construct the acoustic spectrogram of the scatterer. Jointly with the well-known experimental methods, the described ones form the basis for ultrasonic spectroscopy.
Effects of bilingualism on non-native phonetic contrasts.
Authors: Calderón Janet , Best Catherine T.
Published: October 2005

Monolingual listeners often have difficulties discriminating non-native contrasts. The Perceptual Assimilation Model (PAM) [C. T. Best, G. W. McRoberts, and N. M. Sithole, JEP:HPP 14, 345–360 (1988)] predicts poor discrimination if two non-native sounds assimilated equally well to a single native category (SC), good discrimination if a category goodness (CG) difference is perceived, and excellent discrimination if sounds are assimilated to two different categories (TC). However, implications for bilingual listeners are uncertain. Do bilinguals maintain two separate phonological systems, or do the systems interact to enhance or inhibit non-native discrimination? In this study, monolingual English and bilingual Spanish/English listeners discriminated and categorized Spanish [b–p], English [b–ph], and three Xhosa bilabial stop contrasts. Both groups discriminated English [b–ph] excellently, as did bilinguals for Spanish [b–p], which monolinguals discriminated less well, consistent with CG assimilation. Compatible with PAM, monolinguals showed excellent TC performance on Xhosa unaspirated/aspirated stops; bilinguals’ lower discrimination indicated CG assimilation. On Xhosa implosive/pre-nasalized stops, monolinguals showed CG assimilation and greatly outperformed bilinguals, who showed an SC pattern. Conversely, on Xhosa implosive/plosive stops monolinguals showed SC assimilation; bilingual discrimination was higher, showing GC assimilation. [Work supported by NIH.]
Perceptual assimilation of German vowels by American listeners: Context and speaker effects.
Authors: Strange Winifred , Bohn Ocke-Schwen , Trent Sonja A. , McNair Melissa C. , Bielec Katherine C.
Published: October 2005

This study investigated American English (AE) speakers’ perceptual assimilation of North German (NG) vowels spoken in 5 CVC contexts by four adult male speakers. Fourteen NG vowels were produced in /bVp, bVt, dVt, gVt, gVk/ syllables in the sentence ‘‘Ich habe CVC gesacht.’’ Twelve monolingual AE listeners were tested on each speaker’s corpus; consonantal context was a within-subjects variable. Response categories were indicated by /hVd/ key words and IPA symbols. Listeners responded by selecting the AE category containing the vowel most similar to the one in the utterance and rating its ‘‘goodness of fit.’’ The percentages of selection of the modal AE response category for each NG vowel ranged from 99% for /i/→/i/ (best fit) to 41% for /o//→/u/ (worst fit). NG front and back rounded vowels were assimilated to AE back rounded vowels. However, for seven vowels, modal category percentages differed by greater than 15% across the five consonantal contexts. There was also significant variation in assimilation patterns across the four speaker groups for 11 of the NG vowels. These results have implications for theories of L2 speech learning. [Work supported by NIDCD.]
Preferred onsets.
Authors: Maddieson Ian
Published: October 2005

Previous analysis of segment inventories (e.g., by Maddieson, 1984 and Lindblom and Maddieson, 1988) has shown that, across a large sample of languages, the segments that more commonly occur contrastively are those that are less complex on an intuitive scale of simplicity. But a segment type within any given language may occur in many or few words: segments that occur in more items may also be those that are in some sense more simple, or those that combine best with other segments in sequences. Within-language frequency of usage may therefore serve to show that segments of (near-) equal frequency in terms of mere membership in inventories in fact show different preference patterns. However, because there are many idiosyncratic properties of individual languages, it is important to look across a range of languages to reach general conclusions. The present paper reports on the relative frequency of the different onset consonants found in the universally present syllable type CV in a global sample of 31 languages (10 from Asia, 8 from the Americas, 6 from Africa, 3 from Europe, and 4 from the Pacific area). The counts are based on lexical frequency. [Work supported in part by NIH.]
Modeling the categorization of a large F1–F2–F3 continuum by Finnish listeners.
Authors: Nearey Terrance M. , Kiefte Michael
Published: October 2005

A continuum of 972 vowels was synthesized, each of which was 115 ms in duration with a falling F0 contour (125–100 Hz). F1 ranged (in 0.5- Bark steps) from 250 to 760 Hz, F2 from 750 to 2260 Hz and F3 from 1360 to 3080 Hz. F4 and F5 were fixed at 3500 and 4500 Hz, respectively. (Constraints were placed on formant separations to ensure relatively natural stimuli.) This continuum was previously categorized by a group of English speakers [T. M. Nearey and M. Kiefte, J. Acoust. Soc. Am. 96, 3284(A) (1994)]. The same stimuli were presented to 14 speakers of Finnish at the University of Turku. Subjects categorized these stimuli with labels for the nine Finnish vowels, / i, e, y, ö, æ, u, o/. Results of logistic regression analysis will be presented and compared with previous findings for English. [Work supported by SSHRC. The assistance of Ulla Fisher and Dr. Olli Aaltonen of the University of Turku in collecting the Finnish data is gratefully acknowledged.]
Arabs’ stress placement in English: Intelligibility test.
Authors: Mitleb Fares
Published: October 2005

This study was intended to give an impressionistic description of Arabs’ performance in English stress placement. Two native British English speakers were asked to evaluate the productions of English words by six Arabs. Findings indicated that the Arab subjects’ ‘‘conscious knowledge’’ of a stressful speaking situation was less than satisfactory. Listeners reported a great percentage of confusion in stress placement. A number of explanations were attempted for the intelligibility problem which arises from the misplacement of stress in the subjects’ productions. It was also inferred from the confusion Arabs made that suprasegmentals should be given emphasis in the teaching of foreign languages and should be taught simultaneously with segmental structure of the target tongue. [Research supported by Yarmouk Univ.]
Harvey Fletcher’s role in the creation of communication acoustics
Authors: Allen Jont B.
Published: October 2005

The major contributions made by Harvey Fletcher and his colleagues to communication acoustics are summarized along with a brief account of the acoustical career of the first President of the Acoustical Society of America.
Wave propagation in fluid-loaded, transversely isotropic cylinders. Part I. Analytical formulation
Authors: Berliner Marilyn J. , Solecki Roman
Published: October 2005

The problem of wave propagation in an infinite, fluid-loaded, homogeneous, transversely isotropic cylinder is studied within the framework of the linearized, three-dimensional theory of elasticity. The equations of motion of the cylinder are formulated using the constitutive equations of a transversely isotropic material with a preferred material direction collinear with the longitudinal axis of the cylinder. The equations of motion of the internal and external fluids are formulated using the constitutive equations of an inviscid fluid. Displacement potentials are used to solve the equations of motion of the cylinder and the fluids. The frequency equation of the coupled system, consisting of the cylinder and the internal and external fluids, is developed under the assumption of perfect-slip boundary conditions at the fluid–solid interfaces. This frequency equation is general in axial wave number k, circumferential wave number n, cylinder wall thickness h, and radial frequency ω. Simplifications to the frequency equation for the cases of zero wave number and material isotropy are discussed.
Wave propagation in fluid-loaded, transversely isotropic cylinders. Part II. Numerical results
Authors: Berliner Marilyn J. , Solecki Roman
Published: October 2005

The frequency equation of a coupled system consisting of an infinitely long, fluid-loaded, homogeneous, transversely isotropic cylinder was derived in Part I [J. Acoust. Soc. Am. 99, 1841–1847 (1996)]. In this paper, Part II, the frequency spectra for the n=1 nonaxisymmetric modes of wave propagation are presented for hollow cylinders, fluid-filled cylinders, and cylinders that are fluid filled and immersed in fluid. These frequency spectra consist of the first three branches corresponding to the flexural mode, the longitudinal mode, and the circumferential mode. Since propagation modes are of primary interest, branches extending into the imaginary and complex wave-number domain are not included in this study. Numerical results for an isotropic (linearly elastic) rubber cylinder are compared to the results for a highly anisotropic, fiber-reinforced cylinder. The material properties of the rubber cylinder are identical to the properties of the matrix material of the fiber-reinforced cylinder. It is shown that the characteristics of wave propagation in the fiber-reinforced cylinder, with and without fluid loading, are markedly different from the characteristics of wave propagation in the isotropic cylinder.
Reactive acoustic intensity for general fields and energy polarization
Authors: Stanzial Domenico , Prodi Nicola , Schiffrer Giuliano
Published: October 2005

A kind of energy polarization is shown to occur in certain acoustic fields, because of energy oscillations due to the instantaneous reactive intensity. The time-averaged behavior of such oscillations is described by a second degree symmetric tensor, which is identified with the time-independent reactive intensity, whose conventional vectorial definition is obtained for particular fields, including monochromatic and spherical ones.
Effect of multilayer baffles and domes on hydrophone response
Authors: Ebenezer D. D. , Abraham Pushpa
Published: October 2005

The effect of infinite multilayer planar baffles and domes on the response of point hydrophones mounted on the baffles with their centers at some distance from the face of the baffles is studied. The analysis is based on the use of transfer matrices and matched boundary conditions. A two-port transfer matrix for a baffle–dome system with several solid and liquid layers is first developed by using four- and two-port transfer matrices for solid and liquid layers, respectively. This is then used to determine the voltage generated by a hydrophone in response to an incident plane wave as well as a specified velocity distribution on the rear of the baffle. The voltage depends on the acoustic and acceleration sensitivities of the hydrophone and on the characteristics of the baffle–dome system. It is also shown that in most cases moderately low values of acceleration sensitivity are sufficient to ensure that the waterborne noise sensed by hydrophones is much greater than the structureborne noise. Elastic theory is used to model the solid layers. Numerical results are presented to illustrate the effect of single, double, and triple layer baffles, compliant layers, speed of shear waves, and the distance between the hydrophone and the baffle on the generated voltage. Experimental results are also presented.
Leaky plate modes: Radiation into a solid medium
Authors: Molz Eric B. , Beamish John R.
Published: October 2005

The propagation of ultrasonic waves has been studied for a thin plate (an alumina membrane 60 μm thick) surrounded by a second medium (helium) with much lower density and slower sound speeds. When the helium freezes, there are sudden jumps in the attenuation of both the shear SH(0) and the longitudinal L(1) plate modes which appear to result from radiation of sound into the solid helium. Since there is a large acoustic mismatch between the plate and the helium, the attenuation of these ‘‘leaky’’ modes is relatively small. The expected attenuation has been calculated for the SH(0) and L(1) modes in the low-frequency limit where the sound wavelength is much greater than plate thickness. When the helium is fluid, neither mode can radiate and the attenuation is small. Once the helium is frozen, however, both modes become leaky. For the SH(0) mode, only shear waves are generated in the helium but the L(1) mode can radiate both transverse and longitudinal waves. The magnitude of the observed attenuation changes, as well as their dependence on frequency and pressure, agree quite well with those calculated for leaky modes using the known properties of the alumina plate and of solid helium.
Rayleigh scattering from nonspherical particles
Authors: Palmer D. R.
Published: October 2005

A comprehensive framework is developed for calculating the intensity received by a monostatic sonar system due to backscattering from a cloud of nonspherical particles suspended in the ocean. The cloud can consist of different types of particles having arbitrary shapes, volume distributions, and orientations, as well as an overall mass density that varies spatially within the cloud. In the Rayleigh region it is possible to average over particle orientation exactly. The averaged backscattered intensity depends on particle shape through the eigenvalues of a tensor that can, in principle, be determined by solving a boundary value problem for a harmonic function. Since the solution to this boundary value problem is out of reach practically, bounds are obtained on the eigenvalues using the theory of isoperimetric inequalities. Bounds can thereby be obtained on the backscattered intensity that are independent of particle shape. These bounds form the basis for obtaining estimates of the error that is made by assuming the particles in the cloud scatter sound as if they were spherical. A number of examples and applications are considered, the most important of which is the feasibility of a sonar to image black smoker hydrothermal plumes. The reassuring result that the spherical particle assumption is likely to lead to feasibility criteria that underestimate the performance of a sonar is obtained.

The isoperimetric bounds are combined with the principle of maximum entropy, applied to the distribution of particle shapes, to obtain a new expression for the square of the amplitude for backscattering at wave number k0 from a particle of volume V, specific bulk modulus e and specific density h: Φ2=(k20V/4π)2[(e−1)/e+(h2−1)/2h]2. This amplitude is obtained by averaging over particle orientation and particle shape and is to be compared to the corresponding quantity for a sphere Φ2sp=(k20V/4π)2[(e−1)/e +(3(h−1))/(2h+1)]2. The use of the new expression is preferred in situations where it is known the particle shapes are quite variable and irregular and where 1.0≤h≤2.5. In all the examples considered it is found the error that results from assuming the particles scatter sound as if they were spherical is small. This is comforting and consistent with one’s intuition that in the Rayleigh region the scattered sound should be somewhat insensitive to the shape of the scatterer.
Experimental demonstration of the frequency dependence of the effective scatterer number density
Authors: Chen Jian-Feng , Zagzebski James A. , Madsen Ernest L.
Published: October 2005

In previous papers, a data reduction method for determining a frequency-dependent ‘‘effective scatterer number density’’ in ultrasound was reported [Chen et al., J. Acoust. Soc. Am. 95, 77–95 (1994); 96, 2556–2563 (1994)]. The effective scatterer number density is the actual number density of scatterers multiplied by a frequency-dependent factor that depends on the differential scattering cross sections of the scatterers. Evaluation of this technique based on measurements applied to a phantom with a distribution of scatterer diameters is reported here. This condition yields an effective scatterer number density that depends on the dominant scatterer concentration at the analysis frequency. Measured scatterer number densities at 3.5, 5, and 8 MHz were in agreement with theoretical computations of this parameter for the phantom.
Determination of the viscous characteristic length in air-filled porous materials by ultrasonic attenuation measurements
Authors: Leclaire P. , Kelders L. , Lauriks W. , Glorieux C. , Thoen J.
Published: October 2005

The concept of viscous characteristic length is used to describe the acoustical behavior of fluid-saturated porous media in the high-frequency regime. A method to determine this parameter consists of measuring the wave attenuation in the high-frequency limit. This method has already been used for porous materials saturated by superfluid 2He. It is tested in the case of air-filled absorbent materials in a frequency range of [50–600 kHz]. The thermal characteristic length is assumed to be known or measured independently. Two examples are presented. In the first one the method is usable and the viscous characteristic length Λ is deduced from the high-frequency behavior of the attenuation per cycle. In the second example, an additional attenuation occurs at high frequencies and only an estimate of Λ can be given. Nevertheless, the estimation appears to be rather accurate. The values obtained by this method are compared to those determined by a nonlinear fit of the dispersion curves.
Modal analysis of a structure in a compressible fluid using a finite element/boundary element approach
Authors: McCollum M. D. , Siders Clementina M.
Published: October 2005

One approach to modeling the resonant behavior of structures in a compressible fluid is to use finite elements to describe the structure and boundary elements to describe the fluid. The fluid loading is characterized by a complex, frequency-dependent influence matrix that is combined with the frequency-independent stiffness and mass matrices obtained from the finite element model. This approach works well for determining the fluid-loaded harmonic response of the structure over a specified frequency range, if one knows the appropriate frequency range over which to perform the analysis. Since the in-fluid resonance frequency is usually not known, the designer must choose successive frequency sets until the resonance peak is found. This paper describes a method that eliminates this guesswork by computing the in-fluid eigenfrequency of the mode of interest using boundary elements to model the fluid loading. The procedure is iterative, beginning with the in vacuo eigenfrequency and continuing until the in-fluid eigenvalue converges. The designer may then perform a harmonic analysis in a narrow band about the computed eigenfrequency to obtain the structural and/or acoustic response levels. The accuracy and efficiency of the technique is demonstrated with two examples: a spherical shell and a low-frequency projector, both in water.
Acoustic gyrotropic tensor in quasicrystals
Authors: Rao K. Rama Mohana , Rao P. Hemagiri
Published: October 2005

With the employment of group-theoretical methods, the surviving and independent numbers of acoustic gyrotropic tensor coefficients are determined for all the nine point groups with fivefold notations describing the symmetry of quasicrystals.
Saturation of nonlinear spherical and cylindrical sound waves
Authors: Enflo B. O.
Published: October 2005

Nonlinear acoustic waves with spherical and cylindrical symmetry, described by a generalized Burgers’ equation, are studied. A sine oscillation at the source is distorted into a sawtooth wave profile because of nonlinearity. Very far from the source (old-age region) the wave is again a sine wave solution of a wave equation in which the nonlinear term has grown so small that it can be neglected. In this paper the amplitude of the old-age wave, which is independent of the amplitude at the source (saturation), is determined for nonlinear sinusoidal spherical and cylindrical waves by analytical methods for a certain range of parameter values. The old-age amplitude in this range of parameter values was determined earlier by an approximate method, which overestimates the amplitude by a factor 1.36 in the plane-wave case. It is shown in this paper that this overestimation is still greater for spherical and cylindrical waves.
Particle separation using acoustic radiation force and elecrostatic force
Authors: Yasuda Kenji , Umemura Shin-ichiro , Takeda Kazuo
Published: October 2005

A method for separating particles in liquid by exploiting the competition between acoustic radiation force and electrostatic force is investigated. The displacement of particles from the pressure node of an ultrasound standing wave varies according to the effective charges, radii, and stiffness of the particles, and the particles of different radii can thus be separated even when they consist of the same material. When the particles are of different materials, they can also be separated in relations to their effective electric charges or their stiffness. In this study, the efficacy of this method was theoretically estimated and demonstrated by an experiment, with a mixture of polystyrene spheres of different radii in water, using 500-kHz ultrasound and a 3.3-V/mm electric field. The measured ratio of the displacements of polystyrene spheres 10 and 20 μm in diameter from the pressure node was 2:3, which is consistent with the value predicted theoretically. Radiation forces on the polystyrene spheres were also measured by using this technique.
Acoustic solitary waves in a tunnel with an array of Helmholtz resonators
Authors: Sugimoto N.
Published: October 2005

It is demonstrated theoretically that an acoustic solitary wave can be propagated in a tunnel with a periodic array of Helmholtz resonators, if the dissipative effects are made negligibly small. As wave propagation in such a periodic system is known as the Bloch waves, the array can give rise to the dispersion necessary to formation of the solitary wave. Explicit profiles of the solitary waves are obtained by solving the steady-wave solutions to the nonlinear wave equations derived previously. It is found that the solitary wave is compressive and its propagation speed is slower than the usual sound speed a0, i.e., subsonic, but faster than a0(1−κ/2) in the linear long-wave limit, κ being a small parameter representing the ratio of the cavity’s volume to the tunnel’s volume per axial spacing between the neighboring resonators. As the propagation speed approaches the upper bound, the height of the solitary wave increases to approach the limiting height, while as the speed approaches the lower bound, the solitary wave tends to be the soliton solution of the Korteweg–de Vries equation. It is also found that while no solutions exist for the speed below the lower bound, the shock wave may be propagated for the speed above the upper bound, i.e., supersonic, but accompanying nonlinearly oscillatory wavetrain downstream.
The effect of sea-surface roughness on shallow water waveguide propagation: A coherent approach
Authors: Norton Guy V. , Novarini Jorge C.
Published: October 2005

Standard propagation models in underwater acoustics (e.g., normal modes, PE) are deterministic in nature, i.e., they deal with a single realization of the environment. Additionally, for mathematical reasons, they typically treat the sea surface as a flat pressure-release surface. Effects of sea surface and bottom roughness are incorporated through a loss mechanism. This is accomplished by including an additional attenuation factor based on coherent loss of the surface-interacting component of the propagating field. This type of correction presents a mathematically inconsistent model, since usually results from stochastic scattering models are applied to results from single realizations of the stochastic medium. Moreover, scattering kernels are generally derived assuming a homogeneous medium underlying the sea surface, an assumption incompatible with a realistic environment. Using a numerical model [Norton et al., J. Acoust. Soc. Am. 97, 2173–2180 (1995)] that combines a high fidelity Parabolic Equation propagation model with the conformal mapping technique developed by Dozier [L. B. Dozier, J. Acoust. Soc. Am. 75, 1415–1432 (1984)] to handle surface roughness in a marching algorithm, forward propagation with a single realization of a rough sea surface overlying a complex ocean environment can be modeled in a mathematically consistent way.

This technique is applied to the problem of shallow water propagation with a rough sea surface. For the adopted environment and range of rms roughnesses considered (0.28<kh<2.33, where k is the acoustic wave number and h is the rms surface height) the inclusion of the rough surface introduces a significant increase in the transmission loss and vertical-angle distribution of the propagating field. Results for this environment also show that, on average, the transmission loss is close to that calculated using the roughness-induced attenuation factor approximation. The transmission loss calculated with the roughness-induced attenuation factor exhibits a smoother range dependence, indicating strong attenuation of energy at steeper propagating angles. However, when strong upward refraction conditions exist, coherent effects and energy redistribution cannot be ignored and results from the procedure which incorporates the roughness through a loss mechanism are in error.
Imaging the sources on a cylindrical shell from far-field pressure measured on a semicircle
Authors: Williams Earl G.
Published: October 2005

This paper provides a method to identify which areas on a vibrating cylindrical shell body radiate to the far field. Of particular interest is the identification of these surface ‘‘hot spots’’ (as a function of frequency) from pressure measurements made in the far field on a circle with the source at the center, located in the same plane as the axis of the shell. In this paper a simple formula is derived using a rigorous mathematical approach for the backpropagation of this far-field data to the surface of the shell. The accuracy of this approach is tested with numerical and experimental data. It is shown over a wide frequency range that far-field data can accurately predict the acoustic source regions on the shell in the same plane as the measured data. These regions are quantified using a new concept, supersonic acoustic intensity. Implied in the success of this approach is a general rule that acoustic sources on a cylindrical body which radiate to the far field, radiate dominantly in the direction defined by the plane passing through the shell axis and the source.
Acoustic pulse propagation in a fluctuating ocean with range-dependent sound-speed profile
Authors: Chang W. R. , Tarng J. H.
Published: October 2005

When an acoustic pulse propagates in a randomly fluctuating ocean with a deterministic sound-speed profile, it is distorted since every frequency component experiences different extents of scattering from the random inhomogeneity and echo numbers. Here, the split-step method is used to simulate an acoustic pulse with a 3-kHz carrier propagating through a turbulent ocean with range-independent/-dependent sound-speed profiles. It is found that (1) the ocean is a frequency-selective fading channel; (2) the received pulse profile is dependent on the received depth, sound-speed distribution, fluctuation strength, and scale length of turbulence in oceans; (3) the rms pulsewidth is broadened by several times its initial value as a consequence of pulse echoes and pulse wandering of every pulse realization of the ensemble; (4) the rms pulsewidth is increased when the fluctuation strength increases or the scale length decreases; and (5) the statistical properties of the propagating pulse are similar for both the range-independent and -dependent cases in the mean square sense.
An evaluation of 1–3 connectivity composite transducers for air-coupled ultrasonic applications
Authors: Hayward Gordon , Gachagan Anthony
Published: October 2005

A combination of theoretical modeling and experimental analysis is used to predict and assess the performance of 1–3 composite transducers for operation in an air-coupled environment. Specifically, finite element analysis, supported by linear systems modeling, is employed to evaluate transmission and reception characteristics over the complete volume fraction range, for operating frequencies in the region of 500 kHz, and the theory confirmed using novel experimental techniques. The theoretical approach is then extended to assess the influence of matching and backing on transducer sensitivity and bandwidth. Throughout, the influence of air propagation is included in the simulation approach and highlighted where this factor is significant. The work is expected to provide useful design guidelines for the practical ultrasonic engineer.
Modal truncation issues in synthesis procedures for vibratory power flow and dissipation
Authors: Rook Todd E. , Singh Rajendra
Published: October 2005

Truncation of component modes in synthesis techniques may cause significant errors in the calculation of localized harmonic vibration responses and power flows. Two alternate approaches are proposed to reduce the effects of such errors, and the third approach which combines both with mixed analytical orthonormal bases has been found to be most successful. These concepts are integrated in mobility and modal methods of computing accelerances, input power, transmitted power, and modal dissipation efficiency spectra. Two example cases, namely, the T-beam and a plate–beam structure, are utilized for comparative evaluation of truncation effects. Limited experimental results verify the proposed calculation procedure.
Full-spectrum signal processing using a classify-before-detect paradigm
Authors: Shin Frances B. , Kil David H.
Published: October 2005

In order to effectively deal with quiet source emissions and elevated ambient noise level in littoral waters, it is important that one understand and exploit the underlying signal microstructure. Experiences indicate that thorough understanding of signal structures is a key to designing robust detection and signal processing algorithms. Therefore, classify-before-detect algorithms are designed and their performance evaluated with passive broadband (PBB) data corrupted by the SWell-EX1 shallow water ambient noise collected near San Diego, CA. The processing strategy is based on (1) exploitation of any microstructure present in target signature by projecting raw data onto appropriate low-dimensional projection spaces, (2) identification of key parameters or ‘‘features’’ crucial in determining the presence of signal, and (3) designing a classifier topology that best matches the underlying feature distribution to minimize modeling errors. Full-spectrum signal processing algorithm design is facilitated by the use of an integrated classification paradigm that takes advantage of an inherent relationship between low-dimensional features and classifier architecture. The analysis results based on the classified PBB signal and the SWell-Ex1 ambient noise indicate that taking advantage of the PBB microstructure improves detection performance by an average of 5 to 15 dB over that of a traditional energy detector.
Fractal noise strength in auditory-nerve fiber recordings
Authors: Kelly Owen E. , Johnson Don H. , Delgutte Bertrand , Cariani Peter
Published: October 2005

Discharge patterns recorded from single auditory-nerve fibers have demonstrated long-range dependence, with the count variance-to-mean ratio growing as a power of the counting time for times greater than 0.1–1 s. The intent of this study is to provide a large dataset to enable a more detailed investigation of this phenomenon. Based on 108 recordings from a cat, we conclude that the presence of the fractal noise in the discharge rate is independent of characteristic frequency and stimulus level, but does depend on discharge rate. We measured the low-frequency power of the fractal noise, finding its coefficient of variation to range between 6% and 26% and to decrease as firing rate increases. Such behavior is consistent with multiplicative fractal variations in models of the hair cell membrane permeability to neurotransmitter. Measured standard deviations of spike rate correspond to a sound-pressure level difference limen of approximately 1 dB.
The effect of test signal type and bandwidth on the categorical scaling of loudness
Authors: Ricketts Todd A. , Bentler Ruth A.
Published: October 2005

Recently several methods for obtaining clinical measures of loudness growth through the use of categorical scaling (CS) have been proposed for the selection of hearing aids. These methods use differing test signals or suggest frequency-specific level corrections in an attempt to reflect the loudness perception of hearing aid-processed speech. While some decisions regarding the stimuli utilized for loudness perception procedures are based on measured relationships to speech signals, the effect on loudness perception of changing signal type and bandwidth (as measured by CS) remains unclear. The relationships between the CS loudness growth of signals of differing type, (pure tones, noise bands, filtered/temporally inverted/passband speech) and bandwidth were examined for subjects with both normal and impaired hearing. Results suggest that when the bandwidth is similar (e.g., pure tone and 1/3 oct), signal type does not have significant bearing on loudness perception. As expected, increasing the bandwidth beyond the critical band affected loudness growth, as wideband speech stimuli were judged to be significantly louder than narrow-band speech at equivalent overall sound levels. In this investigation, similar loudness growth patterns were noted across category ratings for all test signal bandwidths. In contrast, loudness growth data obtained using an intelligible speech signal [Cox et al., The American Academy of Audiology (1994a)], revealed loudness growth patterns for speech were fundamentally different than those obtained for tones. Implications for hearing aid fitting strategies are discussed.
Temporal asymmetry in the auditory system
Authors: Irino Toshio , Patterson Roy D.
Published: October 2005

When a damped exponential with a half-life of 4–8 ms is repeated every 25–50 ms and used to modulate a sinusoid or a wideband noise, it suppresses the sound quality typically associated with the carrier. When the envelopes of these ‘‘damped’’ sounds are reversed in time, producing ‘‘ramped’’ sounds, a continuous component with the sound quality of the carrier is restored to the perception. This paper presents an experiment that measures the temporal asymmetry revealed by this perceptual contrast. A ramped sinusoid or noise with a given half-life was presented with a damped sinusoid or noise having the same or greater half-life, to determine the damped half-life required to produce a continuous component with the equivalent relative strength in the two sounds. The results with sinusoidal carriers show that the half-life of the damped sound has to be, on average, about five times the half-life of the ramped sound if the tonal component of the two perceptions is to have the same relative strength. The asymmetry for the noise carrier is about half that of the sinusoidal carrier and, again, the damped sound has the greater matching half-life. Several multichannel auditory models based on a gammatone filterbank are used to try to explain the data in terms of traditional leaky integration, but they produce neither sufficient asymmetry nor the correct pattern of asymmetry. A ‘‘delta-gamma’’ theory is then developed to provide a framework for understanding temporal asymmetry in the auditory system. The theory is used to compare the temporal asymmetry produced by several auditory models and to explain when and how they can accommodate the perceptual asymmetry observed in the experiments.
Perception of back vowels: Effects of varying F1−F Bark distance
Authors: Fahey Richard P. , Diehl Randy L. , Traunmüller Hartmut
Published: October 2005

In a study of vowel height perception using front vowels, Hoemeke and Diehl [J. Acoust. Soc. Am. 96, 661–674 (1994)] found that F1−F0 distance was the best predictor of perceived vowel height for the phonological distinction [±high], while for two other vowel height distinctions F1 alone was the best predictor. Further, the [±high] identification function was defined by a sharp boundary located at 3- to 3.5-Bark F1−F0 distance. One hypothesis offered was that F1−F0 distance had cue value for the [±high] distinction because of an underlying quantal region on the F1−F0 distance dimension. However, the results are also predicted if it is supposed that F1−F0 distance is a cue for vowel height only for pure height distinctions. The present study further tested these possibilities, using back vowels. The results allowed us to reject both as general explanations of vowel height perception. However, the results were consistent with a third possible explanation, namely, that phonetic quality is determined by the tonotopic distances between any adjacent spectral peaks (e.g., F3−F2, F2−F1, and F1−F0), with greater perceptual weight accorded to smaller distances.
Effect of temporal modulation reduction on spectral contrasts in speech
Authors: Drullman Rob , Festen Joost M. , Houtgast Tammo
Published: October 2005

In this paper the effect of temporal modulation reduction on spectral contrasts is investigated. First, a spectral modulation transfer function (SMTF) is presented as a method to measure the transfer of spectral ripples (sinusoidal periods/oct) in the short-time spectral envelope by comparing the spectral modulation depth of original and processed speech fragments. Measuring the SMTF for speech subjected to uniform reduction of the temporal modulation depth (i.e., modulation-frequency-independent reduction) in 24 1/4-oct bands showed an almost equal uniform reduction of the spectral modulations. Furthermore, the SMTF was used to measure the reduction of spectral contrasts associated with low-pass and high-pass temporal-envelope filtering [Drullman et al., J. Acoust. Soc. Am. 95, 1053–1064 and 2670–2680 (1994a, b)]. For a perceptual evaluation, sentences were processed to reduce spectral contrasts and the speech-reception threshold (SRT) in noise was measured with ten normal-hearing subjects. Comparison of the results with those obtained previously after temporal-envelope filtering revealed that the SRT-effect of temporal high-pass filtering can be completely accounted for by the associated reduction of spectral contrasts. However, this relationship cannot be demonstrated conclusively in the case of temporal low-pass filtering.
Quad-band excitation for low bit rate speech coding
Authors: Chiu K. M. , Ching P. C.
Published: October 2005

The excitation parameters of a multiband excitation model for speech production consist of a pitch period and a series of voiced/unvoiced (v/uv) decisions for a number of fixed frequency bands around the harmonics of the fundamental. In this paper, it is shown that, at most, four v/uv variable-length nonoverlapping frequency bands spanning over the telephone bandwidth are adequate to represent the excitation spectrum that provides an improved modeling of mixed voicing and noisy speech. A quad-band excitation (QBE) method is presented which generates excitation source for a linear prediction vocoder for low bit rate transmission of speech signal and the DRT scores validate the potential of the method.
Comment on ‘‘Ray chaos in underwater acoustics in view of local instability’’ [J. Acoust. Soc. Am. 94, 2739–2745 (1993)]
Authors: Tappert F. D.
Published: October 2005

The local instability view of ray chaos in underwater acoustics, as introduced by J. Yan [J. Acoust. Soc. Am. 94, 2739–2745 (1993)], is shown to be false and misleading. A correct approach to understanding the physics of ray chaos is provided by the parametric instability view, in which ray chaos is caused by resonances between ray periods in range and sound-speed perturbation wavelengths.
Bose–Einstein correlations and sonoluminescence
Authors: Trentalange S. , Pandey S. U.
Published: October 2005

Sonoluminescence may be studied in detail by intensity correlations among the emitted photons. As an example, an experiment to measure the size of the light-emitting region by the Hanbury Brown–Twiss effect is discussed. It is shown that single bubble sonoluminescence is almost ideally suited for study by this method and that plausible values for the physical parameters are within easy experimental reach. A sequence of two- and higher-order photon correlation experiments is outlined.
Time-domain shallow-water environmental inversion using unknown broadband sources.
Authors: Roginsky Jacob
Published: October 2005

Inversion for environmental parameters using both simulated and actual experimental data was performed based on the propagation results for presumably unknown broadband sources. The environment is a shallow- water environment and all computations are performed in the time domain. The inversion is based on the least-square comparison between the results of a source deconvolution for each of several receivers. Because single-receiver source deconvolution in underwater acoustics is an intrinsically ill-posed problem, the Tichonov–Philips regularization is incorporated into the current procedure. The method is made efficient by the use of a new deconvolution algorithm that specifically takes advantage of the triangular Toeplitz structure of the propagation matrix [J. Roginsky and G. W. Stewart, J. Acoust. Soc. Am. 97, 3290 (A) (1995)]. The advantages of this method are: (a) The process can be performed with as few as two receivers; (b) no a priori  source information is required; (c) due to one’s ability to work with shorter time windows, the procedure can be made faster than a corresponding frequency domain approach. [Work supported by ONR.]
Robust ray path identification for ocean acoustic tomography.
Authors: Deffenbaugh Max , Schmidt Henrik , Bellingham James G.
Published: October 2005

Acoustic tomography in a ray environment is a two-step process. First, each measured ray arrival time in the received multipath structure is identified with a particular predicted ray path. Second, the differences between the measured arrival times and the predicted arrival times for the represented ray paths are used in a linear inversion to calculate corrections to parameter values describing the sound-speed structure. If measured arrival times are identified with the wrong ray paths, errors will result in the linear inversion. In deep ocean tomography, the time spacing between ray arrivals is typically large compared to the parameter induced changes in arrival times, so ray path identification is not difficult. In shallow water, however, ray path identification can be more challenging. An algorithm is presented that combines the ray path identification step with the linear inversion step to allow tomography using rays where the parameter induced arrival time shifts may be larger than the time spacing between arrivals. The performance of the algorithm is simulated for a typical shallow-water environment. [Work supported by ONR.]
Second-order analysis of eigenray displacement: When does Fermat’s principle apply?
Authors: McDonald B. Edward , Collins Michael D. , Bernstein Ira B.
Published: October 2005

In the ocean sound channel multiple eigenrays, each possessing stationary travel time, may connect two fixed points. In a highly structured propagation environment, how does one determine if the travel time of a given eigenray is a local minimum (Fermat’s principle), maximum, or saddle point with respect to ray parameters? A second-order analysis of the travel time integral along an eigenray is carried out to reveal conditions determining the nature of the stationarity. In three dimensions, the problem reduces to a second-order differential/diadic eigenvalue equation along the ray. In two dimensions, it becomes a scalar Sturm–Liouville eigenvalue problem. An analytic example is given in which both maximum and minimum travel time eigenrays exist. Conditions for ray chaos in the analytic example are derived and related to the occurrence of maximum travel time eigenrays. [Work supported by NRL.]
Mode coupling effect of a cold eddy in Taiwan’s Northeast Sea.
Authors: Chen Chi-Fang
Published: October 2005

The Kuroshio current turns toward the north-east while it passes the Okinawa Trough in Taiwan’s Northeast Sea. In this region, there are different waters mixing, namely, water from the Taiwan Strait, water of the East China Sea, and the Kuroshio current. During the year, except for the summer months, the Kuroshio current is characterized by its distinct temperature difference from other waters, i.e., the Kuroshio front and cold eddies are two predominant features in this region. The frontal effect on acoustic propagation has been studied and reported in a previous talk. In this paper, the coupling effect of modes when acoustic signals transmit through the cold eddy using both the Parabolic Equation method and the Adiabatic Mode Approximation is reported. Severe mode coupling is realized while the sound transmits through the cold eddy. [Work supported by National Science Council of Republic of China.]