bluuebunny/crossref_metadata_2025 huggingface dataset:
Rayleigh wave solitons in layered media
Authors: Odom Robert I.
Published: July 2002

The problem of weakly dispersive long waves in a thin nonlinear solid layer over a linear isotropic solid half-space is formulated as a nonlinear thin plate problem with one free surface and one surface bonded to the underlying linear isotropic half-space. If terms cubic in the displacement gradient are retained in the nonsymmetric Piola–Kirchoff stress tensor, a multiple-scale perturbation analysis of the equations of motion leads to the Benjamin–Ono equation ut+αuux+βℋ[uxx]=0, where u is a particle displacement, ℋ[⋅] indicates the Hilbert transform, and α and β are constants that depend on the material properties of the layer and half-space. The Benjamin–Ono equation admits soliton solutions, and can be solved by the inverse scattering transform. This work may provide a mathematical model for small amplitude nonlinear seismic waves propagating in a thin sediment layer over a much harder basement. It may also have application to surface acoustic wave (SAW) device physics.
Cross-modal links between auditory and visual attention
Authors: Spence Charles , Driver Jon
Published: July 2002

Using the orthogonal spatial-cuing paradigm, it has been shown that people make elevation discriminations concerning target sounds more rapidly and accurately when auditory targets are presented at covertly attended azimuths location [C. Spence and J. Driver, J. Exp. Psychol. Hum. Percept. Perform. 20, 555–574 (1994)]. These shifts of auditory spatial attention could either be elicited endogenously, by informative cues that predicted the likely target location, or exogenously by peripherally presenting spatially uninformative auditory cues. More recently, extensive cross-modal links between audition and vision in the control of both exogenous and endogenous orienting have been reported, such that, for example, a shift of auditory attention typically leads to a shift of visual attention to the same location [C. Spence and J. Driver, J. Exp. Psychol. Hum. Percept. Perform. 22, 1005–1030 (1996)]. Participants in all previous behavioral studies of crossmodal attention had their eyes and head in spatial alignment. New data is reported showing a partial remapping of audiovisual space when the eyes and head are misaligned (i.e., when people look out of the corner of their eyes). This remapping ensures that attention is oriented to the correct distal location, irrespective of receptor misalignment. [Work supported by MRC (UK).]
Numerical method using filter banks for vibroacoustic analysis in the medium frequency domain
Authors: Gorog Sylvie , Micheau Philippe
Published: July 2002

Efficient numerical tools are needed to predict the vibroacoustic response of a viscoelastic structure in the medium frequency range. The presented method is formulated within the framework of nonuniform modulated filter banks, a signal processing tool. The structure is described using a variational approach. The method consists of dividing the frequency domain of interest into several subdomains and hence solving a time domain equation of motion for each subdomain. The complete displacement field is then reconstructed from the different time domain solutions. This time-frequency computations rely on the design of analysis and synthesis filter banks. Flexural vibrations of plates in vacuo are studied to illustrate the numerical efficiency of the method. According to the variational approach that is used, results show that the proposed method allows the computation of the solution in frequency domains where classical modal methods and direct methods are limited from a numerical point of view. This numerical tool is of great interest for the study of structures having frequency-dependent properties.
Updates on becoming a native listener
Authors: Werker Janet F. , Pegg Judith E. , Shi Rushen , Stager Christine
Published: July 2002

Infants’ sensitivity to the sound structure of the native language becomes finely honed during the first year. New studies confirm and extend this fact in the domains of phonetic, metrical, and grammatical processing. First, infants were tested on their ability to discriminate phonetic, but nonmeaningful differences in the native language. Although most 6- to 8-month olds discriminated [d] versus [t], 10- to 12-month olds did not. Thus, by 10–12 months, infants listen to only those phonetic differences that distinguish acceptable native-language syllabic shapes. Next, English-learning infants’ discrimination of single syllable words such as ‘‘clone’’ from their WS counterparts, e.g., ‘‘cologne’’ was examined. Testing infants from the newborn period through the first year of life revealed that this ability is not robustly evident until around 10 months. Finally, the authors asked whether infants are sensitive to the acoustic and phonological cues distinguishing content from function words. Using lists of content versus function words excised from infant-directed utterances, it was found that both neonates and 6-month olds distinguished these broad grammatical categories. These studies confirm and extend our understanding of initial biases and listening experiences on infant speech processing. A critical question the authors are now addressing is how these changes in speech perception prepare the child for language learning.
Matched-field inversion using the down hill simplex algorithm
Authors: Musil Martin , Ozard John M. , Wilmut Michael J.
Published: July 2002

In recent years inversion techniques have been proposed to effectively and efficiently determine geophysical parameters. The focus of this matched-field inversion (MFI) study is to determine the geoacoustic and geometric parameters for a North-East Pacific shallow water data set. MFI correlates modeled data, called replicas, with the measured data and uses a search algorithm to find model values which maximize the correlation function. In our MFI the parabolic equation (PE) is used to compute the replicas to account for mode coupling in the range-dependent environment. The first stage of the optimization algorithm employs a random search to determine N+1 parameter sets with the best correlations, where N is the number of parameters being determined. Next the N+1 sets are the input to the downhill simplex algorithm. The algorithm is shown to perform well for simulated vertical line array data for search parameter ranges representative of the environment in the shallow North-East Pacific Ocean. The inversion technique was then applied to measured data obtained in the North-East Pacific on the continental shelf using towed CW and broadband sources and a vertical array of hydrophones. The geometric parameters of the experiment and dominant geoacoustic parameters were successfully recovered.
Geoacoustic parameter inversion from waveform structure
Authors: Li Fenghua , Zhang Renhe
Published: July 2002

Based on the beam-displacement ray-mode (BDRM) sound propagation model, the effect of the bottom reflection coefficient on the pulsed waveform structure in shallow water with a thermocline is discussed. Simulated numerical calculations show that in shallow water with a thermocline, the bottom reflection amplitude and the bottom reflection phase can be inverted by the envelope of the pulsed waveform and the pulsed waveform structure, respectively, when the source and/or the receiver are above the thermocline. Using the experimental data from ’96 China–US Far Yellow Sea Experiment, inversions for bottom reflection amplitude and reflection phase are performed. The waveform correlation between the experimental waveform and the inversion waveform is about 0.88 while the envelope correlation between them is about 0.95. The inversion of the experimental data shows that the inversion for the bottom reflection coefficient is effective and the inversion results are stable when the source and/or the receiver are above the thermocline. [Work supported by NSF of China and ONR of USA.]
Frequency dependence of acoustic response due to randomness and uncertainties in physical properties of porous media
Authors: Mu Yongke , Badiey Mohsen , Cheng Alexander H.-D.
Published: July 2002

Models of acoustic waves in porous media are complicated because of the multiple physical parameters involved. The physical structure of these parameters can be random, and the accuracy toward their direct measurement or indirect estimate is generally uncertain. In order to better understand the extent by which different parameters can affect the interaction between the acoustic waves and the porous media, these randomness and uncertainty issues need to be addressed. In this paper, the investigation is based on the Biot model. First, the model is improved based on effects arising from the statistical distribution of pore/grain size. Next, effects of randomness in sediment stratigraphy are examined. Also, we take into consideration the uncertainty resulting from data scarcity. Numerical tools used include propagator matrix, PE, and Monte Carlo simulation. From the variation of different parameters a different result is found. But frequency is found to always play an important role. For example, at lower frequencies the effects of pore/grain size can be neglected, but at higher frequencies they have significant impact. The material frequency response for the microscopic and macroscopic randomness is examined here. The results offer a better understanding of the interaction between the acoustic waves and the porous media.
Range-dependent environmental mismatch in matched-field tomography (MFT)
Authors: Kessel Ronald T.
Published: July 2002

The goal of MFT is to determine unknown geoacoustic properties of the ocean by fitting a model to data recorded when the source–receiver configuration is known. The best-fit model presumably gives the best estimate of the actual geoacoustic properties along the propagation path. But the best-fit model, like the family of trials from which it is drawn, is necessarily constrained and idealistic. For simplicity, the horizontal variation of the sediments and bathymetry might have been ignored, and all trials might have had the same number of sediment layers, fixed arbitrarily perhaps, with each trial simply assigning different geoacoustic properties to those layers. If the best-fit model does not match the actual environment in these and other respects, then in what way does its properties represent those of the actual environment? When is the best-fit narrowly functional, fitting one data set well enough, but failing given other source–receiver configurations or frequency bands? These fundamental questions are addressed using the adiabatic theory of mode propagation, following a general perturbative approach to mismatch in any geoacoustic parameter in weakly range-dependent environments. Systematic and random mismatch are considered, and the implications for MFT are explored.
Stochastic effects in ocean acoustics. Advances in theory and experiment
Authors: Uscinski Barry J.
Published: July 2002

As the need to operate in the kilohertz range increased in the 1960s, existing approaches to ocean acoustics, based on sound-speed profiles and ray-tracing, became quite inadequate. The raggedness of acoustic transmissions, previously regarded simply as noise, was so pronounced at the higher frequencies that the stochastic properties themselves became an urgent area of research. Several major ocean transmission trials were carried out to obtain fluctuation data. The trial at Cobb Seamount produced results that could not be explained by existing random-wave propagation theory. The research that followed led to significant advances in several areas. New propagation theory emerged based on the parabolic equations for the acoustic field moments. In particular it was the construction of analytical solutions of the equation for the fourth moment that provided the first satisfactory explanation of the Cobb intensity fluctuation spectra. Advances in numerical simulation methods and capability have allowed pictures of the full stochastic acoustic field in an ocean transmission trial to be produced. These have not only confirmed experimental variances and cross correlations but have also revealed the spatial structure of the field, including interesing features such as the elongated sound ribbons that arise in some cases.
Concert hall research: Balancing complexity and practicality
Authors: Bradley John
Published: July 2002

An approach that has carefully balanced complexity and practicality has led to several new developments in concert hall research. These new developments are reviewed and their practical implications are explored. The two separate dimensions of spatial impression, apparent source width and listener envelopment, are each related to different physical parameters. The relationship between these acoustical parameters and the design of halls will be explored. For example, listener envelopment is related to the relatively late arriving lateral sound energy. Measurements in a number of halls will be used to explore how this and other acoustical measures of spatial impression are related to hall design. This same new understanding of spatial impression can also further enhance our understanding of sound fields under balconies and help us to design improved electroacoustic enhancement systems. Spatial impression is also influenced by sound level and especially by lower frequency levels. The importance of levels and the balance between high- and low-frequency levels has often been neglected. New work relating the perception of bass and treble sound to different factors will be reviewed. Previous studies and new analyses will be used to explore how hall design can influence perceptions of tonal balance in concert halls.
Near-resonance scattering from schooling fish
Authors: Nero R. W. , Thompson C. H. , Feuillade C. , Love R. H.
Published: July 2002

Most fish have air-filled swimbladders which provide some buoyancy to aid in swimming. These swimbladders resonate like damped air bubbles and are very efficient scatterers. A mathematical formalism has recently been developed to describe near-resonance backscattering from schooling fish. [C. Feuillade, R. W. Nero, and R. H. Love, J. Acoust. Soc. Am. 99, 196–208 (1996)]. This model predicts that coupled resonance and interference effects will occur when fish are closely spaced. These effects cause the frequency response of a tightly packed school to differ significantly from that of a single fish. As fish spacings increase beyond several body lengths, these effects rapidly diminish. When this model was developed, only one small set of data was available for comparison to model predictions; these data gave indications that the model was valid [Holliday, J. Acoust. Soc. Am. 51, 1322–1332 (1972)]. Experiments off the west coast of the United States and in the Gulf of Mexico have recently been conducted on several different species of schooling fish in order to confirm the validity of the model and determine its robustness. Measurements on numerous schools confirm that scattering from schooling fish is accurately represented by the model. [Work supported by ONR/NRL.]
The ring-type all-fiber Fabry–Perot interferometer hydrophone system
Authors: Li Donglin
Published: July 2002

In the paper the theory of the ring-type all-fiber Fabry–Perot interferometer hydrophone is given. Such a hydrophone system has been constructed. Experimental results have shown the system has a free-field open-circuit voltage sensitivity level of about −130 dB re: 1 V/μPa.
Sonic gas analyzers
Authors: Golden Matthew V. , Keolian Robert M. , Garrett Steven L.
Published: July 2002

Whistles were used to determine the presence of hydrogen and/or methane in mines before 1900 in Germany. Since early in the 20th century, the measurement of gas thermal conductivity using a hot wire technique has been the method of choice for nonspecific detection of ‘‘contaminating’’ gases in air. At that time, the choice of thermal conductivity detectors was motivated by the popularity of the Wheatstone Bridge circuit for precision measurement [P. E. Palmer and E. R. Weaver, ‘‘Thermal-conductivity method for the analysis of gases,’’ Tech. Papers of the Bureau of Standards, No. 249, Vol. 18, Jan. 7 (1924)]. At the present time, the precision-to-cost ratio for frequency/time measurements exceeds that for voltage/current measurement by more than an order of magnitude. This presentation will examine the advantages which an electronic measurement of sound speed using inexpensive components and novel resonator geometries can bring to the detection of gaseous contaminants in air. Prototype sensor/electronics results will be presented. A discussion of temperature compensation techniques as well as the sensitivity to changes in pressure and humidity will be included. [Work supported by ONR.]
Measurement of third-order elasticity in isotropic solids
Authors: Qian Z. W. , Jiang Wenhua
Published: July 2002

The responsibility of second-order harmonics to the SV incidence was investigated in an isotropic solid such as aluminum, and each sample to be measured was designed as a semicircular disk of which the cross section is a semicircular polygon in order to provide many incidental angles for measuring. The displacements of both the linear and second-order waves were observed in the area near the center of the semicircle, where the surface is stress free. According to the theory proposed by one of the authors (Qian), the third-order elastic constants can be obtained acoustically by the inverse techniques.
Nonlinear acoustics of zero-volume nonbonds and cracks
Authors: Solodov Igor Yu.
Published: July 2002

The results of experimental investigation of nonlinear acoustic phenomena for surface (SAW) and bulk waves (BAW) in materials with nonbonded interfaces and closed cracks are reported. Several mechanisms of acoustic nonlinearity specific for such materials were found and analyzed. In a propagation mode SAW harmonics generation and wave interaction effects revealed two to three orders of magnitude increase in nonlinear parameter values for a nonbonded interface. Unconventional higher harmonics ratio was measured and manifested in a distinctive nonlinear SAW waveform distortion. Efficient generation of harmonics forbidden in homogeneous isotropic solids was observed for shear BAW in the presence of nonbonds and cracks. Peculiar rectification effects were found for SAW propagation and BAW reflection at an interface and shown to result in both acoustic broadening and creeping of a nonbonded area. Extremely high efficiency was measured for nonlinear BAW–SAW transformations accompanying combined three-wave interactions at a nonbonded interface. In a reflection mode such an interface demonstrated a unique feature of nonlinear reflection with inverse spectral distribution of the harmonic amplitudes. Some prospective applications of the effects observed were demonstrated in signal processing, tribology, and nonlinear NDE of zero-volume nonbonds and closed cracks.
A novel octave graphic equalizer
Authors: Hribsek Marija F. , Tosic Dejan V.
Published: July 2002

An octave constant Q graphic equalizer using a new class of active bandpass filters is presented. It covers all 11 standard octaves in a frequency range from 16 Hz to 20 kHz. The level in each octave can be changed within ±20 dB with respect to the reference level which corresponds to the zero dB gain of the equalizer. The advantages of the proposed bandpass biquads are the use of only one operational amplifier per octave, a very small resistors spread ratio, and equal values of the resistors in all octaves. The computer simulation has been used to verify the design of the novel circuit. The new design has been compared to the existing solutions reported in the literature. The comparison shows excellent agreement with the published results. The effects of the finite gain and bandwidth of the real operational amplifier have also been investigated. The proposed new equalizer shows to be robust against these amplifier imperfections.
An 800 bps VQ-based LPC voice coder
Authors: Wang Xianglin , Kuo C.-C. Jay
Published: July 2002

In this paper, it is investigated how to efficiently apply VQ on LPC so as to realize a very low bitrate speech coder with reasonable speech coding quality. The coding bitrate has been pushed to 800 bps and the result is compared with that of a traditional LPC 2.4 kbps speech coder. In LPC10 standard(FS1015), scalar quantization is adopted to quantize the LPC parameters. However, when vector quantization is considered, the speech coding rate can be further reduced without obvious degradation of speech quality. In our coding scheme, instead of direct encoding of LPC parameters, LSF coefficients are encoded which are obtained from a transformation of LPC. In addition, in order to utilize the correlation among LPC parameters, three frames of speech are processed together so that some kind of prediction could be utilized. A weighted version of MSE is selected as the distortion measure in building the VQ codebooks and encoding. Also, due to their different characteristics, separate codebooks are built and used for voiced and unvoiced speech to better match their statistical properties. The result of our experiments shows that our 800 bps speech coding scheme can achieve similar quality to that of the LPC 2.4 kbps speech coder.
A study on the speech analysis and recognition for Korean children
Authors: Park Eunjung , Kam Jieun , Paek Inchan , Kwon Y. , Lee K. S. , Yang Sung-il
Published: July 2002

This paper describes a speaker-independent Korean ten-digit recognizer for males and females from 10 to 13 years old, who have a serious variation of speech characteristics. DHMMs with time normalized ten-dimensional LPC, CEPSTRUM, LSF coefficients, and ten-band energies in frequency domain as the feature vector are used. The pitch and formant informations are extracted to analyze speech characteristics. Through experiments, DHMM recognizer shows the performance of recognition rates, 67.1% (LPC vectors), 80.8% (CEPSTRUM vectors), 66.7% (band energies in frequency domain), and 83.8% (LSF vectors).
Reducing sibilants in recorded speech using psychoacoustic models
Authors: Sapp Markus , Wolters Martin , Becker Joerg
Published: July 2002

Sibilants are a known problem in speech recording. Even though they can often be decreased by a different placement of the microphones, there still is the necessity for methods that reduce these artifacts. Therefore new investigations on sibilants in German, English, Spanish, and French have been made to describe their properties in time and frequency domain. To find an adaptive algorithm which considers these properties a reliable method is needed for detection and classification of the different kinds of sibilants. It is shown that the psychoacoustic unit ‘‘sharpness’’ is well correlated with the appearance of these sounds and that specific loudness, an intermediate step in calculating sharpness, can be utilized to get information about the spectral properties of each sibilant. An algorithm is presented which employs sharpness to detect sibilants and reduces them using variable filters.
Observations of coherence frequency and amplitude fluctuations in a shallow-water acoustic communications channel
Authors: Shockley Richard , Rice Joseph , McDonald Vincent , Green Dale , Proakis John , Newton John
Published: July 2002

This work examines the statistics of a fading, dispersive shallow-water channel, specifically the distribution of amplitudes and the correlation between fluctuations in amplitude at different frequencies in the 8- to 12-kHz band. Signals considered include frequency-hopped, 50-ms duration, CW pulses and 500-ms linear FM chirps sent over a 15-m deep, 1-km range channel. Physical origins and implications for communications receivers of the observed non-Gaussian or non-Rayleigh behavior are briefly discussed. [Work supported by the SSC San Diego Independent Research Program, sponsored by the Office of Naval Research.]
Phase-encoded frequency-hopped signaling for underwater acoustic communications
Authors: Edelson Geoffrey , Gillespie Bradford
Published: July 2002

Phase-coherent digital communications systems require complicated receivers to overcome the intersymbol interference caused by the time-varying multipath propagation of shallow-water acoustic channels. However, many of these channels feature ‘‘sparse’’ impulse responses in that the received signal arrives in distinct clusters separated by time periods in which little signal energy arrives at the receiver. If the phase-coherent message is divided into multiple ‘‘minipackets’’ such that the minipacket duration is shorter than the time span between the distinct multipath clusters, then the receiver configuration can be simplified considerably. The short packets may be frequency hopped so that a given frequency is vacated until subsequent multipath arrivals have died out. Each minipacket is decoded using a maximum-likelihood decoder. If each chip is not phase-encoded, the system reduces to a noncoherent frequency-hopped modulation technique. Experimental results are included to demonstrate the potential performance of this approach.
Sound transmission through suspended ceilings
Authors: Mechel F. P.
Published: July 2002

Suspended ceilings passing over a partition wall between adjacent rooms are a path of sound transmission from room to room for which, until recently, no analytical and satisfactory theory existed, although suspended ceilings are a common system of construction. The principal features of an analysis are outlined for the sound fields in the adjacent rooms, in the plates and absorber layers of the suspended ceiling and in the common plenum above the ceiling. The theory is based on a modal analysis. It not only shows the mechanisms of the sound transmission, which in contrast to common ideas, are quite different on the emission and on the receiving sides, but it also gives numerical results which agree (within the precision of measurements) with experimental data. The influence of geometrical parameters (e.g., plenum height, room width) and of material parameters (e.g., absorber layer thickness) can be demonstrated quantitatively.
Orchestra pit acoustics: From Bayreuth to Broadway
Authors: Holden Mark
Published: July 2002

The design of orchestra pits for opera, ballet, and multiuse halls is examined from an historical perspective. The earliest orchestra pit designs for early European opera houses were open or ‘‘bathtub’’ pits holding few musicians on a single level. Pits remained similar until 1872 when Wagner’s Bayreuth pit changed the musician/vocalist orientation by extending the pit below the stage edge in stepped tiers. Modern pit designs have varied from large ‘‘bathtub’’ pits (the Metropolitan Opera, San Francisco) to ‘‘modified Bayreuth’’ pits (Houston, Seattle, etc.) with varying degrees of success. Issues concerning musicians’ comfort, loudness levels, and hearing loss are discussed along with ways to improve acoustics in the overhung area. Finishes and materials for walls, ceilings, and floors are discussed as well as adjustable acoustic panels, drapes, and walls that can be used to tune the pit for varying programs. Finally, solutions to the dilemma of Bayreuth versus Bathtub pits will be discussed.
Transmission loss measurement of multilayered partitions in time domain
Authors: Cherman Andre L. , Tenenbaum Roberto A.
Published: July 2002

Transmission loss through single-layered partitions depends on the superficial specific mass m of the material. A multilayered partition has, at each interface, an impedance jump that improves its transmission loss. Due to these characteristics, multilayered partitions can provide better sound insulation than a single-layered partition with the same thickness, being much lighter. In this work an experimental setup was built to study the transmission loss of a sample inside a duct. The partition is inserted between two sections of the duct and a pulse is generated at one side. The incident and the transmitted signals are captured by free-field microphones, and the time domain series, acquired with a two channel digital oscilloscope, provides the transmission loss. The impedance of the materials tested was found experimentally and compared with tables, when available. The experiment was performed in order to evaluate transmission loss in single-, double- and three-layered partitions. The experimental results were compared with numerical simulation using the software layer, developed in our laboratory, showing good agreement.
Applying the equivalent source method to the sound radiation from musical instruments in rooms
Authors: Svensson U. Peter , Nakano Mayumi , Sakagami Kimihiro , Morimoto Masayuki
Published: July 2002

Musical instruments often have rather complicated radiation characteristics which have been documented for the case of free-field radiation. This paper studies the effect of the source location relative to the room boundaries on the sound radiation from musical instruments in rooms. The musical instrument is modeled by the equivalent source method, or source substitution method, so that the real source is replaced by a set of simpler sources which approximately reproduces the vibrations on the instrument’s surface. A single corner with rigid walls is used to model the effects of the room boundaries on the sound radiation. As an example, a tympani is studied and theoretical expressions for its surface vibrations are used as input data. The directivity, and total power output, are then studied for various source locations. Possibilities for simplified source directivity modeling for room acoustical simulation are discussed.
Constraints on ocean internal wave spectra from long-range acoustic transmission data
Authors: Viechnicki John , Brown Michael G.
Published: July 2002

Both full wave and ray-based predictions of acoustic wavefields at long range in deep ocean environments are compared to their measured counterparts, including the SLICE89 and AET data sets. The environment for these experiments was characterized by weak climatological range-dependent sound-speed structure, weak mesoscale structure, and moderately strong (typical) internal-wave-scale variability. The acoustic measurements are used to provide constraints on the statistics of the internal wave field, using the Garret–Munk spectrum as a starting point. Our attention is focused on the following parameters to which our simulations are sensitive: the strength parameter E, the mode number cutoff jmax, and the horizontal wave-number cutoff values kmin and kmax. [Work supported by ONR.] a)The ATOC Group: A. B. Baggeroer, T. G. Birdsall, C. Clark, J. A. Colosi, B. D. Cornuelle, D. Costa, B. D. Dushaw, M. Dzieciuch, A. M. G. Forbes, B. M. Howe, D. Menemenlis, J. A. Mercer, K. Metzger, W. H. Munk, R. C. Spindel, P. F. Worcester, and C. Wunsch.
Preliminary results from a large-scale 3-D tomography experiment in the Kuroshio Extension region
Authors: Yuan Gang , Fujimori Hidetoshi , Nakamura Toshiaki , Nakano Iwao , Kamoshida Takashi , Zaima Tatsuo , Kaya Akio
Published: July 2002

A large-scale three-dimensional acoustic tomography experiment has been conducted in the Kuroshio Extension region from July to September 1997. Five 200-Hz transceivers were moored in the 1000-km-diam region approximately centered at 33° N, 149° E. Larger-scale environmental surveys (XCTD, CTD, XBT, and ship-boarded ADCP) were conducted along several acoustic transmission sections during the deployment and recovery cruises. The purpose of this study is to show the results of the preliminary analysis of this data. The stochastic inversions provide the time evolution of the large-scale three-dimensional temperature fields. The 4-D temperature fields dynamically show the variability of Kuroshio Extension with high time resolution. An active and resolvable mesoscale cold eddy is present with variability typically dominated by motions with spatial scales of 100–200 km. The 2-D temperature field along a 1000-km section derived from acoustic data agreed well with that determined from the XCTD measurements during the deployment cruise. The preliminary results of the data analysis suggest that it is possible to monitor 4-D structures of the large-scale ocean (1000×1000 km) by tomographic measurements (five transceivers giving ten paths), which is very difficult and almost impossible to do by traditional point measurements.
Ocean acoustic tomography using explosive charges to observe the submerged mesoscale oceanic variability in the East Sea of Korea
Authors: Na Jung Yul , Han Sang Kyu , Shim Taebo
Published: July 2002

A tomography system consisting of aircraft-deployed shots as sources and a vertical line array moored by a receiver ship was used to survey a large area (120×120 km) where a mesoscale warm eddy appears frequently. The position of the shots was measured by the GPS on the aircraft and the detonation time (or depth) was monitored by sonobuoys which had been deployed close to the shot position. Results show that individual multipaths between a shot and the receiver contain substantial information for a vertical slice of the ocean with a warm eddy. With high accuracy, GPS positioning of shot locations, and receiver position, this rapidly deployable system can be used for monitoring the submerged structure of the warm eddy during the period of diffusive SST in summer in the East Sea of Korea. [Work supported by KOSEF.]
Optical SonographyTM, a new method of diagnostic imaging
Authors: Garlick George F.
Published: July 2002

The characterization of Optical SonographyTM has been measured and is reported. This new soft tissue imaging method, which utilizes the capabilites of acoustical holography, passes a plane wave of ultrasound through the tissue which imposes phase and amplitude information on the wave. This wave then carries information of the three-dimensional structure of the soft tissue being imaged. When combined with an ultrasonic reference wave, an acoustical hologram is formed which is reconstructed with coherent light (hence the name Optical SonographyTM) to provide a real time image of the soft tissue. With Optical SonographyTM the image resolution is determined by the wavelength of sound interacting with points in the tissue rather than the focus size of the ultrasound as in the reflective mode. Thus theoretical limits of resolution are achievable; comparative resolution images will be presented. In addition, since over 99% of the ultrasound intensity passes through soft tissue interfaces, greater sensitivity is achieved. Imaging results using Optical SonographyTM will be presented.
High-frequency imaging of thickness degradation in steel containment vessels and liners
Authors: Bondaryk Joseph E.
Published: July 2002

An area of concern in some nuclear power plants is thickness degradation of embedded steel containments just below the interface where the steel enters concrete. This is an area which cannot be examined by traditional UT testing, due to the inaccessibility imposed by the concrete. In this numerical feasibility study, high-frequency vibrational sources placed above the interface are used to excite elastic waves in the steel, which propagate into the embedded area. The waves that reflect and scatter from the surface roughness caused by thickness degradation are detected and used to determine and map the degradation of the steel. A range-dependent, stratified layer, wave-number integration based, numerical model (OASES) is used to calculate the field in the scenario. Decomposition of the field into longitudinal, shear, and surface waves is used to determine the optimal transducer orientations for transmit and receive. [Work supported by the Nuclear Regulatory Commision.]
The error analysis of inverse algorithms for reconstructing the acoustical parameter profile of layered media
Authors: Lin Jun-xuan , Bao Qing-hua
Published: July 2002

Reconstructing the parameter profile of layered media is studied with the telemeter of tiny structure in hydrology, oil exploration, and the position selection of petroleum platform in the ocean. It is a much studied topic in the field of ocean acoustics. An inverse scattering experiment of thermocline was completed by us in 1992. The inverse results by the sample iteration algorithm and DC algorithm agreed well with the data measuring by the CTD instrument. It is still an open question. Further discussion in the aspect of reliability is presented in this paper. Generally speaking, inverse errors are caused by: (1) the inverse algorithm itself, (2) signal processing for the stability of computation, and (3) the improper problem. The result of a model inverse experiment shows that the errors caused by the algorithm itself and signal processings are not so critical if the improper problem was not paying enough attention.
A DWBA-based representation of the extinction cross section of weakly scattering objects: Application to zooplankton
Authors: Chu Dezhang , Ye Zhen
Published: July 2002

Because of the weakly scattering nature of the marine organisms, the Distorted Wave Born Approximation (DWBA) has been successfully used in modeling the acoustic backscattering by zooplankton [Stanton et al., J. Acoust. Soc. Am. 94, 3463–3472 (1993); Wiebe et al., IEEE J. Ocean. Eng. (in press)]. However, in the cases where the scattering-induced attenuation is noticeable, the previously used DWBA-based solutions fail to predict the attenuation since they ignore the imaginary part of the scattering form function and result in a zero extinction cross section. In this paper, a revised DWBA-based approximation is presented to include the imaginary part of the scattering form function. In deriving the revised solution, phase compensation based on ray paths is used. The solutions are compared with the exact solutions, and the agreements between the approximate solution and the exact ones are reasonably good. The results from this study can be applied to bioacoustic applications where the attenuations due to scattering or/and multiple scattering by zooplankton are significant.
An in situ target strength model for Atlantic redfish
Authors: Gauthier Stephane , Rose George A.
Published: July 2002

An in situ target strength (TS) model for Atlantic redfish is proposed based on a series of acoustic-trawl experiments conducted at the outer edge of the Green and Grand Banks in Newfoundland waters (NAFO div. 3Ps) in July 1996 and January 1997. Acoustic data were collected using a SIMRAD EK500 echosounder with a hull-mounted 38-kHz split beam transducer and a deep-tow system with a 38-kHz dual beam transducer that can be towed down to 400-m depth. Bottom and midwater trawling sets were performed to account for fish species composition and length distributions. Study sites were selected on the basis of low variance in individual fish size and the absence of other fish species. The model tests the dependence of TS on diel migratory behavior, TS methodology (split and dual beam), distance from transducer, fish density and size, and the presence and relative abundance of zooplanktonic organisms (krill).
Quantifying intraspecies variation in acoustic backscatter models
Authors: Horne John K. , Jech J. Michael
Published: July 2002

Fisheries researches are increasing the use of frequency-, length-, and aspect-dependent backscatter models in population abundance estimates of fish and zooplankton. Model predictions are often based on measurements from a single or a limited number of organisms. The resulting model parameters are used to predict backscatter for organisms of any length in the population. At rather high frequencies (i.e., length/wavelength ratios of 1 to 20), choice of carrier frequency, swimbladder shape, and swimbladder aspect influence amplitudes of returned echoes. Morphological differences among individuals will therefore determine the variance observed in amplitudes of echo ensembles. To quantify variance in predicted backscatter within species as a function of carrier frequency, fish length, and swimbladder aspect, we combined data from digitized x rays with Kirchhoff ray-mode backscattering models of brook trout (Salvelinus fontinalis) and Atlantic code (Gadus morhua). Quantifying backscatter variances within and between species allow us to examine the applicability of multi-frequency data and the inverse approach to estimate fish length abundances. [Work supported by ONR.]
Musical instrument perception in cochlear implant listeners
Authors: Galvin John J. , Zeng Fan-Gang
Published: July 2002

To examine the degree to which the cochlear implant preserves acoustic cues for timbre perception, eight cochlear implant and three normal-hearing listeners participated in a closed-set musical instrument identification experiment. Eleven nonpercussive, single-note instrument samples including woodwinds, brass, and strings were selected from the MUMS Classical Sounds CDs and formed a six-token and a nine-token set condition. The stimuli were normalized to have the same duration and RMS amplitude, and edited to include either the natural attack or the steady portion only. Subjects were trained with trial-by-trial feedback until asymptotic performance was achieved on one pitch (a4) and were tested without feedback on another pitch (c4). In the six-instrument task, both normal and implant listeners scored an averaged 70%–80% correct identification performance for both the natural attack and steady-state conditions. In the nine-instrument task, the implant listeners scored 20%–30% lower than the normal control. These results indicate that in a relatively simple six-instrument task, the cochlear implant can provide sufficient cues to support normal-level timbre perception, whereas the distorted spectral transformation via the cochlear implant fails to support a normal-level timbre perception, as the task complexity is increased to require more spectral resolution in the nine-instrument task.
The subjective evaluation of resonating sound-art samples and its relation to psychoacoustic measures
Authors: Cabrera Densil A.
Published: July 2002

A genre of sound-based art is identified, wherein the artist simply records the sound of a continuously resonating acoustic system, with a minimum of intervention in the process. The sound of such works is often close to steady state, and tends to evolve slowly. The sounds include nearly pure tones, tone combinations (sometimes with prominent beats), and sustained noiselike sounds. Fluctuations due to variations in the energy source (often the wind) also occur. It was thought that the abstract nature and simplicity of these sounds would lead to subjective evaluations based largely on fundamental psychoacoustic criteria. Fifty-three samples, of 20 s duration, were arbitrarily selected from the genre, including works by Alvin Lucier, Gordon Monahan, and Roger Winfield. Subjects rated these stimuli on five continuous bipolar scales: (dis)like, (un)interesting, (un)pleasant, emotional arousal, and emotional valence. The stimuli were measured for loudness, pitch characteristics, roughness, fluctuation, and lateralization. Analysis showed emotional arousal to be the strongest response, with significant correlations to loudness, roughness, and pitch. The results point towards the possibility of constructing a perceptual model of this type of minimalist art form. [Work supported by an Australian Postgraduate Award.]
The dependence of timbre perception on the acoustics of the listening environment
Authors: Jeong Dae-Up , Fricke Fergus R.
Published: July 2002

The acoustic quality of a room for music cannot easily be determined. As timbre is important in music it is possible that the perceived change in timbral quality of a sound in two spaces may give the basis for a measure of acoustic quality. The smallest perceivable change in the timbre of steady-state stimuli was measured in different listening environments through two experiments featuring a spectral centroid and rise time, respectively. Five component harmonic stimuli at 440 Hz were employed. The centroid of the standard stimuli was fixed at 2.95, in which the median amplitude of each component of the standard was set at 0.5, while those of comparison stimuli were varied from 2.93 to 2.41 in steps of 0.02 with a negative spectral tilt. The smallest perceivable change in the rise time was also measured using complex tones containing ten harmonics of 200 Hz (F0) with linear spectral slopes of −6 dB/oct. Rise times of comparison stimuli were varied from 5 to 25 ms in 2-ms steps, while the fall time was fixed at 5 ms across the stimuli. Results are presented and comments are made on how the acoustics of the listening environment influences the perception of timbre.
Noise prediction and control for new Norwegian high-speed trains
Authors: Ringheim Matias
Published: July 2002

The prediction of future noise levels is an important part of the planning process for high-speed trains and tracks. The first Norwegian high-speed tracks will be opened in 1998, using new 200-km/h electric trains based on the Swedish X2000. Strict noise criteria have been defined and extensive noise control measures are necessary both on the train itself and along the track. The noise prediction was performed several years ago, with the early and fairly simple Nordic prediction method. In the final planning stages some of the more critical results were checked against the revised Nordic method. The method enables the calculation of outdoor energy equivalent levels and maximum levels in octave bands, in simple and complex terrain. The first version of a computer implementation is available. The outdoor results have a form which is suitable for the further calculation of indoor levels, when the building properties are known. The basic aspects of the method, including a summary of available high-speed data, will be presented. Problems related to the prediction and reduction of future noise from new high-speed trains will be summarized.
Limits to limits?
Authors: Kihlman Tor , Kropp Wolfgang
Published: July 2002

Today, traffic noise due to cars, trains, and airplanes is the main noise source in urban areas. In accordance with the European Commission’s Green paper on Future Noise Policy, 22% of the European population are exposed to outdoor A-weighted noise levels higher than 65 dB and more than 45% are exposed to levels between 55 and 65 dB. This corresponds in total to about 250 million people. To improve the situation is a tremendous challenge and the question arises as to whether a good environment be provided (i.e., levels below 55 dB) for all people in today’s cities. Can the demands of 55 dBs only be fulfilled by structuring traffic in a smart way and using noise barriers? Or is a clear change in traffic policy needed from individual traffic to public transport? Different cities with different structures and automobile dependencies are compared in a general study based on statistical data. Detailed information about traffic flow, population structure, and land use is analyzed to verify these results.
Criteria and control for environmental noise emitted from motor vehicles
Authors: Wentang Ren
Published: July 2002

The present work investigated the environmental noise in a city from energy distribution and annoyance, and showed that the noise from different kinds of in-use vehicles is the main cause of noise pollution, especially in a city in a developing country. The technology and measures of noise control for in-use vehicles are urgently needed. According to measurement results of noise emission from 1000 vehicles based on ISO 5130, the statistical distribution parameters of stationary noise emission for six types of new vehicles and in-use vehicles are obtained. The statistical parameters show that the technology and measures of noise control for exhaust systems of in-use vehicles are key points. Some technological advances and noise-control measures have been proposed and practiced in China. A measurement procedure and system for vehicles in stationary operation is developed to distinguish some noisy vehicles with lost efficacy of a muffler. Regulations concerning stationary noise limits have been published and followed in China subsequent to the investigation. Reasonable design parameters of exhaust systems for different kinds of vehicles are proposed.