bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial broadband processing of active sonar echoes
Authors: Dwyer Roger F.
Published: October 2005

As shown at the 131st meeting [R. Dwyer, ‘‘Wideband higher-order spatial processing of active sonar echoes,’’ J. Acoust. Soc. Am. 99, 2497(A) (1996)] when linear sonar arrays are operated well beyond their design frequency, spatial resolution is reduced at low frequencies and grating lobes appear at higher frequencies. Because the higher-order spectrum provides more flexibility in choosing the frequency response at the output of a beamformer the deliterious effects of wide bandwidths can be reduced. New higher-order processing results will be presented for broadband active sonar waveform transmissions using general array configurations and with returns that can be expected in shallow-water environments.
Short-time Fourier transform, Wigner–Ville analysis, and wavelet transform compared
Authors: Romero J. , Cerdá Salvador
Published: October 2005

Short-time Fourier transform (STFT), Wigner-Ville analysis (WVA), and wavelet transform (WT) are possibly the more important methods of time-frequency analysis. STFT makes use of the time-window function to locate Fourier analysis. WT makes use of the time-frequency window to locate the analysis in the time-frequency domain. WVA is different than STFT and WT in the sense that no outer function is made that uses it in the analysis. Time-autocorrelation is defined and Fourier transform is applied. Six signals were studied with different methods. STFT was applied with three time windows: Gaussian, Hamming, and rectangular. The time duration of the time window has been varied (23, 12, 6 ms), showing the uncertainty principle effect. WT was applied using the real part of Morlet function. Improvements with respect to STFT were shown. Finally, WVA was applied to the signals. The time-frequency resolution of WVA is very good, but the presence of the 4π factor at the time to calculate the Fourier transform, reduces the frequency interval of analysis by a factor of two.
Classification of aircraft flight paths by detecting temporal changes in sound arrival direction
Authors: Makino Koichi , Yamada Ichiro , Hayashi Noriaki
Published: October 2005

Automatic classification of flight paths related to observed aircraft noises is useful for unattended aircraft noise monitoring. This paper describes a method of detecting flight paths based on temporal changes in sound arrival direction. The method applies the acoustical cross-correlation technique using four microphones. The sound arrival direction is expressed as a set of unit vectors on the surface of a unit sphere assumed to be at the center of the microphones. A field experiment was carried out near an end of a runway to confirm the effectiveness of the procedure. The rate of correct classification was 93%.
The earthquake T phase: MILS hydrophone array results
Authors: Duennebier Fred K. , McCreery Charles N.
Published: October 2005

During the 1960s, hydrophone arrays at seven MILS stations around the north Pacific were used to locate earthquakes using the T phase. Much of our knowledge of the characteristics of the T phase and of oceanic earthquakes came from this early study, which located more than 20 000 events in slightly more than 2 years. There were 3794 sources located by the T-phase project in 1966 in the Aleutian Islands region compared to 431 earthquakes located by the coast and geodetic survey in the region. Earthquakes of about 0.7 magnitude units lower than the C&GS threshold could be located by T phase. Study of these events resulted in recognition of mechanisms for propagation ofT -phase energy from the earth to the ocean. Classical slope generation at continental margins and islands feeds energy directly into the sound channel by multiple down-slope reflections. Scattering from the ocean floor and surface appear to account for the energy in the T phases from earthquakes beneath the deep ocean floor. More recent long-term recording of the Wake Island hydrophones has resulted in characterization of variations in ambient noise and of the earthquake Po and So arrivals, which appear to be trapped in the oceanic lithosphere.
A multipath model for T-wave generation by seafloor earthquakes
Authors: Hildebrand John A. , Fox Christopher G. , Dziak Robert P.
Published: October 2005

Seafloor earthquakes create seismoacoustic T waves traveling in the oceanic sound channel. T waves are useful to monitor earthquakes in the oceanic environment, allowing a reduction in detection threshold by at least two levels of magnitude. The physical processes involved in T-wave generation are not well understood. For example, in the case of a perfectly flat ocean bottom at a depth greater than the sound channel, it is not clear how energy radiated by the source is coupled to the sound channel. Likewise, the relationship between earthquake source depth and moment, and the T-wave amplitude and duration is not known. This paper investigates the coupling between seismic sources in the solid earth and T waves in the oceanic sound channel. In particular, the extended time duration of theT wave is related to coupling between the source and sound channel over an extended region at the seafloor, and this coupling is shown to be dependent on the seismic source depth. This work builds on previous observations by Schreiner et al. (1995) of variations in T-wave duration and spectral content with source depth associated with the Juan de Fuca ridge seismic swarm of 1993.
Seismic structure using body wave arrivals at SOSUS hydrophone arrays
Authors: Slack Philip D. , Fox Christopher G. , Dziak Robert P.
Published: October 2005

Body wave arrivals at SOSUS hydrophone arrays are used to determine the seismic velocity structure of the Juan de Fuca ridge and Cascadia subduction zone regions. Since 1991 NOAA has been recording data from the Navy’s SOSUS hydrophone arrays. This has provided a unique set of continuously recorded hydrophone data from oceanic stations. Body wave or P-phase arrivals from large earthquakes are detected by the SOSUS hydrophones. Using body wave arrivals Pn velocities of 8.0 km/s are measured for paths purely beneath the oceanic plates and for paths originating beneath the North American continental plate the Pn velocity is 7.7 km/s. For paths along the subduction zone velocities of 7.6–7.7 km/s are measured. The data from the SOSUS arrays are combined with data from the Pacific Northwest Seismic Network (PNSN), a network of seismic stations in Washington, Oregon and northern California, to construct a tomographic image of the crust and uppermost mantle for the Cascadia subduction zone. The model extends from the oceanic plate (131°W) to the North American continental plate (120°W) and from 40°N to 45°N. The tomographic inversion is a joint inversion for seismic structure and epicenter location using both the body wave and T-phase data. The model images the transition from oceanic to continental plate and the initiation of subduction of the Gorda plate. The discrepancy between event epicenters located using T-phase arrivals alone with the same epicenters located with P- and T-phase arrivals are analyzed to learn more about the process of T-phase generation.
An elastic wave diffusion theory for ocean crustal phase coda development
Authors: Odom Robert I. , Peyton Valerie I. , Mercer James A.
Published: October 2005

The seismic signals designated Po and So are oceanic crustal phases that can be recorded by hydrophones and ocean bottom seismometers. They are characterized by long high-frequency codas and by their efficiency of propagation. Many features of their propagation can be accounted for by considering water-sediment reverberation and fine random layering on the oceanic lithosphere. However, it appears that some range-dependent mechanism, perhaps forward scattering from rough surfaces, is necessary to completely describe the observed signals. An energy diffusion theory based on the coupled mode representation for the solution of the wave equation is described. The theory treats the diffusion of energy in spectral space in the strongly forward scattering limit, and may provide a realistic physical model for the development of the long Po/So coda. The energy diffusivity is derived directly from the continuum limit of the mode coupling matrix; it is proportional to the spatial autospectrum of the coupling matrix. The applicability of the theory requires that the mean free path for multiple scattering must be large compared to the size of the medium fluctuations, and the spatial scale of the heterogeneities must be large compared to the wavelength. [Work supported by ONR.]
The resolution of frequency and time following hair cell regeneration in birds
Authors: Marean G. Cameron , Rubel Edwin W.
Published: October 2005

Detection thresholds, auditory filter widths, and temporal modulation transfer functions were measured in European starlings before, during, and after a 10-day injection series of kanamycin, an ototoxic aminoglycoside antibiotic. Hearing loss in response to the drug exposure was observed in frequencies at or above 3 kHz; threshold shifts above 3 kHz were ≳60 dB. The auditory filter broadened at 5 kHz from 9% to 20% of center frequency (CF). After 60 days of recovery, detection thresholds improved to within 15 dB of predose estimates, and auditory filters at 5 kHz recovered to 11% of CF and were permanently changed in the skew toward lower frequencies. At 3 and 1 kHz, changes in filter bandwidths were small and transient. At 3 kHz, no permanent change in filter width occurred, but filters were permanently skewed toward lower frequencies. At 1 kHz, changes in skew occurred, but only during the period of greatest threshold shift at higher frequencies. Temporal resolution was largely unaffected by hearing loss, although some loss in sensitivity to amplitude modulation was observed during the period of profound hearing loss. The data are discussed in terms of the relation among auditory functions and the perception of birdsong by starlings after hair cell regeneration.
Classification of whale song units using a self-organizing feature mapping algorithm
Authors: Mitsakakis Nicholas , Fisher Robert , Walker Ashley
Published: October 2005

Humpback whales produce prolonged vocalizations consisting of long fixed patterns of sound—elements of which are repeated with characteristic accuracy. The first known hydrophone recordings of these songs were made in 1952, but no objective technique of song classification is widely established. Toward this aim, an artificial neural network algorithm for the extraction and description of basic sound units is being developed. Samples of whale songs are converted into sonogram matrices whose rows correspond to frequencies on a logarithmic scale and whose columns are elemental time slices. Matrix values are quantified sound energy levels. Data preprocessed in this way is used to train a self-organizing feature mapping network which clusters the sounds into an ordered map of acoustic space. Comparison of the representative sound units extracted and encoded in this map is made with similar data (i) classified using human visual and aural impressions and (ii) traditional statistical clustering algorithms.
Investigating acoustic localization using artificial ears
Authors: Walker Ashley , Hallam John , Webb Barbara
Published: October 2005

Physical modeling is a technique wherein sensorimotor mechanisms believed to underlie animal behavior are mimicked using functionally analogous transducers and electromechanical circuitry. Because physical models inhabit the same environment as animals, they allow biologists to examine more realistic environmental interactions. In turn, physical modeling can enable engineers to discover the general principles underlying robust, adaptive sensorimotor control of robots. Two acoustic localization mechanisms are being physically modeled: cricket phonotaxis and echolocation by constant frequency emitting bats. (1) The function of the cricket trachea was modeled by connecting the output of two miniature microphones to a circuit measuring the relative intensity and binaural phase shift of a received call. Using only tracheal phase cancellation and latency comparison, a robot bearing this sensor obtains directional information enabling it to approach only those sounds with the right (frequency and envelope) structure. (2) An artificial echolocation system was built using a continuous, pure-tone-emitting transducer and a pair of receivers mounted on the pan/tilt head of a robot. Directional cues contained in echoes reflected from moving targets—interaural intensity disparities and temporal differences in the echo modulating waveforms—are used to orient the robot toward these targets.
Understanding humpback whale sonar: A physicist’s view
Authors: Frazer L. Neil , Mercado Eduardo , Tolstoy Alex
Published: October 2005

Just as beamforming matched filter sonar (BMF) provides a simple model for the sonar of bats and dolphins, so do recently developed matched-field processing sonars (MFP) provide simple models for the sonar of humpbacks and other mysticetes. This talk reviews the principles of MFP sonar and the behaviors essential to its use. As BMF is optimal for locating small, nearby, rapidly moving targets (potential prey), so is MFP sonar optimal for locating large, distant, slow-moving targets (potential mates). While BMF uses mainly the direct echo from a target, MFP sonar uses the complete reflected wavetrain, matching the latter with the convolution of the source and a set of empirical Green’s functions. MFP sonar requires lower frequencies, more power, and longer listening times than BMF sonar, which is why humpback sound sequences consist of long patterns of regularly spaced sweeps rather than the click trains of odontocetes. Observations of dolphins show their expertise at BMF; similarly, the careful acoustic and visual observations of humpbacks by Payne, Tyack, Herman, Frankel and others show the expertise of humpbacks at MFP sonar. Their observations suggest that when a singer continues to sing after being joined by a nonsinger, the joiner is likely an immature male learning to echolocate; also, the rapid convergence of humpback whale song is a trait selected to impede the use of singer echoes by nonsinging males.
Two-dimensional streamlines obtained from color coded Doppler image
Authors: Ohtsuki Shigeo , Tanaka Motonao
Published: October 2005

The ultrasonic colored Doppler image is convenient to observe blood flow in the human heart. This image displays the velocity component in the direction of the ultrasonic beam. Therefore, it is difficult to point out the existence of vorticity in the flow. An extended stream function method is being developed in order to show streamlines over the colored Doppler image. The Doppler velocity in the image is the local velocity component governed under rules of fluid dynamics. Considering this, two-dimensional velocity components were estimated in the observing plane appearing as the colored Doppler image. Clinical data show that vortexes in blood flow play very important roles in the behavior of the mitral valve in the heart.
Deep localized hyperthermia through the rib cage using ultrasound heating patterns
Authors: Botros Youssry Y. , Volakis John L. , Ebbini Emad S. , VanBaren Phillip D.
Published: October 2005

In this paper, a novel hybrid approach for treating deep localized tumors through strong obstacles (e.g., the rib cage) using ultrasound phased arrays is presented. In view of the large problem wavelength dimensions, high-frequency techniques such as ray acoustics and diffraction techniques are used. In particular, a ray method is employed to propagate the ultrasound fields from the feeding array to the frontal plane of the rib cage where these fields are considered as the primary sources for the region below the ribs. The Rayleigh–Sommerfeld diffraction integral is then used to determine the fields in the lower region interior to the rib cage. The pressure-velocity relation is finally put into matrix form and the pseudo-inverse technique is employed to synthesize the heating pattern required for hyperthermia. The intensity levels over the solid ribs are also examined, as well as the field map under the hard obstacles, to ensure that the synthesized pattern satisfies the desired specifications. Experimental results are given which are in excellent agreement with the computational model and serve to validate the methodology. [Work supported by the National Institutes of Health.]
Deviation from plane-wave condition on precise ultrasound speed measurement
Authors: Behnam Hamid , Ohtsuki Shigeo , Tanaka Motonao
Published: October 2005

Sound-speed measurement in various materials is widely used for getting information about their elasticity and density. It has already been used in many researches to evaluate different biological tissue conditions and for distinguising the normal and diseased tissues. For these purposes it is necessary to implement a precise measurement, reducing the error sources. A sound wave produced by a real (finite size) transducer does not propagate completely as a plane wave. Calculation is done for both a planar circular transducer and a concave circular transducer, considering the uniform vibration velocity and burst pulse activation. The effect of nonplanar transmission in every point of the sound field is an amplitude change and a phase change. The phase change will cause a time shift on ultrasound pulses that will cause some errors in the transmission time measurement. The results are shown that, for the same transducer size and frequency, this effect is more serious for a concave transducer than a plane transducer, and this effect should be considered for measuring the sound velocity with precision better than 0.1%.
Visually handicapped pedestrians and the sound environment: Developmental change of the use of auditory information
Authors: Ota Atsushi , Tamura Akihiro , Kashima Noriaki
Published: October 2005

The visually handicapped, who rely on auditory information, are supposed to take the sound environment in greatly different ways than the nonhandicapped. A survey was conducted about the developmental change of the use of auditory information for the visually handicapped. The purpose of this study is to create a better sound environment for the visually handicapped and the nonhandicapped to live in together. Interviews with 13 visually handicapped students (9–18 years old) and 19 visually handicapped adults were conducted to investigate how they use the auditory information. Interviewees who had little experience in walking around could hardly recognize the surrounding space by making use of the auditory information. They seemed to walk and to move in the behavioral patterns using their own specific information. It was found that they actively used the auditory information to avoid danger, for example, sounds from cars. On the other hand, those who had much experience used the auditory information to recognize stores and houses on a street. They used the auditory information to avoid danger unconsciously. In addition, some of them reported that they often had two-dimensional mental maps and put landmarks on the maps using the auditory information.
Influence of the air absorption and ground effect on aircraft noise
Authors: Makarewicz R.
Published: October 2005

The sound exposure level is calculated for a level flight. The aircraft is assumed to be a nondirectional point source and its power spectrum similar to the ‘‘typical power spectrum’’ given in Noise and VibrationControl Engineering [edited by L. L. Beranek and I. L. Ver (Wiley, New York, 1994)]. The equivalent absorption coefficient was calculated for different weather conditions, i.e., temperature and relative humidity (ANSI S1.26-1995). The ground attenuation is incorporated using the far-field approximation of the Weyl–Van der Pol solution [K. Attenborough, Appl. Acoust. 24, 289–319 (1988)] and the dependence upon the grazing angle [Lee et al., J. Sound Vib. 145, 111–128 (1991)]. The free parameters of the model can be found by measurements of the sound exposure level. The model has been developed as much for its relative simplicity as to save computer time. It seems that the theory yields reasonably good estimates for aircraft noise.
Aircraft noise rating by A-weighted sound exposure level, sidewise 1000 ft
Authors: Young Robert W.
Published: October 2005

The U.S. Marine Corps scheduled demonstration helicopter flybys for 7 and 8 December 1995 over the City of Del Mar, CA, and Torrey Pines State Reserve to the south, and other cities also. Residents were invited to comment on noise; this paper is based on my measurements and comments. City of Del Mar Regulation 9.20.03 provides that the 1-h average sound level beyond the property on which noise is produced shall not exceed 50 dB, from 7 a.m. to 10 p.m. Noise at Torrey Pines was monitored continuously for 10 days. During the scheduled times on 7 and 8 December there were fourteen 1-h average sound levels greater than 55 dB; during 7 of those hours, the 1-h average sound level was greater than 60 dB. The Torrey Pines monitoring site was about 2500 ft from the Seawolf track south of Del Mar, on which some of the helicopters flew at a scheduled altitude of 1000 ft outbound, 500 ft inbound. To provide a common basis for comparison, measurements were interpreted to yield the A-weighted sound exposure level (SEL) at a sidewise distance of 1000 ft from a helicopter. For the CH46E helicopter the typical SEL was 90 dB; for the CH53E helicopter, it was 97 dB.
A numerical study of general aviation noise abatement procedures: Correlations between energy costs and environmental benefits
Authors: Norgia L.
Published: October 2005

The increasing public demand for air transportation has brought both airlines and airport authorities to a serious consideration of the environmental impact particularly for the nuisance caused by noise in the airport surroundings. This in turn has moved the airlines to study and possibly adopt modified LTO procedures which could alleviate the acoustic impact on the ground and provide the benefit of reduced landing fees. When evaluating such alternative procedures, the extra cost to be faced for engine utilization at a higher severity factor must be considered with great attention. This work, supported by Alitalia, describes a simulation done with the Cira acoustical model. A single-point calculation method has been used which was prepared to optimize noise abatement procedures, and to evaluate an energy costs analysis for each takeoff profile. The fuel consumption and noise reduction benefits of three noise abatement procedures are compared with the standard procedures. The analysis consists of determining the fuel consumed in each segment defined by changes in airplane configuration, engine thrust, or speed. Results show that extra fuel is consumed in each of the noise abatement procedures; the magnitude of fuel penalty is aircraft-dependent. This numerical method has been used to define an ‘‘ecological’’ procedure to reduce noise impact on German airports.
Evaluating synergetic noise effects using a combined socioacoustical and psychoacoustical method: A field and laboratory study
Authors: Schulte-Fortkamp Brigitte
Published: October 2005

Research into environmental noise effects and noise judgments has repeatedly shown that, in addition to judging single noise units, several other evaluation patterns seem to play a role. However, it is yet unclear which noise components of a given synergetic background noise will be of primary importance to an individual. In an interdisciplinary socio- and psychoacoustic field and laboratory study on noise effects on residential areas, different combinations of synergetic environmental traffic noise were evaluated. It is intended to develop an appropriate listener- and annoyance-oriented instrument for characterizing acoustic immissions as to the particular annoyance and interference potentials, ascribed to them by the inhabitants. The fundamental methodical principle of the present research design hinges on repeated reconstruction of the interrelations holding among the various different quantitative and qualitative data sets. These data sets relate to the research subject noise annoyance on three distinct levels: to the different social and environmental realities and subjective lifestyles of persons living in different residential quarters; to externally recorded and standardized noise immissions, and to judgments and characterizations of noise events, including a detailed analysis of psychoacoustic parameters and noise immissions.
Estimation of equivalent sound level by invoking a neural net
Authors: Imai Kanenori , Hayashi Akinori , Kuno Kazuhiro , Ikegaya Kazuo
Published: October 2005

The equivalent sound level Leq for road traffic noise is estimated using two models. One is a nonlinear neural model in which the transformation sometimes becomes analytical when it is expanded to a series. Therefore, the output function of the net is examined, and a means of partitioning the data for learning and evaluation is described. The other model is a prediction equation in which the decay due to distance is added to the unit pattern based on an expression derived from Poisson traffic flow. The variables included in the equation are then selected as inputs to the net, and learning is evaluated. The output of the net is compared with the results of the prediction equation. The neural net learns functional relations with relatively little polarization, and predictions are easily made since the data are partitioned. The degree of prediction errors is approximately the same for both the equation and the neural net.
Is sonochemistry able to give information about the so-called extreme conditions that prevail in collapsing bubbles?
Authors: Reisse Jacques
Published: October 2005

In order to obtain information about the physical conditions that prevail in collapsing bubbles, we can use two different types of experiments: sonoluminescence measurements and sonochemical measurements. Sonoluminescence and sonochemistry must in some way be interrelated but this interrelation is far from obvious. Indeed, the detectable products of a sonochemical reaction are rarely the products directly formed during the bubble collapse. They are the final products of a series of different steps which are generally not known. This issue will be discussed on the basis of quantitative sonochemical experimental results obtained in Brussels at two different frequencies (20 kHz and 1.7 MHz), using pulsed and continuous pressure waves. Special emphasis will be put on the time evolution of a chemiluminescent system during and after a pulse of ultrasound or during a pulses series. The evolution of the system was followed by pressure intensity measurements, light diffusion measurements, and luminescence measurements.
Temperature and pressure during acoustic cavitation
Authors: Suslick Kenneth S. , McNamara William B. , Didenko Yury
Published: October 2005

Acoustic cavitation results in extraordinary transient conditions inside the collapsing bubble. In addition to interesting chemical effects (sonochemistry), cavitation also produces light emission. Such sonoluminescence from cavitating clouds of bubbles (‘‘multibubble sonoluminescence,’’ MBSL) in room temperature liquids closely resemble flame emission, and this has been used to measure the effective temperature and pressure of species formed during cavitation. Effective emission temperatures have been obtained for MBSL from both excited state C2 emission (from sonolysis of hydrocarbons and silicone oil) and from excited state metal atom emission (from sonolysis of several volatile metal carbonyls). Effective pressures can be obtained from line broadening and line shifts of the metal atom emission. The effective transient conditions formed during cavitation of bubble clouds are ∼5000 K, ∼1700 atm, which implies heating and cooling rates in excess of 1010 K/s. Temperatures reached during single bubble sonoluminescence (SBSL) are likely to be very much higher. Differences between MBSL and SBSL will be discussed. The chemistry generated by cavitation hot spots often differs from either ordinary thermal or photochemical processes, and sonochemistry represents a fundamentally unique interaction of energy and matter. [Work supported by NSF.]
Enhancement of sonochemically active cavitation by second-harmonic superimposition
Authors: Umemura Shin-ichiro , Kawabata Ken-ichi , Sasaki Kazuaki
Published: October 2005

Acoustic cavitation is known to be the primary mechanism of subharmonic acoustic emission, sonoluminescence, and sonochemical effects. Recently, it was found that sonochemically active cavitation is significantly enhanced by superimposing the second harmonic to the fundamental in ultrasonic exposure. Second-harmonic superimposition lowered the intensity threshold for inducing iodine release as well as subharmonic emission in an aqueous iodide solution and expanded the sonochemical reaction rate by an order of magnitude. It can reduce the intensity threshold for sonochemically active cavitation in a progressive wave field to the same order of magnitude as that in a standing wave field at a single frequency. It also lowered the in vivo intensity threshold for producing focal liver tissue damage paired with subharmonic emission by an order of magnitude especially with a systemic administration of a certain sonodynamically active agent. These effects were partly explained by theoretical analysis of the rectified diffusion of gas molecules into a microbubble under acoustic pressure with second-harmonic superimposition. Focused ultrasound with second-harmonic superimposition in combination with an administration of a sonodynamically active agent may have potential use for selective tumor treatment, which may be termed as ‘‘sonodynamic therapy.’’
Acoustic coaxing of microimplosions for chemical-free deinking of paper
Authors: Madanshetty Sameer I.
Published: October 2005

Deinking remains an important step in environmentally conscious manufacturing of paper. A novel method based on acoustic-coaxing-induced microcavitation is presented for deinking of xerographic ink from paper. Microcavitation evolves microimplosions which are effective in deinking. Acoustic coaxing is an acoustic mediation that enables one to control the onset, intensity, and evolution of acoustic microcavitation. Acoustic microcavitation is brought about by low-megahertz acoustic fields giving rise to micron-size bubbles that live a few microseconds. Liquid-borne microparticles when exposed to strong sound fields will not, ordinarily, cause any cavitation. However, if in addition to this sound field there exists even a very weak, high-frequency auxiliary acoustic field, cavitation by the microparticles is readily facilitated. This technique of facilitating cavitation is referred to as ‘‘acoustic coaxing.’’ Acoustic-coaxing methods for deinking are a chemical-free, environmentally responsible means of recycling paper. Here, initial experimental results are presented and the technique is elaborated upon in detail for easy implementation. Preliminary results indicate that the paper fibers are entirely undamaged, and the ink separation leaves them immaculately white. The microimplosions appear to occur preferentially at the ink sites.
Nonlinear forced oscillations of vapor bubbles
Authors: Prosperetti Andrea , Oguz Hasan , Pan Yu
Published: October 2005

Evaporation and condensation provide a restoring force for the spherical oscillations of vapor bubbles. Unlike gas bubbles, the existence of this force is critically dependent on finite-rate processes, a fact that endows vapor bubbles with unusual properties such as two linear resonance frequencies. This paper extends the known linear results into the nonlinear domain by numerical simulation. The effects of forcing frequency, system pressure and temperature, and oscillation amplitude are studied. Particular attention is devoted to bubble behavior near the anomalous second resonance. The motivation for this work is offered by the possibility of using pressure radiation forces to remove boiling bubbles from hot surfaces in microgravity. [Work supported by the National Aeronautics and Space Administration.]
Nonlinear shape oscillation dynamics of drops and bubbles in a liquid
Authors: Trinh Eugene H.
Published: October 2005

Ultrasonically trapped centimeter-size liquid drops and gas bubbles in a liquid host are driven into large amplitude shape oscillations by modulating the acoustic radiation pressure. Some of the nonlinear characteristics have been experimentally investigated by measuring the resonant mode frequencies dependence on the oscillation amplitude, and by evaluating the energy coupling between some of the low-order resonant modes. The effect of the ultrasonic trapping field required for ground-based studies has become an issue in terms of its impact on the measured parameters. Such a high-intensity sound field has been shown to dramatically affect both the equilibrium shape as well as the motion of the drops and bubbles surfaces. In order to quantitatively evaluate the impact of such high field effects, simple experiments to be performed in low gravity will be described. [Work funded by NASA.]
A study of wave propagation in varying cross-section waveguides by modal decomposition. Part I. Theory and validation
Authors: Pagneux V. , Amir N. , Kergomard J.
Published: October 2005

The propagation of acoustic waves in waveguides with variable cross section is considered using multimodal decomposition. The approach adopted is to construct two infinite first-order differential equations for the components of the pressure and the velocity projected over the normal modes. From these an infinite matricial Riccati equation is derived for the impedance matrix. These equations are ordinary differential equations that can be integrated after truncation at a sufficient number of modes and take into account the coupling between modes. The stiffness of the pressure-velocity equations induced by the presence of evanescent modes is avoided by first calculating the impedance matrix along the guide. The method is checked using different examples where the solutions of the plane-wave approximation or the finite element method are known. Results show the method provides simple and accurate means to obtain the acoustic field with correct boundary conditions in a nonuniform guide with no restriction on the flare.
Near-field acoustic levitation of planar specimens using flexural vibration
Authors: Hashimoto Yoshiki , Koike Yoshikazu , Ueha Sadayuki
Published: October 2005

In conventional acoustic levitation, the specimens to be levitated are limited to very light ones of a few milligrams to a few tens of milligrams. The authors have learned that specimens with a weight of several kilograms can be levitated stably by direct sound radiation pressure. The specimen material is not important. The requirement is only that the surface of the specimen exposed to the sound wave must be flat. The fundamental characteristics of near-field levitation were experimentally studied with the use of a flexural vibration plate. The following results were obtained: (1) The size of levitation specimen should be longer than 3/2 wavelength of the flexural vibration in order to levitate stably. (2) The relationship between the levitation distance and the mass per unit area is proportion to −1/2 power. (3) The levitation distance is proportional to the displacement amplitude. This phenomenon can be used in noncontact transportation of planar objects such as Si wafer and glass plates.
The effect of receiver size on nonlinear pressure field measurements
Authors: Baker A. C. , Ward B. , Humphrey V. F.
Published: October 2005

The nonlinear pressure field generated by an ultrasonic source many wavelengths in diameter is studied experimentally and theoretically using two different size receivers. One receiver is sufficiently small to be considered infinitesimal at most positions in the pressure field while the other receiver has a diameter equal to that of the source. Theoretical predictions are made using a numerical solution of the KZK equation and these show that the large receiver virtually eliminates the pressure field fluctuations normally observed with a small receiver along and across the acoustic axis. To a large extent the axial field observed with the large receiver resembles a plane-wave field. The predictions are compared with experimental measurements obtained with a plane piston transducer (38-mm-diam, 2.25-MHz center frequency) as a source, and hydrophones 1 mm and 38 mm in diameter. Good agreement is seen between experiment and theory.
Effects of transverse isotropy on modes and mode coupling in shallow water
Authors: Odom Robert I. , Park Minkyu , Mercer James A. , Crosson Robert S. , Paik Pauline
Published: October 2005

Most marine sediments exhibit transverse isotropy (TI) that can have a significant effect on the signal properties of strongly bottom interacting sound. Locally, transverse isotropy has the greatest effect on the fundamental and near fundamental modal overtones. The local shallow water TI modes have reduced amplitude in the sediment relative to the corresponding shallow water modes for an isotropic bottom. Even a small departure from isotropy (2.4%) can have a significant (15%) effect on the phase velocity of bottom interacting modes. Calculations of mode–mode coupling coefficients for a range-dependent medium indicate that mode coupling is more strongly confined to modal nearest neighbors for a TI medium characterized predominantly by shear wave anisotropy, when compared to the corresponding isotropic medium. As the frequency increases, the strongest coupling occurs between higher overtones and also becomes more strongly peaked around nearest neighbors. The coupled mode theory of Maupin [Geophys. J. 93, 173–185 (1988)] is employed to model the coupling. This theory can treat smooth gradients and sloping layer boundaries for all five of the bottom elastic moduli in a TI medium, the densities, and the range dependence of the water column itself. This coupled mode formulation also properly accounts for the continuity of stress and displacement boundary conditions in an exact way at irregular interfaces.
Ultrasonic tomography using curved ray paths obtained by wave propagation simulations on a massively parallel computer
Authors: Schechter R. S. , Mignogna R. B. , Delsanto P. P.
Published: October 2005

Current ultrasonic tomography methods do not properly handle cases involving large refraction, mode conversion, strong scattering, or finite apertures. To account for these different effects, a method has been developed utilizing a very efficient code to model elastic wave propagation on a massively parallel computer. The computation also determines in a detailed way the ray paths of first arrival acoustic energy through solids even with strong scatterers. By using these fast parallel forward and ray path codes as part of an iterative tomography algorithm (ART), a major improvement is obtained over using straight-line ray paths. In addition, the wave propagation approach permits improved tomographic reconstructions in cases having large changes in the refractive index (≳10%), where traditional ray-tracing methods, based on the geometrical acoustics approximation, become numerically unstable. The entire tomography computation required is immense, but is feasible because the code is highly parallel and is implemented on a parallel supercomputer.
Modeling of the seat dip effect using the finite-difference time-domain method
Authors: LoVetri Joe , Mardare Doru , Soulodre Gilbert
Published: October 2005

In this paper the use of the finite-difference time-domain technique for the modeling of the seat dip effect in concert halls is demonstrated. The linear time-domain acoustic partial differential equations are discretized using a finite-difference technique. The second-order accurate differencing scheme is time–space centered, and the velocity and pressure are solved on an interlaced mesh. First- and second-order Mur absorbing boundary conditions, originally formulated for electromagnetic problems, are adapted to the acoustics case and used to truncate the numerical grid. The technique is first verified by comparing the numerical results to the analytic solution of a simple point source. Results from computer simulations of the seat dip phenomena are compared with the findings of previous studies where measurements had been made on scale models and in real concert halls. The computer model successfully predicts the effects associated with the source–receiver distance, the height of the receiver, and the height of the source.
A comparison of t test, F test, and coherence methods of detecting steady-state auditory-evoked potentials, distortion-product otoacoustic emissions, or other sinusoids
Authors: Dobie Robert A. , Wilson Michael J.
Published: October 2005

Sinusoids in background noise can conveniently be detected using unsegmented power spectra, comparing power at the signal frequency to average power at several neighbor frequencies. In this case, the F test is preferable to t tests based on rms or dB values, because of the skewed distributions of rms and dB when signal-to-noise ratio (SNR)=0. F-test performance improves as the number of frequencies increases, to about 15, but can be degraded if the background noise is not white, with a slope exceeding about 10 dB for the range of frequencies sampled. Segment analysis, using magnitude-squared coherence (MSC) or related statistics, has equivalent statistical power; MSC and F each yield unbiased SNR estimates that have identical distributions when SNR=0. Selection of F or MSC for detection of sinusoids will usually be a matter of convenience.
The effects of reverberant blast waves on the auditory system
Authors: Ahroon William A. , Hamernik Roger P. , Lei Sheau-Fang
Published: October 2005

Chinchillas were exposed to 1, 10, or 100 reverberant impulses at 150, 155, or 160 dB peak SPL. The impulses were generated by one of two different shock tubes, each producing blast waves having a different spectral composition, with one emphasizing low frequencies (<0.5 kHz) and the other midfrequencies (2–4 kHz). Impulses were presented at the rate of one per minute. This parametric paradigm yielded 18 exposure conditions with 15 animals/condition. Hearing thresholds were measured using auditory-evoked potentials and the sensory epithelium was evaluated with the surface preparation. In general, trauma increased as the total energy of the exposure, determined by the peak SPL and number of presentations, increased. The dependent variables (permanent threshold shift and sensory cell loss) varied in an orderly fashion across frequency as the peak and number of presentations were increased for both blast wave sources. There were, however, consistent differences between the effects of the low- and high-frequency energy ‘‘content’’ blast waves. Correlations between the dependent variables and the energy of exposure were highest for P- or A-weighted energies [Patterson et al., J. Acoust. Soc. Am. 93, 2860–2869 (1993)].
Release from upward spread of masking in regions of high-frequency hearing loss
Authors: Nelson David A. , Schroder Anna C.
Published: October 2005

The upward spread of masking was compared for 500-Hz quasifrequency-modulated (QFM) and sinusoidally amplitude-modulated (SAM) maskers. The modulation rate was 20 Hz. These maskers had identical magnitude spectra but different envelopes, which were relatively flat for the QFM masker and strongly fluctuating for the SAM masker. At signal frequencies more than an octave above the masker, masked thresholds for the SAM masker were lower than for the QFM masker, revealing ‘‘masking release’’ (QFM-SAM masked threshold differences) exceeding 30 dB in normal-hearing ears. In ears with high-frequency sensorineural hearing loss, but normal hearing in the region of the masker, masking release was markedly reduced or completely absent in regions of hearing loss. The data were evaluated with a model of masking based on the linearized response growth (LRG) of basilar membrane transfer functions associated with cochlear damage in animals. The LRG model predicted more gradual slopes of the growth of masking and reduced amount of masking in regions of hearing loss. The reduced masking release seen in regions of hearing loss could be largely accounted for by a more rapid growth of response to the probe tone in regions of hearing loss.
Effects of masker gating for signal detection in unmodulated and modulated bandlimited noise
Authors: Hall Joseph W. , Grose John H. , Hatch Debora R.
Published: October 2005

Thresholds for a 400-ms 1000-Hz pure-tone signal were obtained as a function of masking noise bandwidth for unmodulated and square wave modulated masking noise. Rates of modulation were 10 and 40 Hz. Noise bandwidths were 128 Hz, 387 Hz, 921 Hz, and 1505 Hz. The masking noise was either continuous or gated on and off with the signal. In general, signal thresholds were relatively constant as a function of noise bandwidth in unmodulated noise, and improved as a function of increasing noise bandwidth in modulated noise. Noise gating had little or no effect on signal threshold in unmodulated noise. At the 10-Hz modulation rate, signal thresholds were somewhat higher in gated than in continuous noise at relatively narrow noise bandwidths, but thresholds were similar in gated and continuous noise for relatively wide noise bandwidths. At bandwidths of 387, 921, and 1505 Hz, comodulation masking release (CMR) was calculated as the unmodulated noise threshold minus the modulated noise threshold, corrected by the difference between the unmodulated noise threshold and the modulated noise threshold at the 128-Hz bandwidths. At wide masker bandwidth, CMRs were higher for gated noise than for continuous noise. This was due almost entirely to the threshold gating effect found in the 128-Hz bandwidth condition. These results suggested that there was a within-channel effect for gated noise thresholds to be higher than continuous noise thresholds, but essentially no across-channel effect of gating. At the 40-Hz modulation rate, signal thresholds were similar for gated and continuous noise at all noise bandwidths. There was a very small but significant effect for the gated noise threshold to be lower than the continuous noise threshold at the widest noise bandwidth. It was speculated that this effect may be related to a decrease in sensitivity to modulation with continuous stimulation. In general, effects of gating appear to be small or absent for across-channel masking release in broadband modulated masking noise.