bluuebunny/crossref_metadata_2025 huggingface dataset:
Speech enhancement using state-based estimation and sinusoidal modeling
Authors: Deisher Michael E. , Spanias Andreas S.
Published: July 2002

A procedure for estimating the parameters of a sinusoidal model from speech corrupted by additive noise is described. An approximate harmonic representation is used wherein voiced speech is represented by a set of sine waves at multiples of the fundamental frequency and several additional components at frequencies near each harmonic. Amplitudes and phases of the sinusoidal components are estimated using a state-based technique that employs hidden Markov models (HMMs) to classify speech and noise spectra. Voicing and fundamental frequency are determined using an analysis-by-synthesis approach. Simulation results are presented, comparing the performance of the proposed algorithm to that of the standard HMM-based minimum mean square error (MMSE) estimator. The proposed method was found to reduce the structured residual noise associated with HMM-based algorithms.
Active control of a distributed-parameter structure using vortex power flow confinement
Authors: Tanaka Nobuo , Kikushima Yoshihiro , Kuroda Masaharu , Fergusson Neil J.
Published: July 2002

This paper considers the active power flow control of a distributed-parameter planar structure, with particular emphasis on a vortex power flow which has the potential to confine the vibrational power into a restricted area of the structure. Without letting the vibrational power, a cause of exciting structural modes, disperse into the structure, control of the structural response can be achieved. This paper begins by deriving the necessary condition for producing a vortex power flow in the vicinity of a disturbance point force at an arbitrary exciting frequency. Then, with a wave visualization system newly developed, it becomes possible to observe the wave propagation (the vortex power flow) taking place in the structure. In order to investigate the contribution of structural modes to the vortex power flow configuration, an energy stream function as well as a vorticity function is derived in a general form. By using these functions, the generation mechanism of a vortex power flow actively induced around a disturbance force location is quantitatively studied.
Audible circuit noise in hearing aid amplifiers
Authors: Agnew Jeremy
Published: July 2002

Audible electronic circuit noise generated within a hearing aid is distracting to a listener in quiet situations and, if the noise level is high enough, may cause listener irritation and rejection of the hearing aid. Thus for hearing aid specification and fitting purposes, it is useful to know the acoustic levels at which this internal noise may become audible and also at which it may become objectionable. For hearing aid amplifier circuit specification and design purposes, it is useful to know the same levels in electrical terms. This paper reports on a study that used an amplifier with no acoustic input and a hearing aid receiver output to simulate internally generated hearing aid circuit noise. Results are reported for testing eight subjects with high-frequency hearing loss for the perceived acoustic and electrical levels at which internal circuit noise became both audible and objectionable.
Systems approach to sound in porous media
Authors: Lambert Robert F.
Published: July 2002

A method based on linear systems analysis is developed for estimating propagation characteristics of sound in porous media both in the fluid of the pores and in the elastic structural frame. It predicts propagation constants, pressure ratios, and velocity ratios in close agreement with previous work. The two coupled systems are visualized in the form of signal flow diagrams that are composed of transfer admittances and transfer impedances.
A cohesive lumped parameter analysis of the mechanics of the goldfish peripheral auditory system
Authors: Finneran James J. , Hastings Mardi C.
Published: July 2002

A mathematical analysis has been formulated to model the dynamic behavior of the goldfish peripheral auditory system, including the swimbladders, Weberian apparatus, and saccule. The two-chambered goldfish swimbladder is treated as a two degree-of-freedom mechanical system consisting of two coupled mass-spring-damper arrangements. The swimbladder is coupled to the Weberian ossicles using a phenomenological analysis of the anterior swimbladder tunica externa which permits both stretching and sliding. Analysis of the saccule features only a single degree-of-freedom, corresponding to the direction of orientation of the ciliary bundles. Inputs to the saccule consist of the transverse canal fluid motion and the motion of the animal’s head (assumed to match the local acoustic particle motion). Mechanical properties required for the system equations were estimated from published literature and direct measurements. Results of the analysis compare favorably to experimental data for the motions of the swimbladders and Weberian ossicles. The results indivate that the Weberian apparatus has a significant impact on the hearing ability over a broad frequency range and that the saccule functions as a displacement sensor above approximately 300 Hz. [Work supported by ONR Grant No. N00014-94-1-0337 and the ASA Hunt Fellowship.]
Ultrasonic echo signals obtained in the outdoor environment
Authors: Anderson Michael J. , Luke Jeffrey , Canning John , Edwards Dean B.
Published: July 2002

Many, if not most, applications of ultrasonic transducers in air are for ranging systems used in a relatively structured environment. We describe the application of ultrasonic transducers to range sensing for a robotic autonomous vehicle that is intended to operate outdoors in a forested environment. Unlike the indoor environment, application of ultrasonic ranging outdoors involves a much more cluttered environment. The outdoor environment contains a large number of categories of objects and features, as well as a wide variation within each category. In this talk, a statistical summary of echoes obtained from features including ground contour, roughness elements, and obstacles common in the forest environment is presented. Information that can be extracted from the echo data that is useful to an autonomous controller is then discussed.
Miniaturized ultrasonic sensor system for liquid analysis
Authors: Henning Bernd , Daur Peter C. , Wolf Alexander , Hauptmann Peter , Puettmer Alf
Published: July 2002

At the moment, known commercial devices to measure the sound velocity in liquids are limited in their application because the relation between velocity and concentration of substances is often not clear, for instance, if it is a parabolic curve. Additionally, the temperature dependence shows similar behavior. This contribution will present an ultrasonic sensor system consisting of a miniaturized multisensor arrangement for the comprehensive acoustic characterization of liquid mixtures. The sensor is based on segmented cylindrical piezoceramics and measures velocity, impedance coefficient, attenuation coefficient, and temperature. If it is a known liquid mixture it is possible to use the measuring quantities to calculate the material properties acoustical impedance and absorption or the concentration of selected substances in complex liquids. The sensor system is able to adapt itself to different and changeable absorption conditions which is typical of industrial processes. The measuring chamber is optimized to investigate small volumes of liquid specimens. In this contribution the sensor design and the developed approach for the continuous and simultaneous measurement of acoustic properties of liquids will be described. Application examples of the sensor in the chemical and food industry will show the advantages and limits of our new sensor system.
Numerical analysis of high-intensity ultrasonic processing systems
Authors: Campos-Pozuelo Cleofe , Dubus Bertrand , Gallego-Juarez Juan A.
Published: July 2002

High-intensity applications of ultrasonic energy in industrial processing are based on the performance of the power transducers and their coupling with the processing chamber. In fact, the right distribution of the acoustic field inside the treatment chamber and the efficiency of the system transducer-chamber are determinant factors for the feasibility of the applications. Therefore, the knowledge of the influence of geometry and dimensions of the processing chamber as well as the effect of the excitation transducers on the pressure field distribution is essential for the development of practical systems. This paper deals with the finite element modeling of a high-intensity ultrasonic processing system which is composed of a flexural-plate transducer and a cylindrical tube with characteristic dimensions much longer than the wavelength. A three-dimensional numerical procedure has been developed for modeling the finite amplitude acoustic field. Fundamental and second harmonic pressure distribution are calculated for several chamber geometries and excitation conditions. It has been found that the efficiency of the system is dependent on the geometry and dimensions of the chamber as well as on the efficiency, dimensions, and vibration distribution of the exciting transducer. The results give a guideline for the design of practical processing systems.
Acoustic measurements of condensation/evaporation and crystal growth
Authors: Petculescu Andi G. , Wilen Larry A.
Published: July 2002

Using a volume-modulation technique developed to study thermoacoustics, the complex compressibility of a liquid in coexistence with its vapor is measured. Such a system exhibits a distinctive behavior. At low frequencies, the inverse complex compressibility vanishes because the pressure remains at the equilibrium vapor pressure as the total volume is changed slowly. The volume change is accompanied by an exchange of molecules between the two phases. At higher frequencies, however, this exchange is too slow, and the pressure response approaches that which would be expected in the absence of the liquid phase. The presence of the liquid acts effectively as a high-pass filter whose time constant depends on the rate of condensation/evaporation. The application of this technique to the measurement of condensation coefficients of liquids will be discussed. The same technique can also be applied to solid/vapor systems where the results provide a measure of the crystal growth rate. A unique feature of this technique is that the crystal growth rate can be monitored continuously as a function of temperature. [Work supported by Ohio University Research and Sponsored Programs.]
Effects of sound and vibrations on tensions and deformations of a stratificated plate
Authors: Simion Florian-Paul I. , Simion Gabriela-Cristina D.
Published: July 2002

Effects due to sound and vibrations phenomena in bodies are multiple and more complex than those in the case of sound propagation in air. In the present paper deformations and tensions are analyzed in the case of a plate with eight layers and a solicitation in flexion. Our plate is subjected to a uniform pressure. Let us consider a Cartesian frame (O, x1, x2, x3) for our multilayer plate from composite material. Axis x3 is normal to the medium surface of the plate. This plate is composed of eight unidirectional layers and the angles between fibers of a layer and axis (O|x1) have the following values: 0, π/2, 0, π/2, π/2, 0, π/2, 0. Matrix of rigidities for a layer is determined in a rectangular base (x1,x2,x3) in case x1 parallel to the direction of fibers. A formula of medium deformated surface, arrow in the middle of plate and flexion deformation is determined. Particular application efforts in each layer are computed and their graphs are plotted.
Estimating the vibration energy of an elastic structure via the input impedance
Authors: Bobrovnitskii Yuri I.
Published: July 2002

The following problem is posed and solved: given an elastic structure vibrating under the action of a harmonic point force, find the time-average potential and kinetic energy, loss factor, and other energy characteristics of the structure if known are only the complex amplitudes of the force and velocity response at the driving point, f and v. The structure is assumed to be linear, with viscous and hysteric damping not necessarily proportional. It is shown that the problem has a mathematically exact solution only for lossless systems. For structures with losses, there exist rather accurate estimates valid at low and middle frequencies. The main result is the equation relating the total vibration energy of the structure to the derivative of its input impedance, f/v, or mobility, v/f, with respect to frequency. Computer simulation examples with typical structures (rod, plate) illustrate the accuracy and the range of validity of the estimates. The results presented allow one to obtain the energy characteristics of a forced vibrating structure by the most economic way: without measuring or computing the response all over the structure and using only the data measured at one singular point.
Vocal tract shape estimation using three noninvasive transducers
Authors: Long Russel , Story Brad , Titze Ingo
Published: July 2002

Sentence-level speech simulation requires a description of vocal tract shape parameters as a function of time. Vowel-like configurations can often be derived from a microphone signal; however, the influence of consonants may be more easily detected with the use of additional signals. The electroglottograph (EGG) and an articulatory transducer [McGarr and Lofqvist, J. Acoust. Soc. Am. 72, 34–42 (1982)] are employed to increase the accuracy of vocal tract shape estimation. The microphone signal is analyzed on a frame-by-frame basis for spectral features, energy, and zero-crossing rate. The EGG provides information regarding voicing onset and offset, and the articulatory signal is used to indicate closure and lip rounding. These data are combined to select an appropriate area function for each frame of the sentence. The resulting temporal map of area functions is interpolated and sent to a wave reflection simulator to reconstruct the speech. [Work supported by NIH Grant No. DCO2532.]
3-D ultrasound imaging of the prostate
Authors: Fenster Aaron , Downey Donal
Published: July 2002

An important aspect that needs improvement in medical ultrasound systems is related to the 2-D imaging of the prostate. 2-D viewing of 3-D anatomy limits our ability to quantify and visualize prostate disease and is partly responsible for the reported variabilities. This occurs because: (i) the diagnostician must integrate multiple 2-D images in his mind during the procedure, leading to inefficiency and variability; (ii) The 2-D ultrasound images represent a thin plane at some arbitrary angle in the body, making it difficult to localize the image plane. To overcome these difficulties, we have developed a 3-D ultrasound system to image the prostate. Our 3-D ultrasound imaging system consists of: a conventional ultrasound machine and transducer; a custom-built assembly for rotating the probe under microcomputer control; a microcomputer with a video grabber; and software to reconstruct and display 3-D images. A typical scan of 200 2-D B-mode images takes only 13 s, and the reconstruction less than 1 s. This paper will detail the 3-D imaging approach and its use for imaging the prostate in 3-D. Various applications will be discussed related to prostate cancer diagnosis, prostate volume measurements, and 3-D ultrasound-guided therapeutic procedures such as cryosurgery.
Tracking and correcting for organ motion artifacts in ultrasound tomography systems
Authors: Dhanantwari Amar C. , Stergiopoulos Stergios
Published: July 2002

Motion artifacts have been identified as a problem in medical tomography systems. This problem, however, is well known in other types of real-time imaging systems such as radar satellites and sonars. In this case it has been found that the application of an overlap processing scheme [J. Acoust. Soc. Am. 86, 158–171 (1989)] increases the resolution of a phased array imaging system and corrects for motion artifacts as well. Reported results have shown that the problem of correcting motion artifacts in synthetic aperture applications is centered on the estimation of a phase correction factor. This correction factor is then used to compensate for the temporal phase differences between sequential sensor-array measurements in order to synthesize the spatial information coherently. This paper describes an approach which tracks the organ motion and allows the artifacts to be isolated in ultrasound tomography systems. Two sources are utilized so that two sets of projections are generated that are identical in space but separated in time. Then the spatial overlap correlator processing scheme is used to synthesize the 2-D projection data coherently. This provides the desired phase correction factor, which compensates for the phase fluctuations caused by the subject’s organ-motion effects and tracks the organ motion.
A practical model for high-frequency seabed bistatic scattering strength
Authors: Jackson Darrell R. , Ivakin Anatoliy N.
Published: July 2002

The authors have previously reported a model for bistatic scattering by elastic seabeds. This model is extended here to cases of larger roughness by replacing the rough-interface perturbation approximation with the small-slope approximation [Yang and Broschat, J. Acoust. Soc. Am. 96, 1796–1804 (1994)]. Consistency with older models is shown by comparisons of calculations for silt and sand examples. Correlations between volume fluctuations of different types (e.g., density and compressional wave speed) are considered, and it is shown that the effects of such correlations are more readily observed in bistatic scattering measurements as opposed to backscattering measurements. Finally, the importance of elastic effects in scattering by rocky seabeds is illustrated. [Work supported by ONR.]
High-frequency bistatic scattering from sediments—experiments and modeling
Authors: Williams Kevin , Tang Dajun
Published: July 2002

Typically, for frequencies in the 10–100 kHz range, the interaction of sound with the ocean bottom is a scattering process. Use of bistatic geometries can give insight into the scattering process not possible via traditional monostatic experiments. The trade-off is that such experiments are more difficult and more data are needed to get statistically meaningful results to compare with models. During the last 5 years, the Coastal Benthic Boundary Layer (CBBL) program allowed the opportunity to develop and fine-tune one method of obtaining bistatic data. That evolution will be briefly described and the data from three sites (one mud, one sand, one sand-silt-clay) shown. The sand and sand-silt-clay site data are compared with a model based on surface roughness and volume perturbation scattering. The mud site had methane bubbles embedded within it and the data are compared with a model based on bubble scattering. The physical insight derivable from the model/data comparison in the mud case will be discussed. [Work supported by ONR.]
A fast integral equation approach to acoustic scattering from three-dimensional objects using a natural basis set
Authors: Moroney D. T. , Cullen P. J.
Published: July 2002

Boundary value integral equations and the moment method solution technique provide a succinct and elegant strategy for the solution of acoustic surface scattering problems. This paper explores the application of a subdomain basis set, based on the phase of the incident radiation, which is used to solve for the unknown normal pressure gradient on the surface of the scatterer using the moment method. The advantage of this basis set lies in the fact that it can accurately represent the fast phase character of the pressure gradient on the surface of the scatterer. This allows for far fewer discretizations/basis elements in the moment method formulation and therefore significantly reduces the density of unknowns that must be numerically computed. The main contribution of this paper is to show how to efficiently employ this natural basis and to explore the physical justification for using this approach. The method is compared with other techniques including the Kirchhoff solution technique, high frequency single scattering techniques, the Nussenzveig–Fock technique, and the parabolic equation approximation. Unlike these methods no approximation to the physical system need be introduced.
Known source detection predictions for higher order correlators
Authors: Pflug Lisa A. , Ioup George E. , Ioup Juliette W.
Published: July 2002

The problem addressed in this paper is whether higher order correlation detectors can perform better in white noise than the cross correlation detector for the detection of a known transient source signal, if additional receiver information is included in the higher order correlations. While the cross correlation is the optimal linear detector for white noise, additional receiver information in the higher order correlations makes them nonlinear. In this paper, formulas that predict the performance of higher order correlation detectors of energy signals are derived for a known source signal. Given the first through fourth order signal moments and the noise variance, the formulas predict the SNR for which the detectors achieve a probability of detection of 0.5 for any level of false alarm, when noise at each receiver is independent and identically distributed. Results show that the performance of the cross correlation, bicorrelation, and tricorrelation detectors are proportional to the second, fourth, and sixth roots of the sampling interval, respectively, but do not depend on the observation time. Also, the SNR gains of the higher order correlation detectors relative to the cross correlation detector improve with decreasing probability of false alarm. The source signal may be repeated in higher order correlations, and gain formulas are derived for these cases as well. Computer simulations with several test signals are compared to the performance predictions of the formulas. The breakdown of the assumptions for signals with too few sample points is discussed, as are limitations on the design of signals for improved higher order gain. Results indicate that in white noise it is difficult for the higher order correlation detectors in a straightforward application to achieve better performance than the cross correlation.
An analysis of the effect of basilar membrane nonlinearities on noise suppression
Authors: Billa Jayadev , El-Jaroudi Amro
Published: July 2002

Computational models of the peripheral auditory system have largely modeled basilar membrane (BM) mechanics as a linear filter-bank-like entity. Recent mathematical work on the nature of auditory system noise suppression allows us to analyze and argue for the incorporation of BM nonlinearities into these models. This analysis shows that vowel perception improves with increasing presence of BM nonlinearities whereas consonant perception degrades with increasing influence of BM nonlinearities. Experimental results on tones and real speech corrupted by noise corroborate the analysis as well as suggest a novel approach to speech processing.
Sound fields caused by diffuse-type reflectors with periodic profile
Authors: Takahashi Daiji
Published: July 2002

For the purpose of providing highly diffuse reflections, the reflection surface is often periodically corrugated. The degree of diffusion of this periodic type diffuser can be evaluated by an objective criterion named DNSD [D. Takahashi, J. Acoust. Soc. Jpn. (E) 16, 51–58 (1995)], the value of which varies in the range 0–1; DNSD=0 for a perfect diffusion, and DNSD=1 for a specular reflection. Optimum diffuse reflectors with periodic profiles can be designed by using this criterion, but this type of diffusion might have some aspect of misgivings due to its periodicity, which may be a kind of so-called ‘‘tone coloration.’’ In other words, the highly diffuse reflections might have a problem of some particular effect on the spectrum caused by the interference between the direct and the reflected waves, and the effect might be different from an ordinary case of the plane surface. In this report, for the three types of reflectors, the calculated results of the SPL characteristics of the reflected field as well as the diffusion performances are presented and mutually discussed in comparison with the measured data from 1/8-scale model experiments.
On the acoustical characteristic of a balloon
Authors: Nash Anthony P.
Published: July 2002

It is common to use a transient acoustical signal when testing the properties of large architectural spaces. Some of the traditional signal sources include pistol shots, pulses from loudspeakers, etc. Assuming the background noise is reasonably low, an inflated balloon can be a very effective signal source in this application. The published literature contains little documentation regarding the sound power, directional properties, and repeatability of an exploding balloon. A carefully controlled experiment was conducted involving a series of balloons exploded in an environment where the closest reflecting surface was located more than 15 m from the source. Several microphones ringing the source were used to measure the free-field acoustical transient on a multi-channel tape recorder. The measured data will demonstrate that a properly inflated balloon is a very satisfactory (and lightweight!) sound source.
The use of two freqencies to interpret acoustic scattering layers
Authors: McKelvey Denise R.
Published: July 2002

The use of multiple frequencies during acoustic stock assessment surveys allow methods to be used, which can discriminate between different species groups based on their scattering properties and assist in target species identification, thus improving estimates of biomass. Research, using multiple frequencies to study zooplankton, have used the difference in backscatter between several frequencies to identify the species or species groups comprising the scattering layers. This paper presents the results of using a dual-frequency differencing algorithm on 120- and 38-kHz mean volume backscatter strength (MVBS) data collected during a 1995 United States west coast acoustic survey of Pacific hake (Merluccius productus) as a means to acoustically separate hake from zooplankton. Scatterers were sampled using various nets with mouth areas ranging from 5 to 1000 m2. Backscatter data from both frequencies were corrected for background noise. The effect of species composition, time of day, depth, and density of scatterers on the (delta)MVBS data were evaluated. Results indicate that the dual-frequency differencing algorithm shows a marked difference between fish and zooplankton (delta)MVBS and can be used to distinguish between fish and zooplankton scattering layers.
Use of two pulses to control cavitation in lithotripsy
Authors: Bailey Michael R. , Cleveland Robin O. , Blackstock David T. , Crum Lawrence A.
Published: July 2002

In lithotripsy acoustic cavitation appears to play a role in both comminution of kidney stones and damage to tissue. To investigate the role of cavitation, we used a pair of confocal electrohydraulic lithotripters (ellipsoidal reflectors). A delay in firing of Δt modified the cavitation field without altering the peak positive and negative pressures. Bubble collapse time tc, measured by passively detecting acoustic emissions generated by the bubble, was used as a measure of cavitation activity. A two-pulse sequence from the source shortened tc relative to the single pulse value tc1. Collapse times calculated by using the Gilmore equation agreed well with measurements. Relative intensity of bubble collapse was determined by depth of pits created in aluminium foil. For pulse delays Δt<0.3tc1 the pit size decreased, a result that implies the second pulse stifled the collapse. Conversely, for delays in the range 0.5tc1<Δt<tc1, cavitation apparently intensified, since pit depth increased by a factor of up to 2. Pit depth correlates well with (calculated) pressure radiated by the bubble. When the two reflectors were pointed at each other and fired simultaneously, pitting was localized to a spot less than 1 cm in diameter. [Work supported by ONR, ARL:UT IR & D, and NIH PO1-DK43881.]
Modeling acoustic radiation from end-initiated explosive line charges
Authors: Marshall William J.
Published: July 2002

Acoustic radiation produced by end-fired explosive line charges has been examined experimentally and theoretically. In terms of directivity effects, line charges are found to behave like beam-steered continuous arrays over moderately wide bands. This talk briefly summarizes measured waveforms and derives a math model which predicts levels and spectrum shapes from such sources over a wide range of view angles and source characteristics. The model is driven by two parameters which may be extracted from experimental data. The result is a practical means of designing explosive line arrays to desired source levels, bandwidths, and beam patterns. [Work supported by DARPA.]
The estimation of an interior sound field by source methods
Authors: Too Gee-Pinn James , Wang Shing Maw
Published: July 2002

In an earlier study, three different source methods (SSM, similar source method; IPSM, internal parallel source method; ISM, internal source method) were successfully developed to estimate radiation and scattering sound field. All these are methods of estimating exterior sound fields which are not suitable for estimating interior sound fields. In this study, the similar source method is modified to estimate the interior sound field. The modification is to move the sources to somewhere outside the boundary surface in order to estimate the interior sound field and to prevent the singularity problem when the source point is close to the field point. Finally, the sound field inside a 2D infinite cylinder and in a car will be estimated. The results will be compared with the results obtained by the boundary element method.
Nondestructive acoustical forced oscillation method of fatigue cracks
Authors: Gelman Leonid M. , Kondratyuk Lyudmila V.
Published: July 2002

For nondestructive testing and evaluation of fatigue cracks the acoustical forced oscillation method with nonstationary excitation is used. The testing object model as a nonlinear oscillator is considered. The nonlinear forced oscillations of the testing object model are investigated. The new decision method (‘‘equivalent frequency’’ method) of nonlinear differential equations which describe the object forced oscillations is proposed and investigated. Comparison of the proposed method with the classical decision method is given.
Physical and chemical sensing applications of acoustic devices
Authors: Martin Stephen J.
Published: July 2002

Acoustic devices are finding a number of applications as physical and chemical sensors. Thickness-shear mode resonators, for example, can be operated in a fluid to measure properties such as density and viscosity. These devices are being developed for in situ monitoring applications, including engine oil for condition-based maintenance. The surface acoustic wave (SAW) device serves as a versatile platform for constructing gas-phase chemical sensors. These devices serve as extremely sensitive gravimetric detectors with chemical selectivity conferred by depositing a chemically sensitive film onto the device surface. Selectivity can be further enhanced by using arrays of chemical sensors combined with a pattern recognition algorithm. Flexural plate wave (FPW) devices, consisting of a self-supporting membrane in which acoustic waves are excited, can be used in a number of sensing applications. These devices are sensitive to either mass accumulation or a change in membrane tension. Chemical sensors can be constructed by depositing a chemically sensitive film onto the membrane surface; species absorption leads to a change in the membrane’s areal mass density. Alternatively, sensors for pressure and acceleration can be constructed which rely on the device’s sensitivity to membrane tension. Sensor systems using these various sensor platforms will be described.
Historical sketches I. The acoustical contributions of Karl Rudolph Koenig
Authors: Beyer Robert T.
Published: July 2002

While the acoustical contributions of Helmholtz, Rayleigh, and Bell are remembered, many of the secondary lights of acoustics in the nineteenth century have faded away. This is the first of what is hoped to be a series of recollections of a number of them. One such leader was Karl Rudolph Koenig. Born and educated in Koenigsberg, Germany (now Kaliningrad, Russia), he spent his adult life in Paris, where he established a laboratory for making acoustical instruments, including tuning forks, resonators, and devices for the visualization of sound and for obtaining ultrasonic frequencies. Details of some of his instruments and discoveries will be presented and his role assessed.
Nonaxisymmetric disturbances in a jet and their effect on structural loading
Authors: Bayliss Alvin , Maestrello Lucio
Published: July 2002

A model of sound generated in a high subsonic (Mach 0.9) circular jet is solved numerically in cylindrical coordinates for nonaxisymmetric disturbances. The jet is excited by transient mass injection by a finite duration pulse via a rotating ring source. The flow field near-field and far-field pressure disturbances corresponding to these sources are described. In particular, the resulting pressure field which would serve to excite nearby panels is illustrated together with results on the excitation of thin slices of nearby panels. Considered are both the short-time behavior of the jet and the long-time behavior, after the initial excitation pulse has exited the computational domain.
Vibration of a cavitating elastic wing in a periodically perturbed flow: Excitation of subharmonics
Authors: Kovinskaya Svetlana I. , Amromin Eduard L.
Published: July 2002

Vibration of an elastic cavitating wing in periodically perturbed flows is analyzed. Because cavity thickness and length are perturbed, too, an excitation with a fixed frequency leads to a parametric vibration of the wing, and this vibration spectra’s amplitudes have nonlinear dependencies on amplitudes of the perturbations. Numerical analysis was carried out for two-dimensional flow of an ideal fluid. Wing vibration was described by the equation for a beam in bending motions. As a result, two frequency bands of an essential vibration increase are found. A high-frequency band is mainly associated with an elastic resonance of the wing, and a cavity can do certain damping there. A low-frequency band is associated with cavity volume oscillations. The governing parameter for the low-frequency vibration is the Strouhal number (Sh) based on the cavity length. The most significant vibration in the low-frequency band corresponds to approximately constant values of Sh and has the most extensive subharmonics.
Frequency constants for transverse vibration of annular disks
Authors: Gabrielson Thomas B.
Published: July 2002

Frequency constants for the transverse vibration of thin, annular disks are presented. All nine combinations of the boundary conditions, free, simply supported, and clamped, are included for Poisson’s ratios of 0.0, 0.3, and 0.5. Many of these cases have been treated earlier in the literature but with occasional, significant error. Consequently, several tests of the validity of the present solutions are described.
Speech intelligibility model including room and loudspeaker influences
Authors: Faiget L. , Ruiz R.
Published: July 2002

Loudspeaker directivity and frequency response are of great importance for speech intelligibility estimation. In this work their respective influence is introduced in a new predictor. Properties of the model are in good agreement with expected variations of scores when radiation and frequency response are modified. An experiment shows the accuracy of the predicted scores. Limitations of the model are discussed and future research perspectives are presented.
Synthesis of optimal, single-frequency, passive control laws, with application to reducing the acoustic radiation from a submerged spherical shell
Authors: Titterton Paul J.
Published: July 2002

This paper uses (i) a network model for vibrating and radiating structures, (ii) network-scattering variables, and (iii) semi-definite programing to synthesize load admittances which achieve performance bounds for single-frequency, multi-port passive control of acoustic radiation. The network model relates the disturbance, regulated output, and the force and velocity at control-load attachment points. The semi-definite program minimizes the maximum singular value of a weighted, single-frequency, closed-loop, disturbance-to-regulated-output transfer matrix, while maintaining the passivity of the load. Three design examples demonstrate control of single-frequency radiated power from a (mathematically modeled) submerged spherical shell. First, we minimize the power radiated into a 30° far-field sector for two configurations: (i) one disturbance with one control load, and (ii) two disturbances with three control loads. For 4⩽ka⩽7, radiated power is reduced by 10–20 dB. This reduced radiated power is compared to the conjugate-matched-load radiated power, which is greater than the uncontrolled at almost every frequency. Second, we show that the optimal-passive radiated power is sensitive to the phase of the uncontrolled response at the attachment point of the load. Third, we remove the passivity constraint to show that the best (active or passive) controller is often passive. When the optimal is active, the radiated power is only a few decibels less than the optimal passive. Our technique’s primary shortcoming is that the quieting is optimal at only a single frequency. Broadening the control bandwidth is a topic-of current research.
Evolution of the Journal: Early history and overview
Authors: Pierce Allan D.
Published: July 2002

The new Editor-in-Chief of the Acoustical Society of America gives an editorial discussion of the history of the Journal of the Acoustical Society of America. Emphasis is given to the earlier years in the Journal’s 70 year history and to the evolution of the Office of Editor-in-Chief. A dominant driving force throughout the history of the Journal has been that of fulfilling the Society’s purpose—to increase and diffuse the knowledge of acoustics and to promote its practical applications.
Wave number frequency (k-ω) analysis using a wavelet transform and an eigenvalue decomposition
Authors: Salisbury John I.
Published: July 2002

In a previous paper [Salisbury, J. Acoust. Soc. Am. 96 (1994)], the spacial resolution of a conventional KW (2D FFT) was improved by the use of an eigendecomposition in the spatial domain. In this letter, a new method for generating four-dimensional wave number frequency-time (k-ω-t) vs level plots is presented. It combines eigendecomposition in the space domain and a wavelet transform in the time domain. This technique uses the true broadband continuous Wavelet Transform (WT). This combination generates k-ω plots that are functions of time, and is a significant advance over existing methods for analyzing broadband impulse type and nonstationary signals. The WT-ED technique has wide ranging applicability from diagnosis of acoustic and nonacoustic source generating mechanism to medical imaging technology.
Boundary conditions for the weak formulation of the mixed (u,p) poroelasticity problem
Authors: Debergue Patricia , Panneton Raymond , Atalla Noureddine
Published: July 2002

This paper presents the boundary conditions that apply to the weak integral formulation of the Biot mixed (u_,p) poroelasticity equations. These boundary conditions are derived from the classical boundary conditions of the Biot displacement (u_,U_) poroelasticity equations. They are applied to the surface integrals of the associated weak form to account for exterior excitations, supports, and couplings with exterior elastic, acoustic, poroelastic media, and a septum. It will be shown that the derived boundary conditions for the (u_,p) formulation lead to simpler finite element equations compared to those obtained from the (u_,U_) formulation. Finally, two numerical examples are presented to validate the poroelastic-septum coupling condition, and to highlight the limitations of the free edge condition on a poroelastic medium.
Modeling of Lamb waves generated by integrated transducers in composite plates using a coupled finite element–normal modes expansion method
Authors: Moulin Emmanuel , Assaad Jamal , Delebarre Christophe , Osmont Daniel
Published: July 2002

Thin piezoelectric transducers attached to or embedded within composite structures could be used for in situ structural health monitoring. For plate-shaped structures, the useful ultrasonic vibration modes are Lamb waves. Preliminary testing has already demonstrated the suitability and practical feasibility of such integrated transducers, but better control of the generation of Lamb modes seems to be necessary. Therefore, an original modeling approach has been developed, which can be used to design and optimize these “sensitive materials.” This modeling technique allows the determination of the amplitude of each Lamb mode excited in a composite plate with surface-bonded or bulk-embedded piezoelectric elements. The method consists of a coupling of the finite element method (FEM) and the normal modes expansion method. The limited finite element mesh of the transducer and its vicinity enables the computation of the mechanical field created by the transducer, which is then introduced as a forcing function into the normal modes equations. The adequacy and accuracy of this modeling method have been numerically and experimentally verified.
A strip-element method for analyzing wave scattering by a crack in an immersed axisymmetric laminated composite cylinder
Authors: Xi Z. C. , Liu G. R. , Lam K. Y. , Shang H. M.
Published: July 2002

A strip-element method is presented for analyzing wave scattering by a crack in a laminated composite cylinder immersed in a fluid. In this approach, two-nodal-line and three-nodal-line axisymmetric strip elements are employed to model the fluid and laminated cylinder, respectively. Governing equations for the fluid and solid elements in the frequency domain are derived with a variational method and the Hamilton principle. The associated characteristic equations in the wave-number domain are obtained through Fourier transform techniques. Responses of the fluid-loaded cylinder to a line load are found by a modal-analysis method and inverse Fourier transform techniques. Numerical results are presented for cracked laminated composite cylinders submerged in water. Water is found to have strong influence on the scattered wave fields in a cracked laminated composite cylinder.
The Flow of Moderately Concentrated Polymer Solutions in Water
Authors: Rodriguez F. , Goettler L. A.
Published: July 2002

The flow curves for four water-soluble, non-ionic polymer types have been characterized using rotational viscometers primarily. Molecular weight and solution concentration variations gave a total of twenty-five curves. Polyacrylamide, poly(ethylene oxide), hydroxyethyl cellulose, and methyl cellulose were studied. A two-parameter model that gives a good fit to the data over five decades of shear-rate is: log (ηr)/log (ηr)0=0.68−0.32 erf {[log (τγ̇)−log B]/2.272} In this equation, ηr is the relative viscosity; (ηr)0, the same at zero shear-rate, erf, the error function; (τγ̇), the rate of energy dissipation; and, B, the value of (τγ̇) at the inflection point of the flow curve. Furthermore, B is independent of concentration.
Linear Free Energy Effects in Poly(vinyl Chloride)-Ester Systems from Tensile Creep Compliance, Melt, and Solution Viscosity Techniques
Authors: Hammond R. J. , Smoley E. M.
Published: July 2002

Current literature indicates that considerable effort is being made to relate rheological behavior of various materials to molecular mechanisms of flow. Implicit in viscoelastic spectra are the molecular motions and configurations that give shape to the stress relaxation or creep compliance curves. In dilute solutions or concentrated melts at higher temperatures, flow curves give indications of molecular arrangements present which cause deviation from some previously defined standard. Both qualitative and quantitative descriptions of solution and flow mechanisms recognize the importance of intermolecular forces. While these treatments can be used with confidence in systems of low polarity, highly polar solvent-solute mixtures are not adequately described by these relations. Our primary considerations here are directed at understanding the nature of the interaction of 2-ethylhexyl carboxylates with poly(vinyl chloride) and its model 1,3-dichloropropane. The method employed represents a departure from conventional thought in that rheological behavior, from tensile creep compliance, dilute solution, and melt viscosity, has been successfully correlated to both Hammett and Taft substituent constants as implied in Eyring's concept of absolute reaction rates. While changes in interaction free energies between solvent and ester evolve simply and naturally from this technique, the significant conclusion obtained from these data is that the generally accepted “hydrogen-bonding” interaction hypothesis of poly(vinyl chloride) with esters is clearly absent.
Rheological Properties of Disperse Systems of Spherical Particles in Polystyrene Solution at Long Time-Scales
Authors: Matsumoto Takayoshi , Hitomi Chiyoji , Onogi Shigeharu
Published: July 2002

The dynamic and steady flow properties of disperse systems of styrene–divinylbenzene copolymer particles in a polystyrene solution have been measured over wide ranges of frequency, shear rate, and strain amplitude by means of a cone-and-plate type rheometer. The main results may be summarized as follows. 1) These systems show Newtonian behavior at extremely low rates of shear, that is, the apparent viscosity is approximately constant. This fact indicates that the systems have no yield stress, although they appear to show one if only the behavior at high shear rates is considered. 2) They show linear viscoelastic behavior at strain amplitudes less than 0.5%, but striking nonlinearities at larger strains. However, at very long time-scales, these systems are linearly viscoelastic and independent of the strain amplitude. 3) The nonlinear viscoelastic functions G1′ and G1″ decrease with increasing strain amplitude, but they are almost independent of strain for strains larger than 50%, over the entire frequency range. 4) The relaxation spectra for these disperse systems consist of two parts: one is the box type portion in the long time-scale region, where the intensity is very sensitive to strain; the other appears in the short time-scale region and is not sensitive to strain. 5) |η*| coincides well with the Newtonian viscosity at extremely low shear rates or frequencies, but the empirical law proposed by Cox and Merz does not hold at higher values. Thus, the rheological behavior of these disperse systems cannot be understood without considering the three-dimensional network structure formed by the suspended particles. On the basis of these results, a new concept for the yield stress of disperse systems is proposed and discussed.