bluuebunny/crossref_metadata_2025 huggingface dataset:
Comodulation masking release for suprathreshold signals.
Authors: Hall J. W. , Grose J. H.
Published: October 2005

Previous studies of comodulation masking release (CMR) have shown that the threshold of a signal masked by a narrow band of noise centered on the signal can be improved by the presence of energy remote from the signal frequency, provided that the amplitude envelope of the remote noise is correlated with the envelope of the noise centered on the signal frequency. The extent to which an advantage in comodulated noise may apply also to suprathreshold signals is currently being investigated. The present study deals specifically with the ability to detect changes in the intensity of a pure tone presented in a narrow band of noise, both as a function of the level of the standard, and whether comodulated flanking bands are present or not. Preliminary data indicate that the amount of CMR with increase in the level of the standard depends upon the basis of comparison between comodulated and uncorrelated noise conditions. Comparing equal SPL standards, advantage for comodulated noise persists until the standard in the comodulated case is about 10 to 15 dB above masked threshold; comparing equal SL standards, performance is generally better for the uncorrelated envelope case. Data on similar conditions will be presented for the masking-level difference paradigm. [Work supported by AFOSR.]
Estimating bottom slope from pulse duration.
Authors: McCammon D. F. , Burns T.
Published: October 2005

Employing the Fresnel and Kirchhoff approximations in the Helmholtz integral equation and assuming a Gaussian correlation function, an equation can be derived that predicts the time distribution of the acoustic pressure from a pulse propagated over a rough bottom. A simple expression can be found that relates the half duration time of the pulse to the surface rms slope, grazing angle, and slant range. Applying this expression to a measured time series from a rough Pacific thin sediment area, the computed rms slope is found to be larger than that estimated by spectral means. This increase in slope value can be thought of as an ‘‘effective’’ slope, that is, this computed slope was obtained using a first-order scattering theory, and the increase must therefore be including second-order scattering effects. The size of the increase leads to the conclusion that in thin sediment areas, second-order scattering effects such as multiple scattering, layering resonances, and shadowing must be as important as first-order scattering. [Work supported by ONR-AEAS Program.]
Empirical derivation of bathymetric resolution.
Authors: Goff John A.
Published: October 2005

Two properties can be used to define the accuracy of a bathymetric sonar system: (1) the system’s response to the seafloor, which determines lateral resolution, and (2) the system noise, or spurious addition of a high-wave-number component, which determines vertical resolution. The methodologies presented here attempt to quantitatively characterize these properties using only the bathymetric data, independent of theoretical predictions of system resolution. One method of analysis, useful for characterizing system response, is to compare co-registered data of differing quality, with the highest resolution data serving as the measure against which other systems are judged. Comparison techniques include the use of ruler measures, covariance functions, and power spectra that allow for the investigation of the size of features measured as a function of scale. Another method of analysis seeks to quantify noise characteristics by isolating the contribution of noise to the bathymetric autocovariance function. This yields both the rms noise height and the noise correlation distance, the former an estimate of the vertical resolution of the system and the latter providing information regarding the spatial/temporal persistence of noise spikes.
A comparison of methods for quantitative analysis of sonar imagery and bathymetry.
Authors: Reed Thomas B.
Published: October 2005

The usefulness of synoptic seafloor surveys has been limited in the past by the minimal extent to which the user can interact with the resulting survey data with any confidence. An interactive tool for co-registration and quantitative analysis of seafloor acoustic imagery and bathymetry is presented. The technique of stochastic back projection [W. K. Stewart, Proc. ASME Conf. on Off Shore Mechanics, Houston, TX (1988)] is used to produce mosaics of imagery and bathymetry. This application of a uniform mosaicking procedure allows the creation of data ‘‘layer cakes,’’ containing uniformly gridded, co-registered layers of all data available for a given location. This ‘‘layer cake’’ can then be accessed through a mouse-driven screen-interactive tool for selection and analysis of whatever information might be available in the grid. From gridded imagery one acquires a suite of first-order statistics (mean, variance, skewness, kurtosis, etc.), image histogram, image texture, and image fractal dimension. Raw side-scan data yield probability distribution functions (PDFs) indexed by slant range, incidence angle, slope, dip direction, and look direction. From bathymetry, slope statistics, variograms, and surface fractal dimension estimates are extracted. Given this partial or complete descriptive vector, classification maps are created of bottom type, capable of distinguishing to a first order lithologic differences seen in bottom photographs.
A theory for individual preference of designing the sound field in a concert hall.
Authors: Ando Yoichi
Published: October 2005

The scale value S [Y. Ando, ConcertHallAcoustics (Springer-Verlag, New York, 1985)], which is obtained by the law of comparative judgment and confirmed by the test of goodness of fit, may be inversely transformed into the original probability P(B≳A). Consider first of all the simplest case consisting of only two kinds of sound fields A and B in a concert hall, and if S=−1.0, then P(B≳A)=0.84 and P(B<A)=0.16. This means that 84% of listeners judge that sound field B is preferred over A, and 16% of listeners judge A as more preferred. For the purpose of obtaining preferred conditions for different listeners, such a relationship should be satisfied by the number of seats. In order to determine the number of seats in reference to that of the most preferred condition, for the majority of listeners, probability index (PI) is defined by PI=P(B<A)/P(B≳A), 0≤PI≤1.0. If P(B≳A)=0.5, then PI=1.0, which implies the most preferred condition. After construction of the concert hall, a seat selection system for each listener is used to enhance the listener’s satisfaction.
Normal-mode matching localization in shallow water: Environmental and system effects
Authors: Jesus S. M.
Published: October 2005

Matched-field processing is a passive range and depth source localization technique that has been extensively used in shallow-water environments. A vertical array of sensors is used to spatially sample the acoustic waveguide where the source signal embedded in additive ambient noise propagates. The array output is then matched with the signal replica field generated by a normal-mode model based on the environmental parameters that characterize the waveguide. Recent results obtained from real data show the feasibility of the technique and give evidence of its strong dependence both on the array aperture and on the knowledge of the environmental parameters used in the model. This paper describes a modified matched-field technique, called normal-mode matching, that is applied to real shallow-water data. Its performance is compared to that obtained by conventional matched-field processing using the same data set. Unlike conventional matched-field processing, the results indicate that unambiguous localizations can be obtained even for ‘‘short’’ arrays spanning only half of the water column.
Resonant interaction of sound wave with internal solitons in the coastal zone
Authors: Zhou Ji-xun , Zhang Xue-zhen , Rogers Peter H.
Published: October 2005

Naturally occurring internal solitary wave trains (solitons) have often been observed in the coastal zone, but no reported measurements of such solitary waves include low-frequency long-range sound propagation data. In this paper, the possibility that internal waves are responsible for the anomalous frequency response of shallow-water sound propagation observed in the summer is investigated. The observed transmission loss is strongly time dependent, anisotropic and sometimes exhibits an abnormally large attenuation over some frequency range. The parabolic equation (PE) model is used to numerically simulate the effect of internal wave packets on low-frequency sound propagation in shallow water when there is a strong thermocline. It is found that acoustic transmission loss is sensitive to the signal frequency and is a ‘‘resonancelike’’ function of the soliton wavelength and packet length. The strong interaction between acoustic waves and internal waves, together with the known characteristics of internal waves in the coastal zone, provides a plausible explanation for the observed anomalous sound propagation in the summer. By decomposing the acoustic field obtained from the PE code into normal modes, it is shown that the abnormally large transmission attenuation is caused by ‘‘acoustic mode-coupling’’ loss due to the interaction with the internal waves. It is also shown that the ‘‘resonancelike’’ behavior of transmission loss predicted by the PE analysis is consistent with mode coupling theory. As an inverse problem, low-frequency acoustic measurements could be a potential tool for remote-sensing of internal wave activity in the coastal zone.
Sound scattering from a particle-laden, turbulent jet
Authors: Hay Alex E.
Published: October 2005

Multifrequency acoustic scattering experiments were carried out in the laboratory using a free, turbulent water jet carrying solid particles in suspension. A crossed-beam geometry was used, in which the axis of the jet was perpendicular, or nearly so, to the direction of the incident sound. The suspended particles were either natural sand grains or lead-glass beads, 100–500 μm in diameter. The results, based on measurements made simultaneously at 1, 2.25, and 5 MHz, include backscatter and attenuation as a function of suspended sediment concentration, measurements of the total scattering and backscattering cross sections of natural sand grains and glass beads as a function of frequency and particle size, and two-point correlation measurements of the fluctuations in apparent suspended sediment concentration. The lead-glass bead cross sections exhibit both the resonance and diffraction extrema expected of solid spherical scatterers; the sand cross sections do not and, for acoustic wavelengths comparable to or less than the particle circumference, are larger than spherical scatterer theory would predict. The two-point correlation estimates of jet velocity and measurements of the time-averaged jet width as a function of particle size are related to the mean and turbulent structure of two-phase jets and illustrate the potential of acoustic methods for noninvasive investigations of two-phase turbulent flow.
A neural network approach to source localization
Authors: Steinberg Ben Zion , Beran Mark J. , Chin Steven H. , Howard James H.
Published: October 2005

The use of neural network techniques to localize an acoustic point source in a homogeneous medium is demonstrated. The input data are the cosines of the phase difference measurements at an array with N detectors. Only the most fundamental types of neural network systems will be considered. Use will be made of linear and sigmoid-type neurons in a single-layer network. The performance of the single-layer network is very satisfactory for a wide range of configuration parameters if the resolution and sampling conditions are satisfied. Once the parameters of the neural network are determined, the computational effort to determine a new source location is minimal. However, when a source/detector configuration is considered that does not satisfy the resolution and sampling conditions, the single-layer network will not consistently perform well.
Transition to chaos in acoustically driven flows
Authors: Thompson C. , Mulpur A. , Mehta V. , Chandra K.
Published: October 2005

In this paper, a model describing the process of transition to chaotic fluid motion in an acoustically driven fluid is presented. The nonlinear interaction between the Stokes boundary layer and linearly unstable three-dimensional vortical disturbances is examined. Special consideration is given to the amplitude range above which these disturbances bifurcate from linear stability. It is found that oscillatory modulation present in the basic-flow results in successive period-doubling bifurcations of the three-dimensional vortical disturbances. It is shown that these bifurcations result in the disturbance amplitude becoming chaotic.
Complex resonance frequencies in acoustic-wave scattering from impenetrable spheres and elongated objects
Authors: Bao X. L. , Schumacher C. R. , Überall Herbert
Published: October 2005

The complex resonance frequencies of impenetrable (rigid or soft) elongated objects, namely, spheroids and cylinders with hemispherical end caps, including the spherical limit of the latter are studied. Complex resonance frequencies are obtained from the principle of phase matching of surface waves. For the case where such surface waves are generated by plane acoustic waves at broadside incidence, the simultaneous presence of cylindrical circumferential-wave resonances and of the resonances of meridionally propagating surface waves is discussed.
Designing a negligible specular reflection coefficient for a panel with a compliant layer
Authors: Maidanik G. , Dickey J.
Published: October 2005

The specular reflection coefficient of a basic boundary that possesses surface impedance that is mass controlled can be rendered negligible by cladding it with a compliant layer. In this rendering the surface stiffness of the compliant layer and the surface mass of the basic boundary form a resonant dynamic system. The negligible specular reflection coefficient is obtained when the ratio of the surface impedance of the basic boundary and that of the fluid bears, at the resonance frequency and at a specific incidence angle, a direct relationship to the sum of the loss factors in the basic boundary and the compliant layer. A relationship is then derived between the surface stiffness of the compliant layer and its loss factor. This relationship must be necessarily satisfied if a vanishing specular reflection coefficient is to be achieved. The relationship is exemplified by a primitive boundary that is composed of a panel and a compliant layer. Examples relating to this primitive boundary are computed and displayed.
On the normal modes of free vibration of inhomogeneous and anisotropic elastic objects
Authors: Visscher William M. , Migliori Albert , Bell Thomas M. , Reinert Robert A.
Published: October 2005

The Hamilton’s principle approach to the calculation of vibrational modes of elastic objects with free boundaries is exploited to compute the resonance frequencies of a variety of anisotropic elastic objects, including spheres, hemispheres, spheroids, ellipsoids, cylinders, eggs, shells, bells, sandwiches, parallelepipeds, cones, pyramids, prisms, tetrahedra, octahedra, and potatoes. The paramount feature of this calculation, which distinguishes it from previous ones, is the choice of products of powers of the Cartesian coordinates as a basis for expansion of the displacement in a truncated complete set, enabling one to analytically evaluate the required matrix elements for these systems. Because these basis functions are products of powers of x, y, and z, this scheme is called the xyz algorithm. The xyz algorithm allows a general anisotropic elastic tensor with any position dependence and any shape with arbitrary density variation. A number of plots of resonance spectra of families of elastic objects are displayed as functions of relevant parameters, and, to illustrate the versatility of the method, the measured resonant frequencies of a precision machined but irregularly shaped sample of aluminum (called a potato) are compared with its computed normal modes. Applications to materials science and to seismology are mentioned.
Measurement of the characteristic impedance and propagation constant of materials having high flow resistivity
Authors: Champoux Yvan , Stinson Michael R.
Published: October 2005

A technique for the measurement of characteristic acoustical impedance and propagation constant of porous materials is presented. Samples are mounted in an impedance tube and both the surface impedance and a transfer function along the sample length are determined; characteristic impedance and propagation constant may be calculated using these quantities. For this implementation, a classical standing wave procedure is used for the determination of surface impedance. Measurements are obtained for frequencies between 100 and 4000 Hz. A special procedure that makes use of extension tubes, between sample and the fixed part of the impedance tube, is used to achieve the low-frequency results. The new technique yields results that are comparable in accuracy to the ‘‘two-cavity’’ technique described by Utsuno et al. [J. Acoust. Soc. Am. 86, 637–643 (1989)] for samples of low flow resistivity (17.2 and 43.6 cgs-rayl cm−1 ), but substantially better for a sample of higher flow resistivity (380 cgs-rayl cm−1 ).
Natural frequencies of Timoshenko beams elastically restrained against translation and rotation at one end
Authors: Laura P. A. A. , Bellés P. M. , Rossi R. E. , Maurizi M. J.
Published: October 2005

An exact solution for the title problem is obtained. The lower five natural frequencies of transverse vibration are tabulated as a function of the mechanical parameters coming into play.
Acoustical nondestructive evaluation of heterogeneous materials in the multiple scattering regime
Authors: Feng Shechao , Sornette Didier
Published: October 2005

Multiple scattering blurs the distinction between different material systems beyond a certain distance from the observation point, thereby rendering most random systems cloudy in appearance and opaque in the sense of structure delineation. However, based on a theoretical analysis, it will be shown that, due to the phase coherent nature of wave propagation through random media, some remnant information is still present which can be used to detect and locate new growing cracks. This offers the possibility to extend acoustic nondestructive evaluation techniques in the realm of highly heterogeneous media, such as composites or concrete analyzed by high-frequency sound waves.
An ultrasonic method to measure human plasma coagulation time
Authors: Machado J. C. , Lenzi A. , Silva W. G. , Sigelmann R. A.
Published: October 2005

An ultrasonic method to measure coagulation time for prothrombin time (PT) is discussed. This method is based on the measurement of ultrasonic scattering from spherical glass particles of 200-μm diameter kept in motion, inside of a holder containing 0.1 ml of plasma, by ultrasonic energy. The incident wave (2.7 MHz) not only keeps the particle in motion but also is the source for the scattered waves. A receiving transducer captures part of the scattered wave and generates at its electrical output a signal containing amplitude and phase fluctuations. The motion of the particles are strongly influenced by the rheological changes during the process of coagulation. When the clot is formed, the amplitude of the motion of these particles is significantly reduced and so the fluctuations on the received signal stop. The time from the start of the coagulation process until the end of the fluctuations at the received signal is the coagulation time. Experimental results demonstrate that the ultrasonic method has precision and accuracy compatible to those provided by the manual tilt-tube method when PT is measured with normal and abnormal samples of human plasma.
On the combined use of accented and unaccented diphones in speech synthesis
Authors: Drullman Rob , Collier René
Published: October 2005

In this paper, three experiments are reported that were run in order to assess the quality of Dutch synthetic speech using accented and unaccented diphones, i.e., diphones extracted from accented and unaccented syllables, respectively. In a paired-comparison design, subjects were asked to evaluate the naturalness and fluency of different versions of an utterance. The results of the first two experiments, in which isolated polysyllabic words were used, indicate that the use of accented or unaccented diphones has a perceptual effect on phonologically long vowels only. In a third experiment, the use of the different diphone types in short sentences with a fixed temporal structure was evaluated. Results suggest that using unaccented diphones in unaccented or secondarily accented syllables does not result systematically in more natural-sounding speech.
McGurk effect in non-English listeners: Few visual effects for Japanese subjects hearing Japanese syllables of high auditory intelligibility
Authors: Sekiyama Kaoru , Tohkura Yoh’ichi
Published: October 2005

The McGurk effect is a phenomenon that demonstrates a perceptual fusion between auditory and visual (lip-read) information in speech perception under the condition of audio-visual discrepancy, created by dubbed video tapes. This paper investigated whether or not the McGurk effect could be extended to Japanese subjects listening to Japanese syllables of different auditory intelligibility. The audio and video signal of a female talker’s speech for ten Japanese syllables (/ba/, /pa/, /ma/, /wa/, /da/, /ta/, /na/, /ra/, /ga/, /ka/) were combined on videotapes, giving 100 audio-visual stimuli. These stimuli were presented to ten Japanese subjects who were required to identify the stimuli as heard speech in both noise-added and noise-free conditions. For both conditions, the intelligibility of the auditory stimuli was measured, by presenting the audio-alone stimuli. The results showed that, in the noise-free condition, the McGurk effect was small and almost limited to auditory stimuli of which the intelligibility was less than 100%. In the noise-added condition, the McGurk effect was very strong and widespread. These results indicate that the ‘‘Japanese McGurk effect’’ is less easily induced than the English one, and that it depends on the auditory intelligibility of the speech signal.
Combination of binaural information across frequency bands
Authors: Buell Thomas N. , Hafter Ervin R.
Published: October 2005

Perceptual grouping of the frequency components from a source into a single auditory object is needed when localizing a complex sound in an environment where other sounds are also present. Two acoustic regularities that might allow for such grouping are a harmonic relation among the components and a commonality of their spatial positions. The utility of these cues was examined in a forced choice psychophysical task by measuring sensitivity to interaural differences of time (IDT) for low-frequency stimuli presented via earphones. In the first experiment, stimuli were composed of either one, two, or three frequencies. A signal detection analysis used to predict the effects of combining information across frequencies found summation to be optimal, regardless of the harmonicity of the complex. A second experiment presented two-frequency complexes in which one tone, the target, contained the IDT to be detected while the other, the distractor, was constant across all three intervals of the forced choice. For inharmonic complexes, performance for the target–distractor combinations was equivalent to that found for targets presented alone, suggesting segregation of the targets and distractors into separate auditory objects. However, for harmonic target–distractor combinations, performance was diminished. A signal detection analysis of these data supports the idea that for purposes of lateralization, the interaural information in the targets and distractors was combined into a variance-weighted value, even though it meant a lowering of performance. Thus it seems that for the grouping of complex acoustic stimuli in space, harmonic structure is more important than commonality of spatial position.
Models of the effects of threshold on loudness growth and summation
Authors: Humes Larry E. , Jesteadt Walt
Published: October 2005

The present paper extends previous efforts to compare models of additivity of masking in normal and impaired listeners to measures of loudness. A model that provides a good account of additivity of masking for normal and impaired listeners, the modified power-law model with compressed internal noise, also provides a good description of basic loudness data from normal and impaired listeners. This model has been discussed frequently in the literature on loudness as one means of correcting loudness functions near threshold, but has not been widely accepted. The applicability of this model to loudness growth and the summation of loudness, both monaurally and binaurally, is evaluated and compared to the more generally accepted alternative. The ability of the model reported here to account for growth of loudness near threshold, as well as the additivity of masking, suggests a need to reconsider its application to loudness data, as well as a need to reconsider the relation between loudness and masking.
Intensity coding in low-frequency auditory-nerve fibers of the guinea pig
Authors: Winter Ian M. , Palmer Alan R.
Published: October 2005

Rate-level functions from 130 auditory-nerve fibers with characteristic frequencies below 3.5 kHz have been recorded. The relationship between rate-level function type and other properties of auditory-nerve fibers was similar to that previously reported for a high-frequency population in the same species [characteristic frequencies>8 kHz—Winter et al., Hear. Res. 45, 191–202 (1990)]. To estimate whether there is sufficient information in the changes in discharge rate from auditory-nerve fibers to account for the intensity discrimination performance observed in humans (for 1-kHz tone bursts), the Sachs–Abbas model was modified to produce the variation in rate-level functions found in guinea pig auditory-nerve fibers. The ability of modeled, single auditory-nerve fibers and populations of these fibers to signal differences in intensity has been calculated. Optimal combination of information from those fibers assumed to synapse beneath just one inner hair cell resulted in a discrimination performance that exceeded human psychophysical performance up to sound levels of 113 dB SL. It is concluded from these results that there is more than sufficient information present in the changes in discharge rate of a localized population of guinea pig auditory-nerve fibers to account for the intensity discrimination performance of humans as measured psychophysically.
Periodic signals with minimal power fluctuations
Authors: Hartmann William Morris , Pumplin Jon
Published: October 2005

In this article, Pumplin’s algorithm [J. Pumplin, J. Acoust. Soc. Am. 78, 100–104 (1985)] is used to find periodic waveforms with minimal power fluctuations. Starting with a particular power spectrum, the algorithm can find a set of phases for the harmonics such that the variance in waveform power is a minimum or near a minimum. Such optimized waveforms are smooth and tend to have very small crest factors. The particular power spectra chosen for study include narrow- and wideband spectra, with emphasis given to signals that are useful in research in psychoacoustics and in physiological acoustics.
Dynamics of an ultrasonic bonding tool: A case study in p-version finite-element analysis
Authors: Morris Rael B. , Carnevali Paolo , Bandy William T.
Published: October 2005

A recently developed p-version finite-element program [Bagus et al., IBM Res. Div., Res. Rep., RJ 7733 (71598), October 1990; Carnevali et al., in preparation] was used to simulate the dynamic behavior of an ultrasonic bonding tool. The accuracy of the p-code was exploited to resolve high-order modes near to the ultrasonic operating frequency (approximately 60 kHz). In particular, an undesired high-order bending mode was found to occur at a frequency very close to the axial mode that facilitates the bonding process. An optimal operating frequency that minimizes the excitation of the deleterious mode could be determined. Frequency response simulations and experiments were performed to validate this assertion. Their nature, and the accuracy required to resolve these high-order modes, would have made this analysis extremely difficult with other finite-element tools.
Measurements of ultrasonic pulse arrival time differences produced by abdominal wall specimens
Authors: Sumino Yoichi , Waag Robert C.
Published: October 2005

The influence of propagation medium inhomogeneities on pulsatile ultrasonic fields has been investigated experimentally. The study employed a special curved transducer to produce a hemispherical wave pulse and a linear array to measure the resulting field along a line in a plane. Translation of the array in the elevation direction yielded data over a two-dimensional aperture. Time delay across the aperture was calculated by adding delay differences obtained by cross-correlating signals on adjacent elements and noting the position of the cross-correlation peaks. Received waveforms were shifted an amount given by the difference between the actual arrival time and a calculated geometric delay to isolate arrival time differences due to propagation path inhomogeneities. Waveform and time delay difference plots as well as histograms and statistics derived from them for propagation through a water path and for propagation through five specimens of human abdominal wall indicate that arrival time fluctuations in the presence of human abdominal wall specimens are significantly greater than for a water path and that degradation in focusing through human abdominal wall can be expected in ultrasonic imaging systems that operate in the low megahertz range and employ a relatively large aperture.
Intrinsic echolocation capability of Hector’s dolphin, C
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Authors: Thorpe C. William , Bates Richard H. T. , Dawson Stephen M.
Published: October 2005

A sonar system’s echolocation capabilities can be inferred from the ambiguity distribution (defined here in terms of the conventional signal response function) of each of its transmitted signals. Several records of sounds emitted by Hector’s dolphin are analyzed. The computed ambiguity distributions indicate that the sonar clicks of Hector’s dolphins should be capable of resolving the ranges of targets as close together as 2 cm apart, but that target velocities cannot be resolved to any useful degree from a single echo.
On the perceptual limits of octave harmony and their origin
Authors: Demany Laurent , Semal Catherine , Carlyon Robert P.
Published: October 2005

Three subjects were monaurally presented with dyads of simultaneous, frequency modulated, sine tones approximately 1 oct apart. The tones, with carrier frequencies FL and FH, were presented in a background of pink noise and at a low sensation level, so that they were completely resolvable by the subjects’ peripheral auditory filters. In two experiments, subjects had to judge on each trial which of two dyads was inharmonic (FH≠2FL); the relative mistuning of the inharmonic dyad [(FH−2FL)/2FL] was varied independently of FL and could be either positive or negative; FL was fixed within trials in one experiment, and varied within trials (from about 8%–20%) in the other experiment. In both experiments, performance monotonically worsened as FL increased from 300–2000 Hz; in addition, negative mistunings were more often identified as inharmonicities than positive mistunings. In another experiment, a 4I-2AFC procedure was used to assess the detectability of changes in FH, irrespective of their effect on the perception of harmonicity. Compared to the other two experiments, performance was not the same function of FL, and was much better at high FL. Thus it is concluded that the detection of inharmonicity was limited by factors other than those responsible for fine pitch discriminations. Our results also have implications with respect to the origin of human listeners’ melodic octave templates.
Perception of acoustic source characteristics: Walking sounds
Authors: Li Xiaofeng , Logan Robert J. , Pastore Richard E.
Published: October 2005

The current study investigated the ability of subjects to perceive source characteristics (the gender of a human walker) of a naturally occurring auditory event (human walking). A number of acoustic properties were measured and subjected to statistical analyses in order to identify those properties that differentiate male and female walking footsteps. A principal component analysis on the statistical properties of the spectral energy distributions then identified two classes of information that were important in determining subject perception of the gender of a walker: (1) the spectral peak which integrates the information about the spectral central tendency of frequency and shape of the spectral peak; and (2) the contribution of high-frequency spectral components. A follow-up experiment then manipulated these spectral properties to verify their contributions in the perceptual classification of walker gender. Additionally, the effect of shoe on the gender judgement in walking sequences was assessed by having both male and female walkers wear male’s shoes.
Reverberation and attenuation in a pine forest
Authors: Huisman Willibrord H. T. , Attenborough Keith
Published: October 2005

Measurements of reverberation and attenuation as a function of frequency have been made in a pine forest at ranges from 10–100 m, paying particular attention to diurnal variation in meteorological conditions and effects associated with receiver location. Up to 1 kHz, the measured excess attenuation is modeled tolerably well by a conventional point source calculation using a two-parameter ground impedance model. It is found that the observed variations in meteorological profiles do not produce significant changes in the measured 100-m attenuation at any frequency. It is proposed that high-frequency attenuation and reverberation for ray paths below the foliage canopy are dominated by multiple scattering among the tree trunks. This is modeled numerically by a stochastic particle bounce procedure. The results of calculations indicate the relative importance of multiple scattering in reverberation and attenuation. However, the model is unable to verify the strong height dependence shown by the measured attenuation. The results suggest an interaction between ground effect and trunk scattering that is more complicated than simple addition as proposed hitherto. It is shown that the measured attenuation is considerably underpredicted by the Dutch–Scandinavian noise prediction scheme. The A-weighted imission level of road traffic noise transmitted through 100-m woodland of this type is significantly lower than that transmitted over 100-m pasture.
A numerical method for general finite amplitude wave propagation in two dimensions and its application to spark pulses
Authors: Sparrow Victor W. , Raspet Richard
Published: October 2005

The general equations of finite amplitude acoustics, including classical absorption effects and second-order nonlinear effects, are written in a form suitable for two-dimensional numerical solution. A finite difference scheme then is applied to numerically solve the equations. To demonstrate the method, examples are given of spherical free-field propagation, normal plane reflection from a hard surface, and oblique spherical reflection from a hard surface for spark pulses. This method has an advantage over Burgers’ equation methods, one-way wave equation methods, and Pestorius type algorithms in that it can predict the interaction of multiple finite amplitude acoustic waves at arbitrary propagation angles.
The van Cittert–Zernike theorem in pulse echo measurements
Authors: Mallart Raoul , Fink Mathias
Published: October 2005

A classical theorem of statistical optics, the van Cittert–Zernike theorem, is generalized to pulse echo ultrasound. This theorem fully describes the second-order statistics of the spatial fluctuations (the spatial covariance) of the field produced by an incoherent source. As a random scattering medium is insonified, it behaves as an incoherent source. The van Cittert–Zernike theorem can thus predict the spatial covariance of the pressure field backscattered by a random medium. It is shown that this spatial covariance and the incident energy diagram are Fourier pairs. In the case of a focused illumination, the spatial covariance of the backscattered pressure field is proportional to the autocorrelation of the transmitting aperture function. This is independent of frequency and of F/ number. Experimental results obtained with a linear array are in good agreement with theoretical expectations. The implications of this theorem in speckle reduction and in focusing in nonhomogenous media are discussed.
Increased accuracy in the application of the Sommerfeld–Watson transformation to acoustic scattering from cylindrical shells
Authors: Rumerman M. L.
Published: October 2005

The Sommerfeld–Watson transformation (SWT), when applied to problems of sound scattering from elastic bodies with separable geometries, allows the scattered field to be displayed in terms of waves rather than in terms of modes, and so gives a more meaningful picture of the scattering mechanisms at moderate and high frequencies. As typically applied, however, the SWT has left a discontinuity in the calculated field as a function of field point. This discontinuity is not inherent in the method, but is a result of not accounting for the effects of nearby poles in the evaluation of the line integral which represents the geometric part of the scattered field (essentially the specular term). This paper considers this effect in the particular case of broadside scattering from an infinite circular cylindrical elastic shell in an acoustic medium. The scattered field in the backward half-space, as computed from the corrected wave solution, is shown to be in excellent agreement with the field calculated from the normal mode (partial wave) series for frequencies corresponding to ka=1.5 and above, for a steel shell whose wall thickness is one percent of its radius. Shell theory, rather than the theory of elasticity, is used.
Plane-wave reflection from a random fluid half-space
Authors: Tang Dajun , Frisk George V.
Published: October 2005

The reflection of a monochromatic plane wave impinging from a homogeneous fluid half-space onto a random fluid half-space is studied using an integrodifferential equation method. The coherent reflection coefficient is presented as a function of frequency and statistical parameters characterizing the random medium.
Attenuation and speed of antiplane waves in a cracked solid using the Kramers–Kronig relations
Authors: Angel Y. C. , Achenbach J. D.
Published: October 2005

The propagation of antiplane waves in an unbounded linearly elastic solid that contains a distribution of flat cracks is considered. The cracks are parallel to each other, the distribution is dilute, and the incident wave is normal to the planes of the cracks. Using the Kramers–Kronig relations, the speed c of the coherent wave in the cracked solid is derived as a function of the dimensionless frequency ωa/cT (where ω is the angular frequency, a is the half crack width, and cT is the speed of antiplane waves in an uncracked solid) and of crack density. Numerical results for the speed c are obtained, based on the assumption that the limit of c for high frequencies is equal to cT. These results show that the speed of the coherent wave in a cracked solid is always less than the limiting speed at high frequencies. The results of this work are valid for the entire range of frequencies.
A wave vector, time-domain method of forward projecting time-dependent pressure fields
Authors: Forbes M. , Letcher S. , Stepanishen P.
Published: October 2005

A wave vector, time-domain (k−t) method of forward projecting time-dependent pressure fields from complex vibrators is developed using space-time Fourier transform methods. Axisymmetric fields are included as a special case of the general formulation in which a pressure field at one plane can be forward projected to other planes. In brief, a wave vector, time-domain representation of the field at one plane is forward projected via a temporal convolution with a wave vector, time-domain impulse response that is dependent on the projection distance. The projected field is then obtained via the use of an inverse spatial Fourier transform. A numerical study of the method illustrates the accuracy of the approach when implemented using fast Fourier transform (FFT) algorithms. The forward projections of simulated pressure fields from a planar ultrasonic transducer are shown to be in excellent agreement with corresponding results from the use of a time-domain impulse response method.
Active control of noise transmission through rectangular plates using multiple piezoelectric or point force actuators
Authors: Wang Bor-Tsuen , Fuller Chris R. , Dimitriadis Emilios K.
Published: October 2005

This paper analytically demonstrates the use of multiple piezoelectric actuators bonded to the surface and point force actuators applied directly to a plate to reduce sound transmission through the plate. A harmonic plane wave incident on a simply supported, thin rectangular plate mounted in an infinite baffle was considered as the primary source. Both multiple piezoelectric and point force actuators are separately used as secondary (control) sources to attenuate the sound transmission through the plate. An optimal process was applied to obtain the input voltages of the piezoelectric actuators and the magnitude of the point forces, so that the radiated acoustic power can be minimized. Results show that a reduction of sound transmission through the plate is successfully achieved, if the proper size, number, and position of the piezoelectric or point force actuators are selected. Additionally, a comparison showed that point force actuators provide more effective control of the sound transmission than piezoelectric actuators; however, piezoelectric patches have more practical implementation than point force shakers, because of their low cost and light weight.
Three-dimensional angular distributions of acoustic scattering from flexural and Rayleigh resonances of elastic spheroidal targets
Authors: George Jacob , Werby M. F.
Published: October 2005

Three-dimensional angular distributions of acoustic scattering strength arising from flexural and Rayleigh resonances of a prolate steel spheroid are presented. Flexural resonances are found to produce strong scattering into four almost symmetrical lobes, by as much as 20 dB above the nonresonant background. Rayleigh resonances are weaker, but significant portions of the scattered Rayleigh energy are radiated into steep angles. In both cases, considerable interactions of the scattered energy with waveguide boundaries may be expected.
Equations for estimating sound velocity and velocity ratio of marine sediments: Brazil Basin (NW South Atlantic)
Authors: Orsi Thomas H.
Published: October 2005

This letter presents regression equations for determining sound velocity in marine sediments of the Brazil Basin (NW South Atlantic). These equations are a revision of an earlier work by Orsi and Dunn [J. Acoust. Soc. Am. 88, 1536–1542 (1990)], where in situ velocities were used to examine selected empirical relationships. In this letter, sediment sound velocities have been corrected to standard laboratory conditions to recompute the equations, as well as several other statistical characteristics. Additional new relationships have been derived that permit calculation of velocity ratio. The relationships between properties and their statistical significance remain unchanged, and the reader is referred to the original study for detailed discussion.
Acoustic microcavitation: Its active and passive acoustic detection
Authors: Madanshetty Sameer I. , Roy Ronald A. , Apfel Robert E.
Published: October 2005

In this work acoustic microcavitation in water is studied primarily at 0.75 MHz and 1% duty cycle. To detect cavitation, two kinds of acoustic detectors are used. The first one is an unfocused, untuned 1-MHz receiver transducer that serves as a passive detector. The other one is a focused 30-MHz transducer that is used in pulse-echo mode and is called the active detector. Cavitation itself is brought about by a focused PZT-8 crystal driven in pulse mode. The active detector is arranged confocally with respect to the cavitation transducer. Both the interrogating pulse and the cavitation pulse arrive simultaneously at the common focus, which is the region of cavitation. With the test chamber filled with clean water, no cavitation is observed, even when the cavitation transducer is driven to give its peak output of 22 bar peak negative. Cavitation is, however, observed when polystyrene microparticles are added to the host water. Our view of how these smooth, spherical, monodispersed microparticles give rise to cavitation is described with some estimates. An attempt has been made to understand whether the presence of ‘‘streaming’’ affects the thresholds, and it has been found that the active detector field affects the cavitation process.
Application of the method of moments to acoustic scattering from arbitrary shaped rigid bodies coated with lossless, shearless materials of arbitrary thickness
Authors: Rao Sadasiva M. , Sridhara B. S.
Published: October 2005

The method presented in this paper provides a computational technique for solving acoustic scattering problems associated with arbitrary shaped three-dimensional rigid bodies coated with absorbing material of arbitrary thickness. The coating materials are assumed to be lossless and the shear speeds have been ignored. In particular, using the potential theory along with associated boundary conditions at the interfaces, a set of coupled integral equations is derived. The equations are then solved by approximating the scatterer geometry by planar triangular patches and employing the method of moments. For comparison purposes, the exact solution for a rigid sphere coated with an absorbing material is also derived using the eigenfunction expansion method. The numerical and exact solutions are compared and found to agree very well. Further, numerical results are also presented for other canonical shapes such as a thick disk and a cube. The method presented in this work is simple, efficient, and easily applicable to a variety of geometrical shapes.
Multipole acoustic waveforms in nonaxisymmetric boreholes and formations
Authors: Randall C. J.
Published: October 2005

Using a 2.5-dimensional velocity-stress finite-difference (vs-fd) technique, waveforms are calculated for multipole excitation of azimuthally nonsymmetric boreholes and formations. Axial uniformity of the borehole cross section and formation is assumed. The vs-fd waveforms agree with previous transform methods for circular boreholes, and the modes found for elliptical boreholes agree with those derived by a boundary integral technique. Borehole ellipticity substantially reduces monopole compressional headwave amplitudes in fast formations. Low-frequency dipole waveforms in elliptical boreholes show marked sensitivity to source dipole orientation in fast formations, but small sensitivity in slow formations. Waveforms from dipole receivers perpendicular to the source dipole may be comparable in amplitude to those recorded by parallel dipole receivers. Dipole waveforms from an exaggerated ‘‘keyhole’’-shaped borehole are quite similar to those from an elliptical borehole of similar aspect ratio in a slow formation. Finally, the behavior of early compressional headwaves arising from a nearby faster bed parallel to the borehole axis is qualitatively similar to that for a point source above a simple planar interface.