bluuebunny/crossref_metadata_2025 huggingface dataset:
Ray theoretic modeling applied to low-frequency interaction with the sea floor
Authors: Lawrence Martin W.
Published: October 2005

A computer model has been developed which uses ray theory, with various corrections, to provide calculated acoustic pressure fields for a given geoacoustic model of the sea floor. This computer model has been used to provide acoustic pressure fields for comparison with those measured in the deep ocean using a harmonic source located near the sea floor, with receivers also near the sea floor and with a quasicontinuous set of source-to-receiver separations. The acoustic pressure fields calculated by the ray theory model are compared with those calculated by an exact technique (using the Hankel transform). The decomposition of the acoustic field into components generated by different ray families is used to assist in understanding the results of the exact technique. The effect of variation of some experimental parameters can be more easily studied using this model than the Hankel transform model. For example, the effect of source height variation may be addressed.
Low-frequency sound propagation across a bathymetric ridge in the Strait of Juan de Fuca
Authors: Browning David G. , Lee Ding , Botseas George , Scully-Power Paul D.
Published: October 2005

In the deep ocean, bathymetric ridges have been shown to have a significant effect on low-frequency sound propagation [R. W. Bannister et al., J. Acoust. Soc. Am. 62, 847–859 (1977)]. These results may be further enhanced in the relatively shallow Strait of Juan de Fuca where a bathymetric ridge forms a sill across the Strait running north-south between Victoria, British Columbia and Port Angeles, Washington. This ridge not only significantly changes the bottom contour but also is the boundary between two distinctly different oceanographic domains. The implicit finite difference (IFD) model is used to determine the relative importance of changing bottom slope and oceanographic conditions across the ridge as factors affecting low-frequency (10–200 Hz) sound propagation. [Research supported by NUSC.]
Acoustic reflection from Arctic ice cover
Authors: McCammon Diana F. , McDaniel Suzanne T.
Published: October 2005

The ice canopy that covers large areas of the Arctic in winter is acoustically a very complex structure. It is a layered, anisotropic solid containing brine drainage channels as well as inclusions of brine and precipitated salts. Because of this complexity, it is desirable to ascertain those ice characteristics that play a dominant role in the reflection process. To this end, the plane-wave reflection coefficient for reflection from smooth ice and snow cover has been modeled using a matrix approach. Results are presented for frequencies of 1 to 5 kHz, showing the effect of layers of ice chosen to conform to a measured sound velocity profile in floe-ice. The reduction in reflectivity due to the absorption of shear and compressional waves in ice are displayed and the effect of the addition of a 30-cm snow layer is demonstrated. [Work supported by ONR.]
Model for Arctic propagation loss using scattering integrals and empirical reflection losses
Authors: Gordon D. F. , Bucker H. P.
Published: October 2005

A normal mode program for under ice propagation has been developed. To permit rapid computation, eigenvalues are determined for loss-less boundaries and attenuation is then added for reflection losses. Scattering from nonspecular angles is included by integration over ray paths from the surface to the source and receiver. Various published shot data were assembled and compared with computed propagation losses, using graphical methods, to determine ice reflection losses. Losses for ranges greater than 100 km gave the most definitive values for ice loss. Losses for shorter ranges, with greater dependence on grazing angles from 0° to 10°, were less definitive. Therefore, a linear function in decibels with 0-dB loss at 0° was assumed for the ice loss. The slope was then determined by comparison with the data. For Central Arctic data this slope is 1.125 × 10−3 f dB/deg (f is frequency in Hz) for frequencies from 0 to 400 Hz and a constant 0.45 dB/deg above 400 Hz. [Work supported by NORDA, Code 110 A.]
Acoustic analysis of the budgerigar vocal repertoire
Authors: Kline Cynthia A. , Dooling Robert J.
Published: October 2005

Previous ethological studies of the budgerigar (Melopsittacus undulatus) have provided a functional description of the vocal repertoire [B. F. Brockway, Anim. Behav. 23, 294–324 (1964)]. The present study describes the acoustic structure of each of these complex vocalizations with an emphasis on the contact call. Acoustic features of each vocalization were measured from standard sonograms. Most of the vocalizations of the budgerigar are short, discrete calls varying in duration between 20 and 200 ms. A long, rambling courtship vocalization is also described which varies in duration from 10 s to 1 min. This vocalization is composed of many different elements and is performed primarily by males. This courtship vocalization may be functionally similar to the song of oscine song birds. The acoustic properties of these vocalizations are discussed in relation to the hearing capabilities of the budgerigar. [Work supported by NICHHD and NINCDS.]
Discrimination of natural vocalizations by budgerigars (Melopsittacus undulatus) using operant techniques
Authors: Park Thomas J. , Dooling Robert J.
Published: October 2005

Budgerigars (Melopsittacus undulatus) were trained by operant techniques on a GO-NOGO discrimination task requiring the classification of complex species specific acoustic signals. Budgerigars began training on one pair of contact calls. After reaching a criterion of 85% correct, a third stimulus was added to the classification task. This procedure was reported each time budgerigars reached criterion on the current set of calls. By 70 sessions (days) budgerigars demonstrated the capacity for correctly identifying/classifying ten contact calls. Responses to probe stimuli indicate that the budgerigars were relying on the features of each call, not a rule or rules, in making a correct classification. Canaries (Serinus canarius) trained on the identical task failed to reach criterion on a single pair of budgerigar contact calls. These data suggest species differences in the perception and learning of complex vocalizations. [Work supported by NINCDS and NICHHD.]
Discrimination of frequency-modulated sounds by the frog Kassina senegalensis
Authors: Capranica R. R. , Harned G. D. , Passmore N. I.
Published: October 2005

Male South African running frogs (Kassina senegalensis) produce a pronounced frequency modulated (FM) mating call during the breeding season which serves to attract conspecific females. The call typically sweeps upward from 750 to 2250 Hz in 140 ms. Behavioral phonotaxis studies were conducted with 73 female frogs. Results from 475 two-choice playback discrimination trials, using natural and synthetic mating calls, verify that females can readily discriminate among a variety of FM signals based on sweep direction, duration, rate, and frequency range. Concomitant electrophysiological results indicate that these animals afford an opportune model for neurobehavioral studies of encoding of FM sounds in the vertebrate peripheral and central auditory system. [Work supported by N. I. H. Grant NS-09244, South African Council for Scientific and Industrial Research, and Animal Communication Research Program, University of the Witwatersrand.]
Surface and volume backscattering of broadband acoustic pulses normally incident on the sea floor: Observations and models
Authors: Dodds D. J.
Published: October 2005

When a broadband (1–10 kHz) impulsive (0.2-ms duration) acoustic source is directed vertically at the sea floor, the resulting echo contains a significant proportion of energy which does not remain coherent during horizontal translations of the acoustic system. This indicates that scattering is taking place. The scattering effects are a function of frequency, and the interaction of the source beam function with the bottom produces a time dependence as the expanding wave front encounters the sea floor at an increasing distance off the axis of the source. These effects can be displayed in a contour diagram of signal power as a function of time and frequency, called a sonogram. By using models of surface and volume scattering, a synthetic sonogram can be calculated from parameters of volume scattering and surface roughness. Such a synthetic sonogram can be fitted to an actual sonogram, yielding estimates of the parameters. These parameters promise to be useful in characterizing sediments, their acoustic properties, and their surfaces.
Acoustic volume scattering: 100 kHz to 10 MHz
Authors: Holliday D. V. , Pieper R. E.
Published: October 2005

High resolution profiles of acoustic volume scattering strength were made to a depth of 100 m at 18 frequencies spaced approximately logarithmically in a band between 100 kHz and 10 MHz. Stations were located in a complex marine environment extending offshore from Los Angeles, CA. High resolution temperature, conductivity, and chlorophyll fluorescence data were also collected and comparisons are made with the acoustic profiles. Interpretations of the data are made in relation to size and abundance of zooplankton collected at selected depths during the same cruise. Comparisons are also made to data collected in different seasons in the same geographic area. [Work supported by ONR and NSF.]
Bubbles near the surface of the ocean and their influence on wind-generated ambient noise
Authors: Farmer David M. , Lemon David D.
Published: October 2005

Bubbles of radius 40–400 μm are formed by breaking wind waves and are known to influence significantly air-sea gas exchange. Do they also modify wind generated ambient noise? For frequencies greater than 500 Hz, wind-generated noise typically has a constant spectral slope, but a layer of bubbles will scatter and absorb the sound, changing its spectral and directional properties at high wind speed. Observations in Queen Charlotte Sound, B. C., in bands centered at 4.3, 8.0, 14.5, and 25.0 kHz illustrate these effects; at sufficiently high wind speeds noise at 14.5 and 25.0 kHz actually decreases with increasing speed. The changes in spectral slope as a function of wind speed and frequency allow bubble populations and size distributions to be inferred. These were found consistent with previous photographic and bubble trap measurements, but the range of wind speeds encountered permits determination of a more complete relationship. Scattering and absorption by the bubble layer has implications for the use of ambient noise in passive remote sensing of wind speed and precipitation.
Hybrid ray-mode methods for underwater acoustic propagation
Authors: Felsen L. B.
Published: October 2005

Ray fields and guided mode fields form alternative and complementary building blocks for modeling high-frequency acoustic propagation in the ocean environment. Since the ocean waveguide is large compared to the local wavelength, a mode formulation requires many modes. In the presence of surface ducts and submerged ducts, a ray formulation at long ranges requires many rays. Since either formulation is therefore inconvenient, a hybrid combination in terms of rays and modes can introduce efficiencies and greater physical clarity. The foundation for the hybrid scheme is the ray-mode equivalent that permits a finite spectral interval of continuously distributed local plane-wave fields to be filled either with rays or with modes plus a truncation remainder. The equivalent can then be used to eliminate troublesome ray or mode spectral intervals and replace these by troublefree modes or rays, respectively. Exact for range-independent environments, including those with elastic layers where P-SV coupling may occur and ray species proliferate in consequence, the equivalent can also be formulated approximately for weak range dependence through use of adiabatic invariants. These concepts are developed, quantified, and illustrated on examples involving modal substitution for ray clusters in caustic forming surface ducts, for bottom glancing and refracting ray transitions, for collective treatment of ray fields in elastic layers, and for ocean channels with sloping penetrable bottom. Alternatively, rays are efficient for tracking interference maxima of groups of modes. Implications of these concepts for time-dependent propagation are also discussed. [Work supported by ONR, Ocean Acoustics Branch.]
Prediction of surface velocity of plate vibration using two microphones
Authors: Forssen Bjorn H. , Crocker Malcolm J.
Published: October 2005

A theoretical derivation is presented for the spectral density of the acoustic velocity in terms of the auto- and cross-spectral densities of the signals from two closely spaced microphones. This theory, a Fast Fourier Transform mini-computer, and a two-microphone probe, were used to measure the surface velocity of a vibrating flat panel. The surface velocity thus measured agrees quite well below the panel critical frequency with that measured by an accelerometer. Theory has also been developed to determine the difference between the sound pressure and intensity levels obtained with a two-microphone probe near to an arbitrary source distribution on a surface. The application of this theory to a point source and a rectangular radiator is discussed. An error analysis for these simplified cases is presented.
Scale-model studies of normal mode field
Authors: Shang E. C. , Clay C. S. , Yang Y. Y.
Published: October 2005

In recent years scale-model studies of normal mode fields in waveguides have been conducted by the authors both in the Institute of Acoustics, Academia Sinica, the Institute of Oceanography in China, and in the Department of Geology and Geophysics, University of Wisconsin-Madison in the United States. Some results concerning the implementation of mode filtering and some new techniques of signal processing in waveguides are summarized. The results of the study of source location-source ranging, source depth estimation, and source bearing in waveguides are presented.
High-frequency propagation modeling using HYPER
Authors: Tappert Fred , Lee Ding , Weinberg Henry
Published: October 2005

The hybrid parabolic equation-ray (HYPER) model previously described [J. Acoust. Soc. Am. Suppl. 1 74, S96 (1983)] has been further developed both theoretically and numerically. The small-angle Newtonian ray equation that is consistent with the parabolic approximation has been integrated numerically through strongly range-dependent ocean environments and compared to the exact rays with satisfactory agreement. The modified parabolic equation that correctly describes amplitude and phase within a ray bundle has been integrated numerically at kHz frequencies through strongly range-dependent ocean environments and the caustic structure at convergence zones has been examined. Comparisons to available caustic theories show that the HYPER model provides fully diffractive results that are uniformly valid.
Acoustic backscatter at low grazing angle from the ocean bottom. II: Statistical characteristics of bottom backscatter at a shallow water site
Authors: Chotiros N. P. , Boehme H. , Goldsberry T. G. , Pitt S. P. , Lamb R. A. , Garcia A. L. , Altenburg R. A.
Published: October 2005

Analyses of the statistical characteristics of bottom backscatter, measured in shallow water off San Diego, CA [T. G. Goldsberry, S. P. Pitt, and R. A. Lamb, J. Acoust. Soc. Am. Suppl. 1 72, S74 (1982)] are presented. An experimental sonar, operating at 30 kHz, mounted on the sea bottom was used to gather data over a wide sector of the bottom within its operating range. The bottom was comprised of areas of coarse and fine sand. The distribution function and probability of false alarm function of the detected envelope of a “widebeam” and a “narrowbeam” signal were measured. Some spatial and temporal correlation functions of the signal amplitudes were measured. A limited attempt was made to compare the results with existing theoretical models. [Work supported by NAVSEA 63R and NORDA Code 113.]
A semi-empirical model for high-frequency bottom backscattering
Authors: Jackson Darrell R.
Published: October 2005

Expressions have been developed for bottom scattering strength as a function of frequency and four bottom parameters. These parameters are rms roughness. sound speed, mass density, and a volume scattering parameter. Procedures have been developed for assigning best values to these parameters for poorly characterized sites, e.g., for sites at which mean sediment grain size or porosity is the only known quantity. This model is based upon the composite roughness and Kirchhoff approximations, but empirical adjustments have been made to fit data that lie outside the region of applicability of these approximations. [Work supported by NAVSEA.]
Angle spreads of broadband high-frequency signals reflecting from a random surface
Authors: Brill Michael H. , Zabal Xavier
Published: October 2005

A simple geometric-acoustic model (appropriate for high frequencies) has recently been used to compute time and frequency spreading of a broadband acoustic signal reflecting from an ocean bottom [M. H. Brill, X. Zabal, and S. L. Adams, J. Acoust. Soc. Am. Suppl. 1 73, S11 (1983); also 74, S76 (1983)]. In that model, the expected power received from a bottom facet dxdy at (x,y,0) is computed as a function of the x and y coordinates of the reflecting point on the bottom. A ray arriving from any reflecting point has a well-defined travel time, relative frequency shift (for a given source and receiver motion), polar arrival angle, and azimuthal arrival angle. In the present work, the received power from a grid of facets is histogrammed in the two arrival angles. The resulting histogram, called the angle-spread function, is a measure of the spatial coherence of the reflected signal. Computed angle-spread functions will be presented for various source/receiver geometries, and implications for sonar signal processing will be discussed.
Tinnitus occurence and modification—A case study
Authors: Campanella Angelo J.
Published: October 2005

In July 1982, a brief exposure to 133-dB 400-Hz sounds to the author caused a mild case of tinnitus to erupt that evening. Ancillary circumstances included insufficient earplug attenuation, fatigue, and hot weather. No significant TTS was noted at the time of exposure, though the environmental noise was sufficient to mask mild TTS. Tinnitus tones were generally above 4 kHz and occasionally of narrowband (versus tonal) quality at an SPL estimated to be about 35 dBA. Audiograms taken a few days after the exposure indicated no notable PTS, though personal experience indicated a slight loss of response in the 4-, 5-, or 6-kHz region. Lack of sleep was relieved by medication and tinnitus masking for a few weeks. Long-term acclimatization is now more or less complete. Recent measurements indicate that permanent tinnitus tones lie in the 10 to 13 kHz region. Mild exposure to noise (vis, a 60-mile automobile trip without earplugs) incites lower tones in the 5- to 8-kHz region which persist for a few hours. Mechanical pressure on certain skull locations will increase the 10/13-kHz tinnitus tone level by 10 to 20 dB. Still another pressure point will stop the tone as long as the pressure is applied. Blood pressure pulses individually modulate the 10/13-kHz tinnitus by an estimated 10 dB. Acoustical measurements pertinent to these observations will be presented. Such observations suggest that tinnitus can be altered by such mechanisms as pressure, stresses, or dislocations in the cochlear region. It is also possible that the damage mechanism (in this case) would include mechanical stress induced in the cochlear assembly and its attachments by intense sound vibrations.
Detection of frequency modulation by normally hearing and severely-to-profoundly hearing-impaired listeners
Authors: Grant Ken W.
Published: October 2005

Listeners with a severe to profound hearing loss often perceive changes in loudness when the frequency of a stimulus is changed. As a result, researchers who have studied frequency discrimination in impaired listeners may have underestimated the extent of the frequency impairment. In this study, we compare normal and impaired listeners in three frequency modulation detection experiments, in which the amplitudes of the test signals were either fixed, sinusoidally modulated at a constant rate of 3 Hz, or randomly modulated at rates of 3 Hz and below. Results for listeners with normal hearing showed that modulation of signal amplitude yielded Δ FMs that were 2–3 times larger than those obtained with fixed amplitude. Results for one impaired listener tested thus far show abnormally large Δ FMs for all conditions, and, in addition, that Δ FMs obtained with random amplitude modulation are as much as 45 times larger than those found for listeners with normal hearing. [Work supported by NIH.]
Loudness discomfort level measurements and their implications for the design and fitting of hearing aids
Authors: Dillon Harvey , Chew Robyn , Deans Margaret , Tonisson William
Published: October 2005

If the maximum power output (MPO) of a hearing aid is set at too high a level, then the aid wearer experiences discomfort from the intense sounds produced. This paper presents measurements of the loudness discomfort level (LDL) of 120 hearing-impaired individuals. As well as large differences between the average LDLs of the subjects, there are large differnces in the shapes of the LDL curves. For subjects with severe to profound losses, the shape of the LDL curve is closely related to the shape of the threshold curve. Some of these individuals have as little as 5-dB dynamic range available between their threshold and LDL at some frequencies. The extreme range of shapes, especially when combined with narrow dynamic ranges implies that a similar range of shapes should be available in the MPO curves of hearing aids if aid wearers are to have an audible, comfortable signal present in each frequency region. This feature can be readily arranged in aids incorporating compression limiting.
Improved frequency-lowering technique
Authors: Posen M. P. , Reed C. M. , Braida L. D. , Durlach N. I.
Published: October 2005

Frequency lowering is a form of signal processing intended to make high-frequency speech cues available to those who cannot hear high-frequency sounds. We have evaluated a frequency-lowering technique studied by Lippmann [J. Acoust. Soc. Am. Suppl. 1 67, S78 (1980)]. In this system speech levels in high-frequency bands modulate 1/3 octave bands of noise at low frequencies, which are then added to unprocessed speech. We found, in agreement with Lippmann, that processing improved the recognition of stop and fricative consonants when the listening bandwidth is restricted to 800 Hz. However, we also found that processing degrades the perception of nasals and (particularly) semivowels, consonants not included in Lippmann's study. We modified Lippmann's signal processing by reducing the level of the modulated noise when low-frequency components dominate the speech signal. Preliminary results indicate that the modified system does not degrade nasals and semivowels, but maintains the processing advantage for stops and fricatives. [Work supported by NIH.]
The evaluation of speech-to-tactile transformations utilizing two training paradigms
Authors: Fluster Matt
Published: October 2005

Two distinct training paradigms, building block and holistic, were used to evaluate two speech-to-tactile transformations, vocoder and flowed spectrographic. A separate group of subjects was used for each of the four conditions in the 2 × 2 (transformation × training) experimental design. The building block subjects were taught first to identify a small set of vowels and consonants, followed by CVs and VCs, nonsense words, small phrases, and finally, small phrases in conjunction with a simple, visually presented game. Each level used elements from the preceding level. With the holistic paradigm, the subjects were only presented with the final task. No significant difference in the overall effectiveness of the vocoder versus the flowed spectrographic transformation was seen. However, in the initial level of the building block paradigm, vocoder subjects relied more heavily on durational cues. The stimuli were constructed following simple phonological, syntactic, and semantic rules. This stimulus structure was seen to have specific effects on the types of confusions found with the building block paradigm, and on the manner in which the subjects learned the tactile patterns in the holistic paradigm. Results of these experiments have implications for the evaluation of communication aids. [Work supported by NSF and NIH training Grant 5T32GM07057.]
Sound speed and attenuation in thin polymer films in the frequency range 0.2–1 GHz
Authors: Sessler G. M. , Gerhard-Multhaupt R. , West J. E.
Published: October 2005

Pressure pulses or pressure steps with rise times on the order of 0.2 ns can be generated in dielectric films by application of laser pulses to a specially coated surface of the dielectric [G. M. Sessler, J. E. West, and R. Gerhard-Multhaupt, Phys. Rev. Lett. 48, 563 (1982)] or by excitation with a quartz crystal [W. Eisenmenger and M. Haardt, Solid State Commun. 41, 917 (1982)]. The acoustic phenomena propagate in the thickness direction of the films and are reflected at its surfaces. If the samples are electrically biased or charged, electrode signals are generated upon each reflection. The sound speed may be obtained from the relative delays of these signals while the sound attenuation can be evaluated by comparing their spectra. A modification of the laser method consists in the generation of double (or multiple) pulses by splitting the laser beam into two (or more) components and delaying one component relative to the other by a time T. This results in a boost of the spectrum at the frequency f = 1/T. Measurements on PETP, PI, PVDF, and FEP yield sound speeds close to the values determined for bulk material with other methods and sound attenuation coefficients that rise almost linearly with frequency in the range 0.2–1 GHz. The attenuation data can probably be explained by a hysteresis-type absorption process.
The effect of viscous relaxation on sound propagation in porous materials
Authors: Haumeder M. v.
Published: October 2005

The Biot theory treats a porous, fluid-filled material as a composite of two, interpenetrating elastic continua. In the theoretical description this composite nature is reflected by a set of two equations of motion which are coupled via a flow term. It can be shown that this formulation includes viscous relaxation due to a local flow of the pore fluid relative to the frame. This local flow is strongly frequency-dependent because the geometry of the pores supports flow only for a certain wavelength range in which the fluid flow can follow the excitation by the elastic wave. Accordingly we derive a relaxation time τ which is partly determined by geometrical factors. τ is expressed in terms of permeability, porosity, viscosity, and effective modulus. The viscous relaxation in a porous material can result in a local minimum in the frequency dependence of the reflectivity and a corresponding step in the sound velocity. These and other unusual features predicted by the Biot theory are explained in terms of a viscous relaxation process.
Hydroacoustic analysis of multiple relaxation kinetics
Authors: Margulies Timothy S. , Schwarz W. H.
Published: October 2005

This investigation presents a hydroacoustic theory which accounts for sound absorption and dispersion in a multicomponent mixture of reacting fluids (assuming a set of first-order acoustic equations without diffusion) such that several coupled reactions can occur simultaneously. General results are obtained in the form of a biquadratic characteristic equation (called the Kirchhoff- Langevin equation) for the complex propagation variable χ = (α + ωi/c) in which α is the attenuation coefficient, c is the phase speed of the progressive wave, and ω is the angular frequency. Computer simulations of sound absorption spectra have been made for three different chemical systems each comprised of two-step chemical reactions using physico-chemical parameter data available in the literature. The chemical systems studied include (1) water-dioxane, (2) glycine-water, and (3) cobalt polyphosphate water mixtures. Explicit comparisons are made between the biquadratic characteristic solution and the approximate equation (sometimes referred to as a Debye equation) previously applied to interpret the experimental data for the total chemical absorption versus frequency. The relative chemical reaction and classical viscothermal contributions to the sound absorption are also presented. Several discrepancies that can arise when estimating thermodynamic data (i.e., chemical reaction heats or volume changes) for multistep chemical reaction systems when making dilute solution or constant density assumptions are discussed.
Pressure dependence of sound absorption in synthetic seawater at 0 °C
Authors: Hsu C. C. , Dickson A. G. , Fisher F. H.
Published: October 2005

Measurements have been made of sound absorption in Lyman and Fleming seawater at 1 and 307 atm. Results for maximum absorption per wavelength (αλ)max/106 are 45.8 ± 0.4 at 1 atm and 28.9 ± 0.6 at 307 atm. The relaxation frequency of ∼39 kHz appears to be independent of pressure as had been observed earlier at 25 °C. Our results are in excellent agreement with the predictions of Francois and Garrison for 0 °C for both sound absorption and relaxation frequency. Based on these results together with the earlier ones at 25 °C reported by Hsu and Fisher [J. Acoust. Soc. Am. 74, 564–569 (1973)], we find a temperature dependence for both absorption and relaxation frequency different from that reported by Francois and Garrison. These differences will be discussed. The following equation represents our results for absorption (s = ± 0.8): (αλ)max/106 = 45.6 + 0.652(t/°C) − 0.0533(P/atm). [Work supportedby the Office of Naval Research, Code 400R.]
The influence of the dissolved ion concentration on the acoustic cavitation threshold of water
Authors: Atchley A. A. , Crum L. A. , Reidy J. R. , Roy R. A.
Published: October 2005

The variation in the transient acoustic cavitation threshold of water was measured as a function of the dissolved ion concentration of various salts. The measurements were made with a resonant sphere system in which solid particle size, water temperature, and dissolved gas content could be controlled within a closed circulating system. The normal criterion used for a cavitation event was the detection, by a photomultiplier tube, of sonoluminescence produced by a collapsing cavity. Water with a specific conductance of about 1 μS cm−1 was assigned zero concentration for the first data point. Measurements were then made at successively higher concentrations, up to 10 mmoles 1−1. The salts were chosen to check and extend the measurements of a previous researcher [V. A. Akulichev, Sov. Phys. Acoust. 12, 144–149 (1966)], who first detected a dependence of the cavitation threshold on dissolved ion concentration. The results of our measurements show that the threshold increases with ion concentration, reaching saturation at concentrations of 2 mmoles 1−1 or less. This dependence is in the opposite direction to that observed by Akulichev. Our results will be analyzed with regard to the standard models of cavitation nucleation. [Work supported in part by the Office of Naval Research and the National Science Foundation.]
Discrepancy between experiment and theory for magneto-acoustic fields in salt water
Authors: Pierce Allan D.
Published: October 2005

Moose and Klaus [J. Acoust. Soc. Am. 74, 1066–1068 (1983)] report results of novel and carefully controlled fundamental experiments in which a rectangular Plexiglas container filled with saturated salt solution was between the poles of a strong electromagnet. When the solution was driven at an acoustic resonance frequency an oscillating electric potential difference developed between electrodes placed on container sides parallel to magnetic field lines. The potential difference was nearly ten times larger than magneto-acoustic theory predictions. This abstract and proposed talk is with belief that such a discrepancy should not be ignored by the acoustics research community. Present author suggests that Moose and Klaus's assumption that electric field inside cavity has factored form f(x)g(y)h(z) may be an inappropriate approximation. A more nearly complete theory should take into account continuity conditions across container walls to the surrounding air, boundary conditions that require quasistatic electromagnetic disturbance to vanish at large external distances, and the presence of the electrodes. Simple estimates suggest the elaborated model will yield predictions more in accord with experiment.
Force on a sphere associated with nonuniform temperature distribution in an acoustic resonance chamber
Authors: Leung Emily W. , Wang Taylor G.
Published: October 2005

In an acoustic resonance chamber, the force on a hollow heated sphere is investigated. The temperature of the sphere is controlled by a heater inserted inside its shell. The heating of the sphere produces a nonuniform thermal gradient in the resonance chamber. During the heating and the cooling process, the resonance condition is maintained by an analog tracking technique. The force on the sphere in a direction perpendicular to the direction of gravity is measured. Steady and nonsteady forces were observed under various conditions.
Response to ultrasound of a Cheng-type liquid crystal cell
Authors: Hamidzada W. , Letcher S. V.
Published: October 2005

We reported earlier on the ultrasonic response of a bistable twisted nematic cell [W. Hamidzada and S. V. Letchef, J. Acoust. Soc. Am. 72, 561 (1982); Appl. Phys. Lett. 42, 785–787 (1983)]. We now report on similar properties of an untwisted nematic cell that can have two different types of bistability [G. D. Boyd, J. Cheng, and P. D. T. Ngo, Appl. Phys. Lett. 36, 556–558 (1980)]. Sensitivity is quite good, but depends rather strongly on the state of the cell and on the angle of incidence of the sound. Ultrasonically induced switching from the so-called vertical to horizontal state (or vice versa) is difficult because of the disclination motion that is required, but it is possible to induce switching between two similar, but optically distinguishable, states that exist in the horizontal state with a holding voltage.
Review of conventional methodology used for predicting the propagation of sound outdoors
Authors: Brittain F. H.
Published: October 2005

Many factors affect the outdoor propagation of sound, some of which remain roughly constant and others vary considerably with time. For example, the variable propagation characteristics of the atmosphere can cause noise from an industrial source to be annoying at one time and inaudible at another, as perceived in a community. As an introduction to the special session on outdoor propagation of sound, this paper will cover various phenomena that affect propagation of sound through the atmosphere, including spherical spreading, atmospheric absorption, turbulence, terrain/barriers, foliage, and ground effects. The quantization of these phenomena, and conventional methodology used for predicting their effect on noise in the community, will be discussed. Other factors that affect the variability of propagation characteristics of the atmosphere will be briefly reviewed.
Outdoor propagation models with and in the absence of barriers
Authors: Hayek Sabih I.
Published: October 2005

Analytic models for predicting the propagation of noise outdoors over uniform, flat terrain covered by a variety of ground covers have been proposed by the author and other researchers. These mathematical models are compared analytically and numerically for few ground cover impedances. Furthermore, when the terrain is partly covered by a hard pavement and partly by an absorbent ground, the models must take account of this discontinuity in the ground impedance. A review of the few analytic models developed by the author and other researchers is given and compared analytically and numerically. If a noise barrier is erected on a uniformly covered ground or over a pavement-absorbent ground, then the barrier performance is affected by the ground absorption. Various empirical analytic models based on geometrical acoustics and diffraction, which account for multiple diffraction by barriers located on an absorbent ground, are reviewed. [Work supported by FHWA.]
Sound propagation over the ground
Authors: Bolen Lee N.
Published: October 2005

The intensity of sound propagating outdoors is reduced by spreading losses and absorption losses. Absorption losses are due to atmospheric absorption and absorption by the ground and ground cover. At low frequencies, the major factor reducing intensity is reflection and interference and absorption by the surface of the earth. This paper will review the theoretical predictions of sound propagation losses over various ground covers. The prediction of sound intensity at some distance from an outdoor source near the surface requires a solution for a spherical spreading wave near a boundary. That boundary can be characterized by its impedance. Several models will be described which simplify the characterization of the surface in terms of a single parameter determined by the flow resistance of the surface. Several techniques to measure this parameter will be discussed, and a description of the calculation needed to predict the surface effects on the acoustic intensity will be presented. The effects of interference of the reflected wave and absorption by the ground surface will be described for a variety of surfaces. Effects of diffraction from barriers and atmospheric turbulence will be neglected in this review. [Work supported by ARO.]
Sound propagation through the atmosphere near the ground
Authors: Daigle G. A.
Published: October 2005

Within the first meter above the ground there are strong gradients of temperature and wind velocity. For sources or receivers on the ground these gradients produce significant refraction of sound, even at distances as short as 15 m. The refractive shadow is penetrated by energy diffracted via a creeping wave and good agreement is obtained between point source measurements and simple theory. In addition to their gradients, the temperature and wind fluctuate rapidly about their mean. Close to the ground, the spectrum of these fluctuations is dominated by eddies having a characteristic size of about 1 m. The resulting phase fluctuations of the sound increase with increasing distance, frequency, and strength of turbulence. Good agreement is obtained between measurements and simple theory that approximates the eddy spectrum by a Gaussian. However, the amplitude fluctuations are substantially smaller than predicted and, in addition, show clear evidence of saturation. Both experiments and theory are starting to show how and to what extent the acoustical shadow regions predicted by coherent theory are reduced by the effects of atmospheric turbulence, even at short distances.
Relating fluctuations of propagating acoustic signals to vertical heat flux
Authors: Roth S. David
Published: October 2005

The atmospheric boundary layer is said to be convectively unstable when the sun heats the earth's surface causing a positive temperature lapse rate to have developed near the surface. The surface layer (SL) of the convective boundary layer (CBL) has been studied for many years by meteorologists. The dynamics and structure of the convective SL have relatively recently become of interest to acousticians. The effects on propagating signals of mean temperature and wind velocity profiles as well as scatter from small scale eddies are fairly well understood. However, larger scale eddies known as “thermal plumes” which transcend the SL and in fact scale with the CBL have not been considered by the acoustics community. Thermals act as large scale discontinuities in the surface layer and their passage may cause variation of signals propagating over a 100-m path by about 30 dB. The transport of heat in the atmosphere is mainly accomplished by thermals [D. H. Lenschow and P. L. Stevens, Boundary Layer Meteorol. 19, 509–532 (1980)]. We therefore can expect that, to some extent, large scale fluctuations of propagating acoustic signals in the surface layer of the convective boundary layer will be related to the heat flux. Theoretical and experimental results are presented supporting this hypothesis.
Sentence intonation is context/discourse oriented: Evidence from Mandarin Chinese
Authors: Tseng Chiu-yu
Published: October 2005

Analysis of a corpus of simple declarative sentences extracted from natural spontaneous fluent speech in Mandarin Chinese (Tseng, 1981) shows that only 20% of the data can be accounted for in the declination theory (Maeda, 1976; Pierrehumbert, 1979; Sorensen and Cooper, 1980). In this study, the same corpus of sentences produced as unrelated utterances in read form are being examined in comparison with their spontaneous natural fluent counterparts. Results of intonation analysis from this set of production data appear to be adequately characterized by the “top-line” rule (Sorensen and Cooper, 1980), thus supporting one version of the declination theory to a certain extent. However, further analysis of those sentences whose natural spontaneous fluent versions cannot be characterized by the declination pattern shows the influence of contextual as well as discourse information, as noted by Umeda (1982). It appears that having the same syntactic structure does not provide much explanation or support for having the same intonation pattern. Furthermore, the intonation pattern of sentences appears to be governed by information beyond the scope of sentential information. The present investigation thus provides support for a context/discourse oriented theory of intonation.
Ultrasonically produced hyperthermia in ophthalmology
Authors: Lizzi Frederic L. , Driller Jack , Ostromogilsky Michael , Rosado Angel , Coleman D. Jackson , Torpey Joan
Published: October 2005

A series of related experimental and theoretical studies have been conducted on lesions produced in various structures of the eye by ultrasonically induced hyperthermia. Results obtained in animal eyes have been used to plan clinical treatments of various diseases. Clinical treatments of medically nonresponsive glaucoma are now in progress, and an 81% success rate has been achieved. This paper will review a theoretical model of ultrasonically induced hyperthermia. The model has been applied to the study of lesions produced in thin ocular layers by focused beams exhibiting various frequencies and beamwidths. Empirical corrections for blood flow cooling have been incorporated using data reported for related laser experiments. The model has successfully predicted the threshold values and sizes of experimental chorioretinal and scleral lesions that are useful in treating ocular disorders. In addition, the paper will describe ultrasound and thermal parameters that have been used successfully in treating human tumor transplants in nude athymic mice. [Work supported by NIH.]
Thermal dosimetry studies in ultrasonically induced hyperthermia in normal dog brain and in experimental brain tumors
Authors: Britt Richard H. , Pounds Douglas W. , Stuart Jeffrey S. , Lyons Bernard E.
Published: October 2005

In a series of 24 acute experiments on pentobarbital anesthetized dogs, thermal distributions generated by ultrasonic heating using a 1-MHz PZT transducer were compared with intensity distributions mapped in a test tank. Relatively flat temperature distributions from 1 to 3 cm have been mapped in normal dog brain using “shaped” intensity distributions generated from ultrasonic emission patterns which are formed by the interaction between compressional, transverse, and flexural modes activated within the crystal. In contrast, these same intensity distributions generated marked variations in three malignant brain tumors presumably due to variations in tumor blood flow. The results of this study suggest that a practical clinical system for uniform heating of large tumor volumes with varying geometries is not an achievable goal. Our laboratory is developing a scanning ultrasonic rapid hyperthermia treatment system which will be able to sequentially heat small volumes of tumor tissue either to temperatures which will sterilize tumor or to a more conventional thermal dose. [Supported by NIH/NCI CA29731.]
Rhythm in poetry and in prose
Authors: Lehiste Ilse
Published: October 2005

The paper describes an attempt to compare the rhythm of poetry with the rhythm of prose. Two poets read a number of their own poems in two modes, “poetry mode” and “prose mode.” The recordings were analyzed acoustically; segmental durations were measured from broadband spectrograms, while the duration of longer utterances and pauses was measured from oscillograms produced on a Honeywell model 1858 Visicorder. It was expected that the rhythm of read poetry would be more regular than that of materials read as prose. This was expected to be reflected in durational variability. Specifically, it was anticipated that the duration of metric feet contained in texts read as poetry would be less variable than the duration of the same verbal material read as prose. This expectation was not met: for both speakers, the variability of the durations of metric feet in texts read as poetry was greater than the variability found in texts read as prose. The difference was nonsignificant in the materials produced by one of the speakers; in the materials read by the other speaker, the durations of metric feet read in the poetic mode were significantly more variable than the durations of the same verbal material read as prose.
The perceived rhythm of English and French as assessed by the tapping task
Authors: Isard Stephen D. , Scott Donia R. , de Boysson-Bardies Benedicte
Published: October 2005

Pike [Intonation of American English (UMP, Ann Arbor, 1945)] and many others have claimed that English is a stress-timed language, having equally spaced interstress intervals (ISIs), as opposed to French which is said to be syllable-timed. Although measurements of ISIs in English show equally spaced ISIs to be the exception rather than the rule, it is the generally accepted view that there is a tendency for more-or-less equally spaced ISIs. Darwin and Donovan [Proceedings of NATO ASI, edited by J. C. Simon (Reidel, Dordrecht, 1980)] found that when English listeners were asked to tap out the rhythm of stressed syllable onsets of English utterances, the rhythm of their taps was more isochronous than that of the stress beats of the target utterances, and conclude from this that English is perceptually isochronous. Using the same task, we have replicated their results, but have found that English listeners also tap more isochronously to French targets. Moreover, so do French listeners. We conclude that the results of the tapping task cannot be used to support the distinction between stress-timed and syllable-timed languages.
Effects of accent on vowel amplitude in Japanese
Authors: Beckman Mary E.
Published: October 2005

It has long been known that accent (i.e., lexical stress) is a major factor contributing to variations in both vowel duration and vowel amplitude in English. An earlier experiment [Beckman, J. Acoust. Soc. Am. Suppl. 1 71, S1 (1952)] showed that, by contrast to English, Japanese accentual patterns have only a minimal effect on duration patterns. The present experiment compared accentual effects on amplitude in the two languages. It measured vowel amplitudes in a smaller subset of the minimally contrasting Japanese word pairs used earlier, as well as in a set of comparable English pairs. Three measures of vowel amplitude were obtained; namely, peak amplitude, average amplitude, and total amplitude. All three measures performed substantially worse as criteria for accent in Japanese than in English.