bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of transducer and tissue parameters on motion induced by radiation force during ultrasonic lesion monitoring
Authors: Mikaelian Samuel , Lizzi Frederic L.
Published: October 2013

Tissue motion induced by acoustic radiation force is studied as a means of monitoring the formation of therapeutic lesions with increased stiffness produced by high-intensity focused ultrasound (HIFU). Our analyses and simulations examine the role and interplay of various tissue and system parameters to assist in designing practical systems and interpreting results. The radiation force is generated by a therapeutic transducer excited at levels below lesion-production threshold, while the magnitude and time-course of the induced motion is monitored via a confocal and collinear diagnostic transducer. Lesions are detected by comparing pre- and post-treatment motion patterns. Parameters characterizing properties of the motion-inducing beam, such as its intensity and spatial profile, and tissue parameters signifying its viscoelastic properties, acoustic attenuation, and geometry, are the focus of this investigation. Acoustic attenuation, which can increase significantly during lesion production and directly affects the radiation-force profile, manifests itself on time scales characteristic of acoustic propagation. In contrast, time scales characteristic of viscoelastic effects are substantially larger. These viscoelastic properties also mediate effects associated with tissue geometry and large-scale spatial beam profile. Effects of diagnostic beam parameters on the sensitivity and accuracy of the method have also been investigated.
Feasibility of bone assessment with leaky Lamb wave in bovine cortical bone
Authors: Lee Kang Il , Yoon S. W.
Published: October 2013

Quantitative ultrasound (QUS) technique is now widely used for non-invasive assessment of osteoporosis. The use of leaky Lamb wave is very attractive since it propagates throughout the cortical thickness of long bones, which means that the entire thickness of bones is interrogated. Feasibility of bone assessment with leaky Lamb wave is investigated in a bone phantom and bovine tibia in vitro using the axial transmission method commonly used to characterize human long bones. The bone phantom consists of Lucite plates with thicknesses of 1, 3, and 5 mm. The results obtained from the bone phantom show that the peak frequencies and amplitudes of excited Lamb modes are strongly dependent on the frequency-thickness product. In the case of the bovine tibia, the S0 Lamb mode may be more sensitive to any change of elastic properties inside the bone plate due to damage or to cortical thickness changes with aging and osteoporosis. This study suggests that leaky Lamb wave is feasible to ultrasonic bone assessment. [Work supported by BK21 Program in Korea.]
The evolution of acoustically absorbent lining systems for anechoic chambers
Authors: Schmitt Jeff
Published: October 2013

Materials for the construction of and techniques for the evaluation of acoustically absorbent lining systems for anechoic test chambers have evolved significantly over the past 20 years. This paper will recount the authors experiences in anechoic chamber design, construction and evaluation techniques since his early 1980s thesis work on the subject conducted under the guidance of Dr. Elmer Hixson of the University of Texas.
Energy density and intensity measurements in a reverberant sound field
Authors: Poterek Thomas J.
Published: October 2013

The measurement of reverberant fields using an acoustic energy density sensor has been investigated over the years but has not seen general use. The energy density sensor can also measure acoustic intensity, which is a more commonly used technique in noise control. Measuring three-dimensional acoustic intensity with the energy density sensor shows that the techniques of energy density are complementary to intensity measurement and worthy of broader use Statistical measurements of kinetic and potential energy density were taken using a rotating boom in a reverberation room. Vector intensity was simultaneously measured in three orthogonal directions along with the total intensity. The measurements show that while the vector intensity components were significant, their sum was zero within the limits of the measurement system.
Physical modeling of the piano
Authors: Giordano N. , Jiang M.
Published: October 2013

Over the past several years, this project has been aimed at constructing a physical model of the piano. The goal is to use Newton’s laws to describe the motion of the hammers, strings, soundboard, and surrounding air, and thereby calculate the sound produced by the instrument entirely from first principles. The structure of the model is described, along with experiments that have provided essential tests and guidance to the calculations. The state of the model and, especially, how this work can lead to new insights and understanding into the piano are discussed. In many cases the work and the specific questions addressed along the way have followed paths initially inspired and developed by Gabriel Weinreich. [Work supported by NSF.]
Smart panels with SISO or MIMO velocity feedback control systems
Authors: Gardonio Paolo , Elliott Stephen
Published: October 2013

This paper summarizes and contrasts the research work that has been carried out on two types of smart panels with ASAC control systems: first, a SISO velocity feedback control system with a sensor that detects the volumetric component of the vibration of the panel and an actuator that exerts a uniform force over the surface of the panel and, second, a MIMO decentralized feedback control system using a grid of sensors that measure the point velocities of the panel and a grid of actuators that generates point excitations in the locations of the sensors. Both theoretical predictions and experimental results are presented for a reference problem of control of sound radiation by a rectangular panel clamped along the perimeter. The simulations carried out for the two systems have shown that the smart panel with the volume velocity sensor and uniform force actuator can in principle give better control performance than the smart panel with the sixteen decentralized control units. However, the practical implementation of the smart panel with the volume velocity sensor and uniform force actuator is limited by stability problems which are instead a minor issue for the panel with 16 decentralized velocity feedback control units.
Particle sedimentation measurements using active resonator shifts
Authors: Kwiatkowski Christopher S.
Published: October 2013

A measurement of the properties of fluids with suspended particles is important in fields such as biology, chemistry, geology, and industrial processing. The limitation of being inside closed or otherwise inaccessible containers provides a challenge to typical measurement systems, especially where an invasive technique is either disadvantageous or impossible. These situations occur in opaque containers or within pre-existing pipes. The technique presented describes using an active all-ultrasonic technique, where the time-averaged radiation force on particles in an acoustic standing wave causes them to migrate. The migration of particles has a measurable effect on the resonant frequency of the cavity that depends on the properties of the particles and the host fluid. This technique is used to initially determine the presence of suspended particles in a fluid, to characterize the particles, and provide a measurement of the total volume fraction of suspended particles. The measurement of the total volume fraction as a function of time gives information on the particle sedimentation rate. The technique is noninvasive, uses no moving parts, consumes little electrical power, and is capable of relatively fast measurement times on the order of a few seconds.
Modeling HRTF of a thin elastic layered spherical model of head
Authors: Dat Tran H. , Fumitada Itakura , Oboznenko Igor L.
Published: October 2013

The understanding and simplified modeling of the Head Related Transfer Function (HRTF) is very important for applications in virtual audio reality. However HRTF depends on many factors such as the shape of head and pinnae, torso, refraction by the body, and others. In this work we investigated the influences of a thin-elastic layered structure of a head on the HRTF. The analytical solution is applied to a six-layer model of the head. The elastic properties of layers are taken into account in the modeling. The results are compared with the results of spherical rigid model and experiments. The numerical results showed the new peaks of HRTF caused by elastic scattering and re-reflecting from layers. However this effect is very small and can be neglected at high frequency.
Effects of hair, clothing, and headgear on localization of three-dimensional sounds Part IIb
Authors: Riederer Klaus A. J.
Published: October 2013

Seven 20–25-year-old normal hearing (≤20 dBHL) native male-undergraduates listened twice to treatments of 85 virtual source locations in a large dark anechoic chamber. The 3-D-stimuli were anew-calculated white noise bursts, amplitude modulated (40-Hz sine), repeated after a pause (total duration 3×275=825 ms), HRTF-convolved and headphone-equalized (Sennheiser HD580). The HRTFs were measured from a Cortex dummy head wearing different garments: 1=alpaca pullover only; 2=1+curly pony-tailed thick-hair+eye-glasses; 3=1+long thin-hair (ear-covering); 4=1+mens trilby; 5=2+bicycle helmet+jacket [Riederer, J. Acoust. Soc. Am., this issue]. Perceived directions were signified by placing a tailored digitizer-stylus over an illuminated ball darkened after the response. Subjects did the experiments during three days, each consisting of a 2-h session of several randomized sets with multiple breaks. Azimuth and elevation errors were investigated separately in factorial within-subjects ANOVA showing strong dependence p(≤0.004) on all main effects and interactions (garment, elevation, azimuth). The grand mean errors were approximately 16°–19°. Confused angles were retained around the ±90°-interaural axis and cos(elev)-weighting was applied to azimuth errors. The total front−back/back−front confusion rate was 18.38% and up−down/down−up 12.21%. The confusions (except left−right/right−left, 2.07%) and reaction times depended strongly on azimuth (main effect) and garment (interaction). [Work supported by Graduate School of Electronics, Telecommunication and Automation.]
Negative temporal summation of the responses to pairs of tone bursts in albino mice inferior colliculus
Authors: Bibikov Nikolay G. , Cai Chen Qi , Jie Tang
Published: October 2013

The extracellular activities of single units in an inferior colliculus of narcotized albino mice have been studied. As a stimuli pairs of best frequency (BF) tone bursts with different duration have been used and forward masking has been studied. The test tone usually has a 40 ms duration at intensity 5 dB above threshold. The intensity and duration of the masker could be changed. It was shown that the forward masking essentially depends upon the duration of the first burst. In many cases, the negative temporal summation can be seen. The increase in the duration of first burst (or masker) leads to the decrease in the whole response. Moreover, the BF tone burst which did not evoke any spike response could inhibit the response to the second (test) tone in some cases. Therefore in many units the inhibitory threshold was lower than the excitatory threshold even at the best frequency. The local application of bicuculline through a multibarrel-electrode increased the pulse activity considerably. However, the effect of forward masking usually left even after an inhibitory antagonist (bicuculline) application. [Work supported by grants 39970251 from NSFC, T010360056 from the Foreign Expert Bureau of the State Council of China, and 02-04-3900 from RFBR-NSFC.]
On using ordinary mobilities to predict structure borne power flow from studs to directly attached gypsum board of a wood stud wall—Effect of simplifying assumptions
Authors: Nightingale Trevor , Kohler Katrin
Published: October 2013

This paper reports on the effect of simplifying assumptions made when applying ordinary point mobilities (from thin plate/beam theory) to predict structure borne power, and hence velocity level difference (VLD), from a stud to gypsum board attached by screws. The systematic study showed for practical purposes the fastening points of a gypsum board sheet were sufficiently far from an edge so that the measured mobilities approached those of a drive point located near the sheet center. The mobility of a stud does not change appreciably when attached to the wall head and sole plates. Above the transition frequency from line to point connection where fastener spacing is greater than one half wavelength VLD is inversely proportional to the number of fasteners. Measurements indicate above 1000 Hz local and volumetric deformation of the stud are important causing a very significant VLD across the stud. Deep beam theory, which includes area of the contact between the stud and gypsum board must be included. Between 125–1000 Hz, where the basic assumptions are reasonably satisfied, there is very good agreement between measured VLD and predicted using thin plate/beam mobilities. Predictions indicate agreement above 1000 Hz is greatly improved using deep beam theory.
Control of sound transmission into a large composite cylinder using passive, adaptive–passive and active control strategies
Authors: Johnson Marty , Esteve Simon , Fuller Chris
Published: October 2013

This work is directed at the goal of controlling the high noise levels experienced in launch vehicle payload fairings. The problem frequency range is typically below 300 Hz where passive structural damping and sound absorption treatments perform inadequately. In this paper the work conducted at Virginia Tech over the last 3 years on techniques for reducing the interior noise levels at launch using an eight ft. diameter composite cylinder as a test platform is summarized. First the theoretical development will be presented with an overview of the mechanisms of sound transmission. Then, passive control methods using optimally damped structural distributed vibration absorbers (DVAs) and acoustic Helmholtz resonators will be presented. Both theoretical results and experimental results using high level acoustic excitation (132 dB) will be described. A set of adaptive Helmholtz resonators were also built and tested and are capable of tracking changes in acoustic resonances automatically. Finally, the results from a fully active structural acoustic control experiment using distributed active vibration absorbers will be presented.
Acoustics of the glottal source at closures for fricative and stop consonants
Authors: Salomon Ariel
Published: October 2013

Previous research on acoustic distinctions between manner classes of obstruent consonants has primarily considered differences at the release. This study investigates acoustic distinctions in the glottal waveforms at the closure. It is hypothesized that the higher pressure generated in a complete closure (stops and affricates) results in a more rapid cessation of vibration of the glottis than for a partial closure (fricatives). This can be measured by rate of energy offset at the closure landmark. This work studies measurements of the rate of change of energy at closure in various frequency bands. For lower frequencies, in the range of the first formant or below, it is expected that there is interaction between voicing and manner due to the presence of a ‘‘voicebar’’ (continued vibration) during the closure. Preliminary measurements show that both voiced and voiceless stop consonants exhibit more rapid rates of energy offset than fricatives in a frequency band containing the second formant. This measure may be useful in noisy environments where the energy of frication is obscured; the periodic glottal waveform can be more reliably measured in noise, e.g., by autocorrelation-based methods. [Work supported by NIH Grant No. DC02978.]
Effects of obstruent consonants on the F0 contour
Authors: Hanson Helen M.
Published: October 2013

When a vowel follows an obstruent consonant, the fundamental frequency in the first few tens of milliseconds of the vowel is influenced by the voicing characteristics of the consonant. The goal of the research reported here is to model this influence, with the intention of improving generation of F0 contours in rule-based speech synthesis. Data have been recorded from 10 subjects. Stops, fricatives, and the nasal /m/ were paired with the vowels /i,ɑ/ to form CVm syllables. The syllables mVm served as baselines with which to compare the obstruents. The target syllables were embedded in carrier sentences. Intonation was varied so that each target syllable was produced with either a high, low, or no pitch accent. Results vary among subjects, but in general, obstruent effects on F0 primarily occur when the syllable carries a high pitch. In that case, F0 is increased relative to the baseline following voiceless obstruents, but F0 closely follows the baseline following voiced obstruents. After voiceless obstruents, F0 may be increased for up to 80 ms following voicing onset. When a syllable carries a low or no pitch accent, F0 is increased slightly following all obstruents. [Work supported by NIH Grant No. DC04331.]
Speech synthesis with pitch modification using harmonic plus noise model
Authors: Lehana Parveen K. , Pandey Prem C.
Published: October 2013

In harmonic plus noise model (HNM) based speech synthesis, the input signal is modeled as two parts: the harmonic part using amplitudes and phases of the harmonics of the fundamental and the noise part using an all-pole filter excited by random white Gaussian noise. This method requires relatively less number of parameters and computations, provides good quality output, and permits pitch and time scaling without explicit estimation of vocal tract parameters. Pitch scaling to synthesize the speech with interpolated original amplitudes and phases at the multiples of the scaled pitch frequency results in an unnatural quality. Our investigation for obtaining natural quality output showed that the frequency scale of the amplitudes and phases of the harmonics of the original signal needed to be modified by a speaker dependent warping function. The function was obtained by studying the relationship between pitch frequency and formant frequencies for the three cardinal vowels naturally occurring with different pitches in a passage with intonation. Listening tests showed that good quality speech was obtained by linear frequency scaling of the amplitude and phase spectra, by the same factor as the pitch-scaling.
The effect of masking noise on acoustic-phonetic contrasts in post-lingually deafened cochlear implant users
Authors: Vick Jennell C. , Perkell Joseph S. , Stockmann Ellen , Zandipour Majid , Lane Harlan , Tiede Mark
Published: October 2013

This study examined the effect on the vowel contrast distance (average inter-vowel distance in the F1−F2 plane) of gradually decreasing the signal-to-noise ratio (SNR) in the auditory feedback of a post-lingually deafened cochlear implant (CI) user at 1-month and 1-year following CI processor activation. Masking noise, mixed with normal levels of speech feedback, was presented through the headpiece of a research sound processor to the CI user. As a control, an analogous procedure was used for a normal-hearing speaker where the masking noise and speech feedback were delivered over headphones. The SNR was gradually decreased over seven steps as the speakers produced ten repetitions of two vowel contrasts (æ\/[g\/] and i\/u). Speech SPL and vowel contrast distance were measured at all seven masking noise levels. Data from both subjects showed that SPL gradually increased with decreased SNR, while contrast distance decreased. The effect was greater after 1 year of experience with a CI than at 1 month. The effect in the NH speaker was similar to that noted in the CI user after 1 year of experience. Data from additional subjects will be analyzed and reported. [Work supported by NIH Grant No. R01 DC03007.]
Analytic conditions for asymptotic optimality of the maximum-likelihood estimator with application to problems in remote sensing
Authors: Makris Nicholas C.
Published: October 2013

Analytic conditions necessary for a general multivariate maximum-likelihood estimate (MLE) to become asymptotically optimal are derived from the first principles of estimation theory following Makris and Naftali [J. Acoust. Soc. Am. 110, 1917–1930 (2001)]. The conditions are given as sample size or signal-to-noise ratio requirements for the MLE to become asymptotically unbiased and attain the minimum variance possible for any unbiased estimate known as the Cramer–Rao lower bound (CRLB). Applications to problems common in remote sensing such as time-delay and Doppler shift estimation, beamforming, source localization in a waveguide, pattern recognition in 2-D intensity images, surface orientation estimation, and Kalman filtering will be presented.
Image processing techniques for underwater acoustic image enhancement
Authors: Boyle Frank
Published: October 2013

Underwater acoustic images are often dominated by noise, which obscures signals of interest. When the spatial character of the noise differs from that of the signal, image processing techniques can be employed to enhance the image. In underwater acoustic time-bearing displays, the signals of interest form continuous tracks, while noise often takes on the form of isolated speckle. In this case, a speckle suppression technique related to the Hough transform can be used to reduce the noise and enhance the tracks. The presentation will include a discussion of variations of the technique that are under consideration, as well as considerations of optimum values for the input parameters.
Multiple time-reversed guide-sources in shallow water
Authors: Gaumond Charles F. , Fromm David M. , Lingevitch Joseph F. , Gauss Roger C. , Menis Richard
Published: October 2013

Detection in a monostatic, broadband, active sonar system in shallow water is degraded by propagation-induced spreading. The detection improvement from multiple spatially separated guide sources (GSs) is presented as a method to mitigate this degradation. The improvement of detection by using information in a set of one-way transmissions from a variety of positions is shown using sea data. The experimental area is south of the Hudson Canyon off the coast of New Jersey. The data were taken using five elements of a time-reversing VLA. The five elements were contiguous and at midwater depth. The target and guide source was an echo repeater positioned at various ranges and at middepth. The transmitted signals were 3.0- to 3.5-kHz LFMs. The data are analyzed to show the amount of information present in the collection, a baseline probability of detection (PD) not using the collection of GS signals, the improvement in PD from the use of various sets of GS signals. The dependence of the improvement as a function of range is also shown. [The authors acknowledge support from Dr. Jeffrey Simmen, ONR321OS, and the chief scientist Dr. Charles Holland. Work supported by ONR.]
Wavelets and neural networks for change detection in simulated sidescan sonar data
Authors: Ioup Juliette W. , Gendron Marlin L. , McDowell Pamela J. , Bourgeois Brian S. , Ioup George E.
Published: October 2013

Recently recorded sidescan sonar data can be compared to historical data from the same area to detect any differences or changes. Such comparisons are complicated by the fact that the position is uncertain and the viewing angle or depth of the sidescan sonar may be different in the two data sets. Neural networks offer a possible technique to be used in the comparison procedure. Inputs to neural networks investigated here include wavelet transform coefficients of the data as well as the two-dimensional sidescan sonar data itself. Several different neural network architectures and several different wavelet bases are investigated. Both noise-free and noisy data are considered. Preliminary results for change detection using simulations that model simple historical and recent sidescan sonar data sets will be presented. [Research supported in part by NRL-ASEE Summer Faculty Research Program.]
Matched field processing in a multisource environment
Authors: Rittermann Eric A. , Koch Robert A. , Stotts Steven A. , Knobles D. P.
Published: October 2013

Matched field processing can be utilized to localize a single source in a quiet, well-known medium. In shallow water, the combination of environmental mismatch and low signal to noise ratio causes significantly reduced resolution. Discussed is a simultaneous matched field processing and geoacoustic inversion methodology using a simulated annealing approach applied to a quiet source in the presence of loud interferers. This is accomplished by preprocessing array element acoustic data with a spatial matrix filter, which acts to reduce the effective number of sources present in the received data. Specifically, the effects of the filter on matched field processing and geoacoustic inversion accuracy as a function of interferer strength is investigated. Acoustic data collected from the Gulf of Mexico is employed to validate the proposed simultaneous localization and inversion approach. [Work supported by ONR.]
Spatial encoding of communication sequences with an ocean acoustic time-reversal mirror
Authors: Roux Philippe , Kuperman W. A. , Hodgkiss W. H. , Song Hee Chun , Akal Tuncay , Stevenson Mark
Published: October 2013

With the at-sea demonstration of producing simultaneous multiple focal spots with a TRM, spatial encoding of communication sequences is now possible. We present the results of an ocean acoustic experiment in which we demonstrate that different communication sequences can be simultaneously sent to and decoded at individual receivers on a vertical array. This ‘‘multiple input, multiple output (MIMO)’’ process significantly increases the acoustic communications band rate. Various incoherent and coherent communication temporal coding schemes are employed together with this spatial procedure.
High-frequency underwater acoustic communications using FH-FSK signaling in a reverberant shallow water environment
Authors: Yang Wen-Bin , Yang T. C.
Published: October 2013

This paper describes the experimental results of frequency-hopped frequency-shift-key (FH-FSK) signaling operated at 20 kHz with a 4 kHz bandwidth for underwater acoustic communications in a reverberant shallow water environment. The data were collected during the RDS4 (Rapidly Deployable Systems) experiment in a shallow water (<80 m depth) near Halifax, Canada. The measured impulse response function showed multipaths lasting over a second, which is an order of magnitude longer than the symbol length. Time-varying Doppler shifts of 30–70 Hz were found in the data. The long multipath delay and high Doppler shift are found to have a significant impact on data processing. For example, using conventional processing that detects the symbol energy over the symbol duration, the bit error rates (BER) are of the order 30–40%. Using a longer time window allowing integration of multipath energy and using Doppler estimated from trigger signals, the uncoded BER is reduced to 10–15%. The data are error-free after error decoding using a convolutional code with a rate and constraint length of 9. Consequences for acoustic networking will be discussed. [Work supported by ONR.]
Computer modeling of a large fan-shaped auditorium
Authors: Smith Heather , Leishman Timothy
Published: October 2013

A research project was recently undertaken to analyze the acoustical characteristics of a 21000-seat fan-shaped auditorium. Careful geometric modeling of the hall has been a significant part of this study. Because of its size, shape, and other architectural features, computer modeling has presented some interesting challenges. For example, it has been shown experimentally that the concavely oriented rows of (moderately absorptive) seats produce significant scattering that aggregates toward the focal point of the hall. This paper will discuss how the seat scattering and scattering from other bodies have been included in the model. Other challenges in modeling a hall this size will also be discussed.
Shoehorning in the jet age
Authors: Beranek Leo L.
Published: October 2013

The introduction into commercial service of jet air transports preceded the codification of U.S. federal aviation noise regulatory policy by nearly two decades. The immediate problem that had to be solved to permit jet operations in 1958 at New York airports was to determine that the noisiness of jet airplane would be no greater than that of the largest propeller-driven aircraft then in operation. This paper describes the efforts made for the Port of New York Authority to meet and enforce that mandate. BBN made noise measurements of many propeller aircraft takeoffs in the community off the main runway at Idlewild at distances of 2.5 miles and greater from the start of take-off roll. Each measurement was associated with airplane type, gross weight, and altitude. The Boeing 707 was similarly measured at Boeing’s airport. Relative annoyance judgments were made in the laboratory to establish equivalent noisiness of jet and propeller spectra, and ‘‘Perceived Noise Levels’’ were determined by a process similar to loudness calculations. Boeing was forced to equip the 707 with multi-tube mufflers and, and jet take-off procedures had to be modified to maintain equivalent perceived noise levels. The substantive findings and politics of these efforts are discussed.
Soap bubbles, sparks, sonic booms, spikes, and David Blackstock
Authors: Pierce Allan D.
Published: October 2013

In the late 1960s people were puzzled by some anomalous features in the measured waveforms of sonic booms recorded at the ground during flyovers of supersonic aircraft. The waveforms were supposed to look like the letter N, but that was not always the case. Sometimes there were strange upward reaching spikes just behind the leading and trailing shocks. There were a lot of explanations kicking around, and the present author had the idea that it was somehow caused by imperfect focusing of wavefonts after traveling through regions of higher sound velocity and discussed this with David Blackstock, who made the characteristic remark, ‘‘Let’s talk experiment.’’ What resulted was an experiment that would have been worthy of Lord Rayleigh. The paper that reported this, titled ‘‘Measurements of the Refraction and Diffraction of a Short N-Wave by a Gas-Filled Soap Bubble,’’ appeared in J. Acoust. Soc. Am. in March 1971. Besides really nailing down the physical phenomena responsible for the spikes on sonic boom waveforms, it illustrated a wealth of physical concepts and experimental techniques. The present talk discusses the background of the paper, the physics that it used, and the influence it had on subsequent research.
Statistical nonlinear acoustics: First studies and current state
Authors: Rudenko Oleg V.
Published: October 2013

Statistical physics of high-intensity noise waves has, in principle, a long-term history. Nonlinear interactions between random and regular waves studied in the 1930s were devoted to sound absorption in solids caused by energy transfer from coherent phonons (signal) to Debye’s thermal quantum (noise). However, exhaustive studies of nonequilibrium nonlinear random wave processes have been carried out only in the 1970s, after experimental and theoretical nonlinear acoustics reached an advanced stage of development. David Blackstock, one of the founders of modern nonlinear acoustics, performed pioneering experiments on broadband noise spectra distortion and signal–noise interactions in tubes and outdoors. These experiments confirmed existing data and formed the fundamental basis for both future studies and applications. Along with temporal statistics, spatial ones were considered by D. T. Blackstock during his studies of nonlinear diffraction caused by orifices and screens with irregular edges. These results are also of great significance for applications. A brief overview of the first studies in statistical nonlinear acoustics is given, as well as of new results obtained in recent years.
Aeroacoustics, moving boundaries, and bursting balloons: Acoustic sources revisited
Authors: Morfey Christopher L.
Published: October 2013

The use of equivalent acoustic sources to describe scattering in a nonuniform medium dates back to Rayleigh’s theory of sound. The idea of equivalent sources in a uniform medium at rest was later developed by Lighthill into his ‘‘acoustic analogy,’’ capable of describing the generation of sound by turbulence and other vortical flows. In the present paper Lighthill’s acoustic analogy formulation is generalized to encompass initial-value problems; the initial conditions are represented by impulsive sources and dipoles distributed over the domain, and boundary conditions are represented in the usual manner by surface sources and dipoles. David Blackstock’s bursting balloon example, discussed in Chapter 3 of Fundamentals of Physical Acoustics, can be solved by this method. However, in situations where the medium is of nonuniform density (for example, a gas with a specified temperature distribution at the initial time), the impulsive source distribution obtained by a direct application of time windowing to the acoustic analogy is nonphysical. The apparent paradox is resolved by introducing the energy conservation equation, and reformulating the acoustic analogy with pressure, rather than density, as the wave variable.
From bench to bedside: Nonlinear bio-ultrasound
Authors: Parker Kevin J.
Published: October 2013

In the early 1960s, David Blackstock developed the weak shock theory which characterized the development and evolution of harmonics in a finite-amplitude propagating plane wave. Later work developed an understanding of beam patterns of the fundamental and higher harmonics from piston radiators. All of these concepts were germane to the field of bio-ultrasound. However, nonlinear effects were largely unexploited in bio-ultrasound until the 1980s, when the role of finite-amplitude mechanisms was recognized as an enhancer of heating and lesion production in high intensity applications. Later, in the 1990s, the role and the advantage of higher harmonics in ultrasonic imaging were developed. In particular, the higher harmonics generated by nonlinear effects, especially in the presence of aberrating tissue, were shown to produce dramatic increases in the resolution and contrast of ultrasound images in cardiology and other applications. Today, every high-end medical ultrasound scanner has the capability of ‘‘harmonic imaging’’ for improved image quality in a number of applications. The physics and technology of this remarkable development will be reviewed, along with the important guiding role of David Blackstock and his collaborators, particularly at UT Austin and at U. Rochester.
Predicting folded beam waveguide absorber behavior using full translational and rotational degree of freedom coupling
Authors: Pray Carl , Campbell Robert , Hambric Stephen , Munro Andrew
Published: October 2013

Folded beam waveguide absorbers (WGAs) have been shown to be effective low-frequency damping devices. Early WGA studies were unable to accurately predict this damping behavior. These studies used only translational degrees of freedom (DOFs), which resulted in the underestimation of the WGA damping performance. A recent study [Munro and Hambric, ‘‘Modeling folded beam waveguide absorber behavior using translational and rotational degree of freedom frequency response function coupling,’’ Proc. NOISE-CON 2003] used translational and rotational DOF frequency response functions to predict folded beam WGA behavior when attached to a thick rectangular plate, where the plate and WGA rotational DOFs were estimated using the finite-differencing method. Each plate and WGA DOF was coupled independently using frequency domain substructure synthesis (FDSS) [Jetmundsen et al., ‘‘Generalized frequency domain synthesis,’’ J. Am. Helicopter Soc. 55–64, Jan (1988)], and the damping contributions due to each DOF were summed to give the total WGA damping prediction. This method gives a much improved damping estimate from previous methods but is inefficient for complex problems. In this study, all the DOFs for the plate and WGA are combined simultaneously using FDSS to predict the WGA damping behavior and plate response with folded beam WGAs attached.
Enhancement of distinctiveness in strident fricatives: An example from Mandarin Chinese
Authors: Lee Chao-Yang , Stevens Kenneth N.
Published: October 2013

Strident fricatives in Mandarin may be followed by fricative vowels, which are made with the tongue body in essentially the same position as in the corresponding fricative (Ladefoged and Maddieson, 1996). Specifically, the vowel [i] may occur only after the palatalized fricative, the apical vowel after the alveolar fricative, and the retroflex vowel after the palatoalveolar fricative. Given the complementary distribution, the three phonetically distinct vowels are generally considered allophones. Under the view that the implementation of discretely specified distinctive features may be enhanced by gradient, non-contrastive articulatory gestures to maintain perceptual distinctiveness (Keyser and Stevens, 2003), it is proposed that the three vowels are derived from an underlying [i] and are modified to enhance the defining articulatory and acoustic attributes of the fricatives. Acoustic data from six speakers indicate that the defining acoustic attributes for the fricatives, i.e., spectral prominences in discrete frequency ranges, are associated with distinct tongue configurations. The articulatory and acoustic properties of the palatalized fricative is most compatible with those of [i], whereas the tongue body backing gesture in the alveolar and palatoalveolar fricatives are consistent with lowered F2 frequency in the apical and retroflex vowels. [Work supported by NIH.]
Nonlinear acoustics in tissue harmonic imaging
Authors: Averkiou Michalakis
Published: October 2013

In recent years the interest in nonlinear acoustics has dramatically increased in diagnostic ultrasound. There are two main areas where nonlinear acoustics is used in medical imaging: tissue harmonic imaging (THI) and imaging of ultrasound contrast agents. Although similar approaches are used in both of these areas, they are very different in that THI is based on nonlinear propagation of sound in tissue, whereas contrast imaging is based on the nonlinear scattering from resonant microbubbles. The clinical benefits of THI are reduced phase aberration artifacts and overall clutter, improved border delineation, and increased contrast resolution. The basic principles of nonlinear propagation of sound beams in tissue are discussed here. Theoretical and experimental results are used to demonstrate some of the properties of nonlinear propagation and their relation to imaging. To a large extent the clinical benefits of THI are explained with the nonlinear propagation properties. Imaging considerations and techniques like pulse inversion and power modulation are discussed. These techniques are also used in imaging contrast agents (microbubbles) and an effort is made to separate the various issues in these two imaging areas and explain their differences.
Noise impact caused by electrical energy substations in Curitiba, Brazil
Authors: Diniz Fabiano B. , Zannin Paulo T.
Published: October 2013

This survey is intended to characterize the noise impact due to electrical energy substations in the city of Curitiba over the population living in their vicinity. This impact has been studied with the aid of a computational tool capable of mapping the acoustical field of substations and their vicinity. Several factors have been considered in this survey: sound power of the transformers; vehicle flow on the surrounding roads; positioning of the firewalls, of the buildings and of the walls; terrain topography. Four substations have been analyzed, and an acoustical map has been traced for each of them. With these maps it was possible to visualize what was the incident noise level on the building facades. The predicted noise levels have been compared to the environmental legislation of the noise emissions in effect in the city.
Evaluation of noise pollution in urban parks of Curitiba, Brazil
Authors: Ferreira Andressa M. , Diniz Fabiano B. , Zannin Paulo T.
Published: October 2013

A study about the noise pollution found in six urban parks of Curitiba, Paran, Brazil. The equivalent noise levels (Leq) have been measured in points spread throughout the park, and interviews have been conducted with some park visitors. It has been found out that 17.83% out of the measurement sites have presented Leq levels over 65 dB(A), considered by the Preventive Medicine as the maximum level one can be exposed to without being exposed to health impairment risks, and 52.48% out of the meas sites do not satisfy the municipal law 10625, which states the noise emission level of 55 dB(A) as the limit value for green areas (AV). The results of the questionnaires applied to the local visitors have showed that 39% out of the interviewed people users to visit the park every 75% of them seek for the realization of a physical activity during the realization of their activities in the parks, 22% out of interviewed people point the noise pollution as the source of annoyance and 29% of them point the local security.
Wave propagation in viscoelastics with chemical relaxation
Authors: Margulies Timothy
Published: October 2013

Acoustic wave properties of fluids have provided a fruitful qualitative and quantitative analysis of fast chemical reactions. The purpose of this paper is to present an extension of the linear acoustic theory of Verdier and Piau [J. Acoust. Soc. Am. 101, 4 (1997)] to include simultaneous chemical kinetic relaxation. The energy equation, equation of state with thermodynamic relations are formulated to account for chemical reactions. A general wave equation for a compressible viscoelastic with thermal transfer and chemical progress variable perturbations are explicitly modeled. Longitudinal wave propagation is described by a biquadratic equation for the sound absorption and dispersion. Approximations of small thermal transfer and viscous effects yield linearly additive contributions of viscous, thermal, and reaction contributions. Here, linearly viscous or visco-elastic effects can be examined, in addition to the chemical kinetic effects. Sample calculations illustrating the physio-chemical dynamics will be presented.
Explicit pattern recognition models for speech perception
Authors: Nearey Terrance M.
Published: October 2013

Optimal statistical classification of arbitrary input signals can be obtained, in principle, via a Bayesian classifier, given (perfect) knowledge of the distributions of signal properties for the set of target categories. At least for certain constrained problems, such as the perception of isolated vowels, simple (imperfect) statistical pattern recognition techniques can accurately predict human listeners’ performance. This paper sketches several relatively successful case studies of the application of static pattern recognition techniques to speech perception. (Static techniques require inputs of a fixed length, e.g., F1 and F2 for isolated vowels.) Real speech clearly requires dynamic pattern recognition, allowing inputs of arbitrary length. Certain such methods, such as dynamic programming and hidden Markov models, have been widely exploited in automatic speech recognition. The present paper will describe initial attempts to apply variants of such methods to the data from a perception experiment [T. Nearey and R. Smits, J. Acoust. Soc. Am. 111 (2002)] involving the perception of three (VCV) or four (VCCV) segment strings. Practical and conceptual problems in the application of such techniques to human perception will be discussed. [Work supported by SSHRC.]
Speech enhancement for better hearing aid design using chirped wavelets
Authors: Doser Adele
Published: October 2013

Wavelet techniques are utilized in the enhancement of speech signals for hearing-impaired persons. The interest is in schemes that isolate and enhance short duration, broadband speech elements (such as unvoiced, fricative consonants) while still capturing narrow-band speech components (such as vowels). Discerning unvoiced consonants presents an obstacle for hearing-impaired persons (i.e., ‘‘bark’’ and ‘‘park’’ may sound identical). A scheme is proposed, using chirped wavelets, to seize the characteristics of broadband speech elements. The method is tested on speech data, in noise-free and noisy conditions, and compared with sinusoidal-based wavelets. Results demonstrate that chirped wavelets are useful in the analysis and enhancement of speech for the hearing impaired. It is hoped these techniques might be incorporated in future hearing aid design.
Local characteristics of dispersive pulse propagation
Authors: Loughlin Patrick J.
Published: October 2013

As a wave propagates, its shape and other physical characteristics may change, depending on the initial wave and the propagation environment. In this talk, the effects of structural dispersion on the spatial and temporal spreading of a propagating pulse wave, and on the spectral characteristics of the pulse over time, are considered. These effects are quantified by obtaining the local spatial, temporal, and spectral moments of the pulse. General results for any dispersion relation, as well as the particular case of a two-plate waveguide, are presented. [Work supported by ONR.]
Cloud cavitation effects in shockwave lithotripsy
Authors: Colonius Tim , Tanguay Michel
Published: October 2013

Cavitation has already been identified as an important damage mechanism in the comminution of kidney stones in shockwave lithotripsy (SWL). However, the precise conditions that maximize the damage caused by the collapsing bubbles are still unknown. Numerical simulations are used to investigate shock propagation and the consequent growth and collapse of a bubble cloud in the focal region of a lithotripter. In the simulations, a continuum two-phase flow model for the ensemble-averaged macroscale is coupled to a Gilmore model for individual spherical bubble dynamics at the microscale. The simulations show agreement with experimental pressure measurements and high-speed photography of the bubble cloud. At void fractions commensurate with experiments, it is found that the collective collapse of the bubble cloud provides a significant increase to the energy available for comminution (beyond what a single bubble would produce). Relatively small increases in the pressure at the center of the cloud in advance of collapse (two orders of magnitude smaller than the initial shock) can more than double the energy of the collapsing bubble.