bluuebunny/crossref_metadata_2025 huggingface dataset:
Articulation class data: Early returns
Authors: Herbert R. Kring
Published: July 2002

Articulation class (AC) is a single number metric approved by ASTM Committee E-33.02 to characterize the performance of components used in open office environments to provide a degree of acoustical privacy between workstations. The AC values are derived from standardized acoustical laboratory tests using ASTM Standard E-1110. Standard test methods have been developed for ceiling systems (E-1111), furniture panels employed as acoustical barriers (E-1375), and wall finishes and furniture panels in the flanking position (E-1376). Test data are becoming available based on ASTM E-1111 for ceiling assemblies. These data are reviewed for different types of ceiling boards and the merits of the test method are examined with these new data in hand.
Atmospheric propagation transfer function determination using an adaptive filter
Authors: Benson Jonathan W.
Published: July 2002

In this Letter an alternative method for the experimental determination of the complex acoustic propagation transfer function is presented. The method uses an adaptive filter in system identification mode. The inputs to the system are the source and received signals. The transfer function is represented by finite impulse response filter coefficients. Good results were obtained using filter lengths in the range from 100 to 250 with a sampling rate of 12 k samples/s. The method is outlined and some representative results with experimental field data are given.
Analysis of acoustic propagation in the region of a shelfbreak front
Authors: Sperry Brian J. , Lynch James F. , Chiu Ching-Sang
Published: July 2002

The 1996-97 Shelfbreak Primer Experiments, which involved extensive oceanographic and acoustic measurements, have provided a large dataset with which to investigate the complexities of acoustic propagation in a shelfbreak front region. This paper looks in detail at a subset of the acoustic transmissions extending over a 12-day period during the summer 1996 experiment. Acoustic propagation near the continental shelfbreak is affected by numerous aspects of the oceanography, including but not limited to variable bathymetry, the shelfbreak front, an energetic soliton field, and interactions with occasional Gulf Stream filaments. Because of strong internal wave-induced coupling between the acoustic modes, changes in the large-scale oceanography, such as movement of the front, are difficult to distinguish. The impact of the soliton field on the acoustics is investigated, particularly from the perspective of wanting to invert for the front and other mesoscale features in the presence of this noise. One measure of oceanographic interest is the horizontal wave-number spectrum for the shelfbreak region. The possibility of obtaining this oceanographic quantity from acoustic data is considered. [Work supported by ONR.]
Azimuthal coupling computations for transmission loss caused by shelf internal waves
Authors: Oba Roger M.
Published: July 2002

The amplitude of an acoustic field propagating through a stratified continental shelf water column in the presence of an internal wave packet is azimuthally dependent when referenced to the direction of propagation of the internal wave packet. Internal wave packets propagating across the continental shelf give rise to a highly directional wave-number spectrum of the continental shelf sound velocity field. FOR3D [D. Lee, G. Botseas, and W. L. Siegmann, J. Acoust. Soc. Am. 91, 3192–3202 (1992)], a three dimensional, one-way acoustic propagation model, has been modified to model internal waves in shallow environment on various computational platforms. It allows azimuthal coupling in the propagation, so that horizontal variation of the field may be observed. Results of numerical solutions are presented for propagation through synthesized internal wave packets [D. Tielburger, S. Finette, and S. Wolf, J. Acoust. Soc. Am. 101, 789–808 (1997)] in order to demonstrate the dependence of properties of the acoustic field as a function of range and bearing from the source and internal wave packet. These will also be compared to models that do not take into account azimuthal coupling. [Work supported by the Office of Naval Research.]
Coupled mode propagation in the presence of internal waves
Authors: Abawi Ahmad T. , Kuperman W. A.
Published: July 2002

In a previous paper [J. Acoust. Soc. Am. 102, 233–238 (1997)] the effect of mode coupling due to bathymetric variations was studied by means of a new coupled mode parabolic equation model (CMPE). Instead of directly computing the total field, as is done using the conventional parabolic equation method, this model computes the modal coefficients as a function of range and obtains the total field by summing the local modes times the modal coefficients. In the present work, CMPE is used to study mode coupling due to internal waves in a shallow-water environment. The internal wave field is modeled and the spatial and temporal signal coherence across the array caused by interaction with the internal wave field is investigated.
Physical modeling of a trombone player’s lips
Authors: Ludwigsen Daniel O. , Strong William J.
Published: July 2002

The creation of a physical model is discussed in the context of the lips of a player/trombone system. The lip model is designed to incorporate the salient features of the physical structure of the lips, especially the geometry and material properties. A finite-element model is developed to approximate this structure, while the aerodynamic system is represented by flow equations solved with a finite difference scheme. To drive this model three pressures are applied. The mouth pressure is generated as a constant lung pressure delivered across an airway resistance; the pressure between the lips is dependent on the stream velocity, and the pressure in the mouthpiece is given by the convolution of the volume velocity with the impulse response of the trombone. Together these drive the oscillation of the finite element lip structure, which may be compared with that of previous models and experimental studies.
Software for thermoacoustic modeling
Authors: Muehleisen Ralph T.
Published: July 2002

In modeling thermoacoustic systems, many researchers rely on a freely available software package called DeltaE developed by Bill Ward and Greg Swift at Los Alamos National Lab. While DeltaE is an accurate and useful package, it is only available as a precompiled binary executable. As such, augmentation or modification of the code is impossible. In response to the limitations of DeltaE, a new, freely available software package has been developed. In contrast to the precompiled DeltaE, this new software has been developed as a set of MATLAB subroutines. While certainly not as fast as DeltaE, the MATLAB routines can easily be modified and augmented by researchers using a very wide variety of computing platforms. In addition, the MATLAB software has several new features including the use of complex frequency for determining resonance frequency and quality factors for resonators, and complete access to the spatial pressure, velocity, and temperature profiles throughout the system being modeled. An overview of the features and performance of this software package is presented. [This work was supported by the Office of Naval Research.]
Labio-coronal fricatives in Sengwato
Authors: Zsiga Elizabeth , Tlale One
Published: July 2002

This paper will present evidence for the existence of doubly articulated labio-coronal fricatives in Sengwato (a northern dialect of the Bantu language Setswana). The existence of stops and fricatives that incorporate all two-way combinations of labial, coronal, and dorsal articulations is predicted by phonological feature-geometry models [E. Sagey, MIT dissertation, 1986]. According to Ladefoged and Maddieson [Sounds of the World’s Languages (1996), p. 331], however, ‘‘the world’s languages do not use segments that combine two fricative elements.’’ Ladefoged and Maddieson analyzed reported labio-coronal fricatives in Sepedi, a sister language to Setswana, and concluded that the fricative articulations were sequenced. In this presentation, spectrographic analysis and video images from two speakers of Sengwato will be presented, demonstrating that in words like [o/sa] ‘‘to burn,’’ speakers do use two simultaneous fricative articulations. Spectrographic analysis shows a steady-state fricative, not a sequence; and comparison of video images shows that the labial constriction is more extreme than the addition of approximantlike rounding. The data to be presented here will show that, in contrast to Sepedi, Sengwato [o/s] is a true doubly articulated fricative. This type of sound is indeed represented in the repertoire of human languages.
The relationship between final alveolar stops and /ai/ offsets in American English
Authors: Thomas Erik R.
Published: July 2002

Two procedures were conducted to determine the relationship between final /t/ and /d/ and the realization of preceding /ai/ offsets. First, productions of /ai/ offsets in minimal pairs such as tide/tight were measured for Anglo sixth-graders and high schoolers from central Ohio, who speak a ‘‘General American’’ dialect, and for Mexican-American junior college students from Laredo, Texas, whose dialect is influenced by Spanish. Both groups tended to produce lower F1 and higher F2 before /t/ than before /d/, though the difference was smaller for the Texans than for the Ohioans, which is probably related to the impossibility of tautosyllabic combinations like /taid/ in Spanish. Second, a discrimination test was performed with similar subjects using stimuli representing a continuum of offset formant values, vowel duration, and duration of phonation into closure from most tide-like to most tight-like. Results showed that offset quality and vowel duration influenced discrimination of /t/ and /d/ by both groups of subjects, though somewhat differentially. The findings reveal that the offset difference exhibits dialectal variation and thus is not simply an artifact of articulatory constraints, and that listeners can access it to differentiate final /t/ and /d/.
Use of target characteristics for classification
Authors: Baer Ralph N. , Gaumond Charles F.
Published: July 2002

Scattering from ribbed cylinders exhibits very significant angular dependence. This angular dependence must be accommodated by any active classifier. A numerical technique for incorporating this dependence was previously reported [Charles F. Gaumond, J. Acoust. Soc. Am. 101, 3130 (1997)]. Using a data set simulating both targets and false targets in a shallow water environment, it is demonstrated that the method can be used as a component of an active classifier and produces an improved probability of detection over energy detection. The technique is based upon physics-based wave packets derived from the backscattered signal of a numerical scattering model. There is only one wave packet, originating from the so-called chalice waves, for the particular frequency band in the data set. These wave packets from a numerical model are then used to obtain features from the experimental data. A probabilistic method is then used to combine the features. The resulting performance is determined through the use of ROC curves. [Work supported by ONR.]
A comparison of tonal signal extraction methods
Authors: Jones Michael G.
Published: July 2002

The measurement of acoustic pressure signals in the presence of masking noise, often generated by mean flow, is a continual problem in the field of passive liner duct acoustics research. When performing acoustic liner tests in a flow duct facility, the researcher must balance two criteria. The most obvious is to design the acoustic liner such that the maximum amount of sound absorption is achieved. The other is to obtain a signal-to-noise ratio high enough for quality measurements. For grazing incidence impedance tests, these two criteria are contradictory. As the liner absorptive capacity is increased, the signal-to-noise ratio at the liner trailing edge is decreased. For this reason, measurement methods are needed that are capable of accurately extracting the portion of the measured acoustic pressure which is due to the sound source, even when the desired signal is buried beneath the broadband background noise generated by the presence of mean flow. The results to be presented provide a comparison study of three signal extraction methods for acquiring quality acoustic pressure measurements in the presence of broadband noise (to simulate effects of mean flow). The performance of each method was compared to a baseline measurement of a pure tone acoustic pressure 3 dB above a uniform, broadband noise background.
Detection of buried objects: Tank experiments
Authors: Sessarego Jean P. , Sageloli Jean
Published: July 2002

Detection and identification of buried objects in sediments is a wide problem which is far from being solved due to the complexity of the different situations encountered in real life applications (surface roughness, multiple reflections between object and water-sediment interface, complex nature and shape of the target, complex nature of the surrounding medium, porosity, bubbles). In these conditions, it seems hopeless to develop a general method capable of handling all these different situations. One issue for this problem is to resort to tank experiments and perfectly controlled situations. The aim of this paper is to give some answers to questions which frequently arise in detection problems of buried objects and also to show the limit of the assumptions which are made by most people working in this field. In particular, comments on the influence of the elastic behavior of the surrounding medium on the scattered field will be given; moreover, in the case of a simple shaped object, the shift in the position of resonances which is experimentally observed will be discussed. Finally, an experimental study of the influence of surface roughness will be given in order to show the importance of this effect on target detection.
Investigation of the near field of a loudspeaker using tomographic reconstruction from TV-holography measurements
Authors: Rustad Rolf , Morset Lars Henrik
Published: July 2002

It has previously been shown that a three-dimensional mapping of an acoustic field’s amplitude and phase may be calculated from a set of TV-holography measurements by use of tomographic techniques. In this paper a thorough mathematical description of this measuring technique is given. An increased number of measured projections improves the tomographic reconstructions significantly. Techniques for obtaining quantitative data for the pressure amplitude of the acoustic field are implemented. The technique is demonstrated by measurements of the near field of a loudspeaker and these measurements are shown to agree well with measurements obtained with a microphone.
Linear and nonlinear model of the human middle ear
Authors: Pascal Jérôme , Bourgeade Antoine , Lagier Michel , Legros Claude
Published: July 2002

The measurement of the middle ear transfer function usually requires invasive methods. An equivalent analog equivalent model enables us to evaluate its characteristics without damaging any part of the ear. A linear and a nonlinear model of the middle ear have been developed to predict intracochlear pressure and the stapes volume velocity for various sound pressure levels (SPL). The linear model results have been compared with human eardrum impedance and middle ear transfer function data. The nonlinear phenomena due to the contraction of the stapedius muscle over 80 dB and to the stapes clipping displacement above 120 dB are represented by a set of variable electrical components. The model of the acoustic reflex is based on experimental observations. The study of the annular ligament behavior was performed on cats and extrapolated to humans with some hypothetical restrictions. These approximations provide information on the middle ear transfer function and enable us to better understand the nonlinear middle ear mechanisms in an intense acoustic field.
Do click-evoked otoacoustic emissions have frequency specificity?
Authors: Ueda Hiromi
Published: July 2002

Whether click-evoked otoacoustic emissions (CEOAEs) have frequency specificity is an issue still subject to debate. In order to resolve this issue, changes in the frequency components of the CEOAE power spectrum, together with changes in compound action potential (CAP) thresholds before and after pure-tone exposure in guinea pigs, were examined. Changes in CAP thresholds immediately before and 1 h after exposure were compared with changes in the frequency components in the CEOAE power spectrum before and 1 h after exposure. The ILO 88 was used for measurement of CEOAEs. Total echo energy in the CEOAE power spectrum was converted into frequency bands of 1000 Hz. Shifts in filtered echo power (FEP) levels correlated maximally with those in CAP thresholds at 0.5 kHz above the same frequency. Stepwise regression indicated that only one step could be entered in a linear regression model using the variable of CAP threshold shifts at 0.5 kHz above the same frequency for all FEP shifts except FEP4.5. The remaining variables played a negligible role, since variance no longer changed when they were included in the regression equation. From these results, it was concluded that CEOAEs display frequency specificity. Influence on CEOAEs from higher frequencies is negligible.
On the horizontal structure of a field in separate modes radiated by a parametric antenna in axially nonuniform acoustic waveguides
Authors: Gurbatov Sergei , Egorychev Sergei , Kurin Vasily , Pronchatov-Rubtsov Nikolai , Kustov Leonid
Published: July 2002

The results of laboratory experiments on propagation of low-frequency acoustic waves produced by a parametric antenna in a few-mode waveguide with a linear depth variation along propagation direction are described. Mode structure of the radiated field and the characteristics of eigenwaves forming an acoustic field in waveguides of different types, which model shelf areas of the world oceans, are obtained. The study of the horizontal structure of separate normal waves was carried out by allocation of mode pulses due to the intermode dispersion. Also, the revealing of mode contents of radiated field was carried out by Fourier analysis of the signal received by evenly moving along the propagation route acoustic probe. The different Doppler frequency shifts of eigenmodes allows the resolution of each normal mode. It is shown experimentally that the azimuth structure of separate modes is transformed in the process of sound propagation to an area of smaller waveguide depths. For a particular mode, the direction at which mode radiation reaches a maximum value changes due to decreases in a waveguide depth when the number of normal waves evidently decreases. Experimental data obtained are confirmed by the results of numerical simulations. [Work supported by RFBR Grant No. 98-02-16402 and INTAS-RFBR Grant No. 95-IN-RU-0723.]
Free vibration of a kinked cantilever with attached masses
Authors: Reddy B. S. , Simha K. R. Y. , Ghosal A.
Published: July 2002

In this paper free vibration characteristics of a centrally kinked cantilever beam of unit mass carrying masses at the kink (mk) and at the tip (mt) are analyzed. Frequency factors are presented for the first two modes for different combinations of mk,mt and the kink angle δ. A relationship of the form f(mk,mt,δ)=mk+mt(4+103 cos δ+23 cos2 δ)=const appears to give the same fundamental frequency for a given δ and different combinations of [mk,mt]. Mode shapes as well as bending moments at the support and at the kink are also discussed. The utility of a discrete beam model in understanding the free vibration characteristics is also highlighted.
A modal-type analysis of the interactions for submerged elastic structures with the surrounding heavy acoustic medium
Authors: Chen Pei-Tai
Published: July 2002

The work investigates submerged elastic structures interacting with the surrounding acoustic medium. The equation of motion under mono-frequency oscillations for the coupled structural/acoustic system is formulated where a symmetrical complex matrix represents the acoustic loading. A surface acoustic reciprocal principle verifies the matrix symmetry. Such symmetrical formulation allows the ratio of real part to imaginary part of the complex power exerted by external forces to become the division of two quadratic forms of the structural vibration velocity. Consideration of the stationarity of the ratio leads to a symmetric eigenvalue problem, in which the eigenvalue is related to the radiation efficiency of the coupled system. The corresponding eigenvector defines a mode, which is referred to as the coupled structural/acoustic radiation mode. Based on the set of coupled structural/acoustic radiation modes, the forced vibration of the submerged structure can be decomposed into a set of decoupled complex impedance equations. Each impedance equation describes the relationship between a modal external force and the responded velocity amplitude. Moreover, the radiated acoustic power due to each coupled radiation mode is one-half of the square of the external modal force multiplying an effective modal admittance. The effective admittance depends on the structural properties, acoustic loading characteristics, and the exciting frequency. Furthermore, the effective modal admittance is applied to analyze resonant phenomena of submerged elastic structures. Spherical and spheroidal shells are selected to demonstrate the physical meanings of the modal-type analysis proposed herein, and the various aspects of resonant phenomena of submerged structures.
Physics of drop formation
Authors: Eggers Jens
Published: July 2002

A wide variety of technologically relevant processes, like ink-jet printing, spray painting, or internal combustion, depends on a detailed understanding of the underlying mechanism of drop formation. The motion is driven by surface tension, which tries to minimize surface area, thus reducing the minimum radius of a fluid jet to zero in finite time. This singular motion is self-similar as a function of time, and independent of fluid parameters or of initial conditions. The theory is confirmed by experiment without adjustable parameters.
Radiation pressure of sound on moving vortices
Authors: Semenov Andrew G. , Alexeyev Vadim N. , Rybak Samuel A.
Published: July 2002

This report is devoted to the nonlinear acoustic pressure of sound waves propagating in the vicinity of a rather general class of localized flows induced by the motion of spherically symmetric structures of the type of vortices in the liquid, say, ocean environment. As a result, the mean force exerted on a vortex is considered. The conventional general expression for transport cross section derived in a nonlinear theory of interaction of sound with rigid particles is proven to be incorrect for the vortex–sound interaction case. For the specific case of Hill’s vortex mean force, it is shown to be absent both in the traveling and standing sound wave fields. However, the force could be observable if the distribution of mean sound energy in the incident sound field in the limit of vortex dimensions could be characterized by nonzero spatial gradient. A generalized expression for mean force exerted on a localized vortex structure is derived.
Modal filtering for flexible beams using optical fibers
Authors: Semba Hiromasa , Tanaka Nobuo
Published: July 2002

This paper describes a vibration-mode filtering method for one-dimensional structures such as a cantilevered beam using a two-mode optical fiber as a distributed-effect sensor. One of the most important problems regarding the optical measurement is how to alter the sensor sensitivity spatially along the longitudinal direction of the beam when the sensor is mounted on the beam surface. In this study, spatial variation of the sensor orientation with respect to the longitudinal direction is included in the sensor model. The sensor sensitivity can be experimentally measured and used for design, incorporating the orthogonality of the mode shapes of the structure. Moreover, in light of practical considerations, a design procedure of optimal fiber placement utilizing bipolar weighting functions is presented. Finally, theoretical predictions are confirmed by experimental results and efficient vibration-mode filtering is demonstrated.
Empirical eigenfunctions obtained from high-speed imaging of the vocal folds
Authors: Berry David A. , Titze Ingo R. , Herzel Hanspeter
Published: July 2002

Previously, the method of empirical eigenfunctions has been used to interpret both periodic and aperiodic oscillations from a finite-element model of vocal fold vibration. For a typical case of periodic vibrations from the model, it was shown that two eigenfunctions explained 98% of the variance of the nodal trajectories. Furthermore, the extracted eigenfunctions were qualitatively similar to analytic normal modes computed from a linear continuum model. Even for complex aperiodic oscillations, 85% of the variance could be explained by just three eigenfunctions. The method of empirical eigenfunctions is now applied to quantitative observations of vocal fold movement obtained from excised canine larynx experiments. With the aid of a high-speed imaging system (the Kodak EktaPro 4540), both periodic and aperiodic oscillations were captured. The newly calculated eigenfunctions will be presented, and contrasted with those obtained previously from finite element simulations. Hints of low dimensionality and mechanisms of irregular oscillation will be discussed. [Work supported by NIH, Grant No. R29 DC03072.]
Periodotopic organization in the ICC of gerbils: A 2-deoxyglucose study
Authors: Langner Gerald , Braun S.
Published: July 2002

Periodicity is an important property of many acoustic signals. In the central inferior colliculus (ICC) of the auditory brainstem pathway, frequency and periodicity information converge on a tonotopically organized network. Electrophysiological investigations demonstrate a marked degradation of temporal information in the ICC pertaining to the envelope of spectrally complex signals relative to that observed at the level of the auditory periphery. The temporal information appears to be transformed into a rate-place code and is represented topographically in an orientation orthogonal to the spectral frequency (tonotopic) axis. Additional evidence for orthogonal orientation of frequency and periodicity is derived from a magnetoencephalographic (MEG) study of human auditory cortex and from optical recordings in cat auditory cortex. 2-deoxyglucose labeling was used to investigate the topographic organization of frequency and periodicity information in the ICC of the Mongolian gerbil. The results of this study provide additional evidence for such topographic orthogonality, as well as for convergent information flow, suggesting that neurons in the ICC project to a specific subpopulation of cells in the low-frequency area of the auditory cortex that integrate information across separate periodotopically organized frequency bands.
Robust matched-field processing in underwater acoustics
Authors: Booth Newell O.
Published: July 2002

During the last decade, underwater acoustic matched-field processing (MFP) has been shown to be a robust and powerful means of extracting information related to the propagation of sound and the location of acoustic sources in the ocean. Using large arrays of acoustic receivers, broadband sources of acoustic energy, and physically accurate propagation models, MFP techniques have been used to detect, localize, and track acoustic sources. It is also possible to estimate the array shape as well as oceanographic parameters which affect acoustic propagation. Using a broad definition of matched-field processing, this paper reviews its application to underwater acoustics and acoustical oceanography. Physical phenomena which contribute to the successful application of MFP are discussed, along with other phenomena which have contributed great simplifications.
Analysis of modal dispersion in the Middle Atlantic Bight
Authors: Laliberte John E. , Potty Gopu R. , Miller James H.
Published: July 2002

Ocean environmental acoustic experiments were conducted on the Middle Atlantic Bight during the August 1996 Shelf Break Primer Experiment. Broadband acoustic sources, SUS charges, were dropped across and along the shelf in depths ranging from 85 to 350 m. The experimental data were collected at two veritical hydrophone arrays situated at the top of the shelf. The acoustic signal received was analyzed using a Morlet wavelet. This wavelet analysis enabled time and frequency characteristics to be extracted. Scalograms, representations of the energy distribution in the time-frequency plane, were used to assess the modal dispersion. The group speeds for modes 1–4 at frequencies 15–240 Hz were estimated using the wavelet scalogram. The mode dispersion was dependent upon the bathymetry, depth, and range features of the shelf. A normal mode code was used to compare the observed dispersions with theory. In addition, the influence of the bathymetry, depth, and range features were analyzed for their impact on the modal dispersion. [Work supported by ONR.]
Characterizations of the internal waves and their effects on sound propagation in the central area of the Yellow Sea
Authors: Yan Jin , Zhang Renhe , Sun Zhenge
Published: July 2002

In the late summer of 1996, a joint China–USA experiment was performed in the central area of the Yellow Sea. The analysis of the data from thermistor string and CTD reveals that (1) there was intense internal wave activity in the experimental area, and the isotherm displacement induced by internal waves could be as large as 8 m; (2) the power spectrum of the vertical displacement had a significant peak near the M2 tide frequency, and was approximately proportional to ω−3/2; and (3) the internal wave field was dominated by first-order modes. Based on the observed properties of the internal waves, a model of the induced sound-speed distribution is developed, and computer simulations are conducted for cw and wideband signal propagation by using the PE method. Numerical results are presented for comparison with the experimental data. [Work supported by NNSF of China and ONR of USA.]
Sound vertical coherence in shallow water with a thermocline
Authors: Zhang Renhe , Li Fenghua
Published: July 2002

A China–U.S. cooperative experiment was conducted in the Far Yellow Sea with a thermocline in August 1996. The explosive sources were discharged either above the thermocline or below the thermocline. The pulsed signals were received by a vertical array spanning the whole water column, and the shortest separation between two hydrophones is 2 meters. The vertical correlation of the received data is analyzed in this paper. Experimental data show that vertical coherence has different depth structure for different source, frequency, and range, and it is also shown that the relationships between the coherence and the frequency and between the coherence and the range are different for different source and receiver. It is found in the experimental data that the vertical coherence is not reciprocal. Numerical results and theoretical explanations of these relationships are also given in this paper. [Work supported by NSF of China and ONR of the U.S.]
Active control of acoustic and structural intensities of a submerged elastic plate
Authors: Fischer Matthias , Hayek Sabih I.
Published: July 2002

In this paper, the active control of active structural intensity (SI) and the resultant radiated active acoustic intensity (AI) in a coupled structure-fluid system is explored. The system consists of an infinite elastic plate submerged in an infinite heavy acoustic medium. The plate is excited to vibration by mechanical noise sources, which generate a vector-active SI field in the plate and a vector AI field in the coupled acoustic medium. Due to heavy fluid loading, the flexural waves in the plate are strongly coupled to the acoustic waves. A line-force and line-moment actuators, which are located at arbitrary locations on the plate, are used for control. The mechanical noise source and control actuators interact not only by their mutual flexural impedance through the elastic plate, they also interact through an acoustic path as well. The control algorithm is aimed at minimizing both SI and AI. The cost function to be minimized consists of a weighted sum of the SI and AI in the far field of the mechanical source region. The influence of the location of these controllers relative to the source region and the relative weighting given to SI versus AI in the cost function is explored.
Direct adaptive predictive control using gradient descent
Authors: Eure Kenneth , Juang Jer-Nan , Silcox Richard
Published: July 2002

Predictive control has been successfully used for the regulation of plate vibrations. Past implementations of predictive control have included both feedforward and feedback algorithms. These algorithms may be used as a nonadaptive or an adaptive control method as long as conditional updating is employed or a sufficient level of dither is added to the control signals in order to maintain input and output data coherence for system identification. For large-order systems with many input and outputs, the adaptation rate is severely limited due to the computational burden. The direct adaptive controller presented in this paper uses a gradient descent method to directly determine the predictive control parameters for the feedback regulator. The key features of this control scheme include the use of leakage to prevent drifting of the identified parameters in the presence of closed loop data. The initial information needed by the control scheme is an estimate of the plant order and an estimate of the plant pulse response from input/output data. Because this scheme is adaptive, the controller poses robustness against errors in the estimate of the plant’s pulse response which allows the time-varying characteristics of the plant to be regulated.
Assessing and optimizing the acoustical parameters of concert halls for Korean traditional music
Authors: Park Kyoungsoo , Sung Koeng-Mo , Choi Yeongha
Published: July 2002

The western music has been studied for many decades in acoustical viewpoint. Many objective parameters are developed for the purpose of assessing the concert halls and optimal values of them were studied. Oriental music, however, and musics of the other cultures have not been studied well yet and neither is Korean traditional music. Although Korean traditional music is somewhat different from western music in sense of the structure of instruments, the style, and the concert halls, something making common people feel the music to be beautiful may have many factors in common. In this paper, a few acoustical parameters of Korean concert halls have been studied by that assumption. Many parameters of traditional concert halls and modern concert halls for Korean traditional music have been measured. The halls were modeled for computer simulation and then varied to find optimal conditions of the halls for Korean traditional music by listening to artificially generated live music in the simulated virtual halls. The method of assessing and finding the optimal condition proposed in this paper may be applied to the other cultural music, too.
Noise reduction algorithms for digital hearing instruments
Authors: Hamacher Volkmar , Holube Inga
Published: July 2002

One of the main problems for hearing instrument users is the reduction of speech intelligibility in noisy and/or reverberant environment. To compensate for this disadvantage, noise reduction algorithms preceding or integrated in the hearing instruments’ signal processing are required. New generations of powerful digital hearing instruments enable the implementation of sophisticated algorithms, which have been partly applied in other communication devices. These algorithms offered promising benefit in previous laboratory studies with hearing instrument users. This paper presents a survey of noise reduction strategies implemented in current hearing instruments and new algorithms applicable in future devices will be given. The algorithms can be divided into different classes concerning their approach in noise reduction. One class of algorithms uses the signal from one microphone and reduces the noise by analysis of the signal characteristics. Another class of noise reduction techniques uses several microphones and exploits spatial information about the sound field to improve the signal-to-noise ratio. Restrictions for the different algorithms are the computational effort and the preconditions to the interfering noise field. The expected benefit for hearing instrument users in typical everyday life hearing situations will be discussed.
Single-bubble sonoluminescence in water during transitions from hypergravity to low gravity on NASA’s KC-135 aircraft and laser-beam extinction methods for studying bubble dynamics
Authors: Thiessen David B. , Young Jeremy E. , Marr-Lyon Mark J. , Dzikowicz Ben R. , Marston Philip L.
Published: July 2002

The sound field which drives SBSL also provides the radiation force which counteracts the average buoyancy of the bubble. One consequence is that the location of the bubble should be altered by the effective acceleration of gravity ge. Variations in ge may alter the physical processes giving rise to luminescence. This group’s previous experiments have confirmed that SBSL is not automatically quenched in the reduced and enhanced ge conditions in an aircraft undergoing parabolic flight trajectories [D. B. Thiessen et al., in Proc. of the 4th Microgravity Fluid Phys. Conf. (NASA, 1998), pp. 379–383]. The new experiments were carried out with the SBSL chamber in contact with a constant-pressure gas-filled chamber. During intervals of negligible drift in the SBSL intensity, there can be a rapid intensity rise (with a relaxation time of about 5 s) of about 4% as ge is decreased from 1.8 to near 0 g, but the increase is not seen in all data sets. In related work, diagnostics based on monitoring laser-beam extinction with a photocell [J. S. Stroud and P. L. Marston, J. Acoust. Soc. Am. 94, 2788–2792 (1993)] is applied to SBSL bubbles in the laboratory. [Work supported by NASA.]
An approach to calculating spatial impulse response of curved transducers: Linear arrays with cylindrically curved surfaces
Authors: Wu Ping , Stepinski Tadeusz
Published: July 2002

The spatial impulse response method (SIRM) is a powerful tool to calculate transient fields that has been applied extensively to planar sources with both uniform and nonuniform excitations as well as to spherically and axisymmetrically curved transducers. Yet, it seems that the SIRM has not found application to other curved transducers, like linear arrays with cylindrically curved, focusing surfaces, which are commonly used in nondestructive testing and medical imaging. This paper is intended to propose an approach for the calculation of the spatial impulse response of such linear arrays. The approach starts from a general form of the expression for spatial impulse response, which is a double surface integral, and finally gives a single integral after coordinate transformation. The single integral is numerically calculated. The approach is generally applicable. Spatial impulse responses of a linear array with a cylindrically concave surface are presented, and analyzed in comparison with that of the corresponding linear array with planar surface.
Fiber-tip sensors for ultrasonic measurement
Authors: Koch Christian , Wilkens Volker , Molkenstruck Walter
Published: July 2002

Modern trends in the application of ultrasound, such as the increasing use of high-frequency fields and high power pulses, constantly increase the demands for resolution and robustness of ultrasonic sensors. An alternative to customary measurement techniques consists of using the tips of optical fibers as sensor elements. Because of the small outer diameter of an optical fiber and the optical principle of measurement, fiber-tip sensors combine high spatial resolution with wide bandwidth; in addition, they are robust components. After classification of the kinds of fiber-tip sensors, a brief introduction to the principle of operation of displacement and pressure detection is given. The acoustic properties of the sensors are discussed on the basis of transfer functions obtained by calibration measurements up to 50 MHz. Shock-wave detection is the usual application of fiber-tip sensors, and experimental results of an investigation of an electromagnetic lithotripter are presented. If the fiber tip is, however, covered with dielectric coatings, the detection of ultrasound generated by focused piston transducers is possible, and this technique opens up new fields of application for fiber-optic sensing.
Thermoacoustic testing on thermal protection systems
Authors: Bayerdörfer Gerhard
Published: July 2002

The IABG has designed and built a thermoacoustic facility capable of producing surface temperatures up to 1300°C at sound pressure levels up to 160 dB. The purpose of this facility is to simulate aerothermal environments as encountered during the mission of space planes. The thermal protection systems (TPSs) of space planes are very susceptible to fatigue under these environments and therefore need extensive qualification testing before being used in operational missions. After reviewing the design aspects of the facility with a description of the selected components, a number of typical applications are presented such as tests in a progressive wave tube as well as tests in a reverberation chamber. In both cases difficulties arise in measuring the dynamic pressures acting on the test specimens under the extreme thermal environment. The paper therefore includes a discussion of possible measuring techniques for temperature and vibration control.
Shock waves in reactive bubbly systems
Authors: Kedrinskii V. K.
Published: July 2002

Shock wave propagation in a reactive bubbly system results in the formation of a quasi-stationary self-sustaining wave regime which is known as a bubbly detonation wave [Hasegawa, Fujiwara, 1982]. This paper presents experimental and numerical results of the features of formation of the wave regime mentioned and includes (1) data on a shock wave/single bubble and shock/shock interactions, (2) an analysis of a bubbly cavitation role in initiating detonation of liquid High Explosives, and (3) analysis of the explosive processes arising when storage containers containing pressure-liquified gases or a combustible liquid are suddenly depressurized. The results of numerical analysis of bubbly detonation as a physical model of a hot-spot mechanism responsible for explosive processes in liquid media and the possibility of its application to the problem of acoustical analogies of laser systems are considered.
Nonlinear phenomena in resonator caused by finite displacement of vibrating piston
Authors: Rudenko Oleg V. , Shanin Andrey V.
Published: July 2002

Design of high-Q resonators demands reducing of all types of energy loss. When linear losses are eliminated, the nonlinear absorption due to shock-wave formation becomes significant. Such methods as using frequency-dependent reflecting boundaries (providing phase shifts between harmonics), using a selective absorbent for second harmonic, and design of resonators with complicated geometrical shape are known for damping of the shock formation process. The new type of nonlinear distortion of a wave profile is studied. This phenomenon appears in linear media and is caused by finite displacement of boundary. The magnitude of the effect depends on the ratio of two small parameters: Mach number and Q−1, and therefore, it can be significant even for small pumping. The effect of moving the boundary is accumulative in time and is of the same order as effect of volume nonlinearity. The temporal profiles of nonlinear vibrations at harmonic pumping are calculated. The optimum law of piston movement providing the maximum energy accumulation in a resonator is suggested. The nonstationary problem is solved. New mathematical models based on functional equations are proposed. This model has a discrete character and requires some specific approaches, unlike the models for volume nonlinearity. [Work supported by INTAS-RFBR European grant.]
Time constants of pitch processing arising from auditory filtering
Authors: Wiegrebe Lutz , Hirsch Hans S. , Patterson Roy D. , Fastl Hugo
Published: July 2002

This study uses rippled noise and ‘‘AABB’’ noise [Wiegrebe et al., J. Acoust. Soc. Am. 104, 2307–2313 (1998)] to investigate time constants associated with pitch processing in the auditory system. RN and AABB have identical long-term spectra and autocorrelations but they differ in their temporal dynamics. Previously, it was shown that, when the pitch of the stimuli is below about 350 Hz, listeners could discriminate broadband AABB from RN based on a pitch-strength difference. Here, the effect of frequency passband on the RN-AABB discrimination was investigated. In each 1-kHz band, discrimination performance decreased with decreasing delay (32–4 ms). As the center frequency increased from 0.5 to 4 kHz, the rate of decrease became smaller such that discrimination was still significant in the highest band with the shortest delay. Further experiments suggest that the RN-AABB discrimination and its frequency effects are based on pitch-strength differences. Auditory simulations suggest that integration of pitch information occurs in two stages comprising a short, frequency-dependent time constant of auditory filtering and a long, yet undetermined neural time constant separated by a nonlinear transformation, i.e., half-wave rectification. [Supported by the Medical Research Council, the ‘‘Prof. Dr. Ing. Erich Mueller-Stiftung’’ and the ‘‘Deutsche Forschungsgemeinschaft.’’]
Perceptual consequences of spectro-temporal smearing in the wavelet coding of speech
Authors: van Schijndel Nicolle H. , Houtgast Tammo , Festen Joost M.
Published: July 2002

In this study, speech is spectro-temporally smeared, i.e., the contrasts in the spectral and/or temporal domain are reduced. This spread-of-excitation type of manipulation is embedded in a spectro-temporal analysis and resynthesis scheme. In order to perform a perceptually relevant analysis, wavelet coding with a Gaussian wavelet of 1/4 octave is used. The detectability of smearing and the effect on intelligibility are measured for normal-hearing and hearing-impaired listeners. Smearing is imposed concentrating on the spectral domain (related to upward and downward spread of masking), concentrating on the temporal domain (related to forward and backward masking), and considering the spectral and temporal domain in combination (spectro-temporal spread of excitation). Mechanisms underlying the just-noticeable degree of smearing, and the intelligibility of smeared speech will be addressed. The results may provide insight into the sharpness of the internal spectro-temporal representation of the auditory system and its effect on speech intelligibility. Comparing normal-hearing and hearing-impaired listeners, the role of a reduced sharpness in auditory spectro-temporal coding as a possible explanation for degraded speech intelligibility will be discussed. [Work supported by the Netherlands Organization for Scientific Research (NWO).]