bluuebunny/crossref_metadata_2025 huggingface dataset:
The response of acoustic measurements to anthropogenic climate change
Authors: Dzieciuch Matthew A.
Published: October 2005

Anthropogenic CO2 in the atmosphere is expected to result in increased ocean heating. The output of a coupled ocean-atmosphere general circulation model was used to simulate to expected climate change scenario. The model was run with no CO2 increase and with CO2 doubling. The spatial properties of the CO2 signal are nonuniform and show that heating is not confined to the ocean surface. The ambient climate variability shows a different spatial structure that is more emphasized at the surface. The GCM output was then used as an input to an acoustic propagation model. The acoustic time series can then be analyzed for climatic trends. The control run is used to estimate the ambient noise processes on long-term scales. Maps of the anthropogenic signal to the ambient noise ratio of the climate system can then be constructed. Acoustic thermometry measures integrals of heat content through these maps. A network of sources and receivers can then be designed to efficiently monitor anthropogenic climate change. Work is in progress to compare the efficiency of different measurement systems such as satellite altimeters, drifters, and traditional measurements to that of acoustic thermometry.
Stochastic modeling and global warming trend extraction for ocean acoustic travel times
Authors: Bottone Steven , Gray Henry L. , Woodward Wayne A.
Published: October 2005

A possible indication of the existence of global climate warming is a negative trend for the travel time of an acoustic pulse along a fixed long path, or paths, in the ocean over a period of many years. Statistical methods for determining whether a significant long term trend is present in a given set of time series data of acoustic propagation times have been developed and, for illustration, applied to some specific travel-time time series generated by the MASIG and GFDL ocean models. For the multiple path case, line + noise models, where the noise is modeled as a multivariate autoregressive (AR) process are considered. It is shown that the time necessary to detect the presence of a warming trend in a time series for a single path is reduced by considering time series for multiple paths. [Work sponsored by ARPA.]
Are faster than predicted arrival times seeing Arctic Ocean warming?
Authors: Mikhalevsky Peter N. , Gavrilov Alexander , Baggeroer Arthur B.
Published: October 2005

Arrival times of M sequences transmitted across the Arctic in the spring of 1994 during the trans-Arctic acoustic propagation (TAP) experiment [P. N. Mikhalevsky, 2851(A) (1994)] are faster than modeled arrival times using historical climatology. The modal dependence of the travel times appears to be consistent with a warming of the Atlantic intermediate water (AIW) in the Arctic Ocean. Calculations of the effects of this type of climate change signal, as well as ambient variability on the modal arrival times, will be presented. The possibility that the TAP results are consistent with new reports of AIW warming in the Arctic [Carmack etal., Geophys. Res. Lett. (in press) and K. Aagaard and E. C. Carmack, Science 266 (23 December 1994)] will be discussed. [Work supported by ONR, ARPA, and the Ministry of Science, Russian Federation.]
Long-distance low-frequency modal propagation into the Lincoln Sea
Authors: Pawlowicz Rich , Farmer David M. , Sotirin Barbara , Sozard Siobhan
Published: October 2005

One-Mm transmissions from the April 1994 trans-Arctic acoustic propagation (TAP) experiment recorded by a vertical line array deployed from an icecamp at the edge of the continental shelf in the Lincoln Sea are analyzed. The received phase is astonishingly stable, and appears to vary mainly with source/receiver motions. Travel times determined from M-sequence transmissions are less stable and are not consistent with the phase measurements. Modal decomposition shows that bottom effects strip out the higher-order modes as sound propagates onto the shelf. The amplitude of the surface-trapped first mode is also weaker than predicted by standard loss mechanisms. Some implications of this analysis for the design of future Arctic low-frequency tomography experiments are discussed.
Use of simplified coupled mode propagation for the prediction of impulse responses of megameter trans-Arctic propagation paths
Authors: Freese Herbert A.
Published: October 2005

In the spring of 1994, a long-range propagation experiment was conducted in the Arctic during which large time-bandwidth product signals (M sequences) were transmitted to two receiver sites. These data were processed to extract the pulse response of the propagation channel at the vertical arrays at each site and a horizontal array at one of the sites. These data are being used for an assessment of the utility of Arctic acoustic measurements for global warming signature detection and monitoring. A critical part of this measurement is the identification of the observed paths with specific propagating modes. A method has been developed based on coupled normal modes which allows us to estimate pulse responses quickly. The results agree favorably with the experimental data when historical environment data are used as the model inputs. The modeling methods used, comparisons with the measurements and implications, as well as the impact on sound speed accuracy required, will be discussed.
On the feasibility of modal group delay-based tomography in the deep ocean
Authors: Brown Michael G. , Viechnicki John
Published: October 2005

The modal description of sound propagation in deep ocean environments is considered. Several recently published inversion algorithms have assumed that modal group time delays can be measured. Such a measurement requires that the frequency bandwidth: (1) be sufficiently broad that successive modal arrivals are resolved in time, and (2) be sufficiently narrow that, across the band, the group slownesses of neighboring mode numbers do not overlap. These conflicting requirements can be reconciled only at long range. In the deep ocean, the late arriving, low-order modes are most likely to satisfy condition (2). Unfortunately, recent measurements and numerical simulations suggest that these modes are susceptible to internal wave-induced mode coupling—especially at long range. The following pessimistic conclusion is made: Modal group delay-based inversion schemes can be applied to measurements of acoustic wavefields in the deep ocean only for a carefully selected choice of experimental parameters (range, center frequency, and bandwidth) which may not be experimentally accessible. [Work supported by ONR.]
Frequency interpolation method for increasing speed of long-range broadband parabolic equation (PE) calculation
Authors: Heaney K. D. , Kuperman W. A.
Published: October 2005

An interpolation method that increases the speed of broadband range-dependent calculations by an order of magnitude using the parabolic equation has been developed. By decomposing the vertical field into complex modal amplitudes, interpolation across frequency is possible. The method was designed to be used in Monte-Carlo studies of the effects of internal waves. Signal processing algorithms are being developed to extract the deterministic signal from the internal wave noise. The method has been benchmarked against the fully broadband PE for several ocean environments. The results are in good agreement with the PE for 1000-km propagation through internal waves and for 3000-km mildly varying ocean environments. The reproduction of the internal wave effects in the SLICE89 experiment reported by Colosi [Colosi etal., 452–68 (1994)] has also been possible. Frequency interpolation predictions of the ATOC Acoustic Engineering Test will be presented and compared with preliminary results from the experiment. In particular, simulation of the statistics of the internal wave effects as measured in the Acoustic Engineering Test is of main concern.
Biophysical properties of a tactile mechanoreceptor: The Pacinian corpuscle
Authors: Pietras B. W. , Bolanowski S. J.
Published: October 2005

The Pacinian corpuscle is a tactile mechanoreceptor composed of a neural element surrounded by a multilayered, fluid-filled accessory capsule. Receptor potentials recorded from isolated Pacinian corpuscles in response to sinusoidal vibrations have nonlinear, asymmetric full-wave rectified transfer functions. The frequency response is U-shaped with a best frequency near 300 Hz. The Pacinian corpuscle’s accessory capsule was studied experimentally and modeled theoretically to determine its mechanical contribution to the observed physiological response. Measurements of reactive force in response to sinusoidal compression showed that the reactive force is linear, and increases with frequency and amplitude. The compressive force can be described by a first-order linear differential equation of the form f(x,t)=kx+cdx/dt. Interlamellar fluid velocities and lamellar displacements were also computed for a range of frequencies. Computational simulations of the interlamellar fluid flow in response to sinusoidal displacement of the surface of the capsule shows that the multilayered structure linearizes the interlamellar fluid velocity, thereby linearizing the interlamellar compressive force. Thus both the mechanical filtering by the accessory capsule and the electrodynamical properties of the neurite contribute to the nonlinear, physiological response profiles seen in the receptor potential. [Work supported by NSF, IBN-9211561.]
Tactile perception with haptic displays
Authors: Weisenberger Janet M.
Published: October 2005

Tactile sensing of objects and surfaces is typically accomplished via movement of the hand or fingers relative to the object being sensed, a mode known as haptic touch. Despite this fact, most previous work on the tactile response to complex vibratory stimuli has employed stationary displays. Although pattern movement can be simulated on these displays, kinesthetic feedback from active movement of the hand is absent. The present paper describes a series of studies employing a haptic vibratory display for the index fingertip that can be moved across a surface to encounter and scan virtual stimuli, thus preserving kinesthetic feedback. Experiments comparing this haptic scanning mode to stationary display modes showed a significant superiority of haptic scanning. However, most of this advantage was attributable to the ability to scan patterns repeatedly and from multiple directions, and not to haptics perse. Further experiments examined whether reductions in the display’s field of view could be compensated by haptic scanning. Dramatic reductions in the field of view showed minimal decreases in performance when haptic scanning was employed. Results are discussed in terms of the role of haptics in tactile sensing and implications for the development of tactile displays. [Work supported by Systems Research Laboratories and ASFOSR.]
Cortical plasticity and representation of spatially temporally distributed tactile stimuli
Authors: Wang Xiaoqin , Merzenich Michael M.
Published: October 2005

An important property of the cerebral cortex is its ability to reorganize itself in response to changing sensory environment throughout life. Representational ‘‘maps’’ of skin surfaces in the primary somatosensory cortex (SI) are remodeled after many forms of input alteration. Two questions were addressed in our recent plasticity experiment: Under what specific conditions are spatially distributed and time-varying sensory inputs (a) integrated, or (b) segregated in their representations by the dynamic mechanisms underlying cortical function? The results showed that the topographic map of skin surfaces in SI was dramatically remodeled in adult owl monkeys trained to discriminate two tactile stimuli applied to distal and proximal segments of their fingers in alternation. Subsequent mapping of area 3b revealed neural responses with either distal or proximal multiple-digit receptive fields, reflecting cortical integration of inputs from temporally coincidentally excited skin surfaces. By contrast, the cortical representations of temporally noncoincidentally stimulated skin surfaces were segregated from each other. These findings directly demonstrate that for learning induced plastic changes in cortical topographic maps, afferent input integration and segregation are dependent on stimulus coincidence, and that regularly practiced hand use results in a representation of its sensory surfaces in the brain that reflects that specific use.
Influences of pain and learning on vibrotaction
Authors: Bolanowski Stanley J. , Maxfield Lisa M. , Hall Karen L. , Makous James C.
Published: October 2005

The parallel processing of tactile information by independent channels as defined psychophysically, physiologically and anatomically has been amply described in the literature. For a unified percept to occur, however, information carried by these separate channels must be combined centrally. Furthermore, the unified percepts are affected by submodality interactions, such as the gate theory of pain whereby tactile stimulation suppresses pain, and cognitive factors (e.g., attention). Several series of experiments are presented showing that painfully hot and cold stimuli can substantially diminish vibrotactile sensation, but only when co-localized with the tactile stimuli. The effect occurs regardless of the tactile channel activated. This tough-gate acts oppositely to the pain gate and indicates centrally located touch–pain interactions. The results of additional experiments show that training of observers in an intensity-discrimination task can significantly affect the ability to distinguish differences in vibrotactile intensity. This learning effect appears to be bilateral and affects intensity as well as spatio-temporal perceptions of tactile stimuli. The effect indicates that high-level cognitive functions can influence tactile perceptions; the neural basis for these perceptions are presumably located at the cortical level.
The effects of the intensity and duration of a masking stimulus, Δt, and signal duration on vibrotactile forward masking
Authors: Gescheider George A. , Santoro Kristine , Makous James C. , Bolanowski Stanley J.
Published: October 2005

Vibrotactile thresholds were found to increase as a function of the duration and intensity of a forward masking stimulus and to decrease as a function of the time interval between the termination of the masking stimulus and the onset of the signal (Δt) and signal duration. The effects of the intensity and duration of the masking stimulus were similar for both the P and NPI channels as indicated by the nearly identical results measured at 250 and 20 Hz. The observed declines in threshold as a function of Δt and signal duration were both attributed to an increase in the time interval between the offset of the masking stimulus and the offset of the signal.
Response to ‘‘Comments on ‘The hydroacoustics of a raindrop impact’ ’’ [J. Acoust. Soc. Am. 97, 3184–3187 (1995)]
Authors: Nystuen Jeffrey A.
Published: October 2005

Two components of the underwater pressure signal of a raindrop impact are identified. An initial single cycle impulse lasting less than 0.1 ms is attributed to an acoustic ‘‘water hammer’’ of the raindrop onto the water surface. The second feature, a ‘‘plateau’’ pressure signal with a time scale over 1 ms, is associated with the nearly incompressible hydrodynamic flow of the drop splash. The radiated sound field from the impacts is dominated by the impulse component and produces a broad spectral peak near 15–20 kHz as previously reported.
Lamb’s problem for an anisotropic half-space studied by the Cagniard de Hoop method
Authors: Mourad A. , Deschamps M.
Published: October 2005

The 3-D Green’s tensor is obtained for an anisotropic half-space, by using the Cagniard-de Hoop method. Some numerical results of the normal displacement field component are outlined for the cases of cubic and hexagonal symmetries. The novelty of the present approach deals with the fact that the diffraction effects related to the free surface are taken into account. The numerical method, which has been used, shows up, for instance, the diffraction of the head waves.
Structurally transmitted dynamic power in discretely joined damped component assemblies
Authors: Farstad Jerry E. , Singh Rajendra
Published: October 2005

In this paper, a formulation for computing the vibration transmitted among components joined at discrete locations is presented. The formulation is based on a component modal synthesis approach. Natural frequencies and modes of individual components subject to specific boundary conditions at joint locations are used to compute the modal properties of assemblies from a variational formulation. Lagrange multipliers are used to enforce constraints that motions of components be identical at joint locations, and the assembly forced response is obtained from the normal mode method. Since the Lagrange multipliers used to enforce the motion constraints are equal to the interfacial forces, evaluating these from the assembly response provides an efficient means for computing the dynamic forces and moments at joints and the mechanical power transmitted among components. The formulation is initially developed for proportionally damped assemblies. Because localized damping at joint locations is often the most significant source of damping in component assemblies, the modal synthesis and vibration transmission formulations are subsequently extended to structures with arbitrary viscous damping. Simple illustrative examples of proportionally damped and nonproportionally damped assemblies of lumped parameter systems are included.
Benchmark vibration solutions for regular polygonal Mindlin plates
Authors: Liew K. M. , Xiang Y. , Kitipornchai S.
Published: October 2005

Benchmark vibration solutions for thick polygonal plates of arbitrary boundary conditions are presented. The Mindlin first-order shear deformation theory is used to derive the energy functional while the pb-2 Ritz method is employed for solution. By minimizing the difference between the maximum strain and kinetic energies with respect to unknown coefficients in the pb-2 admissible functions, the governing eigenvalue equation is derived. The vibration frequencies are obtained by solving this governing eigenvalue equation. A convergence study has been carried out to verify the accuracy of these results. In the absence of existing results for thick polygonal plates, the present results where possible are compared with available thin plate solutions by setting the thickness to apothem ratio to be very small (say, t/r=0.001). Sets of first known vibration frequencies for moderately thick regular polygonal plates are presented as an enhancement to existing literature.
Statistical energy analysis and structural fuzzy
Authors: Lyon Richard H.
Published: October 2005

The concepts and derivations of the effects of a minor or secondary structure on the dynamics of a well defined major or primary structure have been recently presented as a ‘‘fuzzy structure’’ interacting with a deterministic one. On the face of it, this appears like a ‘‘halfway’’ SEA system in that one of the two systems is well defined while the other is probabilistic in the SEA sense. It is therefore interesting to see if a ‘‘full SEA’’ treatment of the system would lead to difference in, at least, some of the quoted results. The second, and more important, purpose of this paper is to relate the dynamics of potential minor structures to the properties of the ‘‘fuzzy’’ system, since these properties have been presented in some of the ‘‘fuzzy literature’’ in rather general terms.
Power flow through multidimensional compliant joints using mobility and modal approaches
Authors: Rook Todd E. , Singh Rajendra
Published: October 2005

An analytical framework, based on the refinements to the mobility and modal approaches, is proposed to calculate the structural power flow through multidimensional compliant joints or connections. The built-up assembly is divided into the classical model of a noise control problem, i.e., source, path (joint), and receiver. Both methods place emphasis on the joint properties and account for different paths and mechanisms of noise transmission (e.g., forces and moments). Only the discrete system formulation is considered and results obtained via exact (unsynthesized) and the proposed component synthesis procedures perfectly match with each other. The mobility method is found to be useful for distinguishing which path (joint) transmits power and the complementary modal method yields information on the newly defined modal dissipation efficiencies. Finally the issues of scalar versus vector joints and rigid versus compliant connections are addressed by using a pedagogical example of a 10 degrees-of-freedom system.
Analytical and experimental aeroacoustic studies of open-ended three-duct perforated elements used in mufflers
Authors: Gogate G. R. , Munjal M. L.
Published: October 2005

Perforated element mufflers have been known to have good acoustic performance, when used on automotive exhaust systems. In the last decade and a half, plug mufflers, concentric hole resonators, and three-duct closed-end perforated elements have been studied. The present investigation concerns open-ended, three-duct perforated elements, which are known to combine high acoustic transmission loss with low back pressures. The governing equations have been solved in the frequency domain, using the decoupling approach along with appropriate boundary conditions, to derive the transfer matrix and then to calculate noise reduction and transmission loss. The predicted noise reduction values have been shown to corroborate well with experimentally observed values. Finally, parametric studies have been done to draw design curves for such mufflers.
Trispectral analysis of stationary random time series
Authors: Dalle Molle John W. , Hinich Melvin J.
Published: October 2005

This paper investigates the statistical properties of the trispectrum. The trispectrum is the Fourier transform of the fourth-order joint lagged cumulant of a zero-mean stationary random time series. A complete representation of the principal domain of the trispectrum derived from its inherent symmetries is detailed. The large sample variance for a consistent estimator of the trispectrum is presented and used in the development of the fourth-order generalizations of the bispectrum-based Hinich tests of Gaussianity and linearity. A test for stationarity is developed using an amended version of the trispectrum-based test of Gaussianity. An arithmetic frame-averaging procedure is used to compute consistent trispectral estimates for a zero-mean bandlimited real-valued stationary random process. The trispectral-based tests are applied to time series of ship noise recorded by a sonobouy in the Eastern Atlantic Ocean.
Orthotropic piezoelectric properties of the cochlear outer hair cell wall
Authors: Tolomeo J. A. , Steele C. R.
Published: October 2005

The mammalian outer hair cell has been shown to possess significant coupling between mechanical and electrical properties. This electromotile property may play a key role in cochlear tuning. In order to characterize quantitatively the electrical and mechanical behavior, the cell wall is modeled as a thin linear elastic piezoelectric material. Experimental findings from several investigators are used to determine the mechanical and electrical generalized stiffness coefficients described by the model. The model analysis indicates that orthotropic mechanical properties in the plane of the cell wall are required to match experimental behavior. The calculated orthotropic coefficients predict that the outer hair cell deforms due to cilia deflection with a force gain of 0.5 for perfectly constrained end conditions and a displacement gain of 3.6 for free end conditions. These values reflect the potential role of the OHC as a feedback mechanism to the basilar membrane. Results are for small deformation and quasi-static conditions with viscosity and inertial effects neglected. It is further assumed that cell permeability is negligible at the time scale of the fast deformation considered here.
Transient-evoked otoacoustic emissions and high-frequency acoustic trauma in the guinea pig
Authors: Avan Paul , Bonfils Pierre , Loth Drystan , Elbez Michel , Erminy Manuel
Published: October 2005

Transient-evoked otoacoustic emissions (TEOE) disappear when hearing loss exceeds 40 dB in the range 1–4 kHz, due to impairment of cochlear outer hair cells. Early screening of sensorineural hearing losses is based on this finding. However, little is known as to the frequency specificity of TEOE abnormalities in a damaged cochlea. TEOE were recorded in 18 normally hearing guinea pigs in a range from 1.5 to 5 kHz before and after exposure to loud pure tones (3–10 kHz, 95–105 dB SPL, 1–10 min). The thresholds of eighth-nerve compound action potentials (CAP) were monitored with a round-window electrode; it was confirmed that acoustic overexposure resulted in typical high-frequency threshold elevations (10 to 50 dB). Most TEOE components were found at lower frequencies at which CAP thresholds did not change. However, a significant linear regression was found between their amplitudes and the percentage of basal cochlea with unaltered CAP thresholds (r=0.69, p<0.0001). Two alternative hypotheses are proposed to account for this correlation. Either acoustic trauma induced some minute cochlear damage at places tuned to low frequencies and TEOE were more sensitive to it than CAP thresholds, or significant contributions to lower-frequency TEOE came from the most damaged cochlear places tuned to much higher frequencies.
Objective versus human observer detection of 40-Hz auditory-evoked potentials
Authors: Dobie Robert A. , Wilson Michael J.
Published: October 2005

Magnitude-squared coherence (MSC) was used to detect 40-Hz auditory-evoked potentials (AEPs) in a two-alternative forced-choice experiment. MSC performance was found to be better than that of ten human observers. Experienced observers did not perform better than naive observers. In a ‘‘yes–no’’ experiment, observers demonstrated large differences in criterion, with false-positive rates of 2%–20%. Observers also performed better when AEPs were presented in a 50-ms window (two response cycles) than when presented in a 205-ms window (eight response cycles), although total test time was the same; MSC performed equally well in both cases. MSC provides a useful and objective adjunct to visual detection of 40-Hz AEPs.
Auditory steady-state responses to tones amplitude-modulated at 80–110 Hz
Authors: Lins Otavio G. , Picton Peter E. , Picton Terence W. , Champagne Sandra C. , Durieux-Smith Andrée
Published: October 2005

Steady-state responses can be recorded from the human scalp in response to tones that are sinusoidally modulated in amplitude at rates between 60 and 120 Hz. For 60 dB SPL 1000-Hz tones the maximum baseline-to-peak amplitude of about 0.06 μV occurs for modulation rates between 80 and 95 Hz. The phase of the response does not change with modulation depths greater than 25% and the amplitude saturates at modulation depths greater than 50%. The presence or absence of a response can be accurately determined by frequency-domain statistics and the response becomes clearly recognizable at intensities that are 16±8 dB above behavioral thresholds. With increasing intensity the response increases in amplitude at 1.9 nV/dB until an intensity of 70 dB SPL. As the intensity increases above 70 dB SPL the response increases in amplitude more rapidly at 7.8 nV/dB (at 1000 Hz) and contains significant energy at harmonics of the modulation frequency. This second stage of the intensity function is more prominent for stimuli with lower carrier frequencies (500 more than 1000 more than 2000 Hz) and is attenuated by high-pass masking. These steady-state responses should be helpful in evaluating human auditory physiology and in objective audiometry.
Locus equations derived from compensatory articulation
Authors: Sussman Harvey M. , Fruchter David , Cable Amory
Published: October 2005

Locus equations are linear regressions of the onset of F2 transitions on their offsets. These functions vowel-normalize the F2 transitions such that they are able to characterize consonantal place categories. The purpose of this research was to determine if compensatory articulation due to bite blocks would alter the normally linear relationship between F2 transition onset and offset frequencies or alter the differential slopes and y intercepts of locus equations as a function of stop place. Six speakers, three male and three female, each produced /bVt/, /dVt/, and /gVt/ tokens for ten vowel contexts under normal and bite block conditions. Extremely linear and practically identical scatterplots were obtained in the two speaking conditions. No adaptation to the bite blocks was found when comparing locus equations derived from the initial versus the final bite block trial. Results are discussed in relation to the ‘‘orderly output constraint,’’ which postulates a perceptual function for linearly related F2 transition end points within consonantal place categories.
The effects of breath sounds on the perception of synthetic speech
Authors: Whalen D. H. , Hoequist Charles E. , Sheffert Sonya M.
Published: October 2005

When preparing to speak, talkers typically take a breath. The perceptual effect of adding naturally produced breath intake sounds to synthetic speech was examined. In experiment 1, subjects were better at transcribing synthesized sentences that were preceded by a breath sound than those that were not, in addition to the improvement due to practice that is typically found with synthetic speech. Experiment 2 found that replacing the breath with the spectrally similar sound of rustling leaves had no effect on the accuracy. Experiment 3 had breaths before randomly selected sentences. Only the practice effect was significant, though there was a tendency for sentences with the breath sounds to be remembered better. In experiment 4, we tested whether the appropriateness of the breath sound to the sentence size (relatively short or long) affected the use of the breath sound. Appropriateness had no effect, perhaps because the range of sentence durations was too small. Experiment 5 replicated experiment 1 but used leaf sounds rather than silence in the nonbreath sentences. The presence of breath was again found to aid recall. Overall, the current results indicate that adding the breath intake sound to synthetic sentences improves listeners’ ability to recall those sentences.
Some mechanical and acoustical consequences of the violin soundpost
Authors: Bissinger George
Published: October 2005

Mechanical and acoustical consequences of removal of the soundpost in the violin were examined using (a) experimental modal analysis on a violin with (SP) and without soundpost (no-SP) to examine the approximately 50 modes observed over a 0- to 2-kHz range and (b) boundary element radiation calculations of radiation efficiency and directivity for each normal mode. A majority of modes were tracked between SP and no-SP states by correlating frequency, damping, mode shape, and interviolin MAC values. On removal of the soundpost, (a) mode frequencies below 1 kHz usually dropped a few percent, while those above increased similarly, (b) average mechanical response at the bridge increased 14%, (c) average radiation efficiency dropped 17%, most noticeably from 500 to 800 Hz, especially for a very strong corpus SP mechanical mode at ∼550 Hz whose radiation efficiency dropped from 0.105 to 0.022, and (d) radiation patterns altered substantially. A vibration-radiation model to simulate response curves agreed well with general features of previous SP violin response and radiativity measurements, and with Fourier analysis of recorded SP and no-SP slide tones. Calculated SP radiation patterns were also compared to previous violin directivity measurements.
Tactile perception of ultrasound
Authors: Dalecki Diane , Child Sally Z. , Raeman Carol H. , Carstensen Edwin L.
Published: October 2005

In this investigation, acoustic radiation force was used as a stimulus to determine the threshold for tactile perception in the human finger and upper forearm as a function of frequency and pulse duration. Initially, a small (1.8-cm2) acoustically reflecting disk was affixed to the anatomical exposure site to maximize the delivered radiation force. Exposures were performed using a 2.2-MHz unfocused source modulated to produce square waves at 50, 100, 200, 500, and 1000 Hz. For the finger, maximum tactile sensitivity occurred at 200 Hz with a threshold radiation force of ∼0.4 mN. For single pulses of 1 to 100 ms at 2.2 MHz, the threshold forces were an order of magnitude greater than for continuous exposure modulated at 200 Hz. Thresholds for pulse durations of 0.1 ms were somewhat greater than for pulses longer than 1 ms. Subsequently, thresholds of tactile perception were determined for direct exposure of the upper forearm (avoiding bone) to single pulses of 2.2-MHz ultrasound. Comparison of perception thresholds with and without a reflecting material over the tissue were consistent with the hypothesis that the tactile sensation experienced when tissue is exposed to ultrasound is its response to the radiation force associated with the transfer of momentum from the sound field to the tissue medium.
The scattering of sound from a spatially distributed axisymmetric cylindrical source by a circular cylinder
Authors: Morris Philip J.
Published: October 2005

General expressions for the scattering of sound from a spatially distributed cylindrical source by a circular cylinder are given. The incident field is determined using a Hankel transform. The scattered fields are determined by matching the pressure and radial velocity at the surface of the cylinder. Examples of total and scattered pressure fields are given for a cylindrical line source and a axisymmetric source with a Gaussian spatial distribution. An example is also given for a circular disk source.
Sound radiation from two semi-infinite dissimilar plates subject to a harmonic line force excitation in mean flow. I. Theory
Authors: Wu Sean F. , Zhu Jinshuo
Published: October 2005

Formulations are derived for predicting sound radiation from two semi-infinite dissimilar plates subject to a line force excitation at the joint in the presence of mean flow using the Wiener–Hopf technique and Fourier transformations. The acoustic pressure is solved in the frequency-wave-number domain first in terms of the decomposition factors and parameters associated with displacements, slopes, bending moments, and shear forces at the joint of two plates. The decomposition factors are evaluated via contour integrations, and the parameters are determined by a set of simultaneous equations derived from boundary conditions and the finiteness requirement imposed at the joint. It is shown that the set of equations reduces to a 2×2 matrix for a welded joint, a 3×3 matrix for a hinged joint, and a 4×4 matrix for a free–free joint, i.e., two plates being mechanically unconnected. The frequency-domain acoustic pressure is subsequently obtained by taking an inverse Fourier transformation and evaluated by using the residue theory and contour integrals along the branch cut. Asymptotic behaviors of the plate flexural displacement and radiated acoustic pressure in the frequency-wave-number domain are obtained. Effects of mean flow on resulting sound radiation are examined.
Calculation of acoustic radiation force generated by focused beams using the ray acoustics approach
Authors: Wu Junru
Published: October 2005

Radiation force applied on an absorbing disk due to a focused circular beam generated by a focusing transducer is calculated using the ray acoustics approach. It is found that the radiation force is a function of the acoustic power of the beam, the f number of the source transducer, the normalized radius of the absorbing disk relative to the radius of aperture of the source transducer, the separation between the disk and the source transducer, the ratio between the speed of sound in the medium and that in the disk material, and the ratio between the characteristic acoustic impedance of the disk material and that of the medium.
Influence of geoacoustic modeling on predictability of low-frequency propagation in range-dependent, shallow-water environments
Authors: Cederberg R. J. , Siegmann W. L. , Carey W. M.
Published: October 2005

In a previous study of predictability of relative intensity and horizontal wave numbers by the authors, parabolic approximations were used in range-independent shallow-water waveguides. Uncertainties in sediment properties were found to be the most significant factor limiting prediction accuracy. In this paper, models of bottom sound-speed profiles that take into account sediment consolidation are developed, and their effects on propagation model predictions in range-dependent environments are examined. Modeling of low-frequency results from a New Jersey shelf experiment is the focus of our efforts. Using borehole data and Biot–Stoll theory, the porosity profiles for homogeneous consolidated sediments are derived, and corresponding sound-speed profiles for different sediment types are then constructed. Predictions from models with consolidated sediment layers throughout the bottom are compared with results from cases where bottom sound speed is comprised of piecewise linear segments. In addition, bottom sound-speed range dependence is shown to be significant in the area of the experiment, and different geoacoustic models for it are examined. Comparisons of experimental data with model predictions incorporating range dependence are illustrated and show the influence of the bottom model.
Spatial correlation of acoustic waves scattered from a random ocean bottom
Authors: Tang Dajun , Frisk George V.
Published: October 2005

Acoustic wave scattering from a random bottom is studied. The bottom is modeled as a fluid medium with a layer where the sound speed is composed of a small random component superimposed upon a constant background sound speed. Emphasis is placed on the spatial correlation of the scattered field. It is found that the spatial correlation length of the scattered acoustic field is related to the correlation length of the random sound speed in the bottom, and by sweeping acoustic frequencies, it is possible to invert for the bottom correlation length through measuring the spatial correlation of the scattered field by using a receiving array. Also studied is the influence of anisotropy of the bottom scatterer. A comparison is made to the Born approximation.
A shallow-water normal-mode reverberation model
Authors: Ellis Dale D.
Published: October 2005

A practical model to compute shallow-water boundary reverberation is described. Normal modes are used to calculate the acoustic energy propagating from the source to the scattering area, and from the scattering area to the receiver. At the scattering patch each mode is decomposed into up- and down-going waves, then ray-mode analogies and empirical scattering functions can be used to compute the scattered energy. The method was first described by Bucker and Morris [J. Acoust. Soc. Am. 44, 827–828 (1968)], and papers which first appeared in the Chinese literature. Their work is extended here by using group velocities to obtain the travel times for each mode pair, and by further developing the ray-mode analogy. The effects of summing the modes coherently or incoherently and of including the time spreading due to the modal group velocities are examined. This paper deals with the range-independent monostatic case, although the technique is extendible to bistatic geometries and range-dependent environments. Calculations show excellent agreement with some ray-based models, and, using the Lambert bottom-scattering coefficient as the only adjustable parameter, good agreement is obtained with some measured shallow-water reverberation.
Hysteretic model of the grand piano hammer felt
Authors: Stulov Anatoli
Published: October 2005

The experimental relationships of dynamic force versus grand piano hammer felt deformation show the significant influence of hysteresis characteristics. To explain this phenomenon, a new mathematical model of the hammer felt is proposed. In this model the hammer felt is considered as a nonlinear history-dependent (hysteretic) material with an exponential kernel function. The numerical simulation of interaction of the hammer with a fixed target was used to identify the nonlinear and hysteresis parameters of the felt, and good agreement with experiments was achieved. Also, this model is used here for the analysis of interaction of the hammer with a real grand piano string.
Algorithm for computing the physical descriptor of environmental impulsive sounds
Authors: Cannelli Giovanni B. , Santoboni Silvio
Published: October 2005

Some considerations and information are provided on the previously proposed algorithm for computing the physical descriptor (Lφ) of environmental impulsive sounds. This parameter can be directly measured by a microprocessor-based apparatus recently presented in this Journal [G. B. Cannelli and S. Santoboni, J. Acoust. Soc. Am. 90, 1464–1468 (1991)], but its analytical formulation, as it is given in the above-mentioned paper, needs further improvements in order to fit in perfectly with the working of the instrument. The definitive formulation of Lφ is given here together with an example which clarifies the concept of ‘‘noise fluctuation level’’ and illustrates the way of computing this physical descriptor. Some preliminary laboratory tests are also reported.
Spectral representations of rough interface reverberation in stratified ocean waveguides
Authors: Schmidt Henrik , Kuperman W. A.
Published: October 2005

An earlier developed perturbation approach to scattering from rough interfaces in stratified fluid–elastic media has been extended to provide a spectral representation of the higher-order statistics of waveguide reverberation, incorporating the combined physics of scattering and waveguide propagation. The formulation is compatible with existing propagation and ambient noise models based on wave number integration and therefore provides a more complete model with consistent treatment of all components of the acoustic environment. The model is used to demonstrate how reverberation affects the spatial correlation of the acoustic field, and the associated degradation in performance of high-resolution matched-field processing approaches is discussed. In addition to the higher-order statistics the formulation also provides a model for the reverberant field for specific roughness realizations, allowing for direct modeling of time-domain solutions, both in the spatial and the spectral domains, as illustrated by examples relevant to both deep- and shallow-water sonar scenarios.
Investigation of ultrasonic pulses with an optical probe
Authors: Hays-Stang Kathy J. , Cook Bill D.
Published: October 2005

This paper presents the theory and experimental results for an optical ‘‘near-field’’ technique applied to pulsed ultrasound. This technique was originally developed for continuous-wave ultrasound [B. Cook, J. Acoust. Soc. Am. 60, 95–99 (1976)]. The distinguishing feature of the optical near-field technique is the placement of the photodetector in the optical near field of the optical grating induced by the sound. A photodetector, with a photodiode small compared to the ultrasonic wavelengths and a frequency bandwidth sufficient to detect the ultrasonically induced irradiance variations, combined with a low power laser comprise the optical probe. In this study, the optical probe behaved as a line receiver of ultrasonic pulses propagating in water and as a linear device for the limited range of sound frequencies and amplitudes studied. Investigation of selected portions of the acoustic field confirm previous models of ultrasonic pulses.
Acoustic interaction forces between two fluid spheres in an acoustic field
Authors: Zheng Xiaoyu , Apfel Robert E.
Published: October 2005

The acoustic interaction force between two fluid spheres in a plane acoustic wave field is investigated by calculating the radiation force due to the total acoustic field that includes the incident plane wave and the first- and second-order scattered fields of the objects. A general formula for the radiation force on one sphere is derived which shows the dependence on the resonant modes of the other. In the expression for the radiation force, there are cross terms that involve the primary plane wave and the scattered wave field. For two small bubbles, the result is reduced to the same as the Bjerknes force expression obtained by others under the approximation of long wavelength. Calculations are also done for the case when the primary wave is a standing-wave field.
Free vibration of a clamped-free circular cylindrical shell partially submerged in a liquid
Authors: Chiba M.
Published: October 2005

Theoretical analysis and experimental study have been carried out on the free vibration of a thin cantilever cylindrical shell partially submerged in a liquid. In the analysis, the shell is assumed to be submerged in a rigid cylindrical container with finite diameter. Considering the effect of static liquid pressure, coupled bulging-type natural frequencies were calculated for various system parameters, i.e., thickness ratio, aspect ratio, density ratio, radius ratio, material parameter, and liquid height. The effect of liquid height outside the shell on the bulging-type natural frequency and on the mode shape of vibration was found to be remarkable for a thinner and longer shell. The results are summarized in the form of engineering design data from which one can easily presume the natural frequency of a given shell partially submerged in a liquid. To confirm the accuracy of the theoretical analysis, experimental study was conducted by using two test cylinders made of polyester film. Excellent agreement between theoretical results and experimental ones was demonstrated.
Active control of the sound radiated by a vibrating body using only a layer of simple sources
Authors: Fahnline John B.
Published: October 2005

Previous research in the area of active noise control has shown that the sound radiation from a vibrating body can be completely controlled using layers of simple and dipole sources located on a surface which completely surrounds the vibrating body. In this paper, the source layer is assumed to consist of simple sources only. If complete control of the sound radiation can be achieved with simple sources only, the implementation of the control strategy will be considerably simplified because simple sources can be approximated with conventional loudspeakers. It is shown that complete control can be achieved when the simple source layer is just outside the boundary surface of the vibrating body (assuming that the fluid coupling between the vibrating body and the surrounding fluid is negligible). When the simple source layer is not near the surface of the vibrating body, the control strategy fails at the resonance frequencies of the volume of fluid between the surface of the vibrating body and the layer of simple sources. It is also shown that in the limit as the source surface approaches the surface of the vibrating body, the control source amplitudes can be written directly in terms of the normal surface velocity of the vibrating body. An example is given to demonstrate the accuracy of the analytical development.