bluuebunny/crossref_metadata_2025 huggingface dataset:
Sound scattering by resonantly excited, fluid-loaded, elastic spherical shells
Authors: Gaunaurd G. C. , Werby M. F.
Published: October 2005

The scattering of sound waves by an air-filled, elastic, spherical shell in deep waters, in the frequency domain is analyzed. This exact analysis is based on the classical formulation of three-dimensional elastodynamics, for fluid-loaded spherical shells of arbitrary thickness. Form functions, residual responses, and the partial-wave expansions of both, are determined. Results are displayed in relatively wide frequency bands for various increasing shell thicknesses. The resonance features in the sonar cross sections (SCS) are isolated by means of a new hybrid modal background that substantially improves the results found with the earlier (rigid/soft) backgrounds of the resonance scattering theory (RST). The resonance features in the SCSs that correspond to each mode, and also to each of the various shell waves that propagate around its periphery are isolated. There seem to be over half-a-dozen shell (generalized Lamb and Stoneley) waves manifesting their influence in the SCSs within the examined band. Three large-amplitude features are most noticeable. There is a (slow) wave due to the double curvature of the shell which is responsible for a large, spiky feature at low frequencies.

There is the spherical A0 wave, caused by the coincidence effect, responsible for a broad ‘‘bump’’ with superimposed spikes, which appears in the midfrequency region, near x∼(h′)−1, where h′ is the relative shell thickness. There is also a thickness resonance feature at high frequencies, which is due to a wave that propagates through the shell thickness at the incidence point. There is a spherical Stoneley-type wave that resides mostly in the water in the frequency region below coincidence, xc, at which the A0 wave is activated. Finally, there are two resonance families caused by spherical analogs of the symmetric, Sn, and the antisymmetric, An, Lamb waves originally studied in flat plates. These spherical generalizations are denoted by the same symbols Sn, An, with the understanding that they now refer to shells. This model’s results for phase velocities, cutoff frequencies, etc..., are compared to those produced by simpler approaches in order to size the approximations introduced by those simpler models. This serves to establish the benchmark nature of the present model and of the calculations it produces, which are displayed in many instances. Dispersion plots are generated for the phase velocities cp(x) of all the above-mentioned shell waves. These cp(x) are proportional to the (real parts of the) roots of determinantal conditions that are also analyzed. Critical angles, coincidence phenomena, and reflection and transmission properties of the shell are examined and all the required physical interpretations are given.
Free-field acoustic calibration of long underwater acoustic arrays in a closed chamber
Authors: Luker L. D. , Zalesak J. F.
Published: October 2005

In this paper a closed-chamber technique for measuring the complex free-field sensitivity and directivity patterns of long underwater acoustic arrays is described. Performing these free-field calibrations normally requires a large body of water to ensure that the reflections from the sides, surface, and bottom have a negligible effect on the measurement. The chamber contains acoustic projectors and monitoring hydrophones located along its length. The projectors are driven to produce an acoustic pressure field in the chamber that is equivalent to a free-field plane acoustic wave propagating from any angle of incidence. This is accomplished by first measuring the transfer matrix for the calibration system. The transfer matrix relates the sound pressures at the hydrophone locations to the electrical drives to the projectors. The required projector drives, both amplitude and phase, are then determined by inverting the transfer matrix. A prototype calibration system has been developed. The system can operate over the frequency range from 10 to 600 Hz and is capable of simulating depths to 410 m. Directivity patterns obtained using the prototype for a test line array are in good agreement with theoretically predicted patterns.
Narrow-band performance of phase-conjugate arrays in dynamic random media.
Authors: Dowling David R. , Jackson Darrell R.
Published: October 2005

Phase-conjugate arrays in underwater acoustics are of interest because of their ability to produce retrodirective fields. The theoretical narrow-band performance of acoustic phase-conjugate arrays in the presence of static and dynamic random media will be presented. For a static random medium, our results suggest that random refraction allows phase-conjugate arrays to ‘‘super-focus,’’ that is, produce a focal region smaller than the free-space diffraction limit. For a dynamic random medium, the round-trip time delay between the source and the array degrades phase-conjugate array performance. When the dynamics of the medium are characterized by the statistics of oceanic internal waves, analytical results can be obtained for the intrinsic or ‘‘maximum-possible’’ signal-to-noise ratio produced by the array at the source location. For a typical deep-water oceanic medium, internal wave dynamics do not preclude interesting applications of phase-conjugate arrays. [Work supported by ONR.]
Diffraction of acoustic waves by a circular disk.
Authors: Dlubac J. J. , Huang C. J. , Chwang A. T.
Published: October 2005

Fredholm integral equations of the second kind are applied to study the diffracted acoustic field of a point source at an arbitrary location relative to a circular disk that may be either acoustically hard or soft. The velocity potential at an arbitrary field point is expressed in terms of a surface-source distribution with complex densities. A set of six real Fredholm integral equations of the second kind is used to determine the surface-source densities. These equations are solved by the method of successive approximations, which is also called the direct integral method. In order to accelerate the convergence of the iteration process, an under-relaxation algorithm is applied in the computer program. The under-relaxation factor used in the present study is between 0.4 and 0.8. It is found that the numerical result usually converges within 30 iterations. Pressure contour plots are obtained for acoustically hard circular disks that are compared to those for soft disks. When the source is located on the axis of symmetry, a pattern of local maxima and minima of the pressure appears along the axis for both hard and soft disks. The distance between neighboring ‘‘hot’’ spots (points with maximum pressure) decreases as the source moves away from the disk.
Analysis of the ultrasonic wave scattering by end of a plate immersed in water.
Authors: de Billy M. , Piet J. F.
Published: October 2005

This paper is concerned with the study of the acoustic field scattered by the end of a plate immersed in water which is insonified by an outside source. The experiments are achieved on plates symmetrically situated with respect to the beam axis. The angular diagram reveals the existence of maxima whose angular positions vary with the product of the frequency times thickness of the plate (Fd). Some of the maxima are due to the excitation of leaky symmetric modes and the number of these guided waves depends on the value of Fd. The other maxima may be caused by the diffraction from the end of the plate that acts as a ‘‘diffracting slit.’’ Results will also be carried out for two plates bounded under different conditions and explained in terms of single plate. [Work supported by DRET.]
The acoustical background for a submerged elastic shell.
Authors: Werby M. F.
Published: October 2005

The resonance process can be viewed as a superposition of an acoustical background (a rigid scatterer for elastic solids) and the resonance response. This technique proved valuable for isolating the lower frequency resonances as well as to understand the nature of resonances excited by acoustical signals impinging on elastic solids. In particular, one could subtract the rigid background mode by mode in partial wave space to isolate the resonances. An analogous background for elastic shells has proven elusive over the years though for very thin shells a soft background has proven adequate for the lower frequency region, while for thicker shells and at appropriately higher frequencies a rigid background has in some cases proven useful. In this work a new model is proposed that describes the background of an elastic shell for a suitable thickness region over the entire frequency range. Further, in the limit of thin shells at the lower frequency end it is shown to equal a soft background, while for thicker shells and at higher frequencies it goes into a rigid background. The appropriate mass dependence for the new background is also observed. The usefulness of the new background is demonstrated for several examples in which it is shown that by subtracting the new background, one is better able to isolate resonances than for the elastic soft/rigid analogs.
Application of time-frequency analysis to acoustic scattering.
Authors: Hackman Roger H. , Abatzoglou Theagenis J. , Arnold Hal
Published: October 2005

In a scattering experiment, it is generally true that the contributions (pulses) associated with different dynamical processes arrive at the field point at different times and that these pulses show evidence of dispersion that is characteristic of the underlying scattering dynamics. Thus the time-frequency structure of the echo return is intimately connected not only with the frequency bandwidth and shape of the incident pulse, but also with the target response. Elements of the above have been discussed by previous authors [e.g., Yen etal., J. Acoust. Soc. Am. Suppl. 1 84, S185 (1988)]; in this paper, a comparative study of time-frequency analyses of the numerically synthesized echo returns of solid finite cylinders with several algorithms is presented, including the Wigner distribution, Choi–Williams distribution (along with its high resolution version), the Gabor transform, and wavelet algorithms. The goal of this work is to relate the time-frequency structure of the echo return to the scattering dynamics and to compare the efficacy of the different algorithms for the analysis of that structure.
Grain bulk modulus of sand.
Authors: Darrouzet Jennifer L. , Molis Joseph C. , Chotiros Nicholas P.
Published: October 2005

The objective of this project is to determine the grain bulk modulus of sand, as it has not been found directly before. The compressibility of sand has been assumed to be the same as that of quartz, though this has never been proven. The constant under question is being measured for sand from several different locations, each mixed in an enveloping liquid of either castor oil or water. A pressure chamber is used to compress the mixtures up to a working pressure of 2000 psi. As pressure is released, the rate of change of volume with respect to change in pressure is measured. Volume change is measured in a tall glass tube that serves as a graduated cylinder. A pressure transducer is used to monitor changing pressures in the chamber. The compressibility of both castor oil and water was checked, as compared to a sample of stainless steel of known compressibility. The observed ratio of volumes between test fluid and sand sample is then taken into account in order to determine the compressibility of the sample in the enveloping liquid.
Wave propagation theory in anisotropic periodically layered fluid-saturated porous medium.
Authors: Sun Fangning , Banks-Lee Pamela , Peng Hong
Published: October 2005

A study is made of harmonic plane wave propagation through an anisotropic periodically layered fluid-saturated porous medium. Biot’s theory is used to describe the constitutive equations of a fluid-saturated porous solid. Employing the idea of introducing fundamental elasticity tensors, the field equations governing the wave propagation are derived in terms of first-order matrix ordinary differential equations. Propagator matrix formulation is adopted to treat the periodically layered property. Within this framework, the inhomogeneous medium is treated by dividing it into homogeneous layers. This technique is acceptable provided the coefficient matrix of ordinary differential equations consists of piece-wise constants. Also, within each layer, the general case of anisotropic fluid-saturated porous materials can be considered. Based on this approach, computer software has been developed and a numerical example is presented using air as the acoustic medium.
T-matrix formalism for scattering from a porous saturated inclusion embedded within a porous saturated medium.
Authors: Kargl Steven G. , Lim Raymond
Published: October 2005

The scattering from an inclusion embedded within a host is analyzed within the framework of Biot’s theory for wave propagation in porous saturated media. The inclusion and host are assumed to be porous saturated media with distinct material parameters. Norris has derived a solution for radiation from a point source and he has considered a Green’s function analysis of the scattering problem [A. N. Norris, J. Acoust. Soc. Am. 77, 2012–2022 (1985)]. A transition (T-) matrix scattering formalism has been developed within the full Biot theory (i.e., including attenuation mechanisms) for an arbitrarily shaped inclusion. In implementing a T-matrix formalism, Betti’s identity from elastic wave scattering [Y. H. Pao, J. Acoust. Soc. Am. 64, 302–310 (1978)] was generalized to porous media where the additional slow longitudinal wave is present. The T-matrix formalism is specialized to a spherical inclusion and calculations of extinction, scattering, and absorption cross sections for ideal porous media (no attenuation) will be discussed. Elastic wave scattering is recovered as the porosity of each media approaches zero and the solid constituent is considered to be perfectly elastic.
Biot–Stoll model of sea ice.
Authors: Sammelmann Gary S.
Published: October 2005

At a previous meeting, K. L. Williams etal. [J. Acoust. Soc. Am. Suppl. 1 87, S56 (1990)] presented a Biot–Stoll model of the elastic moduli of sea ice. The present article describes a simple application of this model to calculate the high-frequency reflection coefficient of sea ice as a function of the salinity and temperature of the sea ice and the porosity of the dendritic layer. Sea ice is modeled as a simple open pore Biot–Stoll layer underlying a closed pore Biot–Stoll half-space. This model focuses on the effects of the ice–water interface on the reflection coefficient of sea ice and it ignores the effects of the snow–ice interface.
Simple 3-D Gaussian beam propagation model.
Authors: Bucker Homer
Published: October 2005

In many practical Navy acoustic systems the sound field is strongly affected by three-dimensional variations in the ocean bottom. A theory is presented for a simple Gaussian beam propagation model that accounts for full three-dimensional effects of the ocean bottom. Examples will be shown for a typical site in shallow water. Also, a comparison will be made between the experimental data of Glegg and Yoon [J. Acoust. Soc. Am. 87, 101–105 (1990)] and calculated data for propagation across slope in a wedge.
Production and perception of the consonantal voicing distinction in speech without VOT: An acoustic study using electric larynx speech.
Authors: Kobayashi Noriko , Honda Kiyoshi
Published: October 2005

Acoustic features and perceptual cues for the voicing distinction of intervocalic stops were investigated using electric larynx speech. Alaryngeal talkers who speak American English with an electric larynx of the transcervical type produced multiple repetitions of /schwa CVC/ syllables. As the sound source of the electric larynx was continuously generated throughout an utterance, systematic control of voice onset time (VOT) was not available for the intervocalic stops in this speech. Statistical analyses based on the talkers’ intention revealed that duration and amplitude of high-frequency noise following the consonant release were increased for the voiceless stops than for the voiced cognates. The F1 frequency value of the following vowel was higher for the voiceless stops than for the voiced cognates. The major finding of the perceptual experiment was that duration and amplitude of the above-mentioned high-frequency noise were highly correlated with the perception of ‘‘voicelessness.’’ Articulatory efforts made by the electric larynx talkers and the perceptual effectiveness of the efforts will be discussed. [Research supported, in part, by NIH Grant to Haskins Laboratories.]
The role of the jaw in consonant articulation.
Authors: Jun Sun-Ah , Lee Sook-hyang , Beckman Mary E. , De Jong Kenneth
Published: October 2005

Various linguistic roles have been hypothesized for the jaw. In Browman and Goldstein’s ArticulatoryPhonology, it is identified as the common articulator among gestures involving the lower lip, tongue tip, and tongue body, and Goldstein has suggested that this may underly the differentiation in Arabic phonology between oral consonants (labials, dentals, velars) and gutturals (uvulars, pharyngeals, glottals). Keating (1983) proposed that consonants are specified for relatively fixed jaw heights (sibilants higher than stops higher than glides), providing the phonetic basis for sonority sequencing constraints. Macchi (1985) proposed that jaw height during consonants reflects both a passive coarticulation with neighboring vowels, and an active suprasegmental specification (lower in stressed syllables). This paper re-examines these hypotheses using a corpus contrasting different places of articulation. The hypotheses are supported more or less well, depending on place. For example, Macchi’s hypothesis was borne out for labials, but the jaw was quite low during velar stops in unstressed syllables, usually lower than in the preceding vowel. These results suggest that no linguistic role can be stated straightforwardly for all consonants. Rather, the jaw’s contribution varies in proportion to the distance of the oral articulator from the condyle. [Work supported by the NSF.]
Phonetic coding and its relationship to talker and rate normalization.
Authors: Tomiak Gail R. , Green Kerry P. , Kuhl Patricia K.
Published: October 2005

Listeners perceptually adjust for the acoustic variability brought about by differences in talker (voice) and rate information. To account for this adjustment, researchers have posited the existence of normalization processes. The purpose of the experiments reported here was twofold. First, the nature of the relationship between phonetic coding processes and talker and rate normalization processes was examined using monosyllables varying in three dimensions [phonetic (/bi/, /pi/); talker (male, female); rate (fast, slow)] in a speeded classification procedure [W. R. Garner, TheProcessingofInformationandStructure (Erlbaum, Potomac, MD, 1974)]. Subjects classified the syllables along each of the three stimulus dimensions under two testing conditions: when the syllables varied only in the relevant/attended target dimension (single dimension) and when the syllables varied along the relevant and an irrelevant/unattended target dimension (orthogonal). Results indicated that decisions about phonetic identity were dependent upon both talker and rate information: Irrelevant variation in either dimension interfered with (increased reaction time to) phonetic classification. While rate classification was also affected by phonetic variation (integral), talker classification was not (separable). A final experiment, using the same stimuli and reaction time procedure, explored the relationship between the two normalization processes. Results indicated an integral relationship: Variation in talker information interfered with rate classification and vice versa.
Level discrimination of stop-consonant noise bursts: Performance in single- and two-interval tasks with single and multiple standards.
Authors: Miller Michele R. , Espinoza-Varas Blas
Published: October 2005

Discrimination of increments in the rms level of either the initial or final consonant noise burst of the word (pæt/) was measured for seven highly trained, normal-hearing listeners. The stimulus was a single token of /pæt/ produced by a female talker and digitized at 20 kHz. The noise bursts’ sample points were multiplied by (1+k), 0.025≤k≤4.1, to obtain rms-level increments ranging from 0.2–14.0 dB. Experiment I (n=4) compared discrimination performance for noise bursts presented either ‘‘in isolation’’ (i.e., excerpted from the word) or in word context. A constant-stimulus 2IFC procedure was employed. Level discrimination thresholds expressed as 20 log (1+k) were 2.0–3.0 dB for both the /p/ and /t/ bursts ‘‘in isolation.’’ Thresholds ‘‘in context’’ were 2.0 dB for /t/ and 5.0–7.0 dB for /p/. Experiment II (n=3) compared level-discrimination performance measured in four different tasks for /p/ or /t/ bursts presented ‘‘in context.’’ The tasks were (a) 2IFC with a single standard (/pæt/); (b) 2IFC with three standards (/kæt, pæk, pæt/); (c) single interval, single standard; and (d) single interval, three standards. A strong context effect was again obtained with the /p/ burst, but the effects of task and number of standards were small. [Supported by OCAST Grant HSO-005 and Presbyterian Health Foundation.]
The effect of rate of amplitude comodulation on sentence perception.
Authors: Opie Jane M. , Carrell Thomas D.
Published: October 2005

Previous studies of the perception of time-varying sinusoidal (TVS) sentences suggested that amplitude comodulation may serve as a grouping cue in speech perception [T. D. Carrell, J. Acoust. Soc. Am. Suppl. 1 86, S102 (1989)]. The purpose of the present investigation was to further explore that idea and to evaluate whether the effects observed in TVS studies are related to other temporally based phenomena such as comodulation masking release (CMR). If a common process underlies the perception of amplitude-modulated speech and nonspeech stimuli, then grouping effects should occur in speech perception in a manner similar to that observed in nonspeech studies when the amplitude modulation characteristics are similar. Examined in the present study was the effect of amplitude modulation rate on intelligibility of TVS sentences as compared with rate effects in CMR phenomena. Amplitude modulation rates were 5, 10, 20, 50, 100, and 200 Hz. Although the results suggested that comodulation is important in speech perception, effective rates may be different from those observed in nonspeech tasks. These findings are important for our understanding of auditory object formation of both speech and nonspeech stimuli.
The use of arrays in differentiating between water–bottom interface scattering and subbottom scattering.
Authors: Tang Dajun , Frisk George V.
Published: October 2005

Two major causes of sound scattering from the ocean bottom are the rough water–bottom interface and the inhomogeneities within the bottom. For low frequencies (up to a few kilohertz), both scattering mechanisms may be important. An experiment has been proposed that differentiates between scattered signals associated with these two scattering mechanisms by utilizing the directional characteristics of acoustic arrays. Here, this technique is demonstrated on synthetically generated scattered signals for different environments. The advantages and limitations of using arrays to achieve the desired differentiation are discussed. [Work supported by ONR.]
Acoustic imaging of black smoker hydrothermal plumes: East Pacific Rise 21°N, 109°W.
Authors: Palmer D. R. , Rona P. A. , Chayes D. A. , Jones C. D. , Czarnecki M. F. , Carey E. W. , Guerrero J. C.
Published: October 2005

During the November 1990 dive series of the US Navy DSV Turtle, plumes emanating from high-temperature black smoker-type vents were imaged using a prototype sonar system mounted on the submersible. The study focused on two plumes from adjacent sources that were scanned horizontally in arcuate sectors at increasing angular increments from the vent orifices up to 90°. Multiple data sets were recorded at horizontal ranges of 3–70 m from the base of the plumes and sonar ranges to 200 m with submersible stationary on the seafloor. Computer graphics were used to reconstruct the plumes in cross section and in 3D, revealing coherent plume images up to 100 m above the seafloor. Multiple plume cross sections recorded at the same level show changes in shape and distribution of suspended particulate matter on a time scale of seconds. Whole images show coalescing of the buoyant plumes and deflection by the prevailing current. The work demonstrates the value of acoustic imaging of plumes for initial detection and for characterization of plume dynamics.
Artificial neural networks for simultaneous and independent range and depth discrimination in passive acoustic localization.
Authors: Zakarauskas Pierre , Ozard John M. , Brouwer Peter
Published: October 2005

Two feedforward neural networks (NNs) with one hidden layer each were trained using a modified backpropagation algorithm to determine the position of an acoustic source in a waveguide. One network was trained to localize the source in depth while the other was trained independently to localize in range. The signal was preprocessed by decomposition along an orthogonal basis vector set in order to increase the robustness of the resulting trained network to uncertainties in the signal and environmental parameters. The output layer consisted of one unit for each possible range or depth of the source. The NNs were trained with a signal-to-noise ratio (S/N) of 50 dB and tested with patterns generated with S/Ns ranging from 50–0 dB. The performance of the NNs was compared with that of a conventional nearest neighbor processor. Evaluation of the processors was done in the context of an estimation problem, i.e., by measuring the standard deviation of the processors’ outputs. The NNs turned out to be less resistant to noise than the conventional processor, but were faster.
Single-frequency matched-field processing with a single hydrophone.
Authors: Collins Michael D. , Tinker Laurie E. , Perkins John S. , Makris Nicholas C. , Kuperman W. A.
Published: October 2005

The most common formulation of matched-field processing (MFP) involves a single frequency and an array of hydrophones. Since arrays are difficult to deploy (especially vertical arrays), single-hydrophone MFP methods might prove to be of great practical value. Broadband MFP methods of this type have been developed by Frazer and Pecholcs [J. Acoust. Soc. Am. 88, 995–1102 (1990)]. Single-frequency, single-hydrophone localization is possible by synthetic aperture if the source is in steady motion (the receiver may also be moving). By working in the frequency domain, less computational effort is required for constructing replica fields, and it is possible to focus on individual spectral lines of a source to window out interference from other sources and noise. Furthermore, it is possible to localize in three dimensions by taking advantage of environmental complexity.
Improved estimation of the bearing of a narrow-band source using a spatially referenced towed array.
Authors: Tufts Donald W. , Edelson Geoffrey S.
Published: October 2005

The spatially referenced towed array is introduced as a system for the simultaneous estimation of source bearing and frequency. This system consists of both a conventional towed array and a fixed-position array of passive sensors. The stationary array, which may consist of only a single hydrophone, functions as the spatial reference and supplies additional frequency information to the towed array. The limits on bearing and frequency estimation error predicted for conventional towed arrays by the Cramér-Rao lower bound (CRLB) are greater than those for the corresponding fixed-position arrays when there is no knowledge of both the source frequency and bearing. In contrast, the CRLB performance of the towed array with respect to bearing estimation improves over that of the stationary array given perfect knowledge of the source frequency. The spatially referenced towed array is shown to improve significantly upon the bearing CRLB performance of a conventional towed array for the case in which both the source frequency and bearing are unknown.
Effects of mass loading on the propagation of Lamb waves.
Authors: Wu Junru , Zhu Zhemin
Published: October 2005

The influence of liquid layers on the propagation of Lamb waves in a plate of finite thickness is studied theoretically. The dispersion equations of Lamb waves in a plate bordered with layers of liquids are derived and solved numerically. For the zeroth-order antisymmetrical mode (A0 mode) of very thin plates, the numerical results calculated from the dispersion equations are compared with those derived from the bending wave acoustic impedance approach. The limitation of the latter is discussed. [Work supported by BFGoodrich Simmonds Precision Aircraft System.]
Simulating three-dimensional acoustic fields with a lattice gas model for waves.
Authors: Numrich S. K. , Krutar R. A. , Squier R. K. , Pearson J.
Published: October 2005

Simulations of acoustic field behavior based on a lattice gas model for waves were presented at the 121st Meeting of the Acoustical Society of America [J. Acoust. Soc. Am. 89, 1894(A) (1991)]. Since that time, the model has been extended to three dimensions. The model runs on a connection machine and is implemented in a fashion well suited to the computer’s SIMD architecture. The results are consistent with the anticipated field behavior and the computation is very rapid, on the order of three frames per second where a typical frame is a cube with 128 thirty-two bit values on a side. There are no narrow angle restrictions and sound speed can change in all directions. [This work has been supported by ONT.]
Far-field holography applied to an arbitrary geometry.
Authors: Sarkissian Angie
Published: October 2005

An algorithm is developed for the reconstruction of the surface acoustic field from measurements of pressure made in the far field for a structure with arbitrary geometry. This inverse problem is ill-posed due to the presence of evanescentlike modes that decay very rapidly away from the surface making them difficult to reconstruct. The boundary elements method is applied. The presence of the evanescentlike field is treated by expanding surface normal velocity in a set of functions that form the eigenstates of radiated power, computed by diagonalizing the surface resistance operator, the sum truncated to remove the modes with negligible radiation. The algorithm is tested by applying it to scattering from a rigid cylinder with hemispherical endcaps. It is also applied to the radiation problem of a small piston located on the same cylinder, where the resolution attained on the surface is shown to increase with increasing frequency.
Boundaries of negligible reflection coefficients achieved by single compliant layers.
Authors: Sheiba L. , Maidanik G. , Dickey J.
Published: October 2005

The basic boundary is assumed to possess a (specular) reflection coefficient that is not negligible, i.e., [Zp(ω)/Zf(Θ)] does not approach unity. Here, Zp(ω) is the surface impedance of the basic boundary at the frequency ω and Zf(Θ) is the surface impedance of the fluid that occupies the semi-infinite space above the boundary. It is noted that Zf(Θ)=[ρc/cos(Θ)], where ρ and c are the density and speed of sound in the fluid, respectively, and Θ is the angle of incidence from the normal to the plane of the boundary. For a basic boundary that possesses a surface impedance Zp(ω) that is mass controlled, namely, Zp(ω)=iωMp, where Mp is the surface mass, a compliant layer of surface impedance Zc(ω)=(K/iω)(1+iηc), placed atop the basic boundary, will render the reflection coefficient negligible if: ηc=[ωMp/Zf(Θ)]; ω2=(K/Mp)(1+ηc2). In another example, the surface impedance ratio ‖Zc(ω)/Zp(ω)‖ at the frequency ω of concern is small compared with unity, then one may render the reflection coefficient of the boundary negligible by adding a panel of surface impedance Z1(ω) that is mass controlled atop the compliant layer: Z1(ω)=iωM1. In this case the reflection coefficient will be negligible if: ηc=[Zf(Θ)/ωM1]; ω2=(K/M1). In both examples the reflection coefficient is rendered negligible by providing the reflecting boundary with a resonant dynamic system that is adjusted so that the resonance frequency coincides with the frequency of concern. To achieve negligible reflection coefficient, the loss factor ηc of the compliant layer needs to be appropriately adjusted. The need for the later adjustment will be discussed.
Do octave complexes facilitate learning to identify pitch class?
Authors: Laden Bernice , Goad Pamela
Published: October 2005

This research explored the ability to learn to identify the pitch class of sine and complex tones. It was hypothesized that pitch-class identification could be improved if octave complexes were used in training. Shepard tones [R. N. Shepard, J. Acoust. Soc. Am. 36, 2345–2353 (1964)] were thought to be ideal pitch-class exemplars because they contain only octave-related partials and have an envelope that controls for pitch height. Three groups of undergraduate music majors participated in the study. None had absolute pitch. Subjects were given a pre- and post-test of their ability to name the pitch class of sine tones, various acoustical instrument tones, synthesizer tones, and Shepard tones. Group 1 controlled for maturation effects and did not receive any training. Subjects in groups 2 and 3 attended five training sessions. Digital piano tones were used in group 2 training sessions, while Shepard tones were used for group 3. There were reliable differences between group 2 and group 1 scores. Group 3 scores were higher than group 1 scores, but the difference was not statistically significant. Although results indicate that training facilitates pitch-class naming ability, Shepard tones do not give subjects an advantage over digital piano tones. [Work supported by the Virginia Merrill Bloedel Hearing Research Center.]
Acoustical and electronic instruments in jazz: A compositional perspective.
Authors: Boulanger Richard
Published: October 2005

Electronic instruments are an important aspect of the sound of today’s music. Still, although the overall sound of jazz has been significantly enhanced by digital synthesizers, signal processors, and recording technology, these tools have yet to have a serious impact on jazz composition or performance. The sounds are ‘‘new,’’ but their musical use is not; and, although the instruments played by keyboardists and drummers are now digitally based, the role of the musicians playing them, and, for that matter, the ‘‘jazz’’ played on them, is not new at all. Clearly, computers are changing how we work at making music, but are these powerful new tools resulting in a powerful new music? Is this ‘‘exciting’’ new context for music actually extending and redefining the art of music itself? For the most part, the answer is ‘‘no.’’ However, there is a new generation of programs that in many ways embody the improvisatory spirit of jazz. Further, they allow the computer to take an active role in the music-making process and, by so doing, redefine the creative process and set the stage for a new music and a new orchestra−thevirtualorchestra... In this presentation, music composed and performed with the assistance of Jam FactoryTM, OvalTuneTM, sYbilTM, InteractorTM, MaxTM, and the Mathews’ Conductor Program will serve to demonstrate that the computer does hold the key to new forms of musical expression, and may one day even break down the barriers of musical genre.
Acoustical and electronic instruments in jazz: A wind performance perspective.
Authors: Marvuglio Matt
Published: October 2005

It has been only 4 years since Akai and Yamaha introduced the first MIDI wind controllers at the Chicago Exposition of the National Association of Music Merchants. These instruments were designed to be the wind player’s link to digital electronic music hardware−synthesizers, sequencers, and other computerized applications. The true potential of these windcontrollers has never been as an electronic facsimile of the flute, clarinet, or saxophone, but rather as a step beyond the world of standard instrumental timbres into; who knows where? This presentation addresses the questions of how a MIDI wind controller may be used in jazz performance, and how technology is handing wind players an instrument whose potential is not clearly related to their demands as performers.
Hybrid ray-mode parametrization of acoustic scattering from submerged internally loaded thin cylindrical elastic shells: Reformulation of angular harmonic resonant mode data.
Authors: Felsen Leopold B. , Guo Yue-Ping
Published: October 2005

Angular harmonic resonant-mode expansions have recently been applied to determine the two-dimensional scattering of a plane sound wave incident transversely on a fluid-immersed thin elastic cylindrical shell with a variety of axially invariant internal loadings [Y. P. Guo, submitted to J. Acoust. Soc. Am.]. The scattered field, especially in the mid- and high-frequency ranges, reveals important new features that are due to the internal loading and that appear to be closely tied to traveling waves, with localized induced excitations arising from the vicinity of the lines of attachment of the internal loads. To show these more directly in terms of waves, the problem is reparametrized in terms of the hybrid ray-mode algorithm developed previously for empty source-excited cylindrical shells [L. B. Felsen, J. M. Ho, and I. T. Lu, J. Acoust. Soc. Am.], but augmented now by on-surface equivalent forces induced by the loads. This observable-based parametrization (OBP) is shown to reconstruct the angular harmonics solution with remarkable accuracy, with efficient versatility accommodating loadings of various kinds, and with cogent insight into the relevant physical wave processes. It is therefore suggestive that OBP can be adapted adiabatically to structures that depart from the idealized infinite cylindrical shell model. [Work supported by ONR.]
Harmonic response of finite cylindrical shells coupled to interior fluid regions.
Authors: Stepanishen Peter R. , Hassan Scott E.
Published: October 2005

The effects of internal fluid loading on the harmonic response of finite circular cylindrical shells were investigated. Interior fluid loading on the shell was included via a Green’s function approach for the Newmann boundary value problem. The shells were treated analytically and via finite-element methods. The fluid and structural models were combined and solved using both mobility matrix and eigenfunction expansion approaches. A circular cylindrical shell open at one end (i.e., pressure release) and capped at the opposite end was investigated as a special case. The shell was driven by a force acting on the end cap along the axis of symmetry. A parametric study of this configuration was conducted. An experimental investigation of this configuration was also conducted. Analytical results for the invacuo and fluid-loaded shell response are compared to experimental data. Longitudinal resonances of the interior fluid are clearly evident in the response of the shell.
The acoustic realization of metrical structure by F0 maxima.
Authors: Terken Jacques , Collier René
Published: October 2005

An investigation was performed to determine whether the scaling of F0 maxima is sensitive to syntactic properties of sentences. Seventy sentences were read aloud by a professional speaker. They all had the same basic structure: NP–VP. Variations of the basic scheme were obtained by adding lexical material to the NP and VP, and by permuting the constituent order in the VP. It was found that successive F0 maxima in the NP were subject to evidence lowering (also known as downstep). The results for the VP were more heterogeneous. Here, the occurrence of the downstep pattern was apparently blocked by two factors: the presence of an accent preceding the prosodic head of a constituent, or a deviation from the canonical order of constituents. It is concluded that these factors influence the division of the utterance into prosodic domains, which, in turn, affects the scaling of F0 maxima.
Melodic cues to ‘‘finality’’ in discourse units.
Authors: Swerts Marc , Collier René
Published: October 2005

Among the possible functions of speech melody is its capacity to signal different sorts of relationships between utterances that build a discourse unit. Pitch may indicate, for example, whether a current utterance is likely to be the last one in a sequence of statements. Spontaneous speech was elicited by having subjects describe a path through a spatial network, containing geometrical figures, some of which were identical in form, but occurred in different positions (among which is the final one in the trajectory). Perceptual tests brought to light that listeners can identify the utterances in accordance with their structural positions in the spontaneous descriptions and that the pitch contours may indeed contain cues to those perceivable distinctions. The communicative relevance of pitch for signalling ‘‘finality’’ was then further investigated in perceptual experiments. It was revealed that, in pairwise comparisons, ‘‘finality’’ judgments can be significantly influenced by the following variables: the direction of the utterance-final-pitch change, the relative size of the pitch movements, the position of the contour in the speaker’s pitch register, and the type of ‘‘hat pattern’’ used.
Vocal cord vibration and speech waveform in diplophonia.
Authors: Kiritani S. , Hirose H. , Imagawa H.
Published: October 2005

Simultaneous recording of vocal cord vibration and speech signal was conducted on the three diplophonic cases using a high-speed digital imaging technique recently developed at our institute. All three cases [unilateral paralysis of recurrent nerve(1) and external branch of superior laryngeal nerve(2)] show a difference in the vibratory frequency between the left and right vocal folds. During successive cycles, the phase difference progressively becomes larger. At a certain point, when it exceeds a threshold, the phase difference is reset and the vocal cord movements resume synchrony. This pattern is in good agreement with that described by Moore. When the movements of the vocal cords are in phase, the glottal closure is complete and the excitation pattern in speech waveform is large, whereas when the movements are out of phase, the glottal closure is incomplete and the excitation pattern is weak. This quasiperiodic variation in speech waveform appears to be related to the diplophonic voice quality in the present cases.
Exploring declination utilizing a dynamic systems approach.
Authors: Hogue David M. , Porter Robert J. , Tobey Emily A.
Published: October 2005

Recent reports suggest the value of examining various aspects of speech production from a nonlinear ‘‘dynamic systems’’ point of view [e.g., Kelso and Tuller, J. Physiol. 246, R928–R935 (1984)]. Such an approach searches for behaviors that reflect generic properties of self-organizing, dynamic systems, such as phase transitions, order or control parameters, and fractal dimensions [e.g., R. J. Baken, ASHA Fall 1990 and J. Voice (in press); M. T. Turvey, Am. Psychol. 45, 938–953 (1990)]. The attempt to examine fundamental frequency declination and intrautterance resets over phrase and sentence length utterances using this approach will be reported. Using reiterant syllable utterances, effects of task variations, such as speaking rate, intonation, and depth of initial inspiration, are examined in the context of what changes in behavior reveal about the coupling of component systems and possible ‘‘order parameters.’’ [Work supported by the Dept. of Psychol. and Chancellor’s Fellowship.]
Reception of the Heard Island signals off South Africa.
Authors: Brundrit G. B. , van Ballegooyen R. C. , Valentine H. R. , Krige L. , Potgieter E. , Stander M. P. , Sale D. , Hardisty A. C. , Runciman P. B. , Lazarus M. D. S.
Published: October 2005

Heard Island experiment sound transmissions were received at sea some 300 km south west of the Cape of Good Hope on a 40-m vertical hydrophone array deployed from the vessel SAS Umzimkulu. This area, 53-min travel time along the Atlantic path from Heard Island, lies immediately down-path from strong regional variability in the acoustic properties of the SOFAR channel, associated with the retroflection of the Agulhas current. A total of eight transmission periods, covering cw, pentaline, and m-coded sequences were successfully received, with a peak signal-to-noise ratio of 41 dB during the cw transmission of 0000Z on 30 January 1991. Reception was of varying quality with some transmissions not being received at all and with successful reception periods having appreciable fluctuations in signal strength. A combination of difficult operating conditions and the up-path disturbances to the sound channel were crucial in determining the character of the actual signals received.
Preliminary analysis of the Ascension Island receptions.
Authors: Georges T. M. , Palmer D. R. , Boden L. R.
Published: October 2005

The strength and quality of the Ascension signals received from Heard Island were exceptional, probably because of low background noise as well as a propagation path relatively unobstructed by bathymetry and having a shorter segment in the Antarctic surface duct than eastward paths. Analysis of the cw and pentaline signals shows remarkable phase stability over a 9100-km path. Analysis of the m-sequence transmissions shows arrivals spread over about 8 s, roughly in agreement with propagation modeling for the path. Because of source motion, however, arrival structure does not show continuity from transmission to transmission. Coherence of phase and amplitude over four on-axis hydrophones spaced several kilometers apart is briefly examined, in anticipation of beamsteering and scintillation analyses.
The victory squeal of dolphins and white whales on the surface and at 100 m or more in depth.
Authors: Ridgway S. H. , Carder D. A. , Romano T. A.
Published: October 2005

After seizing a fish, small odontocetes often produce a rapid series of pulses that we call a ‘‘Victory squeal.’’ Animals trained to dive to depth and turn off a switch that was emitting a continuous tone [S. H. Ridgway etal., Science 166, 1651–1654; Can. J. Zool. 62, 2349–2351] made the victory squeal (Vs) within 1 s of tone termination (reinforcement signal or Sr). When dolphins (Tursiopstruncatus) or white whales (Delphinapterusleucas) were trained for other tasks, a Vs was commonly produced after the Sr (in these cases Sr was a whistle, tone, or underwater buzzer activated by the trainer for correct responses). At a depth of 100 m or more, Vs peak frequency of the white whale was lower than at the surface (p<0.001), while pulse repetition rate was higher at depth (p<0.05). Vs averaged 14.2-kHz peak frequency, 7.14-kHz, 3-dB bandwidth, and 247 pps at depth. At the surface, values were 29.3 kHz, 15.30-kHz, 3-dB bandwidth, and 179 pps (n=10 at surface, 10 at depth). Dolphin Vs latency after Sr was 560±192 ms (n=179). White whale Vs latency was 796±170 ms (n=104). Vs latency was shorter with higher amplitude of the Sr.