bluuebunny/crossref_metadata_2025 huggingface dataset:
Recollections of acoustics at Brown University in the early fifties.
Authors: Elder S. A.
Published: October 2005

When I arrived at Brown in 1950, Bob Beyer, a young assistant professor, was already becoming well known as an acoustician. Within a year he was promoted to associate professor and took over the ‘‘References’’ section of JASA at the death of Arthur Tabor Jones. Having previously translated works in German, soon he had taught himself Russian and become known as the editor of JETP, the Russian translation journal. I took an ultrasonics course from him, about the time the milestone article on acoustic absorption by Markham, Beyer, and Lindsay came out in Reviews of Modern Physics. In those days Brown Physics was a powerhouse of expertise in acoustics, with three out of every four faculty members specializing in that field. In 1952 distinguished acousticians from around the world gathered at Brown for an ONR ultrasonics symposium. As the field of nonlinear acoustics began to evolve, Beyer, along with Lindsay, Nyborg, Westervelt, and their students, was busy exploring high amplitude effects such as anomalous absorption, acoustic streaming, and, later, scattering of sound by sound. All this took place in an ancient relic of a building called Wilson Hall, with an attic full of dusty apparatus left from a departed 19th century department chairman, and a basement full of great, mosquito-infested ultrasonic water tanks.
Nonlinear acoustic Doppler effect in a bubble flow.
Authors: Didenkulov Igor N. , Yoon Suk-Wang , Kim Eui-Jun , Sutin Alexander M.
Published: October 2005

The Doppler effect is a well-known and widely used phenomenon. In acoustics it is usually considered for linear response from a moving target. No attention was given previously to specific phenomena of nonlinear sound scattering by moving nonlinear scatterers. In the present paper a nonlinear analog of the Doppler effect is studied theoretically and experimentally. The most prominent nonlinear acoustic scatterer is a bubble. A theoretical analysis of frequency shift under nonlinear scattering of two, in a general case, acoustic waves by a moving nonlinear scatterer with generation of harmonics and combination (i.e., the sum and the difference) frequencies is given. It is shown that the nonlinear Doppler frequency shift for the difference frequency generation depends on the geometry of primary waves and can be much larger than the linear Doppler frequency shift for the difference frequency. Experiments have been made with bubble flows in a vessel. The results are in good agreement with the theory. Feasible applications of the nonlinear Doppler effect for bubble flow velocity measurement are discussed and demonstrated experimentally. [This work was done at the Acoustic Research Lab. of Sung Kyun Kwan Univ. under support of STEPI, Republic of Korea, and supported in part by RFBR (grant 94-05-16755), Russia.]
Nonlinear acoustic method for bubble density measurements.
Authors: Sutin Alexander M. , Yoon Suk-Wang , Kim Eui-Jun , Didenkulov Igor N.
Published: October 2005

An enormously high nonlinear response of a bubble to an acoustic excitation makes nonlinear methods possible and very selective for bubble observation and sizing. Among different nonlinear acoustics methods of bubble detection there is one based on difference frequency generation under the action of two high- frequency pump waves. In this method the nonlinear scattering from a single bubble was studied. In the present paper the nonlinear incoherent scattering of two high-frequency acoustic waves with the difference frequency generation from a bubble cloud was theoretically and experimentally investigated to estimate bubble size distribu- tions. In the experiments two primary waves were produced by focused transducers. One of the primary frequencies was kept constant at 2.25 MHz; another was changed. Thus the difference frequency was varied from 30 to 320 kHz, which corresponds to the resonant bubble radii from 109 to 10 μ m. For the bubble clouds produced in a laboratory tank by electrolysis- and slit-type bubble makers, the bubble densities were well estimated with the present nonlinear acoustic method, respectively. [This work was done at the Acoustic Research Lab. of Sung Kyun Kwan Univ. under support of STEPI, Republic of Korea, and supported, in part, by RFBR (Grant 94-05-16755), Russia.]
Observer weighting of interaural differences of time in different regions of intracranial space.
Authors: Stellmack Mark A. , Dye Raymond H.
Published: October 2005

Weights that listeners placed on interaural differences of time (IDT’s) were computed for two pure tones that had different mean IDT’s. As a cue on each trial, the target (753 Hz) was presented in isolation at its mean IDT. Then, the target and distractor (553 Hz) were presented simultaneously with IDT’s selected from Gaussian distributions (σ = 50 μs). The listener indicated whether the target in the test interval appeared to have moved to the left or right of its cued position. The weights were the correlations between the IDT of each component and the listener’s left/right response. In one condition, the mean target and distractor IDT’s were of equal magnitude (0, 25, 50, 100, and 200 μs) but opposite sign. Large individual differences in weights and percent correct were observed. In a second condition, the mean target IDT was 0 μs and the mean distractor IDT was 0, 50, 100, or 200 μs. Here, target weights and percent correct generally increased for all listeners as the mean distractor IDT increased. Results are attributed to increased target weight as the difference between target and distractor IDT increased, and decreased sensitivity to changes in IDT as mean IDT increased. [Work supported by a Program Project Grant from NIDCD.]
Franssen effect as a function of carrier waveform, carrier level, and room acoustics.
Authors: Mapes-Riordan Dan , Yost William A. , Guzman Sandra J.
Published: October 2005

The Franssen effect was studied as a function of the frequency of the source and echo sounds, the difference in frequency and level between the source and echo sounds, and as a function of the amount of room reverberation. A modification of the single-interval procedure used by Hartmann and Rakerd [J. Acoust. Soc. Am. 86, 1366–1373 (1989)] was used to measure the degree to which the source and echo sounds were fused in terms of determining the location of the perceived sound. The amount of fusion was a nonmonotonic function of frequency, decreased as the frequency and level difference between the echo and source increased, and is greater for a room with more reverberation. The results will be discussed in terms of the precedence effect, listener’s prior experience, and the plausibility hypothesis. [Work supported by a Program Project Grant from NIDCD and a grant from the AFOSR.]
Phase discrimination and stimulus level in normal-hearing and hearing-impaired listeners.
Authors: Leek Marjorie R. , Patterson Roy D. , Summers Van
Published: October 2005

In a linear filterbank there is a simple trade-off between filter bandwidth and duration of the impulse response. This suggests that hearing-impaired listeners with broad auditory filters will have abnormally acute temporal sensitivity, and would be more sensitive than normal to phase manipulations in harmonic stimuli. However, repeated attempts to substantiate this prediction have largely failed. Linear models fail to account for the loss of gain associated with outer haircell damage in the impaired cochlea. In preparation for modeling phase discrimination with an active cochlea model, phase discrimination thresholds were measured at a number of stimulus levels for normal-hearing and hearing-impaired listeners in a standard/2AFC experiment. Stimuli were 21-component harmonic complexes with a fundamental frequency of 125 Hz. The standard had all components in cosine phase. Test stimuli had odd-numbered harmonics in cosine phase and even-numbered harmonics shifted a fixed number of degrees as determined by an adaptive track. For both groups of listeners, phase discrimination deteriorated as stimulus level decreased below 30–40 dB SL. The importance of sensation level to these results and their lack of dependence on frequency resolution will be discussed in terms of linear and level-dependent models of cochlear function. [Work supported by NIH.]
Differences in modeling adaptation for the hard of hearing versus normal listeners.
Authors: Dou Hong-Wei , Mackay Ian , Korman Maureen , Huber Teri , Martin Marianne , Bose Heather , Hall Stephanie , Homan Dana , Walls Gena , Hawes Dana , Sandman David , Weiler Ernest M.
Published: October 2005

Data gathered by Korman and Weiler [MA thesis, Univ. of Cincinnati, 1986] and Janson et al. [Br. J. Audiol. 30, 35–42 (1996)] have shown the loudness function for loudness adaptation gathered by the ipsilateral comparison procedure (ICP) differs for normal hearing listeners and those with high-frequency cochlear loss. This paper investigates the modeling assumptions for loudness growth in the two kinds of listeners. Surprisingly, the loudness growth within a given frequency is not clearly different in kind, although the two groups start with different values in most test conditions. However, there does appear to be a difference across frequencies which may be a reflection of the spread of excitation on the basilar membrane. Expected differences in activation for normal listeners and those with a high-frequency loss will be discussed.
The phase gradient method applied to the plate: Analysis of the partial derivatives with respect to the phase velocities.
Authors: Lenoir O. , Conoir J. M. , Izbicki J. L.
Published: October 2005

The phase gradient method is a convenient tool in order to analyze the frequential and angular resonances of an immersed elastic plate [J. Acoust. Soc. Am. 94, 330–343 (1993)]. It consists in the study of the derivative of the phase of the reflection coefficient with respect to the frequency x—the obtaining of the resonance frequency x* and the resonance width Γ* is then straightforward—or with respect to the angular parameter y (which is the sine of the incidence angle). It is shown that the derivatives with respect to the different phase velocities involved in the scattering problem also permit the isolation of the resonances. The derivatives with respect to the longitudinal (cL) and shear (cT) velocities of the plate and to the longitudinal velocity of the fluid (cF) are studied. The plot of the previous derivatives, versus the frequency, exhibits Breit–Wigner peaks. Their half-widths are equal to Γ* and the coefficients ΓL, ΓT, ΓF related to their amplitude are introduced. The physical meaning of the previous amplitude coefficient is given. Then a resonant energy conservation law is shown: Γ*+ΓF=ΓL+ΓT.
Waves and vibrations in multilayer poroelastic plates.
Authors: Dökmeci M. Cengiz , Altay G. Askar
Published: October 2005

In view of a recent extensive review concerning wave propagation in porous media [M. Y. Corapcioğlu, in Transport Processes in Porous Media (Kluwer, Dordrecht, 1991), pp. 373–469], this paper presents a theory for the dynamic response of a multilayer plate within the frame of Biot′s theory of elasticity and consolidation for a porous anisotropic solid [M. A. Biot, J. Appl. Phys. 26, 182–185 (1955)]. The multilayer plate may comprise any number of bonded layers, each with a distinct but uniform thickness and anisotropic elastic properties. A differential variational principle [G. A. Altay and M. C. Dökmeci, J. Acoust. Soc. Am. 95, 3007 (A) (1994)] for Biot’s theory together with Mindlin’s plate kinematics for each layer is used to derive the two-dimensional approximate equations of multilayer plate in invariant differential and variational forms. All the continuity conditions between the interfaces of layers are taken into account. The governing equations are capable of predicting the extensional, flexural, torsional, and coupled vibrations of multilayer poroelastic plates. Special cases involving the geometry, material, and motions of multilayer plates are studied. The results contain some of earlier ones as special cases. [Work supported in part by TÜBA-TÜBİTAK.]
Mode shape and eigenfrequency spectra of elastic plates in the vicinity of the thickness resonance frequency.
Authors: Grinchenko Victor T.
Published: October 2005

A number of experimental investigations have been performed to study vibration characteristics of elastic plates in a high-frequency region. Up to this time the empirical data have no satisfactory explanation in terms of Lamb wave coupling. The theoretical analysis of the coupling effects presented in the article is based on the exact solution of the free-axis-symmetric vibration problem for a circular plate. Consideration of a special case of zero Poisson’s ratio allows one to distinguish and investigate three independent kinds of eigenmodes. Two of them are initiated by simply propagated longitudinal waves. The waves with complex wave numbers (evanescent standing waves) provide a rise to a third type of eigenform. Eigenfrequencies of these last modes are very close to the thickness resonance frequency and they increase as radius of a plate increases. The data for nonzero Poisson’s ratios demonstrate an influence of coupling on a structure of eigenfrequency spectra and mode shape. An investigation of radius variation effects gives a good indication of the feasibility of the coupling effect control. The values of the plate radius with the moderate mode shape disturbances are determined.
Investigation of wave processes in a Timoshenko thin-walled beam of open section caused by the shock subjection of an elastic sphere upon its surface.
Authors: Rossikhin Yuriy A.
Published: October 2005

The problem on the normal impact of an elastic sphere upon an elastic Timoshenko beam of thin-walled monosymmetrical open section is considered. The process of impact is accompanied by the dynamic flexure and torsion of the beam, resulting in the propagation of plane flexural, shear, and torsional waves of strong discontinuity along the beam axis. Behind the wavefronts the solution is constructed in terms of one-term ray expansions. During the impact the sphere moves under the action of the contact force which is determined due to the Hertz’s theory, but the contact region moves under the action of the contact force, and the bending-torsional moment and transverse forces, which are subjected to the lateral surfaces of the contact region and are determined using one-term ray expansions. The joint consideration of the equations of sphere and the contact region motion leads to the Abel equation of second kind in the rate of change of the value of the sphere and beam drawing together. The solution to the Abel equation written in the form of a series in terms of this value allows one to determine all characteristics of the sphere and beam shock interaction.
Wave-number-based assessment of the doubly asymptotic approximation.
Authors: Ginsberg Jerry H. , Wu Kuangchung
Published: October 2005

The most widely implemented technique for modeling fluid–structure interaction effects associated with shock response is the doubly asymptotic approximation (DAA), which has been developed in a variety of versions. Because of a lack of analytical solutions for realistic geometries, prior validation efforts have not provided definitive guidelines regarding the accuracy of the method. The present work uses Nicholas–Vuillierme’s derivation [Numerical Techniques in Acoustic Radiation, edited by R. J. Bernhard and R. F. Keltie (American Society of Mechanical Engineers, New York, 1989), Vol. 6, pp. 7–13] of the frequency-domain version of DAA as the basis for examining the accuracy and limitations of DAA for a slender hemi-capped cylindrical shell. The development computes the wet surface impedance matrix relating surface pressure and velocity variables over a broad frequency band according to two DAA versions and the surface variational principle. The alternative wet surface impedances are used to predict the frequency-domain structural response of the shell to a point force, after which alternative time-domain responses are obtained from the FFT algorithm. Results for wave-number amplitudes (azimuthal and meridional) are reported for moderate and large aspect ratios. An overview indicates that a higher-order DAA version occasionally works extremely well, but that there is no consistent high/low trend as a function of wave number. [Work supported by the Office of Naval Research, Code 1222.]
Precise formulation of the vibroacoustic effects of an added constrained damping layer on a plane structure.
Authors: Nicolas Jean , Atalla Noureddine , Foin Olivier , Mercier Bertrand
Published: October 2005

The model proposed here describes the SAV behavior of a sandwich plate (elastic–visoelastic–elastic) and uses the following hypothetisis, inspired by the discrete layer theory: The viscoelastic layer takes into account bending, shear, and traction compression; normal strain and torsional motion are neglected; using the continuity of the displacement at the visoelastic layer interfaces, the displacement field of the viscoelastic layer is written as a function of the elastic layer displacement field. A variational method is used to find the displacement equations. The radiation impedance is calculated via a formulation recently proposed by Atalla and Nicolas [J. Acoust. Soc. Am. (1994)]. This formulation allows one to calculate, for a large frequency range, the quadratic velocity, the radiation efficiency, and the radiated power. Emphasis is then put on precise experimental validation. A fully instrumented setup using a laser vibrometer for probing the displacement field has been developed. The basic plate is made either from aluminum or from resin epoxy. Using technical data furnished by the manufacturers, the comparison between theory and experience is extremely good in the case of aluminum. Discrepancies are bigger for the resin epoxy and this aspect will be discussed. Partial covering, which is also of great practical interest, will also be presented for both theoretical and experimental aspects.
Acousto-optic phase modulation of a laser Doppler vibrometer signal resulting from the radiated pressure produced by a submerged cylindrical shell: Numerical predictions and experimental results.
Authors: Simpson Harry J. , Vignola Joseph , Marcus Martin H. , Houston Brian H.
Published: October 2005

It has been proposed that large stand-off laser Doppler vibrometer (LDV) measurements have significant errors resulting from index of refraction modulation due to the acoustic pressure distribution along the laser light paths between the structure and the probe [Y. H. Berthelot et al., J. Acoust. Soc. Am. 97, 3347(A) (1995)]. A high fidelity numerical model has been used to predict the pressure distribution and shell motions for a submerged finite ribbed cylinder under point excitation. Generally speaking, these predictions show low levels of contamination even for large stand-off probe distances. In addition, an experimental study has been conducted at NRL using a newly integrated three-axis vibrometer and near-field pressure probe where shell motions and near-field pressure distributions were measured for the case of a submerged ribbed cylinder under point excitation. The experiments and the associated numerical modeling both indicate low levels of acousto-optic contamination of the shell velocity signals. These findings contrast previously reported predictions of the level of acoustically induced error for large stand-off in-water LDV designs. [Work supported by ONR.]
Fractal sound radiation by layered elastic structures.
Authors: Lyamshev Leonid M.
Published: October 2005

A general method of calculation of sound radiation by layered elastic structures is developed. The reciprocity theorem formulated by the author in 1958 is used. It is shown that plane structure sound radiations are determined by external acting forces and the structure transmission coefficient. The method is very convenient for the analysis and calculation since the external force characteristics are given and the transmission coefficient is a known function of impedances of layers. Several particular problems are considered. Sound radiation by a thin plate or a thick three-layered structure are considered when concentrated or fractal distributed statistical external forces act. The method for moving media in layers is generalized. Sound radiation by curved inhomogeneous layered structures is discussed. The plane structure formula, Green’s theorem, and the Kirchhoff approximation are used in last cases. Sound radiation fractal characteristics are discussed.
Musical communication and theories of the stimulus.
Authors: Palmer Caroline
Published: October 2005

Is the stimulus for music perception an abstract form of a musical piece, or a particular performance of it? As with language, music reflects a communication of structure among its users (composers, performers, and listeners), which suggests the existence of some shared musical knowledge. Music performance may be an indispensable source of evidence for theories of that shared knowledge, because the particular expression given in each performance guides our musical understanding. Different sources of knowledge in music performance that contribute to a theory of the stimulus for perception will be described. Evidence from both expressive nuances of performance and from production errors (unintended mistakes) converge on the same knowledge sources. These performance findings have correlates in both music perception and in other production domains, such as speech. [Work supported by NIMH and NSF.]
Music and speech in a neuropsychological perspective.
Authors: Peretz Isabelle
Published: October 2005

Neuropsychology — defined as the study of the relations between brain organization and mental functioning — has concerned itself from its earliest days with the processing of speech and music. The first steps were taken in the speech domain, via the observation of selective speech impairments following damage to specific areas of the brain (Broca, in Von Bonin, Some Papers on the Cerebral Cortex; Wernicke, in Brain Function 3, 1–16). These initial findings swiftly prompted the exploration of music disorders (Bouillaud, Bull. Acad. Med. 30, 752–768). Such observations are labeled aphasia and amusia, respectively, and reflect a long-standing concern to describe the selectivity of the disorders observed. This issue of specificity is even more prevailing/acute in contemporary neuropsychology, with the advances made in brain imaging and in experimental psychology. Current knowledge will be summarized and organized along two main questions: (1) Is music, like speech, subserved by neutral circuitries devoted to its processing? (2) What are the boundaries of neuropsychological separability between music and speech?
Reproducibility of low-frequency shallow-water acoustic experimental data.
Authors: Evans Richard B. , Carey W. M.
Published: October 2005

Transmission loss measurements were conducted in September 1993 on the continental shelf off New Jersey. Low-frequency continous-wave data were recorded on a vertical line receiving array in approximately 73 m of water. The geometry of these measurements replicates the geometry of experimental measurements conducted during October 1988 at the same site and under similar downward refracting conditions. The sets of frequencies transmitted during the two experiments were different, but covered the region less than 1 kHz. Acoustic surveys and geophysical data obtained in 1988 provided detailed characterizations of the seabed. The bottom characterization is assumed to be time invariant, except for the contribution of the pore fluid to the uppermost layers of the sediment. Consequently, the characterization of the seabed should be valid when the bottom waters are similar. The coincidence of the two sets of experimental data and a valid geoacoustic model provide the opportunity to test the reproducibility of these results. The bottom characterizations based on two sets of acoustic data are compared with expectations based on profiles derived from geophysical data.
Statistical analysis of broadband propagation in shallow water.
Authors: Badiey Mohsen , Shaw Simon A. , Bongiovanni Kevin P. , Honsinger Thomas C. , Zagar Joe R.
Published: October 2005

One of the most important issues facing ocean acoustic experimentalists when attempting to perform calibrated experiments is distinguishing measurement errors from environmental variabilities. These errors include accuracy of monitoring hydrophones, ship positioning (hanging sources), and, for a broadband source in particular, spectral level and phase variations of the source. Statistical analysis is used to investigate the repeatability of source and receiver signatures collected from a series of broadband experiments performed in very shallow water at the Atlantic Generating Station (AGS) site. Classification of the factors inducing signal variation, which may arise from surface and bottom roughness and time-varying volume inhomogeneities, in addition to source errors, is made for several experimental configurations. It is shown that the coherence of the received signals is directly related to the environmental effects on the acoustic waves and the shot-to-shot correlation decreases with increasing range.
A study of the influence of an off-shore rise on low-frequency modal propagation with Arctic surface loss.
Authors: Lawrence Thomas N. , Trappe Wade , Bedford Nancy R.
Published: October 2005

Simple up-slope propagation of underwater acoustic energy can usually be modeled by an adiabatic normal mode approximation, provided the slope is not too severe. Bottom interacting paths in such an environment are usually sufficiently attenuated to make consideration of mode coupling unnecessary. An environment further complicated by an off-shore rise can cause additional acoustic energy to be introduced into lower-order modes due to bottom interaction. These low-order modes will then propagate in deep water until encountering the continental shelf. Experimental results from the Arctic Ocean between 25 and 45 Hz suggest such propagation conditions. These results, and their interpretation in the context of a coupled mode study, will be presented. Environmental parameters and source depth will be varied to explore under what conditions mode coupling can be ignored when considering detection and localization problems. Arctic surface loss will be applied to the modeling results to show how mode varying attenuation will affect those results. The coupled mode model (COUPLE) [R. B. Evans, J. Acoust. Soc. Am. 74, 188–195 (1983)], is used as the vehicle for this study. [This work is sponsored by SPAWAR PMW 182-2.]
Improved narrow-band and broadband normal-mode algorithms for fluid ocean environments.
Authors: Westwood Evan K.
Published: October 2005

Improvements have been achieved in the speed, robustness, and versatility of a recently developed normal-mode algorithm for fluid ocean environments [S. J. Levinson et al., J. Acoust. Soc. Am. 97, 1576–1585 (1995)]. The possibility of missing modes has been eliminated by computing both the total phase of the oscillatory mode function versus depth and the number of zeros of the function. The root-finding algorithm computes both an error function and its derivative, which allows cubic interpolation to be used to obtain eigenvalue guesses when a root is bracketed. The efficiency of the root-finder is characterized by the fact that the error function typically must be computed less than 3-1/2 times per mode. An automated broadband capability has also been implemented. Analytic first and second derivatives are used to interpolate the eigenvalues in frequency as a fifth-order polynomial. For broadband computations where inclusion of the continuum is desired, a false bottom may be automatically inserted. Its thickness is specified in terms of acoustic wavelengths in the medium and varies with the frequency, thus saving the computation of a significant number of modes. [Work supported by ONR 321OA.]
Acoustic propagation through a low Mach number, stratified flow.
Authors: Elisseeff Pierre , Schmidt Henrik
Published: October 2005

Propagation of sound in an oceanic waveguide in the presence of a low Mach number, stratified flow is investigated. Equations for the wavenumber integration (WI) and normal mode (NM) approaches are simultaneously derived in a single formulation. When hydrodynamic shear stress and acoustic azimuthal coupling are negligible, the effect of current can be accounted for by a simple modification of existing WI and NM codes. A current layer is then shown to act as a wave-number filter which, in some cases, cannot be modeled using an equivalent sound-speed profile. Broadband numerical simulations show very good agreement between independently modified versions of OASES and KRAKEN. Applications to tomography are eventually discussed. The acoustic field for smooth current profiles can be derived as a function of the medium-at-rest mode set, making a broadband inversion possible. [Work supported by ONR.]
Nonlinear wide-angle paraxial propagation in shallow-water channels.
Authors: Kulkarni Rahul S. , Siegmann William L. , Collins Michael D.
Published: October 2005

A model that describes wide-angle paraxial propagation of acoustic pulses in shallow water has been developed. This time-domain, range-marching model incorporates weak nonlinear effects and depth variability in both ambient density and sound speed, with extensions to include dissipative effects. The derivation is based on an iterative approach, in which the wide-angle approximation is obtained by using a narrow-angle equation to approximate the second range derivative in the two-way nonlinear wave equation. Scaling arguments are used to obtain a more tractable simplification of the equation. Higher-order approximations can be derived by continuing the iterative procedure. The wide-angle equation is solved numerically by splitting it into components representing distinct physical processes and employing a predictor-corrector strategy. A high-order upwind flux-correction method is used to handle the nonlinear component, in order to eliminate spurious artifacts that otherwise degrade the solution. Numerical results are presented for different types of sources in several horizontally stratified environments. Effects of nonlinearities on wide-angle propagation and differences between narrow- and wide-angle nonlinear propagation will be discussed. [Work supported by ONR.]
A hot topic in musical acoustics: Phase coherent representation of radiated sound fields.
Authors: Hansen Uwe J.
Published: October 2005

A technique used to study normal-mode vibrations in musical instruments is modal analysis. This experimental method analyzes a series of transfer functions which relate the frequency spectra of a number of impact points to the spectrum of a fixed response point, and subsequently presents the motion of the structure at the various normal-mode frequencies in computer animation. This approach is extended to represent a radiated sound field by using a fixed excitation point on the musical instrument as the reference signal and monitoring the sound field with a microphone at a number of predetermined points. This makes it possible to relate the phase of the sound field to the phase of the vibrating structure responsible for generating that field. Animated illustrations will be shown for the air column in a wind instrument and for the sound field of a concert grand piano.
Equipment representations as time-domain fuzzy structures.
Authors: Cherukuri Aravind , Barbone Paul E.
Published: October 2005

The presence of complex subsystems can dramatically affect the dynamics of the main structure to which they are attached. Exactly modeling these subsystems, however, is often impossible. Here, replacing the substructure (say a piece of equipment) by an equivalent set of forces which react back on the main structure is proposed. These forces are given as time convolutions of the displacements at the equipment attachment points. The convolution integral, which represents a time-domain DtN (Dirichlet-to-Neumann) map, is approximated in the high modal density limit with determined error bounds. Local in time approximations to the convolution integral are obtained using Padé approximants. These yield a family of equipment representations. The simplest requires two measured equipment properties, though more information can lead to greater accuracy. Our approximate DtNs are validated numerically in finite-element simulations. [Work supported by ONR.]
Experimental identification of fuzzy structure parameters.
Authors: Nagem Raymond J. , Stokes Ann W. , Pierce Allan D.
Published: October 2005

Researchers have recently been developing a theory to model structures in which a primary or ‘‘master’’ structure with precisely known parameters is coupled to ‘‘fuzzy’’ substructures with parameters known only in a statistical sense. The goal of the fuzzy theory is to model complex structures with as few parameters as possible. The research presented here is an experimental investigation of the effectiveness of fuzzy parameter choices in modeling the drive-point impedance of a beam with a number of simple oscillators attached along its length. The fuzzy model makes use of ‘‘most likely’’ distributions of mass per unit resonance frequency, given limited knowledge about the attached oscillators. The oscillators are interchanged in order to achieve various realizations of mass per unit natural frequency. The magnitude and phase of the measured drive point impedance are compared to that predicted by fuzzy theory models. The use of the moments of the mass per unit natural frequency distribution as the primary descriptors of the effect of the fuzzy substructures is examined. Bounds on the differences between predicted and measured drive point impedances are established. The use of these bounds in applications such as high-performance, robust vibration control is discussed.
Vibration response statistics in regular and irregular plates.
Authors: Hartemink Christopher A. , DeJong Richard G.
Published: October 2005

Statistical measures of the vibration response of flat plates in both the frequency and spatial domains are presented. Analytical, numerical, and experimental results are presented for rectangular and irregularly shaped plates. The results are consistent with the assumption that the modal response of a rectangular plate is sinusoidal, while the modal response of an irregularly shaped plate is Gaussian. The statistical measures of a plate vibration response can be used to evaluate the system modal overlap factor, the ratio of the modal damping bandwidth to the modal frequency spacing.
Development of a mid-frequency definition and appropriate analysis techniques.
Authors: Huff John E. , Rabbiolo Guglielmo , Bernhard Robert J. , Milner Fabio A.
Published: October 2005

From experimental data collected on ensembles and from analytical verification studies of structural acoustic systems, it is apparent that there is a mid-frequency range where dominant structural acoustic responses cannot be sufficiently described deterministically or statistically. The focus of this presentation is to describe work to derive a general and rigorous definition for the frequency limits of the mid-frequency range. The statistical behavior of system response in this range is described through the analysis of the analytical expressions for the displacement of Bernoulli–Euler beams. Additionally, work to develop a numerical analysis technique which can be implemented in a finite element formulation is discussed and the possible connections between it and current techniques for energy flow analysis in the high-frequency range are made.
Comparisons of room acoustics measurement systems.
Authors: Bradley J. S.
Published: October 2005

This paper gives a summary of the results of an international room acoustics measurement system round robin. Twenty-three different measurement systems were compared by measuring three settings of the same digital reverberator that was shipped to each measurement group. This was equivalent to testing three standard rooms, but the tests did not include variations due to different types and placements of transducers. The various measurements were made over a one year period and the reverberator and measurements were shown to be stable and very reproducible over this period. The means of the closely clustering results were used to represent the best estimate of the ‘‘correct’’ answers. The standard deviations of the closely clustering results were used to evaluate the divergence of the measurements from the central trend. Approximately 2/3 of the results were within two of these standard deviations from the central trend. Two specific problems were identified and solutions recommended. While most results were in close agreement, a number of results differed significantly from the central trend and demonstrated the importance of validating new room acoustics measurement systems.
Automated architectural acoustical modeling with the SeDReS system.
Authors: Siebein Gary W. , Spolan Mitchel E. , Herr Christopher
Published: October 2005

A computer-controlled architectural modeling system was developed to allow the enclosure and materials of a room to be rapidly and precisely varied for acoustical testing using ultrasonic sparks and miniature microphones at various scales (depending upon the size of the model room to be tested). A system of stepper motors moves segmented wall, ceiling, and floor panels of a large, flexible enclosure. The walls, ceiling, and floor can be moved to configure a wide variety of rooms from a small lecture room to a large arena. The locations and angles of the enclosing surfaces of the room for multiple design motifs can be stored in the memory of the computer. One can then push several keystrokes to reconfigure the room and proceed with acoustical testing and simulation using the acoustical research instrumentation for architectural spaces (ARIAS) system. Impulse responses, acoustical measurements, and aural simulations from alternative designs can be compared at the earliest stages of the design process when one is considering basic choices of finish materials, room shape, and wall angles. [Work supported by NSF.]
Analysis and synthesis of room reverberation in the time and frequency domains—Application to the restoration of room impulse responses corrupted by measurement noise.
Authors: Jot Jean-Marc , Vandernoot Guillaume , Warusfel Olivier
Published: October 2005

This paper reviews a statistical time-frequency model of the late diffuse reverberation in rooms. In this model, the later part of a room impulse response is described by a ‘‘time-frequency envelope,’’ defined as the ensemble average of the time-frequency energy distribution in the late decay. The time-frequency envelope is independent of the source and receiver locations and is characterized by two functions of frequency: the reverberation time and a power spectral density called the ‘‘initial spectrum,’’ which corresponds to the product of the diffuse-field transfer functions of the source and the receiver. An analysis method is described for deriving these parameters from a measured impulse response, yielding an accurate estimate of the reverberation time with arbitrary resolution in the frequency domain. The time-frequency envelope defines a time-dependent filter which transforms a sampled stationary Gaussian white noise into a synthetic model of the late reverberation decay. Substituting this synthetic reverberation decay to the part of an impulse response that is corrupted by measured noise, yields a restored impulse response allowing faithful auralization by convolution with anechoic source signals. The models and the methods described are illustrated on impulse responses measured in a concert hall.
Analysis of subjective acoustic measures and speech intelligibility in Portuguese churches.
Authors: Carvalho António P. O. , Morgado António , Henrique Luís
Published: October 2005

This study reports on subjective acoustical field measurements made in a survey of 36 Catholic churches in Portugal built in the last 14 centuries. The same group of college students were asked to judge the quality of speech and music at all the churches. Two sets of listeners in each church evaluated live music performance (cello and oboe) at two similar locations in each of the rooms using a seven-point semantic differential rating scale. An acoustical evaluation sheet was used to measure listeners overall impression of room acoustics qualities, and each of the factors that can contribute to that perception as loudness, reverberance, intimacy, envelopment, balance, clarity, echoes, and background noise. Speech intelligibility tests were also given to the same group in each church. One-hundred-word lists were used in live speech tests using a theater college student as speaker. The results are graphed and analyzed by comparisons. Variations of subjective and speech intelligibility qualities were identified among the different churches and within each of the churches as well. For instance, church mean values for the intelligibility scores range from 56% to 96% correct words and the variability within each room extent from 6% to 49%. The subjective qualities that contributed to overall acoustical impression were also identified. [Work supported by CEDEC, ESMAE and UP-Portugal.]
A proposed acoustical renovation for The Great Hall at The Cooper Union.
Authors: Miller Gregory A. , Raichel Daniel
Published: October 2005

The Great Hall is an 1100-seat auditorium with historical landmark status built in 1859. It has been the site of many historic speeches by figures ranging from President Abraham Lincoln to Sioux Chief Red Cloud. Throughout its history, however, The Great Hall has been described as a less than adequate acoustical environment, suffering from low speech intelligibility and excessive reverberance. Building upon the previous work of Raichel and Dragan who modeled the auditorium in its current configuration, the authors undertook a study of the feasibility of renovating and improving The Great Hall while maintaining the architectonic integrity of the space, as necessitated by historical landmark protection. It was found that a simple replastering of the walls and ceiling of the auditorium will lower the reverberation time at 250 Hz from over 3 s to under 1 s and should significantly reduce the effect of late (after 50 ms) reflections. The new plaster will have lower density and higher porosity than the old plaster, significantly improving its sound-absorbing characteristics. The proposed renovations are currently under consideration for implementation.
Recognition of the utterances of terrestrial wildlife: A new approach.
Authors: Larkin Ronald P. , Margoliash Daniel , Kogan Joseph A. , Pater Larry L.
Published: October 2005

Finding and censusing birds and other animals via listening can pose problems because of inaccessibility of habitats, rarity or shyness of animals, or subjectivity of observers. A new collaborative project seeks to evaluate algorithms adapted from human speech recognition to establish a basis for automating the identification of animal vocalizations and recording their occurrence. The algorithms include dynamic time warping and hybrid hidden Markov models incorporating features of artificial neural networks. Probably no single method will work for all species. More than one method maybe useful together, in multiple stages. A database of high-quality, annotated digital field recordings is being collected to supply training and test data on known species and, when possible, known individuals. Both low-noise and realistic ambient noise situations are important. Field data are supplemented with recordings from laboratory settings. Red-cockaded woodpecker, other vocal yet threatened species, and species related to them, such as other Picoides woodpeckers, are being studied. Preliminary results are presented. [Research supported by USACERL.]
Intraspecific variation in primate vocalizations.
Authors: Norris Jeffrey C.
Published: October 2005

Intraspecific variability in primate vocalizations exists at several levels—within organizational levels of a species, as well as differingly across acoustic variables. This paper reviews signal variability between subspecies, groups and populations, individuals, and within a single individual’s vocalizations. The problem of signal variability is best seen when humans describe a species’ repertoire. The literature is replete with examples where humans underestimate the amount of variability recognized by the animals; humans typically are lumpers, where playback experiments show that the animals recognize differences that are imperceptible to us. The perceptual cues used by five primate species will have been described. Sensitivity to variability is not uniform between acoustic variables. Variability in signal production has been described for an additional 14 species. Details of interindividual and intraindividual variability of wedge-capped capuchin alarm calls is described. Where early taxonomies of this species’ vocalizations recognized two alarm calls, subsequent research by the author described 15 variants of one call, at least three of which were recognized by the monkeys to refer to different objects. The importance of the vocalization’s function will be stressed, recognizing that motivational calls may have greater intrinsic variability than those referring to specific external objects.
Geographic variation and cultural evolution in songs of humpback whales (Megaptera novaeangliae) in the eastern North Pacific.
Authors: Cerchio Salvatore , Jacobsen Jeff
Published: October 2005

Songs of humpback whales off Hawaii and Mexico were examined to determine whether they changed similarly in both areas during a breeding season. Songs of 24 individuals were recorded off Kauai, Hawaii and Isla Socorro, Mexico during winter and spring of 1991. Forty-seven acoustic variables describing all levels of song structure were measured for each singer. Similar variables were grouped together into six categories. Mean values for each singer were compared among regions and time periods using two-factor ANOVAs. All but three variables changed between winter and spring in at least one area. Groups of similar variables displayed similar trends. Quantitative characteristics of song elements often changed during the breeding season by the same amount in each area, with little variation within and among individuals. Structures of song patterns often changed differently in each area. Results indicated cultural transmission may have occurred during the season. Alternatively, whales may be predisposed to gradually change features of song independent of cultural influences. Given the low level of variability exhibited by many variables, the latter seems more likely; therefore, temporal change, like song structure, may be governed by a discrete set of rules. Further research on a longer time scale is needed.