bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement and correlation of acoustic cavitation with cellular bioeffects
Authors: Hallow Daniel M. , McCutchen Todd E. , Mahajan Anuj D. , Zarnitsyn Vladimir G. , Prausnitz Mark R.
Published: October 2013

Noninvasive methods to measure and predict ultrasound effects on cells are needed to realize applications of ultrasound-mediated drug delivery to improve chemotherapy, gene therapy and targeted delivery. This study tested the hypothesis that (i) cellular bioeffects of ultrasound correlate with cavitation dose, (ii) broadband noise provides a measure of cavitation dose, and, thus, (iii) cellular bioeffects can be predicted by noninvasively measuring broadband noise. After exposing cell suspensions to ultrasound and measuring intracellular molecular uptake and loss of cell viability (bioeffects), a broad range of bioeffects were achieved by varying frequency, pressure, exposure time, cavitation nucleation site (Optison) concentration, and cell type. As a measure of cavitation activity, broadband noise measurements from acoustic spectra were collected during cell sonication and shown to be larger at elevated pressure and, after a high initial value, sharply decayed to a constant, background value at long exposure times. Combining these results, we found that broadband noise correlated well with molecular uptake and viability over the broad range of experimental conditions used (p-value <0.0001). This indicates that acoustic spectrum analysis provides a unifying parameter to correlate with bioeffects over a wide range of acoustic and experimental conditions. [Work supported by NIH, EKOS, DoEd GAANN Program.]
Microbubble contrast agents in vibro-acoutography
Authors: Manilal Prasika , Al-Jumaily Ahmed , Fatemi Mostafa
Published: October 2013

The use of contrast agents is becoming a routine practice in diagnostic ultrasound imaging. Microbubble contrast agents are proving to be a safe and practical way of enhancing conventional ultrasound images. This paper discusses the concept of using microbubble contrast agents in the vibro-acoustography (VA) technique. A brief background of microbubbles and their clinical applications is given as well as a summary of the different attempts at modeling microbubble contrast agents in ultrasound fields. A general Keller–Herring equation is modified to mathematically model the interaction of encapsulated microbubbles in blood with VA ultrasound. The frequency response and scattered pressure of microbubbles with initial radius of 1 and 3 m are presented. This method is accurate for pressure amplitudes up to 500 kPa. Understanding this interaction is important for the correct interpretation of clinical investigations when using VA.
Finite difference time domain simulation of nonlinear ultrasonic pulse propagation
Authors: Fukuhara Keisuke , Morita Nagayoshi
Published: October 2013

The extracorporeal shock wave lithotripsy has come into wide use rapidly owing to its advantage of non-invasiveness. However, as for the shock wave propagation in the human body in relation to practical lithotripsy, reports of numerical simulation based on models conforming to a practical situation are very few. In this paper, excited pulse wave forms are measured by using a water tank model based on a practical lithotriptor and numerical simulation is made on the basis of these measured data. A new FDTD algorithm is proposed and used for this simulation, the problem being connected with extracorporeal shock wave lithotripsy. In this simulation method, conventional plane wave approximation is not used but original equations including convection terms are directly employed to derive new FDTD algorithms. This method is applied to an experimental setup and its numerical model that resemble an actual treatment situation to compare sound pressure distributions obtained numerically with those obtained experimentally. It is shown that the present method gives clearly better results than the earlier method does, in the viewpoint of numerical reappearance of strongly nonlinear wave forms.
Pressure calibration of MEM microphones
Authors: Wong George S. K.
Published: October 2013

Micro-electro-mechanical microphones (MEMS) are micro devices approximately 4×6×1.5 mm in size, with relatively low sensitivities (typically −40 dB re 1V/Pa) and operate to ultrasonic frequencies. However, the calibration of these microphones has been a challenge to most Metrology Institutes. One obvious route is to perform a free-field calibration. This presentation will discuss a preliminary coupler design for pressure comparison calibration of microphones to frequencies as high as 80 kHz.
Experiments on redirection of organ pipe sound by coupling
Authors: Kleiner Mendel , Scholz Matthias , Yokota Munetaka
Published: October 2013

It is well known among organ builders that the sound of an organ pipe may be influenced by the addition of closely tuned pipes in the vicinity of the pipe. Rather than being a result of absorption of sound it is hypothesized that the effect is due to the sound being redirected due to coupling between pipes, similar to the coupling between elements in a Yagi antenna array. Measurement results will be shown and discussed. [Work supported by RPI and Chalmers University of Technology.]
A parabolic equation solution for advected acousto-gravity waves
Authors: Bruch Jeremy , Collins Michael D. , Dacol Dalcio K. , Lingevich Joseph F. , Siegmann William L.
Published: October 2013

It is relatively difficult to account for advection in parabolic equation solutions. An effective solution was recently derived for the acoustic case [J. Acoust. Soc. Am. 111, 729–734 (2002)]. This work is currently being extended to include buoyancy effects. In the initial study, emphasis is placed on wave numbers near the Lamb wave, where buoyancy and compressibility both have a significant effect. An approximate parabolic solution is derived and tested for range-indendent cases using a spectral solution. The limiting cases of small ambient flow and/or no gravity are compared to the extended result for consistency. [Work sponsored by the ONR.]
The theory of the generation of atmospheric microbaroms
Authors: Waxler Roger , Gilbert Kenneth E.
Published: October 2013

It is well known that the standing wave components of large ocean wave systems, such as those produced by storms, radiate infrasound (microbaroms) into both the ocean and the atmosphere. The radiated sound is found in a narrow band (from 0.2 to 0.3 Hz wide) centered near 0.2 Hz. It is also well known that the radiation mechanism is nonlinear since ocean-wave wavelengths are too short to directly radiate. A systematic theoretical study of the radiation mechanism has been undertaken. The model considered is the two-fluid system consisting of atmosphere (a very rare fluid) over ocean (a very dense fluid). The interface between the fluids is allowed to undulate. The equations of fluid mechanics are then solved to second order in Mach number. It is found that the physical mechanism for (as well as the mathematical form of) the radiation into the atmosphere is entirely different from that of the radiation into the ocean. In particular, the compressibility of the atmosphere plays a crucial role.
Height-of-burst influence on spectra emitted by small explosions
Authors: White Michael J.
Published: October 2013

Explosions in air nearby to the ground produce high-pressure waves that obey nonlinear superposition. The ground-reflected wave, when superimposed on the positive pressure phase of the direct wave, advances to merge in a mach stem. ANSI Standard S2.20 offers a correction factor applied to the real charge weight, to account for the increase in peak overpressure. Over a hard surface, the factor ranges from 2 near the ground to a maximum value of 5.6 at a scaled height (ratio of height to cube root of charge mass) equal to 3.9 m/[(kg)(1/3)]. We performed a set of experiments to measure the height-of-burst effect from explosions of composition C-4 over grass-covered ground at horizontal distances between 5 and 174 m. We offer an empirical analysis of the resulting spectra, and extend the height-of-burst analysis to far-field spectral sound power.
Variance of energy and energy density in statistical energy analysis of complex systems
Authors: Cotoni Vincent , Langley Robin
Published: October 2013

Standard statistical energy analysis (SEA) predicts the mean energy level in each subsystem of a complex system at high frequencies. The resulting energy is to be seen as averaged over an ensemble of similar systems (like nominally identical products coming off an assemble line). This prediction of the mean has been recently extended to the ensemble variance of the energy. The variance gives indications of how far from the ensemble mean can be the response of one particular member of the ensemble. Using few additional assumptions, the variance can be used to predict the confidence intervals around the SEA mean prediction, and can be extended to the variance of the response at a point (i.e., the energy density). Some numerical validations for several types of vibro-acoustic systems are presented.
Analysis of wave dispersion in cylindrical shells with anisotropic layers by Rayleigh–Ritz expansions
Authors: Magliula Elizabeth A. , McDaniel J. Gregory , Corrado Charles N.
Published: October 2013

Recent advances in composite materials offer the potential to dramatically affect the dispersions of helical waves that propagate in layered cylindrical shells. Effective choices and configurations of these materials require rapid dispersion predictions that take into account general anisotropy and variations of elastic variables through the thickness of each layer. This presentation describes a solution to this problem that is based on a previously developed theory [J. G. McDaniel and J. H. Ginsberg, J. Appl. Mech. 60, 463–469 (1993)] for the vibrations of cylindrical shells with isotropic layers. The approach uses propagating wave representations in the axial and circumferential coordinates. A series expansion with polynomial basis functions represents dependences on the radial coordinate and equations for the series coefficients are derived using the Rayleigh–Ritz method. These equations yield a dispersion relation that is solved for the complex-valued axial wavenumber at each frequency and circumferential harmonic. Examples illustrate the interface of this approach with optimization algorithms that identify layer designs possessing specified dispersion properties. [Work supported by ONR.]
Strategies used to increase speech clarity by normal-hearing children
Authors: Ide-Helvie Dana L. , McCleary Elizabeth A. , Sullivan Sarah C. , Lotto Andrew J. , Higgins Maureen B.
Published: October 2013

It is common among clinicians to ask children to produce their best speech during intervention. However, it is unclear whether children know how to make their speech clearer. The strategies used by children with and without hearing loss have implications for maximizing intelligibility and for understanding the development of communication competency. As a first step toward this understanding, children (7 to 12 years of age) with normal hearing were asked to read ten simple sentences. They were told that they were testing a new computer program designed to recognize speech. There was, in fact, no recognition program and each child received the same output feedback. After providing normal speech to allow the program to get used to their voices, they subsequently produced their best and then very best, very clearest speech in order to see how accurate the recognition program could be. Acoustic analyses (intensity, fundamental and first two formant frequencies for all vowels, as well as sentence, vowel, and VOT durations) were performed on recorded waveforms from each repetition in order to determine what the children were varying to comply with best speech instructions. The results demonstrate large individual differences in strategies and persistent gender differences. [Work supported by NIH.]
Processing microphone arrays for spatial selectivity in three dimensions
Authors: Flanagan J. L.
Published: October 2013

Reverberation degrades the performance of conventional beamformers. Matched-filter processing combats multi-path distortion and provides improved quality by utilizing signal information arriving from different paths. Implicit is spatial selectivity in three dimensions—which enables an array to ‘‘reach over’’ intervening sources of interference. The cost is arithmetic, storage, and a priori characterization of the enclosure. Source-to-receiver transmissions are described by impulse responses, which are employed in causal time-reversed form to accomplish matched filtering. Work conducted earlier for the National Science Foundation is summarized and demonstrated, along with a description of algorithms for automatic tracking of moving talkers. Array configuration and placement remain challenges in geometric optimization.
Sectorized beam-base adaptation for long line arrays
Authors: Cox Henry
Published: October 2013

Long line arrays of many elements present special problems for adaptive beamforming. The long travel time for an endfire signal to traverse the array requires the use of narrow frequency bins to avoid a significant phase change within a frequency bin. The narrow beamwidth near broadside makes the array sensitive to small bearing charges that occur within the coherent integration time so that adaptation must take place rapidly. These two effects combine to cause a snapshot-starved situation. A beam-based adaptation approach is suggested in which the first step is to form shaded conventional far-field beams. This is followed by a sectorized adaptive combination of beams in a sector to provide adaptive near-field and far-field beams. For a sector near broadside where the beams are very narrow and sensitive to motion but the travel time across the array is short, less temporal averaging and more frequency averaging is used. Near endfire, where the beams are wide but the travel is long, narrow frequency beams are used with longer temporal averaging. The approach is applied to the case of strong far-field interference masking a weak near-field signal. The approach is computationally efficient as well as providing improved snapshot support for adaptation.
Unified acoustic model for simulating propagation and scattering effects in oceanic waveguides
Authors: Tamendarov Ildar M. , Sidorovskaia Natalia A.
Published: October 2013

The paper addresses the recent developments of Shallow Water Acoustic Modal Propagation (SWAMP) model (http://www.ucs.louisiana.edu/∼nxs7560/swamp.html) to account for the scattering events along the acoustic signal propagation path. The theoretical and numerical aspects of SWAMP extension to model the acoustic pulse scattering by a spherical elastic shell in an inhomogeneous oceanic waveguide within the T-matrix approach are discussed. The algorithm utilizes the incident modal functions obtained by SWAMP for an empty waveguide in the spherical representation and the free-field T-matrix. The theoretical foundation for the approach is based on the work by Hackman and Sammelmann [J. Acoust. Soc. Am. 80, 1447–1458 (1986)]. The T-matrix calculations are implemented in MATLAB software. The interpretation of the scattering event as the modal transformation through the T-matrix is attempted. The numerical studies based on the new model are presented. [Work supported by the Louisiana Board of Regents Support Fund, Contract No. LEQSF(2001-04)-RD-A-38.]
Scintillation of short duration records
Authors: Lutz Steven , Culver R. Lee , Bradley David
Published: October 2013

We have investigated propagation of sound in the ocean using the theory of wave propagation in random media. The theory classifies specific source/receiver geometries as either unsaturated, partially saturated, or saturated. In the unsaturated regime the variance of the intensity fluctuations will generally be quite small such that the scintillation index is less than unity. The partially saturated regime can give rise to scintillation indices larger than unity. In the fully saturated regime the scintillation index asymptotically approaches unity. We have conducted an experiment in which the two-dimensional sound-speed field was measured directly using a towed CTD chain, and relatively short acoustic records were captured using a number of source/receiver pairs. The length scales and index of refraction variation place the experiment in the saturated regime. However, measured scintillation indices are much less than 1. We provide an explanation for this difference and utilize local current measurements to bring the theory into agreement with the data. Our results are applicable to operational sonar systems, where short duration records are ordinarily utilized to transmit information or detect targets. [Work sponsored by ONR Code 321US.]
Efficient computation of acoustical scattering from N spheres via the fast multipole method accelerated flexible generalized minimal residual method
Authors: Gumerov Nail A. , Duraiswami Ramani
Published: October 2013

Many problems require computation of acoustic fields in systems consisting of a large number of scatterers, which can be modeled as spheres (or enclosed by them). These spheres can have different sizes, can be arbitrarily distributed in three dimensional space, and can have different surface impedance. Solution of this problem via direct T-matrix approach [Gumerov and Duraiswami, J. Acoust. Soc. Am., 112, 2688–2701 (2002)] is practical only for relatively low number of scatterers, N, since its computational complexity grows as O(N3). We developed and implemented an efficient computational technique, based on an iterative solver employing a flexible generalized minimal residual method with a right preconditioner. Matrix-vector multiplications involving a large system matrix and the preconditioner are sped up with the aid of the multilevel fast multipole method. We tested the accuracy, convergence and complexity of the method on example problems with N∼104 (millions of unknowns). These tests showed that the method is accurate for a range of frequencies, and experimentally scales as O(N1.25). The method has substantial advantages in speed and convergence compared to the reflection method reported earlier [Gumerov and Duraiswami, J. Acoust. Soc. Am., 113, 2334 (2002)]. [Work supported NSF Awards 0086075 and 0219681, which are gratefully acknowledged.]
Acoustic intensity measurements involving forward scatter from prolate spheroids
Authors: Rapids Brian R. , Lauchle Gerald C.
Published: October 2013

Underwater acoustic measurements made by scalar pressure sensor are only able to provide an estimate of the magnitude of the total intensity associated with an equivalent plane wave. This equivalence is based upon an assumption that the relative phase between pressure and particle velocity is identically zero. True intensity sensors measure simultaneously the acoustic pressure and components of particle velocity (or related quantity such as acceleration, displacement, or pressure gradient) at a single coordinate in space. The measurement of both pressure and velocity provides the magnitude of acoustic intensity as well as the relative phase between acoustic pressure and velocity. Numerical computations of a steady-state acoustic field perturbed by the presence of a rigid spheroid indicate that the plane wave equivalence may not be a perfect assumption in certain bistatic geometries and that additional information regarding the total acoustic field can be observed only with true intensity sensors. A varnished prolate spheroid constructed from red oak was employed as part of an underwater scattering experiment. A dual axis p-a probe was employed at frequencies near 10 kHz to test the theoretical hypotheses. Theoretical and experimental results will be discussed. [Work supported by ONR, Code 321MS under Grant No. N00014-01-1-0108.]
Experimental and theoretical target strength of fluid filled spheres
Authors: Deveau David M.
Published: October 2013

Investigation into the scattering nature of surfaces or other physical objects often requires the use of measurement systems which cannot always be well controlled. This lack of control can be compensated for by calibrating the resulting measurements against a known target. While these targets can be any object, the goal is to use a target that has a stable scattering response and is independent of angle. The ideal shape is that of a sphere but even this can be improved with the addition of internal fluids that focus and temperature stabilize the scattering response. A scatter response model of a sphere has been developed and used to design four thin walled spheres, each with a different diameter and filled with a focusing fill fluid (Fluorolube). One pair of spheres was measured in an ocean environment while the second pair was tested in a controlled test tank from 5 to 50 kHz but using shorter continuous wave pulses. While the ocean measured spheres closely matched the model, the test tank measurements showed a marked difference from the model. Changes to the model will be explored to determine if theoretical minimums for pulse length are insufficient for targets of this density or focusing capability.
The influence of synthesized music on the expansion of trombone performance techniques
Authors: Plsek Thomas
Published: October 2013

Much of the development of synthesized music has been involved with the modeling of traditional acoustic sources such as strings, brass, woodwinds, and percussion. It has, of course, also been concerned with the creation of new, yet unheard, sounds and the modifications and manipulations of existing sources through signal processing. The author has been involved with these processes for many years as a trombone explorer, and has had to interact and integrate wth them. Much was discovered and learned about how trombone performance can be expanded to acoustically simulate these developments in electronic music. This paper demonstrates some of the techniques such as the real-time control of sound source location and the manipulation of timbre. In many instances the acoustical solution proved to be as, or even more, interesting as the synthetic process.
Design challenges for the integration of virtual acoustics in music practice rooms
Authors: Freiheit Ron
Published: October 2013

The use of virtual acoustics has provided a new level of practice experience for the musician. By integrating the sound isolation of music practice rooms with the signal processing of an active acoustic system (with time-variant gain before feedback), musicians can now benefit from the experience of practicing in multiple acoustic environments. The variability of the acoustic environment allows the musician to clearly hear their intonation and articulation, which may be difficult to discern in a small practice room. For the effective implementation of virtual acoustics in small spaces (typically 15 square meters) a number of technical issues had to be resolved including sound-field immersion, reducing input level due to proximity of the source to the microphone transducers, and a simplified system control allowing musicians to focus on the art of practice and not the technology. This paper deals with these issues and the subsequent design decisions to address them.
Directional sensitivity in bottlenose dolphins: Evoked potential study
Authors: Popov Vladimir , Supin Alexander
Published: October 2013

ABR threshold-versus-azimuth function was measured in two bottlenose dolphins. The measurements were done in a circular pool 6 m in diameter and 40 cm deep. The animal was supported by a stretcher, the head in the center of the pool. The transducer was moved around the animal’s head at the radius of 1.2 m. ABRs were recorded using electrodes mounted in suction caps fastened at the head surface. ABR thresholds were measured at azimuth of the sound source of ±90° from the midline and frequencies from 8 to 128 kHz. Both acuteness of the directional diagram and the lowest-threshold azimuth value depended on stimulus frequency. Acuteness increased with the frequency increase. The lowest-threshold azimuth was near midline at high frequencies and deviated laterally up to 45–60° with lowering the frequency. The maximum azimuth-dependent thresholds shift (20–35 dB) was at high frequencies (90–128 kHz); at lower frequencies (8–16 kHz), the azimuth-dependent threshold shift decreased down to 10–15 dB. [Work supported by the Russian Foundation for Basic Research.]
Internal- and surface-wave-induced fluctuations and frequency spreading in shallow water acoustic propagation over short ranges
Authors: Lynch Stephen D. , D’Spain Gerald L. , Terrill Eric
Published: October 2013

During a 2001 ocean acoustics experiment approximately 40 miles west of San Diego, a moored, underwater source at 30-m depth transmitted a set of narrow-band tones in the 100–1000-Hz band to a 32-element, 992-m-long bottom hydrophone array deployed from R/P FLIP. Also deployed about FLIP were multiple, fixed vertical thermistor strings with ambient pressure sensors, and CTD casts. These data provide observations of the effects of a fluctuating ocean environment on acoustics in shallow water (180 m) over short ranges (2.5 km). A series of very long fast Fourier transforms of the received signals reveal time dependence in the frequency spreading about the transmitted frequency. Time series of spatial and temporal coherence estimates show temporal variations in the relatedness of the received signals. The environmental data are used along with physics-based models of ocean surface and internal waves to predict the signal fluctuation and frequency spreading characteristics. Results of comparison of acoustic observations with oceanographic-data/model-based predictions under various assumptions will be presented. [Work supported by ONR, Code 321(US).]
Noise reduction for digital hearing aids
Authors: Hohmann Volker , Kollmeier Birger
Published: October 2013

The normal-hearing system extracts monaural and binaural features from the signals at the left and right ears in order to separate and classify sound sources. Robustness of source extraction is achieved by exploiting redundancies in the source signals (auditory scene analysis). ASA is closely related to the ‘‘Cocktail Party Effect,’’ i.e., the ability of normal-hearing listeners to perceive speech in adverse conditions at low signal-to-noise ratios. Hearing-impaired people show a reduced ability to understand speech in noisy environments, stressing the necessity to incorporate noise reduction schemes into hearing aids. Several algorithms for monaural, binaural and multichannel noise reduction have been proposed, which aim at increasing speech intelligibility in adverse conditions. A summary of recent algorithms including directional microphones, beamformers, monaural noise reduction and perceptual model-based binaural schemes will be given. In practice, these schemes were shown to be much less efficient than the normal-hearing system in acoustically complex environments characterized by diffuse noise and reverberation. One reason might be that redundancies in the source signals exploited by the hearing system are not used so far by noise reduction algorithms. Novel multidimensional statistical filtering algorithms are introduced that might fill this gap in the future. [Work supported by BMBF 01EZ0212.]
A new psychoacoustic fitting algorithm for digital hearing aids
Authors: Ih Jeong-Guon , Park Kyung-Hoon , Yoo Dong-Gu
Published: October 2013

Existing fitting methods, which employ a pure tone stimulus, such as the Fig6 method or the POGO2 method, yield the same target gains when individual hearing thresholds are identical. Therefore, the loudness perception of an individual is hardly considered. Also, the fitting procedure becomes an empirical one, which is very time-consuming for detailed adjustment. Fitting methods using fractional octave-band tone stimulus often result in excessive gains at low frequencies and too many measurements for loudness level setting are required. In this study, subjects with normal hearing are tested and the loudness perception to a certain level of band-limited white noise at the modified 14 critical bands is classified by five categories. A standard database, as the target value, is constructed by statistically processing the results. The same procedures are applied to a hearing impaired patient and the response data are used for estimating individual hearing characteristics. Acquired hearing loss data are compared with the standard database of normal hearing and then the target gains for five loudness categories are obtained for compensation. The proposed fitting method was compared with the existing methods for some patients and the results suggest that the auditory performance is better than the existing algorithms or empirical readjusting fitting.
Stable multibubble sonoluminescence
Authors: Greenwood Larry R. , Posakony Gerald J. , Bond Leonard J. , Good Morris S. , Ahmed Salahuddin , Wojcik Michael D. , Harper Warren W. , Morra Marino
Published: October 2013

A multibubble standing wave pattern can be generated from an acoustic wave reflected from a flat surface. By adding a second transducer at 90 deg from the transducer generating the standing wave, a three-dimensional volume of stable single bubbles can be established. Further, the addition of the second transducer operating at the same frequency stabilizes the bubble pattern so that individual bubbles may be studied. The size of the bubbles and the separation of the standing waves depend on the frequency of operation. Two transducers, operating at frequency of 630 kHz, provided the most consistent results for the configuration used in this study. The bubbles exhibit bright sonoluminescence. Spectral measurements are in progress. Effect of the shape of the configuration will be discussed along with the standing wave patterns, spectral data, and pictorial results of separation of individual bubble sonoluminescence in a multibubble sonoluminescence environment.
Physical analysis of a stable cavitation bubble structure at high acoustic intensity
Authors: Dubus Bertrand , Moussatov Alexei , Granger Christian , Campos-Pozuelo Cleofe , Vanhille Christian , Mettin Robert , Tervo Topi , Lauterborn Werner
Published: October 2013

A cavitation bubble structure stable at high acoustic intensity (from 1.8 to more than 8.2 W/cm2) has been experimentally observed [A. Moussatov et al., Ultrason. Sonochem. 10, (2003)]. At the vincinity of an axisymmetrical radiating surface, big streamers of bubbles get ejected from the surface and build up a bubble structure of conical shape denoted CBS. In this paper, results on the observation and analysis of the CBS are reported for 20-kHz horn-type transducers with different sonotrode diameters. It is found that: (i) the CBS is always a zone of high chemical activity, even when the bubble structure is not observed due to high speed streaming; (ii) the geometry of the CBS is determined by nonlinear acoustic wave propagation. These results are supported by various experimental data: chemiluminescence measurements, high speed movies (2250 frames/s) under CW scattered light or LED flashes synchronized with driving signal and measurement of the acoustic pressure and of the time-averaged acoustic pressure. [Work supported by CNRS-CSIC cooperation project and European Union (FEDER 2).]
Simulation of synchronized animal calling with a distributed sensor network
Authors: Ojomo Efosa , Mudindi Praveen , Amundson Isaac , Frampton Kenneth D.
Published: October 2013

A distributed sensor network has been programmed to simulate synchronized calling exhibited by many species of frogs and insects. The distributed sensor network consists of numerous sensor nodes consisting of a microprocessor, wireless communications and a sensor board containing a buzzer and microphone. The goal was to program the sensor array to mimic the synchronized calling behavior (inspired in no small part by the recent appearance of cicada brood X). To this end, a single leader node was programmed to begin calling (i.e., buzzing). The remainder of the node array was programmed with an algorithm which allows them to detect other buzzing nodes and to synchronize their own buzz to that of the group. After start-up transients, the entire array calls in synchrony. Of particular interest is the system’s transient behavior system when perturbed or when a second leader node begins calling out of synch with the array. The hardware and software algorithms will be described. Furthermore, numerous nodes will be distributed throughout the audience and a demonstration of system behavior will be provided. While this is a rather whimsical application of distributed array processing, it does demonstrate the unique system behaviors that can arise in truly distributed processing.
Acoustic array data compression via Karhunen-Loeve transform
Authors: Boyle Frank A. , Phipps Thomas H.
Published: October 2013

Acoustic data compression has been explored in several contexts and several techniques exist. The applicability of each technique depends on the type of data processing that is intended. For example, audio data is often compressed via perceptual coding methods (e.g., mp3) in which quantization noise is distributed according to psychoacoustic principles. The Karhunen-Loeve (KL) transform presents an opportunity to compress surveillance array hydrophone-level data while preserving relevant features in beamformed displays. A KL codec was formulated and applied to acoustic test data from a horizontal line array. The results appear promising in that features of interest are preserved with significant data compression. The presentation will include a description of the algorithm as well as examples with actual data. [Work funded by ONR.]
Parabolic propagation in a weakly range-dependent duct: Approaching higher orders systematically
Authors: Gragg Robert F.
Published: October 2013

This work illustrates a technique that exploits energy-conserving transformations to split a CW field into a pair of components that propagate via uncoupled parabolic equations in opposite directions along the axis of a weakly inhomogeneous waveguide. A systematic series of these transformations produces this splitting at successively higher orders while avoiding backscatter. In the interest of clarity, the simplest possible nontrivial case is considered: waves of vertical displacement on a stretched membrane with a smooth density inhomogeneity along the y direction that forms a duct in the x direction. (This case is truly two-dimensional and its only environmental variable, density, is continuous.) This transformation technique provides an efficient means of incorporating the effects of weak environmental inhomogeneity in higher-order parabolic propagation. [Work supported by ONR.]
A new primitive ray-tracing (PRT) model to compute forward and inverse acoustic propagation in a two-dimensional, range-dependent, sound-speed field
Authors: Vinogradov Sergey V. , Caruthers Jerald W. , Ngodock Hans E. , Sidorovskaia Natalia A.
Published: October 2013

A primitive ray-tracing (PRT) model has been developed as part of a computational system to support potential tomographic observations. It is intended to estimate the variability in acoustic arrivals due to mesoscale oceanic circulation. The underlying algorithm is fully range dependent; it utilizes both vertical and downrange sound-speed gradients to compute ray trajectories. The ‘‘primitiveness’’ of the model means that it is simple enough to be inverted, while most existing forward acoustic models are too sophisticated computationally for that purpose. The inversion of this PRT takes in travel times and estimates possible oceanic structure, which further is being assimilated into an ocean circulation model. This paper provides details and results of acoustic computational experiments, along with a description of the PRT’s application in a postulated tomographic observational system for the northeastern Gulf of Mexico.
Coupled volumes in concert hall: Not just reverberation chambers
Authors: Doria Damian , Johnson Russell , Brooks Todd L. , Pyper Ted
Published: October 2013

Artec Consultants Inc. has incorporated coupled volumes into the design of purpose-built concert hall spaces for over three decades. Initial interest in coupled volumes for concert spaces focused on extending reverberation time and assisting loudness balance for brass and strings, but the geometric configuration and incorporation of other acoustics design innovations in Artec projects has varied not only reverberation time but also several other primary parameters. This paper reviews approaches to incorporating coupled volumes in concert halls and comments on the artistic value of their ability to instantly tailor the acoustics of a concert space. Artec’s halls in Dallas, Lucerne, São Paulo, and Philadelphia are discussed in the context of their use of coupled volumes to enhance the performance environment for symphony and other performances.
Searching for double-slope behavior in a coupled-volume concert hall
Authors: Storch Christopher
Published: October 2013

Impulse response measurements were recently conducted in a coupled-volume concert hall in an attempt to discover any double-slope behavior in the reverberant decay, a characteristic that had been subjectively heard in concerts. In the unoccupied hall, measurements were conducted in the primary volume with the secondary volume decoupled, 50% coupled, and 100% coupled. Results of these measurements will be presented. Speculation as to why the reverberant decays do not agree with subjective listening impressions will be discussed.
Acoustic monitoring of northern fur seals in the Bering Sea
Authors: Insley Stephen J. , Robson Bruce W. , Burgess William C.
Published: October 2013

A substantial problem in determining whether anthropogenic noise affects marine animals is measuring how an animal responds to a noise source that is located in a remote pelagic environment and is ephemeral in nature. We are interested in measuring northern fur seal reactions to ship noise in the Bering Sea, Alaska, where the fur seals have started to decline. The timing of their decline coincides with an increased probability of interaction with the pollock fishing fleet. Whether fishing activity affects fur seal behavior, via direct competition for fish and/or indirect competition (e.g., acoustic disturbance or vessel avoidance), is unknown and difficult to study. We began by developing procedural tools to measure encounter rates and animal response. We deployed acoustic dataloggers on lactating females in order to monitor for ship signatures. This was referenced to movement data from satellite position fixes and pressure data from dive records. The combined dataset provides assays that measure an animal’s movement (i.e., direction, speed, and relative effort via stroke rate), its overall activity budget (i.e., traveling, diving, and resting), and the pattern of diving behavior. The assays are now being field tested with a new set of instrument deployments during the 2004 fur seal breeding season.
Antimasking strategies of underwater vocalizations and hearing abilities of polar seals
Authors: Terhune Jack
Published: October 2013

Detection of underwater vocalizations by polar seals is limited by their auditory sensory abilities and external masking noises from abiotic (meteorological and ice noises) and biotic (conspecific calls) sources. Attributes that present the antithesis of masking noise characteristics are thought to enhance detectability of calls. Some proposed anti-masking strategies such as call repetition/rhythm patterns are supported by evidence of lower detection thresholds (1–5 dB), while others are not (e.g., abrupt onset and offset of calls). For frequency swept calls, downsweeps have lower detection thresholds (1–5 dB) than upsweeps. The majority of frequency swept calls (greater than 0.1 oct) of bearded (Erignathus barbatus), Weddell (Leptonychotes weddellii) and harp (Pagophilus groenlandicus) seals are downsweeps (89%, 86% and 63%, respectively). Temporal and frequency separation, call lengthening, and directional clues also reduce masking effects. Diverse call repertoires and calling behaviors of polar seals (e.g., courtesy rule) appear to have evolved characteristics that reduce the effects of abiotic and biotic masking. Characteristics of many anthropogenic underwater noises differ from sounds produced in nature. To estimate masking effects of anthropogenic noise on phocid communication, it is important to determine if the man-made noises are defeating existing antimasking strategies.
Acoustic reflectivity measurments of sirenia (Florida manatees) at high frequencies
Authors: Jaffe Jules S. , Roberts Paul L. , Simonet Fernando , Bowles Ann E.
Published: October 2013

The Florida manatee (Trichechus manatus latirostris) is an endangered sirenian inhabiting shallow coastal waters of Florida (USA). Its population (∼3300) is dwindling, with 25%–30% of mortalities occurring due to collisions with boats (95 losses in 2002). An active sonar system that detects the presence of the animals, and hence alerts the boater, could help reduce the collisions. Experiments were performed on six captive manatees with several calibrated transducers in a 33×10×3 m3 pool to learn how much sound is reflected by these animals. At a frequency of 171 kHz we transmitted a brief sinusoid. An underwater video camera was aimed along the axis of the range direction of the sound transmission, permitting the co-registration of animal and acoustics. The camera and sonar were calibrated together by translating a 38-mm tungsten carbide sphere (TS=−39 dB@ 171 kHz) in a separate test tank facility. Results indicate that the reflectivity of the animals (not strictly target strength) is somewhat low, in the −49 to −40 dB range.
Geoacoustic inversions in shallow water using Doppler-shifted modes from a moving source
Authors: Giddens Eric M. , Buckingham Michael J.
Published: October 2013

Underwater acoustic measurements have been made of aircraft overflights of a shallow-water (15 m deep) environment off the coast of La Jolla, CA. The narrow-band harmonics generated by the engine and propeller penetrates the air–sea interface and excites the normal modes of the system with each mode having a characteristic Doppler shift. From a high-resolution FFT, the modal eigenvalues are determined from the modal frequencies. These eigenvalues are dependent on the acoustic properties of the sediment. For a Pekeris waveguide, the eigenvalues can be found from the transcendental dispersion relationship, providing a direct method for inverting for the density and sound speed in the sediment without the use of a complicated numerical model. The method is relatively straightforward and only requires a single sensor in the water column. The sensitivity of the inversion technique will be discussed in the context of simulated experiments as well as real data collected in the experiments performed north of Scripps pier, La Jolla. [Work supported by ONR and the ARCS Foundation.]
Travel time difference and incoherent intensity tomography of the current and turbulence structures of shallow oceans
Authors: Yamamoto Tokuo J. , Kaneko Arata , Yamaoka Haruhiko
Published: October 2013

Acoustic waves propagating through irrotational current cause a travel time difference between the reciprocal transmission paths. When they propagate through turbulence, they are scattered and a part of the propagating acoustic wave energy becomes incoherent. The two acoustical principles lead to the two corresponding acoustic tomography methods for imaging current and turbulence. The acoustic cross-array tomography (ACT) experiment was conducted at the Kammon Strait on 17–20 March 2003. Eight ACT measurement units were distributed on both sides of the strait. Gold codes having a carrier frequency of 5.5 kHz were transmitted as source signals. The data obtained from the experiment were used in the travel time difference tomography for imaging the current field and in the incoherent acoustic intensity tomography for imaging turbulence in the strait water. The comparisons between the current fields and the turbulence fields reveal that the turbulence intensity is nearly proportional to the current strength. This indicates that the turbulence in the very shallow (roughly 11 m deep) strait water is generated within and may be transported outside the bottom boundary layer. [Work supported by ONR.]
Effect of exposure duration on lung hemorrhage from low-frequency underwater sound
Authors: Dalecki Diane , Child Sally Z. , Raeman Carol H.
Published: October 2013

Previous research from our lab has shown that low-frequency (∼100–1000 Hz) underwater sound exposure can produce lung hemorrhage in laboratory mammals. The threshold for damage is lowest for exposure at the resonance frequency of lung. In adult mice, the threshold for lung damage is ∼2 kPa using a 3-min continuous wave (cw) exposure at the resonance frequency (∼300 Hz). The objective of this study was to determine the effect of exposure duration on lung damage produced by low-frequency sound. Experiments were performed with anesthetized adult mice. The resonance frequency of each mouse lung was determined using an acoustic scattering technique. Mice were exposed cw at the resonance frequency for durations of 1, 5, 10, 30 s, 1 and 3 min. The threshold for lung hemorrhage was relatively independent of duration for exposures greater than or equal to 1 min. For short exposure durations, the threshold increased and the mean extent of lung damage decreased. In some instances, extensive damage to the lung was observed to occur even for the 5-s exposure duration. However, the likelihood of extensive lung hemorrhage increased with increasing exposure duration.
Real-time timbre analysis as a technique for live synthesis control
Authors: Puckette Miller S.
Published: October 2013

The possibility is explored of controlling synthesis using an instrumental or other sound source, not by trying to recreate the time-varying timbre of the musician’s sound exactly, but instead by making the output sound reflect changes in the input, in a way a musician can control in order to produce an interesting stream of synthetic sound. First the range of spectra available from the sound source, and also that available from the synthesis technique, are estimated. A very simple measure of timbre is used that maps any sound into a point in a ten-dimensional space. (As a byproduct, the ten-dimensional volume spanned by a sound source gives a rough measure of timbral variability.) Then synthesis parameters are chosen for the synthesis algorithm by searching a database of known output timbres.
The impact of the Lennard-Jones parameter choice on theoretical acoustic absorption and dispersion curves
Authors: Petculescu Andi G. , Lueptow Richard M.
Published: October 2013

The acoustic vibrational relaxation in polyatomic gas mixtures is modeled based on binary collisions treated via pairwise transition probabilities. The sensitivity of the model to the values of the Lennard-Jones parameters (potential well depth and collision diameter) is investigated for nitrogen–water–methane mixtures. The choice of the collision diameter has a far greater effect on the transition probabilities and subsequently on the acoustic absorption than that of the Lennard-Jones potential depth. In addition, the sensitivity of the acoustic relaxation model to the choice of an LJ parameter (the collision diameter for water, for the mixture considered) is itself sensitive to the mixture composition. Thus, a binary mixture of moist nitrogen with 338 ppm water is considerably more sensitive to changes of the water collision diameter than is a mixture of nitrogen, 338 ppm water and 1% methane. [Work supported by NASA.]