bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations of insonified contrast agents in vitro and in vivo
Authors: Dayton Paul , Morgan Karen , Allietta Margaretta , Ferrara Kathy , Klibanov Alexander , Brandenburger Gary
Published: July 2002

Ultrasound contrast agents, which may include a gas core and lipid or albumin shell, play an increasingly important role in medical imaging. However, a complex set of phenomena have limited quantitative evalua- tion of tissue perfusion based on echoes from these microbubbles. With the use of optical microscopy, mechanisms of microbubble destruction during insonation are evaluated, as well as the effects of ultrasonic radiation force. Depending on conditions such as acoustic intensity and dissolved gas concentration in the media, several mechanisms can change the microbubble and promote its destruction during insonation. Slow gas diffusion from the bubble is observed with low-intensity transmission, but with several pulses at a higher intensity, the albumin shell may weaken sufficiently to release the gas core. It is demonstrated that the primary acoustic radiation force has a significant effect on microbubbles when the ultrasound is transmitted with a low acoustic pressure and high pulse repetition frequency. Deflection of the contrast agent streamline to the wall of a small vessel is shown both in vitro and in vivo. Such manipulation of the contrast agents may be desired in drug delivery applications, as it provides a method of concentrating bubbles in a specific area.
The use of tuned absorbers in minimizing sound power from vibrating structures
Authors: Koopman Gary H. , Constans Eric , Belegundu Ashok
Published: July 2002

This paper presents a methodology for designing quiet shell structures through the use of multiple tuned resonators. Thin shell structures are targeted for noise reduction because of their ubiquity in industry. They are used to cover and protect noisy devices, such as gearboxes and electrical transformers, and are also used to keep dirt and other contaminants away from moving parts, as in the case of automotive valve covers. The method combines a finite element method vibration prediction code, a boundary element method sound power prediction code, and a combined stochastic/gradient-based optimization algorithm for optimizing the locations and parameters (stiffness, mass, and damping) of the tuned absorbers. A design example has been optimized: a thin shell covering a motor/gearbox/brake combination. It is demonstrated that the addition of a small amount of weight (130 g, or 1.6% of the weight of the shell) can produce substantial reductions in sound power (13 dB in the targeted a 1/3-octave band centered at 125 Hz).
Temporal structuring of acoustic segments in speech communication
Authors: Potapova Rodmonga K.
Published: July 2002

The following problems were studied on the domain of the temporal structuring of speech utterance: the determination of algorithms of synthesis of the rhythmic patterns of the utterance, the problem which is often referred to as preprogramming of the temporal organization of the speech signal being part of a more general problem of synthesis (generation) of prosodic patterns of the utterance; the determination of signals used in the information exchange between linguistic and neuro-physiological levels of speech analysis and synthesis; the rules determining the conversion of transformation of the rhythmic patterns of the utterance into real-time intervals between articulatory positions and movements. The character of a durational correlation which has been revealed in this experiment (with the use of the special correlation coefficient ρ and the test of the H0-hypothesis) made it possible to define three types of temporal correlation: microcorrelation (for subsound and sound levels), mesocorrelation (for syllabic level), and macrocorrelation (for the level of phrase rhythmic structures—phonetic words). The integral temporal organization of speech utterance is determined on the one hand by a lower level effect—coarticulation, and on the other hand by a higher level effect—the rhythmic patterns of a phrase.
Baby word rhythm preferences of Japanese infants
Authors: Hayashi Akiko , Yoshioka Kyoko , Mazuka Reiko
Published: July 2002

For infants acquiring English, many studies have shown that the dominant stress pattern of the language (viz., strong–weak syllable sequence) plays a critical role in perception, segmentation, and early speech production. Questionnaires to Japanese mothers revealed that many words they use in child-directed speech take the form of XsX or XsXs (X=regular mora; s=special morae). It was hypothesized that this sequence might count as a dominant rhythmic pattern for Japanese infants. Using a head-turn listening preference paradigm, 8–10-month-old Japanese infants were found to show a preference in listening to lists of pseudowords that conform to the XsX pattern when compared to another list of words with three regular morae (XXX). Four- to six-month-old infants showed no such preference. An additional experiment eliminated the possibility that the result of the first experiment was simply based on the presence or absence of special morae in the lists. The results will be discussed in relation to the increasing body of English data to examine how infants might learn to take advantage of language-specific rhythmic patterns in language development.
Effects of levodopa on finger and articulatory movements in Parkinson’s disease
Authors: Gentil Michele , Pollak Pierre
Published: July 2002

Efficacy of levodopa therapy on finger and articulatory movements in Parkinson’s disease was studied. The production of isometric force was estimated in both conditions, without and with levodopa in 14 patients with a diagnosis of idiopathic Parkinson’s disease (the mean duration of symptoms was 9 years). Forces generated by the upper and lower lips, tongue, and right and left forefingers in the presence of visual feedback were measured by means of force transducers. Moreover motor disability of patients was assessed in each condition. Fourteen control subjects also participated in this study. The beneficial effect of levodopa on finger motor disorders of patients was observed as indicated by better motor scores and improved production of finger forces. In contrast, the production of articulatory forces of patients was either not improved or aggravated by levodopa therapy. These results suggest that cerebral nondopaminergic lesions are probably responsible for the impairments of parkinsonian speech.
Source modeling of severely pathological voices
Authors: Gerratt Bruce R. , Kreiman Jody , Antonanzas-Barroso Norma , Gabelman Brian , Alwan Abeer
Published: July 2002

Previous studies using a simplified LF source model [Qi and Bi, J. Acoust. Soc. Am. 96, 1182–1185 (1994)] to describe pathological voice sources indicated that model fit to the return phase is particularly poor. To examine the perceptual importance of differences in how the return phase is modeled, various functions were fitted to the source waveforms that had been obtained by inverse filtering. Voices were then resynthesized using these different source functions, and the resulting signals were compared perceptually to the original natural voice and to versions synthesized with LF modeled sources. The perceptual importance of changes in closing phase modeling for these severely pathological voices will be discussed, as will the range of functions necessary to obtain perceptually satisfactory synthesis of severely deviant voice sources. [Research supported by NIH.]
Palate shape effects on characteristic vowel tongue postures
Authors: Tiede Mark K.
Published: July 2002

In this work MRI vocal tract data obtained during sustained vowel production is used to investigate the interaction between individual speaker differences in hard palate shape and the compensatory adjustments to tongue posture needed to tune language-specific vowel formant resonances. PCA techniques developed in previous work [Tiede and Yehia, J. Acoust. Soc. Am. 100, 2658(A) (1996)] were used to characterize three-dimensional tongue and palate shapes for vowel inventories of five Japanese and five American English subjects. Parametrized shapes for individual speakers were compared to a normalized mean tract shape pooled across subjects for each language. Preliminary results show that the axis of tongue body displacement is associated with oral cavity depth (OCD, measured from the teeth to the rear pharyngeal wall): Shorter OCD subjects showed greater vertical /a/ versus /i/ differences, and longer OCD subjects used more of a horizontal component. Systematic effects of palate vault shape on tongue constriction location have also been observed. These results are consistent with the speaker-specific articulatory (‘‘A’’ space) adaptations suggested in previous work [Honda et al., Proc. ICSLP96, 784–787 (1996)].
A perceptual and acoustic study of the imitated voice
Authors: Sullivan Kirk P. H. , Schlichting Frank
Published: July 2002

The belief that an individual can discriminate between different voices from memory is central to the concept of the voice line-up, the aural analogue of the police identification parade, and its application in the legal sphere. This paper examines the impact professional and amateur imitations have on the accuracy of the technique and whether differences in impact can be explained by an examination of vowel space, timing, and F0 values. Three groups of experimental participants heard a series of different voice line-ups. They were instructed to indicate which voice of each series was the voice they had been asked to identify. Not all of the series contained the voice to be identified. Group one was presented line-ups containing a high-quality professional imitation. This resulted in a significant degree of confusion between the voice to be identified and the imitation. Group two was presented the same series of line-ups but the professional imitation was exchanged for an amateur one. Group three was presented the same line-ups, but containing another amateur imitation. The amateur imitators failed to cause confusion with the voice they were imitating, yet succeeded, to different degrees, in disguising their natural voices such that their own identity was protected.
Modeling in-vehicle engine noise
Authors: Deblauwe Filip , Van de Ponseele Patrick , Lowet Geert
Published: July 2002

Transfer path analysis is accepted as a tool to model or troubleshoot the lower engine orders for in-vehicle noise. The contribution of each force input that is coherent with the engine can be evaluated both for amplitude as well as phase. This allows ranking the individual paths and allows identifying paths that interact (cancel effects). The ability to listen to these contributions, also called partial pressures, is needed for the sound quality evaluation of engine noise, and the next logical step in transfer path analysis. Steady-state applications of time domain transfer path analysis have been reported, but primarily the study of pseudostationary sounds such as engine run-ups was desired. In this document, different methods will be discussed that could enable this type of work. The new developed synthesized order substitution method is presented. This method enables an engine sound engineer to listen to the sound due to a single or a set of noise transfer paths, for a reasonable computation effort.
Acoustic-wave detection by optical beam deflection
Authors: Caron James N. , Mehl James B. , Steiner Karl V.
Published: July 2002

Audio-frequency acoustic signals in gases have been detected by measuring the bending of an optical beam directed through the gas to a custom-built position-sensitive photodetector. The beam deflection is caused by a transverse acoustic density gradient, and can be calculated when the acoustic field is known. The spectrum of a cylindrical resonator was recorded using both a calibrated microphone embedded in one end of the cylinder, and deflection of a laser beam passing through the center of the cylinder along a diameter. Beam deflection is expected for the first plane-wave mode of the resonator and other modes having nonzero average transverse density gradients along the beam path. The observed beam deflections were in qualitative agreement with calculations for all modes which could be resolved. For the first plane-wave mode, the measured and calculated deflections agreed within a few percent. Refinement of this technique could be applied to the absolute calibration of microphones. The beam-deflection technique was found to be sufficiently sensitive for the recording of voice and musical instruments, both in digital form on laboratory instruments and on audio tape. [Work supported by the Army Research Office.]
Direct detection of acoustic waves by laser light diffraction and proposals of the optophone
Authors: Sonoda Yoshito
Published: July 2002

The conventional light diffraction method cannot be applied to the measurement of the acoustic waves with a long wavelength, where the diffracted optical waves propagate in the penetrating optical beam and cannot be measured because of the disturbance by the latter. In this study, the Fraunhofer diffraction method, which was developed as a new means to detect the electromagnetic radiation scattered within the penetrating light beam in the plasma-nuclear fusion research, is applied to the measurement of acoustic waves. It is experimentally demonstrated that the acoustic wave with a wavelength longer than 8.5 mm can be detected by a visible laser of 5 mW, and the amplitude of the electrical output signal from a photodiode is linearly proportional to the sound pressure and the probe laser power, as predicted by the theory. The frequency property and directivity of the optical sound-antenna are roughly estimated by the preliminary experiment. Furthermore, the Optophone (the optical microphone) of various types are proposed as a new acoustic detection method.
Prediction of the difference between CSEL and ASEL of blast sound for correlation purposes with annoyance
Authors: Hirsch Karl W.
Published: July 2002

ISO-TC43/SC1/WG45 plans to have three categories of impulsive sound sources for purposes of noise ratings. Each category, ‘‘ordinary impulsive’’ (adjustment 5 dB), ‘‘highly impulsive’’ (12 dB), and ‘‘high-energy impulsive’’ (significantly more than 12 dB to ASEL) sound, will receive the indicated adjustment to its measured SEL. But these adjustments based on categories of sources do not take into account the change of ‘‘impulsiveness’’ with propagation. This omission raises uncertainties—especially for high-energy blast sounds. Recently published proposals by Buchta and Vos use the differences between CSEL and ASEL at the receiver to determine impulse adjustments that correlate with annoyance. However, this level difference is not reliably obtained by measurement because the spectrum is influenced by local properties of the ground due to superposition, and because the A-weighted levels are close to the background noise level at typical receiver distances. For blasts from explosive sources (e.g., demolitions, weapon firing), this paper presents a theoretical approach to predict CSEL-ASEL using an energy concept forthe sound spectrum. This approach yields an expected value for the dif-ference between C- and A-levels that depends on the acoustical energy of the sound at the source and on the frequency-dependent attenuation along the propagation path.
Wideband noise signatures from low-altitude military jet overflights
Authors: Lomax C. , Kerry G. , James D. J.
Published: July 2002

Public concern about the noise from low-altitude military jet overflights and its alleged effects on the health and annoyance of those overflown has resulted in some restrictions on flying activities at low level, even bans within some countries, being imposed. Much past research into aircraft noise emissions has been based on band-limited noise measurements. Full pressure signatures are required if all possible noise effects are to be fully understood. In 1995 a series of trials was completed in the UK under controlled conditions, and typical wideband noise signatures obtained for a variety of speeds and heights of a Tornado aircraft. Samples of these signatures are presented and the various pertinent characteristics highlighted. The question as to whether these signatures should be considered impulsive is discussed.
An innovative approach to predict sound field in a complex outdoor environment
Authors: Taherzadeh Shahram , Li Kai M. , Attenborough Keith
Published: July 2002

It is well known that the fast field program (FFP) is an accurate numerical scheme for calculating the sound field above a flat ground and in a range-independent environment. On the other hand, the boundary element method (BEM) is most superior for a situation with complicated boundary conditions, such as the presence of noise barriers. However, the successful application of the BEM requires an accurate Green’s function. This requirement somewhat limits the general applicability of the BEM only to the condition of homogeneous medium or other media with a simple sound-speed profile where analytical Green’s function exists. In order to predict the propagation of sound in a complex outdoor environment, a hybrid method is developed that combines the advantages of the BEM and the FFP. In this numerical scheme, the sound field for an inhomogeneous medium is first computed by the FFP. The numerical result is then applied as the input Green’s function for use in the BEM. The new hybrid scheme, fast field boundary element method (FFBEM), is used to investigate the performance of sound barriers and screens in upwind and downwind conditions. [Work supported by EPSRC of UK.]
Sound propagation through time-dependent random media
Authors: Blanc-Benon Ph. , Wert K. , Juvé D.
Published: July 2002

In recent years, several authors have studied the impact of turbulence on sound propagation through numerical simulations. Currently, these simulations model the turbulence using a frozen turbulence hypothesis and a random Fourier modes (RFM) technique, such that the turbulent fluctuation at any point in the medium (either scalar or vectorial in nature) is calculated from the sum of a limited number of time-independent random Fourier modes. The RFM technique is quite easy to implement, and has been used to make accurate predictions of ensemble-averaged sound-pressure level for atmospheric propagation. In this paper, the extension of the RFM method to include simple time evolution of the fluctuations is presented. However, this method produces fields that do not satisfy the Navier–Stokes equations and thus cannot exhibit either the dynamics or the structures found in atmospheric boundary layer (ABL) turbulence. The desire to include ABL turbulence characteristics in simulations of atmospheric propagation has led to consideration of large eddy simulations (LES) for turbulence modeling. Here, numerical simulations obtained using both turbulence models in conjunction with a parabolic equation solver to calculate time-evolving acoustic fields, which are subsequently ensemble averaged to determine statistical characteristics, will be presented. [Work supported by CNRS/NSF and IDRIS under project 960742.]
Spectral element analysis of sound propagation in a muffler
Authors: Lin Wen-Hwang , Sindir Munir M.
Published: July 2002

This paper presents a novel numerical method based on the least-squares spectral element formulation to analyze sound propagation in an expansion-chamber muffler with and without a mean flow. The method solves the linearized acoustic field equations derived from the full Navier–Stokes equations. Effects of the mean flow on the acoustic wave propagation in the muffler were taken into consideration. The method solves the first-order acoustic field equations in a finite number of elements which represent the chamber muffler. Within each element the method first approximates the solutions to these equations by a series of unknown coefficients with known basis functions, forms the residual of the approximation, and then minimizes the integral of the squares of the residual with respect to the unknown coefficients. The resultant system equations were discretized by the spectral element method for spatial derivatives and by the dual time stepping for the temporal derivative. Finally, the algebraic equations were solved by a Jacobin preconditioned conjugate gradient method. Numerical results were presented for pressure contours and transmission loss of sound waves propagating at various frequencies in the muffler. These results were compared with the analytical values available, and the comparison showed very good agreement.
An alternative derivation of Howe’s (1975) formula for the scattering of hydrodynamic flow into sound by solid bodies
Authors: Lin Dan , Powell Alan
Published: July 2002

An alternative way to derive the Green’s function in the presence of a solid body is presented and applied to the case of scattering of hydrodynamic flow into sound. This method utilizes an imaging system of a point source outside a solid sphere. The ‘‘incident potential’’ and the ‘‘scattered potential’’ are obtained in terms of velocity potentials from the original source and the image sources. The total potential and the Green’s function can then be easily derived. The resultant Green’s function G=δ(t−τ−|x−Y|/c)/(4π|x−Y|) is exactly the same as that derived by Howe [J. Fluid Mech. 67, 597–610 (1975)] while the physical meaning is much more clear and less mathematics is involved. Here, x is the vector from the origin to the observation point, and Y is the incompressible flow vector potential in the presence of the solid body. For the case of scattering of hydrodynamic flow into sound, the above Green’s function is substituted in Lighthill’s solution p(x,t)=ρ0∫(∂2uiuj/∂yi∂yj)GdVd τ. The far-field scattered acoustic pressure is then obtained in terms of flow vorticity ζ and the vector stream function Ψx for a unit potential flow around the solid body in the x direction: p(x,t)=(ρ0/4πxc)∂2/∂t2∫Ψx⋅ζ(t−|x| /c)dV, as given by Dowling.
Perceptual segregation and pitch shifts of mistuned components in harmonic complexes and in regular inharmonic complexes
Authors: Roberts Brian , Brunstrom Jeffrey M.
Published: July 2002

It is unclear whether the perceptual segregation of a mistuned harmonic from a periodic complex tone depends specifically on harmonic relations between the other components. A procedure used previously for harmonic complexes [W. M. Hartmann, S. McAdams, and B. K. Smith, J. Acoust. Soc. Am. 88, 1712–1724 (1990)] was adapted and extended to regular inharmonic complexes. On each trial, subjects heard a 12-component complex followed by a pure tone in a continuous loop. A mistuning of ±4% was applied to one of the components 2–11. Subjects adjusted the pure tone to match the pitch of the mistuned component. Near matches were taken to indicate segregation. The complexes were either harmonic, frequency shifted, or spectrally stretched. Performance in the inharmonic conditions was generally as accurate as in the harmonic condition. Small but consistent mismatches, pitch shifts, were found in all conditions. Their direction and size were similar to earlier findings for harmonic complexes. Subsequent tests using a range of mistunings showed that the perceptual segregation of components from regular inharmonic complexes could be sensitive to mistunings of 1.5% or less. These findings suggest that the effects of spectral regularity on auditory grouping are more general than those of harmonic relations.
A modal approach for the acoustic and vibration response of an elastic cavity with absorption treatments and mechanical/acoustical excitation
Authors: Atalla Noureddine , Tournour Michel
Published: July 2002

The calculation of the acoustic and vibration response of an elastic cavity is considered. The presented technique couples a modal decomposition for the structure in vacuo and the cavity with a coordinate transformation to allow for efficient determination of the coupled modes. Using these coupled modes, it rewrites the coupled equations accounting for the impedance condition at the treated elastic walls, internal acoustic sources, and mechanical excitations in terms of a compact forced system. The theory behind the method is presented together with validations and numerical examples.
The effect of large structural perturbations on the response of structural-acoustic systems
Authors: Hahn Steven , Ferri Aldo
Published: July 2002

Due to high sensitivity, first-order perturbation analysis of structural-acoustic systems can be inaccurate for large perturbations. Using high-order derivatives to create a Taylor series approximation for the perturbed solution can result in slow convergence or even divergence. A rational polynomial or Pade approximation may overcome the poor convergence of the Taylor series by canceling out the pole causing the poor convergence. In this study, a finite element framework is used to describe the structural-acoustic system. External radiation and scattering problems are accommodated by truncating the infinite fluid region using exponential decay infinite elements. Changes to a nominal model are introduced through a structural perturbation that modifies the nominal structural stiffness matrix. An efficient method for calculating the solution derivatives with respect to the structural perturbation is presented. A Taylor series expansion is constructed using the derivative information and the convergence criteria for the series is examined. The local solution and derivatives are then used to construct a Pade approximation. The method is illustrated using several numerical examples. The approximation is shown to be quite accurate for large perturbations even when there are one or more nearby poles and the Taylor series fails to converge.
A modal formulation for an arbitrary submerged structure in a heavy acoustic medium
Authors: Chen Pei-Tai
Published: July 2002

The paper studies radiational and dynamic characteristics for an arbitrary elastic structure submerged in a heavy acoustic medium. The equation of motion for the coupled structural/acoustical system is formulated. In the equation, the acoustic loading is expressed as a symmetric complex matrix derived by a surface acoustic reciprocal principle. Due to the symmetric formulation, the ratio of the complex input power exerted by an external force yields an expression for the ratio of quadratic representations of the vibration velocity. A consideration of the stationarity leads to a symmetric eigenvalue problem, in which the eigenvalue is related to the radiation efficiency for the vibration velocity corresponding to the eigenvector. Based on the eigensolution, the forced vibration of the coupled system is decomposed into a set of mutual orthogonal equations where each equation represents a one-degree-of-freedom mass/spring/dashpot system having an impedance determined by the eigensolution. A spherical shell and a slender spheroidal shell are chosen as numerical examples to demonstrate the present analysis.
Dispersion-free finite-element methods for the Helmholtz equation
Authors: Barbone Paul E. , Harari Isaac
Published: July 2002

The problem of dispersion in finite-element approximations of solutions of the Helmholtz equation are considered. Dispersion errors can accumulate over large propagation distances. Such error is sometimes called the ‘‘pollution error.’’ Via a one-dimensional example, it is shown that the dispersion error is linked to the fact that standard finite-element approximations are not optimal (in the sense of H1 best approximation) for the Helmholtz equation. Thus to eliminate dispersion error in finite-element solutions, the problem of finding the H1 projection onto a finite-element space of a field satisfying the Helmholtz equation is examined. In one dimension, exact optimality of the finite-element approximation is achieved, and thus exactly zero dispersion is obtained. This leads to a finite-element formulation that is nodally exact in one dimension on any linear mesh. In higher dimensions, or formulation is approximately optimal and nonsymmetric. The formulation itself yields an expression for the ‘‘distance’’ from optimality, related to the lack of symmetry. Examples are shown that demonstrate the performance of the method in one and two dimensions. [Supported by ONR.]
A wave-based prediction technique for vibroacoustics: Comparison with the finite-element technique and experimental validation
Authors: Sas Paul , Desmet Wim , Vandepitte Dirk
Published: July 2002

In a coupled vibroacoustic analysis, a structural and acoustic finite-element model must be solved simultaneously. This results in a very large, nonsymmetrical coupled model, which requires a computationally expensive solving procedure. To reduce the size of a coupled model, a wave-based prediction technique has been developed. Instead of dividing the structural and acoustic domain into small elements and solving the dynamic equations within each element using simple approximating shape functions, the entire structural and acoustic domains are described by plane-wave functions, which are exact solutions of the structural and acoustic homogeneous wave equation. To these wavefunctions, particular solutions of the inhomogeneous wave equations are added, so that the governing dynamic equations are exactly satisfied. The contributions of the wavefunctions to the coupled vibroacoustic response are determined by applying the boundary conditions in a weighted residual formulation. The wave technique has been used for the prediction of the acoustic pressure in the cavity of a car breadboard model by applying the measured structural velocity distribution as boundary conditions to the car cavity. The prediction results of the wave model are compared with the finite-element predictions and the measured cavity pressure field.
Amplitude modulation cues for perceptual voicing distinctions in noise
Authors: Strope Brian P. , Alwan Abeer
Published: July 2002

Fricatives are produced by forming a sufficiently narrow constriction in the vocal tract to generate a turbulent noiselike source. With voiced fricatives, vibrating vocal folds introduce low-frequency energy at the first few harmonics of the fundamental frequency. Measurements using the relative level of the first harmonic have been shown to be good indicators for voiced/unvoiced fricative distinctions [e.g., Pirello et al., J. Acoust. Soc. Am. 101, 3754–3765 (1997)]. In the current study, fricatives [s z] with the vowels [i a u] were recorded as CV syllables from four talkers. Perceptual thresholds for syllable detection and voicing distinction were measured in noise. Subjects were able to make reliable voicing distinctions at low SNRs after the fricatives were manually isolated from the vowels and spectral components below 3 kHz were removed. Temporal analyses indicate that during voiced fricatives the vibrating vocal folds can modulate the pressure source behind the constriction sufficiently to generate an acoustic pitch-rate amplitude-modulation cue in high-frequency regions. Predictions of the perceptual experiment’s thresholds are evaluated for psychoacoustic models of amplitude-modulation detection which use the standard deviation of the temporal envelope, modulation filter banks, and summary autocorrelograms. [Work supported by NIDCD Grant No. DC02033 and NSF.]
Speech enhancement by a Kalman filter based on wavelet transformation coefficients
Authors: Nishimura Ryouichi , Suzuki Yôiti , Sone Toshio , Asano Futoshi
Published: July 2002

A new speech enhancement technique based on Kalman filtering and wavelet transformation is proposed. A problem in using a Kalman filter for speech enhancement lies in how to construct and to estimate the state transition matrix. Considering that wavelet transformation can well localize the speech energy in the time-frequency domain in the presence of noise, wavelet coefficients are used here for this purpose. That is, the state and observation vectors are expressed by matrices which have column vectors consisting of wavelet coefficients calculated from densely overlapped frames. Then the state transition matrix is calculated from a single state matrix postmultiplied by the inverse matrix of the preceding state matrix. These matrices are obtained from a speech signal enhanced by existing algorithms such as MMSE. This enhancement process does not need to correctly estimate a speech signal itself but needs just to supply the correct differentials of state matrices. A computer simulation was conducted to evaluate the performance of the proposed method. The result shows that the signal processed by the proposed method generally gives a better subjective impression while physical evaluation by use of the ‘‘signal to deviation ratio’’ becomes worse.
Comparison of methods for analysis of cyclostationary noise
Authors: Vokurka Karel
Published: July 2002

A great number of machines work cyclically. Hence the noise they generate is cyclostationary. A traditional approach to this noise analysis is based on an assumption of its stationarity. This assumption implies continuous time averaging. Unfortunately in this way a certain amount of information concerning, e.g., time-frequency distribution, is lost. Methods have been looked for to preserve this information. They all are based on periodic time averaging and the resulting statistical characteristics are known as gated spectrum, cyclic correlation, cyclic autospectrum, double autocorrelation, double autospectrum, etc. Each of the methods has its advantages and disadvantages. These may concern processing time, hardware requirements, frequency resolution, occurrence of artifacts (cross terms), and others. In this paper the methods are analyzed and compared and possible improvements in their performance are suggested. [Work supported by the Grant Agency of the Czech Republic and by the European Commission.]
Localized wave pulses in the Keyport experiment
Authors: Chambers David H. , Lewis D. Kent
Published: July 2002

Localized wave (LW) pulses were produced using a standard Navy array in the anechoic tank at NUWC Keyport. The LW pulses used were the MPS pulse first derived by Ziolkowski, and a new type of pulse based on a superposition of Gaussian beam modes. This new type is motivated by a desire to make a comparison of the MPS pulse with another broadband pulse built from solutions to the wave equation. The superposed Gaussian pulse can be described by parameters which are analogous to those describing the MPS pulse. The directivity patterns and the axial energy decay between the pulses are compared. The behavior of the pulses are found to be similar so that the superposed Gaussian could be another candidate in the class of low diffractive pulses known as localized waves.
Localized wave generation with a standard underwater array
Authors: Lewis D. Kent , Chambers David H. , Ziolkowski Richard W.
Published: July 2002

Recent work at the NUWC Keyport has generated localized waves using Navy field equipment. The array, a rectangular arrangement of tonpiltz elements, was driven with precompensated signals to generate sound covering a decade of usable bandwidth. The elements were grouped by radius from the center and excited by signals designed specifically for each radius, for a total of 7 radii. Results of the angular scans show a narrowed beam pattern and lowered side lobes relative to design signals. Results of axial range scans show an increase in directivity of more than an order of magnitude over array specific tone bursts. Frequency analysis shows that the main beam is an octave wide while the surviving side lobes are narrow bandwidth.
Optimal array element localization
Authors: Dosso Stan E. , Sotirin Barbara J.
Published: July 2002

Measuring ocean acoustic fields at an array of sensors allows the application of advanced signal processing methods such as beamforming and matched-field processing. However, these methods require accurate knowledge of the positions of individual sensors. Typically, an acoustic survey is required to localize the sensors, a procedure referred to as array element localization (AEL). AEL generally consists of measuring the traveltimes of acoustic signals transmitted from a series of known positions to the sensors to be localized. These traveltime data can then be inverted for estimates of the sensor locations using a linearized inversion algorithm. An important issue in AEL is designing the configuration of acoustic source positions: a well-designed source configuration can produce substantially better AEL results than a poor configuration. In this paper, a procedure is developed to determine optimal AEL source locations for arrays of any configuration. This procedure minimizes the condition number of the Jacobian matrix of partial derivatives on which the linearized inversion is based. Minimizing the condition number in effect minimizes the magnification of data (traveltime) errors into model (sensor position) errors in the inversion. Monte Carlo simulations verify that optimal AEL source configurations can lead to significant improvements in sensor localization.
Effects of environmental mismatch on Bartlett sidelobe broadband interference structures
Authors: Thode Aaron M. , D’Spain Gerald L. , Song Hee Chun , Kuperman William A.
Published: July 2002

When a series of perfectly matched range-independent Bartlett surfaces (computed over small increments of frequency) are stacked and then sliced along a constant depth, the resulting sidelobe contours in the range-frequency plane display interference patterns that converge to the correct range [Thode et al., J. Acoust. Soc. Am. 102, Pt. 2 (1997)]. The existence of these patterns can be derived from waveguide invariant principles [e.g., G. A. Grachev, Acoust. Phys. 39, 33–35] and their physical meaning interpreted using a time-reversal argument [Song et al., J. Acoust. Soc. Am. 102, Pt. 2 (1997)]. Several qualitative effects of environmental model mismatch on these patterns have been observed: pattern translation along the range axis, frequency-dependent warping, and ‘‘ghost’’ contours that converge to the range origin instead of the true source range. Translational shifts are produced by certain mismatch parameters (e.g., waveguide depth) associated with invariant theory. Warping at low frequencies is generated by a mismatched bottom sound speed, and can be explained using ‘‘effective depth’’ concepts [G. L. D’Spain, 15th Int. Cong. Ac. Proc., 231-4]. ‘‘Ghost’’ patterns arise when the modeled environment contains more modes at a given frequency than the actual environment. A time-reversal hypothesis for their convergence to the range origin is suggested. [For Underwater Acoustics Best Student Paper Award.] [Work sponsored by ONR.]
The virtual orchestra; acoustical and audio engineering issues
Authors: Campbell Richard H. , Bianchi Frederick W.
Published: July 2002

The multichannel MIDI system known as the ‘‘Virtual Orchestra’’ has been used several times in the pit for the performance of opera, and recently demonstrated at an ASA regional chapter meeting in Boston. This paper discusses technical issues such as the selection of the types of loudspeakers and their placement in the pit, the amplifier power requirements, and the sound level calibration for each instrumental section based on a mezzo-forte norm. ‘‘Wolf’’ tones caused by understage extension cavities and other pit deficiencies can be easily modified within the MIDI computer program or with external equalization. Ideas are presented for the use of this new tool with respect to an acoustic freedom heretofore unavailable to orchestrators of musical theater works. The computer operator’s ability to follow in real time the conductor’s direction in nuance and tempo guarantees a cohesive performance synchronized with the singers and the dramatic action.
Individual subjective preference of listeners for vocal music sources in relation to the subsequent reverberation time of sound fields
Authors: Sakai Hiroyuki , Setoguchi Hiroshi , Ando Yoichi
Published: July 2002

The purpose of this study is to evaluate subjective preference of a simulated sound field by listeners in changing subsequent reverberation time Tsub using vocal music sources. Previously, a great deal of effort has been made on the study using music or speech [for example, Ando et al., Acustica 50, 134–141 (1982); J. Acoust. Soc. Jpn. 39, 89–95 (1983)]. In addition to subjective preference judgments, the α-waves’ range of the continuous brain waves (CBW) in relation to the specialization of human cerebral hemispheres is also evaluated [C. Chen and Y. Ando, J. Archit. Plann. Environ. Eng., AIJ 489, 73–80 (1996)]. In this paper, subjective evaluation using vocal music sources, which is often played in concert halls and opera houses, has been examined. Subjective preference tests were conducted changing Tsub, which is one of the four objective parameters in relation to subjective preference of sound fields. Individual differences of subjective preference as well as global preference are discussed. [Work was partially supported by the Ministry of Education, Grant-in-Aid for Scientific Research (C), 9838022, 1997.]
Scale effects as constraints in insect sound communication
Authors: Bennet-Clark Henry
Published: July 2002

Calling insects have problems of optimizing range and maintaining the specificity of the call. Higher frequencies are more easily refracted and reflected by objects in the environment. Smaller insects have less muscle power and also, because of the small sound source size, higher frequencies are radiated more efficiently than lower frequencies. In open air or water, the sound spreads spherically and decays by the inverse square law. If the sound can be confined to a sheet it decays as the inverse of range while within a rod it decays due to viscous losses; such calls are usually rather simple pulses and rely on initial time of arrival because of multiple pathlengths in the environment. With airborne sounds, those in the range from 1 to 10 kHz tend to have sustained pure-tone components and a specific pattern of pulses which propagates well; but with higher frequencies pulses tend to become briefer and, once again, to rely on time of arrival of the onset.
Acoustic detection and identification of insects in soil
Authors: Mankin Richard
Published: July 2002

There is considerable practical need for user-friendly, inexpensive devices that detect and quantify insect populations in environments hidden from visual observation. One approach that has been used with varying success has been to detect the insects through the sounds or vibrations they generate for communication or through noises that are produced incidentally during feeding and general movement. The ability to precisely monitor soil insect populations is limited by interference from background noise and the high rate of attenuation of sound in soil. This paper describes experiments using different sensors and analysis techniques for detection of insects in soil in an agricultural environment. Results from different sensors are compared, and the spectral and temporal patterns that can be used to distinguish the target insects from noise and nontarget soil organisms are discussed. The use of accelerometers attached to 20–30-cm nails appears to be a low-cost, user-friendly method to locate and monitor the size of infestations of soil insects that tend to group together in clumps.
Bioacoustic correlates of female choice in European starlings
Authors: Gentner Timothy Q. , Hulse S. H.
Published: July 2002

The elaborate structure of male European starling song suggests that it is a trait under heavy sexual selection pressures, and the results of several studies in both the laboratory and the field have identified song as the only male characteristic correlated with female choice in this species. However, previous studies have failed to isolate the bioacoustic feature(s) of song that are important for mating decisions and preferences in female starlings. An operant apparatus that reinforces a natural approach response to potential nest sites with different male starling songs is used to demonstrate that female preference is positively correlated with song bout length but not repertoire size (two features that normally covary). Further, this preference for longer song bouts is made in such a way that the absolute length of a bout cannot be the feature upon which the preference is based. A method for quantifying the temporal structure and stereotypy in male starling songs is presented using information theory, and it is shown that these measures correlate very closely with different song bout lengths. The importance of song bout stereotypy for female preference is then tested using synthetic stimuli or operant apparatus.
Ex vivo studies of the effect of high-intensity focused ultrasound on whole human blood
Authors: Poliachik Sandra , Bloch Susanah , Bailey Michael , Kaczkowski Peter , Cleveland Robin , Mourad Pierre D. , Porter Tyrone , Crum Lawrence A. , Chandler Wayne L. , Keilman George W.
Published: July 2002

A surgical application of high-intensity focused ultrasound (HIFU) is hemostatis. In this application, both tissue and blood will be subjected to HIFU. What will happen to blood? The intent of this study is to explore via experiment some of the bioeffects of HIFU on whole human blood. A 1.1-MHz piezoceramic source with a 60-mm radius of curvature and 100-mm aperture was used. Special acoustically transparent containers were made of handmade, low-density polyethylene tubing. Phenomena studied included hemolysis, morphologic changes in erythrocytes, white blood cell differential, and platelet activation, all as a function of acoustic intensity and dosage. Intensities up to 6000 W/cm2 were used in cw pulses of one second. The bioeffects noted above were correlated with temperature and a passive acoustic measure of bubble activity within the blood created by the ultrasound. Under the acoustic conditions considered for this work, nonthermal acoustic effects were most strongly associated with bioeffects. [Work sponsored by DARPA.]
Shaping of focused ultrasonic beams to expedite thermal necrosis in tumor therapy
Authors: Lizzi Frederic L.
Published: July 2002

Ultrasonic tumor therapy employing focused beams shows great promise for treating tumors by producing spatial matrices of thermal-necrosis lesions. A practical problem involves the long time required to treat extended tumor volumes. To treat ocular tumors, our laboratories are investigating beams with asymmetric shapes to expedite the production of lesion matrices. The beams are generated using rectangular strip electrodes plated on spherical-cap ceramic transducers. The phase and amplitude of the strip excitation voltages are controlled to launch beams whose focal-zone patterns consist of a sequence of lobes confined within elliptical, rather than circular, cross sections. A simple theoretical model has shown that thermal diffusion between these lobes can produce lesions with elliptical cross sections; lesion matrices would be readily produced by translating such transducers along the short axis of the lesion cross section, thereby causing necrosis in broad regions. The concept has been verified in in-vitro experiments (in liver and the ocular lens) and in in-vivo exposures of human tumor explants in nude mice. [Work supported by NIH Grant EY10369.]