bluuebunny/crossref_metadata_2025 huggingface dataset:
Selective adaptation by context-conditioned fricatives
Authors: Cheesman Margaret F. , Greenwood Kristina G.
Published: October 2005

The role of vowel context and consonant labeling in the selective adaptation of voiceless fricatives was examined in three experiments. This approach was designed to determine whether selective adaptation effects occurred with voiceless fricative stimuli and to determine whether any such effects had a linguistic basis as opposed to a purely auditory basis. Two synthetic fricative-vowel continua were used; one ranged from [si] to [∫i] and the other from [su] to [∫u]. Identification of the consonant portion of the syllables in these continua, as either [s] or [∫], depended on both the frequency of the friction noise and on the vowel quality. In experiment 1, the end points of the continua were used as adaptors, and the identification boundary shifted toward the adapting stimulus. In experiment 2, an ambiguous frication noise (that was identified as [s] before [u] and as [∫] before [i]) adapted the identification boundary in opposite directions, depending on which of the two vowels followed the noise. Thus the direction of adaptation depended on the perceptual identity of the consonant. In the final experiment, the isolated [i] and [u] vowels, and the isolated ambiguous frication noise, were demonstrated to be ineffective adaptors. The selective adaptation effects observed in these experiments were not determined by the acoustical information in the consonant or the vowel alone, but rather by the context-conditioned percept of the fricative. These results extend the reports of other research that has attempted to dissociate auditory from linguistic adaptation, provide further evidence that selective adaptation effects have multiple loci, and establish for the first time a selective adaptation effect which is unambiguously, not acoustically based.
A proposed microscopic elastic wave theory for ultrasonic backscatter from myocardial tissue
Authors: Rose James H. , Kaufmann Mark R. , Wickline Samuel A. , Hall Christopher S. , Miller James G.
Published: October 2005

The physical structures responsible for ultrasonic scattering from myocardial tissue have not yet been conclusively defined. It is hypothesized in this paper that the backscatter from myocardium is primarily due to inhomogeneities approximately the size of the myocytes. In particular, it is proposed that the acoustic contrast responsible for the scattering is that between the extracellular collagen network that surrounds each myocyte (or myocyte bundle) and the rest of the tissue (the myocytes’ intracellular contents). To test this hypothesis, a simple elastic wave scattering model for myocardium was developed. An elementary scatterer is modeled as an ellipsoidal shell, having the material properties of wet collagen, imbedded in a host medium having the average properties of myocardium.

The first Born approximation to elastic scattering is used to calculate the frequency-dependent scattering from a single scatterer. To scale up from a single scatterer to a distribution of scatterers, it is assumed that the power received at the transducer is simply the sum of the power scattered in the direction of the transducer by each individual scatterer located in the active volume of the beam (an independent-scatterer approximation). Calculations are restricted to the backscattering direction (pulse-echo), although the theory can accommodate pitch–catch scattering at all angles. With the aid of a computer program, the acoustic backscatter coefficient is calculated using the Born formalism and then measurement effects (frequency-dependent beam width and attenuation correction factors) are incorporated to arrive at calculated integrated (frequency-averaged) backscatter. Both the backscatter coefficient and integrated backscatter are calculated for angles of incidence that range from parallel to the long axis of the scatterer to perpendicular to this fiber direction. For the low MHz frequencies typically used in clinical echocardiography, the calculated absolute magnitude of the acoustic backscatter coefficient lies within a range from 0.0001 to 0.001 cm−1 sr−1. For selected fiber geometries, the anisotropy in integrated backscatter as the angle of incidence is varied with respect to the fiber orientation is about 10 dB.

The predicted frequency dependence of the acoustic backscatter coefficient is calculated to be about f3.9 in the low MHz frequency range. These calculated results are reasonably consistent with published experimental measurements and provide a successful preliminary test of the hypothesis.
Dimethylformamide as an enhancer of cavitation-induced cell lysis in vitro
Authors: Jeffers Russell J. , Feng Ruo Qin , Fowlkes J. Brian , Hunt John W. , Kessel David , Cain Charles A.
Published: October 2005

Polar solvents, including dimethylformamide (DMF), have been investigated as anticancer drugs, but their potential usefulness is constrained by hepatotoxic side effects. The ability to enhance drug cytotoxicity with ultrasound would be valuable in creating locally intense chemotherapy while minimizing effects peripheral to the treatment site. The effects of continuous wave ultrasound (US) (985 kHz; 0.5–2.5 W/cm2) were evaluated on cultured HL-60 human promyelocytic leukemia cells alone and with a noncytotoxic DMF dose (0.11 M). The cells were insonified in a configuration that created no cell lysis without the introduction of albumin-stabilized microbubbles into the exposure chamber. When microbubbles were introduced, US with bubbles induced cell lysis, and the presence of DMF significantly increased the lysis induced by ultrasound with bubbles. The necessary presence of microbubbles for the DMF–US synergism to occur suggests that a likely mechanism is acoustic cavitation, initiated by the presence of microbubbles as nuclei. Detection of subharmonics confirmed the presence of cavitation, and cell lysis was well correlated with the subharmonic amplitude. The results show that albumin-stabilized microbubbles, similar to those currently used as US contrast agents, may provide a significant source of nuclei and improve prospects for cancer therapy using acoustic cavitation. The evidence presented supports the hypothesis that cell damage is due to a sonochemical rather than to a sonomechanical process.
Cavitation phenomena generated by a lithotripter shock wave
Authors: Carnell M. T. , Fiadeiro P. T. , Emmony D. C.
Published: October 2005

A focused electromagnetic acoustic transducer (EMAT) has been used to produce high-intensity shock waves in water. Schlieren imaging of the field has shown the complex structure of not only the main shock transient but also that associated with cavitation in the field. The primary source of cavitation is, as expected, due to the rupture and subsequent collapse of bubbles generated in the water by the main shock. The images give evidence for the interaction of these primary cavitation shocks with bubbles in the field. The collapse of some of these bubbles gives rise to additional or secondary cavitation shock transients which expand symmetrically. This appears not to be the case for the primary events and some bubbles, which look highly distorted.
On the accuracy of modal analysis in reverberant acoustical systems with damping
Authors: Franzoni Linda P. , Dowell Earl H.
Published: October 2005

That the modal analysis method works well regardless of the amount of damping in the system, provided that modal coupling is included in the analysis, is shown. The soundfield produced by a vibrating piston in a tube with an absorptive end is calculated. An exact solution is compared to results computed by modal analysis with and without the inclusion of modal coupling. Recent published results, which did not include the effects of modal coupling, incorrectly concluded that discrepancies were due to limitations of modal analysis, rather than the uncoupling assumption.
A second note on the prediction of sound intensity
Authors: Pan J.
Published: October 2005

The coupling between different rigid-wall modes is often neglected in the prediction of sound-pressure field in lightly damped rooms. This author pointed out in a recent Letter to the Editor that although the sound-pressure field can be calculated to sufficient accuracy, the uncoupled model fails to give a correct description for the sound intensity field in the rooms. Following this Letter, Franzoni and Dowell carried out more detailed studies and showed that the neglecting of the rigid-wall modal coupling is the cause of the error in the prediction of sound-pressure field, but they made no comment on the prediction of sound intensity field. In this Letter, the convergence problem inherited in the rigid-wall mode model with or without the inclusion of modal coupling in the prediction of sound intensity field is revealed.
Experimental determination of wind speed and direction using a three microphone array
Authors: Bass Henry E. , Raspet Richard , Messer John O.
Published: October 2005

Recent studies indicate that the major sources of wind noise (under 50 Hz) measured on outdoor microphones is due to turbulent eddies moving across the microphone [S. Morgan and R. Raspet, J. Acoust. Soc. Am. 92, 1180–1183 (1992)]. Taylor’s frozen turbulence hypothesis states that these eddies retain their shape over a distance large compared to the size of the eddy. Thus it may be reasonable to assume that each eddy presents a specific acoustic signature that remains somewhat stable over a finite distance and time. If this is true, the cross correlation time for signals from two microphones a known distance apart should correspond to the travel time for an eddy to traverse the distance between the microphones. Assuming that the speed and direction of the eddy is the same as the ambient wind, enough information exists to calculate the wind speed and direction.
Failure to hear binaural beats below threshold
Authors: Gu Xiang , Wright Beverly A. , Green David M.
Published: October 2005

The ability to hear binaural beats at 500 Hz was assessed using a tone presented at 20 dB SL to one ear and a tone presented at a variable level ranging from −20 to 20 dB SL to the other ear. The tones at the two ears differed in frequency by 1, 3, or 6 Hz in different experiments. A two-alternative, forced-choice test was used to measure the listener’s ability to detect the beats. Special care was taken to avoid a potential pitch cue. There was no evidence to suggest that binaural beats were detectable when the intensity of the variable-level tone was below 0 dB SL.
Describing-function theory for flow excitation of resonators
Authors: Mast T. Douglas , Pierce Allan D.
Published: October 2005

A theory is presented for the mechanism by which resonators are excited by grazing flow. The theory allows prediction of oscillation characteristics for the range of Reynolds numbers, frequencies, and resonator amplitudes for which the acoustically excited mean flow rolls up into discrete vortices. The resonator-flow system is treated as an autonomous nonlinear system. Limit cycles of the system are found using describing-function analysis, in which each component of a nonlinear oscillating system is represented by an associated frequency-response function. This mathematical approach is shown to be a generalization of models in which the resonator and flow are considered parts of a feedback system. The theory’s predictions for the frequencies of oscillation compare favorably with experiment. The results indicate that both ‘‘edge’’ and ‘‘resonator’’ feedback contribute to the mechanism of self-excited oscillations of the resonator-flow system.
Benchmark cases for outdoor sound propagation models
Authors: Attenborough K. , Taherzadeh S. , Bass H. E. , Di X. , Raspet R. , Becker G. R. , Güdesen A. , Chrestman A. , Daigle G. A. , L’Espérance A. , Gabillet Y. , Gilbert K. E. , Li Y. L. , White M. J. , Naz P. , Noble J. M. , van Hoof H. A. J. M.
Published: October 2005

The computational tools available for prediction of sound propagation through the atmosphere have increased dramatically during the past decade. The numerical techniques include analytical solutions for selected index of refraction profiles, ray trace techniques which include interaction with a complex impedance boundary, a Gaussian beam ray trace algorithm, and more sophisticated approximate solutions to the full wave equation; the fast field program (FFP) and the parabolic equation (PE) solutions. This large array of computational approaches raises questions concerning under what conditions the various approaches are reliable and concerns about possible errors in specific implementations. This paper presents comparisons of predictions from the several models assuming a complex impedance ground and four atmospheric conditions. For the cases studied, it was found that the FFP and PE algorithms agree to within numerical accuracy over the full range of conditions and agree with the analytical solutions where available. Comparisons to ray solutions define regimes where ray approaches can be used. There is no attempt to compare calculated transmission losses to measurements.
Biot model of sound propagation in water-saturated sand
Authors: Chotiros Nicholas P.
Published: October 2005

Elastic theory of wave propagation and the measured speed of sound in sandy ocean sediments indicate that such sediments are impenetrable to high-frequency sound at shallow grazing angles. The speed of sound in water-saturated, unconsolidated sand is in the region of 1700 m/s which, under the elastic theory of wave propagation, gives it a critical grazing angle in the region of 28°. At shallower grazing angles, refraction is not permitted, and total internal reflection is predicted. Recent experimental measurements contradict this view. Biot’s theory of acoustic propagation in porous sediments is the most likely explanation. Biot’s theory of acoustic propagation, as it applies to water-saturated sand, is reviewed. The speed of the slow wave is found to be higher than previously predicted. New input parameter values are deduced.
Measurement and modeling of dispersive pulse propagation in drawn wire waveguides
Authors: Madaras Eric I. , Kohl Thomas W. , Rogers Wayne P.
Published: October 2005

An analytical model of dispersive pulse propagation in semi-infinite cylinders due to transient axially symmetric end conditions has been experimentally investigated. Specifically, the dispersive propagation of the first axially symmetric longitudinal mode in thin wire waveguides, which have ends in butt contact with longitudinal piezoelectric ultrasonic transducers, is examined. The method allows for prediction of a propagated waveform given a measured source waveform, together with the material properties of the cylinder. Alternatively, the source waveform can be extracted from measurement of the propagated waveform. The material properties required for implementation of the pulse propagation model are determined using guided wave phase velocity measurements. Hard tempered aluminum 1100 and 304 stainless steel wires, with 127, 305, and 406 μm diam, were examined. In general, the drawn wires were found to behave as transversely isotropic media.
Broadband electrostatic transducers: Modeling and experiments
Authors: Anderson Michael J. , Hill James A. , Fortunko Christopher M. , Dogan Numan S. , Moore Russell D.
Published: October 2005

A model for broadband electrostatic transducers capable of generating and detecting ultrasound in air at megahertz frequencies has been developed. This model uses a lumped parameter approximation to describe a transducer with a grooved backplate and a stretched diaphragm. The mechanical stiffness effects included in the model are compressibility of the air gap separating the diaphragm and the backplate, flexure bending stiffness of the diaphragm, and in-plane tension forces applied to the diaphragm. A prototype transducer with backplate grooves 200 μm wide and 3.75 μm deep was constructed using micromachining techniques. Measurements of the electrical admittance and transmit sensitivity were made at various polarization voltages and diaphragm tensions. Model predictions of transducer electrical admittance and transmit sensitivity compare well with experimental data. The resonance frequency is predicted within 50 kHz of the nominal measured value near 500 kHz, and model predictions of transmit sensitivity were within 0–4 dB of measured values.
Sensitivity enhancement in laser ultrasonics using a versatile laser array system
Authors: Steckenrider J. Scott , Murray Todd W. , Wagner James W. , Deaton John B.
Published: October 2005

Past investigators have predicted and, in limited cases, demonstrated the potential utility of using temporally and spatially modulated laser array sources as a means of increasing the signal-to-noise ratio in laser ultrasonic systems without causing the surface damage characteristic of a single high-power laser point source. In an effort to develop a practical and flexible laser array source, a laser system has been designed and implemented which uses a single Nd:YAG pulsed laser and an optical delay system in which the laser pulse passes repetitively through a White cell cavity being sampled by a custom beamsplitter after each pass. Up to ten spatially separated light beams exit from the system each time a single laser pulse is introduced. Time separation between the distinct pulses can be adjusted over a range from 28 to 170 ns, corresponding to a pulse repetition rate from 6 to 36 MHz. Since individual control of the beam paths is possible, one has the flexibility to implement either a single-element, temporally modulated array, or a multielement, ‘‘phased’’ array. From a single point, a multiple spike narrow-band acoustic signal is generated, permitting greater detection sensitivity than can be obtained with broadband detection of a single spike. Alternatively, multielement arrays can be used to increase the acoustic signal amplitude by superposition of the signals generated from each individual element, once again enhancing detection sensitivity.
Flexural wave transmission through angled structural joints
Authors: Guo Y. P.
Published: October 2005

This paper studies the interactions between incident flexural waves and a structural joint that connects two identical elastic beams at an arbitrary angle. The beams are described by classical beam theory and the joint is modeled with stiffness, dissipation, and mass, all in three degrees of freedom, namely, in longitudinal and flexural displacements as well as rotation. Coefficients of flexural wave transmission, reflection, dissipation, and conversion to longitudinal waves are derived, and are analyzed to reveal the functional dependence of these coefficients on parameters such as frequency, joint angle, and various joint parameters. Discussions are also given on potential ways of minimizing flexural wave transmission through a joint.
A time domain study of active control of sound transmission due to acoustic pulse excitation
Authors: Koshigoe Shozo , Teagle Allen , Gordon Alan
Published: October 2005

A time domain model for simulating the noise transmission through an elastic plate into a rigid cavity has been developed. This model is used to study the noise attenuation capability of the filtered-x least-mean-square (LMS) feedforward control algorithm for the case where the model is excited by an acoustic pulse. Piezoelectric transducers (PZT’s) are considered to be bonded on the elastic plate and are used as actuators in the control scheme. In this study, the fully coupled acoustic–plate interaction equations are solved using time-dependent Green’s function techniques, where a time-varying mean air density is considered. The effects of this variation on the transmission of sound and on the stability of the filtered-x LMS adaptive controller are discussed.
Predicting noise-induced sleep disturbance
Authors: Pearsons Karl S. , Barber David S. , Tabachnick Barbara G. , Fidell Sanford
Published: October 2005

The findings of 21 studies of the effects of noise on sleep were reanalyzed in an effort to develop a quantitative dosage-response relationship. Large and systematic differences in sleep disturbance were observed between the findings of studies conducted in laboratory and in field settings. The influence of noise on sleep was also found to depend on additional factors such as the nature of noise and response metrics, noise source, background noise level, length of study, and sex of test participants. No reliable quantitative model for sleep disturbance could be developed from the studies reviewed.
Evaluation of the performance of suspended baffle arrays in typical industrial sound fields. Part I. 1:8 scale-model experiments
Authors: Hodgson Murray , Eldada Mazen Victor , Simard Louis-Philippe
Published: October 2005

In order to determine the performance of baffles in nondiffuse fields such as those found in typical industrial workrooms, reverberation times and steady-state sound-pressure levels were measured in a 1:8 scale-model workroom with variable dimensions, containing various arrays of baffles. The objective was to determine the effect of changes in various room and baffle-array parameters on the sound field as characterized by the early-decay time and the sound-propagation function. The parameters studied were fittings, room height, roof shape, baffle density, baffle pattern, baffle aspect ratio, baffle thickness, and baffle composition. The experimental results show that the changes depend on room geometry and on whether the room is empty or fitted, and that they are different for early-decay time and for sound-propagation function. The most significant results were that roof shape and baffle pattern have little effect; increased baffle density generally results in reduced early-decay time and sound-propagation level, but using too high a density is ineffective; baffle aspect ratio had a small effect; high baffles are slightly more effective than wide ones; increasing the baffle thickness resulted in slightly lower early-decay times and sound-propagation levels; nonabsorbent baffles were much less effective than absorbent ones.
Transducer resolution and the turbulent wall pressure spectrum
Authors: Lueptow Richard M.
Published: October 2005

The size of a pressure transducer will affect the accuracy of measurements of the wall pressure beneath a turbulent boundary layer because of spatial averaging over the sensing area of the transducer. The effect of transducer size on the wall pressure spectrum was investigated by numerically applying wave-number filters corresponding to various size and shape transducers to a database of wall pressure generated from a direct numerical simulation of turbulent channel flow. Circular transducers with piston-type and deflection-type sensitivities were modeled along with square transducers having piston-type sensitivity. The rms wall pressure is attenuated less for a deflection-type transducer than for a piston-type transducer of the same area. The wave-number spectrum of the wall pressure measured using a large transducer has lobes and zeros corresponding to those in the wave-number response function of the transducer. These lobes and zeros in the wave-number spectrum are also evident in the frequency spectrum, although they are smeared. Using Taylor’s frozen field hypothesis, an approximate upper bound on the frequency of wall pressure fluctuations that can be measured before the zeros in the wave-number response function is ωd/Uc<C, where ω is the frequency, d the dimension of the transducer, Uc the convection velocity, and C 6.3, 7.7, and 11.0 for square piston, circular piston, and circular deflection transducers, respectively. The Corcos correction to the wall pressure spectrum recovers the true spectrum within this bound.
Detection performance of the ideal decision function and its McLaurin expansion: Signal position unknown
Authors: Brown David G. , Insana Michael F. , Tapiovaara Markku
Published: October 2005

Although optimal decision functions for many simple detection/discrimination tasks can be cast in a form linear in the signal data, more complicated tasks require the addition of higher-order terms. This is typically the case when parameter uncertainty is allowed, in imaging for example, for the detection of a target of known size and shape but unknown position in a noise field. The simple task of detecting signals known exactly except for position, specifically detection of a ‘‘boxcar’’ shaped signal on a uniform data trace, has been studied in order to elucidate the relative importance of the first-, second-, or higher-order terms of the likelihood ratio decision rule. Analytical expressions have been developed to describe signal-to-noise ratios relevant for performance evaluation at low signal contrast levels, and computer simulations have been used to evaluate performance at higher contrast. It was found that for this task the first-order term (which corresponds to measuring the mean value of the data) dominates for low contrast signals but is superseded by higher-order terms (which to jth order correspond to the jth-order correlation of the data match filtered with the jth-order correlation of the signal) as contrast is increased. The quadratic term is found to be inferior to the linear term for small contrast and to the cubic for all values of signal contrast if the background is held constant. When the background level is allowed to vary, the performance of the odd-order terms decreases relative to that of the quadratic (and other even-order ones). Various measures of decision function efficiency are compared, demonstrating the severe limitations of using the simple signal-to-noise ratio (SNR) formalism for processes with non-Gaussian-distributed probability density functions. These results are valuable for guiding approaches to computational observers of signal data by showing the range of validity of suboptimal decision functions that are much easier to compute than the exact likelihood ratio solution.
Time-space domain incident angle compensation for ray inversion in an inhomogeneous medium
Authors: Tao Liang , Ma Xingrui , Huang Wenhu
Published: October 2005

In many acoustical ray inversion methods, if the wave ray is nonlinear in a random medium, the distribution of the incident angles of the discrete projections is uneven, and this brings forth the distortion in the inversion result. Moreover, the far-field condition is broken down while the inversion region is large. In order to overcome these drawbacks, a new t-x (time-space) domain backprojection method compensating the density of the distribution of incident angles is developed. This paper provides the theory of the incident angle compensation, discusses the efficiency with several point defect examples in the layered medium, and describes the ray tracing method for defect inversion in a layered medium. Finally, it presents a simulation inversion result of a crack defect.
Measuring the sound power of a moving source
Authors: Wei Wei , Hickling Robert
Published: October 2005

The sound power of a moving source was measured with a vector sound-intensity probe, for the simple case of an axisymmetric source moving along a known straight path. The probe tracks the position of the source and, at the same time, measures the component of intensity normal to a hypothetical measurement cylinder enclosing the source, the axis of the cylinder lying along the path of the source. The sound power of the axisymmetric source is determined by integrating sound intensity over the surface of the cylinder. The contributions of the ends of the cylinder can be neglected if the cylinder is long enough. The measured sound power of the moving source was compared with the sound power of the source, (a) estimated from the applied voltage and (b) measured with the source stationary, and it was found to be greater than (a) by 14% and greater than (b) by 18% or 0.7 dB. The difference is believed to occur because the source is not completely axisymmetric due to reflections in the tank. The method can be applied to a nonaxisymmetric source using a circular array of sound-intensity probes instead of a single probe.
Sound propagation through atmospheric turbulence: Multifractal phase fluctuations
Authors: Mellen Robert H. , Siling George
Published: October 2005

Phase fluctuations of sound propagating through turbulent air show frequency spectra following an F−β power law (β=const.) over several decades. This is consistent with a simple fractal description involving the dimension D=(5−β)/2. However, many similar natural phenomena have been shown to be multifractal. Universal multifractals are characterized by two additional parameters: The Lévy index 0≤α≤2 for the type of multifractal and the codimension 0≤C1≤1 for the intermittence. These parameters are a statistical measure of the nonlinear dynamics. Analysis of experimental data obtained at 5 kHz, range ≊4 m and wind speed ≊12 m/s is reported here and results indicate that phase fluctuations are ‘‘hard multifractal’’ (α≳1). The actual estimate is near the limiting value α=2, which is consistent with Kolmogorov’s lognormal model for turbulence.
Calculation of average turbulence effects on sound propagation based on the fast field program formulation
Authors: Raspet Richard , Wu Wenliang
Published: October 2005

Daigle has published a series of papers in which he has applied the turbulent scattering theories of Chernov and Karavainikov to sound propagation over hard and finite impedance grounds. In these papers, Daigle has introduced the decorrelation in phase and amplitude due to turbulence along the direct and reflected path into the spherical wave reflection analysis for a nonrefracting atmosphere. Here the phase and amplitude decorrelation terms have been incorporated into the evaluation of the spectral integral of a fast field program for propagation in a refracting atmosphere. Although the calculation involves two significant approximations, it reproduces Daigle’s results for homogenous atmospheres and compares well with the upward refraction measurement of Parkin and Scholes and with measurements taken under a variety of refractive conditions at Bondville, Illinois by the U.S. Army Construction Engineering Research Laboratory.
Causal theories and data for acoustic attenuation obeying a frequency power law
Authors: Szabo Thomas L.
Published: October 2005

This study compares causal theories, based on Kramers–Kronig relations, fractional calculus, and on those derived from new time domain causal relationships, to diverse data. All these theories are based on the assumptions that the functional form of the attenuation persists beyond the measurement range and that attenuation is much smaller than the wave number. The data, for lossy media with attenuation having a power-law frequency dependence with an exponent y, include cases for both liquids and solids, ranging from acoustic to ultrasound frequencies. Data are in closer correspondence with the new theory which predicts decreasing dispersion as the power exponent y approaches zero or an even integer. Experimental results and supporting evidence show that the classical case of frequency-squared attenuation is dispersionless. An approximate nearly local Kramers–Kronig theory is in agreement with the time causal theory when the exponent is close to one, but deviates for other values. The comprehensive time causal theory is shown to be equivalent to two other theories derived from exact Kramers–Kronig relations and from fractional calculus and it covers the y odd integer cases which are missing or incomplete in these approaches. Attenuation–dispersion relations are presented in two forms: one for a general frequency range and another for a finite range. It is demonstrated that complete velocity dispersion (within a signal bandwidth) can be predicted from knowledge of the attenuation data and velocity at a single frequency including the velocity at either zero frequency (y≳1) and or at a high-frequency limit (0<y<1). In addition, attenuation data can be predicted from velocity data.
Aeroacoustic measurements in wind tunnels using adaptive beamforming methods
Authors: Gramann Richard A. , Mocio James W.
Published: October 2005

Tests have been performed in a conventional low speed wind tunnel using a linear array of microphones to measure the received source level of a speaker projecting within the test section. Conventional, or delay and sum beamforming (CBF), and adaptive beamforming (ABF) have been employed to determine the source bearing and the received source level. Both narrow-band and broadband sources were used, with two different array configurations and several array orientations. The results show that ABF can be used in such an environment and that it rejects much of the multipath. Consequently more accurate broadband measurements are obtained with ABF than with CBF.
Identification of concurrent harmonic and inharmonic vowels: A test of the theory of harmonic cancellation and enhancement
Authors: de Cheveigné Alain , McAdams Stephen , Laroche Jean , Rosenberg Muriel
Published: October 2005

The improvement of identification accuracy of concurrent vowels with differences in fundamental frequency (ΔF0) is usually attributed to mechanisms that exploit harmonic structure. To decide whether identification is aided primarily by selecting the target vowel on the basis of its harmonic structure (‘‘harmonic enhancement’’) or removing the interfering vowel on the basis of its harmonic structure (‘‘harmonic cancellation’’), pairs of synthetic vowels, each of which was either harmonic or inharmonic, were presented to listeners for identification. Responses for each vowel were scored according to the vowel’s harmonicity and that of the vowel that accompanied it. For a given target, identification was better by about 3% for a harmonic ground unless the target was also harmonic with the same F0. This supports the cancellation hypothesis. Identification was worse for harmonic than for inharmonic targets by 3%–8%. This does not support the enhancement hypothesis. When both vowels were harmonic, identification was better by about 6% when the F0’s differed by 1/2 semitone, consistent with previous experiments. Results are interpreted in terms of harmonic enhancement and harmonic cancellation, and alternative explanations such as waveform interaction are considered.
Frequency glide discrimination in the F2 region by normal-hearing and hearing-impaired listeners
Authors: Summers Van , Leek Marjorie R.
Published: October 2005

The dynamic formant transitions present within consonant–vowel and vowel–consonant utterances may be poorly processed by hearing-impaired (HI) listeners and may, as a result, provide reduced segmental information to these listeners. Both the brief durations and rapid spectral change associated with these transitions have been proposed as contributing to these deficits in processing. To investigate HI listeners’ processing of transitional stimuli, six HI and six normal-hearing (NH) listeners were asked to discriminate between frequency glides patterned after second formant transitions in English CV syllables. The influences of glide duration, rate, and frequency extent were examined for each group in quiet and in broadband noise. Reductions in glide duration and the presence of noise each led to significant increases in frequency difference limens for glide onset. The magnitudes of these effects were similar across groups, thereby failing to show increased susceptibility to noise or greater deficits in dealing with brief stimuli on the part of HI listeners. Contrary to the expectation that HI listeners would show greatest deficits (relative to the NH group) for the most rapidly changing glides, the only significant group differences were observed for gradual glides of limited frequency extent. This latter finding is discussed in terms of sensitivity to ‘‘cochlear dispersion’’ cues [Porter et al., J. Acoust. Soc. Am. 90, 1298–1308 (1991)]. It is hypothesized that HI listeners may not process these cues as effectively as NH listeners, perhaps as a result of impaired frequency selectivity.
Time-domain simulation of sound production in the brass instrument
Authors: Adachi Seiji , Sato Masa-aki
Published: October 2005

Sound production in brass instruments is formulated physically with two different models of lip vibration: the ‘‘transverse’’ model, where lips strike laterally to the direction of the air flow, and the ‘‘swinging-door’’ model, where lips execute an outwardly striking motion. This formulation is used to carry out time-domain simulation, which indicates that self-excitation of the brass instrument is possible with both of these lip models. Changing the lip resonance frequency provides sustained oscillation at the first through eighth air column resonance modes, which correspond to the musical tones in the harmonic series played on the brass instrument without valve manipulation. Oscillation probably also occurred at higher modes, but that region was not investigated. The harmonic structure of the simulated sound varies according to the fundamental frequency and sound level, as is the case in the sound produced by actual brass instruments. Unusual regimes of oscillation are also obtained: the pedal tone, whose fundamental does not participate in its sound production, a tone an octave below the third mode, whose odd harmonics do not contribute to the regime of oscillation, and a multiphonic, which is an oscillation perceived as having two fundamentals simultaneously.
Upper lip, lower lip, and jaw peak velocity sequence during bilabial closures: No differences between stutterers and nonstutterers
Authors: Jäncke L. , Kaiser P. , Bauer A. , Kalveram K. Th.
Published: October 2005

In the present study, movement timing of upper lip (UL), lower lip (LL), and jaw (J) was investigated. Twelve nonstutterers and nineteen stutterers were asked to utter the testwords /papapas/ and /sapapple/ under different stress and speech rate conditions. Contrary to earlier reports suggesting an invariant UL–LL–J peak velocity sequence in normal speakers and a more variant pattern in stutterers, it was found that nonstutterers as well as stutterers failed to show an invariant peak velocity sequence for bilabial closure and that stutterers and nonstutterers exhibited almost the same distribution of peak velocity sequences. The present results reveal strong intra- and interindividual variability in peak velocity patterns, and lead to the conclusion that a deviation from the UL–LL–J peak velocity sequence is not an indicator of a disturbed speech motor control process.
Subjective evaluation of four low-complexity audio coding schemes
Authors: Joseph Stella M. , Maher Robert C.
Published: October 2005

In this study the subjective performance of four low-complexity audio data compression methods are compared, operating at nominal bit rates of 2, 3, 4, and 5 bits per sample, applied to four 20-kHz bandwidth, 16-bits per sample digitized musical signals. The simple compression schemes compared were elementary differential pulse-code modulation (DPCM), noise feedback coding DPCM (NFC-DPCM), adaptive quantizer DPCM (DPCM-AQB), and a recently proposed method known as recursively indexed quantizer DPCM (RIQ-DPCM). Pairs consisting of a reconstructed signal and a reference signal were presented in a two-interval preference experiment. The reference signals were processed for specified levels of modulated noise reference unit (MNRU) in order to estimate the equality threshold rating (ETR) of the reconstructed audio stimuli. The subjective MNRU values were found to increase by 2–5 dB for each increment in bits per sample. The DPCM-AQB scores were found to be 8–10 dB higher than for DPCM and NFC-DPCM. RIQ-DPCM was rated highest, exceeding the DPCM-AQB results by 2–5 dB in all tests. Objective measurements of segmental signal-to-noise ratio (SNRSEG) for the reconstructed signals predicted a performance level 2–5 dB lower than was actually found in the subjective results, particularly for SNRSEG values below 25 dB.
A qualitative study of mechanisms of jitter-induced shimmer in the voice
Authors: Wong Darrell , Lange Robert , Titze Ingo R. , Guo Chwen Geng
Published: October 2005

Measurements of jitter and shimmer are typically applied to microphone signals to discern the level of perturbations in the oscillatory behavior of the vocal folds. Shimmer, the average cycle-to-cycle change in amplitude, is known to linearly increase as the extent of amplitude modulation of tissue displacement increases. Behavior under frequency modulation (FM), however, is nonlinear. This nonlinearity is often attributed to time aliasing, the superposition of jittered impulse responses (assuming the source-filter model of phonation). As a consequence, whenever jitter is present, any measurement of shimmer cannot be solely attributed to amplitude modulation of the vocal fold tissue. The present study attempts to characterize other sources of FM-induced shimmer by examining points earlier in the voice production process. An interactive computer simulation of the vocal fold and vocal tract system is used under conditions of FM1/2 subharmonic modulation of the tissue displacement. It appears that, in addition to time aliasing, shimmer may be generated from FM-induced perturbations in mucosal wave propagation and tissue displacement. The paper qualitatively describes and illustrates these jitter-induced shimmer mechanisms.
Exit jet particle velocity in the in vivo canine laryngeal model
Authors: Bielamowicz Steven , Berke Gerald S. , Kreiman Jody , Gerratt Bruce R.
Published: October 2005

This study extends the previous work on exit jet particle velocity in an invivo canine laryngeal model of phonation [G. S. Berke etal., J. Voice 3, 306–313 (1989)]. In both the previous and the current study, a hot-wire anemometer was used to measure air particle velocity in the midline of the glottis at anterior, intermediate, and posterior positions. Simultaneous measurements of subglottal pressure, EGG, and PGG were also obtained. In the previous study, these measures were obtained with constant levels of recurrent laryngeal nerve (RLN) and superior laryngeal nerve (SLN) stimulation. In the current study, exit jet particle velocity profiles were obtained across multiple levels of RLN and SLN stimulation. Exit jet particle velocity was also measured at midline and off-midline positions with constant levels of RLN and SLN stimulation. The time-varying features of exit jet particle velocity as a function of subglottal pressure and glottal vibratory events will be presented.
Glottal characteristics of female speakers—acoustic, physiological, and perceptual correlates
Authors: Hanson Helen M.
Published: October 2005

A previous study of vowels produced by female speakers showed substantial individual differences in acoustic parameters related to glottal characteristics [K. N. Stevens and H. M. Hanson, in Vocal Fold Physiology: Voice Quality Control (Singular, San Diego, 1995)]. Based on measurements taken on the speech signal or spectrum, inferences were made about glottal configuration during phonation and the nature of the glottal pulse. Subjects fell into two groups based on the acoustic measurements, group 1, assumed to have abrupt glottal closure and group 2, assumed to have nonsimultaneous closure. Results of a listening test have shown that members of group 2 are perceived to be breathier than members of group 1 [H. M. Hanson, Proc. ICASSP-95 (in press)]. The current study extends the earlier work in several ways. Physiological measurements have been made for four subjects, including inversed filtered airflow recordings and glottal images obtained by fiberscopy. Also, listening tests using synthesized speech have been carried out to study the role of glottal characteristics in speaker discrimination, and the usefulness of the acoustic measures for guiding the synthesis of natural sounding speech. The physiological and perceptual data are found to be consistent with the earlier interpretations of the acoustic measures of glottal characteristics.
Bistatic scattering of underwater sound from a porous solid sphere: A comparison of theory and experiment
Authors: Pace Martin E. , Huskey Theodore W. L. , Baker Steven R. , Kargl Steven G. , Lim Raymond
Published: October 2005

Measurements were made of the bistatic scattering of underwater sound from a porous solid sphere. Two sample spheres were employed composed of bonded glass beads of 100- and 500-micron nominal grain diameter, respectively. The diameter of each sphere was approximately 6.8 cm. The scattering into the rearward hemisphere was measured over the frequency range 13 to 150 kHz, corresponding to values of ka from approximately 2 to 20. Over this frequency range the viscous penetration depth varies from approximately 5.0 to 1.5 microns, so that the water in the pores can move freely. The experimental results were compared to numerical computations based on a theoretical Biot model [S. G. Kargl and R. Lim, 1527–1550 (1993)]. The physical parameters required by the model were obtained by independent measurements on the sample spheres and on similar cylindrical samples. Reasonably good agreement was found between the experimental and theoretical results for the 100-micron sphere, especially at the lower frequencies, except for a consistent deficit in the measured backscatter. Agreement between the results for the 500-micron sphere was poor, probably due to sample inhomogeneity.
Scattering of a transient plane compression wave by a spherical inclusion in a Biot medium
Authors: Schantz Hans , Stern Morris , Beres Justin
Published: October 2005

The scattering of an arbitrary transient plane wave by a spherical inclusion in a Biot medium is modeled, by applying the single frequency, steady-state solution of Zimmerman and Stern [ 527–536 (1993)] to the discrete Fourier components of the transient signal, and assuming linear supersposition. The solution of Zimmerman and Stern is an analytical series solution. Its accuracy is mainly determined by computation errors and the convergence of the series. The incident pulse can be any combination of Biot fast and low waves. The theoretical results for certain cases are shown. They are also compared to experimental measurements. [Work supported by Naval Research Laboratory, Stennis Space Center.]
Multiple scattering from submerged bodies with dissimilar acoustical properties. Part I. Local impedance models
Authors: Turek Gabriella , Rogers Peter H. , Ferri Aldo A.
Published: October 2005

A numerical solution for a two-body acoustical multiple scattering problem based on the analytical infinite series solution of the wave equation was developed. FORTRAN 77 codes implementing this solution were written which are capable of simulating the case of two spheres of arbitrary radius and distinct material properties subject to an acoustic plane wave of arbitrary incidence. Far-field solutions involving permutations of the two ‘‘degenerate’’ boundary conditions (pressure release and rigid) were compared to solutions obtained with the combined Helmholtz integral equation formulation problem (CHIEF) program. Surface pressures and velocities were also calculated. [Work supported by ONR.]
Multiple scattering from submerged bodies with dissimilar acoustical properties. Part II. Experimental results
Authors: Turek Gabriella , Rogers Peter H. , Ferri Aldo A. , Caille Gary W.
Published: October 2005

In Part I [Turek etal.] a numerical solution for a two-body acoustical multiple scattering problem based on the analytical infinite series solution of the wave equation was presented. Surface and far-field solutions involv- ing permutations of the two ‘‘degenerate’’ boundary conditions (pressure release and rigid) were compared to solutions obtained with the combined Helmholtz integral equation formulation problem (CHIEF) program. In this paper the case in which one of the spheres is fully elastic and the other pressure release is modeled and the results verified experimentally.