bluuebunny/crossref_metadata_2025 huggingface dataset:
Dependence of multibubble sonoluminescence intensity on the sound field in a sonochemical reactor
Authors: Mitome Hideto , Kozuka Teruyuki , Tuziuti Toru , Wang Liming
Published: July 2002

Since sonochemical reaction is related to the generation of acoustic cavitation bubbles, sonoluminescence induced by the collapse of bubbles can be a measure to specify the reaction field. The present paper discusses dependence of multibubble sonoluminescence intensity on the sound field in a sonochemical reactor to specify the cavitation field quantitatively. Deionized and distilled water was filled in a square reactor cell 50×50 ×140 mm, which was settled in a temperature-controlled water bath, and was irradiated by cw ultrasound changing the frequency from 20 to 250 kHz for various values of water depth and temperature. The intensity of sonoluminescence was measured by a photomultiplier tube with a converging lens ensuring all the sonoluminescing position was detectable. The experimental results show that the luminescence intensity is very sensitive to the water depth. A change as small as 1 mm alters the vibration mode in the cell. The intensity is also strongly dependent on the amount of dissolved air and temperature. Correlation between the luminescence intensity and the harmonics in the ultrasonic waveform generated by nonlinear vibration of bubbles is shown. [Work supported by Japan Small Business Corporation.]
Problems of ultrasonic energy transferring into liquid-phase load
Authors: Abramov Oleg V. , Abramov Vladimir O. , Bulgakov Vitaly N. , Gradov Oleg M.
Published: July 2002

The rational circuits of construction and modes of operations for a system: electric generator, electroacoustic transducer, sonotrode system, irradiator, and liquid phase are considered from the point of view of transferring vibrations of maximum power into the load. The analysis has shown that for realization of vibration transfer of the greatest possible acoustic power created by the electroacoustic transducer, it is necessary to use the sonotrode system with developed surface. It can be realized by using an irradiator of the tubular form, in which the longitudinal fluctuations are transformed into radial ones. Calculations of tubular type sonotrode systems, based on use of the analytical approaches and of computer modeling, are conducted. A number of sonotrode systems that transform longitudinal vibrations into ones, extending in a radial direction in relation to axes’ tubular irradiator, is made and tested. For improving the technological efficiency of the device, the tubular irradiator form was optimized to increase the number of the cavitational bubbles beneficially worked in the liquid and intensity of hydroacoustic streaming. So, for increasing the number of the cavitational bubbles on the external surface of the tubular irradiator at the high-amplitude zones for the longitudinal vibrations, the cross lugs are formed. The stand for valuation of acoustic capacity, entered in liquid load, is assembled, and experimental research at the choice of optimum modes of ultrasonic processing of liquids with various physical properties (viscosity, surface tension, density) is conducted.
Enhancement of ultrasonic cavitation yield by a bifrequency irradiation and its frequency effect
Authors: Feng Ruo , Zhu Channgping , Li Huamao , Chen Zhouhua
Published: July 2002

The ultrasonic cavitation yield given by a combining orthogonal irradiation at frequencies of 28 kHz and around 1 MHz is studied experimentally by using electric detection method. It is shown that the cavitation yield produced by the bifrequency irradiation is much larger than the sum of the yields produced separately by the two irradiations. For instance, when the intensity of 28-kHz ultrasound is fixed but that of 0.87-MHz ultrasound changes in the range of 4–7 w/cm2, the cavitation yield of the combining irradiation is equal to 1.9–3.4 times of the sum of the yields given separately by the two irradiations. The ultrasound beams of 28 kHz combined separately with 1.0 and 1.7 MHz are also used. The results show that the enhancement of cavitation yield by bifrequency irradiation is notably dependent on the used frequencies. When the intensity of 0.87-, 1.0-, and 1.7-MHz ultrasound is taken 6.5 w/cm2, the combining irradiation gives 4.4, 3.2, and 1.8 times the cavitation yield of 28-kHz irradiation, respectively, which is similar to that obtained previously by using single-frequency ultrasound irradiation. The authors would like to acknowledge Professor T. J. Mason for his valuable suggestion.
Effects of disorder and nonlinearity on the propagation of classical waves
Authors: Richoux Olivier , Depollier Claude , Hardy Jean , Brezini Abderrahmane
Published: July 2002

The interplay between the effects of disorder and nonlinearity on the propagation of classical waves is examined by means of an analytical model and numerical simulations. A quasi-one-dimensional string is loaded by N masses, each one fixed to a spring. Disorder is introduced onto the system by considering masses and/or lattice spacing as random variables. Nonlinearity is assumed to arise from the dynamical potential associated to each spring. The wave propagation is formulated in terms of the transfer matrix. The Lyapunov exponent is computed for various system size, yielding the spectrum and the localization length. The numerical simulations have been performed for the linear ordered case which serves as support. The purely disorder linear system offers a direct realization for the observation of the classical Anderson localization. Disorder in mass perturbs the allowed band from the upper edge in contrast to the disorder in position from both edges, the latter appears more efficient in inducing the Anderson localization. The nonlinear system in presence of both order and disorder exhibits bandwidths greater than their respective similar linear case. These findings suggests strongly that nonlinear waves are robust enough to propagate through the system even in the presence of disorder.
Nonlinear vibroacoustical free oscillation method for crack detection and evaluation
Authors: Gelman Leonid M. , Gorpinich Sergey V.
Published: July 2002

For detection and evaluation of cracks, the vibroacoustical method of free oscillations, based on nonlinear dynamics of a tested object, is widely used. However, in spite of wide practical application, the theoretical basis of this method is insufficiently investigated. The theoretical research of the decrement of the damped nonlinear free oscillations is given in the presence of a crack in a tested object. New generalizations of the decrement for nonlinear oscillations are proposed and investigated. New analytical expressions between the decrement and relative size of a crack, factors of damping, and the natural frequency of a tested object without a crack are received, on the basis of which a new testing feature is proposed and investigated. The cases of small and large damping are considered. The results obtained allow one to explain the phenomena that appeared at the method usage. [Work supported in part by the John D. and Catherine T. MacArthur Foundation.]
Nonlinear dynamic behavior of a piezoelectric 1-3 composite
Authors: Royston Thomas J. , Houston Brian H.
Published: July 2002

The nonlinear vibratory behavior of a smart material component, a 1-3 piezoceramic composite, is characterized theoretically and experimentally. The developed theoretical model for the electroelastic behavior of the 1-3 composite follows conventional assumptions made by prior investigators but includes higher-order electrical, mechanical, and electromechanical terms in the constitutive equations for the embedded PZT-5 phase. Dynamic experimental measurements of the 1-3’s mechanical response to harmonic electrical excitation over a range of excitation frequencies and mechanical loading conditions quantify the level of higher harmonic content (harmonic distortion) in the device and illustrate the dependence of this on the mechanical coupling conditions of the component to its surrounding. While this study focuses on a particular piezoelectric device, the techniques developed are applicable to the wide range of smart materials and structures which exhibit significant nonlinearity, including those based on piezoelectric, electrostrictive, magnetostrictive, and electrorheological technologies, to name a few. [Work supported by ASEE/NRL Summer Faculty Program.]
Using acoustic impulses to detect buried objects
Authors: Don Charles G. , Lawrence David E. , Rogers Andrew J.
Published: July 2002

A detector of nonmetallic buried objects, such as land mines, has been developed using acoustic impulses with a peak energy around 1 kHz. The initial proposal was to compare the difference in signals from two microphones spaced equally on either side of the sound source held a few centimeters above the ground. Ideally, over a uniform surface the difference signal is zero, however, when one microphone is over an object an additional reflected pulse remains after subtraction. In practice, this pulse is small and often obscured by noise. Better results have been obtained if data from a single microphone is subtracted from a ‘‘reference‘‘ waveform. Some problems which have to be overcome are optimizing the alignment of the two pulse trains and deciding whether or not to normalize the signals prior to subtraction. If care is not exercised, either process may distort or mask the required object reflection. This small reflected signal can be further enhanced, compared to the background noise, by correlating with an appropriate known waveform. Mention will also be made of the effects of different media and surface contours.
Environmental impact on phase coherent underwater acoustic communications: A physics based approach
Authors: Yang T. C. , Al-Kurd A.
Published: July 2002

Phase coherent acoustic communication systems, which employ joint adaptive channel equalization and phase-locking synchronization, have been shown to yield a much higher symbol rate (e.g., 2 kb/s at 3.5 kHz) by successfully tracking and updating time varying phase fluctuations in signals dominated by multipath components. This communication technique holds high promise for many applications. Its performance, however, can strongly influence (and could be limited by) the signal and noise fluctuation characteristics of the propagation channel. A statistical underwater acoustic communication model which incorporates random media propagation physics is needed to predict the performance of phase coherent acoustic communication algorithms. In this paper, the ocean acoustic propagation physics and signal processing issues which must be addressed to develop a physics-based performance prediction model are outlined. Acoustic communication simulation results for a dynamic underwater acoustic channel with time varying internal waves, fine and microfine structures, and surface waves are presented. Initial performance assessments (predictions) are given based on previously measured signal fluctuation statistics as characterized by the signal amplitude fading and phase spectra. [Work supported by the Office of Naval Research.]
The development of room acoustical demands on operas within the last 50 years
Authors: Müller Gerhard , Müller Helmut A.
Published: July 2002

After World War II, many destroyed operas in Europe required reconstruction. Since the period of the royal operas was past, architects tried to develop new shapes based upon the new social philosophy. For the acoustical planning, this has led to the following goals: (1) equal acoustical quality in all areas of the auditoria, (2) high speech intelligibility, and (3) uniform sound transmission from the pit and the stage to the audience. The deducted measures were the following: (1) application of an arenalike seating arrangement of the public to expose everybody to a strong direct sound, (2) low reverberation, and (3) reflection of sound energy to compensate the increasing distance of the listeners from the sound sources. These principles have led to the realization of slightly fan-shaped rooms with a relatively small volume or additional sound-absorbing claddings. Surprisingly, these opera halls have been quoted worse than the old ones, by the musicians and the audience. The reason for the lower reputation of the operas, designed applying the rules of the 1950s, will be explained with the help of two examples in which improvements have been realized afterwards. The measured relevant room acoustical data will be presented and the differences discussed.
Alternate venues for opera performances. Wagner started it...should we retreat now?
Authors: Jaffe Christopher
Published: July 2002

Although there has been a resurgence of interest in opera over the last 15 years in America the current outlook for continued financial support for this form of musical theater as well as classic concerts is bleak. At one time opera was enjoyed by the unwashed as well as sophisticates and a number of today’s creative opera directors are trying to appeal to a broader segment of the market. This paper will discuss the break with tradition that Richard Wagner and Adolph Appia succeeded in achieving at Bayreuth in terms of architectural acoustic design and how these changes were integrated with new approaches to scenic design and stage lighting. In addition, examples of contemporary opera companies that are creating a more intimate and emotionally powerful experience for their audiences by breaking out of the picture-frame productions of proscenium theater are given. Among these companies are the Colorado Opera and the Opera Theatre of Saint Louis.
Studying room acoustics using a monopole-dipole microphone array
Authors: Begault Durand R. , Abel Jonathan S.
Published: July 2002

The use of a sound field microphone for examining the directional nature of a room impulse response was reported recently [R. Essert, J. Acoust. Soc. Am. 100, 2837(A) (1996)]. By cross-correlating monopole and colocated dipole microphone signals aligned with left–right, up–down, and front–back axes, a sense of signal direction of arrival is revealed. The current study is concerned with the arrays ability to detect individual reflections and directions of arrival, as a function of the cross-correlation window duration. If this window is too long, weak reflections are overlooked; if too short, spurious detections result. Guidelines are presented for setting the window width according to perceptual criteria. Formulas are presented describing the accuracy with which direction of arrival can be estimated as a function of room specifics and measurement noise. The direction of arrival of early reflections is more accurately determined than that of later reflections which are quieter and more numerous. The transition from a fairly directional sound field at the beginning of the room impulse response to a unidirectional diffuse field is examined. Finally, it is shown that measurements from additional dipole orientations can significantly improve the ability to detect reflections and estimate their directions of arrival. [Work supported by NASA.]
Partially saturated transmission scintillation and the bias of the sonar equation
Authors: Makris Nicholas C.
Published: July 2002

The statistical properties of partially saturated ocean-acoustic intensity measurements are analyzed. This extends and generalizes previous analysis for completely saturated measurements [J. Acoust. Soc. Am. 100, 769–783 (1996)]. While the random component of the instantaneous field is a circular complex Gaussian random process in both saturated and partially saturated cases, a purely deterministic component is added in the latter but not the former. In both cases, the random component may contain a fluctuating signal as well as noise. The present analysis, therefore, is relevant not only to transmission scintillation but also to the general analysis of deterministic signals in additive noise. Analytic expressions are derived for the probability distributions and moments of finite-time averaged intensity and log-transformed intensity as a function of the time-bandwidth product of the measurement. From these, general formulas are obtained for the bias of the sonar equation and the standard deviation of the logarithmic measures commonly used in ocean acoustics. Asymptotic expressions are also derived for the various distributions examined and their moments.
Acoustic microscopy in pathological specimens
Authors: Halliwell Mike , Eavis Joe , Wells Peter NT , Berry Jem
Published: July 2002

The application of acoustic microscopy to biological targets is extremely limited. Devices operating at gigahertz frequencies have been proposed as replacements for conventional light microscopes with the advantage of utilizing unstained specimens. However, there remains the inconvenience of sectioning and very slow scanning speeds. Applications to unsectioned, thick specimens of unstained tissues with a view to reconstructing three-dimensional images remain uninvestigated. A 60-MHz scanning acoustic microscope was constructed with two coaxial transducers separated by about 10 mm. Linear and compound scans were performed throughout a specimen volume of about 5 mm3. Standard pulse-echo slices, velocity maps, highly compounded images, and three-dimensional representations of the specimen were produced. Water-filled airways, in fetal lung, of 40 μm diameter were visualized, and compounding was found to yield this resolution in both axial and lateral directions. Three-dimensional images demonstrated airway morphology. Acoustic scanning microscopy has been shown to be feasible in 5 mm3 soft tissue specimens. The images demonstrate pathological features in fresh unstained material. Potential for three-dimensional reconstruction of pathological morphology remains to be explored. [Work was supported by the Foundation for the Study of Infant Death.]
Ultrasonic focusing and steering through the skull: Toward brain imaging
Authors: Tanter Mickael , Thomas Jean-Louis , Fink Mathias
Published: July 2002

The time-reversal method has been experimentally applied to the focusing through the skull bone. This technique needs the knowledge of the Green’s function of a dominant scatterer available in the medium. Moreover, it is shown that the skull induces severe attenuation of ultrasound and reduces the efficiency of the time-reversal approach. Nevertheless, an improvement of time-reversal processing for ultrasonic waves focusing through an aberrating and absorbing layer can be achieved. When the attenuating layer is located close to the array, this method consists of inversing the amplitude modulation before the time-reversal operation. Conversely, when the attenuating layer is located some distance away from the transducer array, numerical backpropagation is used to discriminate between the amplitude modulations resulting, respectively, from interference and absorption. Moreover, although time reversal is only self-adaptative to the artificial source implanted inside the imaging volume, this method is generalized to steer the ultrasonic beam on other points surrounding this acoustic source. This process has already been applied to hyperthermia through the skull bone and it can be applied to noninvasive brain imaging.
The piezoelectric implant method compared to classical ultrasonic spectroscopy: Application to the monitoring of polymer curing
Authors: Raquois Agnes , Tabellout J. Mohamed , Emery Jacques , Jayet Yves
Published: July 2002

Previous studies have described an original method enabling the in situ real time monitoring of a composite polymer structure by means of an inserted piezoelectric sensor. An analytical one-dimensional model has demonstrated that the electrical impedance of such an inserted element depends in particular on the acoustical parameters of the surrounding media. Then, by solving the inverse problem by means of a nonlinear optimization algorithm, it is possible to determine these acoustical parameters characteristic of the materials in contact with the inserted piezoelectric plate. This technique has been applied to the monitoring of the cure of gel-forming and glass-forming polymers such as polyurethanes and epoxies and compared to classical ultrasonic spectroscopy method. Thus it is possible to detect chemical evolution, transitions, and damage phenomena in such systems, provided that the material is homogeneous in the ultrasonic field or in the area surrounding the piezoelectric element. Particular attention has been focused on a polyimide (PMR-15) which is used as a matrix for composites in high-temperature applications. [Work supported by SNECMA/HISPANO-SUIZA.]
A study of extracting characteristic parameters of a tubular target
Authors: Wang Renqian , Li Yingchun
Published: July 2002

An inverse problem of sound scattered by a tubular target is studied for extracting its characteristic parameters. A geometrical acoustic method is used to describe the scattered field of the tubular target. A physical model is suggested: the backscattering of a tube shell is simplified into reflection of a plane wave on layered media under conditions: ka≫1, c/c2≫h/b, here a, b, and h are outer radius, inner radius, and thickness of the tube shell, respectively, and c and c2 are sound velocity of the external medium of the tube shell and (longitudinal wave) sound velocity of the tube shell. Reconstruction formulas of the characteristic parameters of the tubular target are given. The characteristic parameters of an elastic tube shell, such as a metallic tube shell, a metallic tube covered with sound-absorbing materials, a bone tube of a pig, and soft tube shell such as a blood vessel, and a trachea of a pig, are reconstructed by using computer simulation and experiments. The theoretical results obtained by this method are supported by experiments.
An experiment on inversion of sound profile through ray modeling
Authors: Ma Yuanliang , Jiang Xiaoquan , Sheng Yuanhai , Yang Shixing , Cheng Qingzuo
Published: July 2002

An experiment was conducted in a lake of 150-m depth. A very short hydrophone array (3-m long or 1/50 of the water depth) was used for data acqisition, which consists of 13 hydrophones with 25-cm spacing. Receiving signals are modeled as sums of eigenrays determined mainly by the sound profile, while the sound profile is expressed by six measured samples at different depths in addition to a known sound speed at the bottom. The inversion is based on a simulated annealing algorithm off-line using a 486/100 microcomputer and completed within 2 min. The resultant rms error of sound profile is about 1.6 m/s in comparison with the measured data. An important feature of this approach is that instead of matching the measured to the modeled data vector, arriving structure expressed by the DOA angles and relative time delays are matched for the inversion. To estimate the arriving structure, high-resolution spectrum analysis techniques such as OWSF and MUSIC are adopted. The experiment has shown that inversion of the sound profile can be successfully achieved through ray modeling and using a very short vertical array.
Acoustical design of the medium theater of the New National Theater, Tokyo, Japan
Authors: Beranek Leo L. , Hidaka Takayuki , Masuda Sadahiro
Published: July 2002

The medium theater is mainly intended for the performances of musicals, dramas, dances, and small-size operas. It features use of two types of stage arrangement: a proscenium type with modest fan plan (1038 seats with V=7150 m3 and occupied RT=1.0 s), and an open stage type with wide fan plan (1010 seats with V=9250 m3 and occupied RT=1.3 s). The stage types are changeable from one to the other by operation of a movable floor, which is the front half of the main floor, and of slidable side walls. To cope with a wide variety of performing types, two stage types, two scenery lofts, and extensive lighting and loudspeaker requirements, minimal effective initial reflecting surfaces to enhance raw voice were studied through experiments and studies with CAD models and 10:1 scale model tests. The rear wall is a combination of a Schroeder QRD diffuser and absorbing material to eliminate echo. Satisfactory sound strength without amplification is possible only because of the short depth of the hall.
It’s all a matter of timing: Temporal mechanisms for production and encoding of acoustic signals
Authors: Bass Andrew H. , Bodnar Deana A.
Published: July 2002

Studies of acoustic communication in teleost fish have identified basic principles underlying both the motor control of acoustic signaling and the sensory encoding of the physical attributes of those signals. Parental male midshipman fish excavate denlike nests under rocky shelters in the intertidal and subtidal zones along the western coast of the United States and Canada. Nesting males generate long duration, multi-harmonic signals with a sinusoidallike appearance that are known as ‘‘hums.’’ Observations of courtship behavior together with phonotaxis experiments support the hypothesis that the hum functions as a mate call. Early studies showed that a rhythmically active, pacemaker-motoneuron circuit in the hindbrain establishes the temporal features of hums [Bass and Baker, J. Neurobiol. 21, 1155 (1990)]. Recent studies suggest that temporal coding in the auditory midbrain contributes to the segregation of, and discrimination between, concurrent acoustic signals which form acoustic beats like those generated by the overlapping hums of nesting male midshipman during the breeding season [Bodnar and Bass, J. Neurosci. 17, 7553 (1997)]. Hence, the rhythmic timing of action potentials is important for both acoustic signaling and reception. [Work supported by NIH and NSF.]
Whale voices from the deep: Temporal patterns and signal structures as adaptations for living in an acoustic medium
Authors: Clark Christopher W.
Published: July 2002

Whales produce long, rhythmic patterns of sounds and some sounds travel many hundreds of miles underwater. Species can be distinguished by temporal features, but there has been a history of infatuation with melodic qualities as the primary features of measurement. Temporal rates and time-bandwidth products are generally related to bathymetry and transmission properties, suggesting that signal features are adapted for communication and navigation. Pelagic species such as blue and fin whales rely on signals in the 10–30-Hz band, presumably to take advantage of the excellent low-frequency propagation properties of the deep ocean, with 10–200-s patterns of sound delivery. Examples will be presented illustrating the remarkable cadence of signal delivery and that animals retain a rhythm after minutes of silence. Shallow water species produce mid-frequency signals (50–1000 Hz) with temporal patterns on the order of seconds. These species with faster rhythms have greater signal variability covering a greater frequency range. At what level is this relationship between temporal pattern and spectral bandwidth indicative of adaptation to optimize for communication and navigation? Is temporal pattern a retained, conservative feature and spectral variability more of an embellishment by individuals to adjust to local conditions?
Ground-borne vibration measurements of high-speed trains
Authors: Towers David A. , Saurenman Hugh J.
Published: July 2002

Ground-borne vibration measurements of high-speed train operations were carried out in France for the TGV and Eurostar trains, in Italy for the Pendolino trains, and in Sweden for the X2000 trains. The measurements were made to develop vibration-prediction models for a new guidance manual published by the U.S. Federal Railroad Administration on ‘‘High Speed Ground Transportation Noise and Vibration Impact Assessment.’’ The tests included measurements of ground-borne vibration at various distances from the track as well as a procedure to characterize the ground vibration propagation characteristics at each measurement site. The results indicated a wide spread in the vibration data, partly due to differences in the equipment and track condition and partly due to differences in site geology. Further analysis suggested that much of the difference between the trainsets is due to variations in the geology rather than differences in suspension, axle load, or wheel conditions of the trainsets. Applying the characteristics of one type of trainset to different test sites resulted in widely varying ground vibration levels and propagation rates, whereas normalizing the ground vibration from the trainsets to one site substantially reduced the differences in overall vibration level.
Multivariate analysis of road traffic noise in Gandia (Spain) during 24 hours and its evolution in the last decades
Authors: Romero Jose , Jiminez Alicia , Sanchis Antonio , Marin Albert , Garcia Amando , Zurita Grover
Published: July 2002

Road traffic noise is one of the most widespread and growing problems in urban areas. While it has long been known that hearing can be damaged by exposure to noise, it is also believed that continual noise, even at low or moderate intensity, can cause psychological discomfort and sleep disorders. Traffic noise levels in urban areas are increasing, and the areas affected by noise are spreading. As a result of these problems, legislation has been introduced by the city council to control the noise produced by individual vehicles with the aim of eventually producing traffic noise levels which are acceptable to the public. In this paper, therefore, aspects which connect the evolution of the road traffic noise in the last decades and the development of the infrastructure of the city are discussed. The study was carried out in Gandia (Spain), which is situated on the East Coast of the country, 65 kms from Valencia and 100 kms from Benidorn. The population has increased from 50 000 to 60 000 in the last 15 years, and the traffic distribution of the city has changed during this time, with a new bridge and some highways around the urban area. The main objective of this paper is to characterize the effects of the road traffic noise during 24 h (between 1983 and 1997), and including such aspects as traffic density and psychological aspects. The analysis part was performed by using multivariate analysis methods (MVA). Multivariate analysis methods can be used to investigate relationships between all the variables by extracting information from data with many variables and treating them simultaneously.
Adaptive control of sound transmission with neural network algorithms
Authors: Tian Jing , Lin Hai , Cheng Mingkun
Published: July 2002

The Artificial Neural Network is widely used for its self-learning, self-organizing adaptability as well as nonlinearity in nature. Active control of structural sound radiation and sound transmission through panels is widely researched recently for its effectiveness and efficiency in the low-frequency range. In this paper, a neural network-based feedforward adaptive controller using the modified Error Back Propagation Learning Algorithm is presented. The controller is realized with a TMS320C25 DSP Board monitored by an IBM PC compatible, and applied to control the sound transmission through a thin panel between two rooms. Experiments showed that the algorithm was superior in robustness and broadband performance. In the adaptive controller, the structure of a traditional multi-layered feedforward neural network (MFNN) is modified. Both filtered-X and filtered-U adaptive filters are discussed. Two auxiliary filters are designed to compensate the secondary signal feedback and the error delay. Random gradient estimation method is used to update the weights of MFNN. Several methods to speed the learning rate are also introduced. The causality of the feedforward controller is analyzed, by which the system behavior is greatly improved. Further strategy to improve the controller is also proposed. [Project supported by the Natural Science Fund of China.]
Macrotimbre: Contribution of attack, steady state, and verbal attributes
Authors: Sandell Gregory J.
Published: July 2002

The timbre attributes of a source that are contained across variations in pitch, dynamic, and articulation can be referred to as its ‘‘macrotimbre.’’ The timbre of a musical instrument changes across pitch, and thus learning its macrotimbre can be dependent upon the ability to make comparisons among individual pitches. Using 20 pitches shared by two easily confused instruments (C4 to G5, oboe and English horn), listeners performed better at categorizing novel notes (from a pitch range different from those heard in training) when training facilitated comparison of notes (versus isolated presentations) [Sandell and Chronopoulos, Proc. Third ESCOM Conf., Uppsala, Sweden, 222–227 (1997)]. This indicated that information contained across pitches was useful in generalizing timbre knowledge to previously unheard notes. The present study used (1) multiple versions of the tones (natural, shortened, attack + synthetic steady-state, synthetic steady-state alone), (2) a sorting task under conditions where comparisons were facilitated or hindered, and (3) ratings of verbal attributes (nasal, breathy, muffled, etc.) to isolate the relevant across-pitch timbre properties, and appraise the relative contributions of the attack and steady state.
A measurement of sound power lever of noise source—Vibration velocity method
Authors: Yang Weicheng , Qiao Wuzhi
Published: July 2002

Sometimes it is necessary to measure on-line the noise of some products, such as the household electrical appliances and their parts (motors, compressors, and contacts). Nowadays, several measurements (sound intensity measurement and vibration flow measurement) have been applied, but are not good enough. In this paper, another on-line measurement of sound power lever of noise source vibration, velocity measurement, is proposed. This measurement has two advantages, viz., without the influence of the surrounding area and with less measuring time. After the theoretical analysis and the experiment to the small-type compressor of the refrigerator in a semi-anechoic chamber, the sound-radiating efficiency curve is attained. Based on the vibration velocity measurement, the sound power lever of the compressor is predicated through this curve. The error of the predicated result is less than 2 dB, compared with that of the standard ISO 3745.
Cavitation terminology
Authors: Nyborg Wesley L.
Published: July 2002

Among the important contributions Flynn made to the subject of acoustic cavitation was his introduction of concepts and language which have greatly helped our thinking and our communications. In 1964, he defined two acceleration functions and used them for classifying the behavior of gas-filled cavities in a sound field. The more violent kind of behavior, involving ‘‘collapse,’’ occurs when one of the functions, the inertial function, dominates at a critical time during cavity contraction. This type of cavitation was initially called ‘‘transient,’’ partly because the collapse events are of short duration, and partly because the cavities themselves are often short-lived, disappearing through fragmentation and dissolution after collapse events. The other class of cavitation is called ‘‘stable,’’ and represented oscillatory motion which might be complicated but which persists indefinitely. This classification has become very helpful in discussing cavitation phenomena and is widely used in the literature. In recent years, however, the term ‘‘inertial’’ has come into use, replacing ‘‘transient,’’ for cavitation in which Flynn’s inertial function dominates. Examples will be discussed in which Flynn’s classification is applied to experimental situations.
Influence of nonradial experimental conditions on the acoustic scattering behavior of a single cavitation bubble
Authors: Niederdraenk Torsten
Published: July 2002

The dynamic behavior of a single cavitation bubble in a sound field can be evaluated using the acoustic scattering technique. A high-frequency image sound is scattered by the bubble, which pulsates in the primary driving sound field. The scattered sound contains information about the bubble oscillation. The shape of the bubble radius can be observed by evaluating the amplitudes of the scattered sound or by determination of frequency shifts caused by the motion of the bubble wall. If the wavelength of the high-frequency image sound and the bubble size are of the same order, or if the boundary and excitation conditions in the experimental setup do not fulfill the demand of a spatially independent primary driving field, the bubble is exposed to nonradial driving conditions. Modes of bubble oscillation may develop that can be decomposed into spherical harmonic components of different order. These modes affect the acoustic scattering behavior, because sound emissions of the nonradial contributions of bubble oscillation are characterized by different directivities. Moreover, the amplitudes of sound emitted by higher-order spherical harmonics depend more strongly on the receivers’ distance to the bubble.
Absorbing boundary conditions for acoustic waves and Huygens principle
Authors: Mangiante Gérard , Charles Sylvestre
Published: July 2002

When numerically simulating acoustic wave propagation, artificial boundaries must be introduced into the model to limit the area of computation. To eliminate the spurious reflections produced by these artificial boundaries, absorbing boundary conditions are needed. Such boundary conditions are usually approximated according to two main strategies: paraxial wave equation and the use of viscous media. This paper describes a new approach of the boundary conditions problem using Jessel’s formulation of Huygens principle [Jessel (1991), Mangiante (1994), Charles (1996)]. A suitable distribution of Huygens secondary sources was arranged in a transition zone surrounding the model, and adjusted to produce destructive interference to cancel the wave field outside this transition zone. Perfect absorption can be theoretically obtained and can be numerically illustrated. However, due to practical difficulties, only an approximation of this solution has been derived for a finite difference scheme. This approximation consists in splitting the history of the wave field within user defined time windows. The main difficulties are related either to the space and time behavior of the Green functions, or to the solution of the wave equation problem via a finite difference scheme.
The role of the auditory periphery in the categorization of stop consonants
Authors: Damper Robert I.
Published: July 2002

A proper understanding of speech perception requires an understanding of the staged restructuring of information that occurs as an acoustic stimulus is transformed by the auditory system into a phonetic percept. It is now firmly established that a physiologically faithful computer simulation of peripheral processing feeding into a trainable artificial neural network (ANN) is capable of reproducing the important aspects of the categorization of initial stop consonants into voiced and unvoiced classes. Correct behavior is found to be insensitive to the ANN architecture and a precise training scheme used, suggesting that such categorization is very basic to the repertoire of auditory processing strategies. Unlike a human or animal listener, a computational model can be easily manipulated and interrogated to discover the underlying basis of category formation. In particular, the physiological-based simulation of the auditory periphery can be dramatically simplified and the effect on categorization observed. It is found that proper modeling of frequency scaling and neural adaptation are essential to correct simulation of the well-known shift of phoneme boundary with place of articulation for stop consonants. The role of the auditory periphery in this case seems to be to emphasize the region of first formant information around the time of voicing onset.
A mathematical model of consonant perception by cochlear implant users with the SPEAK strategy
Authors: Svirsky Mario A. , Meyer Ted A.
Published: July 2002

The traditional approach to determine which psychophysical variables are important for speech perception by cochlear implant (CI) users has been to perform correlational analyses. However, the finding of a statistically significant correlation between psychophysical and speech perception variables does not explain the actual mechanisms CI users employ to identify speech sounds. A mathematical modeling approach is proposed that does provide a detailed description of how CI users identify speech sounds based on the acoustic information they receive. To use the proposed approach, it must be hypothesized what the relevant psychophysical dimensions are for a given stimulation strategy. In this study, it is hypothesized that users of the SPEAK stimulation strategy use three types of cues to identify consonants: first, the average cochlear locations stimulated in response to the first three formants; second, the silent gap duration (if present); and third, the ratio between total energy above and below 1000 Hz. Based on a subject’s performance along these psychophysical dimensions, the model outputs a predicted consonant confusion matrix. Preliminary comparisons between model predictions and actual data indicate that the model was able to predict which pairs of consonant sounds would be most frequently confused by CI users. [Work supported by NIH.]
Perception of speech gestures
Authors: Carré René , Divenyi Pierre L.
Published: July 2002

Perception of a synthetic French /aya/ sequence, generated by coproduction of two simultaneous gestures (tongue constriction and lip rounding), was tested in a series of experiments. The tokens consisted of eight different degrees of gesture reduction in which the target /y/ was not reached. The /ay/ trajectory in the plane F1–F2 was not rectilinear (it pointed first to /i/ before reaching /y/), having to do with the fact that the acoustic effect caused by lip rounding (lowering F2) becomes manifest later than the effect due to constriction (lowering F1 and raising F2). The /aya/ transition is, therefore, an appropriate stimulus to study the role of the linearity of trajectories in speech perception. Results show that unless /y/ is present as a steady-state vowel for at least 30 ms, the lip rounding gesture is ignored and the percept is /aia/. Thus the results strongly suggest that formant trajectories are perceived as time averages through a mechanism that calculates the direction of transition toward an (unreached) tar-get from a running average of the direction of the formant trajectory. These findings point to the importance of the trajectory direction in vowel reduction and of the time dimension in phonetic distinctions. [Work supported by NATO.]
A model for dependences in phonetic categorization
Authors: Smits Roel
Published: July 2002

A quantitative model for human categorization behavior is proposed which can be applied to four-alternative forced-choice categorization data involving two binary classifications. A number of processing dependences between the two classifications are explicitly formulated, such as the dependence of the location, orientation, and steepness of the class boundary for one classification on the outcome of the other classification. The significance of various types of dependences can be tested statistically. Analyses of two data sets from the literature [Repp et al., J. Exp. Psych: Human Percept. Perform. 4, 621–637 (1978); Whalen, Percept. Psychophys. 46, 284–292 (1989)] show that interesting dependences in human speech recognition can be uncovered using the model.
Surveying auditory space using vowel formant data
Authors: Makashay Matthew J. , Johnson Keith
Published: July 2002

Recent research has suggested that vowel category learning and the perceptual magnet effect are the natural consequences of auditory neural map formation [F. H. Guenther and M. N. Gjaja, J. Acoust. Soc. Am. 100, 1111–1121 (1996)]. As these effects are language specific, the organization of the perceptual map crucially is dependent on the input received during learning. Guenther and Gjaja implemented a working model of a self-organizing neural map to show that, given input from Gaussian distributions around vowel category centers, unsupervised training leads to a warping of the perceptual space toward the category centers. This work replicates Guenther and Gjaja’s results and provides a more realistic test of the model by using real vowel formant data instead of idealized distributions. Single and multiple male talker vowel data were used to train auditory neural maps. Single-talker simulations resulted in map organization similar to Guenther and Gjaja’s results. However, no clear vowel category clusters emerged in the multiple-talker simulations. [Work supported by NSF Graduate Fellowship and NIH FIRST Award R29-DC01645-06.]
Modeling the perception of features in the identification of English consonants
Authors: Doeleman Tobey L.
Published: July 2002

The perception of voicing, place, and manner was investigated in a series of gating experiments in which subjects identified eight English consonants in six different duration conditions [T. L. Doeleman, J. Acoust. Soc. Am. 101, 3111(A) (1997)]. Subjects heard either all eight stimuli or two mutually exclusive subsets such that certain feature information was given (e.g., manner given in sets [p, t, b, d] and [f, s, v, z]). Although all subjects listened to the same 48 stimuli, identification significantly improved for subjects given place information (i.e., sets of labials and alveolars). The results are modeled using a spreading-activation connectionist model, the Integration-Competition model [Spivey-Knowlton (1996)]. In this model, the phoneme and feature representations compete with one another such that featural distinctions correspond to different weights assigned to the connection between feature and phoneme layers. The target phoneme has high activation from all featural arrays, resulting in the highest activation in the phoneme array. The increase in identification scores across duration conditions is modeled by the increase in activation of the target phoneme with successive time steps. The model also predicts observed consonant confusion patterns in that distracter phonemes sharing more features with the target phoneme will have higher activation levels.
Noninvasive assessment of shear rate (WSR) in humans by means of ultrasound
Authors: Reneman R. S. , Kornet L. , Samijo S. K. , Brands P. J. , Hoeks A. P. G.
Published: July 2002

An ultrasound technique to assess velocity and shear distribution in arteries noninvasively was developed . Accurate assessment of velocities close to the wall, a prerequisite for reliable determination of WSR, is achieved by tracking of the arterial wall and adaptive filtering of the wall signal. Velocity (v) distribution in the vessel is obtained by RF cross correlation of the signals in between the walls, and determination of dv/dr throughout the cardiac cycle provides shear distribution. Maximum dv/dr near the wall is taken as peak WSR and average shear over the cardiac cycle as mean WSR. Wall shear stress (WSS) is estimated by multiplying WSR by whole blood viscosity. The system also allows assessment of arterial diameter, diameter changes, and intima-media thickness (IMT). In studies on humans it could be shown that at a younger age in the common carotid artery (CCA) MWSS is close to 1.5 Pa, a value in agreement with minimal expenditure of energy. MWSS, however, is not optimally regulated, because it decreases with age. In the CCA, WSR close to the bifurcations were lower than and associated with larger IMT than more upstream. Reflections from downstream are held responsible for these differences in WSR.