bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal change in memory of human voice
Authors: Kido Hiroshi , Kasuya Hideki
Published: October 2013

This study investigates the extent to which human subjects accurately retain memory of speaker individuality and voice quality of utterances without receiving instruction to memorize them. Experiments constituted three phases. In phase one, 27 subjects listened to two target utterances in a paired-comparison test that required only a similarity judgment of voice quality. The target utterances were one sentence read by two males with average and characteristic voice quality, respectively, who were selected from 109 males. In phase two, performed 21 days after phase one, the same subjects evaluated Japanese expressions of voice quality [Proc. ICSLP-98, No. 1005] of the two previous target utterances based on memory only and judged with a degree of confidence whether each of seven speech stimuli (two targets and five additional speakers’ utterances) was identical to one of the two targets. In the final phase, conducted immediately after phase two, the subjects repeated the same phase-two task but after listening to the two target utterances. Data processing based on the signal detection theory revealed that temporal change in memory of speaker individuality and voice quality was relatively small over a period of 21 days. Experiments over a longer period of time are now underway.
The application of chaotic dynamics, synchronization, and parameter estimation in an asymmetric vocal fold system
Authors: Zhang Y. , Jiang J. J.
Published: October 2013

Methods from nonlinear dynamics, including Poincare map, Lyapunov exponent and dimension, are applied to describe the vibrations of a vocal fold model with tension, stiffness, and mass imbalances. Bifurcation diagrams illustrate the effects of these imbalance parameters. When tension, stiffness, and mass imbalance parameters deviate from the normal value of 1, chaotic vibrations with positive Lyapunov exponents may occur. Furthermore, the technique of feedback synchronization allows us to manipulate a simulator to approach the vibratory patterns of an original vocal fold system. The minimal glottal area is applied as a feedback variable connecting between two systems. The simulator and the original system are synchronized when their state differences asymptotically converge to zero. The effects of noise and parameter mismatches on synchronization are investigated. Finally, a parameter estimation scheme based on feedback synchronization is applied. Despite noise perturbations and large initial parameter mismatches, the original system parameters can be reproduced in the simulator with parameter controls, and two chaotic vocal fold systems can be synchronized. A parameter estimation scheme shows the potential application to extract asymmetric biomechanical parameters of the vocal folds from a time series of the glottal area. [Work supported by NIDCD Grant No. R01 DC006019-01.]
The feature [stiff] interacts with intonation to affect vocal-fold vibration characteristics
Authors: Hanson Helen M.
Published: October 2013

As part of a larger study of the effect of prosody on segmental cues, previous work has shown that in a high pitch environment, F0 is significantly increased relative to a baseline following voiceless obstruents, but F0 closely follows the baseline following voiced obstruents. When a syllable carries a low or no pitch accent, F0 is increased only slightly following all obstruents. It is suggested that this difference occurs because demands of the segmental and prosodic levels of speech production conflict. In particular, results support a theory that the primary feature of voiced or voiceless obstruents is [.-stiff] or [+stiff] vocal folds, respectively. Enhancing features such as [-.spread] or [+spread] vocal folds are secondary. In a high pitch environment, the feature [-.stiff] conflicts with the need to raise pitch. Because of enhancing gestures, the prosodic level can override the segmental. Likewise, in a low pitch environment, the feature [+stiff] conflicts, so the vocal folds will not be stiffened for voiceless obstruents. If so, one might expect that stop consonants in low pitch environments will have longer or stronger prevoicing than in high pitch environments, and preliminary data show that speakers do show this tendency. [Work supported by NIH Grant DC04331.]
Acoustic characteristics of whispered vowels
Authors: Kiefte Michael
Published: October 2013

It is well known that whispered speech is able to convey information that is normally associated with pitch. For example, it is possible to whisper the question ‘‘You are going today?’’ without any syntactic information to distinguish this sentence from a simple declarative. It has been shown that pitch change in whispered speech is correlated with the simultaneous raising or lowering of several formants [e.g., Kallail and Emanuel, J. Speech Hear. Res. 27, 245–251 (1984)]. Data will be presented from 81 native speakers of English from the Halifax region of Nova Scotia (35 men and 46 women) who were asked to phonate and whisper the vowels /i,I,e,ε,æ,≳,o,U,u,■,■,■I,aU,aI/ at three different pitches across a range of roughly a musical 5th. Formant frequency variability is much greater for whispered vowels with different intended pitches resulting in much greater between-category overlap. Listeners’ categorizations of these stimuli will be reported as well as results from a discriminant analysis based on either static or dynamic spectral information. [Work supported by SSHRC.]
Perception of source spectral slope
Authors: Kreiman Jody , Gerratt Bruce R.
Published: October 2013

Researchers broadly agree that the spectral slope of the voice source is an important concomitant of voice quality, but it is unclear which specific aspects of spectral slope are perceptually important. To examine this issue, 50 voice samples were inverse filtered, and a large variety of measures of spectral slope were calculated for the resulting source pulses. Factor analysis was applied to determine which of these measures of slope are in fact independent. Synthetic copies of the voices were generated. Listeners used a method of adjustment task to manipulate these independent aspects of spectral slope in the synthesizer so that the synthetic copies matched the natural voice samples. Patterns of listener agreement and variability provide information about the perceptual relevance of different acoustic measures of source spectral slope. [Research supported by NIDCD.]
Nonlinear weighting techniques to replace tradeoffs between mainlobe width and sidelobe suppression
Authors: Dalrymple Dale B.
Published: October 2013

When the discrete Fourier transform is used to transform data from one domain to another as in narrowband beamforming or spectral analysis a weighting function can be applied as a vector multiplication before the transform or as a convolution after the transform to control mainlobe width in opposition to sidelobe suppression. Nonlinear operations applied to transform outputs or weighted versions of the transform outputs can combine mainlobe width control with sidelobe suppression. Applying weights before the transform requires the execution of multiple transforms for this process. The use of small kernals in the frequency domain on the output of a single transform provides a more efficient implementation. The set of small kernal summed cosine weights provides a variety of responses that can be combined nonlinearly retaining the best traits of each. Kernals can also be calculated adaptively.
Applications of beamforming and acoustic holography in an anechoic tank with surface reflections
Authors: Kim Sea-Moon , Choi Youngchol , Lim Yong-Kon
Published: October 2013

Recently, our institute, KRISO/KORDI, constructed a small anechoic tank which has an anechoic lining at the four walls and bottom. Because surface reflections still occur, special care must be taken for acoustic measurements and array signal processing, for example, source localization and acoustic holography. In this paper the effects of the surface reflections to the array signal processing methods are investigated. First, estimated errors by both methods are analyzed for various measurement parameters. Beamforming experiments with vertical line arrays are performed. Holographic reconstruction of simple and complex acoustic sources is also performed to compare the true and estimated results.
Modeling acoustic nonlinearities in marine sediments
Authors: McDonald B. Edward
Published: October 2013

Investigations into the theoretical and numerical treatment of acoustic nonlinearities in marine sediments are motivated by mine countermeasures and other Naval interests related to explosions in shallow water. Agreement between theory and data for the nonlinearity parameter B/A has been demonstrated in early papers concerning saturated sands. In the more general case involving varying depth profiles of air and silt contents, however, it is observed that B/A values vary so greatly that deterministic nonlinear modeling approaches may have to be augmented to address environmental uncertainty. Comparisons are given between B/A values derived from static consolidation tests and available in situ data. Numerical profiles from the NPE shock propagation model are given to demonstrate the effects of environmental uncertainty. [Work supported by the ONR.]
A single-scattering solution that handles large contrasts across interfaces
Authors: Kusel Elizabeth T. , Siegmann William L. , Collins Michael D.
Published: October 2013

Single-scattering and energy-conservation approximations have both proven to be effective for solving range-dependent ocean acoustics problems. The energy-conservation approach is usually used in acoustic models since it provides greater efficiency. The single-scattering approach is more general and more promising for problems involving elastic layers. A range-dependent medium is approximated in terms of a series of range-independent regions separated by vertical interfaces. The single-scattering solution is usually implemented in terms of an iteration formula, which may diverge when there is a large contrast in the material properties across an interface. Convergence can be improved by artificially splitting a vertical interface into a series of slices with smaller contrasts. For the idealized problem of scattering from a single stair step, a significant error may be introduced by neglecting multiple scattering between slices. However, the approach should be accurate for problems involving gradual range dependence, such as sloping interfaces. [Work supported by the Office of Naval Research.]
Sound propagation in shallow water with surface waves
Authors: Tindle Chris T. , Deane Grant B.
Published: October 2013

Wavefront modeling can be used to calculate acoustic pulse propagation in shallow water with real surface waves. The method uses ray tracing but phase and amplitude are found from approximations to a phase integral. The lowest order approximation is the conventional geometric ray. Higher order approximations describe caustics, shadow zones and focusing. Reflection from sloping curved boundaries also leads to a range dependent horizontal wave number and requires modification of the phase integral and phase derivatives. Results are in good agreement with an experiment in which 10-kHz short pulses were transmitted in shallow water with 0.8-m peak-to-trough surface waves and a sloping bottom. [Work supported by ONR.]
High-accuracy absorbing boundary conditions for high-order parabolic wave equations
Authors: Guddati Murthy N. , Heidari A. Homayoun
Published: October 2013

Using a new systematic approach, a novel set of arbitrarily high-accuracy absorbing boundary conditions (HABC) is introduced for high-order parabolic equations. HABC is derived by finite-element discretization of the boundary, followed by applying a special integration scheme and imaginary stretching. The resulting boundary condition is then coupled with the interior and can be solved with the same numerical method as the interior, e.g., finite differences. The accuracy of the HABC is controlled by two parameters: (1) the number of absorbing layers (the order of the HABC); and (2) a reference phase velocity for each layer. The latter controls the wave number for which the HABC absorbs the wave field exactly. Hence, the absorption range, i.e., the distribution of the reflection coefficient, can be controlled by the coefficient matrices of the HABC. A specially designed explicit finite-difference scheme is used to solve the HABC. The added computational cost due to the HABC is negligible for practical purposes. The performance of the proposed boundary condition is shown through numerical examples for high-order parabolic equations, for different orders of the HABC and different sets of phase velocity parameters. Effective absorption of both propagating and evanescent waves is illustrated in the results. [Work supported by NSF.]
A geometrical model for surface ship wake
Authors: Vasiliev Boris
Published: October 2013

High-frequency geometrical measurements of a surface ship wake collected by other research groups will be presented. The general trends in the width data agree with the previously published measurements; however, the trends in the depth data differ from those published in the literature. On-going efforts in data analysis to develop a high-frequency surface wake model that accounts for wake width, depth and persistence will be discussed.
Identifying modes that produce late arrivals for low-frequency long-range propagation in shallow water
Authors: DeFerrari Harry , Rypina Irina , Udovydchenkov Ilya
Published: October 2013

Model and data comparisons are presented for acoustic propagation over a frequency range from 100 to 3200 Hz (D=145 m, R=10 km). Above 0.8 kHz most all energy is reflected from the water–sediment interface. Arrival times of waterborne paths are in close agreement with normal mode and PE predictions when observed sound speed profiles are used as inputs. Generally, the received signal can be closely approximately with f/50 modes since steeper SRBR modes are attenuated. For frequencies below 0.5 kHz, arrivals from waterborne paths are still present, but an additional group of later arrivals is also observed. The timing of these arrivals suggests either late SRBR or more complicated modes from energy passing well into the bottom. Unfortunately, geoacoustic properties of the subbottom are not known for depth greater than a few meters. Bottom properties at depth are assumed and then propagation models are used to determine the modes that most likely produce the late arrivals. Some modes having group velocities that correspond to the arrival time of the late arrivals penetrate a few tens of meters into the bottom. Coherence in time and space is computed and compared for bottom penetrating and waterborne paths.
Probability density function methods for uncertainty analysis in underwater acoustics
Authors: James Kevin R. , Dowling David R.
Published: October 2013

Forward modeling of underwater acoustic propagation is generally successful when environmental parameters and boundary conditions are known. Unfortunately, such information is seldom available at the requisite level of precision, and any imprecision introduces uncertainty into sound field predictions. Quantifying this sound-field uncertainty is important for applications of acoustic propagation models such as matched-field processing. This presentation describes a method for quantifying the underwater-sound-field uncertainty arising from imperfect knowledge of the environment and its boundaries. It is based on formulating and solving a transport equation for the joint probability density function (PDF) of the real and imaginary parts of a harmonic sound field. The appropriate equation is obtained by combining spatial derivatives of the PDF with physical laws drawn from guided wave mechanics. The inputs for solving the PDF-transport equation are known or assumed distributions of the uncertain parameters. Solutions can be readily reduced to expected values, uncertainties, and confidence intervals for the predicted sound field. Results for simple test cases involving range-independent isospeed underwater sound channels are considered, and compared to solutions obtained analytically or through Monte Carlo simulations. [Work sponsored by ONR.]
Five sensitivities of the coupled volume/double sloped system
Authors: Ermann Michael
Published: October 2013

Stop chord measurements taken in an existing coupled volume concert hall, established statistically-based formulas, ray-tracing-software simulations, and headphone listening perception/preference studies imply a fickle relationship between the coupled volume concert hall, the double-sloped sound decay, and the listener. The two halls examined in this study suggest five sensitivities of the system: (1) To produce a double sloped sound decay, the coupled volume must be exceedingly more reverberant than the main hall to which it is attached. (2) To produce a double sloped sound decay, the sonic aperture linking the coupled volume to the main hall must be exceedingly small. (3) Maintaining low levels of background noise—always essential when designing spaces for music listening—is especially important if the double sloped impulse response is to be perceived above the noise floor. (4) Listeners who sit near the apertures probably hear something different than those who sit nearer to the center of the hall. (5) It is unclear whether subjects taking a paired comparison test prefer a double sloped auralization to a classic Sabine auralization.
Acoustical decoupling of a dome: The adaptive reuse of historic Angelus Temple
Authors: Conant David
Published: October 2013

With its 128-foot-wide, unsupported concrete dome springing 125 feet above the floor of its quarter-circle plan, the original 5300-seat mother church of the International Church of the Foursquare Gospel in Los Angeles (circa 1923) required adaptive reuse as a rock-n-praise Christian church. Challenges included squelching its 7-s RT60, decoupling the dome by eliminating its unusually severe focusing (largely responsible for repetitive echoes), especially strong at the intended audio mix position and stage, integrating acoustical and audio systems design to achieve 118 dBA uniformly throughout, while meeting full operation for opening services within 7 months. Because of its structurally weak dome and its National Register status, the principal acoustical solution prohibited covering, or supporting anything from, the focusing dome. Described is a method not known to have been applied elsewhere intervening about 95% of all the problematic, focusing sound rays with large suspended baffle/absorber panels specifically designed and positioned via laser model studies while achieving an attractive, dramatic array. The result is remarkably successful with respect to all intended acoustical, audio, and historical architecture goals.
Evoked-potential study of automatic gain control in the sonar of a false killer whale
Authors: Supin Alexander , Nachtigall Paul , Au Whitlow , Breese Marlee
Published: October 2013

Brain auditory evoked potentials (AE’s) were recorded in a false killer whale Pseudorca crassidens trained to accept suction-cup EEG electrodes and to detect targets by echolocation. AEP collection was triggered by echolocation pulses transmitted by the animal. The target strength varied from 22 to 40 dB; the distance varied from 1.5 to 6 m. All the records contained two AEP sets: the first one of a constant latency (transmission-related AEP) and a second one with a delay proportional to the distance (echo-related AEP). The amplitude of echo-related AEPs was almost independent of both target strength and distance, though combined variation of these two parameters resulted in echo intensity variation within a range of 42 dB, thus indicating automatic gain control (AGC). The amplitude of transmission-related AEPs was independent of distance but dependent on target strength: the less the target strength, the higher the amplitude. Recording of transmitted pulses has not shown variation of their intensity depending on target strength. It is supposed that AGC mechanisms are a variation of hearing sensitivity depending on the target strength and release of echo-related responses from masking by transmitted pulses depending on the distance. [Work supported by ONR (USA) and RFBR Ministry of Science (Russian Federation).]
Estimation of the acoustic reflectivity of a Florida manatee from physical measurements of animal tissue
Authors: Simonet Fernando , Jaffe Jules J. , Bowles Ann E.
Published: October 2013

In order to better understand the cause of low acoustic reflectivity of the Florida manatee (Trichechus manatus latirostris), a series of measurements were taken from a stranded animal post-mortem. The samples came from an adult male that was struck and killed by a boat in April 2004. These measurements were used to calculate the speed of sound, density and attenuation within each sample. To achieve a good statistical representation, many subsamples (connective tissue, blubber and muscle) were extracted from ventral, dorsal and lateral samples collected from approximately the midpoint of the body (at the umbilicus). Results for the connective tissue samples indicate an average sound speed, density and attenuation of 1725 m/s, 1089 kg/m3 and 5.21 dB/mm, respectively. These results establish a reflection coefficient of 0.12, or, in other words, only 12% of the incident acoustic wave is reflected in the water–skin interface.
In situ measurement technique for compressional wave velocity dispersion
Authors: Holland Charles W. , Dettmer Jan , Dosso Stan E.
Published: October 2013

Marine sediments can be considered a two-phase medium composed of solid sediment particles and fluid-filled interstices. Many theories of propagation through such an assemblage predict a dispersive compressional wave velocity. Granular sediments (i.e., sands and gravels) have been predicted and reported to exhibit velocity dispersion and/or a nonlinear frequency-dependent attenuation in the frequency range 102−104 Hz (Kramers–Kronig relations require velocity dispersion if a nonlinear frequency-dependent attenuation is observed). One of the experimental challenges has been to measure velocity over several decades of frequency using a single technique so that observed velocity changes cannot be due to different biases in the measurement techniques. A simple in situ measurement technique is described that measures the critical angle as a function of frequency from ∼102−104 Hz and thus infers the velocity dispersion over that band. Measurements on the mid to outer continental shelf (Malta Plateau and the New Jersey shelf STRATAFORM area) show little or no velocity dispersion. This implies that the compressional wave attenuation for these sediments is linear or nearly linear over this band. [Work supported by the ONR and NATO Undersea Research Centre.]
Subbottom profiling using a ship towed line array
Authors: Yang T. C. , Yoo Kwang , Fialkowski Laurie
Published: October 2013

This paper presents a technique for determining the effective depth of subbottom layers using a ship towed line array with a controlled source. Results are demonstrated using the MAPEX 2000 data. Local measurements of bottom layer thickness can be done using several methods: (1) Reflection profiling using a source and a receiver array at different ranges. (2) A high power downward looking boomer that can penetrate tens of meters of sediment layers. (3) A vertical line array using ambient noise. (4) Geo-acoustic inversion using acoustic data from a ship towed line array. The ship towed line array provides local measurements of the subbottom thickness without the requirement of high power sources and extended experimental setup, on one hand, and with minimal interference from shipping traffic on the other hand. We show here that a simple seismic profiling technique extended to the towed line array data provides the same thickness profile as obtained by other techniques. It agrees with the geo-acoustic inversion method but can be done in real time. Conversely, it can be used to initialize the geo-acoustic inversion program. [Work supported by ONR.]
Characterizing depth dependent geoacoustic properties of the seabed using layering and reflection loss information inferred from ambient noise
Authors: Siderius Martin , Harrison Chris
Published: October 2013

Vertically beamformed ocean ambient noise data can be used to infer bottom reflection loss over a broad band of frequencies. Seabed layering introduces a fringe pattern into the reflection loss curve that is related, through a Fourier transform, to the two-way travel time to significant reflectors (caused by layering). The two-way travel times can be used to infer number of layers and depths. In this paper, a global search algorithm is applied to find the sound speed, density and attenuation in each seabed layer. The search is directed by the quality of fit between modeled and inferred reflection loss with the two-way travel times used as an additional constraint. This method avoids one of the usual problems associated with geoacoustic inversion: predetermining the number of significant layers to parametrize the seabed. If too few layers are chosen, the solution does not describe the seabed in enough detail and choosing too many leads to ambiguities in some of the inverted parameters. We will present the application of this technique to simulated and measured data from experiments in the Mediterranean.
Estimation of particle sizes for a range of narrow size distributions of natural sands suspended in water using multifrequency acoustic backscatter
Authors: Smith Christopher , Wren Daniel , Chambers James
Published: October 2013

Particle size estimation of suspended sediment is an ongoing area of research in acoustics. A single transducer was used to measure multifrequency backscatter from a suspended sediment-carrying jet. A composite waveform composed of three frequencies was transmitted by the transducer. The sediment was composed of natural sand and covered a range of narrow size distributions. Amplitude ratios among the three frequencies were evaluated in the experimental data. The same ratios were predicted using scattering theory. The measured ratios were used with these theoretical equations to solve for an estimate of the particle sizes. The method works well at estimating large (300–850 micron) particle sizes, but overestimates the size of small (150–300 micron) particles.
Shallow water ocean sound speed estimation using travel times between multiple sources and receivers
Authors: Cornuelle Bruce D. , Roux Philippe , Akal Tuncay , Hodgkiss William S. , Kuperman William A. , Song H. C. , Stevenson Mark
Published: October 2013

A 29-element source-receiver array has been developed and used for time reversal mirror (TRM) experiments at 3.5 kHz. The TRM hardware also has been used to collect waveguide impulse responses between the source array and a 32-element receive array located about 10 km away in 100 m of water. The data were analyzed using standard time-of-arrival methods from large-scale ocean acoustic tomography. Stable arrival peaks with sufficient signal-to-noise ratios are tracked over the duration of the experiment and identified with ray-like arrivals as predicted by both ray tracing and full-wave propagation codes. We then adjust the ocean sound speed field, bottom topography, and array element locations to produce the best match between observed and predicted travel times, using ray paths as the observation kernels in the inversion. Even with an imperfect knowledge of the bottom topography, it is possible to make sensitive, relative inversions, converting changes in travel times to changes in array element locations and ocean sound speed, assuming the bottom does not change. [Work supported by ONR.]
Acoustic-oceanographic buoy—An easily deployable, reconfigurable, and multifunctional acoustic-oceanographic system
Authors: Jesus Sergio M. , Soares Cristiano , Silva Antonio , Hermand Jean-Pierre , Coelho Emanuel F.
Published: October 2013

The concept of an easy to use and easy to deploy ocean acoustic tomographic (OAT) system is presented. The system is composed of a network of buoys and a data inversion online processor. This study concerns the individual node of that network—the acoustic-oceanographic buoy (AOB)—the data inversion technique and the testing of the system at sea. The AOB is a lightweight surface buoy with a vertical array of acoustic and temperature sensors to be hand deployed in a free-drifting configuration from a small boat. The data are locally stored and transmitted online to a remote station for processing and monitoring. Data inversion is based on a broadband matched-field tomography technique where known and unknown parameters are simultaneously searched for (focalization). In situ recorded temperature data serve for algorithm initialization and calibration. The AOB was successfully deployed in several consecutive days during two rapid environmental assessment sea trials in 2003 (Mediterranean) and 2004 (Atlantic). Data collected at sea also show that the AOB can be reconfigured as a receiving array for underwater coherent communications in the band up to 15 kHz. [Work supported by FCT and Royal Netherlands Navy—Projects NUACE, POSI/CPS/47824/2002 and REA, RNLNC/2003/04.]
Dual frequency high intensity focused ultrasound to accelerate hemostasis
Authors: Bailey Michael R. , Maxwell Adam D. , Reed Justin A. , Kreider Wayne , Khokhlova Vera A. , Zderic Vesna , Vaezy Shahram , Crum Lawrence A.
Published: October 2013

In acoustic hemostasis, cavitation appears to help emulsify and heat tissue to form a paste which seals lacerations. Our objective was to mix two frequencies to enhance cavitation, increase heat deposition, and accelerate hemostasis. A focused transducer (curvature 5 cm) with a 4.3-MHz center element (diameter 2 cm) and a 125-kHz outer annular element (inner and outer diameters, 3 and 5 cm) was engineered. This dual frequency transducer was used to create lesions in a transparent gel phantom and to induce hemostasis in five rabbits. Hemostasis time was determined with both frequencies (4.3 MHz at 620 W/cm2, 125 kHz at 4 W/cm2) and with the high frequency only (4.3 MHz at 620 and 780 W/cm2). In gels, dual frequency HIFU created larger, broader lesions than 4.3-MHz HIFU alone. Bubbles created by just low frequency could be seen and, with sufficient time, created small local lesions. In rabbits, hemostasis times (∼1 min for 25-ml/min bleeds) were decreased 20% with dual frequency compared to the 4.3-MHz wave alone at the same intensity or same total electrical power. Dual frequency mixing can enhance heat deposition and accelerate hemostasis by HIFU. [Work supported by NSBRI SMS00203, NIH Fogarty, ONRIFO, and NSF BES0002932.]
Forward modeling of propagation and scattering of acoustic waves for hyperthermia treatment
Authors: van Dongen Koen W. A. , Wright William M. D.
Published: October 2013

Cancer is a major cause of death in the Western world, resulting in a high demand for effective therapies. Recently, there is increasing interest in treatment via high intensity focused ultrasound (HIFU) where ultrasonic waves are used to increase the tumor temperature to induce cell death. For successful treatment, information about the temperature is essential. Research is applied where temperature profiles are obtained via acoustic wavefields. In order to understand the measurements and to verify imaging methods the acoustic wavefields are modeled. The forward model is based on a nonlinear integral equation of the second kind, obtained via reciprocity from the acoustic wavefield equations. The integral equation relates the unknown total wavefields with the known incident wavefields and inhomogeneities in density and compressibility. A conjugate gradient method is used to solve the integral equation to obtain a solution for this ill-posed problem. To reduce the computational costs, a technique called ‘‘marching on in anything’’ is applied in both the temporal and the spatial domain. This technique is especially successful where wavefields have to be computed for various transducer positions. Results will be shown where the propagation and scattering of acoustic waves are modeled by using the above method.
Computational methods for imaging small temperature changes using ultrasonic through-transmission tomography for thermal cancer treatment
Authors: Bograchev Konstantin , Wright William M. D.
Published: October 2013

During thermal cancer treatment there are small temperature fluctuations (37–42.5°C) inside the human body. These fluctuations are very important to monitor for quality cancer treatment. For monitoring deep seated fluctuations it is effective to use ultrasonic through-transmission tomography. Computer modeling of temperature fluctuation reconstruction using the above technique has been carried out. The model considers a fan-bean tomography scheme (60 sensors, 2160 rays in total) and iterative techniques for solving the inverse problem. It also assumes the 2D temperature is being reconstructed in an area of tissue of 60×60 mm2 size, and the temperature fluctuation size is 6.5 mm in diameter. Such heated regions can appear, for example, during thermal treatment using high intensity focused ultrasound (HIFU). Algorithms for solving the inverse problem using algebraic iterative methods (including EM and ART) have been developed. The model takes into account electronic measurement noise and angle positioning errors. The model uses bilinear interpolation and takes into account the interpolation error. It also takes into account a priori information about the heating process. It was shown that it is possible to reconstruct the above temperature fluctuation with a good quality.
Improved exposimetry on diagnostic ultrasound equipment using broadband complex-valued hydrophone frequency responses
Authors: Wilkens Volker , Reimann Hans-Peter
Published: October 2013

Nonideal hydrophone frequency responses may impede correct acoustic output measurements on medical ultrasound equipment, in particular when high-frequency or nonlinearly distorted waveforms have to be detected. However, correct pressure waveforms and the associated standard pulse parameters can be obtained by impulse deconvolution if the nonideal frequency response of the hydrophone M(f) is provided with high frequency resolution both in amplitude and phase in a broad frequency range. The complex-valued calibration data required can be obtained by a novel secondary hydrophone calibration technique using broadband, nonlinearly distorted, focused ultrasound pulses and a very broadband optical multilayer hydrophone as reference receiver. The calibration data obtained for a bilaminar membrane hydrophone are applied to improve exposure measurements on a commercial diagnostic ultrasound machine. In comparison to the results obtained by the proposed pulse deconvolution method using the complete broadband complex-valued transfer function M(f), an overestimation of the positive peak pressure by up to 50%, an underestimation of the rarefactional peak pressure by up to 11%, and an overestimation of the pulse intensity integral by up to 28% are found if the common evaluation method using the voltage-to-pressure transfer factor at the acoustic working frequency M(fawf) is applied.
Stiff piano string modeling: Computational comparison between finite differences and digital waveguide
Authors: Bensa Julien , Bilbao Stefan , Kronland-Martinet Richard , Voinier Thierry , Smith Julius O.
Published: October 2013

As is well known, digital waveguides offer a computationally efficient, and physically motivated, means of simulating wave propagation in strings. The method is based on sampling the traveling wave solution to the ideal wave equation and linearly filtering this solution to simulate dispersive effects due to stiffness and frequency-dependent loss; such digital filters may terminate the waveguide or be embedded along its length. For strings of high stiffness, however, dispersion filters can be difficult to design and expensive to implement. It is shown how high-quality time-domain terminating filters may be derived from given frequency-domain specifications which depend on the model parameters. Particular attention is paid to the problem of phase approximation, which, in the case of high stiffness, is strongly nonlinear. Finally, in the interest of determining the limits of applicability of digital waveguide techniques, we make a comparison with more conventional finite difference schemes, in terms of computational cost and numerical dispersion, for a set of string stiffness parameters.
Interconnecting digital waveguides and finite difference structures: Recent advances
Authors: Karjalainen Matti , Erkut Cumhur
Published: October 2013

Digital waveguides and finite difference schemes have been generally considered as alternative techniques in physical modeling of spatially distributed systems. The main difference between these techniques is in the variables used in the computation; in digital waveguide simulations traveling-wave components are used, whereas physical variables are typical in finite difference schemes. Although both techniques are known to provide exact modeling of ideal one-dimensional band-limited wave propagation and both of them can be composed to approximate higher-dimensional mesh structures, they usually become computationally different in the presence of losses, dispersion, and nonlinear interactions. Despite these differences, successful examples of hybrid waveguide/finite-difference models have been proposed in the literature. In these references, the finite-difference sections typically account for local nonlinear interactions. More recently, a general, unifying, and DSP-oriented framework is introduced, where the functional equivalence of digital waveguides and finite difference schemes is systematically elaborated and the conditions of building mixed models are studied. The present lecture will summarize the new framework and provide demonstrations of hybrid models. Real-time sound examples will be presented. [Work supported by EU ALMA project (IST-2001-33059).]
The digital waveguide mesh: Applications in acoustic modeling and current research directions
Authors: Murphy Damian T.
Published: October 2013

The digital waveguide mesh (DWM) was first introduced as a modeling technique for musical acoustics applications in 1993 as a natural extension to the 1D digital waveguide that is widely used in physical modeling sound synthesis. DWM related work at York has focused on a number of areas with notable results including reverberation simulation using the 2D triangular mesh, modeling enclosed spaces with the 3D tetrahedral mesh, improved anechoic absorbing boundary conditions (ABCs) and the analysis and validation of spatial properties of DWM-based room impulse response measurements. This paper presents recent results from three current areas of research. RoomWeaver is a development environment that facilitates research into the application of DWM-based models for virtual acoustic spaces, incorporating new hybrid mesh-types in 2D and 3D through the use of KW-pipes. The second parallel research area involves the development of new boundary formulations that extend the anechoic ABC to the more general frequency dependent case with variable diffuse reflection control. Finally, Digitract is a speech synthesis research tool based on a 2D DWM model of the human vocal tract that offers improved control over formant bandwidths and greater naturalness in the production of speech sounds.
Equivalence of the digital waveguide and finite difference time domain schemes
Authors: Smith Julius O.
Published: October 2013

It has been previously understood that the finite difference time domain (FDTD) method for numerically solving partial differential equations is equivalent to the digital waveguide (DW) method over the DW solution space. However, prior references have assumed that the DW solution space is a strict subset of the FDTD solution space, so that the FDTD method exhibits solutions not available in the DW method. In this talk, based on arXiv.org e-print physics/0407032, we show that there is in fact a one-to-one correspondence between the two solution spaces, and we give a simple, explicit transformation for the 1D case (e.g., for modeling vibrating strings). The ability to transform FDTD models to DW models and back provides a means of guaranteeing passivity and/or stability of specific FDTD models with specific boundary conditions. Furthermore, wide classes of passive boundary conditions can be specified for the FDTD method based on the linear transformation of known passive terminations in the digital waveguide case. Similarly, physically precise FDTD excitations (input signals) can be defined based on their DW counterparts.
Spectral accuracy of numerical integration schemes for acoustic simulation
Authors: Amuedo John
Published: October 2013

Physical simulation of time-dependent acoustical systems often requires advancing one or more state derivatives of such a system forward in time. Design of a discretization for such a system, and choice of particular numerical integration methods within an acoustical model, determine its physical integrity, numerical accuracy, stability, and realizability. Selection of an appropriate discretization and integration approach requires balancing indigenous numerical properties of a physical model, desired physical accuracy of results, stability constraints on allowable time-step size, computational complexity, and memory requirements. Physical simulation of musical instrument and cochlear mechanics may impose additional demands on physical accuracy, as choice of a particular computational method colors perceptual fidelity of audio output. This talk analyzes magnitude and phase errors, and stability characteristics of zero- through fourth-order members of the families of numerical integrators most commonly employed for solving time-dependent acoustics problems. The methods compared include explicit Adams–Bashforth predictors, implicit Adams–Moulton correctors, backward differentiation integrators, and conditionally stable schemes including the Simpson, Tick and ‘‘leap frog’’ methods.
Robert W. Young, acoustical consultant, 1940 to 1990
Authors: Eilar Douglas K.
Published: October 2013

Robert Young was hired by Vern O. Knudsen in the early 1940s to assist in the acoustical research work being conducted in support of the U.S. Navy’s efforts to develop improved methods to use sound signals to detect and monitor ships and submarines. In this capacity, Bob served as an in-house consultant on all acoustical aspects of that work. After the war, Bob Young formed a partnership with Bob Gales to provide acoustical consulting services for a large variety of clients. Consulting activities included projects in architectural acoustical design, measurement and evaluation of environmental or community noise, neighborhood noise complaints, and the development of acoustical criteria for use in city and county noise ordinances. Bob Young also helped draft the noise regulations of the State of California. This paper describes highlights of some of the acoustical consulting work undertaken by Robert Young over five decades from the 1940s to the 1990s.
The impact of Robert Young on national and international standards
Authors: Schomer Paul
Published: October 2013

Bob’s enthusiasm and active participation in standards from modest beginnings for the Z24 Committee in the 1950s to the important needs for national and international standards in the 1960s to the 1990s was truly remarkable. Bob was a most-conscientious and detailed reader of drafts, redrafts, and new editions of documents for IEC/TC 29, ISO/TC 43 and SC 1, ISO/TC 108, and our four ANSI S-Committees. He collected and used his own experiences and even conducted his own experiments to obtain data to support his proposals. Among other areas, Bob worked for 50 years on national and international Standards related to instruments, measurements, terminology, and scales and ratios for plotting. Bob was noted for his perseverance; if he believed in something, he had to make it happen. Some things that Bob had to make happen were the use of A-weighting and time-average for measurement and evaluation of environmental noise; here he was quite successful. Bobs achievements over a 50-year Standards history helped to push the USA and the world towards better acoustical instruments and measurements, clearer and more-consistent acoustical terminology, and clearer graphs and figures, but with a continuing effort to avoid dBA as the unit of A-weighted sound level.
Contributions of Robert W. Young to the understanding of Space Shuttle sonic booms
Authors: Young Evelyn C. , Young T. L.
Published: October 2013

From 1981 to 1993, Robert W. Young measured 30 sonic booms generated during Space Shuttle landings at Edwards Air Force Base. The chronology of these measurements is based on the recollections of Evelyn Young who assisted Robert Young on all of these excursions. From the early days of the first Space Shuttle landings, with their unknowns of flight paths and landing times, to the routine landings 12 years later, the successes, failures, challenges, and results are described. Anecdotes complete a picture of the effort needed to accumulate the acoustical records that resulted in the presentation of six papers in the period from 1984 to 2002 relating to Space Shuttle landings. Excerpts from the paper ‘‘Sonic Booms of Space Shuttles approaching Edwards Air Force Base, 1988-1993’’ are presented to illustrate the ground tracks, flight paths, and sonic boom waveforms of landings of the Shuttles Columbia and Atlantis.
Bob Young and his contributions to animal bioacoustics and underwater acoustics
Authors: Cummings William C.
Published: October 2013

Quintessential component and Past President of ASA, Robert W. Young was truly a scientist par excellence for all seasons. His professional accomplishments excelled in large measure with outstanding assistance of his talented wife, Evelyn. Whether noise, psychoacoustics, architecture, propagation, music, patents, underwater sound, animal bioacoustics, or other discipline(s), his trademark was always distinguished by elegant design and very proper presentation. Whenever new or experienced co-workers needed a bit of correction or retuning, Bob Young (known to many of us as ‘‘Uncle Fussy Ears’’) was the one to seek for sage guidance. All contemporary acoustics manuscripts from the Naval Electronics Laboratory (NEL), later Naval Ocean Systems Center (NOSC), had to pass his scrutiny. The wise chose to seek early comment from Bob Young or chance the possibility of endless editorial notations or internal memos, oftimes pages long. For example, one quickly learned never to describe a whale’s sound as ‘‘loud’’ in lieu of ‘‘high sound source level.’’ With a few examples of his pioneering studies on animal and underwater acoustics we’ll revisit some of Bob Young’s early landmark contributions and hear about a rare privilege of being so close to such authority, propriety and exactitude.
Robert W. Young and the A-weighting for acoustical measurements
Authors: Wong George S. K.
Published: October 2013

In 1985, the ASA Technical Committee S1: Acoustics, drafted the amendment ANSI S1.4A to the current sound level meter standard ANSI S1.4-1983. The aim was to provide A-weighting tolerances to frequencies above 16 kHz for measurement of short-duration transient signals. Dr. Young gave a lot of support during the preparation of that amendment. The current international sound level meter standard IEC 61672-1 (2002): Specifications, has A-weighting tolerances that allow less capable microphones to be used in Class 1 instruments. Under the above IEC standard, microphones that are not capable of measuring sound beyond 16 kHz can be used in IEC Class 1 sound level meters. Some pros and cons will be discussed.