bluuebunny/crossref_metadata_2025 huggingface dataset:
Monthly monitoring program on DryView™ laser imager: One year experience on five Imation units
Authors: Lu Z. F. , Nickoloff E. L. , Terilli T.
Published: July 2002

Dry‐processing film systems have become popular particularly in a network environment. This is mainly due to its ability to produce high quality images without wet chemistry processing. In this paper we describe a monthly monitoring program on five Model 8700 DryView™ Laser Imagers in our institution. A SMPTE pattern is generated via DryView™ Laser Imager software. The 100% patch is used for checking the base‐plus‐fog of the Imager. The 40% patch is used as the speed index. The optical density difference between patches 10% and 70% is used as the contrast index. These numbers are plotted for testing system consistency. In addition, the SMPTE pattern is examined to verify the sharpness of the bar patterns and the visibility of subtle contrasts—95% inset in the 100% patch and a 5% inset in the 0% patch. The clinical films are checked for processor artifacts, such as residuals from the drum. Stability of the dry processors has also been studied using three strips per day obtained at three different times of the day over a period of ten consecutive working days. The coefficient of variation is 0.05 for the speed index and 0.04 for the contrast index. The monthly monitoring program has been carried out in our institution since January 1997. The problems found by this monthly monitoring program assess the necessity of routine QC for DryView™ Laser Imagers. The instability of the post‐processing dry silver films, and, consequently, the film handling requirements, are also discussed.
Effect of lateral boundaries on contrast functions in time‐resolved transillumination measurements
Authors: Chernomordik Victor , Gandjbakhche Amir H. , Hebden Jeremy C. , Zaccanti Giovanni
Published: July 2002

The method of images is employed to insert the effects of the presence of a single lateral boundary on contrast functions previously derived for an infinite slab using a random walk model of photon transport. The predictions of the model for zero and extrapolated boundary conditions are compared with Monte Carlo (MC) simulations and with experimental results obtained using a homogenous phantom with tissue‐like optical properties. As expected, the extrapolated boundary condition yields better agreement between the theoretical predictions and results obtained from MC and experiments. This indicates that the random walk model has potential as a forward model in iterative imaging schemes developed for optical tomography.
Computer‐aided diagnosis: Automatic detection of microcalcifications on digital mammograms (in Spanish)
Authors: Lado Marı́a J.
Published: July 2002

A computerized scheme to detect clustered microcalcifications in digital mammograms was developed. Detection of individual microcalcifications in regions of interest was also performed. Mammograms were previously classified into fatty or dense. The wavelet basis and reconstruction levels were selected. The symlets 8 were chosen for fatty tissue, and the Daubechies 4 for dense tissue. Two methods to detect individual microcalcifications were evaluated: two‐dimensional and one‐dimensional wavelet transform. The second technique yielded the best results, and was used to detect clustered microcalcifications in the complete mammogram, employing a scheme involving: (1) detection of the breast border, (2) application of one‐dimensional wavelet transform, (3) application of gray level threshold, (4) clustering procedure, (5) reduction of false positives with discriminant analysis. When detecting individual microcalcifications, we have obtained a sensitivity of 66% and an average of 7.23 false positives per image with the two‐dimensional method, and 71% of sensitivity at an average false positive rate of 6.12 with the one‐dimensional technique. For the detection of clustered microcalcifications, the sensitivity was 80% with an average of 0.94 false positives per image for fatty mammograms. The area under the AFROC curve was For dense mammograms, 73% of sensitivity at a false positive detection rate of 2.21 per image was achieved Globally, a sensitivity of 76% and an average of 1.57 false detections per image were obtained. We conclude that a wavelet‐based method to detect clustered microcalcifications would help radiologists as a “second opinion” in mammographic screening. The low false positive rate indicates that our technique would not confuse the radiologist by suggesting normal regions as suspicious.
Reliability of water proton chemical shift temperature calibration for focused ultrasound ablation therapy
Authors: Wu Tao , Kendell Kurtis R. , Felmlee Joel P. , Lewis Bradley D. , Ehman Richard L.
Published: July 2002

Our purpose in this work was to assess the reliability of the calibration coefficient for magnetic resonance water proton chemical shift temperature mapping. Over a six month period, the calibration coefficient was measured 15 times in several different phantoms. A highly linear relationship between water proton chemical shift and temperature change was found. The average temperature calibration coefficient determined from all studies was Four of the 15 studies were conducted on the same day using the same phantom. The average temperature calibration coefficient of these four studies was
A new approach to bound states in potential wells
Authors: Bloch J.-F. , Ignatovich V.
Published: July 2002

A method for calculating the energies of the bound states of a particle in a potential well is presented. A generalization of the Bohr–Sommerfeld quantization rule is obtained.
Impact of a ball with a bat or racket
Authors: Cross Rod
Published: July 2002

The collision of a ball with a baseball bat or a tennis racket is usually modeled in terms of rigid body dynamics, assuming that the hand exerts no impulsive reaction force on the handle during the collision. In this paper, a uniform aluminum beam was used as an idealized bat or racket, in order to examine both the rigid body approximation and the assumption that the hand force can be neglected. An aluminum beam was chosen so that its length and stiffness could easily be varied and so that the results could be compared with solutions for a flexible beam. It was found that rigid body models of beams, bats, or rackets are of limited use but the hand force can usually be neglected. The flexible beam model provides remarkably good agreement with experimental results and provides new insights into the dynamics of this type of collision, including the nature of the sweet spot.
An efficient model of an equipment loaded panel for active control design studies
Authors: Aglietti G. S. , Langley R. S. , Rogers E. , Gabriel S. B.
Published: July 2002

An effective investigation of alternative control strategies for the reduction of vibration levels in satellite structures requires realistic, yet efficient, structural models to simulate the dynamics of the system. These models should include the effects of the sources, receivers, supporting structure, sensors, and actuators. In this paper, a modeling technique which meets these requirements is developed and some active control strategies are briefly investigated. The particular subject of investigation is an equipment-loaded panel and the equations of motion are derived using the Lagrange–Rayleigh–Ritz (LRR) approach. The various pieces of equipment on the panel are mounted on active or passive suspensions, and resonators are used to represent the internal dynamics of the mounted equipment. Control of the panel, which transmits vibrations from sources to receivers, is by means of piezoelectric patches and the excitation consists of dynamic loads acting on the equipment enclosures and/or directly on the panel. The control objective is to minimize the displacement at an arbitrary output location. The LRR model developed is verified against one produced by using the finite-element method. Finally, some initial controller design studies are undertaken to investigate and compare the effectiveness of different control strategies (e.g., minimization at the source, along the vibration path, or at the receiver).
Two- and three-dimensional complex-transducer-point analysis of beam reflection from anisotropic plates
Authors: Zhang Han , Chimenti D. E.
Published: July 2002

In this paper a frequency-domain analysis of the fluid-immersed plate reflection spectrum in which the transmitter and receiver acoustic beams are modeled with complex transducer points is presented. Lamb wave dispersion in the plate forms the major structural features of the reflection spectra. By assuming a linear dependence of the Fresnel length on the frequency for a flat piston transducer, the complex transducer point technique can be employed over a wide frequency range. With the aid of the reciprocity theorem for electroacoustic transducers, a rigorous three-dimensional (3D) expression for the receiver voltage in a pitch–catch transducer arrangement has been derived by using a pair of transmitting and receiving complex transducer points. The calculations are supported by the results of numerous experiments on both isotropic and anisotropic materials in various measurement geometries. The conditions under which a 3D calculation is important are demonstrated, and comparison with a simpler 2D calculation is made. The model calculation is also applied to illuminate several issues related to materials characterization.
Spatial analysis of torsional wave propagation in a cylindrical waveguide. Application to magnetostrictive generation
Authors: Aime Jean-Christian , Brissaud Michel , Laguerre Laurent
Published: July 2002

A spatial analysis of the generation and propagation of torsional waves in a cylindrical rod is presented. Starting from the classical linear equation of propagation and assuming a linear medium of propagation, the eigenfunctions of the propagation operator are calculated. Under the hypothesis of separation-of-variables type of solution, two ways of deriving the associated modes are performed. Given the normal mode basis, the behavior of a wavefront generated into the rod is examined. The application to the magnetostrictive generation of torsional waves is studied. Including the influence of eddy currents on the excitation and the geometry waveguide effects on the wave propagation, an analytical expression of mechanical losses during the first steps of propagation is given. A basic model of the interaction between a defect and the torsional guided waves is also proposed.
A model for sound lateralization
Authors: Aharonson Vered , Furst Miriam
Published: July 2002

Recent studies of multiple sclerosis (MS) and stroke patients suggested a correlation between two patterns of abnormal performance in lateralization tasks and two sites of pontine lesions. Most patients who had lesions below or at the superior olivary complex (SOC) perceived all interaural differences in binaural stimuli as small, while most patients who had lesions above the SOC perceived all interaural differences as large. The two abnormal performance patterns occurred for interaural time differences (ITD) and/or for interaural level differences (ILD). The present model proposes a multi-level hierarchical brainstem structure that estimates ITD and ILD. The first level seeks dissimilarity between the left and right inputs and a second level looks for similarity between the two sides’ inputs. Each level is modeled as an ensemble of neural arrays in which each unit performs a logic or arithmetic function. The inputs are simulations of auditory nerve responses to broadband stimuli. Simulations yield good correspondence to the effect of both locations of pontine lesions on binaural performance.
An analysis of the response of Sooty Tern eggs to sonic boom overpressures
Authors: Ting Carina , Garrelick Joel , Bowles Ann
Published: July 2002

It has been proposed that sonic booms caused a mass hatching failure of Sooty Terns in the Dry Tortugas in Florida by cracking the eggshells. This paper investigates this possibility analytically, complementing previous empirical studies. The sonic boom is represented as a plane-wave excitation with an N-wave time signature. Two models for the egg are employed. The first model, intended to provide insight, consists of a spherical shell, with the embryo represented as a rigid, concentric sphere and the albumen as an acoustic fluid filling the intervening volume. The substrate is modeled as a doubling of the incident pressure. The second, numerical model includes the egg-shape geometry and air sac. More importantly, the substrate is modeled as a rigid boundary of infinite extent with acoustic diffraction included. The peak shell stress, embryo acceleration, and reactive force are predicted as a function of the peak sonic boom overpressure and compared with damage criteria from the literature. The predicted peak sonic boom overpressure necessary for egg damage is much higher than documented sonic boom overpressures, even for extraordinary operational conditions. Therefore, as with previous empirical studies, it is concluded that it is unlikely that sonic boom overpressures damage avian eggs.
Acoustic sounding of wind velocity profiles in a stratified moving atmosphere
Authors: Ostashev Vladimir E. , Georges Thomas M. , Clifford Steven F. , Goedecke George H.
Published: July 2002

The paper deals with analytical and numerical studies of the effects of atmospheric stratification on acoustic remote sensing of wind velocity profiles by sodars. Both bistatic and monostatic schemes are considered. Formulas for the Doppler shift of an acoustic echo signal scattered by atmospheric turbulence advected with the mean wind in a stratified moving atmosphere are derived. Numerical studies of these formulas show that errors in retrieving wind velocity can be of the order of 1 m/s if atmospheric stratification is ignored. Formulas for the height at which wind velocity is retrieved are also derived. Approaches are proposed which allow one to take into account the effects of atmospheric stratification when restoring the wind velocity profile from measured values of the Doppler shift and the time interval of acoustic impulse propagation from a sodar to the scattering volume and back to the ground.
Comment on “Free vibration analysis of laminated piezoceramic hollow spheres” [J. Acoust. Soc. Am. 109, 41 (2001)]
Authors: Buchanan George R. , Ramirez Guillermo R.
Published: July 2002

In a recent article, Chen [J. Acoust. Soc. Am. 109, 41–50 (2001)] presented a three-dimensional analysis for piezoelectric hollow thick spheres. Results were presented for several configurations for shells of layered piezoelectric materials. The elastic material constants for PZT-4 that were used in the paper were in error and this letter is an attempt to justify and offer suggestions that can preserve the value of the analysis.
On the effect of boundaries on radiation resistance of plates
Authors: Renji K.
Published: July 2002

At high frequencies, radiation resistance of a plate converges to the radiation resistance of the simply supported plate and is not influenced by its boundary conditions. But, at low frequencies the radiation resistance is significantly influenced by the boundary conditions. Up to what frequency the boundaries affect the radiation resistance is experimentally investigated in this study. It is found that this depends on the number of bending waves present in the structure and not merely on the critical frequency. If the plate contains more than two bending waves, the radiation resistance is approximately equal to the radiation resistance of the plate with simply supported boundaries. Also, a plate behaves like an infinite plate at frequencies above the critical frequency only if it contains a few bending waves.
Lagrangian effective material constants for the modeling of thermal behavior of acoustic waves in piezoelectric crystals. I. Theory
Authors: Dulmet Bernard , Bourquin Roger
Published: July 2002

After some necessary recalls on the nonlinear theory of thermoelectroelasticity in piezoelectric crystals, asserting the need of constitutive equations which derive from a rotationally invariant energy function, this paper presents the governing equations for a small vibration superimposed on a bias originated by a slow and homogeneous temperature variation from a well-defined reference state. Thereafter, the authors define the effective coefficients appearing in the linearized incremental dynamic balance equations for linear momentum and electrical charge in Lagrange configuration, not omitting associated boundary conditions. The main features of these coefficients are discussed and explicit relations with more conventionally defined coefficients are given. Determination of numerical values of the proposed effective coefficients and examples of their use in the higher order modeling of static frequency–temperature characteristics of either bulk acoustic wave or surface acoustic wave devices are given in a companion paper.
Oscillation modes of supersonic multijets exhausting from very adjacent multiple nozzles
Authors: Umeda Yoshikuni , Ishii Ryuji
Published: July 2002

The oscillation modes of a supersonic circular twin jet and multijet with square configuration where the center-to-center spacing of nozzles was fixed to 1.4 times the nozzle diameter were investigated experimentally. It is found that the twin jet oscillates simultaneously in three different oscillation modes for the pressure ratios of about 4.1. From the acoustical observation, these oscillation modes are identified as one lateral oscillation mode perpendicular to a plane composed of the twin jet axes and two lateral oscillation modes parallel to this plane. For a multijet with a square configuration, only one lateral oscillation mode was observed. In this case, it is observed that when the spacing between two facing sides of the square formed by four jets is stretched, the spacing between the other two sides shrinks and vice versa.
Modeling of high-frequency propagation in inhomogeneous background random media
Authors: Mazar Reuven
Published: July 2002

When a high-frequency electromagnetic wave propagates in a complicated scattering environment, the contribution at the observer is usually composed of a number of field species arriving along different ray trajectories. In order to describe each contribution separately the parabolic extension along an isolated ray trajectory in an inhomogeneous background medium was performed. This leads to the parabolic wave equation along a deterministic ray trajectory in a randomly perturbed medium with the possibility of presenting the solution of the high-frequency field and the higher-order coherence functions in the functional path-integral form. It is shown that uncertainty considerations play an important role in relating the path-integral solutions to the approximate asymptotic solutions. The solutions for the high-frequency propagators derived in this work preserve the random information accumulated along the propagation path and therefore can be applied to the analysis of double-passage effects where the correlation between the forward–backward propagating fields has to be accounted for. This results in double-passage algorithms, which have been applied to analyze the resolution of two point scatterers. Under strong scattering conditions, the backscattering effects cannot be neglected and the ray trajectories cannot be treated separately. The final part is devoted to the generalized parabolic extension method applied to the scalar Helmholtz’s equation, and possible approximations for obtaining numerically manageable solutions in the presence of random media.
A blood vessel exposed to ultrasound: A mathematical simulation of the temperature field
Authors: Krasovitski Boris , Kimmel Eitan
Published: July 2002

In this article we present a mathematical simulation of the temperature field in and around a blood vessel when it is sonicated by a focused ultrasound beam. A simplified geometry is considered: a cylindrical blood vessel is embedded in tissue parallel to a flat skin surface. The ultrasound transducer is placed on the skin above the blood vessel, perpendicular to the skin surface. The 3D geometry of the problem is simplified by transformation, which maps the domain into a parallelepiped. A computational algorithm and computer program were developed. The simulation provides the conditions for successful occlusion of a blood vessel and demonstrates the significant role of the blood flow rate on the temperature difference between the vessel wall and the surrounding tissue. Comparing the predictions with published experimental data tested the validity of the method.
Experimental validation of RESOUND mid-frequency acoustic radiation models
Authors: Gardner Bryce K. , Shorter Philip J.
Published: July 2002

RESOUND is a full-spectrum structural acoustic analysis method that uses finite element analysis in the low frequency region, statistical energy analysis in the high frequency region and a hybrid approach in the mid frequency region. In this paper, acoustic radiation from a frame-stiffened panel into a large acoustic space will be investigated. Over the frequency range of interest, the frame has relatively few modes and exhibits long wavelength global behavior, while the panel has a large number of modes and exhibits short wavelength local behavior. Numerical and experimental results will be presented which illustrate how the frame and panel interact to give rise to the radiated sound field.
Effect of hydrochloric acid on sound absorption and relaxation frequency in magnesium sulfate solutions
Authors: Fisher F. H.
Published: July 2002

The epic work of Kurtze and Tamm on sound absorption spectroscopy in divalent sulfate electrolyte solutions (1953) from the low-kHz region up to over 200 MHz revealed astonishing variability at frequencies below 10 MHz and a common relaxation frequency at about 200 MHz. For magnesium sulfate [Epsom salts] solutions, the salt producing 30× the absorption of fresh water below the 100-kHz region in the oceans at low concentrations [∼0.02 moles/liter], Kurtze and Tamm investigated the effects of adding HC1 or H2SO4. They found that as formal pH increased, the results were different for these acids in reducing the sound absorption. Fisher (1983) found that if the absorption was plotted against free hydrogen, ion concentration was the same. We used the 100-liter titanium sphere, a spare ballast tank from the WHOI submarine alvin. With precise temperature control, we found an increase in the relaxation frequency as HC1 was added in conjunction with the reduction in sound absorption. The results will be presented and an explanation will be proposed in the context of the Eigen and Tamm multistate dissociation model for MgSO4 (1962) which explains the effects of pressure on both absorption and conductance. [Work supported by ONR.] The author acknowledges C. C. Hsu for his work on this project.
Chaotic behavior of piezoelectric plate vibration
Authors: Zhang Yu , Jiang Wen-hua , Du Gong-huan
Published: July 2002

A dynamical model for the piezoelectric plate vibrations is presented in this letter. The calculations of phase portrait and Lyapunov exponents based on the coupled-mode equations given by the theoretical model show that the vibrations of a piezoelectric plate resonator under the resonance may exhibit the chaotic behavior. The experiment is carried out for a LiNbO3 thickness-longitudinal vibration plate resonator by using a setup based on heterodyne laser probe. The fractional harmonic vibration as well as chaotic behaviors are observed.
Attenuation and permeability: high frequency crosswell tomography for imaging permeability structure of sediments
Authors: Yamamoto Tokuo , Sakakibara Junich , Mohri Yoshiyuki
Published: July 2002

Imaging the permeability within sediments and rocks is one of the important problems left to advance in geoacoustics and geophysics. The Hamilton attenuation data suggests it is possible. As a U.S.–Japan joint research project we have selected this important problem. Desired permeability and porosity of test sediments are achieved with a sophisticated technique of sediment deposition called laminar sedimentation. To minimize reflections from the tank walls a wave absorber was placed between the tank wall and sediments. Placing a second hydrophone well between the source well and the receiver well, bore hole losses were physically minimized so as to assure accurate measurements of attenuation. A broadband piezoelectric source and hydrophone arrays were used to propagate and receive high frequency M-sequence acoustic waves. High resolution permeability images within various sediments are extracted from attenuation and velocity measured by high frequency (10 kHz to 80 kHz) acoustic cross-well tomography experiments and a Biot inversion. [Work supported by ONR, NIRE, and KSEC.]
Thermoacoustics with idealized heat exchangers and no stack
Authors: Wakeland Ray Scott , Keolian Robert M.
Published: July 2002

A model is developed for thermoacoustic devices that have neither stack nor regenerator. These “no-stack” devices have heat exchangers placed close together in an acoustic standing wave of sufficient amplitude to allow individual parcels of gas to enter both exchangers. The assumption of perfect heat transfer in the exchangers facilitates the construction of a simple model similar to the “moving parcel picture” that is used as a first approach to stack-based engines and refrigerators. The model no-stack cycle is shown to have potentially greater inviscid efficiency than a comparable stack model. However, losses from flow through the heat exchangers and on the walls of the enclosure are greater than those in a stack-based device due to the increased acoustic pressure amplitude. Estimates of these losses in refrigerators are used to compare the possible efficiencies of real refrigerators made with or without a stack. The model predicts that no-stack refrigerators can exceed stack-based refrigerators in efficiency, but only for particular enclosure geometries.
Duration sensation in relation to the autocorrelation function of sound stimuli
Authors: Saifuddin Kazi
Published: July 2002

Relationships were investigated between subjective judgment of physical duration and the factors extracted from the autocorrelation function (ACF) of sound stimuli. Factors of ACF were changed by using different properties of pure-tone, complex-tone, white noise and bandpass-noise stimuli. Experiments by paired-comparison method were conducted in the sound proof chamber except for one in a concert hall. Sound stimuli were selected on the basis of the measured factors of ACF as parameters. Subjects were asked to compare the durations of two stimuli in the pair. Subjective durations were obtained in the psychometric function and were interpreted as duration sensation (DS) on the basis of the auditory-brain model and the theory of primary sensation. Results (p<0.05) are shown as below. (1) DSs are longer with larger τ1 (being time delay of first peak of ACF corresponding to pitch. (2) DSs are longer with higher Φ(0) (being energy at the beginning of ACF). (3) DSs are longer with smaller φm (being constant amplitude of all peaks of ACF). (4) DSs are similar for pure-tone and complex-tone stimuli with same pitch.

Thesis advisor: Yoichi Ando

Copies of this thesis written in English can be obtained from Junko Atagi, 6813 Mosonou, Saijo-cho, Higashi-Hiroshima 739-0024, Japan. E-mail address: atagi\@urban.ne.jp.
Personal glimpses of Ira Hirsh: Covariance of perception and reality
Authors: Clark William
Published: July 2002

No session honoring Ira Hirsh would be complete without a personal reflection of his enormous influence on his colleagues, students, and friends. During his career in St. Louis that covered the entire second half of the 20th Century (and still continues), Ira interacted with numerous colleagues at Central Institute for the Deaf, where he served as a senior scientist, Director of Research, and Institute Director. His second parallel career was at Washington University, where he was Professor of Psychology, and included a term as Dean of the Faculty of Arts and Sciences. This tribute will provide reflections and reminiscences of what it was like to work with, and learn from, Ira Hirsh.
Acoustic backscatter from materials with rough surfaces and finite size microstructure: Theory
Authors: Bilgen Mehmet , Rose James H.
Published: July 2002

Surface roughness changes the acoustic backscatter signal due to the microstructure of a sample. These changes have been previously reported for the backscatter power under the restrictive assumption that the microstructural length scales are much smaller than any other length scale in the problem. In this study this restriction is removed and an approximate analytic series solution is presented that describes the effects of surface roughness on the power and mean square of the acoustic backscatter from samples whose microstructure is characterized by an autocorrelation length Lm, which may be smaller than, comparable to, or larger than either the wavelength or the autocorrelation length Ls that describes the surface roughness. Both focused and unfocused phase-sensitive transducers are considered. A surprising result emerged. For focused probes at normal incidence and for moderate roughness, the backscattered power at the focal depth is almost entirely determined by the frequency and the rms surface height; it is independent of Lm, Ls, and the radius of the transducer.
Time-domain simulation of the influence of close barriers on sound propagation to the environment
Authors: Botteldooren D.
Published: July 2002

A time-domain numerical model for studying the influence of close barriers on sound levels at a large distance from a source is proposed. It is a combination of a near-field simulation with a near-field to far-field transform based on the Helmholtz–Kirchhoff integral. The near-field simulation is based on a finite-difference time-domain type discretization of a well chosen volume around sources and near objects. The numerical accuracy of the model is studied theoretically and experimentally for a particular sound field. The simulation example is a large power station transformer surrounded by barriers. The evaluation of sound levels in the highly multimodal environment is not trivial. It is performed in small frequency bands around the frequency of the typical pure tones emitted by the source.
The modeling of a continuous structure as a fuzzy
Authors: Garrelick Joel
Published: July 2002

For a continuous structure with a deterministic drive, it is suggested by example that (1) the loss factor invariance of its fuzzy limit is realized only when boundaries/discontinuities away from the master structure measure many characteristic wavelengths so that the influence of their reflecting waves is negligible at the interface, and (2) the value of the fuzzy limit depends on structural details as well as averaged or “smoothed” characteristics.
The simulation of structural response to sonic booms using structural acoustic techniques
Authors: Garrelick Joel , Martini Kyle , Downing Micah , Brown Ron
Published: July 2002

Structural damage from sonic booms is one of the potential environmental impacts of supersonic flight. This paper illustrates how structural acoustic techniques may be used to assess the potential for such damage in the absence of actual flyovers. Procedures are described whereby transfer functions relating structural response to sonic boom signature may be obtained with a stationary acoustic source and appropriate data processing. Further, by invoking structural acoustic reciprocity, these transfer functions may also be acquired by measuring the radiated sound from a structure that is mechanically driven. The approach is based on the fundamental assumption of linearity, both with regard to the (acoustic) propagation of the boom in the vicinity of the structure and to the structure’s response. Practical issues revolve around acoustic far field, source strength, and directivity requirements. The technique was evaluated on a specially fabricated test structure at Edwards AFB, CA. Blank shots from a cannon served as the acoustic source and taps from an instrumented hammer generated the mechanical drive. Simulated response functions were constructed. Results of comparisons with corresponding measurements recorded during dedicated supersonic flyovers with F-15 aircraft are presented for a number of sensor placements. Using the prediction of peak structural response as a metric, it was found that the direct and reciprocal simulation techniques produced ensemble-averaged mean percent errors of −4% and −26%, respectively. The corresponding standard deviations of these errors were 18% and 16%. Also, it was concluded that these uncertainties are consistent with that connected to the representation of the sonic boom itself.
A theoretical basis for the high-frequency performance of the outer hair cell’s receptor potential
Authors: Hassan El-S.
Published: July 2002

The frequency response of the outer hair cell (OHC) was studied theoretically. An electrical model of the OHC was analyzed mathematically, taking into account the effect of its inherent voltage-dependent capacitance. It was found that the variations of the capacitance dependent on the membrane potential could enhance the high-frequency response of the OHC, so that its cutoff frequency could be extended into the audio range. It was found further that the enhancement of the frequency response of the OHC was strongly dependent on its resting potential and on the ratio of the maximum voltage-dependent capacitance to the membrane linear capacitance.
Acceptability for temporal modification of consecutive segments in isolated words
Authors: Kato Hiroaki , Tsuzaki Minoru , Sagisaka Yoshinori
Published: July 2002

Perceptual sensitivity to temporal modification in two consecutive speech segments was measured in word contexts to explore the following two questions: (1) whether there is an interaction between multiple segmental durations, and (2) what aspect of the stimulus context determines the perceptually salient temporal markers? Experiment 1 obtained acceptability ratings for words with temporal modifications. The results showed that the compensatory change in duration of a vowel (V) and its adjacent consonant (C) is not perceptually so salient as expected for the simultaneous modifications in the two segments. This finding suggests the presence of a time perception range wider than a single segment (V or C). The results of experiment 1 also showed that rating scores for compensatory modification between V and C do not depend on the temporal order of modified pairs (VC or CV), but rather on the loudness difference between V and C; the acceptability decreased when the loudness difference between V and C became high. This suggests that perceptually salient markers locate around major jumps in loudness. The second finding, the dependence on the loudness jump, was replicated in experiment 2, which utilized a detection task for temporal modifications on nonspeech stimuli modeling the time-loudness features of the speech stimuli. Experiment 3 further investigated the influence of the temporal order of V and C by utilizing the detection task for the speech stimuli instead of the acceptability ratings.
A consonance-based approach to the harpsichord tuning of Domenico Scarlatti
Authors: Sankey John , Sethares William A.
Published: July 2002

This paper discusses a quantitative method for the study of historical keyboard instrument tunings that is based on a measure of the perceived dissonance of the intervals in a tuning and their frequency of occurrence in the compositions of Domenico Scarlatti (1685–1757). We conclude that the total dissonance of a large volume of music is a useful tool for studies of keyboard instrument tuning in a historical musical context, although it is insufficient by itself. Its use provides significant evidence that Scarlatti used French tunings of his period during the composition of his sonatas. Use of total dissonance to optimize a 12-tone tuning for a historical body of music can produce musically valuable results, but must at present be tempered with musical judgment, in particular to prevent overspecialization of the intervals.
Use of a power law relation to describe field measurements of compressional and shear velocity in a sediment
Authors: Endo Harumi
Published: July 2002

A sediment is assumed as a percolation network described by a “Swiss cheese” continuum model. A scaling law for a sediment is applicable to describe field measurements of compressional and shear velocity with porosity. The experimental data obtained by Deep Sea Drilling Project of three sites 288, 289, and 316 on the Ontong–Java Plateau in the western Pacific Ocean is available for calculations. The approximate expression of the variation of sound velocity with porosity (p) obtains when satisfied with the conditions of pc>p, where pc is the critical porosity. This expression is analogous to that of the frame bulk modulus obtained by Hamilton.
On the scattering of antisymmetric edge modes
Authors: de Billy M.
Published: July 2002

The scattering of antisymmetric flexural waves is illustrated via three series of experiments conducted on linear elastic solid wedges immersed in air. It is quantitatively demonstrated that scattering into different modes exists when an antisymmetric mode is reflected at the end face of a wedge or when it is submitted to an external pressure applied on the tip of the wedge. The existence of transmission of edge modes is also experimentally confirmed.
Computation of the modal response of regularly ribbed cylinders
Authors: Maidanik G. , Becker K. J.
Published: July 2002

Recently an efficient technique was proposed for performing a Fourier transformation on integrands that are composed of aliased factors. In this paper the proposed technique is utilized to perform Fourier transformations on quantities that pertain to the response of a regularly ribbed cylinder. The computations relate to Fourier transformations from the axial wave-number domain to the axial spatial domain. The phenomena of aliasing and pass bands and stop bands are of particular interest. It is argued that the complementarity of the data, when presented in the two Fourier conjugate domains, may be a useful analytical (and experimental) tool.
New formulation of the resonance scattering theory
Authors: Choi Myoung-Seon
Published: July 2002

According to the resonance scattering theory, a process of background subtraction is always required to obtain the resonance spectrum of a target. A new formulation of the theory is proposed here in which the background subtraction is not necessary and the resonance spectrum can be obtained directly. Contrary to the previous theory, this formulation suggests that, within each partial wave, there are three contributions: the resonance, the background, and their correlation. Also, it is shown that the resonance contribution (at least for empty elastic shells) can be synthesized by considering the resonances of Breit–Wigner form and their pair correlation.
Antisymmetric nature of the earliest arrivals of ultrasound propagating in copy paper
Authors: Johnson Mont A. , Berthelot Yves H.
Published: July 2002

Experiments with laser generation and detection of ultrasound in copy paper indicate that earliest arrivals of ultrasound are antisymmetric. A likely explanation is that the out-of-plane interferometer is relatively insensitive to the symmetric compressional pulse because of the low Poisson ratio of copy paper, but rather sensitive to its antisymmetric flexural wake associated with the random heterogeneities and gradients present in copy paper.
Response to “Comment on ‘Modal analysis of a structure in a compressible fluid using a finite element/boundary element approach’ ” [J. Acoust. Soc. Am. 102, 2445–2447 (1997)]
Authors: McCollum M. D. , Siders Clementina M.
Published: July 2002

The authors thank Professors Pathak and Jalihal for their interest in our paper describing an iterative approach to estimating the in-water modal frequencies of a structure in a compressible fluid. Because of the requirement that the mode of interest remain uncoupled when the structure is submerged, the method is limited to nondimensional wave numbers, ka, of much less than one. In their Letter, Pathak and Jalihal showed that the method does not converge for some configurations of a piston in an infinite baffle, even though the in-water modal frequency is less than one. It is proposed that the lack of convergence is a result of the ideal nature of the piston problem. The particular configurations for which the method does not converge have one common characteristic. This is that the ka value corresponding to the in vacuo modal frequency is large, even though the final in-water ka is less than one. For these configurations, the radiation loading at the in vacuo frequency, which is the starting point for the iterative procedure, is dominated not by the radiation mass, but by the radiation damping. For realistic structures whose low-order modes remain uncoupled after submergence, the radiation mass is dominant at both the in vacuo and in-water modal frequencies. The proposed method is based on the assumption that this is the case, and was shown to be efficient and accurate for several modes of three multi-modal structures. Although it is believed that the piston variations presented by Pathak and Jalihal are outside of the realm of realistic structures, it will be shown that it is possible to achieve convergence to an accurate solution with a simple modification to the iterative procedure.
Acoustic scattering from a three-dimensional protuberance on a thin, infinite, submerged elastic plate
Authors: Kapoor Tarun K. , Schmidt Henrik
Published: July 2002

Scattering of sound from an infinite plate is significantly altered by the presence of an impedance discontinuity. Here, an approximate analytical solution is developed for the scattering of sound from a three-dimensional protuberance on a thin, infinite, submerged elastic plate. The protuberance is modeled as a solid elastic sphere of dimensions comparable to the incident acoustic wave [ka∼O(1)], and is attached to the plate along its equatorial plane. The plate is modeled using thin plate theory and supports the lowest-order flexural, compressional, and horizontally polarized shear (SH) modes, while the solid sphere is modeled with the full three-dimensional elastodynamic equations of motion. This idealized environmental model provides an understanding of the underlying physics of 3-D scattering, which is shown to be strongly frequency dependent. The analysis demonstrates that the attachment of the plate manifests itself in the scattered field in a frequency selective manner, and that the resonances of the elastic modes in the sphere leave their imprint on the elastic waves coupled into the plate. It is also shown that since the attached plate primarily restrains the motions of the sphere in the horizontal plane, the dominant contribution to the scattered field arises from the in-plane coupling forces.
Finite correlation and coherent propagation effects in the normal-mode description of bottom reverberation
Authors: LeMond J. E. , Koch Robert A.
Published: July 2002

A normal-mode scattering formulation that assumes a finite spatial correlation length in the distribution of scattering features is used to compute single-frequency bottom reverberation for bistatic and monostatic scattering geometries in a shallow water and deep water environment. Spatial correlation of the scattering features allows the superposition of modes scattered within each spatially correlated region and produces diffraction in the scattered field that is not predicted in the limit of a zero spatial correlation length (point scattering). For bistatic scattering geometries, the scattered field computed as a function of scattering location in the horizontal plane exhibits a pattern of diffractive maxima and minima for nonzero spatial correlation lengths. The spatial details of the diffraction pattern and its influence on the scattered energy depend on the frequency and spatial correlation length and can result in a significant reduction in the predicted levels of received reverberation. The greatest sensitivity to finite correlation effects occurs for monostatic scattering geometries because the strongest diffractive effects occur in the backscattering direction. The effects of including modal interference in the incident and scattered field propagation are also examined in this paper. The inclusion of modal interference in the propagating fields imposes an interference pattern on the spatial structure of the scattered field in the horizontal plane, and can cause the temporal dependence of the reverberated return to oscillate about the levels of return predicted when modal interference in the propagating fields is neglected. In agreement with previously published results for bottom backscattering, the effects of including modal interference in the propagating fields were found to be significant for deep water environments that exhibit convergent zone propagation and to be of limited importance for shallow water environments in which the energy incident on the bottom is characterized by a large number of multipaths. The present work includes results which show that the effects of including modal interference in the propagating fields can be important for shallow water environments that exhibit significant bottom penetration.
Experimental study of sound scattering by elastic spheroids
Authors: Bao X. L. , Überall Herbert , Niemiec J.
Published: July 2002

Experimental results are presented for sound scattering from elastic prolate and oblate spheroidal scattering objects. The backscattered waveform, the target strength versus incident angle, and the frequency response of the echoes are obtained directly from experimental data or via numerical processing of these data. Analytical models and computer codes are developed for estimating the arrival times of the elastic echoes and the resonance modes.
On the overlapping acoustic resonances of a fluid-filled cavity: Schlieren visualization of an insonified circular-cylindrical shell
Authors: Chinnery Paul A. , Humphrey Victor F.
Published: July 2002

A schlieren technique is used to visualize the fluid cavity resonances of an insonified fluid-filled (brass) cylindrical shell in the high-frequency overlapping resonance regime, kb>30, where b is the inner radius of the shell. Hybridization of modes occurs at frequencies where resonances interfere and the resulting dissymetrization of the wave fields are evident in the experimental images. Similar behavior is seen in theoretical predictions obtained using the normal mode series solution for a shell excited by a plane wave. At very high frequencies (kb>100) the field in the cavity has characteristics that can be associated with a ray description of acoustic propagation; in these cases caustics are observed in the acoustic field.
Comments on “Effect of multilayer baffles and domes on hydrophone response” [J. Acoust. Soc. Am. 99, 1883–1893 (1996)]
Authors: Shenderov Evgeni L.
Published: July 2002

In the subject paper Ebenezer and Abraham used the transfer matrix method to investigate the response of a receiver located between a layered dome and a layered baffle. They considered this set as one multilayer system and obtained complicated matrix equations. The purpose here is to show that the sound field and the response of the receiver may be expressed as simple expressions using reflection and transmission coefficients having clear physical meaning.