bluuebunny/crossref_metadata_2025 huggingface dataset:
The mechanical and thermal effects of focused ultrasound in a model biological material
Authors: Feng Feng , Mal Ajit , Kabo Michael , Wang Jeffrey C. , Bar-Cohen Yoseph
Published: January 2006

This paper is motivated by possible medical applications of focused ultrasound in the minimally invasive treatment of a variety of musculoskeletal disorders that are responsive to thermal treatment. A model-based analysis of the interaction of high-intensity focused ultrasound with biological materials is carried out in an effort to predict the path of the sound waves and the temperature field in the focal region. A finite-element-based general purpose code called PZFlex is used to determine the effects of nonlinearity and geometrical complexity of biological structures. It was found that at frequencies of interest in therapeutic applications, the nonlinear effects are usually negligible and the geometrical complexities can be handled through a substructuring procedure. An approximate analytical method with acceptable accuracy is developed as an alternative to the purely numerical approach used in PZFlex. The mechanical and thermal effects in two-layered fluid material systems induced by high-frequency focused ultrasound are calculated through this analytical method. The results are compared with those obtained using PZFlex as a benchmark.
A novel underwater acoustic transmitter
Authors: Chang Chung , Coates Richard
Published: January 2006

A strong wide bandwidth low-frequency acoustic transmitter was designed and built to operate in the high-pressure environment of 20 000 psi and temperature over 200°C inside an oil well. The same design idea can be easily adapted to the naval application in order to use it in the deep ocean environment. This transmitter is pressure balanced and does not use conventional piezoelectric material. Therefore, there is no performance degradation with changing pressure and temperature. This new transmitter uses impact force onto an acoustic resonator to generate sound. The impact force is generated by an electrical hammer. The design is simple, robust and the radiated acoustic wave fields are as repeatable as the piezoelectric source. In addition this new transmitter does not require an expensive amplifier to operate. A video clip will be shown to demonstrate the strength of the source. Further research was done to understand the impact physics and its controlling parameters. Using signal deconvolution technique one can measure the impact force function. A peak impact force of a few thousand pounds by the hammer was measured.
Active hearing protectors: Prospects for improving speech intelligibility while maintaining noise reduction and audibility of warning alarms
Authors: Brammer Anthony J. , Peterson Donald R. , Cherniack Martin G. , Gullapalli Subhash
Published: January 2006

Users of hearing protection devices (HPDs), including the communication headsets and helmets commonly worn by aircraft air and ground crews, emergency responders, military personnel, and persons in industry working in hostile environments, have long complained that HPDs interfere with their ability to communicate and to hear warning alarms. There thus appears to be a need for additional specialized HPDs designed specifically for these situations. The technology of active noise control together with signal processing applied to the communication channel of the HPD may provide a potential solution. The combination could improve noise reduction at low frequencies and enhance the intelligibility of speech reproduced by the communication channel, while maintaining the overall noise reduction within occupational exposure requirements, and assisting the perception of external warning alarms. A strategy for achieving these goals using an active circumaural earmuff equipped with sub-band processing will be described, in which parallel controllers optimize the speech signal-to-noise ratio in bands that contribute most to intelligibility. The perception of a tonal alarm is assisted by binaural feed through to the earphones, within the constraints imposed by occupational exposure limits, and by sub-band processing to reduce the upward spread of masking.
Response of an edge-supported, annular, electret earphone
Authors: Busch-Vishniac Ilene J.
Published: January 2006

In many electret transducers, the diaphragm is held above a metalized backplate by circular ridges machined into the backplate. Such transducers may be thought of as a series of annular electret transducer segments, each of which has an edge-supported diaphragm. In the treatment presented here the behavior of an edge-supported, annular, electret earphone is studied analytically in a two-step procedure. First, the static diaphragm deflection is determined. A stability criterion is developed which physically corresponds to a limit in the maximum stable static deflection. Second, the diaphragm dynamic motion is determined and the resulting sound pressure in the ear canal calculated. Using this method the linear response and distortion response may be separately analyzed. Both tend to increase in level as the transducer approaches the point of static instability. Experimental results agree well with the predictions of the theory. [Work done in part at Bell Laboratories, Murray Hill, NJ 07974.]
Characteristics of a particle velocity hydrophone based on hot-film anemometry
Authors: Dubbelday Pieter S.
Published: January 2006

It is desirable to measure particle velocity in an acoustic field in addition to pressure. The heat transfer inherent in hot-film anemometry is mostly a function of particle motion. The relation between particle velocity and voltage output in a harmonic hydroacoustic field appears different from that in a nonperiodic flow (King's law). For horizontal motion, the output is proportional to the velocity squared, with a frequency twice that of the acoustic field. If the motion is vertical, it modulates the steady free-convection flow off the film, and a linear relation ensues with the same frequency as the field. Experimental results were obtained by means of a horizontally driven open trough for the first case and a vertical inertial calibrator for the second. It was attempted to correlate the output, expressed as a Nusselt number amplitude, to the relevant dimensionless numbers: particle displacement relative to sensor diameter, Stokes, Fourier, and Grashof numbers. Preliminary experiments show that an imposed bias flow improves the sensitivity and directional response of the sensor [Work supported by Office of Naval Research.]
Four accelerometer structural vibration intensity measurements on beams
Authors: Carroll G. P. , Clark J. A.
Published: January 2006

Two accelerometer measurement methods do not accurately measure structural vibration intensity near boundaries for the lowest beam modes because the shear and moment-related intensity components are no longer equal. It was shown by the authors [J. Acoust. Soc. Am. Suppl. I 73, S33 (1983)] that this is a serious limitation since it is often by the lowest modes that power is transmitted through complex structures. In this talk, a four accelerometer spectral averaging measurement approach originally proposed by Verheij [J. Sound Vib. 70, 133–138 0980)] will be reviewed. A method for conveniently implementing this approach with currently available two-channel FFT signal processors will be described and results from an experimental study of a beam excited transversely at one end and damped at the other end will be presented. The experimental results will also be compared with theoretical solutions and with results obtained independently by holographic interferometry. [Research supported by David Taylor Naval Ship Research and Development Center, Washington, DC.]
The internal structure of vowel categories in infancy: Effects of stimulus “goodness.”
Authors: Grieser DiAnne L. , Kuhl Patricia K.
Published: January 2006

We investigated whether perceived differences in stimulus goodness, that is, the degree to which a stimulus within a phoneme category is considered to be a “good instance” of the category, predicted differential responses to these stimuli by young infants. Two points were chosen in an F1/F2 coordinate vowel space: one judged to be a “good” representative of the /i/ vowel category, the other a “poor” representative, based on adult judgments. Then, variants were synthesized by manipulating the first two formants in both distance and direction from these two points. The resulting stimuli formed rings around the “good” /i/ and the “poor” /i/. Thirty-two 6-month-old infants were tested in a generalization task using a visually reinforced head-turn procedure. Half of the infants were tested using the “good” /i/ and its variants, and half using the “poor” /i/ and its variants. Results showed that generalization around the “good” /i/ was significantly greater than around the “poor” /i/. Moreover, infant response patterns correlated with adult subjective “goodness” judgments.
Characteristics of reduplicated babbling in 6–8-month old infants
Authors: Stark Rachel E. , Bond Jennifer
Published: January 2006

Reduplicated babbling has been defined as sequences of identical or nearly identical consonant-vowel syllables. This type of vocalization appears quite suddenly in the premeaningful utterances of infants at 6–9 months of age. In the present study, reduplicated babbling was examined at the time of its onset in four infants of 6–8 months. Computer-assisted spectrographic analysis was carried out and amplitude and pitch contours were obtained. Measurements were made of syllable and sequence duration. A specially designed transcription system was also employed in data analysis. It was found that: (1) the timing patterns in reduplicated babbling differed in specific ways from those of earlier vocalizations; (2) that a variety of vocants (vowel-like) sounds were produced within a babbled sequence; (3) that manner of articulation of consonantal (closant) sounds varied but place of articulation did not within a babbled sequence. The implications of these findings for development of speech motor skills will be discussed. [Work supported by NICHD.]
Development of vowel articulation in children
Authors: Bickley Corine
Published: January 2006

The development of children's ability to produce high versus low vowels and front versus back vowels was examined in a longitudinal study. Acoustic measurements were made of the vowels in spontaneously produced words with known referents. Vowels were grouped by target vowel into high, front (/i/, /ı/), high back (/u/, /U/), and low (/ɑ/, /ɔ/). Evidence for control of vowel height was measured in terms of first formant frequency (F1) change over time. Vowel backing was measured by changes in second formant frequency (F2). Average F1 and F2 values and standard deviations of F1 and F2 were detertmined from harmonic amplitudes in narrow-band discrete Fourier transforms and from local maxima in LPC spectra. Over periods of 5 months, the average F1 for high vowels decreased while the average F1 for low vowels increased. Also, standard deviations for each vowel group decreased with age. Control of backing was seen primarily in increasing average F2 for front vowels. Standard deviations of F2 for both front and back vowels decreased with age. [Work supported by grants from the U. S. Department of Education and from NINCDS.]
On improving articulation index predictions of speech sound identification performance by the hearing impaired
Authors: Pavlovic Chaslav V. , Studebaker Gerald A.
Published: January 2006

Predictions of speech sound identification performance by hearing impaired individuals were made using an articulation index (AI). The AI scheme used was one that had earlier been found accurate for normal hearing listeners. It was expected that some sensorineural hearing impaired individuals would exhibit reduced suprathreshold speech processing capacity, and that therefore, the AI procedure would need to be modified to accomodate those effects. To this end we measured several psychoacoustical variables (critical bands, upward spread of masking, temporal masking, tuning curves, etc.) that might be incorporated into the AI formulas to account for the degraded performance. Results for each of the individuals tested will be discussed. [Work supported by NINCDS.]
Principal component amplitude compression
Authors: Bustamante Diane K. , Braida Louis D.
Published: January 2006

Multiband amplitude compression systems which process each frequency band independently of the others have yet to prove advantageous for sensorineural hearing impaired listeners over good linear amplification systems. Although audibility is improved, certain speech cues are consistently degraded by multiband compression. Acoustic analysis indicates that multiband systems whiten the short-term speech spectrum, reducing the spectral detail. Analysis of speech reception errors suggests that this degrades speech intelligibility. Spectral detail can be preserved by utilizing the correlation of speech levels in different frequency bands. Rather than treating each band independently, the compression in each channel is a function of the levels in all the channels. One implementation of such a system is based on a principal component analysis of short-term speech spectra. Compression of the first component, which corresponds roughly to overall level, equalizes the energy in consonants and vowels much as does a wideband compressor. Compression of the second component, which corresponds roughly to spectral tilt, acts as a variable frequency gain characteristic. The principal component system implementation and measurements of the properties of processed speech materials will be presented.
Second-language speech tests in a deaf patient with cochlear implant
Authors: Müller Carl G. , Kemppel Cornelia M.
Published: January 2006

Some reports of speech understanding through cochlear implants have been difficult to evaluate because test material in a foreign language was not comparable to the widely used and highly standardized speech material in English. Thus the data and their implications have not been widely accepted. To overcome this, we have provided patient “CK” from the Viennese Implant Project with extensive English language training in vocabulary, grammar, and composition with the goals of evaluating her process of second-language acquisition and of corroborating the significant Viennese results by using standardized English language tests. Tape-recorded material was presented solely through electrical connection to the speech processing electronics supplied by the Hochmair group (Vienna), thereby ruling out possible acoustical input. Stimulation was delivered to a single channel electrode through amplitude limiting, frequency shaping, and high-frequency pre-emphasis circuitry. We report on results obtained from selected portions of the Minimal Auditory Capabilities (MAC) Test (including CID Everyday Sentences), the Diagnostic Rhyme Test, the California Consonant Test, and other less difficult tests designed to reduce the role of specific language features. Results support those of the Hochmairs on the efficacy of single channel implant systems for speech understanding. [Research supported in part by a Biomedical Research Support Grant (NIMH).]
A prototype hearing aid for acoustic coupling of telephone and hearing aids
Authors: Stoker Richard G. , French-St. George Marilyn , Brown Jonathan
Published: January 2006

Recent trends in the telecommunications industry have resulted in an increased number of telephone receivers which are not compatible with the induction coils contained in many hearing aids. This situation has developed in spite of efforts by the Federal Government to legislate telephone/hearing aid compatibility. This project was designed to evaluate a prototype heating aid with specialized frequency shaping capability. In short, we wished to discover if current technologies were capable of creating a hearing aid which could be effectively used by hearing aid wearers to understand speech transmitted over a telephone without the use of magnetic coupling. Ten subjects from three different hearing loss categories: precipitous high-frequency loss, sloping high-frequency loss, and relatively flat, severe loss, were tested. Subjects were evaluated using three types of frequency shaping: “typical hearing aid response,” low-frequency compensation, and flat gain condition (up to 40 dB of linear amplification beyond that normally required for free-field communication). Subjects were required to respond to recordings of the NU-6 WORD LIST presented in quiet and with 45 dB and 55 dB SPL of competing background noise (multitalking noise). The results of this study suggest that certain classes of hearing impairment may benefit from specialized circuitry which provides frequency shaping to the telephone signals received at the hearing aid microphone. This technique has also been shown to even be effective in moderate amounts of background noise, allowing speculation that acoustic coupling of hearing aids and telephones may be more realistic than commonly thought.
Vowel production in aphasia
Authors: Ryalls John H.
Published: January 2006

A group of five anterior and seven posterior aphasic patients were recorded for their vowel productions of the nine nondipthongized vowels of American English [Peterson and Barney, J. Acoust. Soc. Am. 24, 175–184 (1952)], and compared to the productions of a group of seven normal speakers. All phonemic substitutions were eliminated from the data base. A linear predictive coding program was used to extract the first and second formant frequencies for each of the five repetitions of the nine vowels. The vowel duration and the fundamental frequency of phonation were also measured. Statistical analyses revealed that the duration and the fundamental frequency for the aphasics were significantly different from the normal subjects. Although there were no significant differences in the formant frequency means, there were significantly larger standard deviations for the aphasic group. This greater variability was considered as evidence of a phonetic deficit on the part of the aphasic speakers, in the context of preserved phonemic organization. [Work supported by ADAMHA.]
Disk brake noise in rail transit vehicles
Authors: Faulkner Lynn L. , Rodman Charles W.
Published: January 2006

A critical parameter in the mechanism of disk brake squeal is the manner in which the coefficient of friction changes as a function of the instantaneous relative velocity between the friction material and the brake rotor. Substitution of alternative materials for asbestos as a friction material constituent has produced squeal in some brake designs but not in others, leading to the conclusion that one or more parameters not associated with friction material characteristics operates to control the squeal mechanism. The probable nature of these parameters is reviewed along with a description of experimental work carried out to investigate the cause of squeal. [Work Supported by US-DOT-TSC and Washington Metropolitan Area Transit Authority (WMATA).]
Vibration damping to control railroad wheel squeal
Authors: Kirschner Francis
Published: January 2006

The squeal noise radiated by rapid transit wheels on sharp turns is an important instance of friction generated noise. It is caused by the lateral slip-stick frictional force between the wheel and railhead. Noise control methods such as rail lubrication, hard faced rails, tuned wheel dampers, and resilient wheels have not been entirely satisfactory from the standpoint of either cost effectiveness or of safety. This paper will focus on several lightweight vibration damping treatments which have been economical and effective means of reducing squeal noise. Several ring and constrained layer damping treatments which make use of efficient viscoelastic damping materials have resulted from extensive development and laboratory testing programs. Treatments ranged from 1% to 2% of the total weight of wheels weighing 450–800 lb. Wayside noise reductions of 34 dB have been measured in recent field tests on rapid transit systems. These measurements have shown excellent correlation with vibration spectra measured in the laboratory and confirm the effectiveness of vibration damping in controlling friction generated noise of this type.
Variational method for prediction of acoustic radiation from vibrating bodies
Authors: Pierce Allan D. , Wu Xiao-Feng
Published: January 2006

Integral equation formulations such as discussed by Chertock, Copley, Schenck, Meyer, Bell, Zinn, Stallybrass, and many others, typically have nonsymmetric kernels and are not easily rephrased as a variational principle. However, a symmetric kernel does result from the normal derivative of the Kirchhoff-Helmholtz integral, with the exterior point subsequently allowed to approach the surface, but the integrand then has unmanageable singularities. A method due to Maue and Stallybrass allows this integral equation to be recast into a usable form (involving tangential derivatives of the unknown surface pressure) and this version in turn leads to a variational principle that has considerable promise for systematic approximate solutions of radiation problems in the low to moderate ka regimes. Validity of this formulation is substantiated by derivation of known results for vibrating spheres and disks. Numerical results for other geometries are expected to yield higher accuracy than previously because one can incorporate one's best “physical insight” in initial choices for the class of trial functions for surface pressure. If computations now in progress are completed, the example of an oscillating airfoil will be discussed, with some expected clarification of the anomalous results of the Brooks' experiment.
Acoustic scattering from absorbent wedges
Authors: Marsan Mehmet , Hayek Sabih I.
Published: January 2006

The prediction of the sound scattered by impedance covered wedges is obtained by use of dual integral equations. The impedance of each face of the wedge is modeled as a point reacting complex quantity which is independent of the other face. The solution was constructed as an angular spectrum to satisfy the boundary conditions and Sommerfeld radiation condition. The solution kernel was obtained exactly and is in terms of circular functions. The solution of the scattered pressure was then obtained for farfield and mid-range by use of asymptotic techniques. This solution is much simpler than the one developed by Russian scientists [for example, see G. D. Malyuzhinets, “The Radiation of Sound by Vibrating Boundaries of an Arbitrary Wedge, Parts 1 and 2,” Sov. Phys. Acoust. 1, 152–174, 240–248 (1955)] which was obtained by a method similar to Wiener-Hopf techniques. Thus it is easier to use highway noise applications because of its simplicity. The solution for the diffracted pressure exhibits clearly the role of the incident and reflected shadow boundaries and shows there is one minimum in the scattered field which depends on the two surface impedances. For backscattered pressure, the solution exhibits two minima. In all cases, the scattered pressure becomes negligible near the wedge surfaces. [Work supported by NAVSEA.]
A new approach to resonance scattering in acoustics and elasticity
Authors: Norris A. N. , Kriegsmann G. A. , Reiss E. L.
Published: January 2006

A new method is described for determining the scattered field from an obstacle in the resonant frequency regime. The method is based on the assumption that the density of the obstacle is either much greater or much less than the density of the surrounding acoustic fluid. When the frequency of the incident wave is not close to a resonance frequency of the obstacle in vacuo the reaction of the fluid on the obstacle is small. However, this reaction is important near a resonance frequency. We use the method of matched asymptotic expansions to obtain a uniform approximation for the scattered field, valid at all frequencies. It is shown that the resonant peak bandwidth is related to the radiation cross section, for simple modes. Multiple modes are also considered. The method is illustrated by examples.
Excitation of anomalous resonances for acoustical scattering from fluid loaded solid elastic spheroids
Authors: Werby M. F. , Hackman Roger H.
Published: January 2006

Conventional theories of scattering from fluid-loaded elastic solids indicate that there is a threshold in KA (K is the wavenumber and A some characteristic dimension of the object) below which one cannot excite Rayleigh resonances and for which the scattering behavior is essentially rigid. However, a systematic investigation of acoustical scattering from elastic solid spheroids reveals that anomalous behavior occurs for scattering in an angular region off the axis of symmetry. It was found that this behavior is more pronounced for higher aspect ratio objects and that the anomalous form functions shift down in KA with increasing aspect ratio. Further investigation revealed that this behavior actually corresponded to the excitation of surface disturbances corresponding to standing waves following a spheroidal path. We thus refer to them as spheroidal resonances, which are similar in nature to Rayleigh type resonances. Such resonances can only occur for elongated objects above a certain aspect ratio and are most strongly excited at specific angles. These results will be presented.
Rigid scattering from fluid-loaded objects for high aspect ratios
Authors: Werby M. F.
Published: January 2006

We perform a systematic study of acoustical scattering from rigid fluid-loaded spheroids with aspect ratios ranging from 10 to 30 using the coupled high-order T-matrix formulation developed for high-aspect ratio problems. The kl /2 range will be from 6 to 50, where k is the wavenumber and l is the length of the spheroid. Until recently it has not been possible to explore this region of interest. Of particular interest is the monostatic angular distributions. In this region there is a proliferation of nulls due to the variation of paths from different points of the scatterer to the point of detection. The origin of the first and subsequent nulls can be related to the aspect ratio of the object by an expression derived from classical wave arguments. Results will be presented.
The isolation of physical mechanisms associated with acoustical scattering from submerged elastic spheroidal and spherical shells
Authors: Werby M. F. , Hackman Roger H.
Published: January 2006

Acoustical scattering from submerged spheroidal and spherical elastic shells exhibits varied behavior over a broad range of KA (K is the wavenumber and A the largest dimension of the object). This behavior is complicated due to reflections from the inner surface (except for very thin shells) resulting in a very pronounced interference phenomenon between the internal and specular reflections as well as effects from the resonances, A general theory based on elastodynamics that accounts for all these mechanisms is perforce very difficult to employ computationally. In addition, some KA regions do not include all the mechanisms and thus a more simplified theory could be used. Thus, if one can develop a procedure that can account for the individual mechanisms separately considerable progress will be made in solving the overall problem. We propose to develop a theory based on an ordering procedure that will allow one to isolate the various effects. Several assumptions and schemes will be examined and compared to solutions of the exact problem.
Sound scattering and radiation from a thin rod in a viscous medium
Authors: Lin Wen H. , Raptis A. C.
Published: January 2006

Sound waves incident on a thin elastic rod whose radius is smaller than the wavelength of the incident sound induce flexural and uniform compressional oscillations in the rod. These elastic oscillations again radiate sound waves into the fluid medium and affect the scattered waves. This synopsis presents theory of sound scattering by, and acousto-elastic vibrations of, a thin elastic unbound rod in a viscous fluid. The shear viscosity of the fluid was considered in the solutions to the boundary-value problems concerning the sound scattering and the elastic response of the rod. Results show that the scattered compressional waves consist of the rigid-rod scattering of compressional wave, a monopolar wave due to the uniform pulsating of the rod, and a dipolar wave due to the flexural vibration of the rod. The scattered viscous waves consist of the rigid-rod scattering of viscous wave and a dipolar wave due to the flexural vibration of the rod. Acoustic resonances occur when the effective inertia force of the rod balances the stiffness force of the rod. The fluid viscosity and the scattering of sound give rise to radiation damping for the rod vibrations and affect significantly the acoustic resonances.
Ultrasound propagation and scattering in randomly distributed particles
Authors: Machado Joāo C. , Sigelmann Rubens A. , Ishimaru Akira
Published: January 2006

This paper deals with experimental and theoretical investigations aimed at increasing the basic understanding of the interaction of acoustic waves with random media. The ranges of frequency are 0.85–3.0 MHz and 5.0–6.0 MHz. The random medium consists of a suspension of polystyrene spheres (mean diameter 0.589 mm, standard deviation 0.066 mm) in a solution of water and sugar. For different concentrations, experimental results for attenuation and pulse broadening for transmission and backscattering, and attenuation as a function of the receiving angle for transmission only are presented. In the range of 0.85–1.1 MHz, the total scattering cross section of the particles depends on the 13th power of frequency. This dependence is due to the role of shear waves inside the particles. The power spectrum density of a burst of sine wave backscattered from the random medium is measured. The experimental and theoretical results agree well. The complex propagation constant of the coherent wave in the medium with large concentrations of particles is measured. It deviates from those predicted for a low-density medium. For the theoretical calculations, the size distribution of the particles was considered. [Work supported by CNPq in Brazil and the U.S. Army Research Office and the Office of Naval Research.]
Intensity fluctuations of waves propagating in a random medium
Authors: Wenzel Alan R.
Published: January 2006

A theoretical analysis of the wave field radiated by a point source in a one-dimensional random medium is presented. The analysis is based on the quasi-Rytov method, and includes both multiple forward-scatter and multiple backscatter effects. An approximate expression for the mean-square fluctuating intensity is derived under conditions of a weakly dissipative medium. This expression shows that at low and intermediate frequencies the intensity fluctuations are a maximum at the source point, decreasing exponentially with distance from the source. These findings are in qualitative agreement with analytical and numerical results obtained by Kohler and Papanicolaou [J. Math. Phys. 15, 2186–2197 (1974)]. At high frequencies, however, this expression shows that, under certain conditions, the intensity fluctuations reach a maximum at some positive distance from the source, decreasing monotonically with distance in either direction from this maximum point. These latter results are in qualitative agreement with observations of intensity fluctuations of optical waves propagating in the lower atmosphere. [Research supported by NORDA.]
Scattering from gratings of high aspect ratio compliant tubes embedded in an elastomer
Authors: Radlinski Ronald P. , Janus Robert S.
Published: January 2006

An improved formulation for normal incident plane wave scattering from gratings of compliant tubes embedded in a viscoelastic layer immersed in fluid is presented. Approximations to boundary conditions at the interfaces between the interstice and compliant elements are eliminated by treating the interstice as a viscoelastic plate which has the material properties of the polymer matrix material. The compliant tubes are treated as two structurally and acoustically coupled plates with end conditions which correspond to those for the vibrational modes of a highly eccentric elliptical shell. Conditions on normal displacement, normal stress, and tangential displacement relate the compliant plates and viscoelastic plate boundaries to the surrounding viscoelastic layers. Comparisons of the insertion loss for gratings in fluid and gratings in viscoelastic layers in fluid will be shown. Limitations of the analysis will be discussed and calculations will be compared with experimental data.
Precision measurements of the reflection coefficient and of the acoustic impedance of materials in water filled tubes
Authors: Skudrzyk E. J.
Published: January 2006

The reflection coefficient and the acoustic impedance of materials can be measured in tubes either by monitoring the amplitude and phase of reflected sinusoidally modulated pulses, or by determining the resonance frequencies and the damping observed for a continuously excited standing wave. The pulse method has the advantage of isolating the errors caused by the tube constructional arrangement, while the standing wave method integrates these errors with the properties of the test probes. The tube itself affects the experimental results due to vibrations that travel in the wall and are coupled into the water, by additional tube vibrations that occur at its ends and by reflections caused by discontinuities and supports. Also, the transducers will be considered in detail and the effects of damping. In this paper, the behavior of the measuring tube will be analyzed and recommendations will be made for the design of trouble-free test tubes. [Sponsored by NAVSEA O5H and by the Office of Naval Research (Code 479).]
A demonstration of peripheral constraint on an auditory duration discrimination task
Authors: Fleet Gregory J. , Shelton Brian R.
Published: January 2006

An earlier study investigated the discrimination of auditory durations presented at a rapid rate in a two-alternative forced-choice task. The results indicated that a constant Weber fraction was obtained across base durations from 25–1600 ms if a long interstimulus interval (ISI) separated the two alternative presentations, but performance degraded with short base durations if a short ISI was used [B. R. Shelton, J. Acoust. Soc. Am. Suppl. 1 72, S89 (1982)]. Here, the same measurements were taken under two presentation conditions: (1) a binaural presentation of both intervals, and (2) a monaural presentation of the two intervals, each to a different ear. Base durations of 25, 50, 100, and 200 ms were used, with ISI values of 25, 50, 100, 200, 400, 800, and 1600 ms. The binaurally presented condition replicated the previous results, but the presentation of intervals to alternate ears produced a marked improvement in performance, especially with short ISI presentations. This finding suggests that the discrimination of the duration of rapidly presented auditory stimuli is restricted peripherally. [Work supported by NSERC.]
Temporal processing in cochlear implants
Authors: Shannon Robert V.
Published: January 2006

Psychophysical experiments were conducted to assess the temporal processing of patients with multichannel cochlear implants. Threshold and suprathreshold temporal integration were similar to normals, with integration time constants of 100–200 ms and 50–100 ms, respectively. Gap detection decreased from 60 ms near threshold to 1–2 ms for loud stimuli, similar to normals at high frequencies. Forward masking decreased as the delay of the signal from the masker was decreased, with a time course similar to or slightly longer than normals. All of these measures indicate that temporal integration and adaptation in implants are similar to normals, indicating an intact central mechanism. One major difference between implants and normals was in the sensitivity to details of the temporal waveform. Normals hear little or no difference as a function of phase within a complex waveform, but the same stimuli can cause large perceptual differences for implant patients. Implications for implant processor design are considered. [Work supported by NIH.]
Changes of tinnitus pitch after monaural exposure to a 1000-Hz pure tone
Authors: Young I. M. , Lowry L. D.
Published: January 2006

A subject with tinnitus of 10 000-Hz pitch equivalent in the left ear and no tinnitus in the right ear was exposed in the left ear to a continuous pure tone 2000 Hz, 107 dB SPL, for 10 min. This exposure resulted in permanent tinnitus in both ears with similar pitch of 10 000 Hz. When the left ear was exposed to a continuous pure tone 1000 Hz, 123 dB SPL, for 21 min, tinnitus disappeared temporarily from stimulated ear but was heard in the nonstimulated ear. In the left ear: 612 h after stimulation, tinnitus reappeared as a mixture of multiple pitches; 51 h after stimulation, tinnitus pitch changed to 4100 Hz, 3 days later to 5800 Hz, 5 days later to 8700 Hz, and 48 days later to the original 10000 Hz and has remained there since. In the nonstimulated right ear: After stimulation, tinnitus pitch was 7500–8500 Hz for 7 days; thereafter, tinnitus has been fluctuating between 8500–9500 Hz; tinnitus did not return to the preexposure pitch of 10 000 Hz until about 9 weeks after exposure. Difference in recovery between two ears was compared with our previous studies of 125-, 250-, and 500-Hz stimulation.
Diagnosis of childhood respiratory disease based on acoustical analysis
Authors: Slawinska Elizabeth B.
Published: January 2006

Diseases of the respiratory pathways are often associated with a narrowing of the respiratory channel. Different diseases are characterized by a well defined locus of the constriction. Theoretical analyses suggest particular acoustical characteristics which can aid in diagnosis. Predictions include (a) a shift in spectral density to the higher frequency range, due jointly to an enlarged noise source and the constricted respiratory channel, in tonsilitis; (b) specific relations between the acoustical pressure/murmur at inspiration and expiration, in congenital stridor; (c) several noise sources generating large high-frequency amplitudes, in acute subglottal laryngitis; (d) stridor during inspiration if the constriction is in the neck or during expiration otherwise, with the narrowing of the traches. These theoretical predictions are developed and then tested with experimental data obtained from 500 children, including 50 cases of tonsilitis, 47 cases of congenital stridor, 30 cases of subglottal laryngitis, and 24 cases of narrowing of the traches. [Work supported by AHFMR and NSERC.]
Annoyance to advanced turboprop aircraft flyover noise
Authors: McCurdy David A.
Published: January 2006

A laboratory experiment was conducted to quantify the annoyance to advanced turboprop aircraft flyover noise. A computer synthesis system was used to generate 45 realistic, time-varying simulations of propeller aircraft flyover noise in which the harmonic content was systematically varied to represent the factorial combinations of five fundamental frequencies ranging from 67.5 to 292.5 Hz, three frequency envelope shapes representing helical tip Mach numbers of 0.63, 0.73, and 0.78, and three tone to broadband noise ratios of 0, 15, and 30 dB. In the experiment, 64 subjects judged the annoyance of recordings of the 45 synthesized flyover noises presented at D-weighted sound pressure levels of 70, 80, and 90 dB in a testing room which simulates the outdoor acoustic environment. Analyses of the judgments examine the effects on annoyance of the differences in the harmonic content of the flyover noises. The annoyance prediction ability of various noise measurement procedures and corrections is also examined.
Qualification of a hemi-anechoic room for sound power level determination
Authors: Burkewitz Bart L.
Published: January 2006

As part of E-A-R's technical expansion program for its noise and vibration control laboratory, an interim hemi-anechoic room has been added to the facilities. Consistent with collection of quality acoustic data, special acoustic environments need to be understood. To accomplish this, ANSI Standard S1.35-1979, “Precision Methods for the Determination of Sound Power Levels of Noise Sources in Anechoic and Hemi-Anechoic Rooms,” was selected as both a tool to guide study of the room and a documentation procedure to provide assurance to subsequent recipients of results of tests performed in the room. This paper will discuss the specific test procedures used to qualify the room under the standard, data analysis techniques used, and the idiosyncracies involved in performing tests of this type.
Preliminary observations of the influence of casework of pipe organs on room acoustical fields
Authors: Kinzey Bertram Y.
Published: January 2006

A studio organ was built for the University of Florida so that its casework can enclose the pipework except for the open front or be removed to permit pipes to be free-standing. The sound of pipes in various locations was recorded at a number of points in the room with and without the case in place. The university organist recorded the same Bach prelude and fugue using identical registration with and without case enclosure. Data are presented showing the comparative spectral analysis of selected notes with and without casework. Professional musicians were asked to pick the cased and uncased examples of the recorded prelude and fugue and give their reactions. Generally, the sound with the case in place contained louder lower harmonics relative to higher pitches than sound from free-standing pipes. Musicians readily differentiated between the eased and uncased examples of the prelude and fugue and observed a better blending of encased high-frequency notes which was lacking for free-standing pipes.
An aerodynamic study of stops with different phonation types
Authors: Dart Sarah N. , Keating Patricia A.
Published: January 2006

Measurements were made of intraoral air pressure and oral airflow during the production of stops with different phonation types. The sounds investigated include Korean lenis and fortis, and Hindi voiced and murmured, stops. An aerodynamic model was used to simulate possible articulations which could produce air flows and pressures like those observed. For example, higher intraoral pressure and lower oral flow were found for Korean fortis as compared to lenis stops. This difference follows from a simulated difference in vocal tract wall tenseness. Furthermore, the right shape of intraoral pressure curves can be simulated with a difference in subglottal pressures. This analysis-by-synthesis approach, combining physiological measurements and articulatory modeling, provides new insights into differences in phonation types. [Work supported by USPHS grant NS 18163-02 to Peter Ladefoged.]
Control of rate and movement duration in speech
Authors: Ostry David J. , Munhall Kevin G. , Parush Avraham
Published: January 2006

This paper provides evidence on the control of rate and movement duration in speech. A computerized pulsed-ultrasound system was used to monitor separately tongue dorsum movements and laryngeal gestures during the production of CV and CVCVC sequences. The kinematics of tongue and laryngeal movements were analysed by partitioning the lowering gesture of the tongue and both the abduction and addution gestures of the vocal folds to give estimates of displacement, duration, and maximum velocity. For both articulators the ratio of the maximum velocity to the extent of the gesture was found to vary inversely with the duration of the movement. The finding suggests that a single function might account for a wide range of changes in the duration of individual gestures. The control of movement rate and duration through the regulation of biomechanical characteristics of speech articulators is discussed.
Ultrasonic orientation methods for tongue scanning
Authors: Hamlet Sandra L.
Published: January 2006

Real-time ultrasonic imaging of the tongue presents a problem in verification of the orientation of the scan, especially when detailed measurements are to be made, or replication of measurements is attempted. Ultrasonically identifiable landmarks may be free to move (e.g., hyoid bone) and thus present an inherently unstable reference. A review and evaluation of various orientation techniques is presented, including (1) use of external facial features for transducer placement, (2) use of ultrasonically distinguishable anatomy, (3) placement of oral markers or probes, (4) adoption of standard speech and speech-like gestures. [Work supported by NIH.]
Jaw muscle activity for speech and nonspeech gestures
Authors: Gentil Michèle , Gay Thomas
Published: January 2006

The activity patterns of the mandibular elevator muscle system were investigated for speech and nonspeech gestures for the purpose of determining the possibility of neuromuscular specialization for speech in relation to other mandibular functions. Intra-muscular wire electrodes were placed into the seven mucles of the mandibular system and the anterior belly of the digastric. The activity of these muscles was recorded along with a time varying magnetometer voltage that corresponded to the displacement of the jaw in two and three dimensional space. These signals were recorded from three adult American English subjects during the production of speech at different rates and for nonspeech gestures that included border movements, functional opening-and-closing and mastication. Results indicated that jaw space for speech is the most restricted of any mandibular function, jaw movements for speech are generally produced by the most simple muscle action patterns and individual differences exist in the selection of a given muscle or muscle system for a specific function and/or utterance, and in the coordination of muscle activity patterns for any particular gesture. [Research supported by a grant from the National Institute of Health (NS-10424).]
Differential negative resistance in a one-mass model of the larynx with supraglottal resistance
Authors: Conrad William A.
Published: January 2006

The steady flow calculations of Conrad [Conference on Physiology and Biophysics of Voice, Iowa (1983)], show that the larynx can manifest a differential negative resistance, i.e., translaryngeal pressure can decrease as flow rate increases. These calculations were based on the one-mass model of Flanagan and Landgraf [IEEE Trans. Audio Electroacoust. AU-16, 57–64 (1968)] with added supraglottal resistance. If the spring acting on the mass is changed from linear to nonlinear, the differential negative resistance becomes bounded by two regions of positive differential resistance. As nonlinear stiffness increases, differential negative resistance disappears. The one-mass model plus supraglottal resistance can be described as an N-type, flow-controlled nonlinear resistance, QNLR. It is well known in electronics and elsewhere that a QNLR in a series resonant circuit can transform de power to oscillatory power [e.g., Ph. le Corbeiller, Proc. Inst. Elec. Eng. 79, 361–378 (1936)]. The system can be usefully analyzed in terms of van der Pol's equation which gives the oscillation condition, the frequency, rate of build-up, limiting amplitude and efficiency. The analysis shows that differential negative resistance is a necessary condition for oscillation.
Effects of phrasing and word emphasis on transitional movements—Location and stability of tongue blade iceberg patterns
Authors: Fujimura O. , Spencer W. R.
Published: January 2006

In previous ASA meetings, it was suggested that certain movements of an articulator that is crucial for both CV and VC identities were often observed unaffected in their nearpeak parts as stable fragmental time functions, even when large variation in other portions such as vowel portions was introduced by prosodic control. By an automatic procedure, we have identified the parts of demisyllabic transitions that are likely to be stable under manipulation of phrasing such as (21 + 2) × 3 vs 21 + (2 × 3), and contrastive emphases placed on different words in a sentence such as “It's 9 8 11 Brooks Drive.” The data were obtained by the computer controlled x-ray microbeam system at the University of Tokyo [Kiritani, Itoh, and Fujimura, Acoust. Soc. Am. 57, 1516–1520 (1975)], and pertain, in this paper, to the vertical position of a metal pellet placed on the tongue blade.