bluuebunny/crossref_metadata_2025 huggingface dataset:
Rudimentary statistical energy analysis and structural fuzzies
Authors: Maidanik G. , Dickey J.
Published: July 2002

Structural fuzzies (Sfs) is a dynamic complex that is attached to a primary structure in order to provide a higher degree of dissipation. The dissipation is with respect to the power that is injected into the driven primary structure. It is argued that care needs to be exercised in the definition of the loss factor that is associated with this dissipation. This definition is examined and discussed; then, the role of the Sfs is analyzed in terms of a rudimentary statistical energy analysis (SEA). It is shown that the effectiveness of the dissipation is enhanced if the coupling of the Sfs to the primary structure is strong enough to approximate equipartitioning of modal energies, if the modal density in the Sfs either approximates or exceeds that in the primary structure and, finally, if the inherent loss factor in the Sfs is sufficiently higher than that in the primary structure. The definitions of strong enough coupling, modal densities, and inherent loss factors will be given. Examples of Sfs will be cited and discussed.
The effect of vowel prototypicality and extremity on discrimination sensitivity
Authors: Nakai Satsuki
Published: July 2002

The present study examines the effect of vowel extremity and prototypicality on discrimination sensitivity. Kuhl [1991] has shown that listeners are not as capable of distinguishing other variations of /i/ from a prototypical /i/ (the stimulus with the highest goodness rating, henceforth P) as from a nonprototypical /i/ (a stimulus with a low goodness rating). However, considering evidence suggesting that discrimination sensitivity grows poorer towards the exterior of the vowel space [Schouten and van Hessen, 1992], it is unclear whether it is vowel prototypicality or extremity that correlates with low discrimination sensitivity, for P is the most extreme among the stimuli used in the discrimination task in Kuhl [1991]. In order to investigate the above issue, discrimination curves were obtained from native speakers of Japanese and Greek in the corner of the vowel space where Japanese /u/ and Greek /u/ are located. As Japanese /u/ is not cardinal, the effect of vowel prototypicality and extremity on discrimination sensitivity could be observed separately on Japanese subjects’ discrimination curves. The results indicate that both vowel prototypicality and extremity contribute to low discrimination sensitivity, and that the extremity of P correlates with the magnitude of its effect on discrimination sensitivity.
Ray tracing in a turbulent, shallow-water channel
Authors: Bjerrum-Niese Christian , Lützen René , Bjo/rno/ Leif
Published: July 2002

A ray tracing model can be used to simulate sound (10–100 kHz) transmitted through shallow water. The phase of the ray arrivals, primarily given by travel time, may be mutually independent in such a multipath transmission. Consequently, the transmission loss in a receiving point is randomly valued due to the coherent interference of the multipath arrivals. This problem can be overcome by incoherent summation of the multipath arrivals. However, knowing that nature behaves coherently, this method is not preferred. Instead, the channel can be regarded as dynamic by allowing microfluctuations of the sound speed. Specifically, the channel may be modeled as given by horizontal layers, each assigned with an individual turbulent dissipation rate, and a translation of this is performed into diffraction and phase fluctuation parameters, following DiIorio and Farmer [J. Acoust. Soc. Am. 96, 1056–1069 (1994) and Flatté et al., Sound transmission through a fluctuating ocean (1979)]. Amplitude and phase fluctuations of every ray are realized as samples of a random process. The results for the dynamic channel show a smoother and easier interpretable transmission loss behavior than for the static channel. Furthermore, it is observed that amplitude fluctuations generally exhibit Ricean fading. [Work sponsored by the Danish Technical Research Council.]
Towards new UK underwater acoustical measurement standards in the 21st century
Authors: Preston Roy C. , Robinson Stephen R.
Published: July 2002

The importance of establishing common measurement standards to support underwater acoustical calibration and testing in the UK, and therefore the need to demonstrate calibration traceability, has progressively grown over the last few years. In the UK, the National Measurement System provides the means of achieving traceability through the establishment and dissemination of primary standards of measurement. This paper will outline the progress made so far in establishing the UK’s underwater acoustical measurement standards, and look forward to plans to extend the capability to cover the whole frequency range of interest, over the ranges of temperature and hydrostatic pressure applicable to simulated ocean conditions. The validation of these measurement standards will also be discussed.
Acoustic projector calibration in reverberant environments: A survey of USRD measurement technology
Authors: Forsythe S. E. , Ainsleigh P. L.
Published: July 2002

The use of pressure- and temperature-controlled tanks for calibration of Navy projectors is a cost-effective alternative to open-water or at-sea measurements. The Underwater Sound Reference Division (USRD) of the Naval Undersea Warfare Center maintains a large closed tank which is temperature and pressure controlled. This tank, like all closed vessels, suffers from a major drawback: it is highly reverberant, especially at low-frequency operation, which precludes the possibility of making steady-state projector response measurements (especially for highly resonant projectors with low-frequency resonances) as would be possible in a large body of open water. This presentation surveys the techniques developed at USRD to ensure that measurements made in the tank are traceable to those that would be made for the same projector in open water. Three broad categories of approaches will be presented: (1) estimating the steady-state response using a model that represents only the pre-echo portion of the received data (transient modeling), (2) estimating the echo-free steady state using a multiple-arrival model that accounts for echoes in the received data (multipath modeling), and (3) characterizing the wave field using multiple hydrophones to separate the direct wave field from the wave field due to echoes (spatial processing). [Work supported by ONR.]
Test chamber for determining damage thresholds for high-amplitude underwater sound exposure in animal models
Authors: Lewis Thomas N. , Rogers Peter H. , Martin James S. , McCall George S. , Lloyd Joey G. , Cotten Henry P. , Caille Gary W.
Published: July 2002

In order to determine the effects of low-frequency underwater sound on small animal models it is desirable to expose them to well-characterized fields which closely simulate the (locally) plane-wave open ocean stimulus. It is also desirable to produce pure pressure and acceleration stimuli to isolate the effects of the individual components of the acoustic plane wave. It is necessary to produce sufficiently strong signals to enable damage thresholds to be determined. The range of frequencies over which such stimuli must be produced is quite broad since it must include the actual band of interest (100–500 Hz) to examine damage on a cellular and tissue level, as well as at scaled frequencies (∼1–5 kHz) to examine the effects of organ structure. The problem is subtler than one might imagine because of the high compliance of the test animals due to the air in their lungs. The lungs will drastically alter the acoustic field in the chamber and change the loading on the sources and the chamber could alter the vibrational response of the lung. Careful consideration is required to ascertain what is required of the chamber to assure valid measurements and to determine the true effective sound pressure level.
Three-dimensional propagation modeling in shallow water
Authors: Orris Gregory J. , Perkins John S.
Published: July 2002

Much interest exists in problems of shallow-water propagation, where three-dimensional spatially dependent waveguide effects are sometimes very large. In these cases the three-dimensional dependence of the acoustic field can be accounted for in a variety of ways other than solving the often intractable fully coupled problem. There exist several pseudo three-dimensional models that are based on the parabolic equation method (e.g., N×2D PE [J. S. Perkins and R. N. Bear, J. Acoust. Soc. Am. 72, 515–522 (1982)], the adiabatic PE [M. D. Collins, J. Acoust. Soc. Am. 93, 2269–2278 (1993)], the coupled-mode PE [A. T. Abawi et al., J. Acoust. Soc. Am. 102, 233–238 (1997)] and the spectral PE [G. J. Orris and M. D. Collins, J. Acoust. Soc. Am. 96, 3499–3503 (1994)]). Yet, because these models are extensions of efficient two-dimensional models they have explicit and implicit limitations on their applicability. Some of the advantages and limitations of these pseudo three-dimensional models will be demonstrated through their application to data collected during the SWellEx-96 and RDS-1 matched-field experiments.
Wave number extraction techniques for a three- dimensionally varying shallow-water waveguide: A comparison
Authors: Becker Kyle M. , Frisk George V.
Published: July 2002

Theory shows that the wave number spectrum of a propagating normal mode field is a function of position for a complex, shallow-water waveguide whose acoustic properties vary in three spatial dimensions. By describing the spatially varying content of the modal field, a direct measure of the propagation characteristics of the waveguide can be made. Consequently, to obtain greater sensitivity of the spectrum as a function of position, it is of interest to resolve the contributions from individual modes using as short a data record as possible. To this end, several wave number extraction methods have been applied to synthetic data, as well as real data measured using a synthetic aperture planar array created by several freely drifting buoys. Wave number content as a function of position was extracted using Hankel transforms, best linear estimator techniques, and autoregressive algorithms. Results obtained for frequencies in the range 50–300 Hz are compared for resolution and consistency using data records of various lengths. Based on these results, recommendations are made for the selection of an appropriate extraction algorithm. [Work supported by ONR.]
Acoustics of two-phase fluids and sonoluminescence
Authors: Nigmatulin Robert I.
Published: July 2002

The basic equations for dynamics of two-phase mixtures like gas–particle suspensions and bubbly liquids are presented. Heat and mass exchange phenomena near a drop, particle, and gas or vapor bubble are discussed. It is shown that these phenomena play an important role in propagation, attenuation, and amplification of sound waves and shock waves in gas–liquid systems, sometimes leading to paradoxical effects. The dynamics of a sonoluminescing bubble is discussed. There are two stages of the bubble oscillation process: The low Mach number stage when the velocity of the bubble interface is small compared with sound speed in the liquid, and the stage corresponding to the collapsing bubble’s compression, when the velocity of the interface may be larger than the sound speed. The analytic solution for the low Mach stage is presented. This solution provides the economical boundary condition around the bubble for an effective numerical code.
The necessity for acoustics in the biomedical engineering program
Authors: Raichel Daniel R. , Jiji Latif
Published: July 2002

Biomedical engineering constitutes the fastest growing segment of all engineering fields. In order to effectively deal with a wide variety of engineering problems, the biomedical engineer needs to be a ‘‘jack of all trades’’ insofar that he or she should be able to meet challenging problems in mechanics, electronics, thermal analyses, fluid mechanics, materials, manufacturing techniques, etc. In the medical field, acoustics (particularly ultrasound) is used for both diagnostic and therapeutic purposes, and new devices are continuously being developed to provide better diagnostic imaging or more effective therapy. As a part of the biomedical engineering program, undergraduate and graduate students need to gain better understanding of acoustical physics, the effects of sound and ultrasound on living organisms, the principles of measurements, imaging processes, and data analysis concepts. Laboratory experience is essential, and practical experience in a teaching medical hospital would definitely be salutary. The time constraint imposed by a four-year undergraduate program, which also needs to meet ABET criteria, effectively limits the expository scope, and it follows that additional, more intensive training may be better achieved through post-baccalaureate (master’s degree and doctoral levels) programs.
Substructuring in the finite-element analysis of sonar transducer arrays
Authors: Dunn J. R. , Chen C-L. , Smith B. V.
Published: July 2002

Finite-element (FE) analysis of arrays of sonar transducers becomes costly in memory and computation time for arrays with many elements. This becomes even more severe a problem if the individual transducers have complex structures. However, because in many cases the individual transducer elements are identical, it is possible to treat them as repeated substructures; each substructure may then be viewed as a superelement which is defined by only those nodes which couple into the overall structure of the array. This technique is analogous to the use of Thevenin equivalent sources in the analysis of complex electrical circuits. By the use of this technique it is possible to analyze the electroacoustic performance of larger arrays than hitherto possible within the limitations set by the computer memory. This paper describes this superelement technique and results are presented for a simple two-element transducer array analyzed for its free (unloaded) vibration behavior both by full FE analysis of the complete structure and by the substructuring technique. The results of the two methods are shown to agree very closely, and measurements on an experimental model compare favorably with the theoretical predictions.
Prediction and reduction of centrifugal blower noises
Authors: Banks Christopher L. , Wu Sean F.
Published: July 2002

This paper presents the results of an investigation of centrifugal blower noises. Experiments on three different types of blowers were conducted to determine the major noise generation mechanisms. The information thus gained has led to an innovative noise reduction method utilizing a stationary, noncontacting transition mesh. Experiments showed that an overall noise reduction of 3 to 5 dB was achieved for all the blowers running at impeller speeds in the range of 10 to 30 m/s. In addition, a semianalytical model was developed to predict noise spectra from dimensionally similar centrifugal blowers. This model yielded an acoustic power proportional to the fourth power of the blower speeds. Comparisons of the calculated and measured noise spectra from different blowers running under various speeds were demonstrated. Good agreements were obtained in all cases. [Work supported by Ford Motor Company.]
Survey on the actual condition of the sound environment in commercial spaces
Authors: So Michiko , Kimura Sho
Published: July 2002

Many people use a great variety of commercial spaces in their daily life, and are exposed to such a peculiar sound environment both consciously and unconsciously. In order to gain a comprehension of the user’s awareness of the sound environment in commercial spaces, a survey was conducted on residents of the Tokyo Metropolitan Area (1198 effective responses were received). The result shows a great majority of those questioned regard the sound environment as one of the features that enhance the atmosphere or the character of commercial spaces. Accordingly, the design of the sound environment plays a role as one of the important factors in creating the atmosphere of individual commercial spaces. On the other hand, it was also revealed that under current conditions, the loudness, articulation, quality, the manner of presentation of background music and announcements, etc. (especially how to use PA systems in noisy surroundings), in individual commercial spaces were not adequately adjusted or designed in many cases. This is associated with the limits of preference and the potential question of the awareness of the users.
Abrupt drive pressure variations for probing the extinction threshold mechanism for single-bubble sonoluminescence
Authors: Matula Thomas J. , Crum Lawrence A.
Published: July 2002

A novel method utilizing abrupt drive pressure amplitude changes has been used to probe transient conditions in single-bubble sonoluminescence (SBSL). This technique has been used to probe the incipient luminescence threshold [Matula and Crum, Phys. Rev. Lett. (submitted)], where it was found that sonoluminescence from air bubbles depend on the time the bubbles spend in the sonoluminescing state. The abrupt pressure change technique has also recently been used to probe SBSL behavior near the extinction threshold. Simultaneous measurements of the radial response and light emission may be used to better understand the mechanism for SBSL extinction.
Loudness of dynamic stimuli in cochlear-impaired listeners
Authors: Zhang Chaoying , Zeng Fan-Gang
Published: July 2002

In normal hearing listeners, a temporally fluctuating sound with modulating frequencies from 4 to 400 Hz was found to be louder than predicted by its averaged power. The louder sensation due to temporal fluctuation was also found to be overall level-dependent: approaching peak amplitude loudness at a comfortably loud level, becoming less at lower sensation levels, and disappearing at higher levels. If this level-dependent loudness effect were related to the nonlinear cochlear compression, then it would disappear in cochlear-impaired listeners because their nonlinear compression is presumably damaged. Three listeners with clinically diagnosed cochlear impairment balanced loudness between white noise and sinusoidally amplitude-modulated noise. The results showed that the modulated noise was louder for modulating frequencies between 4 and 400 Hz at all three sensation levels, consistent with the hypothesis that the overall level effect on loudness of dynamic stimuli is related to the cochlear compression. These results indicate that loudness of dynamic stimuli is governed by two different mechanisms: a retrocochlear temporal processing mechanism which is presumably preserved in both normal and cochlear-impaired listeners, and a cochlear mechanism which provides amplitude compression at high levels in normal listeners and is damaged in the cochlear-impaired listeners. [Work supported by NIDCD.]
A metric for determining the degree of compression of a processed signal
Authors: Schmidt Jon C. , Rutledge Janet C.
Published: July 2002

When attempting to compare different compression algorithms or different parameter settings of a given compression algorithm, there is a need to compare equivalent amounts of compression. Listening tests that have varied only one parameter while fixing the others have obtained the expected results that increasing the amount of compression that occurs creates a more audible difference between the compressed version and the original. Since there are several parameters that influence the actual amount of compression that occurs, it is desirable to know which set of parameters will create to the least perceptual difference from the original signal for a given amount of compression. Unfortunately, there is not a well-defined approach for determining the amount of compression that has been imparted to a signal. The peak/RMS ratio is woefully inadequate for many compression contexts. Two degree of compression metrics are proposed that can be used to determine the amount of compression by direct analysis of the audio signal before and after compression. These metrics give excellent results in predicting the ratings of subject-based testing on the audio quality of several different audio segments across several parameter variations. a)Currently with ReSound. b)Currently with the University of Maryland Medical Center.
Modeling tactile speech perception with auditory simulations
Authors: Lash Albert T. , Weisenberger Janet M. , Xu Ying
Published: July 2002

A useful technique for gaining insights into the perception of speech stimuli presented via vibrotactile aids is to model this perception by presenting degraded auditory stimuli to normal-hearing observers. It is likely that spectral, temporal, and intensive properties of the tactile system could all affect tactile speech perception. In the present experiments, tactile perceptual data were collected for a set of nonsense syllables presented via a vibrotactile vocoder to normal-hearing subjects. The same subjects were tested with sets of degraded auditory stimuli that were modified by reducing spectral, temporal, or intensive parameters. Spectral reductions alone, achieved by reducing the number of filter channels and broadening filter bandwidths, did not appreciably affect auditory performance, nor did intensity reductions, achieved by reducing dynamic range and intensity quantization. Although temporal reductions, achieved by low-pass filtering the stimuli, did result in lower perceptual scores, the pattern of stimulus confusions did not correlate highly with the tactile data. Pairwise and three-way combinations of spectral, temporal, and intensive parameters yielded more promising correlations. Implications for constructing a comprehensive model of vibrotactile speech perception are discussed. [Work supported by NIH.]
The effects of dexamethasone following an acute acoustic trauma
Authors: Ahroon William A. , Johnson Ann R. , Hagar B. Sheldon , Hamernik Roger P.
Published: July 2002

An acute acoustic trauma (AAT) results when the unprotected ear is exposed to very high sound pressure levels, usually as the result of an industrial or military accident. There is no commonly accepted treatment in the U.S. for an AAT. A study was performed to evaluate the effects of a corticoid steroid (dexamethasone) on the hearing loss from a series of blast waves that would simulate an AAT. Dexamethasone is commonly used as an anti-inflammatory agent in veterinary medicine. Groups of chinchillas were exposed individually to ten 160-dB peak SPL reverberant blast waves from a conventional shock tube at a rate of one blast per minute. Immediately following the exposure, the animals were injected with dexamethasone alone (1.0–2.0 mg/kg IV) or in combination with dimethyl sulfoxide (DMSO), a free-radical scavenger. Individual groups of animals showed the well-known extreme variability in hearing losses as noted in earlier studies [e.g., R. P. Hamernik et al., J. Acoust. Soc. Am. 90, 197–204 (1991)]. Examining the median permanent threshold shifts (PTS) of the groups of animals showed a distinct dose-response effect with increasing dosages of dexamethasone associated with lower levels of PTS in the frequency region most affected by the noise exposure.
Simulation of sentence-level speech based on measured vocal tract area functions
Authors: Story Brad , Titze Ingo , Long Russel
Published: July 2002

An inventory of vocal tract area functions, acquired from magnetic resonance imaging experiments, is used as the basis for creating simulations of sentence-level speech. A first approach is a ‘‘brute-force’’ method in which a phonetic transcription of a sentence is time aligned with the recorded acoustic signal. Each element of the transcription is assigned one of the stored vocal tract area functions in the acquired inventory, thus serving as a ‘‘target’’ through which the time-varying area function should pass. This method has produced intelligible speech but maintains a machinelike quality. A second approach uses a parametric representation of the MRI-acquired area function inventory based on a principal components analysis to generate area functions not in the original inventory. The first three formants of each generated area function were computed and stored in a database, thus creating a mapping between formant frequencies and vocal tract parameters (area functions). Except for the edge of the formant space, the mapping between formants and area functions is one-to-one. This method produces connected speech with natural sounding vowels when only a microphone signal is used but requires additional signals to derive the consonantal contribution to the vocal tract shape. [Supported by NIH grant RO1 DC02532.]
Contrasting chest and falsettolike vibration patterns of the vocal folds
Authors: Berry David A. , Montequin Douglas W.
Published: July 2002

Using excised larynges, a hemilarynx methodology was used in order to view vocal fold vibrations from a medial aspect. This was accomplished by removing one fold, inserting a glass plate at the glottal midline, and mounting the remaining fold against the glass plate. A stereoscopic imaging system was used to perform 3D tracking of small markers (microsutures) placed on the folds. Chest and falsettolike vibrations patterns were imaged and quantified. These two vibrations patterns will be contrasted with each other, and discussed in terms of previous qualitative comparisons of these phonation types in the literature. [Work supported by Grant No. R29 DC03072 from the National Institute on Deafness and Other Communication Disorders.]
Perception of coarticulated vowels by prelingual infants: Formant transitions specify vowel identity
Authors: Bohn Ocke-Schwen , Polka Linda
Published: July 2002

German-learning infants were tested for discrimination of four German vowel contrasts in the Silent Center paradigm to examine which acoustic properties of coarticulated vowels (target-spectral, dynamic-spectral) define vowel identity in prelingual infants. Acoustic analyses of naturally produced original syllables (/dVt/ with V=/i, e, I, E, o, U/) revealed no vowel inherent spectral change but only formant movement associated with the gestures for the initial and final consonants. The original syllables were electronically modified to obtain test syllables which contained target-spectral information (the vowel nucleus only), only initial or only final formant transitions, or initial and final transitions in their appropriate temporal relationship, with the vowel nucleus attenuated to silence. Four groups of ten infants each (aged 7–11 months) were tested in the conditioned headturn procedure for discrimination of the test syllables. Each group was tested on one of four contrasts (/i/–/e/, /e/–/I/, /E/–/I/, /o/–/U/) after they had discriminated that contrast successfully in the unmodified condition. Results indicate that target spectral information is not needed to discriminate native contrasts; rather, dynamic spectral information spread over syllable onsets and offsets is sufficient to specify vowel identity in infants. [Work supported by grants of the Deutsche Forschungsgemeinschaft to O.-S. Bohn.]
Some observations of the tense–lax distinction theory with reference to English and Korean
Authors: Kim Dae W.
Published: July 2002

A series of experiments with 13 subjects in total and with /VCV/, /CVC/, /CVCVCV/, and /CVCVC/ words, using various techniques, was undertaken to verify the hypothesis that the speaker may select at least one of muscles involved in the articulation of a phoneme so that either timing or amplitude variable and/or both of the selected muscle(s) could distinguish /p/ from /b/ in English and /ph, p′/ from /p/ in Korean. The English /p/ and the Korean aspirated /ph/ and unaspirated /p′/ were tense, and the English /b/ and the Korean unaspirated /p/ lax. Findings: (1) The EMG data, obtained from the orbicularis oris superior muscle and the depressor anguli oris muscle, supported the tense–lax opposition, except for one English subject in stressed syllables; (2) The leveled peak intraoral airpressure, an output of the synchronized respiratory muscle activities during bilabial stops, backed up the tense–lax distinction, except for one English subject in unstressed syllables, and there was intermuscle compensation between the labial muscle activities and the respiratory muscle activities; (3) The data of the maximum lingual contact in alveolar stops also supported the tense–lax distinction theory. Thus it can be said that the hypothesis has been verified in both languages.
Effects of front/back energy ratios of early and late reflections on listener envelopment
Authors: Morimoto Masayuki , Iida Kazuhiro
Published: July 2002

A previous paper [M. Morimoto and K. Iida, J. Acoust. Soc. Am. 93, 2282 (1993)] indicated that the listener envelopment (LEV) grows as the energy of reflections coming from the back of the listener increases. This paper investigates which is more effective for LEV, the F/B ratio of early or late reflections. In the experiments, a music motif is used as a source signal. The F/B ratios in the early and late reflections are changed independently, but the C value, the degree of interaural cross correlation, and the sound-pressure level of all sound fields are kept constant. The experiments were performed by using a paired comparison test. The task of the subjects was to judge which sound field had higher LEV. The experimental results indicate that the F/B ratio of both of the early and late reflections have an effect on LEV but that the latter is a little more effective for LEV than the former. This result suggests a relation between the perception of LEV and the law of the first wavefront.
Subjective attributes for sound fields from a model of the auditory-brain system
Authors: Ando Yoichi , Sakai Hiroyuki , Sato Shinichi
Published: July 2002

Based on physiological responses, a model of the auditory-brain system may be proposed. The model consists of the autocorrelation mechanisms, the interaural cross-correlation mechanism between the two auditory pathways, and the specialization of human cerebral hemispheres for temporal and spatial factors of sound field. The specialization of the human cerebral hemisphere may relate to the highly independent contribution between the spatial and temporal criteria of sound fields on subjective preference judgments. In addition, based on the model, any other subjective attributes of sound fields can be described in terms of processes of the auditory pathways and the brain. For example, the phenomena of missing fundamental, loudness and coloration, the threshold of perception, and preferred delay of a single reflection are well described by the autocorrelation mechanism. The subjective diffuseness and ASW are described by the interaural crosscorrelation function. Even so-called ‘‘cocktail party effects’’ may well be explained by such specialization of the human brain, because speech is processed in the left hemisphere, and the directional spatial information is mainly processed in the right hemisphere. [Work was partially supported by the Ministry of Education, Grant-in-Aid for Scientific Research (C), 9838022, 1997.]
Reflected sound field by stage floors in the concert halls: Theoretical model analysis
Authors: Nakanishi Shinsuke , Sakagami Kimihiro , Morimoto Masayuki
Published: July 2002

This paper theoretically analyzes a reflected sound field by the stage floor which is modeled as an infinite elastic plate with a point force excitation. Models of infinite elastic plates backed with either an air cavity or an absorptive cavity, which are often seen in stage floors of concert halls, are also considered. The far-field expression for the solution to the reflected field is derived by coupling the Helmholtz integrals for the sound fields surrounding the plate and the equation of motion for the plate. The main features of the reflected field are as follows: (1) A significant peak appears around the coincidence frequency. (2) The reflected field fluctuates due to interference between the reflection by the plate without the point force and the radiation from the plate excited by the point force. (3) The reflection characteristics show the panel absorption dip caused by a mass-spring resonance of the plate-cavity system and many small dips and peaks due to acoustic resonances of the back cavity. Effects of the parameters of the plate and cavity on the reflected sound field are discussed through numerical examples.
A porous medium with porosity variations
Authors: Chotiros Nicholas P.
Published: July 2002

The BiotUs equations of acoustic propagation in porous media have no inherent scattering mechanism, because the pores are modeled as smooth-sided tubular passages with constant cross section. They predict two compressional and one shear wave that propagate independently. Real porous media usually have pores with varying cross section, which may be considered as variations in porosity on a microscopic scale. Although any single variation on such a scale would have a negligible effect on the acoustics of the medium, the cumulative effect of a field of such variations is unknown. A one-dimensional structure with varying porosity was modeled numerically to study its properities as an acoustic medium. It was found that, not only does it possess an inherent volume scattering strength, but it also allows energy transfer between the three types of waves as they propagate. [Work supported by ONR 321 OA.]
Broadening the frequency range of panel absorbers by adding an inner layer of microperforated-plate
Authors: Kang Jian , Zha Xueqin , Fuchs Helmut V.
Published: July 2002

A disadvantage of panel absorbers, namely a panel backed by an airspace, is that the effective frequency range is usually rather narrow. It has been theoretically demonstrated that the absorption range can be broadened by introducing a microperforated-plate between the panel and the back wall [J. Kang, IBP Report 1993]. In this paper, a series of experimental results on the effectiveness of this method is presented. The experiments were carried out using the single microphone FFT technology in an impedance tube. It is shown that with an inserted microperforated-plate the acoustic resistance of the whole structure is greater than that of the outer panel alone. When the parameters of the microperforated-plate are carefully selected, the absorption range can be effectively extended in both low- and high-frequency directions. Typically the improvement is around 1 oct. The effectiveness of the microperforated layer is much less when its resonance frequency is considerably higher than that of the outer panel alone. [Work supported by AvH.]
Sound absorption measurements in diffuse field: A study of parameters
Authors: Nabuco Marco , Massarani Paulo , Tenenbaum Roberto
Published: July 2002

Many researchers have been studying the sound absorption coefficient measurement technique in reverberation chambers, since Sabine presented his formulation during the end of the last century, in order to find reasons for data frequently obtained bigger than 100%, normally correlated to the edge effects of the sample. Some researchers have studied the implications of the lack of diffuseness on the sound absorption data. This paper presents the data obtained for the sound absorption coefficient measured in a 200-m3 reverberation chamber at the National Institute of Metrology, Standardisation and Industrial Quality-INMETRO, in Brazil, for different areas and configurations materials, from 1 to the standardized 12-m2 sample. Also presented is the steady-state standard deviation, the cross-correlation between microphones, and the shape of the decays curves to qualify the diffuseness both in steady as well as during the transient state. At last is presented the data obtained using a steady-state measurement of the sound absorption using a standard reference sound source calibrated in semianechoic chamber.
Effects of flow resistance on acoustic performance of permeable elastic-plate absorbers
Authors: Tanaka Manabu , Takahashi Daiji
Published: July 2002

In general vibration theories of thin elastic plate, the plates have been assumed to be nonpermeable. However, previous work on permeable membranes revealed that the acoustic properties of a membrane are strongly affected by its permeability [Takahashi et al., J. Acoust. Soc. Am. 99, 3003–3009 (1996)]. In this study, permeable elastic-plate absorbers are proposed and their acoustic performance is examined by means of numerical analysis. For the simplest model, a theory for sound transmission through and sound reflection by a single permeable plate absorber with the oblique incidence of steady-state plane wave is developed. In this theory, permeability of the plate is represented by unit-depth flow resistivity [MKS-rayl/m]. Subsequently, for more complex models, structured absorbers composed of the facing of a permeable plate and several layers of air and/or absorptive materials are investigated theoretically. With these theoretical models, parametric surveys are executed to evaluate the acoustic performance of permeable elastic-plate absorbers. As a result of numerical calculations, it becomes clear that the flow resistance of the permeable elastic plate has a remarkable influence on its acoustic characteristics, especially at high frequencies.
Stone tracking with time-reversal techniques
Authors: Thomas J. L. , Fink M.
Published: July 2002

Time reversal of ultrasonic fields allows a very efficient approach to focusing pulsed ultrasonic waves through lossless inhomogeneous media. Time reversal mirrors (TRM) are made of large transducer arrays, allowing the incident acoustic field to be sampled, time reversed and reemitted. Time reversal processing permits a choice of any temporal window to be time reversed, allowing operation in an iterative mode. In multitarget media, this process converges on the most reflective target, i.e., the dominant scatterer. The time reversal process is applied to track, in real time a moving gall bladder or kidney stone embedded in its surrounding medium. The feasibility of adaptative beam forming techniques to track the stone during a lithotripsy treatment is investigated. It is shown that TRM allows sharp focusing on one bright point of the stone. Once the bright point is selected, a time of flight profile is determined and used in a least-mean-square method to calculate the spatial coordinates of the stone. Stone trajectories can be tracked by this technique at 30 Hz.
Resonant frequencies in degeneration of hybrid longitudinal and torsional vibration system
Authors: Zhang LiQun , Zhou TieYing
Published: July 2002

The Langevin vibrator is made of the longitudinal and torsional piezoelectric plates, which can be used for an ultrasonic motor and an ultrasonic welding transducer. Because of the difference between the longitudinal and torsional sound velocity, their resonant frequencies are not equal. To make resonant frequencies of two vibration modes in degeneration, a matching block with a thin neck was connected to the end of the vibrator. Two calculation methods, a dimension network which transmits matrixes and a finite element method have been used. The feasibility of frequencies tuning through a matching block has been analyzed and how to effect the resonant frequency by the radius and thickness of the thin neck and matching block has been summarized. The resonant frequencies of several steel cylinders with variant thin necks and matching blocks were calculated. Some experimental results of measuring the resonant frequencies have been compared with the calculation. According to the calculation and experimental results, a prototype of hybrid longitudinal-torsional ultrasonic motor has been manufactured, and it can be operated very well [Tomikawa et al., IEEE Trans. Ultrason. Ferroelectr. Freq. Control 39 (1992)].
Lumped impedance of a planar discontinuity in an acoustic waveguide
Authors: Muehleisen Ralph T. , Atchley Anthony A.
Published: July 2002

When modeling planar discontinuities in acoustic waveguides at low frequencies, the standard assumptions involve continuity of pressure and volume velocity at the discontinuity. While continuity of volume velocity is required by mass conservation, excitation of evanescent higher-order modes and thermoviscous loss suggest that pressure is not continuous across the discontinuity. Such a pressure loss can be modeled by a series acoustic impedance. A new model for a lumped series impedance at a planar waveguide discontinuity has been developed and is presented. The model uses a modal expansion of the acoustic field near the discontinuity and matrix techniques to obtain a closed-form approximation for the resistive and reactive elements of the series impedance. As an example of the accuracy of the model, the prediction of the resonance frequency of a constricted annular resonator is presented. [This work was supported by the Office of Naval Research and the American Society of Engineering Education.]
Time-resolved measurements of optical emission from sonoluminescence
Authors: Froula D. , Lee R. W. , Moss W. C. , Young P. E. , Matula T. J.
Published: July 2002

The results of detailed measurements of sonoluminescence from a gas bubble that is acoustically driven in deionized water are presented. The pulse width and relative jitter of the optical flash and the minimum and ambient radius of the bubble as a function of the driving pressure, temperature, and gas concentration of the water are measured. The optical flash is collected by an f/1.4 lens, and then optically relayed onto the slit of a Hamamatsu C1587 optical streak camera which records the time evolution of the flash with picosecond resolution. Single event streaks are obtained, showing FWHM pulse widths of 200–400 ps, comparable to recently reported results [Gompf et al., Phys. Rev. Lett. 79, 1405 (1997)]. The jitter of the flash between events has been found to be a minimum of ±200 ps. Mie scattering has been used to measure the maximum and ambient bubble radius at the same time for comparison to the model [Moss et al., Science 276, 1398 (1997)]. The consequences of these results on modeling will also be discussed. [This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.]
On the theory of supercompression of a gas bubble in a liquid-filled flask
Authors: Nigmatulin Robert I. , Akhatov Iskander Sh. , Vakhitova Nelya K. , Lahey Richard T.
Published: July 2002

The spherically symmetric problem of the oscillations of a gas bubble in the center of a spherical flask filled with a compressible liquid that is excited by pressure oscillations on the flask wall is considered. A generalization of the Rayleigh–Plesset equation for a compressible liquid is given in the form of two ordinary difference-differential equations that take into account the pressure waves that are reflected from the bubble and those that are incident on the bubble from the flask wall. The initial value problem for the initiation of bubble oscillations due to flask wall excitation and for the evolution of these oscillations is considered. Linear and nonlinear periodic bubble oscillations are analyzed analytically. Nonlinear resonant and near-resonant solutions for the bubble nonharmonic oscillations, which are excited by harmonic pressure oscillations on the flask wall, are obtained. The influence of heat transfer phenomena on the bubble oscillations is analyzed.
Thermal wave from a sonoluminescing gas bubble
Authors: Lee Yoon-Pyo , Karng Sarng-Woo , Kwak Ho-Young
Published: July 2002

Heat diffusion from the sonoluminescing gas bubble which produces a high temperature and pressure environment adjacent to the bubble wall was considered by solving the heat diffusion equation numerically. The boundary conditions employed in this calculation are the time-varying bubble wall temperature obtained from the analytical solutions around the collapse point. The thermal boundary layer was found to be decreased rapidly during the collapse as expected. The heat flux at the collapse exceed 3 GW/m2. After the collapse a solitonlike heat wave, which was generated due to the rapid increase in the bubble wall temperature at/near the collapse for the sonoluminescing gas bubble, was found to propagate through the medium. On the other hand, the liquid temperature near the bubble decreases after the collapse for the nonsonoluminescing case. [Work supported by Korea Science and Engineering Foundation.]
Effect of quantum radiation pressure on the bubble dynamics in sonoluminescence
Authors: Chen Weizhong , Wei Rongjue
Published: July 2002

In the theoretical frame of quantum vacuum radiation (QVR), the effect of the QVR on the gas bubble dynamics in the single bubble sonoluminescence is studied. The dominated hydrodynamic equation of the gas bubble trapped in a liquid, Rayleigh–Plesset equation, has been modified by considering the reaction of the radiation force on the bubble surface and therefore causing a loss of energy. In the modified model the collapse and expansion of the bubble, especially near the turnaround at minimum radius, related to photon emission instead of independence on it. The numerical computation shows that the emission energy due to the QVR seems too low to explain the experimental data, if some present values of parameters, such as the ambient radius of the bubble and the sound pressure in liquid, are used. The radiation energy due to the QVR, however, can arise by changing those parameters. Based on this, it is concluded that the QVR may be a possible candidate for mechanisms of the sonoluminescence. [Work supported by NSF of China.]
Chaotic dynamics in acoustics
Authors: Lauterborn Werner H.
Published: July 2002

The theory developed for the description of chaotic and nonlinear dynamical systems also pertains to acoustics. A survey is given of the new ideas and methods that for experimentalists rely on the embedding of experimentally obtained data (time series) into high-dimensional spaces. The embedding is the starting point of nonlinear time series analysis for determining the static (fractal dimensions) and dynamic (Lyapunov exponents) properties of the point sets (attractors) obtained. Acoustical systems that can be investigated with these methods are, for instance, vibrating liquid surfaces (Faraday experiment), vibrating machines, musical instruments, nonlinear oscillators, speech and hearing, bubble dynamics, and acoustic cavitation.
Determination of the acoustic nonlinearity parameter B/A using a phase locked ultrasonic interferometer
Authors: Davies Jevon R. , Tapson Jonathan , Mortimer Bruce J. P.
Published: July 2002

The acoustic nonlinearity parameter B/A is an important parameter for characterizing acoustic propagation in fluids. Recent developments in the fields of shock waves and biomedical ultrasonics have necessitated an accurate method for measuring this quantity. This paper presents a new technique based on an ultrasonic interferometer that allows accurate measurements of the change in sound speed within a liquid cavity. The system makes use of a novel continuous wave phase locking principle, which has the effect of nullifying many of the nonlinearities inherent in the acoustic interferometer. The phase lock circuitry automatically adjusts the frequency so as to keep an exact integer number of waves in the cavity regardless of changes in sound speed. Using this principle, B/A is determined by relating a small change in ambient pressure (less than 2 bar) to a change in frequency under isentropic conditions. B/A values are calculated using this experimental setup for several liquids including two slow sound-speed fluorocarbon liquids, FC-43 and FC-75. These liquids are unique in that they have the lowest range of sound speeds of any organic liquids and in that they have the highest values of B/A recorded thus far.