bluuebunny/crossref_metadata_2025 huggingface dataset:
Chirp sonar for classification of marine sediments
Authors: LeBlanc Lester R. , Mayer Larry A. , Schock Steven G.
Published: October 2005

The chirp sonar is a calibrated wide-band digital FM sonar that provides quantitative, high-resolution, low-noise subbottom data. In addition, it generates an acoustic pulse with special frequency domain weighting that provides nearly constant resolution with depth. The chirp sonar was developed with ONR funding to support the objective of remote acoustic classification of seafloor sediments. In addition to producing high-resolution images, the calibrated digitally recorded data are processed to estimate surficial reflection coefficients as well as a complete sediment acoustic impulse profile. In this paper, the focus is on the analysis of surficial sediments in Narragansett Bay, RI. Quantitative acoustic returns from the chirp sonar are used to estimate surficial acoustic impedance and to predict the sediment type. The estimates are compared to “ground truth” values determined from core samples. The comparisons show a high correlation between the core-determined sediment type and the estimates from the acoustic measurements. In concert with the field work, sediment classification models for various depositional environments are being developed. A robust model for deep-sea carbonates has been completed and more generalized models are now under development that predict impedance, density, porosity, compressibility, and rigidity. [Work supported by ONR.]
Estimates of physical properties of deep ocean sediments using deep-towed multichannel seismoacoustic data
Authors: Gettrust J. F. , Rowe M. M.
Published: October 2005

Data taken with a deep-towed acoustics/geophysics system (DTAGS) are used to study deep ocean sediments. By towing the 250- to 650-Hz bandwidth source and 48-channel hydrophone streamer within 400 m of the seafloor, spatial resolutions on the order of ∼10 m with signal penetration to ∼600-m depth was achieved. Estimates of the interval compressional velocity (Vp) within the sediments generally are within several percent of “true” interval velocities. The Vp vs depth functions for both Atlantic and Pacific sites suggest that the Vp gradient is generally extremely low within the upper ∼50- ∼125 m of sediments, then increases with depth; this result is not consistent with simple sediment compaction models used to develop previous geoacoustic models. Further, the spatial variability of Vp within the sediments (> 5% over distance scales of 10 to 100 s of m) resolved with these data indicates that range independent geoacoustic models are not satisfactory. Shear velocity estimates are also presented and used to constrain geoacoustic predictions. [Work supported by ONR and ONT.]
Remote sensing of seabed compressional wave attenuation from acoustic cw propagation experiments combined with the bottom shear modulus profiler (BSMP) database
Authors: Rogers Andrew , Yamamoto Tokuo , Tappert Fred , Carey William
Published: October 2005

As a result of recent ONR shallow water ARI, an accurate database of the compressional wave velocity, the shear wave velocity, and the density of the sediment for the continental shelves of Northeastern U.S. is available (Yamamoto and Trevorrow, in this conference). It has been shown that the model structures of acoustic waves propagating in these shallow waters are very accurately modeled using the BSMP database as compared with the cw propagation experiments [J. Acoust. Soc. Am. Suppl. 1 88, S106 (1990)]. In this paper, it is shown that the compressional wave attenuation within the seabed can be accurately determined from the wave-number energy spectra of cw propagation data from range-independent environments. The seabed geoacoustic data so obtained are then used in the modeling of acoustic cw propagation in range-dependent cases using Fred Tappert's PE code and compared with Bill Carey's experiments. Excellent agreements between model calculations and experiments are obtained, indicating the accuracy and stability of the combined BSMP-cw experiments for determination of seabed compressional wave attenuation in shallow water. [Work sponsored by ONR.]
Seismo-acoustic waves for remote sensing in shallow-water sediments
Authors: Akal Tuncay , Stoll Robert D.
Published: October 2005

The propagation and attenuation of seismic and acoustic waves observed in shallow water are strongly dependent on the physical characteristics of the seabottom. Because the acoustic field in the water column and seismic propagation in the seafloor are directly related, different techniques can be used for remote sensing of bottom properties. However, in each specific case the experimental technique and analysis must focus on a specific wave type. In this paper, results are presented of experiments carried out in various shallow-water areas using an “L”-shaped array consisting of hydrophones in the water column and geophones on the seafloor. The total seismo-acoustic field measured with this array, including the pressure field in the water column and the head waves, diving waves, interface waves, and Love waves in the seafloor, is utilized to demonstrate the use of this approach as a remote sensing technique for seafloor parametrization.
Acoustic remote sensing of shallow ocean sediment characteristics
Authors: Chouhan H. M. , Anand G. V.
Published: October 2005

In this paper, a procedure is presented for estimating the acoustic parameters of shallow ocean sediments from the sound field measurements using a horizontal array. The sediment is modeled as a fluid with sound speed c at the water-sediment interface, a constant sound-speed gradient g, and a constant density ρ. Initially, the modal wave numbers km (m = 1,2,…,M) are estimated using the generalized pencil-of-functions method. Next, an iterative procedure is used for estimating (c,g,ρ). This procedure is based on the fact that the phase change φm of the modal waves at the water-sediment interface can be determined from the dispersion relation using the estimated values of km. The phase change φ̂m of the modal waves can also be computed for any assumed values of (c,g,ρ). Estimates of (c,g,ρ) are obtained by adjusting their values so as to minimize the error ε = Σm(φm − φ̂m)2. Simulation results are presented to illustrate the method. [Work supported by DOE, Government of India.]
Sonoluminescence
Authors: Barber Brad , Löfstedt Ritva , Putterman Seth
Published: October 2005

Sonoluminescence (SL) is an extraordinary phenomenon in that a standing wave sound field with an energy of 10−12 eV per atom can focus to such an extent that photons are emitted with energies that can be greater than 1 eV. The phenomenon has been known for over 50 years and the long held picture that it is due to acoustic cavitation has been demonstrated beyond a shadow of a doubt by the recent work of Gaitan and Crum [J. Acoust. Soc. Am. Suppl. 1 87, S141 (1990)]. They measured the dynamic radius, light emission, and sound field of a single bubble. Here, their pioneering work is extended to determine the details of the individual photon bursts and it is found that they last less than 2 ns and incude about a million photons. From a more general perspective the issue is raised of: Do cooperative optical processes affect the bursts and what are the limits of amplification that can be achieved via the self-focusing effects which lead to SL? Calculations suggest that our current acousto-optic conversion efficiency of 10−5 can be increased by at least 3 orders of magnitude. [Work supported by the Dept. of Energy, Office of Basic Energy Sci.]
Industrial applications of high-intensity ultrasound
Authors: Hunicke Raymond L.
Published: October 2005

With the increased laboratory investigations of sonochemistry, large-scale industrial applications can be expected in the near future. The ultrasonic manufacturing industry can provide large scale equipment with power ratings in the tens of kW and with flow rates of thousands of gallons per hour. For these scales, magnetostrictive transducers have strong relative advantages over piezoelectric transducers. Prior commercial applications of ultrasound to large-scale cleaning, aluminum soldering, and coal and ore benefication are discussed.
Dichotic pitch discrimination
Authors: Yost William A.
Published: October 2005

Dichotic Huggins pitch was produced by generating broadband noise stimuli with narrow sections of the noise (bandwidths of 2, 4, 8, 16, 32, 64, and 128 Hz) interaurally phase shifted (by 90°, 135°, or 180°). The center frequencies of the narrow dichotic bands to which the interaural phase shifts were added were varied to change the value of the Huggins pitches. The just discriminable differences (obtained in a two-alternative, forced-choice adaptive procedure) in center frequency were determined for six listeners and at four (250, 400, 500, and 750 Hz) base center frequencies in an attempt to describe the pitch discrimination of dichotic Huggins pitches. For some listeners, at base center frequencies of 250 and 400 Hz and when the interaural phase shift used to produce the pitch was 180°, discrimination was almost as acute for these dichotic pitches (Δf/f=0.05%) as it was for diotically produced pitches. Pitch discrimination became more difficult as the center frequency increased to 500 and 750 Hz, the bandwidth of the interaurally altered band decreased from 128 to 2 Hz, or the interaural phase shift was reduced from 180° to 135° and 90°. The results will be discussed in terms of models of binaural processing and the use of interaural variables to segregate one sound image from other sound images. [Work supported by the NIDCD and the AFOSR.]
Detection at the level of pitch
Authors: Hafter Ervin R. , Saberi Kourosh , Jensen Eric R.
Published: October 2005

Cues consisting of harmonics f2 through f7 have been shown to reduce frequency uncertainty and thus improve the detectability of a tonal signal at f1 [E. R. Halter and R. S. Schlauch, J. Acoust. Soc. Am. Suppl. 1 86, S112 (1989)]. However, a cue at f1 did not affect the detectability of a signal consisting of only the higher harmonics. One reason for the asymmetry might be that the pure-tone timbre of a single frequency prevents its effectiveness as a cue for detection at the level of processing of pitch. Stimuli in the present study were three-tone sets, typically harmonics chosen at random from f2 through f7 from a sequence whose fundamental was itself chosen at random on each trial. For signals of constant level, best performance to worst was found with the following order: (a) cue = 3 harmonics (ex., f2, f5, f7), signal = cue (f2, f5, f7); (b) cue = 3 harmonics (ex., f3, f6, f7), signal = other 3 harmonics (f2, f4, f5); (c) no cue, signal = 3 harmonics; (d) no cue, signal = 3 randomly chosen inharmonic tones. These data are interpreted as showing that detectability can occur both at the level of the auditory filters and at the level of pitch.
Active vibration control using shear mode piezoceramic transducers
Authors: Sung Chia-Chi , Bao Xiaoqi , Varadan Vasundara V. , Varadan Vijay K.
Published: October 2005

The “d15 ” constant of the piezoceramics was utilized to design shear mode transducers. These shear mode transducers were verified to be pure shear stress/strain sensors/actuators both theoretically and numerically (ANSYS). Active torsional vibration control experiments were conducted on various phenolic and pyrex tubes by using the shear mode sensors/actuators. The free and controlled frequency responses as transfer functions were measured and compared to each other. The finite element mode-frequency analysis was performed to evaluate the structural characteristics for the tubes with and without transducers mounted. The dynamic coupling coefficients were derived for shear mode sensors/actuators based on the finite element mode shapes.
Experiments on active control of acoustic radiation from discontinuities on infinite beams
Authors: Frampton Kenneth D. , Fuller C. R.
Published: October 2005

Two experiments were performed to study the active control of acoustic radiation from discontinuities on infinite beams. One experiment studied a semi-infinite/clamped beam and the other studied an infinite beam with a blocking mass. In each case the noise input was a subsonic bending wave incident on the discontinuity. Active control was implemented using LMS algorithm driving point force shakers or piezoceramic patches with far-field microphones as error sensors. In addition, an accelerometer array was employed to investigate changes in traveling and near-field waves under control conditions. Large attenuation in radiated sound at the error locations was noted while the beam vibrational amplitude often increased under control. Spatial Fourier analysis (wave number domain) of the beam vibration showed attenuation of supersonic wave numbers (responsible for acoustic radiation) while under control. Results for various frequencies and test configurations will be discussed and mechanisms of control in terms of wave components considered. [Work supported by ONR/DARPA.]
Active vibration control of a thin plate using piezoelectric sensors and actuators
Authors: Hong S.-Y. , Varadan V. V. , Varadan V. K.
Published: October 2005

Using piezoelectric sensors and actuators, the vibrating motions of a thin plate could be effectively controlled. Several pieces of Unimorph PZT (lead-titanate-zirconate) were optimally attached on the both sides of a clamped square plate. A series of active vibration control experiments has been tried with different types of control algorithms. Even though the system structure is stiff enough because of the clamped edges, effective vibration control could be implemented with the large electromechanical coupling constant of PZT and well-selected positions of sensors and actuators. Here, particular attention has been paid to several lower-frequency modes. To take advantage of the features of a digital system such as flexibility of the control program and increased logic capability, a microcomputer and a data acquisition board were used to obtain a digital controller.
An experiment in state space control of a simply supported plate excited by steady disturbances
Authors: Rubenstein S. P. , Saunders W. R. , Ellis G. K. , Robertshaw H. H.
Published: October 2005

Experimental results of an active vibration control experiment on a simply supported plate are presented. A linear quadratic Gaussian (LQG) regulator control design is implemented to reject steady disturbances of the plate's fundamental mode. A discussion of the control law is provided. Performance of a four-mode controller is demonstrated for harmonic, narrow-band, and broadband point-force disturbances. Typical reductions in the fundamental mode amplitude were up to 60 dB at the disturbance center frequencies. Results are presented in both time domain and frequency domain format. The digital controller was implemented on a transputer-based parallel processing system for enhanced computational performance. The initial sample speeds obtained with this system were up to eight times faster than the controller hardware previously available. [Work supported by DARPA/ONR.]
SAMREC0: A C30-based reference connected-word recognizer for the evaluation of speech databases
Authors: Capman F. , Chollet G.
Published: October 2005

One of the objectives of the ESPRIT-SAM project is the elaboration of speech databases for the evaluation of recognizers. In this framework, a reference system [G. Chollet and C. Cagnoulet, “On the evaluation of speech databases using a reference system,” ICASSP, 1982], based on dynamic programming algorithm, was modified to accept connected words [G. Chollet and C. Montacie, “Evaluating speech recognizers and databases,” NATO-ASI, 1988]. This software, which is called SAMREC0 by the SAM speech input assessment group, is now implemented using a T.I. TMS320C30-based PC-board, so that it can be used efficiently on the SAM PC-AT workstation. Some results will be presented on the evaluation of the first SAM database EUROM0. This database was recorded in quiet conditions and very few classification errors are observed. Work is under development to simulate noisy conditions using the same database, in order that the limits of the reference or other systems could be measured.
Synthesis of manner and voicing continua based on speech production models
Authors: Bickley Corine , Stevens Kenneth N. , Carlson Rolf
Published: October 2005

The goal of this project is to create natural-sounding synthetic consonant-vowel syllables for presentation to aphasic patients and normal controls in studies of perception of speech sounds and lexical access. Of particular interest are the manner distinctions that appear to form the basis for the processing of other phonetic dimensions by human listeners. Continua of syllabic-nonsyllabic, sonorant-obstruent, continuant-noncontinuant, and voiced-voiceless sounds were constructed using the KLSYN88 synthesizer. The endpoint stimuli were synthesized based on theoretical models of glottal and turbulence noise sources and vocal-tract filtering, with some refinements to match the characteristics of a particular speaker. Intermediate stimuli were created to form continua that represent incremental changes in the synthesizer parameters. For all stimuli, the values of synthesis parameters modeled utterances that could be produced by a human talker. Identification functions for these continua for normal listeners showed relatively sharp boundaries between phonetic categories. The acoustic characteristics of the stimuli in the vicinity of the boundaries were examined to determine the pattern of acoustic attributes responsible for the abrupt change in identification, such as rise times of amplitudes, rates of change of formants, and relative amplitudes of noise and glottal excitations. [Work supported in part by NIH grants DC00776 and DC00075.]
Improvement of synthetic speech quality through syntactic information
Authors: Shimizu Tohru , Yamamoto Seiichi , Higuchi Norio , Kawai Hisashi
Published: October 2005

Many words in Japanese have identical written expression but different pronunciation. Natural synthetic speech therefore requires selection of the correct pronunciation for words and optimized prosodic features, including accent position and level, sentence intonation and length of pause, through the use of syntactic features. This paper describes (1) a new method of determining phrase accent level, based on accentual phrase boundary location and compound word structure, and (2) a newly proposed syntactic class of phrase boundaries. The results of the automatic determination of pronunciation, and opinion tests of intelligibility and naturalness are also described. About 10 000 words are assigned to syntactic and semantic features to determine correct pronunciation, representing about 20% of the total vocabulary. Pronunciation of 99% of the words in a Japanese economic daily were correct, and naturalness of the synthetic speech was 1.1 grades higher under the five-grade opinion test.
Reliable glottal-closure-instant (GCI) estimation from short analysis frames
Authors: Nathan Krishna S. , Silverman Harvey F.
Published: October 2005

It is well known that the first formant is maximally excited at the instant of glottal closure. Therefore, it is natural to utilize the energy in a band containing the first formant as a cue to the GCI. In practice, however, the actual GCI lies a few samples prior to where this energy signal attains a local maximum. Moreover, such an estimate makes no use of any period information regarding the GCI's. Consequently, secondary excitations within a period can lead to spurious GCI's. It is therefore proposed to augment the information contained in the first formant with the linear prediction error. Although, prediction error has been widely used for pitch determination, it is not sufficient to locate the GCI reliably because of ambiguities arising from multiple peaks, especially for vowels like /u/ (as in foot). Interestingly, these experiments have shown that secondary excitations tend to result in peaks in the residual error signal at locations different from those in the formant energy signal. Furthermore, in the absence of spurious excitation, the residual error can contain valuable independent period information. Therefore, the product of these two signals yields accurate GCI estimates. Such an algorithm has been tested on all vowels in a variety of environments and has been found to be very robust. Analysis frames as short as 5–10 ms have been used.
A high-order adaptive integration method for wave propagation in range-independent fluid-solid media
Authors: Ivansson Sven , Karasalo Ilkka
Published: October 2005

A high-order, adaptive method is described for computing the wave field in a laterally homogeneous fluid-solid medium by Henkel-transform integration. A technique for numerical quadrature is used, where trapezoidal or Filon sums obtained with several step sizes are combined by polynomial or Bulirsch-Stoer rational interpolation to increase the order of convergence and to obtain error estimates. This technique is combined with adaptive interval halving, maintaining a hierarchy of subintervals, meshes, and function values in a stack to eliminate duplicate function evaluations. Computational results from an underwater acoustics application are presented, showing impressive gains in efficiency and accuracy in comparison to traditional nonadaptive methods. Wave-field computations with tight accuracy demands are of interest, specifically in the context of benchmark calculations and program verification. With the method presented, about five additional correct digits are obtained by increasing the computational work by a factor of two. Of particular interest is the observation that the Filon technique seems really attractive only in conjunction with the adaptive approach.
Simulating acoustic fields with a lattice gas model for waves
Authors: Numrich S. K. , Krutar R. A. , Squier R. K. , Pearson J.
Published: October 2005

Lattice gas models have been useful in simulating complicated field behavior and are particularly well suited to take advantage of massively parallel computer architectures. As an alternative to the traditional computational methods used in acoustics, a lattice gas model based on the wave equation has been implemented on a Connection Machine and used to simulate acoustic phenomena. The model has been successful in simulating independently driven point sources, functioning singly, as pairs and arranged in both traditional line arrays and a variety of alternative configurations. The implementation of the model can also handle rigid and pressure release boundaries as well as changes in sound speed. Both scattering and propagation are directly computed in the same model. Once a phenomenon, a boundary condition or sound speed change, has been correctly modeled, it can be placed at any point or in any area anywhere in the field. The model then produces the time evolution of the pressure field everywhere in the modeled region. The results are shown as video tapes of that time evolution or snapshots of the entire field at some instant of time. [Work supported by ONT.]
Stability analysis of a higher-order time-domain paraxial approximation
Authors: Orchard B. J. , Siegmann W. L. , Jacobson M. J. , Habetler G. J. , Collins Michael D.
Published: October 2005

The global and local stability of an nth-order time-domain paraxial approximation (TDPAn) to an acoustic wave equation [M. D. Collins, J. Acoust. Soc. Am. 86, 1097–1102 (1989)] is resolved. An operator splitting technique and the Trotter product formula are used to determine the conditional (i.e., parameter dependent) stability of the complete paraxial operator from the stability of the individual diffractive, refractive, and dissipative components. The local stability of a finite difference implementation of the TDPAn is analyzed using Von Neumann and matrix methods. The Von Neumann analysis, which provides a necessary (but not sufficient) stability condition, suggests that the algorithm is unconditionally stable. The matrix method provides two requirements. A necessary condition for stability on the spectral radius of the amplification matrix W is unconditionally satisfied. However, a sufficient condition on the norm ‖W‖2 is only conditionally satisfied. Consequently, the parameter and step-size values required for use of the algorithm are determined. These results are illustrated with numerical examples, and implications for use of the TDPAn are described. The TDPAn marches the solution in range. A similar stability analysis shows that an analogous algorithm that marches the solution in time is unstable. [Work supported by ONR.]
Predictability of acoustic intensity in shallow water at low frequencies using parabolic approximations
Authors: Cederberg R. J. , Seigmann W. L. , Jacobson M. J. , Carey W. M.
Published: October 2005

The accuracy of predictions for acoustic intensity in shallow water from parabolic approximation models are carefully examined. First, accuracy comparisons are made between analytic solutions to the Helmholtz equation and parabolic equations for propagation in a Pekeris waveguide. The parameter dependencies of the interference patterns for frequencies below 100 Hz are described. Calculations from the IFD implementation of parabolic equations are also compared with the analytic solutions. Agreement between the analytical and numerical results is very good, providing that appropriate initial conditions are employed. Sensitivities to input parameters are examined by observing the variations in the predicted fields and intensities as the parameters are changed. The parameters include those specifying the depth and range properties of the geoacoustic bottom, sound-speed profile, and spatial features of the waveguide. Magnitudes of parameter variations are selected consistent with a recent Hudson Canyon experiment. Comparisons of the experimental results with model predictions are discussed. One conclusion is that input parameter uncertainties, even though relatively small for this experiment, can in some cases significantly affect the predictions. [Work supported by ONR.]
Binaural measurement analysis of performing arts spaces
Authors: Bray Wade R.
Published: October 2005

Several performing arts halls are evaluated with a measurement-compatible calibrated dummy-head system and a digital binaural acoustic analyzer. Binaural impulse responses are taken and edited in the time domain, dissonant harmonic structures and their resulting beat-frequency effects in the range below 100 Hz are measured in one hall having a high perceived level of low-frequency noise not in keeping with the NC measurement in the same space. Immediate A/B comparisons for listening juries are made of symphonic sound with different stage conditions, as heard in different seats in the house, and compared using three-axis spectrographic measurement. Panel absorptions, a cavity resonance, loudspeaker tonal colorations, and other effects perceived by human hearing are measured and corrected.
Experimental measurements of auditoria acoustic quality
Authors: Cocchi A. , Fausti P. , Garai M.
Published: October 2005

This paper illustrates an original implementation of Ando's theory for the evaluation of the acoustical characteristics of concert halls. In most cases, preliminary research is carried out on physical scale models in order to identify the temporal distribution of the various reflections into the room, or using a ray tracing program which can also compute other important acoustic descriptors. The following measurement procedure inside the hall is completely automatized: The data are acquired via an artificial head carrying two microphones in the place of the ears; the head is linked to a two-channel FFT analyzer that performs a digital analysis of the signals under control of a microcomputer that also completes some parts of the computation. This fast, in situ elaboration of the data, make it possible to carry out in a short time many measurements in different points of the hall and to obtain for each of them the four parameters of the Ando's theory (IACC, ITDG, Tsub, LA). From these values, a preference index can be determined for each point inside the room. The above mentioned techniques have already been used to qualify and to compare different kinds of theatres and auditoria.
Analytical and experimental results for scattering of ultrasound by surface-breaking cracks
Authors: Achenbach J. D.
Published: October 2005

Mathematical modeling of ultrasonic wave scattering provides valuable quantitative information for methods to detect and characterize cracks. Even though both the geometrical configuration and the process of ultrasonic wave propagation must be simplified, the characteristic features of the scattering phenomenon can be maintained. Results obtained by the modeling approach aid in the design of efficient testing configurations, as well as in the interpretation of experimental results and field data. Once a mathematical model has been verified by comparisons with a sufficiently wide range of experimental data, representative synthetic data can be generated with little effort. This is useful for the generation of a knowledge base for an expert system and for the development of data to train a neural network. The analytical results presented here for surface breaking cracks have been obtained by the use of the boundary integral equation/boundary element method. Since the elastodynamic Green's function is for an elastic half-space is complicated, it was found advantageous to use the full space Green's function. The use of that function implies that the system of boundary integral equations includes equations over the free surface of the half-space. The calculated results show excellent agreement with experimental results that will also be presented. [Work supported by ONR.]
Wave propagation and scattering in chiral elastic media
Authors: Varadan Vijay K. , Varadan Vasundara V.
Published: October 2005

Optical activity is exhibited by media whose molecular configurations are handed or chiral. Since the geometry is the basis for chirality, it can be probed by transverse waves, but not by longitudinal waves. Composite elastic media can also be made chiral because the elastic field in solids consist, in general, of both longitudinal and transverse components. The displacement field u in such isotropic, noncentrosymmetric (chiral) elastic solid has to be supplemented by the independent microrotation field φ. Six different wave numbers are possible in chiral solids. Of these, two represent longitudinal fields and the remaining four are circularly polarized. Composites can thus be tailor-made by suitably designing the microstructure and volume fraction of chiral elements. In this talk, the theoretical foundation for wave propagation and scattering in chiral elastic solids will be outlined. Pertinent experimental results on scattering of acoustic waves by chiral elastic composites containing piezo-chiral elements will also be presented.
Transient and steady-state scattering of acoustic waves from elastic objects in fluids, and of elastic waves from inclusions in solid media—Direct and inverse scattering aspects
Authors: Gaunaurd G. C.
Published: October 2005

This paper considers scattering problems associated with: (a) the simpler case of acoustic wave scattering by an elastic body in a fluid, and (b) the more complex situation of elastic waves scattered by a spherical (fluid or elastic) inhomogeneity in a solid host medium. The analysis is first presented in the frequency domain, in general, for all frequencies. Later, particular emphasis is given to the midfrequency range: 5 ≲ ka ≲ 25, which coincides with the “resonance region” of impenetrable scatterers. It is in this region that a number of simplifying approximations valid at low or high frequencies do not hold and the analysis is hardest. The above two cases were the ones originally treated by the RST. Since there are also resonances in the high-frequency region and in the Rayleigh region (ka ≲ 5), the concept of “resonance region” has to be broadened for penetrable scatterers. However, resonances in the Rayleigh region have relatively simple (viz., either multipole or curvature) origins that will be reviewed here. The analysis is then extended (still direct scattering) to the time domain. The target's transient responses to selected types of incident pulses are computed, measured, and interpreted. Finally, selected aspects of the inverse scattering problem are considered. Also examined (in various cases) is how certain features in the target's time or frequency “signature” are related to specific physical target characteristics (viz., shape, composition,…) that permit its remote and unambiguous classification. [Work supported by ONR and NSWC.]
Application of elastomeric material to the reduction of turbulent boundary layer pressure fluctuations
Authors: Ko Sung H.
Published: October 2005

Turbulent boundary layer pressure fluctuations can be reduced by either spatial filtering through the use of a finite hydrophone or a hydrophone array or by filtering through direct path attenuation. In general practice, various configurations of hydrophone arrays are embedded within a layer of elastomer, thus reducing the turbulent boundary layer pressure fluctuation. The direct path attenuation depends on the elastomer layer thickness, the shear wave speed, and the loss factor associated with the shear wave in the elastomer layer. In the filtering process, the mechanism that controls the direct path attenuation is most important. The theoretical model considered in this paper is a plane elastomer layer backed by an infinite plate with finite thickness; the other side of the layer is exposed to turbulent flow. A theoretical analysis is presented for the development of the transfer function that determines the amount of direct path attenuation. The results presented are numerically calculated transfer functions and noise reductions for various parameters related to direct path attenuation.
Carleen: An appreciation
Authors: Weinreich Gabriel
Published: October 2005

Carleen Hutchins' own accomplishments, as well as the work she has stimulated others to do, not only throws much light on the nature of the art/science interface but also helps to illuminate the riches that can be mined on both sides of it.
New aspects of the violin vibrato
Authors: Meyer Jürgen
Published: October 2005

Usually the vibrato played on a violin is considered as a frequency modulation caused by the rolling motion of the touching finger; typical values are about 4.5–8 Hz for the vibrato frequency and up to ±40% and even more for the width of the vibrato. But the high number of more or less sharp resonances of the violin leads to an amplitude modulation of the partials too. Because of the unharmonic positions of these resonances some overtones are modulated in phase and other ones in antiphase. At higher frequencies individual partials fluctuate over the peak of a resonance or through the gap between two resonances and show an amplitude modulation of twice the vibrato frequency. When lower partials fluctuate in the order of 6 dB, components about 5000 Hz may reach an amplitude modulation of 20 dB or in extreme cases up to 35 dB. Because of the directivity these values depend on the direction of sound radiation, too. It may be a criterion for the sound quality of a violin, whether there are such enormous fluctuations or not. In larger rooms reflections having different delay times average the amplitude modulation and lead to filled frequency bonds for the partials.
The linear and nonlinear vibrations of a stretched string and the relevance to stringed musical instruments
Authors: Gough C. E.
Published: October 2005

For small amplitudes of string vibration, the modes of a stretched string are shown to be equivalent to the normal modes of a coupled oscillator problem, the coupled oscillators being the string itself and the vibrational modes of the body on which the string is supported. The coupling at the bridge splits the degenerate modes of the ideal string, with a degree of perturbation that depends on the strength of the coupling and the damping of the various modes involved. Under extreme conditions this can lead to a splitting of the modes resulting in the famous wolf-note on bowed instruments, which was first studied by Raman and later by Schelling. At large amplitudes, the nonlinear coupling of the orthogonal transverse modes will be shown to result in a precession in the plane of polarization of the now elliptically polarized transverse modes, which could lead to variations in amplitude of emitted radiation of any stringed instrument. In this talk, the theoretical predictions for both linear and nonlinear string vibrations will be briefly outlined and measurements will be described for idealized experimental situations and for instruments of the violin family.
Observatious during a design and test program for bowed instrument strings
Authors: Pickering Norman C.
Published: October 2005

During the past 3 years, the author has participated in a program to review and redesign the entire bowed string line of a major manufacturer, using new materials and manufacturing techniques in addition to traditional designs and methods. Computer programs have been created, both for design and for control of quality. In testing hundreds of strings, some anomalies have been seen, including persistent whirl modes and variation of frequency and damping with amplitude. Attempts have been made to ascertain whether such conditions may affect musical performance. The action of rosin has been studied, and temperature at the bow-string interface measured with a calibrated infrared video camera. The greatest difficulty has been correlating opinions of musicians with actual measurements, a problem that is not unexpected in musical acoustics.
Hearing loss compensation from the worker viewpoint—Legal aspects
Authors: Lawson M. Juliet
Published: October 2005

Workers in the United States who are employed by individuals not engaged in maritime work can recover for occupational hearing loss under state worker's compensation statutes. If the employer is a maritime employer, the worker can recover under the federal Longshore and Harbor Worker's Act for occupational hearing loss. The worker may also have several causes of action against the manufacturer of the product or products that he used or worked around. The worker may allege that the manufacturer was negligent and breached a duty to the claimant to exercise the highest standard of care in the manufacture of its products and/or the worker may claim that the manufacturer is strictly liable for any damage that the worker suffered because the product was distributed in a defective condition unreasonably dangerous to intended and foreseeable users or bystanders. There may also be a claim for breach of an implied or express warranty of fitness and merchantability.
On the normal modes of free vibration of inhomogeneous and anisotropic elastic objects
Authors: Visscher William M. , Migliori Albert
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 resonant frequencies of a variety of anisotropic elastic objects, including spheres, spheroids, ellipsoids, hemispheres, cylinders, eggs, shells, bells, sandwiches, cones, pyramids, prisms, tetrahedrons, octahedrons, and potatoes. The paramount feature of the present calculation, which distinguishes it from previous ones, is the choice of products of powers of the Cartesian coordinates as a basis set for expansion of the displacement, enabling us to analytically evaluate the required matrix elements for these systems. This algorithm will allow a general anisotropic elastic tensor with any position dependence and any shape with any density variation. A number of plots of resonance spectra of families of elastic objects as functions of relevant parameters will be shown, and the measured resonant frequencies of a precision machined but irregularly shaped sample of aluminum (called a potato) will be compared with its computed normal modes. Possible applications to problems in materials science and in seismology will be mentioned. [Work supported by USDOE.]
Changes in open and speed quotient values as a function of measurement criteria
Authors: Sapienza Christine M. , Stathopoulos Elaine T. , Dromey Christopher
Published: October 2005

Noninvasive measures of vocal-fold activity have become useful in describing normal and disordered voice production. Specifically, open and speed quotient measures (OQ and SQ) of electroglottographic and inverse filtered airflow waveforms have been used to describe variability in the phases of vocal-fold vibration. Unfortunately, there is little consistency in the criteria used to calculate these quotients. The lack of consistency becomes important when comparing quotient values from similar waveforms (e.g., VFCA waveform) as well as different types of waveforms (e.g., VFCA versus glottal airflow). Four different percentage criteria were chosen to investigate how quotient values change within and across signal types. Twenty percent, 50%, 80%, and 100% of the ac peak-to-peak amplitude of electroglottographic and glottal airflow waveforms were selected. Results indicated different values obtained across criteria levels. Comparison of absolute values from quotient data across criteria or signal type is not recommended. Use of common measurement procedures is needed so that normative data can be established. ]Work supported by NIH ♯DC00516-42.]
A phase cancellation method for tinnitus
Authors: Judd M. D. , Unäl A.
Published: October 2005

Tinnitus is an intrinsic feedback noise generated within the inner ear. Objective tinnitus is the kind in which a sound field does exist in the outer ear canal. Recent findings on the objective tinnitus problem strongly suggest that the signal(s) emanate from damaged sensor hairs inside the cochlea. The ringing, or noise, that the patient “hears” is most likely the firing of neighbor sensor hairs, due to the damaged sensor. Thus these neighbors comprise some signal bandwidth over which the patient detects the ringing. In the greater number of patients, this phenomenon is diagnosed as due to a single tone. Current signal methods used to mask the tone, or noise, emanating from the cochlea typically employ wide bandwidth signals that overlap more than the full bandwidth of the tone (or noise). These methods inherently create noise in themselves and do little to remove the signals being generated from the inner ear. This paper presents a simple viable method to cancel a single tone, in the local region of the damage sensor, in the cochlea.
The effects of noise on the measurement of the 2f1−f2 otoacoustic emission
Authors: Harrell Richard W. , Feth Lawrence L. , Melnick William
Published: October 2005

The effects of noise exposure on the measurement of the cubic distortion product emission (2f1 − f2) were measured. TTS was induced using white noise presented at four intensities, each for three different time periods, giving a total of twelve conditions. The subjects were normal-hearing adults. The trial conditions were randomized, with an appropriate rest period between each condition. The amount of temporary threshold shift (TTS) in dB was obtained by comparing pre- and post-noise pure-tone thresholds for the 500-Hz to 8-kHz range by octave. The level of 2f1 − f2 was measured prior to and immediately following the threshold testing. Changes in the distortion product emission were determined by comparing pre- and post-noise emission measures. Preliminary results suggest that noise exposure may reduce the level of the distortion product emission. The degree to which this effect was seen appeared to be related to both intensity and duration of the noise exposure.
Importance and generality of various sound assessment criteria. I. Naive listeners
Authors: Smith Kim M. , Letowski Tomasz
Published: October 2005

A series of criteria and their definitions has been developed describing auditory image attributes that are felt to be important in sound quality assessment. These criteria were presented to two matching groups of 25 naive young listeners. Group I read the definitions for each criterion and then rated the attributes on two, five-point scales: (1) an importance scale and (2) a generality scale. Group II rated each criterion on the same scales, but they did not read any definitions. The same 50 listeners were retested under identical conditions. The following results will be discussed: (1) importance and generality of various criteria, (2) differences between groups, (3) differences between test and retest data, and (4) application of results for future research.
Aging and discrimination of interaural time differences
Authors: Ashmead Daniel , Tetzeli Marta , Chandler David , Thomas Amy
Published: October 2005

Discrimination of interaural time differences (ITDs) was compared between ten younger adults (18–24 years) and ten older adults (66–80 years, with normal or near-normal hearing). Both the mean thresholds and standard deviations for older adults were elevated approximately fourfold compared to the younger subjects. The age difference is consistent with previous reports of age-related loss in sensitivity to ITDs. However, in our study and in previous studies, results may have been confounded by a methodological factor. The older adults had very large excursions across stimulus levels in the adaptive (staircase) psychophysical procedure used. Thus the age difference may reflect attentional as well as auditory factors. Further research using the method of constant stimuli in a small number of older adults is in progress. Preliminary results indicate that there is still an age difference in interaural processing, but that the difference is smaller than methods using the adaptive procedure have indicated. The findings have implications not only for age-related changes in interaural processing, but also for the use of psychophysical testing methods with older adults.
Scattering matrix and boundary integral equation methods for long-range propagation in an acoustic waveguide with repeated boundary deformations
Authors: Dawson Trevor W.
Published: October 2005

Boundary integral equation methods (BIEM) provide an accurate model for predicting the scattering of acoustic radiation from compact deformations of the walls of a waveguide. In numerical implementation, however, the denseness of the resulting coefficient matrix inhibits the modeling of scattering over very extensive deformations. It is shown in this paper how scattering matrix methods can be combined with BIEM to model long-range propagation in a two-dimensional range-dependent waveguide. The extension to three-dimensional sources is also indicated.
Scatter of subsonic waves on a fluid-loaded cylindrical shell from an internal obstacle
Authors: Smith P. W.
Published: October 2005

An axisymmetric subsonic wave on a thin, fluid-loaded cylindrical shell of infinite extent impinges on a “shear diaphragm,” which constrains the normal velocity to vanish locally by the action of a ring force. The energy scatter coefficients (wave transmission, reflection, and sound radiation) have been evaluated, as well as the directional radiation source strength for a ring-force source. Results are presented for parameters appropriate to steel and water in the frequency range around the in-vacuo ring resonance frequency. The wave passes the obstacle nearly undisturbed at low frequencies (ka < 1.5, where a is the radius and k is the sound wave number). At high frequencies (ka > 2.5) the wave is largely reflected, behaving asymptotically like a flexural wave on a flat plate of the same thickness as the shell, with fluid on one side.