bluuebunny/crossref_metadata_2025 huggingface dataset:
Group delay in resonant scattering
Authors: He H. , Lyon R. H.
Published: October 2005

For a slightly damped structural system with low modal overlap, roughly half the zeros of the mobility transfer function (MTF) remain on the pole line, and the group delay of the MTF is π/2 times the structural modal density. But in the case of sound scattering, the zeros are translated and rotated randomly and far fewer zeros will remain on the pole line. It is then reasonable to conjecture that the phase of the resonant scattering function (RSF) is determined by the number of poles alone, and thus the group delay of the RSF is roughly a factor of 2 times of that of the MTF. To verify this conjecture, an in-air plate scattering experiment was carried out and the results show a factor of 1.67. Furthermore, the zero density distribution patterns versus modal overlap for both the MTF and RSF were obtained through numerical simulation of a 20-degree-of-freedom system. The simulation shows that in the smaller modal overlap case, the RSF group delay is nearly twice that of the MTF. When modal overlap increases, however, this factor decreases and approaches unity. Physically this means in a high modal overlap system, as in room acoustics, the group delay of the RSF is determined by the energy decay rate.
Development of a new standard laboratory protocol for estimating the field attenuation of hearing protection devices. Part I. Research of Working Group 11, Accredited Standards Committee S12, Noise
Authors: Royster Julia Doswell , Berger Elliott H. , Merry Carol J. , Nixon Charles W. , Franks John R. , Behar Alberto , Casali John G. , Dixon-Ernst Christine , Kieper Ronald W. , Mozo Ben T. , Ohlin Doug , Royster Larry H.
Published: October 2005

This paper describes research conducted by Working Group 11 of Accredited Standards Committee S12, Noise, to develop procedures to estimate the field performance of hearing protection devices (HPDs). Current standardized test methods overestimate the attenuation achieved by workers in everyday use on the job. The goal was to approximate the amount of attenuation that can be achieved by noise-exposed populations in well-managed real-world hearing conservation programs, while maintaining acceptable interlaboratory measurement variability. S12/WG11 designed two new laboratory-based protocols for measuring real-ear attenuation at threshold, with explicit procedures for subject selection, training, supervision, and HPD fitting. After pilot-testing, S12/WG11 conducted a full-scale study of three types of earplugs and one earmuff tested by four independent laboratories using both protocols. The protocol designated as ‘‘subject-fit’’ assessed the attenuation achieved by subjects who were experienced in threshold audiometry, but naive with respect to the use of hearing protection, when they fit HPDs by following manufacturers’ instructions without any experimenter assistance. The attenuation results from the subject-fit method corresponded more closely to real-world data than results from the other protocol tested, which allowed the experimenter to coach subjects in HPD use. Comparisons of interlaboratory measurement variability for the subject-fit procedure to previous interlaboratory studies using other protocols indicated that the measurements with the new procedure are at least as reproducible as those obtained with existing standardized methods. Therefore, the subject-fit protocol was selected for consideration for use in future revisions of HPD attenuation test standards.
Chaos in ocean ambient ‘‘noise’’
Authors: Frison Ted W. , Abarbanel Henry D. I. , Cembrola Joan , Neales Bert
Published: October 2005

Using a data analysis toolkit designed to explore data from nonlinear systems using time domain methods, it has been determined that the observed number of degrees of freedom in one pristine measurement of ocean ambient background pressure fluctuations or ‘‘noise’’ is nine. While the true number of degrees of freedom in the ocean is probably large, the observed measurements have nine degrees of freedom. There is a positive Lyapunov exponent, which identifies the system as being chaotic. The largest exponent is very large, indicating that the prediction horizon for these data is confined to a few samples. Determination of the degrees of freedom is important for the construction of physical models and nonlinear noise reduction filters, which may be based on characteristics of the observed few degrees of freedom from the background acoustic source. The magnitude of the largest Lyapunov exponent provides a measure of confidence for signal state prediction and mitigation.
Steady-state sinusoidal velocity responses of the basilar membrane in guinea pig
Authors: Nuttall Alfred L. , Dolan David F.
Published: October 2005

This report provides a detailed analysis of tone-evoked velocity responses of basilar membrane (BM) motion measured in the basal turn of the guinea pig cochlea. A laser Doppler vibrometer, coupled to a compound microscope, measured the velocity of reflective microbeads placed onto the scala tympani surface of the BM. The velocity responses of the stapes footplate were also determined, allowing the calculation of a BM transfer function. The normal transfer function is compared to that seen with cochlear ‘‘insensitivity’’ and postmortem. This comparison results in measures of the active process contribution to the magnitude and phase of the BM transfer function. It was found that the active process contributed as much as 65 dB of ‘‘gain’’ and 270° of phase lag at the best frequency. Other details about features of input/output velocity functions and the derived mechanical frequency-tuning curve at a criterion of 50 μm/s are analyzed.
Involvement of the olivocochlear bundle in the detection of tones in noise
Authors: Micheyl Christophe , Collet Lionel
Published: October 2005

To investigate the involvement of auditory efferents in hearing-in-noise in humans, olivocochlear bundle (OCB) functioning and detection-in-noise abilities were compared in 30 subjects. OCB function was assessed in terms of contralateral attenuation of evoked otoacoustic emissions (EOAE): i.e., the reduction in EOAE amplitude elicited by a 30-dB SL contralateral broadband noise. Correspondingly, the detection thresholds for 1- and 2-kHz tone pips embedded in 50-dB SPL broadband noise were measured in the same ear as the EOAEs, successively in the presence and in the absence of a 30-dB SL broadband noise in the opposite ear. The shifts in detection threshold induced by the contralateral stimulation could thus be compared to those in EOAEs. The results indicated significant statistical correlations between the contralateral attenuation of EOAEs and (1) the detection threshold of the 2-kHz signal and (2) the contralaterally induced shift in the 1- and 2-kHz thresholds. Furthermore, the correlation between contralaterally induced reduction of EOAE amplitude and contralaterally induced threshold shift was observed only in the group of subjects who had first performed the detection task in the presence of contralateral stimulation. These results, which suggest that OCB is involved in detection of tones in noise in humans, are discussed in relation to previous physiological and behavioral studies of OCB function.
Directional masking of phase locking in the amphibian auditory nerve
Authors: Wang Jianxin , Narins Peter M.
Published: October 2005

Directional masking in the amphibian auditory periphery was investigated by presenting frogs with a continuous tone from above and a continuous broadband noise from four different horizontal directions. This paradigm mimics the natural situation in which frogs are located in three-dimensional space and interference can and does arise from any direction. Intracellular recordings were made from single auditory-nerve fibers of the anesthetized adult leopard frogs using a dorsal approach. Vector strength (VS) and the mean preferred firing phase (MP) were measured for 94 low-frequency fibers. Thirty-six percent of the fibers demonstrated direction sensitivity of noise masking of VS. Most fibers exhibited a maximum decrease in VS at 90° or 270° noise incident angle and a minimum decrease in VS at 0° or 180° noise incident angle, suggesting higher noise susceptibility to the lateral fields than to the anterior or posterior field. Forty-nine percent of the fibers demonstrated direction sensitivity of noise masking of MP. Maximum shift in MP occurred most often at 90° or 180° noise incident angle, whereas minimum shift in MP occurred most frequently at 0° or 270° noise incident angle, suggesting higher noise susceptibility to the ipsilateral or posterior field than to the contralateral or anterior field. The difference in directionality patterns of VS and MP suggests different mechanisms underlying noise masking of these two measures of phase locking in the amphibian auditory nerve.
Detectability of increments and decrements in spectral profiles
Authors: Ellermeier Wolfgang
Published: October 2005

In auditory profile analysis, the subject typically has to discriminate a standard spectrum consisting of widely spaced equal-amplitude sinusoids from a comparison, in which one or several components have been elevated relative to the others. According to the widely accepted multichannel model, however, it should not matter whether the spectral shape alteration consists of incrementing or decrementing a component by a small number of decibels. Thus, in order to investigate the generality of the hypothesized mechanism, and to explore the role of pitch salience cues, which might be thought to favor increments to single components, two experiments comparing the detectability of intensity increments and decrements in spectral profiles were conducted. In experiment 1, in which the number of components was varied from 3 to 15 within a fixed frequency range, decrements to the central 800-Hz component produced significantly larger thresholds than did increments. Experiment 2, which employed three-tone complexes spanning different frequency ranges, revealed that this effect is entirely due to the spectral density of the frequency components: As the distance between the variable signal component and the flanking reference sinusoids decreased, the increment/decrement disparity became larger. These effects may—at least qualitatively—be accounted for when peripheral excitation patterns are considered, suggesting that local decrements are constrained more than increments by the excitation intruding from flanking stimulus components.
A comparison of hearing-aid array-processing techniques
Authors: Kates James M. , Weiss Mark R.
Published: October 2005

Microphone arrays have proven effective in improving speech intelligibility in noise for hearing-impaired listeners, and several array processing techniques have been proposed for hearing aids. Among the signal-processing approaches are classical delay-and-sum beamforming, superdirective arrays, and adaptive arrays. To directly compare the effectiveness of these different processing strategies, a 10-cm-long linear array was built using five uniformly spaced omnidirectional microphones. This array was used in the end-fire orientation to acquire speech and noise signals for a variety of array placements in two representative rooms. Both digital and simulated analog processing techniques were considered, with the array processing implemented in the frequency domain. The performance metric was the steady-state array gain weighted to represent the relative importance of the different frequency regions in understanding speech. The processing comparison indicates that digital systems are more effective than the simulated analog processing, and that both superdirective and adaptive digital array processing can provide more than 9 dB of weighted array gain.
Duration and fundamental frequency correlates of phrase boundaries in productions by children and adults
Authors: Katz William F. , Beach Cheryl M. , Jenouri Kathleen , Verma Sushama
Published: October 2005

Two experiments examined how children and adults produce acoustic correlates for phrase boundaries during speech. Adults and children (ages 5 and 7) were asked to describe groupings of colored blocks, first in a relatively spontaneous manner and next under more structured conditions designed to elicit grouping information concerning ‘‘which blocks go together.’’ In the spontaneous condition, adults gave elaborate descriptions of block positions and color, whereas children produced short descriptions such as ‘‘pink, green, white;’’ ‘‘pink, green, and white;’’ and ‘‘pink and green and white.’’ In the structured condition, all subjects produced utterances corresponding to three syntactic bracketings of the phrase ‘‘pink and green and white:’’ [pink and (green and white)]; [(pink and green) and white]; and [pink and green and white]. Acoustic analyses indicated that adults reliably control both duration and fundamental frequency (F0) to signal phrase boundaries, whereas children of both age groups demonstrate little evidence of either type of information being used. We interpret these finding as suggesting that children as old as age 7 do not produce prosodic cues for this type of standing ambiguity in their everyday speech. Possible reasons for this lack of phrase boundary prosodic correlates are examined.
Inhomogeneous plane-wave scattering and mode stimulation on periodic rough surfaces
Authors: Van Den Abeele Koen E.-A. , Briers Rudy , Leroy Oswald
Published: October 2005

Medium vibration properties to characterize interface layers and quality of bonding can be examined by an ordinary approach using homogeneous waves or by a more general inhomogeneous (or complex harmonic) wave scattering technique. It is known that only particular inhomogeneous plane waves can stimulate eigenvibrations of a given structure, and not the homogeneous wave. The reflection and transmission of such inhomogeneous waves is investigated for plane parallel interfaces as well as their scattering at periodically corrugated boundaries between liquid and solids. The influence of plate thickness, corrugation periodicity, and height on the occurrence of specific plate modes is examined. Using an alternative description of a bounded ultrasonic beam as a finite superposition of inhomogeneous waves, this theory can be applied to examine the deformation of Gaussian profiles and to explicitly relate this deformation to the stimulation of mode vibrations. The generation of a plate—or interface—mode by an obliquely incident single inhomogeneous wave on a plane parallel plate—or half-space interface boundary—and the scattering of inhomogeneous waves at the interface wave stimulated corrugated surface, also suggest a new interpretation of back reflection and transmission of bounded beams at smooth liquid–solid interfaces.
Acoustics and musical qualities
Authors: Beranek Leo
Published: October 2005

This study examines the known acoustical attributes of concert halls and depicts the ways in which they interrelate with the music performed in them. The first section distinguishes between direct sound, early sound, and reverberant sound. The second section concerns how musical factors and acoustical attributes affect vertical and horizontal definition of the music. Figures illustrate the ways that the sounds of fast and slow music are altered by different acoustical conditions. The final section discusses the important acoustical attributes, intimacy, spaciousness, timbre, and tone color.
Wave propagation in anisotropic, saturated porous media: Plane-wave theory and numerical simulation
Authors: Carcione José M.
Published: October 2005

Porous media are anisotropic due to bedding, compaction, and the presence of aligned microcracks and fractures. Here, it is assumed that the skeleton (and not the solid itself) is anisotropic. The rheological model also includes anisotropic tortuosity and permeability. The poroelastic equations are based on a transversely isotropic extension of Biot’s theory, and the problem is of plane strain type, i.e., two dimensional, describing qP−qS propagation. In the high-frequency case, the (two) viscodynamic operators are approximated by Zener relaxation functions that allow a closed differential formulation of Biot’s equation of motion. A plane-wave analysis derives expressions for the slowness, attenuation, and energy velocity vectors, and quality factor for homogeneous viscoelastic waves. The slow wave shows an anomalous polarization behavior. In particular, when the medium is strongly anisotropic the polarization is quasishear and the wave presents cuspidal triangles. Anisotropic tortuosity affects mainly the slow wavefront, and anisotropic permeability produces strong anisotropic attenuation of the three modes. The diffusive characteristics of the slow mode are predicted by the plane-wave analysis. As in the single-phase case, it is confirmed that the phase velocity is the projection of the energy velocity vector onto the propagation direction. Moreover, some fundamental energy relations, valid for a single-phase medium, are generalized to two-phase media. Transient propagation is solved with a direct grid method and a time-splitting integration algorithm, allowing the solution of the stiff part of the differential equations in closed analytical form. The snapshots show that the three waves are propagative when the fluid is ideal (zero viscosity). It is confirmed that, when the fluid is viscous, the slow wave becomes diffusive and appears as a static mode at the source location. The modeling confirms the triplication (cusps) of the slow wave and the polarization behavior predicted by the plane analysis.
The nonlinear interaction of two plane waves in a viscous medium
Authors: Jiang Zhong-Yue , Greenleaf James F.
Published: October 2005

Earlier studies [P. J. Westervelt, J. Acoust. Soc. Am. 29, 199–203, 934–935 (1957)] of the mutual nonlinear interaction of two plane waves of sound with each other are extended to include the viscous effect. The viscous effect is considered both from the equations of motion and the equation of state of the medium. An analytical solution to the lowest-order scattering process is obtained if the viscous effect of second order and higher can be neglected.
Parameter estimation using multifrequency range-dependent acoustic data in shallow water
Authors: Gerstoft Peter , Gingras Donald F.
Published: October 2005

The estimation of all forward model parameters—geometric, geoacoustic, and ocean sound speed—by the inversion of acoustic field observations is considered. The data was taken at a mildly range-dependent shallow water site in the Mediterranean Sea. The inversion is based on data from a vertical array and carried out using information at multiple frequencies. Global optimization using a directed Monte Carlo search based on genetic algorithms and the Bartlett objective function is used. All geometric parameters are well determined, a range-dependent geoacoustic model is determined, and the ocean sound speed is estimated. Comparisons of the observed pressure field as a function of depth and the predicted field show good agreement. The use of observations at multiple frequencies provides considerable stability for the estimated parameters. Optimization of only geometric and geoacoustic parameters in a range-independent environment is found to be satisfactory at the lower frequencies (165–175 Hz), but for the higher frequencies (325–335 Hz) optimization of additional parameters by inclusion of either a range-dependent forward model or the ocean-sound-speed profile seems essential for successful inversion.
Dynamic response and power flow in two-dimensional coupled beam structures under in-plane loading
Authors: Farag N. H. , Pan J.
Published: October 2005

This paper is concerned with the prediction of dynamic response of planar coupled beam structures in the low and medium frequency ranges. Based on the receptance concept, the modal properties of the components of the coupled systems with specific boundary conditions are used to form the receptance matrix for the determination of the internal force and displacement response of the coupled structures. Only in-plane loading is considered here and so the structural response will include the longitudinal and in-plane flexural waves only and the torsional and out-of-plane flexural vibrations are not considered here. The mechanism of power flow through the joint boundaries of the in-plane coupled beam structures is investigated by calculating the power flow components of different wave types. The results from the receptance model are compared with that from the finite element analysis and the traveling wave solutions. Good agreement was found. Examples of connected beams are presented, and the characteristics of the power flow and wave interaction are highlighted.
Theoretical study of perturbation method for acoustic multipole logging in anisotropic formation
Authors: Zhang Bixing , Wang Kexie
Published: October 2005

A new and effective analytical perturbation method is presented for the multipole acoustic logging in a transversely isotropic elastic solid whose symmetric principal axis is perpendicular to the borehole axis. The transversely isotropic elastic solid is regarded as a relevant isotropic elastic solid added to the perturbations, and three perturbation quantities about moduli deviated from the isotropic medium are introduced. By selecting a group of displacement potentials and a cylindrical coordinate system oriented along the borehole axis, the zero- and first-order perturbation solutions of the multipole acoustic field are derived for the weak transversely isotropic elastic solid which has its symmetric principal axis perpendicular to the borehole axis. The acoustic fields inside and outside the borehole excited by a multipole source are investigated. It is found that not only the nth multipole acoustic field can be excited by an nth multipole source, but the multipole fields whose orders are higher and lower than n also can be excited by an nth multipole source.
Influence of gear errors on acceleration noise from spur gears
Authors: Wang Yu-Fang , Tong Zhong-Fang
Published: October 2005

In this paper, using the theory of sound radiated from the impact of two cylinders side by side and regarding the meshing impulse of two gears as that of two cylinders with variable curvature radii, an acoustical model is established for acceleration noise from meshing impulse of spur gears and the mechanism of radiating acceleration noise and the influence of gear errors on acceleration noise are studied theoretically. Then a program for calculating acceleration noise is presented and the influence of several kinds of spur gear errors on the noise is discussed. The conclusions are drawn by comparing the measured results with the theoretical ones.
The ‘‘Schroeder frequency’’ revisited
Authors: Schroeder Manfred R.
Published: October 2005

It is noted that the cross-over frequency that marks the transition from individual resonances of a multimode system to overlapping normal modes, when expressed as a cross-over wavelength, equals—within a numerical constant—the diffuse-field distance in both three- and two-dimensional resonators.
Comments on ‘‘Manipulations of the duration and relative onsets of two-tone forward maskers’’ [J. Acoust. Soc. Am. 94, 1269–1274 (1993)]
Authors: Bacon Sid P.
Published: October 2005

Champlin and Wright {‘‘Manipulations of the duration and relative onsets of two-tone forward maskers’’ [J. Acoust. Soc. Am. 94, 1269–1274 (1993)]} examined the effects of masker duration in forward masking with one- and two-tone maskers. They found, among other things, that the amount of psychophysical suppression increases as the temporal overlap between the two masker components increases. They proposed a two-stage neural model to account for this finding. The purpose of this Letter is to show, experimentally, that their results are consistent with an explanation based on mechanical suppression.
Precision ultrasonic reflection studies in fluid-coupled plates
Authors: Lobkis O. I. , Safaeinili A. , Chimenti D. E.
Published: October 2005

An approximate, but highly accurate, analysis is presented for the reflection of bounded acoustic beams—and their detection by finite receivers—from fluid-loaded structures, demonstrating the relationship between the plane-wave reflection coefficient and the transducer voltage. The correspondence of the reflection coefficient zeros, in both angle and frequency, with the observed voltage minima is found to depend critically on the experimental geometry, especially the lateral transducer placement. In measurements with two identical transducers, the beam shape, its sidelobes, and far-field or near-field conditions are found to play a relatively minor role in the receiver voltage. Instead, the size of the transducers and their relative lateral positioning with respect to the sample are the major geometrical factors determining the appearance, width, and depth of reflection minima. A series of precision, swept-frequency experiments on a uniform, homogeneous plate to validate the calculation and expose any possible limitations is also reported here. In general, excellent detailed agreement between the efficient approximate calculation and the results of the experiments has been obtained. An expression is derived to predict the optimal transducer positioning for accurate estimation of reflection coefficient zeros from voltage measurements. These results have significance for material property extraction from reflection measurements on fluid-loaded structures.
Numerical simulation of active control with on-line system identification on sound transmission through an elastic plate
Authors: Koshigoe Shozo , Teagle Allen , Tsay Ching-Hsu , Morishita Shin , Une Soichro
Published: October 2005

An adaptive control algorithm with on-line system identification capability has been developed. One of the great advantages of this scheme is that an additional system identification mechanism such as an additional uncorrelated random signal generator as the source of system identification [Eriksson and Allie, J. Acoust. Soc. Am. 85, 797–802 (1989)] is not required. A time-varying plate-cavity system is used to demonstrate the control performance of this algorithm. The time-varying system consists of a stainless-steel plate which is simply supported on a rigid cavity where the cavity temperature can depend on time. For a given externally located harmonic sound excitation, the system identification and the control are simultaneously executed to minimize the transmitted sound in the cavity. The control performance of the algorithm is examined for two cases. Keeping the cavity temperature constant for the first case, the external disturbance frequency is swept with 2 Hz/s from below to above a resonance frequency of the plate-cavity system. The simulation shows an excellent frequency tracking capability with cavity internal sound suppression of 40 dB. For the second case, the cavity temperature is lowered to a half of its original value in 60 s while the external sound excitation is fixed with a frequency. Hence, the cavity resonant frequency decreases and passes the external sound excitation frequency. The algorithm shows 40 dB transmitted noise suppression without compromising the system identification tracking capability.
Error evaluation of the structural intensity measured with a scanning laser Doppler vibrometer and a k-space signal processing
Authors: Morikawa Ryusuke , Ueha Sadayuki , Nakamura Kentaro
Published: October 2005

In structural intensity measurements, the calculation error in the higher-order spatial derivatives contained in the derivation has a large effect on the measurement accuracy, since the derivative operations magnify the noise. To overcome the difficulty in calculating the derivatives, the authors employ the k-space processing which is based on the Fourier transform. Then, in this paper, a k-space filter is introduced to reduce the noise further. On the other hand, a noncontact method to measure the vibration distribution is necessary in order to avoid the loading effect on the specimen. An optical method is one of the most promising candidates for this purpose. This paper presents an error evaluation of the structural intensity as measured with a scanning laser Doppler vibrometer and the k-space signal processing. The effectiveness of the combination of the noncontact optical method and the k-space method is confirmed by both simulations and experiments. First, the error in calculating structural intensity is examined numerically using a one-dimensional beam model. As a result, it became clear that the cutoff wave number for k-space filtering should be one and a half of the wave number of the measured vibration to minimize the influence of the error in the measured data. Furthermore, basic measurement conditions such as the minimum number of data points and the sampling rate are studied for practical use of the k-space method. Lastly, the results of the numerical studies are confirmed by the experiments for a beam and a two-dimensional plate.
Parameter resolution bounds that depend on sample size
Authors: Makris Nicholas C.
Published: October 2005

It is currently common practice in theoretical ocean acoustics to derive parameter resolution bounds for a monochromatic measurement of the temporally fluctuating field received by a hydrophone array. However, a monochromatic measurement corresponds to a single random sample. In applied ocean acoustics, single samples are seldom if ever used for parameter estimation because the associated error can be unnecessarily large. Instead estimates are derived from ensemble averages such as the sample covariance. To bridge the gap between these two approaches, the Fisher Information for the sample covariance is shown to be equal to the number of independent and stationary samples times the Fisher Information for a single sample. Therefore, there are no practical limits on parameter resolution if (1) the bound for a single sample is finite, which is generally the case of interest, (2) a sufficiently large population of independent samples can be found. The parameter resolution issue then becomes one of determining the maximum number of such samples. This number is set by physical variables that do not appear in the monochromatic or instantaneous measurement. A means of determining this number from the temporal coherence of the received field and the measurement time is presented.
Strongly nonlinear waves and streaming in the near field of a circular piston
Authors: Yano Takeru , Inoue Yoshinori
Published: October 2005

The propagation of nonlinear waves radiated by a circular piston mounted in an infinite plane rigid wall is numerically studied without the restriction of weak nonlinearity, in the case that the radius of piston is comparable with a typical wavelength of the radiated wave. The piston executes harmonic oscillations and the wave is thereby emitted into an ideal gas of semi-infinite extent, in which the dissipation effect is supposed to be negligible everywhere except for the discontinuous shock front. The wave phenomenon in the near field caused by the strongly nonlinear effect combined with the diffraction effect is clarified by solving the Euler equations with the upwind finite difference scheme. Owing to the strong nonlinearity, not only the waves emitted directly from the piston face but also the diffraction waves from the edge of the source are distorted and developed into the shock waves. This can lead to a multiple interference of shock waves in the near field. The separation phenomenon at the edge is also shown. Another remarkable phenomenon is the excitation of strong streaming (a mean mass flow), which forms a vortex-ring-like flow pattern and rarefies the gas near the source during the several periods of oscillation of the piston. By using a regular perturbation expansion, acoustic streaming in the weakly nonlinear problem is also analyzed, which does not show such a vortex-ring-like flow pattern and never rarefies the gas near the source.
Effects of nonlinear interaction on measurements of frequency-dependent attenuation coefficients
Authors: Wu Junru
Published: October 2005

It was experimentally found that attenuation coefficient of a high-density polyethylene sample determined by the ultrasonic spectroscopy technique strongly depends on the pressure amplitude of an incident broadband pulse applied. This result can be explained by the self-nonlinear interaction of different frequency components of an incident broadband ultrasonic pulse (the parametric end-fire array effect). To minimize the error due to the nonlinear effect, a guidance for choosing an appropriate pulse amplitude used in measurements based on the shock parameter was suggested.
Design and tone in the mechanoacoustic piano. Part I. Piano hammers and tonal effects
Authors: Conklin, Harold A.
Published: October 2005

Relations between the design of a piano and the quality of its tone are reviewed and discussed from the point of view of an instrument designer. Topics include the effects on tone by the hammers, the voicing, the soundboard, the case, the string plate, and the design of the scale and strings, including longitudinal string modes, wrapped strings, and inharmonicity. Design limitations relating to materials, performance, or tone quality are noted. The effect of varying a parameter is described or illustrated graphically when feasible. Data comparing pianos of various size and design are shown. Examples are shown of the use of mobility measurements in assessing soundboard and string plate performance. The potential value of modal and finite element analysis in design work is noted. Although the piano is regarded by many people as fully developed, the author believes that there has never been a better time for improvement. Some directions for future work are indicated.
Effects of fluid-loading on Lamb mode spectra
Authors: Freedman Albert
Published: October 2005

Light fluid-loading of an infinite, isotropic, elastic plate not only leads to the real modes of the unloaded plate acquiring a small, imaginary component, but also to the imaginary modes acquiring a small, real component. This provides a model with which computations of the leaky Lamb modes are seen to be compatible. The imaginary components of the propagating modes form a ‘‘resonance pattern’’ which contains all the information on the plate’s transmittivity. The level of this pattern increases with the ratio of fluid to plate density. When the latter ratio is large enough to cause the resonance pattern to overlap the peaks of the well-known imaginary semiloops, there is interaction leading to transition from the leaky Lamb mode behavior to that of a plate clamped on its surfaces with slip boundary conditions. There is general agreement with the conclusions of S. I. Rokhlin et al. [J. Acoust. Soc. Am. 85, 1074–1080 (1989)] and the present work broadens the parameter range over which those conclusions have been shown to hold.
The structural acoustics and active control of interior noise in a ribbed cylindrical shell
Authors: Houston B. H. , Marcus M. H. , Bucaro J. A. , Williams E. G. , Photiadis D. M.
Published: October 2005

Numerical studies are carried out regarding the structural acoustics of a ribbed aluminum cylindrical shell structure intended to represent the essential structural features of a small aircraft fuselage. Calculations are made to determine both the wall normal displacements and the interior acoustic pressures for the case in which the shell wall is forced dynamically at a point. The structural responses are further decomposed into their frequency-wave-number components. Through a series of comparisons between those responses for an infinite shell, the ribbed vacuum-filled shell, and the ribbed air-filled shell, the relevant structural acoustic mechanisms are interpreted. The frequencies at which interior acoustic ‘‘resonances’’ are observed are connected to specific mechanisms, including cavity responses driven by structural modes, cavity modes forcing the structure, and mixed structure/air-cavity modes. Numerically based active control experiments are carried out using end actuation, and the relative performance of this control ‘‘system’’ is compared when operating on the various mode types.
Transient elastic waves in finite layered media: Two-dimensional axisymmetric analysis
Authors: El-Raheb Michael , Wagner Paul
Published: October 2005

The analysis of transient linear elastic waves in Ref. [J. Acoust. Soc. Am. 94, 172–184 (1993)] is extended to 2-D axisymmetric finite layered periodic and weakly coupled media. Two essential features distinguishing 2-D propagation are flexure and increased dispersion. To allow separation of z and r eigenproblems, a boundary condition that approximates simple supports is adopted that yields nonorthogonal eigenfunctions in the modal analysis.
Timbral aspects of reproduced sound in small rooms. II
Authors: Bech So/ren
Published: October 2005

This paper is a report on some of the influences of individual reflections on the timbre of reproduced sound. Bech [J. Acoust. Soc. Am. 97, 1717–1726 (1995)] gave the first report. A single loudspeaker with frequency-dependent directivity characteristics, positioned in a room of normal size with frequency-dependent absorption coefficients of the room surfaces, has been simulated using an electroacoustic setup. The model included the direct sound, 17 individual reflections and the reverberant field. The threshold of detection, and just-noticeable differences for an increase in level were measured for individual reflections, using four subjects for noise and three for speech. The results have confirmed the findings of the first report that the first-order floor reflection is likely to individually contribute to the timbre of reproduced noise. However, for a speech signal none of the investigated reflections will contribute individually to the timbre. It is suggested that the threshold of detection is determined by the spectral changes in the dominant frequency range of 500 Hz–2 kHz. For increases in the level of individual reflections, the most likely to be audible is the first-order floor reflection, for speech and noise. For a noise signal, additional reflections from the wall to the left and behind the listener also belong to this group.
Sensitivity of the wave-number domain field separation methods for scattering
Authors: Cheng Ming-Te , Mann J. Adin , Pate Anna
Published: October 2005

The two-surface field separation technique for obtaining the sound field scattered from an object has been shown to be feasible for both the Cartesian and cylindrical coordinate systems [Cheng et al., J. Acout. Soc. Am. 97, 2293–2303 (1995)]. Investigations of the sensitivity of implementing these separation techniques to the measurement parameters and their errors will be reported. The results of this sensitivity investigation are helpful in deciding the accuracy of the far-field target strength results and designing experimental procedures and equipment that ensure accurate results. The separation and the spatial processing parameters that are considered include the distance between measurement points in each measurement surface, the aperture size of each measurement surface, and the distance between measurement surfaces. Recommendations for these parameters are made. Next the sensitivity to errors in the experimental geometry is explored. For the Cartesian coordinate system skew and curvature of the measurement surfaces caused the most significant errors. For the cylindrical coordinate system errors in the measurement cylinder radii and skew caused the most significant errors. In both coordinate systems the errors could not be effectively corrected with signal processing except for the skew in the case of the cylindrical coordinate system.
A quantitative model of the ‘‘effective’’ signal processing in the auditory system. II. Simulations and measurements
Authors: Dau Torsten , Püschel Dirk , Kohlrausch Armin
Published: October 2005

This and the accompanying paper [Dau et al., J. Acoust. Soc. Am. 99, ••–•• (1996)] describe a quantitative model for signal processing in the auditory system. The model combines several stages of preprocessing with a decision device that has the properties of an optimal detector. The present paper compares model predictions for a variety of experimental conditions with the performance of human observers. Simulated and psychophysically determined thresholds were estimated with a three-interval forced-choice adaptive procedure. All model parameters were kept constant for all simulations discussed in this paper. For frozen-noise maskers, the effects of the following stimulus parameters were examined: signal frequency, signal phase, temporal position and duration of the signal within the masker under conditions of simultaneous masking, masker level, and masker duration under conditions of forward masking, and backward masking. The influence of signal phase and the temporal position of the signal, including positions at masker onset, was determined for a random-noise masker and compared with corresponding results obtained for a frozen noise. The model describes all the experimental data with an accuracy of a few dB with the following exceptions: forward-masked thresholds obtained with brief maskers are too high and the change in threshold with a change in signal duration is too small. Both discrepancies have their origin in the adaptation stages in the preprocessing part of the model. On the basis of the wide range of simulated conditions we conclude that the present model is a successful approach to describing the detection process in the human auditory system.
Two cross-linguistic factors underlying tongue shapes for vowels
Authors: Nix David A. , Papcun George , Hogden John , Zlokarnik Igor
Published: October 2005

Desirable characteristics of a vocal-tract parametrization include accuracy, low dimensionality, and generalizability across speakers and languages. A low-dimensional, speaker-independent linear parametrization of vowel tongue shapes can be obtained using the PARAFAC three-mode factor analysis procedure [Harshman et al., J. Acoust. Soc. Am. 62, 693–707 (1977)]. Harshman et al. applied PARAFAC to midsagittal x-ray vowel data from five English speakers, reporting that two speaker-independent factors are required to accurately represent the tongue shape measured along anatomically normalized vocal-tract diameter grid lines. Subsequently, the cross-linguistic generality of this parametrization was brought into question by the application of PARAFAC to Icelandic vowel data, where three nonorthogonal factors were reported [Jackson, J. Acoust. Soc. Am. 84, 124–143 (1988)]. This solution is shown to be degenerate; a reanalysis of Jackson’s Icelandic data produces two factors that match Harshman et al.’s factors for English vowels, contradicting Jackson’s distinction between English and Icelandic language-specific ‘‘articulatory primes.’’ To obtain vowel factors not constrained by artificial measurement grid lines, x-ray tongue shape traces of six English speakers were marked with 13 equally spaced points. PARAFAC analysis of this unconstrained (x,y) coordinate data results in two factors that are clearly interpretable in terms of the traditional vowel quality dimensions front/back, high/low.
Three-dimensional tongue surface shapes of English consonants and vowels
Authors: Stone Maureen , Lundberg Andrew
Published: October 2005

This paper presents three-dimensional tongue surfaces reconstructed from multiple coronal cross-sectional slices of the tongue. Surfaces were reconstructed for sustained vocalizations of the American English sounds /i, ■, e, ε, æ, ■, ■, o, ■, ■, r, l, s, ■, θ, n, ■/. Electropalatography (EPG) data also were collected for the sounds to compare tongue surface shape with tongue–palate contact patterns. The study was interested also in whether 3-D surface shapes of the tongue were different for consonants and vowels. Previous research and speculation had found that there were differences in production, acoustics, and linguistic usage between the two groups. The present study found that four classes of tongue shape were adequate to categorize all the sounds measured. These classes were front raising, complete channel, back raising, two-point displacement. The first and third classes have been documented before in the midsagittal plane [cf. R. Harshman, P. Ladefoged, and L. Goldstein, J. Acoust. Soc. Am. 62, 693–707 (1976)]. The first three classes contained both vowels and consonants, the last only consonants. Electropalatographic patterns of the sounds indicated three categories of tongue–palate contact: bilateral, cross-sectional, and combination of the two. Vowels used only the first pattern, consonants used all three. The EPG data provided an observable distinction in contact pattern between consonants and vowels. The ultrasound tongue surface data did not. The conclusion was that the tongue actually has a limited repertoire of shapes and positions them against the palate in different ways for consonants versus vowels to create narrow channels, divert airflow, and produce sound.
Modeling formant frequency discrimination of female vowels
Authors: Sommers Mitchell S. , Kewley-Port Diane
Published: October 2005

The present investigations were designed to establish the features of vowel spectra that mediate formant frequency discrimination. Thresholds for detecting frequency shifts in the first and second formants of two steady-state vowels were initially measured for conditions in which the amplitudes of all harmonics varied in accordance with a model of cascade formant synthesis. In this model, changes in formant frequency produce level variations in components adjacent to the altered formant as well as in harmonics spectrally remote from the shifted resonant frequency. Discrimination thresholds determined with the cascade synthesis procedure were then compared to difference limens (DLs) obtained when the number of harmonics exhibiting level changes was limited to the frequency region surrounding the altered formant. Results indicated that amplitude variations could be restricted to one to three components near the shifted formant before significant increases in formant frequency DLs were observed. In a second experiment, harmonics remote from the shifted formant were removed from the stimuli. In most cases, thresholds for these reduced-harmonic complexes were not significantly different from those obtained with full-spectrum vowels. Preliminary evaluation of an excitation-pattern model of formant frequency discrimination indicated that such a model can provide good accounts of the thresholds obtained in the present experiments once the salient regions of the vowel spectra have been identified. Implications of these findings for understanding the mechanism mediating vowel perception are discussed.
The periodogram and Allan variance reveal fractal exponents greater than unity in auditory-nerve spike trains
Authors: Lowen Steven B. , Teich Malvin C.
Published: October 2005

Auditory-nerve spike trains exhibit fractal behavior, and therefore traditional renewal-point-process models fail to describe them adequately. Previous measures of the fractal exponent of these spike trains are based on the Fano factor and consequently cannot exceed unity. Two estimates of the fractal exponent are considered which do not suffer from this limit: one derived from the Allan variance, which was developed by the authors, and one based on the periodogram. These measures indicate that fractal exponents do indeed exceed unity for some nerve-spike recordings from stimulated primary afferent cat auditory-nerve fibers.