bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of acoustic radiation force in contrast enhancement techniques using bubble-based ultrasound contrast agents
Authors: Fowlkes J. B. , Gardner E. A. , Ivey J. A. , Carson P. L.
Published: October 2005

The movement of bubbles in an acoustic field has recently been used to manipulate bubbles for the purpose of contrast enhancement in medical applications. Some ultrasound contrast agents consist of stabilized microbubbles which, when exposed to an acoustic field, can be collected at specific points in space and may be moved by translating the field. One application for this type of bubble manipulation is the collection of bubbles within the urinary tract for urinary reflux diagnosis. Experiments conducted on sacrificed dogs indicate that bubbles can be moved in a controlled fashion within the bladder using external acoustic fields. In addition, acoustic radiation force could be used to overcome hydrodynamic forces in flowing blood. Bubbles could be pushed to a vessel wall to collect contrast and when the sound field was turned off, a bolus of contrast agent would reenter the flow for measurement of tissue perfusion. In preliminary experiments, a bolus of bubbles was created in blood flowing through dialysis tubing. This paper will review these experimental findings and present an examination of the mechanisms involved in each application. [Work supported in part by USPHS Grant No. DK-42290.]
Feasibility of a mechanical waveguide to control the ultrasonic field in pulsed Doppler blood flow measurement
Authors: Finneran James J. , Hastings Mardi C.
Published: October 2005

The location and size of the sample volume is of considerable importance in pulsed Doppler blood flow detection and velocity measurement. This study examines the feasibility of using a mechanical waveguide to control the ultrasonic field (and thus the sample volume size) of a flat disk transducer operated in pulse-echo mode. The waveguide controls the axial location of the natural focus and the lateral beam width at the natural focus. Experimental measurements are compared to theoretical results derived from a transient field model of the pulse-echo system. Results confirm that the waveguides offer a potentially useful and inexpensive means of altering the pulse-echo field of a flat disk transducer. [Work supported by NSF Grant No. MSS 9058607.]
The relative contributions of targets and distractors in laterality judgments
Authors: Dye R. H.
Published: October 2005

A stimulus classification paradigm that allows the estimation of the relative contributions of target and distractor components of judgments of perceived laterality was used to assess the effect of frequency separation (Δf). A 753-Hz tone was the target and the distractor was 553, 603, 653, 703, 728, 778, 803, 853, 903, or 953 Hz. The duration of the tones, which were gated simultaneously, we either 25 or 100 ms. Each block of 100 trials presented the target and the distractor at ten different interaural delays, with each combination presented once. Preceding the test interval was a diotic presentation of the target. Subjects indicated whether the target component appeared to the left or right of the intracranial midline. Left–right judgments were plotted as a joint function of the target and distractor delays. The slope of the best-fitting linear boundary between left and right responses was used to estimate the relative weights given to the target and the distractor. The target weights were greater for 100-ms durations and decreased as Δf fell below 100 Hz. For all conditions, left–right judgments were partially dependent on distractor delay. [Work supported by NIH.]
Auditory spatial resolution in the horizontal plane as a function of reference angle: Microstructure of the azimuth function
Authors: Chandler David W. , Grantham D. Wesley , Leek Marjorie R.
Published: October 2005

Auditory spatial resolution in the horizontal plane was measured in five normal-hearing subjects by determining the minimum audible angle (MAA) for brief 1.0-kHz tones. Using a left–right discrimination paradigm, MAAs were determined for 22 reference azimuths ranging from −62° to +63°. The gross pattern of the mean data was similar to that reported previously for more sparsely sampled azimuth functions: spatial resolution tended to be best when the reference sound was near midline, becoming worse as the reference moved toward the periphery. However, there were remarkable asymmetries and nonmonotonicities in individual subject’s MAA versus azimuth functions, and these nonmonotonic features were highly subject-dependent. Although such individual differences may be due partly to differences among subjects in head and pinna shape, it is possible that the highly individual and idiosyncratic MAA functions also reflect subject-dependent nonmonotonicities in the underlying interaural time difference (ITD) discrimination functions as reference ITD is varied in fine increments. [Work supported by NIH and by the U.S. Army.] a)Current address: ENT/Audiology (HSHJ-SET-A), Madigan Army Med. Ctr., Tacoma, WA 98431-5374.
Use of auralization to accomplish small elevation shifts of a loudspeaker in the median plane
Authors: Bowen David L. , Blauert Jens
Published: October 2005

The use of frequency domain equalization to change the perceived elevation of a loudspeaker over a fairly small range in the frontal plane (±20°) will be described. Because of the application (the center channel speaker in home video theater), several constraints were in effect. Among these were (1) the effect must be applicable over a broad range of people, and over a fairly broad listening area, (2) the equalization applied must not introduce an objectionable amount of ‘‘coloration’’ into the sound, and (3) the resulting circuit must be feasible to implement into a consumer product. The procedure used was to first determine equalizations from ratios of head-related transfer functions measured on an artificial head and on human subjects. Salient features were then determined and implemented in hardware for listening tests, where further refinements took place. Despite a common assertion that there is little directional dependence in the median plane below 4–5 kHz, listening tests indicated a more convincing effect took place when several features below 4 kHz were included in the equalizations. It was also found effective to include a feature at 12.5 kHz, even if source material was limited to male speech. The results of demonstrating a 20° to 0° ‘‘delevator’’ to 125 groups of 12 people will also be discussed. [Work supported by Thomson Consumer Electronics.]
Active systems for attenuation of noise
Authors: Angevine O. L. , Jessel M. J. M.
Published: October 2005

Both theoretical studies and experience with active systems for noise reduction disclose constraints necessary for successful systems. These include the following. (1) Topologicalfitness: A net of antisources suitable to the primary noise source. (2) Densityofcancellers: Quite different results are produced by dense than by sparse arrays. (3) Directivity: Different results are achieved by directional cancellers than by nondirectional ones. (4) Causality: Cancellation requires repetitive patterns of the noise to be attenuated, or the ability to sample the noise to be canceled earlier than the production of the antinoise by the time interval needed for processing the data. Some consequences of these constraints are discussed. a)Present address: L’Aragon F-13008, Marseille, France.
Ultrasound enhanced generation of hydroxyl radicals from anticancer drugs: Adramycin and Mitomycin C
Authors: Tata Darayash , Tritton Tom R. , Wu Junru
Published: October 2005

It has been reported that OH production in anticancer drug Adramycin and Mitomycin C suspensions is dramatically enhanced by applying 0.5-MHz cw ultrasound (US). Time course studies were performed to characterize the OH generation with and without US exposures. The results show that to a first approximation [OH] can be expressed as superposition of a rapid exponentially growing term and a slow linear varying term. The experiment indicated that the first term is due to US. In view of these observations it is concluded that US activated some shortly lived OH generating pathways.
Performance transmission loss and the ‘‘high low’’ rating method for predicting and measuring sound resistance of walls, ceilings, and floors
Authors: Paige Tom
Published: October 2005

This method uses a two-number rating system as opposed to the single-number rating used in the STC method. The advantage of using two numbers is to distinguish between the speech- and low-frequency sound transmission loss performance. This makes the rating useful for applications involving music sources or mechanical system noise, in addition to speech-frequency applications to which the STC method is limited. The two numbers correspond to the speech-frequency performance transmission loss (SPTL) and the low-frequency performance transmission loss (LPTL). As explained in this paper, SPTL and LPTL predictions and measurements are a function of the source spectrum, the receiving-room noise criteria and the sound transmission loss data. When applied to common wall, floor, and ceiling constructions, SPTL and LPTL predictions correlate very well with measurements in the 500- and 125-Hz octave bands, respectively, thus simplifying field testing for performance verification.
Review of collected data for the experimental checking of a new reverberation time formula
Authors: Stanzial Domenico , Carletti E. , Brambilla G. , Fausti P.
Published: October 2005

The experimental checking of a new reverberation time equation proposed by D. Stanzial in a recent paper [D. Stanzial, ‘‘A heuristic approach to reverberation time in acoustics, based on energy transfer,’’ submitted to J. Acoust. Soc. Am. (1992)] has been carried out in rooms of different size and different acoustic absorption characteristics. Although not rigorously true in a general acoustic field situation, the experimental checking of the new formula has been accomplished ‘‘in a standard way’’ using the measurement of the T60 reverberation time directly obtained as the decay time of the squared acoustic pressure. On the right side of the reverberation time formula, T60=γ{−0.166[1/ln(1−α)]+0.012[ln(α)/ln(1−α)]−0.012}, the local acoustic absorption coefficient α has been determined, for each testing room, from active and reactive sound intensity measurements. A review of the collected data as well as a first analysis of the experimental checking are reported here.
Hot topics in physiological acoustics: The adaptive cochlea
Authors: Zwislocki Jozef J.
Published: October 2005

There are several areas of hot topics in physiological acoustics. However, from the point of view of acoustics, the cochlea that both transmits sound and transduces it into electrochemical events that initiate the digitized neural code must be the closest to an acoustician’s heart. The cochlea has been a hot topic since the discovery in the late 60’s that a live cochlea acted in a different way from a passive post-mortem one. Subsequent discoveries revealed that it was able to emit sound and that its mechano-electrical transducers of one type, the outer hair cells, were bidirectional and also acted as electromechanical transducers, providing in this way a feedback loop. Now it has been found that neither the cochlear transfer functions nor its input–output functions are invariant, but that they change with the intensity and duration of sound. These nonlinear dynamics suggest explanations for the nonlinear growth of loudness with sound intensity and for the shift between the frequency of a damaging sound and the frequency of maximum hearing loss. They also show that the location of maximum cochlear excitation cannot be a code for subjective pitch.
The effects of deviation and phase disparity of frequency and amplitude modulation on musical blend
Authors: Goad Pamela J.
Published: October 2005

Two experiments tested the effects of deviation and phase disparity of frequency and amplitude modulation on an aspect of musical blend referred to as fusion. The experimental procedure was a two-alternative forced choice design. The stimuli were two simultaneously presented complex tones in a musical interval of a major sixth. The spectral envelopes of the complex tones were similar to oboe tones at fundamental frequencies of 312 and 523 Hz. These tones were modulated by a sinusoid at a rate of 5 Hz. Frequency and amplitude deviations representative of musical instrument vibratos were constructed with peak frequency deviation varying by 0% (unmodulated), 1.0%, and 2.2%. Amplitude modulation indices were subjectively matched to the tone quality of the frequency modulation deviations. Also, the modulation of one tone relative to the other tone in a stimulus was varied by 0, 45, 90, and 180 deg. Both tones of a stimulus had the same deviation but they could differ in phase of modulators. Results show subjects were attuned to deviation where greater deviations decreased the amount of fusion. However, subject variability showed two other decision strategies occurring; a combination of deviation and phase disparity, and phase disparity alone.
Effects of alterations in auditory feedback on stuttering frequency during fast and normal speech rates
Authors: Kalinowski Joseph , Armson Joy , Stuart Andrew
Published: October 2005

That stuttering is ameliorated under altered auditory feedback conditions (e.g., masking and delayed auditory feedback) has been known for over 40 years. While this effect was initially attributed to auditory factors, more recent explanations have suggested that a change in speech production, specifically slowed speed rate is responsible. The purpose of this study was to determine if stutterers could demonstrate fluency enhancement under various altered auditory feedback conditions at normal and fast speech rates. Using these rates, stutterers read eight 300-syllable passages under nonaltered auditory feedback (NAF), delayed auditory feedback (DAF), frequency-altered feedback (FAF), and a combination of DAF and FAF (DAF+FAF). Results showed that stutterers significantly reduced stuttering under all altered auditory conditions at both speech rates. These results indicate that a slowed speech rate is not necessary to achieve fluency enhancement under altered auditory conditions. Because sensory and motor events are inseparable components within the speech process, it is proposed that reduction in stuttering occurs as a result of alterations to both auditory feedback and speech production. [Work supported by NIH-DC-00201 awarded to Haskins Laboratories.]
Swath acoustic imaging of the seafloor
Authors: de Moustier Christian , Nishimura Clyde
Published: October 2005

Recent developments in bathymetric sidescan sonar systems and in multibeam echosounders have allowed these systems to produce coregistered bathymetry and sidescanned acoustic images of the seafloor in near real time. As a result, in addition to producing geometrically correct images with much less ambiguous information than conventional sidescanned seafloor images, the effects of the local relief and beam patterns on the magnitude of the backscattered signals can be readily compensated to bring out the angular dependence of acoustic backscatter across the swath. By isolating regions of homogeneous tonal appearance in the resulting image, a first-order assessment of the spatial variability in the composition of the bottom can be made. In such areas of the image, where the seafloor is presumably uniform in composition, the angular dependence of acoustic backscatter can be used to infer statistical terrain characteristics such as surface roughness at smaller spatial scales than obtainable with the bathymetry alone. The deterministic approach of shape-from-shading described in a companion presentation by C. Nishimura (same session) can potentially lead to greater bathymetric resolution. Examples are provided with data from multibeam and bathymetric sidescan sonar systems. [Work supported by ONR.]
Acoustic imaging with a bottom-mounted sonar
Authors: Jackson Darrell R.
Published: October 2005

Phase-coherent processing of data from a bottom-mounted, circularly scanning sonar provides a view of the time evolution of the seafloor that is unlike that obtained with conventional sonar. These techniques were developed under the ONR STRESS program, and will be illustrated using data from the STRESS experiment as well as from a later experiment. Ping-ping correlation is used to provide images of cumulative change in the bottom as well as images of current rate of activity. Correlation between echo signals received on the upper and lower halves of the receiving array provides images of fine-scale bathymetry. Time series of all these image types will be presented as false-color movies. Means of extracting quantitative measures from the images will be discussed.
Three-dimensional acoustic tracking of zooplankton
Authors: Jaffe Jules S.
Published: October 2005

As part of a National Science Foundation initiative in Global Ecology (GLOBEC) our group in acoustic imaging in the Marine Physical Laboratory, Scripps Institution of Oceanography, U.C.S.D., has been operating a multibeam acoustic imaging system whose purpose is to track small animals (zooplankton) in the water column in three dimensions. The system has been constructed to operate at a frequency of 420 kHz and consists of a set of side-scan sonarlike transducers. Together, the eight transmitters and eight receivers allow imaging of an 8×8 image. Lateral resolution is 2×2 deg and the range resolution of the system is on the order of centimeters. The system produces frames (3-D images) at a rate of approximately 1 frame per second. To date, the system has been used to image the trajectories of small fish and test targets in a test tank environment. Animated movies, derived from the data have been fabricated which clearly show the animal’s movements. Quantitative analysis of the systems’s performance has confirmed the three-dimensional locations of the animals that are produced from the data.
Speech changes during exacerbation in multiple sclerosis
Authors: Seikel J. Anthony , Madison Charles L. , Drumright David G. , Russell Marilyn , Cooke N. Roger , Brondos Charles E.
Published: October 2005

Multiple sclerosis (MS) is a demyelinating disease with unpredictable course and variable periods of symptom exacerbation and remission. This study identified characteristics of speech in MS that signaled increased disease activity of exacerbation. Speech of eight MS and eight control subjects was recorded at 5-week intervals for a year. Stimuli were CVCs in the carrier ‘‘Say   again.’’ Durations measured included vowel in ‘‘say,’’ initial stop consonant VOT (/p,t,k,b,d,g/), target vowel (/i,a/), and post-vocalic closure preceding final stops (/t,d/). A number of speech segments were longer for MS than controls. Data from sessions were aligned by date of exacerbation of individual MS subjects and analyzed to determine changes in speech occurring before, during, and after exacerbation. Exacerbations revealed striking reductions in duration for vowels, closure durations, and overall sentence duration, and increases in voiceless VOT duration.
Comparison of cubic distortion product otoacoustic emissions generated by the interaction of a spontaneous emission and an external tone and by the interaction of two external tones
Authors: Long Glenis R. , Sun Chuang , Talmadge Carrick L.
Published: October 2005

DPOAEs generated by the interaction of one external tone and one spontaneous otoacoustic emission (SOAE) are maximal when the external stimulus begins to suppress the level of the emission. Consequently, investigations of the f2/f1 and L2/L1 ratios producing maximum distortion are limited. DPOAEs generated in this way were systematically compared to DPOAEs generated by two external tones. First, another external tone with the same frequency as the SOAE was inserted into the ear canal to entrain the spontaneous emission and maintain a known signal at the frequency of the spontaneous emission. Second, DPOAEs generated by two external tones with same frequency and level ranges as above were measured in ears with no spontaneous emissions in the frequency range examined. The pattern of maximum DPOAEs are interpreted in terms of the excitation patterns of external tones and SOAEs on the basilar membrane.
Temporal pitch coding for cochlear implantees: The effects of carrier rate and amplitude modulation of pulsatile electrical stimuli
Authors: McKay Colette M. , McDermott Hugh J. , Clark Graeme M.
Published: October 2005

The pitch evoked by sinusoidally amplitude-modulated current pulse trains on single electrodes was studied. Modulation frequencies of 100, 150, and 200 Hz, together with carrier pulse rates from 200 to 1200 Hz were studied. The results showed that, in general, the pitch of the stimulation was close to but higher than that of a nonmodulated pulse train of rate equal to the modulation frequency. This general rule did not hold, however, whenever the carrier rate was both less than four times and not a multiple of the modulation frequency. Modulation depth was also found to significantly affect the pitch when less than approximately 7% of the current. In this region, the pitch rose uniformly with reduction in modulation depth and became equivalent to that of the carrier rate near the modulation detection threshold. The results of this investigation have relevance to speech processing schemes utilizing pulsatile stimulation, in which modulations in the processor output at the fundamental frequency of speech may provide a voice pitch percept to implantees. [Work supported by NIH.]
Mean flow effects on the vibroacoustic behavior of baffled plates in heavy fluids
Authors: Sgard Franck , Atalla Noureddine
Published: October 2005

The originality of the present paper lies on the development of a formulation accounting for mean flow effects in the vibroacoustic model of a baffled plate. The importance of those effects on the vibrational behavior and stability of a baffled plate with arbitrary boundary conditions, as well as its acoustic radiation pattern, is assessed. The analysis is based on a finite-element method for the calculation of the plate transverse vibrations and the use of the extended Kirchhoff’s integral equation to account for fluid loading with mean flow. A boundary-element method is used to compute the acoustic radiation impedance. The formulation shows explicitly the effects of mean flow in terms of added mass, stiffness, and radiation damping. Furthermore, the added stiffness is shown to be responsible for the instabilities that occur as the flow speed increases. Details of the formulation as well as its numerical implementation are exposed and results showing the effect of the mean flow on the different vibroacoustic indicators (mean square velocity, radiated acoustic power, modal radiation efficiencies) are presented.
The role of acoustic coupling on the radiation from a vibrating source
Authors: Maestrello Lucio , Frendi Abdelkader , Bayliss Alvin
Published: October 2005

The response of an acoustically excited flexible surface together with the resulting sound radiation was considered. A model was employed that accounts for the full coupling between the surrounding fluid and the vibrating surface in three dimensions as well as two dimensions. The model couples the nonlinear Euler equations with an equation describing the nonlinear vibration of the plate. Different regimes of plate vibration and acoustic radiation were described, including linear, nonlinear, quasiperiodic, and apparently chaotic dynamics. It was found that, in the linear regime, the effect of the fluid/structure coupling is not significant. In the nonlinear regime, the effect of the coupling is to significantly reduce the harmonic content in both the plate vibration and the acoustic field. Furthermore, the nonlinear radiation exhibits a relative increase in harmonic content and an overall reduction in level as the acoustic propagation distance increases.
Acoustic radiation of a nonbaffled vibrating plate with arbitrary boundary conditions in light fluids
Authors: Gauthier Carol , Atalla Noureddine , Nicolas Jean
Published: October 2005

A study of the acoustic radiation in light fluids of a nonbaffled vibrating plate with arbitrary boundary conditions is conducted. A new approach using integral formulations combine with polynomial interpolations (Ritz method) is proposed to compute both the vibrations and the acoustic radiation of the plate. The formulation used to compute the acoustic radiated power is expressed in terms of jump of pressure through the plate. Simulations using different boundary conditions have been conducted in both cases, with baffled and with nonbaffled plate. Comparison between both cases reveals the considerable effect of baffles on the modal and nonmodal radiation efficiencies in the lower frequencies. Comparisons are also made between cases with different boundary conditions (clamped–clamped–clamped–clamped, free–free–free–free, and simply supported–SS–SS–SS). Details of the formulations along with their numerical implementations are described and the results showing the effects of a baffle on the acoustic radiation are presented. Finally, the comparisons between the various cases are commented as a conclusion of the study.
Intra-arterial ultrasonic angioplasty: A feasibility study
Authors: Colliou Olivier K. , Everbach E. Carr
Published: October 2005

Current medical technologies for removing the arterial plaque of patients with cardiac disease include balloon angioplasty and laser ablation. In the first, balloons are introduced via catheter into the blocked artery and expanded to allow increased blood flow, but macroscopic plaque pieces can leave arterial walls and enter the circulatory system, causing brain embolism. In laser ablation, an optical fiber is passed into the artery and intense laser light is used to heat the plaque until micron-sized particles are removed. Unfortunately, the ablation is not limited to the plaque, and punctures can occur in the healthy arterial walls once the plaque layer has thinned. A new technology, intra-arterial ultrasonic angioplasty, is being developed in which a wire, acting as an acoustic waveguide, is inserted into the artery and intense ultrasonic waves are used to ablate the plaque at the wire tip. Alternatively, tiny transducers can be inserted into the artery and excited to produce intense ultrasonic waves. Violent cavitation occurring at the plaque surface is believed to be responsible for the ablation, which occurs preferentially in the harder, stiffer plaque rather than in the softer, healthy vessel walls. A series of measurements on several of these acoustic devices and an analysis of the parameters that could be used to optimize their efficacy and safety are presented here.
Recent theoretical and experimental results with AlbunexR, a contrast agent for diagnostic ultrasonography
Authors: Church Charles C. , Levene Harold B. , Keene James M.
Published: October 2005

AlbunexR is an ultrasound contrast agent prepared by sonicating 5% human serum albumin to produce stable, air-filled, albumin-coated microspheres. It is an effective ultrasound contrast agent for use during echocardiography and other ultrasound radiological procedures. Current research is directed toward understanding the physics of the interaction of ultrasound with AlbunexR in tissue. A theoretical model describing the dynamics of these bubbles has been developed by assuming a solid elastic shell. The shell (1) supports a strain that counters the effect of surface tension and thus stabilizes the bubble against dissolution; (2) increases the stiffness of the bubble and thus raises the resonance frequency of the bubble significantly; (3) increases the effective damping of the bubble and thus reduces the scattering cross section of the bubble markedly. Experimental measurements of speed of sound, attenuation coefficient, and backscatter coefficient have been made as functions of acoustic frequency and gas volume fraction. Comparisons between these measurements and theoretical predictions will be presented.
Ontogeny of 2f1-f2 acoustic and cochlear microphonic distortion products
Authors: Zhang Ming , Abbas Paul J.
Published: October 2005

The development of the acoustic distortion product (ADP) and cochlear microphonic distortion product (CMDP) 2f1-f2 was studied in pigmented rats, beginning 10 days after birth (p10). Both the ADP and CMDP were measured as a function of stimulus frequency (1.04 to 10.24 kHz with an f2/f1 ratio of 1.25) and level (20 to 80 dB SPL). The onset of the ADP occurred first at f2=5.12 kHz (p11–13), then at higher and lower frequencies. The amplitude of the ADP also matured first at f2=5.12 kHz (p17–18). This result is similar to the earlier work [S. J. Norton etal., Hear. Res. 51, 73–92 (1991); C. M. Henley etal., Hear. Res. 43, 141–148 (1989); M. Lenoir and J.-L. Puel, Hear Res. 29, 265–271 (1987)]. The onset and maturation of the DMDP was similar to ADP’s, except at lower frequencies where the CMDP developed somewhat earlier. There is a strong correlation in amplitudes of the ADPs and CMDPs across ages, consistent with the hypothesis that the ADP and CM DP may be linked to the same process [D. T. Kemp and A. M. Brown, Hear. Res. 13, 39–46 (1984)].
Dual SAW sensor for the measurement of skin friction on structures exposed to turbulent fluid flow
Authors: Bao Xiao Qi , Varadan Vasundara V. , Varadan Vijay K. , Pauley Wayne
Published: October 2005

A dual SAW sensor attached in cantilever fashion to a free-floating membrane flush mounted on a structure exposed to turbulent fluid flow are described. Shear stress on the membrane due to the flow conditions, deforms and bends the cantilever beam. The SAW devices are mounted such that one device is in compression and the other in tension. The cantilever arrangement magnifies the deformation of the SAW sensors by many orders of magnitude relative to the membrane. The SAW devices are attached to oscillator circuits and the change in frequency of the SAW oscillators due to the deformation can be accurately measured. The dual arrangement compensates changes in temperatures, electrical, and mechanical noise and other changes and the difference in frequency measured by a mixer is directly related to the shear stress on the structure. Experiments conducted in a wind tunnel are described. [Work supported by ONR.]
Shear acoustic properties of soft biological tissues in medical diagnostics
Authors: Sarvazyan Armen
Published: October 2005

This report is a summary of the studies of shear acoustic properties of soft biological tissues performed by the author and his co-workers in the period from 1966 to the present. A number of techniques for measuring shear elastic moduli of soft tissue in a range of frequencies are described. Methods are considered based on the measurements of acoustic impedance, the shear and surface wave speeds, as well as of static moduli. Results of invitro studies of animal and human tissues and of such model systems as various gels and rubbers are presented. Invivo studies were made on superficial tissues such as the skin and the nearest underlying tissues. It has been shown that surface acoustic waves can be successfully used in the diagnosis of various dermatitis and skin cancer as well as for monitoring of the efficacy of treatment. In response to the needs of the newly developing technique of ultrasonic elasticity imaging of the breast, systematic studies involving 162 excised samples of glandular, fatty, cancerous, and fibroadenoma tissues were performed and the ranges of variation of shear moduli were evaluated. a)Permanent address: Inst. of Theoret. and Exp. Biophys., Russian Acad. Sci., Pushchino 142292, Russia.
ECoS: The experiment control system
Authors: Mandarino Cathy , Bangarth Peter , Ramji Ketan , Jamieson Donald G.
Published: October 2005

The experiment control system is a package of computer programs that facilitate the generation and conduct of identification and discrimination experiments using speech and other complex acoustical signals. The system permits microcomputers to be used to control experimental equipment, present signals to listeners, and record and analyze responses, without preparing individual computer programs for each experiment. The package contains three general programs. The GENERATE program is used to define experimental parameters via full-screen data entry forms. The core of the program is an entry form that allows one to specify four basic parts of an experimental trial: a warning signal, one or more stimulus presentations, the response(s) to be recorded, and any feedback to be provided after the response. Within each of these categories, a number of alternatives are permitted. The CONTROL program applies the parameters and data defined in GENERATE to run the experimental session. Typically, possible responses are displayed using high-resolution graphics on a computer video screen and subjects respond using a computer mouse. The SCORE program analyzes output from CONTROL and displays the results as response matrices with basic statistics such as means and standard deviations, as well as row and column sums. Output is provided as a screen display and print-ready file. ECoS is being made available to researchers as part of Version 4.0 of CSRE (the Canadian Speech Research Environment).
Radiative transfer of ultrasound
Authors: Turner Joseph A. , Weaver Richard L.
Published: October 2005

Multiple scattering of ultrasound in an elastic medium containing discrete random scatterers is modeled using radiative transfer theory. The uncorrelated phases of the scattered field allow one to write an energy balance equation for the spatially incoherent intensity. This ultrasonic radiative transfer equation contains single-scattering and propagation parameters that are calculated using the elastic wave equation. Polarization effects are included through the introduction of an elastodynamic Stokes vector, which contains a longitudinal Stokes parameter and four shear Stokes parameters similar to the four Stokes parameters used in optical radiative transfer theory. The theory is applied to a statistically homogeneous, isotropic elastic half-space containing randomly distributed voids illuminated by a harmonic plane wave. Results on the angular dependence of backscattered intensity are presented. It is anticipated that this approach may be applicable to materials characterization through the study of the time, space, ultrasonic frequency, and angular dependence of multiply scattered ultrasound in elastic media with microstructure. [Work supported by NSF Grant No. MSS-91-14360.]
The French horn versus the concert hall
Authors: Caswell Daryl
Published: October 2005

The acoustical problems presented by the French horn in concert halls and recording studios are a constant source of frustration for the acoustician. The unique performance practices employed by the horn player (hand in the bell, pointing the bell to the back of the hall) create confusing and seemingly contradictory acoustical demands. In addition, the nonscientific language of the performer tends to force the acoustician to disregard the very real concerns and knowledge of the musicians. For example, horn players want a diffuse and ‘‘mellow’’ sound but insist on acoustical conditions that allow clear and precise ensemble playing. This paper will describe a solution to the chronic problems experienced by the French horn section of the Calgary Philharmonic Orchestra in the new Jack Singer Concert Hall. This solution was possible because the researcher (a professional horn player and mechanical engineer) was able to translate the concerns of the horn players into scientifically acceptable terms and use this information to direct the project.
Auditory grouping in lateralization, pitch, and vowel perception: A comparison of the effects of onset asynchrony and of mistuning
Authors: Darwin C. J. , Hill Nicholas I.
Published: October 2005

This paper reviews the effect of two powerful cues to sound segregation, onset asynchrony and mistuning, in a number of different experimental paradigms. Although both cues substantially influence grouping in all three paradigms, there are quantitative differences across the paradigms. An onset asynchrony of a few tens of milliseconds is sufficient to allow listeners to hear out a single low-numbered harmonic from a complex and for it to be lateralized largely independently of the other harmonics. It is also enough to remove that harmonic from the calculation of vowel quality. But a substantially greater asynchrony (over 100 ms) is needed in order to remove a single (mistuned) harmonic from a complex for the purpose of calculating its pitch. When a single low-numbered harmonic is mistuned, a mistuning of less than 1% is generally sufficient to allow it to be heard out. At about 3% mistuning, the mistuned harmonic can be lateralized largely independently of the other harmonics, but will still make a full contribution to the pitch and the vowel quality of the complex. A substantially reduced contribution both to the vowel quality and to the pitch of the complex requires a larger mistuning—around 8%. [Work supported by UK SERC & MRC.]
Implicit assumptions in modeling higher level auditory processes
Authors: Pastore Richard E.
Published: October 2005

There has been growing interest in the investigation of auditory stimulus processing at levels considered to be clearly beyond or above the limits imposed by the peripheral auditory system. Efforts to investigate such higher levels of processing of complex stimuli are nearly always based upon assumptions about perceptual and decision processes that limit the range of reasonably valid conclusions. Such assumptions are usually implicit and often not immediately recognized. To illustrate the critical role played by such implicit underlying assumptions, existing and new research on the perception of formant transitions in speech will be examined in terms of basic assumptions whose recognition can modify (and sometimes strengthen) conclusions about higher levels of perceptual processing. Discussion will focus on the implications of fundamental assumptions for the identification and demonstration of important principles of perceptual organizing (e.g., Gestalt, feature integration) and for testing hypotheses about alternative perceptual models, modes, or modules. [Research supported in part by NSF and AFOSR.]
Comparison of modern room acoustic measurements in auditoria: An overview of variables, data analysis, and objective criteria
Authors: Hyde Jerald R.
Published: October 2005

Over the last two decades, a set of ‘‘modern’’ room acoustic measures has been developed which utilizes the creation of an impulse response at various positions within a room. The idea has been to create a set of information for that space which facilitates correlation with subjective evaluation. Objective measures such as energy ratios, lateral energy fraction, and source strength have been reported frequently in the literature over the past decade, stimulating a concerted effort to standardize the methodology of both the measurements and the data analysis. The goal is to understand the effects of an almost endless set of variables on the data so that one will know which sets of information from different halls and measurement systems can be reasonably compared. This paper will report the results of different measurement systems data in the same auditorium as well as the difference in acoustical properties between the empty and occupied condition for the same space. An approach to how sets of data might be averaged will be explored along with a methodology for predicting full occupancy objective values from ‘‘empty’’ room data. Finally, a range of objective criteria for concert halls will be suggested.
Analysis of acoustic resonances in partial-wave space, and the nonresonant background
Authors: Überall H. , Werby Michael F.
Published: October 2005

The basic principle of the resonance scattering theory, or RST [Flax etal., J. Acoust. Soc. Am. 63, 723 (1978)] consists in separating the scattering amplitude for elastic objects into two parts: a nonresonant background (assumed that of rigid-body scattering for solid-metal and thick-shell objects, as shown above and earlier by Junger), and a series of resonance amplitudes that can be represented as in the Breit–Wigner nuclear scattering theory (cf. reference above). It is shown that this way of subdividing the scattering amplitude into two parts follows naturally from Hilbert–Schmidt theory. For not-so-thick shells, the correct background was given by Werby [original derivation published in AcousticResonanceScattering, edited by H. Überall (Gordon and Breach, New York, 1992)]. Subtraction of the appropriate background in partial wave space can be facilitated by representing the modal amplitudes (and resonances) as a function of frequency, or as done in a more recently introduced approach [Talmant etal., J. Acoust. Soc. Am. 86, 278 (1989)], by representing the total amplitude as a function of mode number. This furnishes an unambiguous classification scheme for all orders of resonances, and allows one to isolate fluid-borne waves as recently identified by Talmant etal.
The effect of periodically attached substructures on the excitation of submerged cylindrical shells
Authors: Choi S.-H. , Achenbach J. D. , Igusa T.
Published: October 2005

The presence of substructures in a cylindrical shell gives rise to dynamic interactions that influence the axial distribution of vibration along the shell. In this paper, Lagrange’s equations are used to develop the equations governing the forced harmonic vibration of a submerged cylindrical shell with periodically attached internal substructures that is subjected to periodically placed loads. Modal expansions are used to describe the response of the shell and the fields in the fluid. First a shell without substructures but subjected to periodically placed ring loads is considered. The method of this paper is found to be nearly as accurate as a traveling-wave-based method for an infinite shell subjected to a single ring load. Two types of substructures are examined: circular panels with hinge connections and circular ribs with rigid connections. It is shown that the substructures confine the flexural motion to a region near the location of the applied forces. The localization effect decreases when the forcing frequency is close to the substrate’s natural frequencies, and becomes more pronounced when within a periodic segment the ribs have a varying impedance. [Work supported by ONR.]
Band-edge localization and spatial textures of surface acoustic waves in weakly disordered 1-D superlattices
Authors: Desideri Jean-Pierre , Sornette Didier
Published: October 2005

The extreme sensitivity of wave propagation on the presence of disorder near remnant geometric Bragg resonance (band edges) is exhibited experimentally for the first time using surface acoustic waves on very weakly corrugated solids. Anderson localization is identified by measuring the spatial structure of proper modes with an optical diffraction experiment and is found to occur most strongly precisely at the two borders of a remnant stop band. Exponentially decaying localized modes are decorated by a speckle-like wave pattern, which constitutes an observable fingerprint of the random system. The amplitude of this spatial wave structure is found to exhibit a marked maximum at band edges thus providing a novel signature of localization, which used to probe localization in the interior of the remnant stop bands.
Inversion and control of an articulatory model of the vocal tract: Recovering articulatory gestures from sounds
Authors: Laboissiere Rafael
Published: October 2005

To what extent are the basic concepts of robotics and control theory useful for the understanding of speech communication processes? In this paper, this question is addressed and a quantitative modeling framework is proposed, which has some bearings on classical concepts of feedforward and feedback control systems. The main feature of the model is the capability to solve the ill-posed inversion problem of determining the articulatory commands from speech goals specifications, whatever they are. A theoretical analysis shows that former models for motor control, namely the task-dynamics approach [Saltzman and Munhall (1989), Ecolog. Psychol. 1(4)] and the forward-inverse modeling [Jordan and Rumelhart (1992), Cognitive Sci.], are subcases of the present model. Simulations of well-known phenomena in speech, like compensation for bite-block perturbation and coarticulation of simple VCV sequences, can be successfully done in this framework. This modeling effort can feed the theoretical debate about invariance/variability in speech because it is a natural framework to address the following issues: (1) the nature of the control space used in programming speech gestures; (2) the suitable principles of control, defined as the choice of an architecture for the control and the constraints imposed on the control law to solve the inversion problem; and (3) the learning of an inverse model capable of generating suitable articulatory commands from a specification of the goals to be reached.
Effects of speaking rate and stress on vowel durations and formant structures
Authors: Stack Janet W.
Published: October 2005

The effects of speaking rate and stress on the temporal and spectral quality of vowels in four adult male speakers were evaluated. Conversational style speech was used from which four vowels in two target words were analyzed. Target words were produced in two different sentence stress conditions. Vowel durations were measured, and formant values were obtained at the one-fourth, one-half, and three-fourths points of the syllables. Rapid rate tokens were consistently shorter in duration than normal rate. There was no differential duration shortening between stressed and unstressed words or vowels. Speakers were very consistent in their overall sentence compression, but word and vowel compressions showed nonsystematic individual differences. Target undershoot (any deviation greater than 1 Bark from the stressed normal rate condition) was found in only one speaker, for the first formant of one vowel. Formant movement from the one-fourth to the three-fourths point was not affected by rate or stress (determined as any change of more than 0.1 log unit from the stressed normal rate condition) in any speaker. [Work supported by NIDCD.]
Articulatory and intonational correlates of French focus
Authors: Ayers Gayle M.
Published: October 2005

Jaw movement and F0 patterns are investigated in a French corpus of neutral utterances and utterances with focus on the initial, medial, or final word. Initial-word length also varied between two or three syllables, and both natural and reiterant copies were produced. The maxima and minima of jaw displacement (jaw closure and opening), peak velocities, and F0 peaks of the target words were measured. Jaw velocity and displacement were correlated identically in neutral and focus utterances. Displacement alone accounted for between 69% (disyllables) and 80% (trisyllables) of the velocity variation. Focused words tended to have a larger displacement on the first syllable. The observed variation in duration could not be accounted for by a displacement-independent variation in peak velocity. In neutral utterances F0 peaks occurred during the last closing gesture of each nonfinal phrase, a pattern that can be represented phonologically by a demarcative phrase-final H tone. In focused utterances, by contrast, F0 peaks occurred during the first closing gesture of the focused word, although there was sometimes also a peak during some later gesture, as in the neutral utterances. The focus H tone is perhaps an accent tone of the English type. A possible correlation between jaw kinematics and the F0 pattern is being investigated.