bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic correlates of social contexts and inferred internal states in howling monkeys (Alouatta palliata).
Authors: Whitehead James M.
Published: October 2005

Students of animal communication since Darwin have hypothesized that emotions find expression in animal utterances. This assertion is being tested in an examination of tape recordings of a well-studied primate, the mantled howling monkey, and of the natural contexts in which calls occur. Previous work has shown that, by means of sound playbacks, monkeys can be induced to approach the sound of another calling, hence possibly rival, male. Since approach to males is normally followed by prolonged vocal battles and sometimes by combat, it is hypothesized that acoustic correlates of stress or affective states such as fear or arousal will be evident in such features as lowered fundamental frequency, alteration of vocalization rate, instability of voice, etc. Although the study is incomplete, examination of the spectrum of roars, measured by FFT and LPC, has failed to reveal consistent differences. Possible reasons for the lack of acoustic differences include technical limitations, constraints on mechanisms of loud call production, and selection pressure against revealing intentions. [Supported by the H. F. Guggenheim Foundation.]
The perils of teaching speech acoustics.
Authors: Tobey Emily A. , Strange Winifred , Stevens Ken , Ladefoged Peter , Dorman Michael
Published: October 2005

The Speech Technical Committee of the Acoustical Society is composed of individuals from a variety of disciplines including linguistics, psychology, engineering, speech science, and communication disorders. The diversity of disciplines represented in speech communication results in studentbodies with a wide range of background knowledge in basic and speech acoustics. The purpose of this panel discussion is to stimulate a dialogue regarding current teaching practices, problem areas unique to particular disciplines, problem areas common across disciplines, and future directions for improving the instruction of basic and speech acoustics.
High-resolution estimates of spatially variable compressional and shear velocities within marine sediments.
Authors: Gettrust Joseph F. , Rowe Mary M.
Published: October 2005

Multichannel seismic reflection data are used to obtain estimates of compressional and shear velocities within marine sediments. Estimates of compressional velocities are made by interactively computing stacking velocities that transform the reflection hyperbola for reflection horizons to a straight, horizontal line. These stacking velocities are used to compute interval velocities that estimate the mean compressional velocity between two reflection horizons. The compressional velocity within the water column is known through direct source-to-hydrophone path travel times; typically, these direct path measurements are within 1% of the interval velocities computed from the seafloor reflection. This suggests that the estimates of the compressional velocity within the sediments are within a few percent of the ‘‘true’’ interval velocity, well below the 10% to 15% spatial variability over distances as short as 20 m that are resolved with these data. Shear velocity estimates computed using spectrum versus offset analysis show that the spatial variability of shear velocity over similar distances often is greater than 30%. [Work supported by the Office of Naval Technology and ONR.]
A measurement of the grain bulk modulus of sands.
Authors: Molis Joseph C. , Chotiros Nicholas P.
Published: October 2005

The grain bulk moduli of several different types of sand from various locations were measured. The method involves compressing a known volume of sand, held in an aluminum bowl, to about 13.78 MPa (2000 psi), using castor oil as the liquid medium, and measuring the volume of released liquid as a function of pressure. The apparatus consists of a pressure chamber, pressure sensor, release valve, and a graduated tube to measure the volume of released fluid. Pressure is decreased and the escaping volume of castor oil is measured, in about constant intervals of 0.344 MPa (50 psi). The change in pressure with respect to released volume and the measured volume of the sand sample are used to determine the grain bulk modulus. Sand samples from various locations have been analyzed. Previous models of acoustic propagation in sandy ocean sediments used an assumption that the grain bulk modulus of sand grains was equal to that of quartz. These results show that sand is significantly more compressible. [Work supported by Naval Oceanographic and Atmospheric Research Laboratories.]
A two-way parabolic equation method for elastic media.
Authors: Collins Michael D.
Published: October 2005

A two-way parabolic equation (PE) method for acoustic media [J. Acoust. Soc. Am. 91, 1357–1368 (1992)] is generalized to elastic media. A range-dependent ocean is approximated by a sequence of range-independent regions. The one-way elastic PE is used to propagate the transmitted and reflected fields through each of the regions. A scattering method based on the one-way elastic PE is used to compute transmitted and reflected fields at the vertical boundaries between regions. The scattering method is implemented using an efficient iteration formula for the reflected field that is analogous to the iteration formula for the two-way acoustic PE method. The two-way elastic PE method is useful not only for studying backscattering but also for achieving improved accuracy for the outgoing signal.
Data processing for high-resolution 3-D subbottom imaging system ‘‘kite.’’
Authors: Yamamoto Tokuo , Shon Howoong
Published: October 2005

A high-resolution 3-D subbottom imaging system called ‘‘Kite’’ has been successfully tested in shallow ocean near Miami Beach in July 1991. Kite is a 24-channel hydrophone array towed laterally, i.e., the axis is perpendicular to the direction of the ship motion. An omni-directional piezoelectric source located at the center of the hydrophone array is excited with a half-wave at 4 kHz every second while towed at 1 m/s. Each hydrophone signal is recorded at 16 kHz in 16 bits using an IBM compatible computer and an A/D converter. The 3-D image processing is done by using a software for conventional multi-channel seismic reflection data. First, the 3-D image of compressional wave velocity is constructed. The density and shear wave velocity images are constructed assuming the normal consolidation stress condition [Yamamoto etal., Geophys. J. Int. 98, 173–182 (1989)]. The results show that Kite has a great advantage in that it produces in high-resolution 3-D subbottom images while its data can be handled in a conventional way. [Work supported by ONR.]
CMR in complex masking backgrounds for normal and cochlear hearing-impaired listeners.
Authors: Hall J. W. , Grose J. H.
Published: October 2005

Comodulation masking release (CMR) was measured in masking backgrounds composed of multicomponent comodulated noise bands, with a variable number of bands (deviant bands) present that had a modulation pattern different from those of the comodulated set. Normal-hearing listeners showed results that were in agreement with previous findings [J. W. Hall and J. H. Grose, J. Acoust. Soc. Am. 88, 119–125 (1990)]: CMR was largest when no deviant bands were present; CMR was very small when only a few deviant bands were present; CMR recovered to some extent as more deviant bands were added. These results are interpreted in terms of frequency selectivity, auditory object formation by amplitude envelope coherence, and the ability of a listener to process a signal in the presence of competing background sounds. The data of cochlear hearing-impaired listeners showed considerable intersubject variability. Some of the hearing-impaired subjects had results that were very similar to those of the normal-hearing subjects (relatively large CMRs for conditions where there were no deviant bands, or many deviant bands). Other cochlear hearing-impaired listeners showed relatively small CMRs in general, but most of these listeners still showed an overall effect of improvement with increased number of deviant bands. Results will be discussed in terms of peripheral and central contributions to CMR. [Research supported by NIH NIDCD.]
Auditory filter shapes in normal-hearing, noise-masked, and elderly subjects.
Authors: Sommers Mitchell S. , Humes Larry E.
Published: October 2005

Previous studies of frequency selectivity have suggested a strong positive correlation between age and the width of auditory filters [Patterson etal., J. Acoust. Soc. Am. 72, 1788–1803 (1982)]. However, given that absolute thresholds are generally higher in older listeners, it is unclear whether the broader filter shapes are a consequence of aging perse or are associated with changes in absolute sensitivity. To dissociate the effects of hearing loss and increased age on changes in frequency selectivity, this study measured auditory filter shapes at 2 kHz in (1) normal-hearing young subjects; (2) elderly (over age 65) subjects with normal 2-kHz thresholds; (3) young subjects with 2-kHz thresholds elevated either 20 or 40 dB by a narrow-band masker; and (4) elderly subjects with varying degrees of hearing loss at 2 kHz. Rounded exponential filter shapes were derived from the data using the method described by Patterson [J. Acoust. Soc. Am. 59, 640–654 (1976)]. Equivalent rectangular bandwidths (ERBs) of auditory filters were not significantly different in young and elderly subjects with normal 2-kHz hearing. Furthermore, filter widths for young subjects with 20- and 40-dB simulated hearing losses overlapped with those obtained from elderly subjects with corresponding degrees of actual hearing loss. These results suggest that the reduced frequency selectivity reported for older listeners can be attributed, primarily, to hearing loss rather than increased age. [Work supported by NIH.]
Parabolic approximations for coherent low-frequency acoustic propagation through atmospheric turbulence.
Authors: Schurman I. W. , Siegmann W. L. , Jacobson M. J. , Robertson J. S.
Published: October 2005

A parabolic equation (PE) method for the prediction of coherent low-frequency acoustic propagation through small-scale atmospheric turbulence is presented. Frequency constraints on the applicability of stochastic parabolic approximations are avoided by first averaging the stochastic Helmholtz equation and then applying a parabolic approximation to the resulting deterministic equation. Turbulence effects are incorporated by means of spatially varying effective wave numbers. Comparison of exact solutions in the case of infinite-space propagation demonstrates the advantages and limitations of this approach. A uniform asymptotic expression for the effective wave-number profile in the case of isotropic turbulence is used to develop a half-space PE formulation that is valid in the limit of low-frequency, small-scale inhomogeneity. For anisotropic turbulence that is correlated more strongly in range than height, a modified mean-value theorem for the 2-D Helmholtz operator is used to find the effective wave number. Numerical examples demonstrate that excess attenuation due to the imaginary component of the effective wave number is the primary effect of weak turbulence on coherent low-frequency propagation. [Work supported by the U.S. Army Atmospheric Sciences Laboratory through the United States Military Academy and by NASA.]
Effects of ambient noise masking on earphone thresholds.
Authors: Williams Dennis L. , Frank Thomas A. , Schmitt Marie K.
Published: October 2005

Monaural thresholds were measured for 24 normally hearing subjects using TDH-49P, Audiocup, and ER-3A earphones from 500 to 6000 Hz in quiet and in background noise having maximum permissible ambient noise levels (MPANLs) specified by OSHA (1983) and ANSI (S3.1-1991). The attenuation for each earphone system was obtained and the actual threshold shift was compared to the predicted threshold shift. The mean threshold shifts were negligible (≤2 dB) in the ANSI MPANLs regardless of earphone and in OSHA MPANLs for the ER-3A but ranged from 2 to 7.5 dB for the Audiocup and from 6 to 12.5 dB for the TDH-49P in the OSHA MPANLs. The results of this study suggest that OSHA MPANLs are too high to allow for testing down to 0-dB HL using these earphones. The high noise-reducing properties of the ER-3A would make it the earphone of choice if testing is done in OSHA MPANLs. Testing down to 0 dB HL can be done in the newly specified ANSI MPANLs regardless of earphone type.
Theoretical aspects on noise attenuation efficiency of coffered ceilings.
Authors: Hirsch K. W. , Buchta E.
Published: October 2005

Coffered ceilings are used as noise abatement measures over shooting ranges for small arms. Usually these ceilings cover the entire ranges using a constant net size between the crossing baffle plates amid a constant plate height. With respect to the muzzle blast from the standard shooting positions and with respect to the sonic boom along the bullet path, size and height could be changed locally without losing attenuation in order to save material or costs, respectively. A ‘‘figure of merit’’ is needed to control a computer optimization process. This figure of merit must predict the relative changes in efficiency with respect to variation of size and height of the baffle plates with sufficient agreements with experimental data. A definition of such a figure of merit and some results of interest will be discussed.
The potential applications of fuzzy logic to problems in underwater acoustics.
Authors: Leonetti Marc C.
Published: October 2005

The methods of fuzzy logic and fuzzy statistics are applied to problems in underwater acoustics. Specifically, problems in underwater acoustics that require a decision to be made from incomplete and/or conflicting evidence are viewed from the perspective of fuzzy engineering. A method for making decisions based on the fusion of probabilities of multisensor inputs is discussed, and the role of a fusion rule is examined.
Active acoustic classification of underwater targets based on time-frequency analyses.
Authors: Hackman Roger H. , Arnold H. , Reagan J.
Published: October 2005

Active acoustic classification of underwater targets is an important problem of current interest. Previously published results have relied on the spectrum of the echo return as an input to a neural net classifier. In this paper, the echo return is regarded as a classic example of a nonstationary signal; the representation/analysis of such signals is normally accomplished by time-frequency distributions. The potential of a time-frequency representation of the target echo for classification purposes is investigated. The echo returns for a class of six targets (three spheres, two finite cylinders, and a prolate spheroidal shell) are numerically synthesized from T-matrix solutions and corrupted with white Gaussian noise to serve as a basis for the classification study. Several feature extraction schemes are presented. The performance of a probabilistic neural net classifier is investigated as a function of SNR for the different feature vectors. Optimum performance is obtained when the feature vectors are based on scattering dynamics.
Active acoustic classification of underwater targets based on scattering resonances.
Authors: Hackman Roger H. , Abatzoglou Theagenis J. , Arnold Hal , Specht D. , Washburne T.
Published: October 2005

This paper concerns the neural network based active acoustic classification of underwater targets. The feature vectors utilized in the training of the network are based on the scattering resonance parameters extracted from the echo return. It is expected that these parameters constitute close to an ‘‘optimum’’ set of feature vectors in that they greatly reduce the dimensionality of the echo return while preserving the ‘‘unique’’ aspects related to target identity. The classification performance of a probabilistic neural network classifier is evaluated for several different SNR levels for both monostatic and bistatic scattering configurations. The performance of several different resonance extraction algorithms (including the constrained total least squares technique and the SVD ‘‘Prony’’) is evaluated in varying levels of SNR. The classification study is based on echo returns synthesized from T-matrix solutions for five elastic targets (three spheres and two finite cylinders).
The cornett: Acoustics and construction.
Authors: McCann John R. , Mathews William G.
Published: October 2005

Although the cornett was one of the most widely used wind instruments during the late 16th and early 17th centuries, the construction of replica cornetts at modern pitch has not been straightforward. The cornett is excited by a lip reed as in modern brass instruments but has an approximately biconical wooden bore with toneholes. Cornetts surviving in European collections generally play at pitch levels higher than the modern standard and many of the few extant mouthpieces are of uncertain, possibly more recent, origin. As a guide to constructing replicas at modern pitch, the input and distributed impedances have been computed in the frequency domain. The accuracy of the computed frequencies for each fingering combination, although encouraging, is at present insufficient for reliable abinitio construction. However, the computations can be useful in determining appropriate perturbations in the size and placement of toneholes or in the bore required to achieve small differential frequency changes.
Handbells: ‘‘The Belles.’’
Authors: Seamons Janet
Published: October 2005

Some of the unique acoustical properties of handbells will be demonstrated with short musical selections.
Acoustics of Caribbean steel pans.
Authors: Hansen Uwe J. , Rossing Thomas D. , Hampton D. Scott
Published: October 2005

The foremost musical instrument in its home country of Trinidad, steel pans are becoming very popular in the United States and Europe as well. Steel pans are usually played in ensembles ranging in size from 6 to 8 players to 100 or more. Steel pans are usually fabricated from 55-gal oil drums, and are known by various names, such as lead, tenor, double tenor, guitar, cello, and bass. The sound spectra are rich in harmonic overtones, which appear to have three different physical origins: (1) radiation from higher modes of vibration in a given note area; (2) radiation from nearby notes whose frequencies are harmonically related to the struck note; and (3) nonlinear motion of the note area vibrating at its fundamental frequency. Modes of vibration of both single note areas and the entire drum have been studied by holographic interferometry and by modal analysis with impact excitation.
Phoneme recognition system.
Authors: Lisonbee James , Tebbs Dan , Wheeler Paul
Published: October 2005

The possibility of phoneme recognition using a hardware-based spectral sampling filter and a 386-μ processor software-based neural network to accurately recognize ten spoken vowel sounds of the English language was explored. To apply the neural network to speech recognition, a set of inputs conducive to the neural network architecture must be supplied. The spectral sampling filter does this by creating a pattern representing energy content in the first and second formants. This analog pattern is converted to digital and communicated to the neural network. The neural network was trained using a back-propagation technique. The neural network sees the localized energy changes across time as a distinct pattern for each phoneme. The neural network executes a recognition sequence and produces an integer correlating to the spoken phoneme.
Axial surface waves on fluid-loaded cylindrical shells below the ring frequency.
Authors: Means Steven L. , Pierce Allan D.
Published: October 2005

Surface waves are waves with speeds somewhat less than the speed of sound in the adjoining fluid and which are largely carried by the fluid itself. Such waves cannot propagate on a flat plate at frequencies below the coincidence frequency because the imaginary part of the surface impedance has the wrong sign. The correct sign is when the surface has spring-like behavior rather than mass-like (inertial) behavior. Based on such an analogy, one would not expect a cylindrical shell to support a surface wave at very low frequencies. However, the shell has a squeezing stiffness that makes its behavior more like that of a plate on an elastic foundation with relatively weak spring constant. An analysis is developed that shows that this spring constant per unit area is Eh/R2, where h is the shell thickness and R is the shell radius. The dispersion relation for the axial surface wave is developed and shown to give predictions consistent with recent experimental results and computational simulations of Williams, Houston, and Bucaro [J. Acoust. Soc. Am. 87, 513–522 (1990)]. [Work supported by ONR and by the William E. Leonhard endowment to Pennsylvania State University.]
Acoustic wave scattering from thin shell structures.
Authors: Norris Andrew , Vasudevan Naresh
Published: October 2005

The response of heavily fluid-loaded thin shells in the mid-frequency regime is studied using a general asymptotic theory. The technique employs the ideas of matched asymptotic expansions and splits the total shell response into the outer or background component and the inner or resonant contribution. This formulation is applicable to thins shells with varying material and geometrical properties. The background field satisfies an impedance condition that does not correspond to either the so-called soft or rigid conditions. The approach is to expand both the outer and inner fields in inverse powers of 1/kR, where R is a typical radius of curvature of the shell. The leading term in these expansions is selected so as to reflect the dominance of the tangential motion near a compressional resonance and the stronger radial motions in the outer region. Also derived are uniform asymptotic representations. The asymptotic method is applied here to study scattering from various nonseparable two-dimensional geometries. The numerical procedure is to first compute the outer solution, which requires solving for a particularly simple impedance condition on the surface. Then the inner resonances are added to give the total response. The numerical method employed in finding the outer solution is MOOT or the method of optimal truncation. Comparisons are made with the solution to the full set of coupled equations. [Work supported by ONR.]
Near-field sound radiation from a line-driven fluid-loaded infinite flat plate with periodic and nonperiodic attached rib stiffeners.
Authors: Cray Benjamin A.
Published: October 2005

The near-field acoustic pressure radiated from a line-driven, fluid-loaded, rib-stiffened plate has been obtained using numerical integration techniques. The plate has been configured to have two sets of rib stiffeners, though the formulation given may be extended to include additional rib stiffener sets. The stiffeners composing a given set are identical and are spaced periodically with distance l. However, one set of stiffeners is shifted by an amount Δ from the other set. In this manner, portions of the plate may be configured with repeating sections having nonperiodic rib spacing. The stiffeners exert reactive forces upon the plate, but not angular moments. Results are presented that show the variation of near-field acoustic pressure along the surface of the plate at a given stand-off distance and at a fixed frequency. At certain frequencies, the investigation revealed that the wavelength of the stiffened plate’s near-field acoustic oscillations−due to the propagating flexural wave−was much greater than that given by the unstiffened plate’s bending wavelength. The effect may be due to the stiffened plate’s flexural response being split into two components that are close together in wave number. The wavelength of acoustic oscillation appears to result from taking the difference of the two spectral components.
Acoustic scattering from a fluid-loaded finite plate with an attached structural fuzzy.
Authors: Russell Daniel A. , Sparrow Victor W.
Published: October 2005

In 1986 Christian Soize and his co-workers at Office National d’Etudes et de Recherches Aérospatiales in Chatillon, France introduced the concepts of fuzzy structures to account for missing degrees of freedom in structural vibration problems. The elements of Soize’s methods have been recently outlined [J. Acoust. Soc. Am. 89, 1867 (1991)]. The present paper concerns the scattering of an incident plane wave from a fluid-loaded finite plate to which a discrete structural fuzzy has been attached. Analyses will be presented for cases where the frequency of the incident field is both above and below the cutoff frequency of the fuzzy attachment. Below the cutoff frequency the fuzzy adds an additional fluctuating mass term to the in-vacuo modal masses that contribute to the plate velocity solution. Above the cutoff frequency, one must account not only for the mass contribution of the attached fuzzy, but also for the fluctuating internal damping and modal density of the fuzzy. [Work supported by ONR.]
Effects of junctions on radiation by plate and shell modes into a surrounding fluid.
Authors: Lu I-Tai , Bertoni Henry L. , Yao Yuqi
Published: October 2005

This discussion considers methods for computing radiation into surrounding water due to vibrating sources within a submerged vessel with internal structures. The vessel is viewed as a collection of plates and shells; the vibration of each component can be written as a superposition of flexural, extensional, and shear motions. Depending on the wave velocity, there can be two components to the radiated field. For example, the extensional wave can radiate continuously into water as it propagates along the outer hull. The angle of radiation is sin−1(vw/vl), where vl and vw are the velocities of the extensional mode and the acoustic wave in water, respectively. In addition, there will be radiation over a 180° spectrum of angles that originates from the vicinity of junctions between the hull and internal structures such as ribs and bulkhead. This radiation is an end effect arising from the fact that the shell/plate waves have a finite starting point. (Note that the flexural mode can also radiate through this diffraction mechanism even when the frequency is below the coincidence frequency.) An important aspect of this paper will be to evaluate the relative importance of these two mechanisms for various shell/plate modes. [Work supported by ONR.]
A comparison of mechanical lysis of erythrocytes and Chinese hamster ovary cells induced by ultrasonic cavitation in a rotating tube.
Authors: Thomas Ronald M. , Miller Douglas L.
Published: October 2005

Hemolysis of erythrocytes was compared to the lysis of cultured mammalian cells to determine how well erythrocytes can substitute for nucleated cells for the investigation of mechanical cell damage induced by ultrasound. Canine erythrocytes and Chinese Hamster Ovary (CHO) cells were exposed to cavitation in a 60-rpm rotating tube with a 1.61-MHz unfocused transducer, at increasing intensities (2, 4, and 8 W/cm2 SPTA), both separately at 2.5×106 cells/ml and mixed together, each with 1.25×106 cells/ml. Cell viability was assayed by counting on a hemacytometer, intact cells which excluded trypan blue dye. Results were normalized to 100% viability in sham exposed samples. The CHO cells appeared to be somewhat more sensitive to lysis under some conditions, and significant differences were noted after six repetitions at 8 W/cm2 in the separate and in the mixed exposures. At this intensity, viability was 73% (separate) and 58% (mixed) for the erythrocytes and 37% (seperate) and 32% (mixed) for the CHO cells. [Supported by PHS Grant No. CA42947 awarded by the National Institute of Health.]
Acoustic cavitation from diagnostic ultrasound.
Authors: Apfel Robert E. , Holland Christy K. , Crum Lawrence A. , Roy Ronald A.
Published: October 2005

Over the past several years a collaborative effort has been undertaken by several research groups to investigate the probability of in-vivo acoustic cavitation by diagnostic ultrasound devices. In the course of this research, movement has progressed from the initial prediction of its existence, through a variety of experiments invitro using existing clinical devices in which the characteristics of this cavitation have been measured, to the current efforts in which in-vivo experiments have been attempted. There will be a joint review of past progress and future plans will be described. [Work supported by NIH through Grant No. CA 39374.]
VLF/ULF noise on basalt and sedimented seafloor.
Authors: Lewis Brian T. R.
Published: October 2005

During project NOBS (7 Sept. 1991 to 10 Oct. 1991) four arrays of ocean bottom seismometers were deployed to record seafloor noise in the band 0.01 to 10 Hz. The arrays had 0-, 10-, 100-, and 1000-m sediment, and were all within a few hundred km of FLIP, which was located at 43° 42.63 N, 125° 59.19 W. Examination of two-dimensional wave-number spectra of waves from an earthquake and from noise shows that for frequencies from 0.1 to 0.5 Hz the wavelength is of order tens of kilometers, whereas above 0.5 Hz the wavelength of noise and signal-generated noise is of order tens of meters. Four conclusions can be drawn from the data at this time; from 0.1 to 0.5 Hz the noise is propagating at a relatively high velocity, probably as Rayleigh waves with speeds of order 3 km/s; from 0.5 to 10 Hz the noise is propagating at low speeds, probably as interface (Stonely) waves with speeds of order 0.1 km/s; shear energy undergoes a large amount of scattering from 0.5 to 10 Hz; noise from 0.5 and 10 Hz is probably produced by scattering at the seafloor and is largest where the sediment is thinnest.
Void-fraction measurements in bubble plumes generated by 2-D and 3-D breaking waves.
Authors: Lamarre Eric , Melville W. K.
Published: October 2005

Recent experiments have confirmed that low-frequency sound (10 to 300 Hz) is generated under breaking waves. It has been suggested that volume oscillations of the bubble plume generated by breaking is the mechanism responsible for the generation of this sound. Confirmation of this process requires independent measurement of the void fraction, and therefore sound speed, in the bubbly mixture. Detailed measurements of the evolution of the void-fraction field in bubble plumes generated by 2-D and large scale 3-D laboratory breaking waves are presented and compared. Various moments of the bubble plume void-fraction field give information on the (a) volume of air entrained, (b) cross-sectional area of the plume, (c) mean void fraction and sound speed, (d) bubble plume resonant frequencies, (e) potential energy of the bubble plume, (f) horizontal and vertical displacement and velocity of the bubble plume. These measurements along with independent measurements of the sound radiated (Loewen and Melville, this meeting) support the hypothesis that low-frequency sound is generated by the volume oscillation of the bubble plume. The radial dependence of the bubble plume’s void-fraction (and sound speed) field and its effect on low-frequency sound generation is investigated and the influence of the void-fraction instrumentation detection threshold in estimating the above moments is also examined. [Work supported by ONR (Ocean Acoustics) and NSF (Physical Oceanography).]
High-speed bubble sizing.
Authors: Koller D. , Li Y. , Shankar P. M. , Newhouse V. L.
Published: October 2005

Since a breaking wave has such a dramatic effect on the bubble population over such a brief period of time, it is necessary to acquire a bubble profile in a fraction of a second. A high-speed bubble-sizing technique has been developed that should have the capability of accurately determining bubble populations during breaking waves. Testing was performed in a pool 3 m in diameter and 1 m deep. An artificial bubble cloud was created through the use of compressed air and hypodermic needles. A three-transducer system was used to determine the existence of various bubble sizes. The system developed to date was able to acquire an average bubble spectrum from 2.5–6 kHz in 0.1 s. Through the use of the double frequency technique, there would be very little or no contribution from nonresonant bubbles at each frequency of interest. The results of the system were compared to the data obtained by listening to ambient bubble noise with a transducer and from photographic population counts. These comparisons demonstrated the effectiveness of this technique. [Work supported by ONR.]
Δk-acoustic sensing of the ocean surface.
Authors: Palmer A. J. , Frisch S. A. , Clifford S. F.
Published: October 2005

A new acoustic remote sensing method for measuring ocean surface directional wave spectra and currents is put forward. The method is termed Δk sonar or Δk sodar for beneath surface and above surface applications, respectively. The method is analogous to Δk radar. The basis of the Δk method is the use of two coherent beams of slightly different frequencies to project a (moving) fringe pattern onto the surface. This fringe pattern selects a single surface wave vector that will modulate the entire footprint of the beams on the surface. This modulation is revealed by the appearance of a ‘‘Δk resonance line’’ in the autocovariance spectrum of the frequency difference signal in the backscattered fields. Signal-to-noise calculations are presented which indicate that the method should be practical for sensing surface currents and wave spectra out to ranges limited by attenuation of the acoustic signals.
Geomorphic parameter estimations with neural networks using bathymetry and backscatter data.
Authors: Caruthers Jerald W. , Bourgeois Brian
Published: October 2005

A bistatic scattering strength model (BISSM) for low-frequency acoustics, which uses high-resolution geomorphology as input parameters, has been proposed [Caruthers etal., NOARL, SP023:200:90 (1990)]. Included in these geomorphic parameters are (1) deterministic bathymetry and local bottom-facet mean slope and azimuth, (2) the stochastic parameters, rms slopes in orthogonal directions and roughness, and (3) the empirical acoustic parameter, Lambert/Mackenzie scattering coefficient. The issue of how to obtain these parameters to support wide-area applications of the model led to a consideration of the inverse problem using the model itself at higher frequencies and in the backscatter direction. Swath sonar systems, simultaneously providing high-resolution bathymetry and backscattering strength as a function of grazing angle, would appear tractable as survey tools for these parameters, if the inverse problem is solvable. Presented here is a sensitivity analysis using neural networks to determine the potential validity of this approach. The model is presumed to be valid and is used to simulate noise-free backscatter data for different sets of parameters. Presented is the ability of neural networks to be trained to provide estimates of the desired parameters under these ideal conditions. [Work is supported by CNOC.]
Models of the distribution of received power in a random propagation medium.
Authors: Churnside James H.
Published: October 2005

The probability density function of the received power of an acoustic signal that has propagated through random sound speed fluctuations in the ocean can be obtained exactly only for two cases. The first case is where the power fluctuations are very small (much less than the mean value). In this case, the density function is lognormal. The second case, which is not realizable, is that of extremely large sound speed fluctuations or path lengths. This condition would produce a negative exponential density function of acoustic power fluctuations. A number of models for the probability density function of received power have been suggested for the region in between these two extremes. A successful model should be possible to evaluate numerically, should be physically plausible, and should describe available data. Candidate density functions will be reviewed, with an emphasis on those that were originally developed to describe optical propagation through the atmosphere.
Binaural hearing.
Authors: Hafter Ervin R.
Published: October 2005

Binaural hearing was not the central focus of Professor Zwicker’s long and distinguished career. However, during the 1980s he developed a strong interest in the binaural release from masking and, showing his usual fervor, he produced a long list of papers on the subject. These generally dealt with the interaction between binaural masking and some of his favorite auditory topics including: effects of such parameters as frequency, duration, and bandwidth; integration of information over time; loudness summation; recognition of vowels. Some of the currently most active topics in binaural hearing that will be discussed today include: binaural precedence and the special role of onset information in localization; the reduction of ambiguity in localization accomplished by comparing phases across frequencies in the binaural cross spectrum; localization in the open-field; generation of artificial open fields under headphones.
Adaptation and release from it in free field listening.
Authors: Hafter Ervin R. , Saberi Kourosh
Published: October 2005

Using headphone presentation, it has been shown that detection of an interaural difference of time or level in a train of n dichotic clicks is affected by the interclick interval (ICI). With ICIs ≥10 ms, thresholds decline as the √n as predicted for optimum signal processing. With shorter ICIs, the decline is as √nk with 0≤k≤1 and k=f(ICI). Such data have been said to show ‘‘binaural adaptation,’’ a process whereby each click is less effective than the one preceding. A release from binaural adaption has been found in response to appropriate acoustic ‘‘triggers’’ such as a gap in the train or a brief burst of noise. In the present study, minimum audible angles (MAAs) were measured in the free field using two loudspeakers in the horizontal plane placed on either side of the midline. Frequency responses of the speakers were equated with digital filters. Stimuli were trains (n=1 to 16) of bandpass clicks (cf.=4 kHz) with ICIs of either 2 or 10 ms. As with headphones, shorter ICIs produced adaptation. Various potential triggers were presented in synchrony with the center of the train in order to produce a release from adaptation, and release was defined by a √2 decline in threshold relative to that for a train of length n/2, indicating that the n/2 clicks in the second half were as effective as those in the first. [Work supported by a grant from the NIDCD.]
Reflection from a baffled strip of a ribbed panel.
Authors: Maidanik G. , Dickey J.
Published: October 2005

A formalism that describes the reflection properties of a ribbed panel is used to generate a formalism that describes the reflection properties of a baffled strip of a ribbed panel. The strip is defined by a pair of infinite rigid boundaries that lie normal to the direction of the parallel ribs. The formalism is demonstrated by computing the bistatic and monostatic reflections from the strip. Examples are cited for free-wave speeds that stimulate the flexural and the longitudinal free waves in a plate. In the former, the free-wave speed is dependent on the square root of the frequency and is subsonic below the critical frequency. The critical frequency is defined with respect to the speed of sound in the fluid that occupies the semi-infinite space above the panel. In the latter, the free-wave speed is supersonic and is independent of the frequency. The magnitude of the reflected pressure is presented as a function of the wave number that lies normal to the ribs and the frequency, or in some cases as a function of the monostatic angle and the frequency. The patterns exhibited in these plots are related to phenomena that are discussed.
Is the ‘‘4-kHz notch’’ in the noise-induced-hearing-loss audiogram due to a tectorial membrane resonance at 2.8 kHz (the frequency of the maximum external ear resonance)?
Authors: Killion Mead C.
Published: October 2005

If Allen is right, and the apparent transmission zero located one-half octave below the best frequency of a nerve fiber is due to the resonance of the tectorial membrane mass on its connecting stiffness, then perhaps an explanation for the half-octave shift in TTS and PTS above the stimulating frequency is available (the tectorial membrane agitation breaks off the hairs). Along the same vein, the typical diplacusis that accompanies a Meniere’s attack can perhaps be explained by the conflicting periodicity pitch cues (unchanged) and place cues (shifted due to the stiffened basilar membrane). The disappearance of diplacusis over time may be an indication of the plasticity of the tonitopic organization of the brain.
Instrumentation issues in collecting ear-canal acoustic distortion products.
Authors: Allen Jont
Published: October 2005

Ear-canal cochlear otoacoustic emission acoustic distortion products (DPs) appear to provide a window into outer hair cell function and are becoming an important noninvasive cochlear evaluation research tool. If they are to become clinically useful, a better understanding of their production and measurement is needed. The magnitude of the DP depends on the acoustic load of the transducer as well as the cochlear input impedance. The ear-canal impedance and the ER-2 and ER-10B acoustic impedance have been measured and predictions of the reverse transfer function were made. Less well understood are observed standing waves in the ear canal at high frequencies. These may be controlled by insertion of the sound delivery tubes deep into the canal. Measurement of the DPs using an Ariel DSP-16 signal processing board is described in a portable PC-notebook configuration. DPs are approximately related to hearing level (HL) according to the formula DP=8−0.5 HL, where both DP and HL are in dB. Several different useful measurement paradigms that have been investigated will be described.
Transducers for otoacoustic emissions measurement.
Authors: Killion Mead C.
Published: October 2005

Most otoacoustic emissions are relatively weak as measured in the ear canal. A system noise level of −20 to −30 dB SPL is required in order to measure some emissions of interest, which means microphone noise spectrum levels of −20 dB SPL or better are needed. In the case of stimulated emissions such as the cubic distortion product at the frequency 2f1−f2, the distortion product is often more than 80 dB below the level of the f1 and f2 primary tones. As a result, the intermodulation distortion requirements on the amplifiers and earphones are severe−typically 0.003% or so−requiring the use of two separate earphones which must be acoustically isolated from each other. Special transducer constructions and couplings designed to meet these needs will be described, as will a new set of transducers specifically designed to be used in an inexpensive infant screening device which can be carried in the pocket like a stethoscope.
Study of adaptive feedback stabilization of hearing aid.
Authors: Engebretson A. Maynard , French-St. George Marilyn
Published: October 2005

Instability is a problem with high-power and ITE hearing aids. Gain margins can be improved by 15 dB using an adaptive LMS filter to estimate the feedback characteristic and actively cancel it [Engebretson etal., ‘‘Adaptive feedback stabilization of hearing aids,’’ Second International Workshop on Hearing Impairment and Signal-Processing Hearing Aids, London, England, June 1991]. This algorithm was evaluated with a wearable digital hearing aid (WDHA). Nine hearing-impaired subjects were tested at 55 dB SPL, in quiet and in multitalker babble (6-dB SNR), with their own aid and with the WDHA programmed, with and without feedback stabilization (FBS), to match the REAR of their own aid. Subjects adjusted overall gain to their liking for each condition. Real ear measurements were taken to verify REAR. Correlation of word identification scores (PHFWL) with the subject’s own aid and the WDHA (FBS disabled) was high. With FBS enabled, subjects chose additional gain that ranged from 2 to 10 dB and scores improved by 7 percentage points on the average across subjects. [Work supported by DVA.]
Standing wave analysis of the low amplitude performance of a thermoacoustic prime mover.
Authors: Atchley Anthony A.
Published: October 2005

A standing wave analysis of the low-amplitude performance of a thermoacoustic prime mover is presented. The analysis, motivated by Swift [G. W. Swift, J. Acoust. Soc. Am. 84, 1145–1180 (1988)], assumes that the acoustic pressure and velocity can be described in terms of a standing wave throughout the prime mover. The analysis is not limited by either the small boundary layer or short stack approximations. The results of the analysis are compared to measurements of the quality factor Q of a prime mover both below and above onset. Measurements were made in both a helium- and an argon-filled prime mover for mean pressures ranging from approximately 80 to 500 kPa. Below onset the Q is determined from the frequency response of the prime mover. Above onset the Q is determined from the initial rise time of the acoustic oscillations. In general, the agreement is good, indicating that previous work on finite amplitude standing waves [A. B. Coppens and J. V. Sanders, J. Acoust. Soc. Am. 58, 1133–1140 (1975)] can, perhaps, be used to explain the observed high-amplitude waveforms in prime movers. [Work supported by ONR and the NPS Res. Prog.]
Register and speech variation.
Authors: Yaeger-Dror Malcah , Nunamaker Jay
Published: October 2005

There are several speech parameters that are known to vary radically with different speech registers. One of the primary concerns of sociolinguists has always been the degree to which speech ‘‘style’’ and ‘‘register’’ influence speech production; this variability is now of greater concern to members of Acoustical Society because the variation influences intelligibility of speech for machines, and of synthesized speech. This paper will discuss evidence that pitch contours, vowel reduction, and vocabulary choice are all influenced by register. This paper will focus on the use of the work "not," analyzing the relative likelihood of pitch prominence, neutral presentation, or reduction (n’t) in three different registers. Data from political debates will be compared with data from small group "brainstorming" sessions and with data from a DARPA workshop. There will be a discussion of the importance of this variation to both automatic speech recognition and speech synthesis. [Work partially supported by NSF.]
/l/ and /ng/ effects on vowel nuclei in four dialects.
Authors: Veatch Thomas
Published: October 2005

The effects of following /l/ and/ng/ on vowel quality as measured by nucleus F1 and F2 frequencies are compared across four vernacular dialects, including Alabama White, Chicago White, Los Angeles Chicano, and Jamaican Creole. Effects of both following /l/ and following /ng/ on vowel nuclei vary across dialects. The phonetic implementation rule by which /l/ is realized as darker or lighter [Sproat and Fujimura (1990)] is absent in Jamaican Creole, which has a lighter /l/ and different effects (/l/ only retracts back, non-low vowels). Some anomalous effects are given either phonological or phonetic explanations. /ng/ raises preceding /i/ consistently in all four dialects except Alabama, where /ng/ lowers the nuclei of preceding vowels including /i/. Since /ng/ presumably does not differ from one dialect to another, this difference cannot be mechanical. Nor is it a phonological effect, it is argued. Thus two strictly phonetic patterns are shown to be present in some dialects and absent or different in others. This is additional evidence for a linguistic component of the phonetic system by which phonological structure is realized as sound.