bluuebunny/crossref_metadata_2025 huggingface dataset:
Design criteria for acoustical excellence of auditoriums
Authors: Veneklasen Paul S.
Published: October 2005

Based on a 25-year series of highly successful auditoriums, for which the designs drew upon a long background of musical participation and acoustical laboratory research, a summary of guidelines and quantitative achievement criteria is presented. In this paper acoustical factors are extracted from total functional requirements while recognizing that there is extensive interplay. Features are concerned with performers as well as audience. The role of laboratory modeling is stressed. The guidance role of auditorium synthesis over the years is also stressed. Adequate full-scale verification is compared with current rating schemes.
Reduction of interaction in multichannel cochlear implants
Authors: Townshend Brent
Published: October 2005

The spread of current in multichannel implants results in excitation of largely identical neural populations regardless of which electrode is stimulated. This severely reduces the number of independent channels of information conveyed with monopolar or even bipolar stimulation. A method based on the thresholds of multiple electrode stimuli was developed to calculate accurately the mapping from electrode current levels to normalized current density at each neural site. For the implant patients tested, this technique accurately predicted thresholds for arbitrary patterns of stimulation. Inverting this mapping matrix produced patterns of stimulation that selectively stimulated only one neural site with a minimum of interaction, while satisfying current limit constraints. These sharpened stimuli were pitch ranked with greater consistency than either monopolar or bipolar stimuli. [Work supported by NIH.]
Psychophysical studies on prelingual patients using a multiple electrode cochlear implant
Authors: Tong Y. C. , Busby P. A. , Clark G. M.
Published: October 2005

Psychophysical studies were conducted on three prelingual patients during the first year of usage of a multiple electrode cochlear implant. The results were compared with those obtained from postlingual patients. For the identification of two electrode positions (6 mm apart), the d′ sensitivity index for prelinguals was <0.75 and for postlinguals > 3.0. For the identification of two electric repetition rates (an octave apart), d′ for prelinguals was <0.6 and >3.0 for postlinguals. Temporal resolution discrimination was also poorer for prelinguals, gap detection >64 ms and duration difference limens >38 ms from a fixed standard duration of 30 ms, while for postlinguals, <3 ms and <38 ms, respectively. The ability to count a variable number of short electrical stimuli deteriorated at high rates (>5/s) of presentation for prelinguals but not for postlinguals, while for visual and tactile stimuli performance was similar across all patients. However, improvements in one prelingual patient after one year of usage were recorded for electrode place and rate identification (d′ > 1.5).
Active control of structural vibration
Authors: Meirovitch Leonard
Published: October 2005

In general, structures represent distributed-parameter systems described by partial differential equations. Strictly speaking, vibration control in distributed structures requires distributed sensors and actuators. Practical considerations demand that control be carried out by means of discrete components. Quite often they also demand that the structure be discretized in space. A discretization procedure having particular appeal is the finite element method, which has the advantage that the nodal (in the finite element sense) coordinates represent actual displacements of the structure. One of the most significant problems in feedback control is the generation of control gains. Techniques for computing gains in common use are the pole allocation method and optimal control. These methods work best for low-order systems. This tends to create a problem in structures, which generally demand high-order mathematical models. Feedback control requires determination of the system state, which can be done through measurement of the nodal displacements and velocities. If it is not feasible to measure all the components of the state, then it is possible to construct a dynamical system, related to the actual system and known as a Luenberger observer, to estimate the full state. One method of controlling the vibration of a structure is modal control, which implies controlling the modes of vibration of the structure. In the independent modal-space control method, design of the control can be carried out for each mode independently. This requires estimation of the modal states. A method not requiring estimation of the modal states is direct feedback control, in which the sensor signals are amplified directly to generate the feedback forces. Under given circumstances, direct feedback can be rendered nearly optimal.
Finite element treatment of exterior fluids in fluid-structure interaction problems
Authors: Everstine Gordon C.
Published: October 2005

Several finite element solution approaches are described for fluid-structure interaction problems involving an exterior fluid. The specific problems of interest are those of acoustic radiation and scattering from submerged elastic structures subjected, respectively, to internal time-harmonic mechanical loads or an incident time-harmonic wavetrain. These problems can be solved by combining a finite element model of the structure with a fluid loading computed using finite element, boundary element, infinite element, or decoupling techniques. Formulations are presented and compared for fluid domains modeled using an added mass matrix, the doubly asymptotic approximation (a decoupling technique), explicit fluid finite elements, and the Helmholtz exterior integral equation. With the exception of the integral equation treatment, all these fluid-loading approaches can be implemented using the standard finite element modeling capabilities available in structural analysis computer codes such as NASTRAN. The most accurate fluid treatment is obtained with the Helmholtz integral equation although this is at somewhat greater computational cost than that required using the less precise approaches.
Matrix quantization for very low data rate voice coding
Authors: Wong David Y. , Juang B. H. , Chen D. Y.
Published: October 2005

Matrix quantization extends the theory of vector quantization for voice coding to take advantage of the phonological and phonotactic properties of speech. The speech signal is first modeled by LPC spectra at 10-ms time intervals. By adopting an acoustically defined (and demisyllable like) automatic segmentation procedure, consecutive LPC spectra are grouped into LPC coefficient matrices. A distortion measure that consists of nonlinear time warping and a standard LPC distance metric is also developed for comparing the “likeliness” of two matrices. The matrix codebook is generated from a speech database using a simple mini-max procedure and the matrix distortion measure. A nearest-neighbor full search procedure is used during speech encoding. Data rates under 100 bit/s can be achieved for the LPC spectra. Results for a single speaker experiment based on the matrix quantization method and subsequent research on very similar techniques will be discussed.
Vector predictive quantization of the LPC spectral parameters for low-rate speech coding
Authors: Shoham Yair
Published: October 2005

Scalar quantization of the LPC parameters requires a high bit rate. Considerably lower rate can be obtained via vector quantization (VQ). However, complexity constraints dictate the use of suboptimal VQ. The use of vector predictive quantization (VPQ) for the LPC parameters is proposed. In VPQ, the suboptimality is compensated for by exploiting the temporal redundancy in the input. VPQ is a two-stage memory VQ. In the first stage, the input vector is predicted from quantized past vectors, using a set of vector coefficients, held in a predictor codebook. In the second stage, the predicted vector is combined with a residual vector to form the final output. A set of residual vectors is held in a residual codebook. VPQ was applied to the LPC parameters in the down-sampled, log-magnitude spectral domain. The idea was to design an efficient VPQ under the perceptually meaningful log-likelihood distortion measure, while circumventing the stability problem of the synthesis LPC filter. This VPQ was used in a 4.8 kbit/s CELP coder where only 1.0 kbit/s were allocated to the parameters. The performance was almost indistinguishable from that of a CELP coder with unquantized parameters. [Work supported by NSA.]
Integration of acoustics and architecture in the auditorium at the Metro Toronto Convention Center
Authors: Van den Broeck Ray
Published: October 2005

The new Metro Toronto Convention Center Hall is a one-balcony auditorium having a seating capacity of 1350. The space is designed as a stage house multipurpose auditorium. Excellent acoustical environments are achieved for functions such as: lectures, motion pictures, speech, and music drama and music recital. The paper describes how final architectural forms and materials of the stage and the house, seating configuration and type, as well as surface size, shaping, and orientation were influenced by row-to-row sightlines, distance between the audience and stage, eccentricity angle, vertical viewing angle, under balcony isolation, safety, circulation, and the acoustical requirements: clarity/intelligibility, balanced and uniform sound projection, cohesion for performers on stage, freedom of echoes, strong envelopmental sound, reverberant sound level, and decay rate.
Measurement of panel reflection using acoustical scale modeling techniques—Part I: Instrumentation and procedures
Authors: Ortega Jose C.
Published: October 2005

It has been recognized for some time that the size, shape, and orientation of reflecting panels used in enclosed spaces affect their reflecting characteristics. This paper describes the test chamber, instrumentation, and procedures that have been developed to measure reflecting characteristics of scale model panels.
New room acoustics measurement software
Authors: Bradley J. S. , Halliwell R. E.
Published: October 2005

Auditorium acoustics research has now developed to the point where there is quite general agreement on the subjective importance of four types of newer measures. These are: (1) decay times; (2) early/late ratios and other measures of clarity; (3) the overall strength or sound level; and (4) lateral energy fractions. In the past such measurements have been made by researchers using various complicated arrangements. The new software runs on an IBM PC compatible computer and controls a Norwegian Electronics two-channel analyzer, so that these newer auditorium acoustical measurements can be much more conveniently obtained. The design of the system and results by this and other methods will be discussed.
Effects of acoustic cavitation under diagnostically relevant conditions
Authors: Carstensen Edwin L.
Published: October 2005

Under appropriate conditions, ultrasound is able to produce profound biological effects through its action on microscopic gas bodies in tissues. Clear examples have been found in lower organisms. To determine what this means for mammals will require a better understanding of the basic physical processes and more information about the existence of appropriate gaseous nuclei in mammalian tissues. From the limited information available at the present time, it appears that ultrasound has two qualitatively different modes of action on these bubbles. (1) Continuous wave exposures excited repetitive oscillations of the bubbles and the restraining tissue structures. It appears that this causes intercellular streaming and stresses on the cytoplasmic membrane which may be great enough to cause rupture as well as sublytic effects. (2) Ultrasound applied in very short pulses and at low temporal average intensities produces effects which have the characteristics of transient cavitation. In this case, the gas bodies expand and collapse violently producing mechanical shocks and chemical products of the extremely high temperatures in the compressed phase of the transient cavity. Although it is essential that nuclei of appropriate size be present for transient events to occur, the phenomenon of resonance which is characteristic of stable cavitation is not evident with short isolated pulses. If there are effects of cavitation in mammalian tissues under the low temporal average intensity exposures used in diagnosis, it most probably will come from the latter mechanism. Up to the present time very little effort has been directed to the study of transient cavitation under conditions which may exist within the body.
Comparison of two single-channel vibrotactile aids for the hearing impaired
Authors: Weisenberger Janet M. , Russell Ann F.
Published: October 2005

Two commercially available single-channel vibrotactile aids for the heating impaired were compared in tasks using acoustic stimuli of varying levels of complexity. Both devices provide envelope information in an AM signal presented to a single location on the skin; however, one of the devices varies the carrier frequency according to input frequency, providing some additional “spectral” information about the stimulus. Subjects were tested in tasks including sound detection, environmental sound identification, syllable number and stress identification, and phoneme identification of limited-set vowels and consonants. All stimuli were recorded onto disk and presented through a loudspeaker by computer. Results showed rapid learning of tasks requiring only envelope information (environmental sounds, syllable number and stress), but little or no improvement with training in vowel and consonant identification. No significant differences between the devices were found on any task, suggesting that the additional spectral information provided by one of the devices is not effectively utilized by the tactile system in the absence of visual cues. [Work supported by NSF and NIH.]
Single-channel FFT analyzers
Authors: Brittain Frank H.
Published: October 2005

FFT analysis gives engineers powerful tools to diagnose and solve problems, and the power to get into trouble. As the sophistication and number of buttons increase, the difficulties in getting valid and useful results also increase. Fundamentals of single-channel FFT analyzers and their capabilities are discussed to help the user better understand the practical use of FFT analyzers. The concept of time and frequency domains is developed using an analog model. Assumptions implicit in using the finite Fourier transform to approximate the (infinite) Fourier transform are defined. Sampling rate, frequency range, number of lines, resolution, and sampling period are reviewed. Folding or aliasing and how to avoid it are illustrated; leakage and the use of windows to reduce errors are discussed. Various types of averaging are reviewed. A description is provided of how these fundamentals, inherent in all FFT analyzers, appear to the user of a single-channel analyzer. Provisions for mitigating errors built into most analyzers are outlined. The two basic outputs (frequency or auto spectra) and special output formats of typical single-channel analyzers are demonstrated.
First, a word from our sponsor
Authors: Hargrove Logan E.
Published: October 2005

The Office of Naval Research is pleased to have supported and to have been associated with Isadore Rudnick's unique research contributions in physical acoustics and wish him a happy 70th birthday.
Nonlinear acoustics of a two-dimensional plasma in He4
Authors: Putterman Seth , Denardo Bruce , Williams Gary A.
Published: October 2005

Balance between the repulsion of positive ions by a dielectric-vacuum interface and an externally imposed holding field facilitates the formation of a 2D plasma (net charge 108e/cm2) about 300 Å beneath the free surface of He4 [Ott-Rowland, Kotsubo, Theobald, and Williams, Phys. Rev. Lett. 49, 1708 (1982)]. Density modes of the charged sheet propagate at acoustic frequencies (10–100 kHz) and have a high adjustable reversible dispersion. The resonance frequencies were found to soften up to 30% at Mach numbers of 0.01. Continuum mechanics yields a good description of the linear dispersion law but to third order in amplitude theory predicts a frequency shift which is too small by a factor of 1000 and has the wrong sign. The huge nonlinearity makes this an ideal system to probe new solitons [Wu, Keolian, and Rudnick, Phys. Rev. Lett. 52, 1421 (1984)] and may provide a means of probing Wigner crystallization via the use of an end fire array to achieve mode conversion [Garrett, Adams, Putterman, and Rudnick, Phys. Rev. Lett. 41, 413 (1978)] of propagating 2D plasma oscillations to 2D shear modes.
Surface acoustic wave interaction with thin magnetic films
Authors: Levy Moises , Wiegert Roy
Published: October 2005

It has been found that surface acoustic waves (SAW) exhibit a very large interaction with appropriately prepared thin magnetic films through the magnetoelastic effect. For a 600 Å 90Ni 10Fe thin film, the interaction can produce changes in attenuation of 30 dB/cm at 700 MHz by changing from 2 to 12 G a magnetic field applied parallel to the film plane and perpendicular to the SAW. Measurements of the frequency dependence of this large effect yield values for the Gilbert damping constant and the anisotropy field. This interaction has been studied in the series of xNi (1 − x)Fe alloy films. For x > 80 wt %, the magnetoelastic constant η is negative. It is positive for x < 80 wt%. An amorphous film with positive η has also been studied. Some device concepts which make use of this effect will be presented. [Work supported by the National Science Foundation under Grant No. ESC 8519695.]
Method for controlled rotation in an acoustic single mode levitator
Authors: Allen J. L. , Barmatz M.
Published: October 2005

A method for producing controlled rotation of an acoustically levitated object in a single mode cylindrical levitator has been developed and tested experimentally. In this method, two spatially separated acoustic drivers are used to provide the levitation and rotation capabilities. The levitation sound fields can produce two types of acoustic torques: a stabilizing “Rayleigh” torque and a rotating torque [M. Barmatz, J. Acoust. Soc. Am. Suppl. 1 78, 44 (1985)]. For an appropriately chosen mode, an amplitude variation and/or phase shift introduced between the two drivers can be used to unbalance the positive or negative going angular waves leading to a net rotational torque on the sample. A finite minimum unbalance of the angular waves is required to overcome the “Rayleigh” torque and produce rotation. The dependence of this minimum on the phase shift, chamber length, sound-pressure level, and sample size will be discussed and a videotape of the rotation experiments will be presented. [Work supported by NASA.]
Resonant reciprocity calibration of conventional, magnetohydrodynamic, and quantumfluidic transducers
Authors: Garrett S. L.
Published: October 2005

Since its application to transducer calibration in 1940 by Cook and MacLean, the reciprocity method has been used for absolute calibration of electroacoustic transducers in a relatively limited number of geometries and media. Following Prof. Rudnick's article on extensions of this technique to unusual geometries [J. Acoust. Soc. Am. 63, 1923 (1978)], the resonant reciprocity technique to high-precision (noncompliant) microphone and hydrophone calibration in air and water, to magnetohydrodynamic (ultracompliant) transducers in salt water and mercury, and to thermomechanical (second sound) transducers in superfluid 4He has been applied. The technique for generalization of the theory to conducting and quantum fluids along with the experimental apparatus used to verify the generalizations will be described. [Work supported by the ONR.]
Maturation effects on binaural interaction in human auditory middle latency evoked potentials
Authors: McPherson D. L. , Tures C. , Starr A.
Published: October 2005

An interaction of the binaural auditory pathway may be observed in human auditory evoked potentials by subtracting the evoked potential to binaural stimulation from the sum of the evoked potential to monaural stimulation. The present study deals with the maturation of the binaural interaction component (BIC) of the middle latency potentials in infants and the difference seen between infants and adults. Eight adults and ten term infants were used in this study. Auditory evoked potentials were obtained for: (1) left monaural stimulation; (2) fight monaural stimulation; and (3) binaural stimulation. Individual binaural interaction waveforms were derived as described above. A shift of the major component of the binaural interaction between the adult and infant was observed. The largest BIC occurs in the adult at the time of P30 and N40 with a 41% interaction at P30 and a 21% interaction at N40. The morphology of the infant middle latency potentials differs significantly from the adult form by the narrowness of an N13 component and the lack of a clearly defined P30. N40 does not occur in the infant. The major interaction in the infant occurs at the time of N20, showing an interaction of 45%. This difference probably reflects changes in the middle latency components between adults and infants, with the adult showing a predominant P30-N40 component. [Work supported in part by the National Institutes of Health and the National Foundation March of Dimes.]
Auditory middle latency and steady-state responses in infants
Authors: Stapells David R. , Costello Jamie A. , Smith Donna , Makeig Scott , Galambos Robert
Published: October 2005

The effects of stimulus rate, intensity, and tonal frequency on the auditory middle latency and steady-state responses (MLR/SSR) were investigated in 29 normal infants (1–36 months) and in eight normal adults. Adultlike MLRs (10/s) were recordable in only 5 infants, 14 demonstrated responses with “immature” morphology, and ten demonstrated no MLR components after Na. Compared to adults, infant SSRs were lower in amplitude and demonstrate different scalp distributions. Unlike the adult data, no consistent amplitude peak was seen across rate, and phase coherence increased up to highest rate tested (59/s). Infants required higher stimulus intensities to produce adultlike SSR phase coherence values: 83% of the recordings to 70-dB nHL tones presented at 43.4/s showed significant values (p <0.01), decreasing to 35% at 40 dB nHL. These results are very different from those we previously reported for adults [Stapells, Makeig, and Galambos, J. Acoust. Soc. Am. Suppl. 1 77, S66 (1985)], and suggest that infant MLRs and SSRs undergo complex changes with maturation. [Work supported by DRF and NIH.]
Some phonetic characteristics of speech produced in noise
Authors: Bond Z. S. , Moore Thomas J. , Gable Beverley
Published: October 2005

This study is concerned with changes in the acoustic-phonetic structure of isolated words produced when the talker is in a high-noise environment and/or is wearing equipment that produces an obstruction to articulation, e.g., an oxygen mask. The speech of four young males was recorded in three conditions: quiet (laboratory recording conditions), while listening to white noise at 95 dB SPL over earphones, and while listening to the same noise levels introduced into the earphones of a standard Air Force helmet equipped with an oxygen mask. Speech produced while listening to noise over earphones alone showed the expected increases in fundamental frequency and amplitude. In addition, the duration and formant structure of vowels, and to a lesser degree the timing of consonantal gestures, changed when speech was produced in noise. Preliminary indications are that speech produced while wearing a helmet and oxygen mask was minimally affected by noise introduced over the headphones. [Supported in part by AFOSR.]
Syllabic constraints on P centers
Authors: Smith Mary R.
Published: October 2005

The location of P centers in monosyllables is affected by changes in durations of phonetic segments. Four natural ways to affect duration have been studied previously: phonetic changes in syllable onset, nucleus, and coda, and changes in speaking tempo. Syllable durations are also affected by the presence of other syllables within a word and the resultant stress patterns. In this study the effects of syllable compression and lengthening on P-center location are examined, together with effects of stress pattern, in natural productions of morphologically derived and inflected forms of base words such as prove and stead. The P centers are describable with reference to the stressed vowel in polysyllables. The previously observed asymmetry of effect between syllable onsets and rimes appears not to extend to prefixes and suffixes beyond the effects such affixes have on the stressed syllable segment durations.
Measurement of the nonlinear parameter of mixtures to test Apfel's tissue composition model
Authors: Everbach Erich Carr , Apfel Robert E.
Published: October 2005

Recently a methodology was proposed for predicting tissue composition (percent water, protein, and fat) from measurements of density, sound velocity, and acoustic nonlinearity parameter [R. E. Apfel, J. Acoust. Soc. Am. 79, 148–152 (1986)]. Comparisons of predictions with the measurements of others and with data from handbooks have been encouraging, but a more systematic comparison between theory and experiment was called for. We have established a facility for measuring accurately the sound velocity and nonlinear parameter of liquids and semiliquid substances and we are applying it to the measurement of mixtures in order to test the validity of our composition-predicting methodology. Eventually we will apply our measurement approach to tissues. Progress on experiment and theory will be presented. [Work supported in part by the Office of Naval Research and by the National Institutes of Health.]
Creak as a sociophonetic marker
Authors: Henton Caroline G.
Published: October 2005

Previous investigations into creak (vocal fry or pulse phonation) concentrated on two aspects: establishment of the physiological, acoustic, or perceptual nature of creak compared with other phonations; or separation of its characteristics in normal speech from pathological voices. The approach here is entirely different. Taking the phonetic and linguistic incidence of creak in normal speech in two accents of English as a starting point, quantitative description of its occurrence is provided. Data are taken from large numbers of speakers producing meaningful utterances in a recording task unrelated to voice quality. Support is given to the previous (unquantified) notion that creak accompanies utterance-final low falls and may be a turn-relinquishing signal. In addition, important cross-accent and cross-sex differences in the usage of creak are revealed. The results indicate that future descriptions of male-female voice quality differences should acknowledge creak as an important sociophonetic marker. Furthermore, phonological accounts of accents should incorporate information about a community voice quality. Last, clinicians will benefit from a quantitative account of creak in “normal voice” and may be led to adjust their parameters of abnormality accordingly.
Prosodic variants of syllable templates for speech synthesis
Authors: Macchi Marian , O'Brien Jennifer , Streeter Lynn
Published: October 2005

In many speech synthesis sytems based on concatenation of prerecorded units, the same segmental template is used in different prosodic environments, typically with simple manipulations of acoustic parameters. The present experiment investigated how successful simple techniques are for syllable-based synthesis. English speakers produced CVC and CV syllables with /p,b,w/ and /i,a,ay/, in isolation and in polysyllabic reiterant phrases (e.g., /bayb bayb bayb bayb/) with different stress and intonation patterns. Pitch tracking the LPC analysis were performed, and syllable templates were excised. Hybrid phrases were created by replacing a syllable template in one prosodic environment with a template for the same syllable from another prosodic environment, substituting the appropriate duration, fundamental frequency, and amplitude. Listening tests showed that natural-sounding hybrid unstressed syllables can be constructed from templates from stressed original syllables, but not vice versa. Also, hybrids should retain the syllable position of the original templates (e.g., phrase-initial, phrase-final). These results are useful for determining which manipulations produce natural-sounding speech, and deciding whether multiple templates for the same segmental unit are necessary.
Effects of cue impoverishment on intelligibility and naturalness of synthesized velar stops
Authors: Malsheen Bathsheba J. , Wright James T. , Yue Melanie
Published: October 2005

In a previous test of two MITalk-based synthesizers [B. J. Malsheen, J. T. Wright, M. Yue, and M. Peet, J. Acoust. Soc. Am. Suppl. 1 79, S25 (1986)], we found that the intelligibility of velar stops degraded more for one system than the other in a simulated telephone bandwidth condition. We hypothesized that this degradation was due to missing secondary cues normally present in human velar productions. In order to test this hypothesis we examined short-time spectra of the synthesized velar bursts and compared them with those produced by a male human speaker. We found that the synthesized velars lacked a number of acoustic cues present in the human productions. Secondary high-frequency energy peaks for initial and final velars before and after nonfront vowels were missing, primary peaks for front vowels were lower in frequency than those apparent in the human spectra, and primary peaks for nonfront vowels were higher. Velar stops were then resynthesized on the basis of the human model spectra. Preliminary results show that the more fully cued velars sound less “chirpy” and more natural both in normal and telephone conditions, and that intelligibility has improved.
Stressing English noun compounds correctly
Authors: Sproat Richard W. , Liberman Mark Y.
Published: October 2005

We describe a program for assigning correct stress contours to noun compounds in English. It makes use of two kinds of knowledge: idiosyncratic knowledge about the stress behavior of various compound types and general knowledge about English stress rules. As an example of the first, place names such as Madison AVENUE generally have rightward stress, but the word street induces left-hand stress: MADISON street. Semantic relations between the component nouns are also important: We know that, if the left-hand member is a grammatical object of the right-hand member, stress is leftward (DOG catcher). Our program makes use of such idiosyncratic knowledge in determining stress by deducing the type of compound and the likely relations between the members. As an example of the second kind of knowledge, our program knows the “rhythm rule” whose consequence is that while stress in Tom PAINE is on the right, stress in TOM Paine AVENUE is stronger on Tom than on Paine. The obvious importance of such a program to speech synthesis is discussed.
VLF pulse propagation in range-dependent geoacoustic waveguides
Authors: Stephen R. , Holzrichter M.
Published: October 2005

The finite difference method is used to study VLF pulse propagation (peak frequency of 10 Hz) in shallow water waveguides (100-m water depth) with range-dependent depth and geoacoustic parameters out to ranges of 5 km. The method solves the full two-way elastic wave equation in space and time using an explicit scheme based on centred finite differences. Compressional and shear velocity and density can be varied arbitrarily in a two-dimensional grid. The models represent continental margin environments with both upslope and downslope propagation. Propagation can be studied in range-time space, in snapshots of the wave field at given instants in time and in frequency wavenumber space. In soft bottom environments where the shear wave velocity of the bottom is less than the compressional wave velocity in the water, energy is continually leaking into converted shear waves in the bottom and there are no “perfectly trapped modes.” However, for sources and receivers near the seafloor, Stonely waves are observed with velocities near the shear wave velocity. For sources over the continental shelf and receivers over the continental slope, the numerical experiments predict two new wave phenomena. Compressional ground wave arrivals are enhanced by focusing at the shelf break and water wave modes do not adapt immediately to changes in water depth. In the latter case, the water wave modes set up in the shallow water waveguide persists almost unaffected out to 2 km beyond the shelf break. Reflections of energy propagating back to the source from the shelf break are also observed.
Sound propagation in three dimensions using a new numerical algorithm
Authors: Lee D. , Scully-Power P. D. , Botseas G. , Siegmann W. L.
Published: October 2005

Recently, a numerical algorithm was developed for solution of a three-dimensional, wide-angle parabolic approximation to the Helmholtz equation [D. Lee, Y. Saad, and M. Schultz, Proc. First IMACS Syrup. Comp. Acoust. (to appear)]. The method is both stable and efficient, since each range step requires solving only two tridiagonal systems. Numerical computations have been performed for test examples and model problems, and the accuracy and efficiency of the method have been illustrated. Extensions and improvements in the algorithm are reported here. These include implementations on parallel processors and on supercomputers, and modifications for switching between two- and three-dimensional calculations. The latter feature permits bypassing the full three-dimensional capabilities of the code where environmental conditions are sufficiently simple. Data requirements for three-dimensional computations using this new algorithm are discussed, in connection with longer range propagation through models of mesoscale variations such as fronts and eddies. [Work supported by NUSC and ONR.]
Time series simulation in a sloping bottom environment using ray theory
Authors: Westwood Evan K. , Hobaek H. , Tindle C. T.
Published: October 2005

A method for simulating time series in shallow water using ray theory has been extended to an isovelocity wedge with a penetrable bottom. Beam displacement at the water-bottom interface is included, and the resulting caustics are treated with correction factors. Simulated time series compare favorably with time series measured in an experimental, scale model tank using an 80-kHz pulse as a source signal. Mode extraction from sets of time series at different water depths works well on both simulated and experimental data. Phenomena such as wave front curvature, upslope mode cutoff, and downslope mode capture are investigated using the ray model. [Work supported by Independent Research and Development, Applied Research Laboratories, The University of Texas at Austin.]
On the controversial leaky Rayleigh wave at a water/ice interface
Authors: Chamuel Jacques R.
Published: October 2005

To the author's knowledge, no experimental data have been published to date isolating and demonstrating the existence of the controversial leaky Rayleigh wave originating at a water/ice interface. In this paper, ultrasonic laboratory results are presented demonstrating the existence of a leaky Rayleigh wave at a water/ice interface not meeting Brower's (1979) existence condition. The measured phase velocity of transient leaky Rayleigh waves is about 8% higher than the free Rayleigh wave velocity from the air/ice interface. The refracted shear wave amplitude is very small compared to the leaky Rayleigh wave. The received signal is dominated by the leaky Rayleigh wave when the receiver is simultaneously close to the source and at a distance of about one Scholte wavelength from the interface. Substantial energy is associated with the leaky Rayleigh wave indicating that it may be important to account for the contribution of the leaky Rayleigh wave in the problem of scattering from rough water/ice interfaces. The leaky Rayleigh wave is very susceptible to the presence of surface cracks in the ice. The reported findings provide physical insights into arctic acoustics and may contribute to the interpretation of arctic acoustic data. [Work supported by ONR.]
The influence of thermohaline steps on under-ice acoustic propagation: A simulation study
Authors: Chin-Bing Stanley A.
Published: October 2005

A simulation study of the influence of thermohaline steps on under-ice acoustic propagation has been made using a surface representation of hard layered ice with a water-to-ice transition region and a “stair-step” sound velocity profile (SVP) in the water. The ice surface was modeled using parallel layers of varying thicknesses, each layer being homogeneous in density, compressional velocity and attenuation, and shear velocity and attenuation. A water-to-ice transition region [S. A. Chin-Bing, J. Acoust. Soc. Am. Suppl. 1 78, S57 (1985)] was included to allow a gradual transition from the water to the multilayered ice. The water region contained the stair-step SVP that is often found in regions containing thermohaline steps [S. A. Chin-Bing and D. B. King, J. Acoust. Soc. Am. Suppl. 1 76, S84 (1984)]. Results indicate that the transmission loss structure is affected by both the stair-step SVP and the water-to-ice transition region.
A range-dependent normal mode model with full mode coupling
Authors: Robinson E. Richard , Wood David H.
Published: October 2005

A preliminary version of a range-dependent transmission loss model is presented. It assumes that the ocean is piecewise constant in range. We use full mode matching at the interfaces to compute the acoustic field. Our approach is similar to that used by Evans and Gilbert [“Acoustic propagation in a refracting ocean waveguide with an irregular interface,” Comp. Math. Appls. 11, 795–805 (1985)] in that we also expand the desired normal modes as a weighted sum of depth dependent basis functions. As is well known, this “Galerkin method” leads to a linear algebraic problem for the unknown weights. However, our approach is different because we insist on using other basis functions that lead to structured algebraic problems, where fast techniques are available. The future development of a fast version of this model will exploit this special algebraic structure. We implement within the generic sonar model because this allows for considerable flexibility in updating developments and the choice of supporting submodels.
Vortex modes in rooms
Authors: Waterhouse Richard V.
Published: October 2005

The existence of a circulation of sound energy in an enclosure of square cross section was demonstrated on theoretical grounds by Preston Smith in 1963. Recent work has confirmed experimentally the flow of sound energy in a vortex pattern in various sound fields. Here it is shown that for any rectangular enclosure (e.g., a room or duct) having reflecting walls with two dimensions in the ratio of any two integers, there exists an infinite set of vortex modes, whose frequencies form a harmonic series. Also, for an enclosure in the form of a rigid circular cylinder, there exists infinite sets of vortex modes whose frequencies depend on the extreae of the Bessel functions Jm. Energy streamlines are given for some of the above modes, and their practical significance is discussed.
The effect of oil and water on the absorption coefficient of selected acoustical materials
Authors: Burks J. Alton , Spencer E. R.
Published: October 2005

An acoustical martial utilized in the environment of an underground mine is subject to environmental deterioration from hydraulic fluid, moisture, and dust. These and other factors can cause physical degradation of the material and can affect the material's acoustical absorptive properties. The sound absorption coefficient of 16 different acoustical materials was measured after four different sample treatments: (1) clean and dry materials as a control, (2) immersion in water and draining, (3) immersion in 100 pct petroleum-type hydraulic fluid and draining, and (4) exposure in a coal mine. The standing wave method was used to measure the normal absorption coefficient. It was found that the absorption coefficient of most materials was adversely affected by the retention of either oil or water, with oil having the greater effect. The only class of materials which was affected by neither oil nor water was neoprene foam.
The linear theory of the wall-jet tone
Authors: Innes Dorothy
Published: October 2005

The wall jet is one of a class of flows, of which the jet-edge tone is typical, associated with the production of discrete frequency sound. We present an incompressible, inviscid model for the wall jet in which a uniform stream emerges from a two-dimensional duct and flows along a flat wall of finite length L. A “phase-locking” criterion leads to simple scaling laws for the tone frequency and stages of operation. Specifically, if f is the frequency of the tone generated in the nth stage, f = (U0/2b) (4b/L) (n + 83), the sound field assumes the familiar cardiodal shape associated with a dipole source located above a semi-infinite wall. These predictions are in agreement with the experimental data of Horne et al. (AIAA Paper ♯81–2043). [Work supported by ONR.]
A model of laser-induced bubble formation and collapse mechanism
Authors: Kim Joon-Hyuk , Lee Sangbum , Yang Hyup , Kwak Ho-Young
Published: October 2005

It is well known that the high power laser can produce the breakdown of liquid [M. P. Felix et al., Appl. Phys. Lett. 19, 484 (1971)]. The bubble formation and the shock wave emission after the breakdown have been observed simultaneously [W. Lauterborn and E. J. Ebeling, Appl. Phys. Lett. 31, 663 (1977)]. Usually, the cavity concept that the bubble is empty has been employed as an initial condition for the study of bubble motion. In this study, the initial conditions of the bubble evolution due to laser irradiation, i.e., the bubble wall velocity and the pressure inside the bubble just after the bubble evolution, were obtained from the bubble formation model proposed by Kwak and Panton [J. Phys. D 18, 647 (1985)]. Subsequent bubble evolution were calculated numerically by using the Gilmore equation in a compressible region and by using the Rayleigh equation in an incompressible region. The elapsing time from the bubble formation to the first bubble collapse and the farfield pressure signal at the first bubble collapse are in good agreement with the experimental results [W. Lauterborn (pp. 3–12) and V. S. Teslenko (pp. 30–34), both in Cavitation and Inhomogeneities in Underwater Acoustics, edited by W. Lauterborn (Springer, New York, 1980)]. Also, calculation results showed that shock strength and the amplitude of the pressure wave at the first collapse are strongly dependent upon the initial bubble wall velocity.
Response of polymorphonuclear leucocytes (PMNs) to vibration at kilohertz frequencies
Authors: Nyborg W. L. , Beeken W. L. , Northwood I. C.
Published: October 2005

It has been shown that stable volume oscillations of bubbles in a suspension of biological cells can cause significant change in the cells via small-scale manifestations of acoustic streaming, radiation force, and radiation torque. These aspects of the acoustic field are simulated, approximately, near small solid objects set into translatory vibration. Except for scale, the phenomena which have been observed at megahertz frequencies are similar to those seen at lower frequencies. In the experiments reported here suspensions of human PMNs, contained in glass capillaries, were exposed to transversely vibrating wires or strips, at frequencies of a few kilohertz, while under view through an optical microscope. As a measure of the potential of the vibrator for producing cellular change, calculations were made of the viscous stress associated with acoustic streaming near the vibrating surface. Among other findings, an increase of cell stickiness was observed at stress levels less than 1 Pa, as were changes of morphology revealed by electron microscopy. Considerable cell destruction occurred at stress levels exceeding 5–10 Pa. [Work supported in part by the NIH.]
Bond graph modeling for modal dynamics of interacting lumped and distributed systems
Authors: Margolis Donald L.
Published: October 2005

In many practical engineering systems, it is important to understand the physics of interacting subsystems, some of which lend themselves to lumped representations while others are inherently distributed. The noise and vibration caused by the engine of an automobile is a good example. The engine, the source of the vibrational and acoustical energy, is a lumped system for typical operating speed. However, the engine sits atop the vehicle frame structure, which exhibits modal dynamics. Ultimately, the vibrational energy finds its way to surfaces that radiate acoustic energy to the surroundings. If one were to model this overall system, lumped and distributed dynamic effects would have to be included. Bond graphs are a concise pictorial representation of the energy storage, exchange, and dissipation mechanisms of dynamic engineering systems [R. C. Rosenberg and D.C. Karnopp, Introduction to Physical System Dynamics (McGraw-Hill, New York, 1983)]. Considerable work has been done in developing bond graph methods for the modal dynamics of distributed systems [D. L. Margolis, “Bond graphs, normal modes, and vehicular structures,” Veh. Syst. Dynam. 7 (1) (1978) and D. L. Margolis, “A survey of bond graph modeling for interacting lumped and distributed systems,” J. Frankin Inst. 319 (1/2) (Jan. 1985)]. The virtues of bond graph modeling are many and space is short; however, once a bond graph model has been constructed, then physical state variables are dictated, and the system can be automatically simulated using a digital computer. This applies to nonlinear as well as linear systems except that the distributed aspects of the overall system must be linear. The paper will develop bond graph modeling for lumped and distributed systems, and the procedure will be demonstrated for realistic systems.
The rise and fall of forward masking
Authors: Carlyon Robert P.
Published: October 2005

Three experiments investigated the forward masking of brief sinusoids by noise bursts as a function of masker duration and of masker-signal delay. Experiment 1 showed that for a 2-kHz signal and a 5-ms delay, long-duration maskers produced much more masking than brief maskers. Recovery from the longer maskers was more rapid so that at a delay of 40 ms this difference was reduced. Experiment 2 showed that, for a 2-kHz signal, the transition from simultaneous masking to forward masking was accompanied by a large drop in threshold. For a 250-Hz signal this large drop occurred as delay time was increased from 10 to 20 ms. This result was attributed to ringing on the basilar membrane. Experiment 3 compared the recovery functions for three maskers of different durations, with masker levels adjusted to produce equal masking of a 2-kHz signal at a 5-ms delay. Brief intense maskers produced slower recovery than longer weaker ones. This finding has implications for attempts to model recovery from forward masking.