bluuebunny/crossref_metadata_2025 huggingface dataset:
Asymptotic descriptions of the acoustic signatures of surface-breaking cracks.
Authors: Harris J. G. , Rebinsky D. A.
Published: October 2005

This describes work on modeling asymptotically the acoustic signature, measured with a scanning acoustic microscope having a line-focus or point-focus lens, of a surface-breaking crack. This is a continuation of the work presented at the Spring 1991 ASA Meeting [J. Acoust. Soc. Am. 89, 1923 (A) (1991)]. The crack is modeled as a vertical discontinuity that can be characterized by reflection and transmission coefficients. Asymptotic expressions describing the incident and scattered wave fields, including the leaky Rayleigh waves scattered from the discontinuity, are given. The acoustic signatures are calculated by using an electromechanical reciprocity identity to relate the wave fields at the specimen’s surface to the voltage at the terminals of the microscope’s transducer. For the line-focus microscope, explicit expressions for the reflection coefficient of a normally incident Rayleigh wave reflecting from a surface-breaking crack are given in terms of the acoustic signatures for a perfect and cracked surface. For the point-focus microscope, explicit expressions for the same reflection coefficient, even though the Rayleigh wave now propagates in two dimensions rather than one, are also given in terms of the signatures for a perfect and a cracked surface. Initial work to assess the influence of the condition of the specimen’s surface upon the acoustic signature will be reported. [Work partially supported by MRC at UI.]
Acoustic response of a rectangular cavity with orifices.
Authors: El-Raheb Michael , Wagner Paul
Published: October 2005

The acoustic response of a rectangular cavity to excitation through waveguides terminating at orifices in the cavity walls is analyzed. Acoustic pressure is expressed by eigenfunctions satisfying Neumann boundary conditions as well as by those satisfying Dirichlet ones. The change in boundary condition from wall to orifice is included by appeal to Lagrange undetermined multipliers. The acoustic consequences of an orifice may be summarized as follows. Resonances of the cavity with zero impedance orifices are higher than those of the cavity without orifices. In particular, the low-order mode (0,0,0) has zero frequency for the simple cavity but appears at finite frequency for a range of orifice impedance. Within a narrow range of orifice impedance, every resonance displays great sensitivity to impedance change. Qualitatively, orifices reproduce the effect of a uniform change in wall impedance. A gap between the speaker diaphragm and a waveguide reproduces these orifice-generated effects.
Simultaneous measurement of ultrasonic velocity and sample thickness and its application to NDE of composites.
Authors: Hsu David K. , Hughes Michael S.
Published: October 2005

Ultrasonic velocity is widely used for nondestructive evaluation of material properties. In cases where the thickness of the test piece is not precisely known or varies spatially, it is desirable to be able to determine the ultrasonic velocity and the sample thickness simultaneously. In immersion tests, the velocity and the thickness may be determined simultaneously by measuring a number of times-of-flight [cf. Kuo etal., J. Acoust. Soc. Am. 88, 1679–1682 (1990)]. In this work the ‘‘simultaneous’’ method was tested in four different configurations of pulse echo and through transmission and was applied to the characterization of porosity in graphite polyimide and graphite–epoxy composites. In addition, the velocity-thickness method was also implemented with water squirters. [Work supported by Center for NDE, Iowa State University.]
Pulsed signal coherence propagation in one-dimensional dispersive waveguides.
Authors: McCoy John J.
Published: October 2005

A coherence formulation is achieved for a one-dimensional, dispersive waveguide forced by a windowed (in space and time), otherwise statistically homogeneous and stochastic forcing. This formulation serves as the starting point for the reduction to a theory for the diffusive flow of a measure of the smoothed energy density in a time (or position) spectral space. Connection is made to other, adhoc, power flow formulations governing the transport of acoustic energy through these simple structural elements.
Effects of fluid loading and mean flow on acoustic radiation from two semi-infinite co-planar dissimilar plates.
Authors: Wu X.-F. , Akay A.
Published: October 2005

This paper is concerned with the problem of sound radiation from two co-planar plane semi-infinite plates subjected to a sinusoidal line force acting at the joint. The plates are made of different materials and thicknesses, connected in different ways, and are in contact with some fluid on one side but vacuum on the other side. The fluid is in uniform motion parallel to the plane of plates at a constant subsonic speed. The governing equations of motion for the plates are coupled to fluid pressure fluctuations through boundary conditions at interfaces. Since the boundary conditions on two dissimilar plates are different, the Winner–Hopf technique is used, and the solution of the acoustic pressure is obtained in the form of spatial Fourier transformations. To circumvent the numerical computational difficulties encountered in the inverse Fourier transformations, an Euler transformation is employed. This transformation enables one to replace the original infinite line integral by a contour integral which, in turn, is evaluated by Cauchy’s residue theorem. Numerical results indicate that the mean flow tends to reduce the magnitude of the far-field acoustic pressure in the direction normal to the plates and cause fluctuations in the acoustic pressure distribution in the near field. Moreover, the effects of mean flow for a lightly fluid-loaded system are more significant than those for a heavily fluid-loaded system. [Work supported, in part, by ONR, NSF, and IMR of Wayne State University.]
HIFE signal processing results.
Authors: Dzieciuch Matthew A. , Metzger Kurt , Birdsall Theodore G.
Published: October 2005

The most remarkable feature of the HIFE receptions is their phase stability in both time and frequency. Examples include (1) tracking of the peak-energy bin of FFT’s, (2) refinement of the carrier estimate to a precision adequate to estimate the transmission launch angle, and the small residual phase deviation track over a full hour, (3) the small phase swing of the integrated autocorrelation phase (IAP1) over one full hour, (4) the phase stability of arrivals, after removal of the broadband phase deviations measured by IAP1, and (5) comparison of the measured distributions of amplitude and phase of the individual frequency lines and individual time arrivals. The implications for phase coherent signal processing, in particular for more frequent transmissions in fixed–fixed tomography and for Doppler utilization in moving source tomography, will be discussed. Last but not least, the utilization of the arrival phase along the several sheets of propagating timefronts by passive broadband channel matching will be discussed.
Downhole instrumentation for seismic waves.
Authors: White J. E.
Published: October 2005

Surface-to-borehole seismic waves have been used from the early days of seismic exploration [B. McCollum and W. W. LaRue, Bull. AAPG 15 (11), (12) (1931)]. As long as the arrival time of the most direct compressional wave was the only observation, a geophone hanging on a cable sufficed, and it did not matter that the ensuing signal was dominated by acoustic waves in the mud column. Mathematical modeling and field measurements have guided the development of geophones that are pressed against the hole wall, greatly reducing sensitivity to these mud-borne waves and more faithfully measuring the three components of motion in the solid around the hole. Analysis and measurements also show that shear and compressional waves passing the borehole create pressure signals in the mud column. Pressure detectors have the advantage that they do not need to be clamped, but this means that suppression of the mud-borne signals must be achieved in some other way. Borehole sources that act by way of volume change create strong mud-borne waves that then act as secondary sources at any discontinuities along the borehole. This is analogous to the pressure detector. If the sources were clamped to the wall and forces were thus applied directly to the solid, mud-borne waves would be suppressed in a manner analogous to the clamped geophone.
Finite element modeling of acoustic transducers.
Authors: Hamonic B. F. , Decarpigny J.-N.
Published: October 2005

In recent years, the need for designing piezoelectric or magnetostrictive acoustic transducers with actually three-dimensional geometries and thus exhibiting complex displacement fields has become urgent. This is the case in underwater acoustics, for sonar or oceanographical applications, with the renewed interest in flextensional projectors or various Helmholtz resonators. This is also the case in the field of geophysical exploration, where the specific conditions related to the borehole dimensions and to the harsh environment as well as the use of dipole sources imply the development of specific transducers such as rings or benders. The use of simple models to optimize these types of transducers is difficult, if not impossible. Thus numerical methods such as finite elements or integral equations are needed to reach this goal. The purpose of this paper is first to describe the use of the finite element method to analyze the static, modal, or harmonic behavior of transducers. A brief survey of the theoretical formulation is given while more emphasis is devoted to the modeling conditions. Coupling to integral equations is also discussed. Then, some numerical results obtained for in-air and in-water transducers using the atila code are described and compared with experimental results. Finally, a temperature analysis of the problem related to the modeling of the acoustic wave propagation in the formations is discussed.
An acoustical approach to the Greek flogera.
Authors: Papadelis George , Papanikolaou George
Published: October 2005

The flogera is a simple structured bamboo woodwind and the most typical musical instrument played by the Greek shepherds. It consists of a cylindrical bore, with uniform internal diameter, open at both ends and a system of seven finger holes. The higher open end acts as the sound production mechanism, by blowing a narrow air stream against its sharp edge. The equivalence between musical tones, emitted by a medium sized flogera, and various ‘‘effective lengths’’ of its bore were investigated on the basis of A. H. Benade’s ‘‘Mathematical theory of woodwind finger holes’’ [J. Acoust. Soc. Am. 32, 1591–1608 (1960)]. Laboratory spectral analyses have been done for sound samples produced by some basic fingerings of the instrument. Embouchure’s ‘‘effective length corrections’’ have been calculated throughout the hole range of the instrument, concerning the fundamental and the first three overtones of each musical tone. On the basis of the above results, tables and histograms have been constructed, concerning various ‘‘length corrections’’ relevant to each part of the instrument. A table was also created showing the magnitude (in cents) of all possible musical intervals played by the instrument. A comparison with modern instrument building aims is finally discussed.
Multiple scattering from many bounded obstacles in a multilayered acoustic medium.
Authors: Lim Raymond
Published: October 2005

At a previous meeting of the Society, a multicentered, transition (T) matrix formalism was suggested for scattering calculations involving many bounded obstacles in homogeneous fluid and solid hosts [Lim and Hackman, J. Acoust. Soc. Am. Suppl. 1 87, S40 (1990)]. In this paper, an extension of that formalism to the problem of multiple scattering from many bounded obstacles arbitrarily distributed in a plane-stratified acoustic medium is presented. Hackman and Sammelmann [J. Acoust. Soc. Am. 84, 1813–1825 (1988)] have given an elegant solution for scattering within a waveguide containing a single obstacle. The present extension is obtained by expanding the multiply scattered field from each obstacle within a layered fluid using their waveguide-obstacle T matrix and obstacle-centered, outgoing eigenfunctions appropriate to the layered medium. Waveguide Green functions are expanded in appropriate regular eigenfunctions to get the incident field coefficients required for the scattered field calculation. To complete the formulation in analogy to multiple scattering in an infinite, homogeneous medium, the translation matrices for these eigenfunctions are derived. The resulting solution is formally exact to all orders of multiple scattering among the obstacles and the waveguide. Also, it is simple to extend the method to calculate the field scattered from infinite, periodic arrays insonified by plane waves in the waveguide.
Scattering from shells with internal structural loading. Part II. Results and discussions.
Authors: Guo Yue-Ping
Published: October 2005

The solution procedure developed in the preceding paper is utilized in this paper to examine a large number of model problems with different forms of internal structural loading, ranging from simple mass-spring oscillators to elastic structures. The results are analyzed to answer questions such as in what frequency domains the internals play an important role in the scattering process, how the structural details affect the scattered field, and where are the loading/observation positions where the loading effects are most significant. It is shown that in the mid-frequency region, which is of main concern here, internal structural loading significantly affects the scattering characteristics, but the scattered field is not sensitive to the details of the internal loading for practical values of the internal system parameters. The positions of the loading points relative to the incidence angle of the incoming sound waves are shown to be important to the scattered field, which determine whether the loading effects are purely geometrical or dynamical. [Work supported by ONR.]
Prosodic influences on the perceptual organization of sentences by young and elderly listeners.
Authors: Wayland Sarah C. , Wingfield Arthur , Stine Elizabeth L.
Published: October 2005

Spoken sentences with normal or anomalous prosody (‘‘In her hope of marrying/ Anna was surely impractical.’’ versus ‘‘In her hope of marrying Anna/ was surely impractical.’’) were presented at speech rates of 187, 234, or 312 words per minute to young and elderly listeners. Elderly listeners’ recall was less accurate overall than young listeners’ recall, especially at higher speech rates. While recall of sentences with normal prosody was almost always near perfect, recall for sentences with anomalous prosody decreased as speech rate increased. Further analysis of listeners’ recall indicated that young listeners were more likely to restructure the prosody of the sentence to match the syntax they had heard. Elderly listeners, on the other hand, were more likely than younger listeners to restructure the syntax of the sentence so it would fit the prosody they had heard. Thus it appears that elderly listeners rely on prosodic information to help them organize sentences at a syntactic level to a greater degree than do younger listeners.
Preplanning and intonation in Peninsular Spanish.
Authors: Toledo Guillermo A. , Martínez Celdrán Eugenio
Published: October 2005

The goal of this paper was to test mental preplanning in the intonational behavior of Peninsular Spanish speakers. In one experiment of production, the P1 effect in data of sentences of increasing length was investigated in order to provide support to look-ahead strategies. In a second experiment, the weight of clause syntactic boundaries in local fall–rise patterns (and versus but versus that versus noun phrase and) as explored with the aim to examine cognitive processes connected with global preplanning, tonal encoding, and syntax. Measurements were made through digital contours of three male speakers from different Mediterranean dialects. Here, F0 results did not confirm any effect of preplanning: P1 showed no correlation with length; fall–rise patterns were similar in all linguistic conditions. These findings were in perfect accord with previous results in American Spanish corpora [G. Toledo and J. Gurlekian, in EstudiosdeFonéticaExperimental, edited by E. Martínez Celdrán (University of Barcelona, Barcelona, 1990), Vol. IV, pp. 27–49].
The Tasman blockage: An acoustical sink for the Heard Island feasibility test.
Authors: Forbes Andrew M. G.
Published: October 2005

Low-frequency (57-Hz) signals from the Heard Island feasibility test, conducted in January 1991 were received on many hydrophones around the globe. The Atlantic and Indian Ocean paths were relatively clear and unimpeded, so received signal-to-noise ratios (after some averaging) were generally high. The Pacific paths were not as clear and considerable interaction with bathymetric features attenuated the signals received off the west coast of the US. It appears that the only successful paths from Heard Island through the Pacific passed south and east of New Zealand. A New Zealand-manned receiver in the Tasman Sea received the transmissions strongly, but a Japanese ship, placed strategically northeast of the South Fiji (Lau) Ridge did not detect any signals. There is good evidence from Whidbey Island receivers (with beam forming capability), that the signals arrived from 20 deg further south (i.e., from south of New Zealand) than if they had passed through the Tasman Sea. Doppler-derived matching of transmitted and received azimuths further indicates that signals received from Whidbey Island to Los Angeles all traveled south of New Zealand. A series of transverse ridges lying between northern New Zealand and New Caledonia and Fiji appears to have effectively blocked the transmission from exiting the Tasman Sea. An adiabatic modal model of refracted geodesic raypaths (developed at NRL, Washington, DC) sheds some light on the reasons for such effective blockage.
Recognition of familiar calls by the Emperor Penguin (Aptenodytes
forsteri)−How important are call timing, spectral characteristics, and frequency modulation?
Authors: Bowles A. E.
Published: October 2005

To determine whether call frequency, mode timing, time-varying frequency cues, or spectral (timbral) characteristics were important to call recognition in the Emperor Penguin, a phase vocoder was used to vary timing and frequency parameters of natural display calls independently. The syntheses were of five types: natural display calls; noise bursts with the correct timing, but without either the harmonic spectrum or frequency modulation of the natural call; modes with the correct spectral characteristics and timing, but lacking frequency modulation; calls with timing lengthened or shortened without altering spectral characteristics; and ‘‘hybrid’’ calls with the correct frequency spectrum and modulation of one individual, but the mode timing of another. Syntheses were based on natural calls of familiar and unfamiliar individuals. They were played to 52 emperors in an artificial habitat at Sea World of California. Since Emperors respond preferentially to the calls of strange individuals, differences in response rates could be used to assess perception of the synthetic calls. Displays, agonistic encounters, and contact calls were measured. Long calls appeared to be more attractive than short ones independent of familiarity. Frequency cues were attended to preferentially over timing of the modes (mixed-model MANOVA over all response types, N=16 experiments, df=5,5, P=0.023).
Passive localization of calling animals using acoustic tomography.
Authors: Spiesberger John L. , Bowlin James
Published: October 2005

The temporal and spatial patterns in the distribution of animals are poorly understood primarily because of inadequate observation techniques. A new passive localization technique (acoustic tomography) is experimentally demonstrated which automatically localizes the positions of calling animals with rms errors of a few centimeters from measurements of the call’s travel-time difference at several pairs of microphones [J. L. Spiesberger and K. M. Fristrup, Am. Naturalist 135, 107–153 (1990)]. Tomographic localization is significantly more precise (by factors from about 2 to 100) than passive acoustic techniques used previously because tomography accounts for and estimates the sound speed and wind fields which significantly modify the travel-time differences. Experimental results will be presented of tomographic localization and tomographic mapping of the sound-speed field in the atmosphere.
ESWL and cavitation bubble dynamics.
Authors: Church Charles C. , Cordry Sean M. , Crum Lawrence A.
Published: October 2005

For a period of several months the authors have had the opportunity to use a Dornier XL1 experimental lithotripter. With this device a detailed investigation of the role of acoustic cavitation in stone commination, has been undertaken using facsimile stones made of plaster of Paris. These results will be presented as well as studies of the nonlinear bubble dynamics of cavitation bubbles produced by the experimental lithotripter. [We acknowledge the Dornier Corporation for the use of the experimental lithotripter as well as support in part by the NIH.]
Examining the validity of the Articulation Index calculations in spaces with concave sound reflecting surfaces.
Authors: Khaiyat Sami A. , Boyer Lester L.
Published: October 2005

The objectives of this paper are (a) to discuss the problem of speech intelligibility in spaces with concave surfaces and how current methods for the Articulation Index (AI) calculations may give architects misleading estimates of intelligibility and (b) to explore the application of two methods to determine possible modifications to current AI calculations for estimating speech intelligibility in spaces with concave wall surfaces. Spoken speech intelligibility tests will be conducted in both small and large mosques with different sizes of concave surfaces on the front wall, as special cases for investigation. The modified rhyme intelligibility test will be used with a male speaker and human subjects. The other method of investigation is to obtain the RASTI measurements utilizing a speech transmission meter and a head simulator. The key variables being considered for this investigation are (a) the size of curvature, (b) the signal to noise ratio, and (c) the source position with respect to the center of curvature as well as the listeners.
A physical measure of consistency among speech parameter vectors: Application to speech intelligibility determination.
Authors: Power Matthew H. , Braida Louis D.
Published: October 2005

A new computational approach is being investigated for determining the intelligibility of speech subjected to a waveform degradation or signal-processing transformation. The approach employs a model of the human auditory system which reduces a speech waveform to a sequence of discrete symbols, each representing a prototypical vector of parameter values measured in a single frame (10 ms) of speech. The perceptual effect of the transformation is estimated by assessing the consistency between the symbol sequence derived from an untransformed (input) speech signal, and that derived from a transformed (output) signal. This is implemented via calculation of percent transmitted information. Degradations studied thus far include linear filtering and additive white noise. Using parameters that represent only band energies, transmitted information is halved for 2.5-kHz highpass and 3-kHz lowpass filtering. By contrast, the effect of noise is much more severe: halving is observed at approximately +30 dB SNR. Efforts are currently underway to improve the model’s behavior, particularly in noise. [Work supported by NIH.]
A multichannel computer-enabled microphone array for use with hearing-impaired children in classrooms.
Authors: Yonovitz A. , Yonovitz D.
Published: October 2005

Many investigations have shown that background noise is generally more deleterious to the hearing-impaired student than a normal listener. Classroom acoustics impart a nearly intolerable noise level, excessive reverberation, and talker variations in intensity for the impaired ear. A low signal-to-noise ratio (S/N) is detrimental to the hearing-impaired student’s understanding of the speech signals from speakers within the classroom, and therefore does not optimize discrimination. Improved S/N can be obtained through the use of a microprocessor based multichannel microphone system. Scanning 32 microphones, a computer-enable microphone system, provides an efficient way to minimize the amount of background noise received by the hearing-impaired students, and consequently improve speech discrimination skills. Technical considerations for attack and release times and adaptive processing of background noise will be presented. Data are shown, which indicate with hearing-impaired students, the expected gains in speech discrimination with this and conventional auditory training systems.
Human auditory response to low flying aircraft noise.
Authors: Nixon Charles W. , West Denise M. , Allen Nancy K.
Published: October 2005

Noise from low flying aircraft may constitute a potential risk of noise induced hearing loss. In this study, hearing threshold levels were measured following human exposures to audio recordings at ground level of noise from low flying aircraft. The noise was characterized by sudden onset, durations of about 10 s, maximum A-weighted sound pressure levels in the frequency region of 1200–2400 Hz, and A-weighted peak levels up to 130 dB. The primary independent variables were A-weighted peak levels and successive repetitions of the noise. In phase I, subjects experienced single noise bursts with the first at a level of 115 dB and each succeeding noise increased an additional 5 dB until a temporary threshold shift (TTS) was observed or the maximum level of 130 dB was completed. In phase II, a single noise burst was repeated at the same sound level up to eight successive repetitions or until a TTS was observed. Hearing threshold levels were measured at 4 and 6 kHz immediately following each individual noise burst. Results will be discussed in terms of noise induced hearing loss relative to damage risk criteria and ISO 1999.
Noise and hearing conservation: Young adults’ habits, knowledge, and attitudes.
Authors: Johnson Carole E. , Gorman Sammi , Tracy LaQuita , Stein Ramona L.
Published: October 2005

According to the National Institutes of Health (NIH), approximately 28 million individuals in the United States suffer from significant hearing loss. More than one-third of those losses are attributable to noise exposure [Lankford, Hearing Instruments 41(10), 6 (1990)]. Between 1971 and 1985, the number of persons aged 35–44 years suffering from hearing loss increased from approximately 55 to 85 per thousand−a larger increase than for the 45–54 or 65 year old and older age group. Two hundred young adults, ages 14 to 38 years, were surveyed via a 20-item questionnaire concerning their habits pertaining to, knowledge of, and attitudes toward noise and hearing conservation. Results indicated that the majority of young adults participated in activities exposing them to excessive noise levels at least twice a week and for several hours in duration for each activity. Further, the large majority reported at least one incident of having symptoms (e.g., tinnitus) of overexposure to noise resulting from those activities. Although the large majority demonstrated basic knowledge about the effects of noise on hearing, most had deficiencies in their knowledge of the effectiveness of hearing protection devices (HPDs) and would feel self-conscious in using them or taking other measures to circumvent noise-induced hearing loss.
Bioacoustic’s anthropometric manikins for acoustic research.
Authors: Obert Angela R.
Published: October 2005

Bioacoustic’s anthropometric manikins for acoustic research (BAMAR) are being developed for use as surrogate humans in selected types of acoustics measurements. Some of the applications targeted for this capability are measurements of sound attenuation of helmet, earmuff, and earplug hearing protection devices, voice communications effectiveness, sound/noise measurement, and transducer design/evaluations. The manikin heads are high fidelity anthropometric replicas of human subjects chosen to represent average, ±1, and ±2 standard deviation head sizes. The BAMAR set consists of ten manikin heads including pinnae and external ear canals fabricated with artificial flesh. The manikins are instrumented with appropriate measurement transducers. The approach involves validation of performance by directly comparing performance of the human subject with that of his/her own manikin. The procedure for creating the manikins, the rationale, and the progress of the developmental effort will be discussed. Sound attenuation data will be presented for the human subject and for the corresponding manikin.
Implementing the tasks associated with the condition monitoring and diagnostics of mechanical systems: Using as an example the vibration condition monitoring and diagnostics of machines.
Authors: Muster Gordon Lewis
Published: October 2005

In the past decade, there have been significant improvements in the manner in which one implements the tasks associated with the condition monitoring and diagnostics of mechanical systems. Here, used as an example of these improvements are the technologies related to the art of vibration condition monitoring and diagnostics of machines, including those related to motion sensors and their associated instrumentation, the handling, processing, and storage of information and data by computers, user interfaces, and databases. Looking forward to the next decade, there is every indication that equally significant advances can be anticipated in these technologies, particularly in those related to monitoring and diagnosing−in real time−the trends in the responses of such high-speed machines as gas turbines to sudden changes in speed and power demand. The engineer/operators of such modern, high-speed machines seek assurance that their machines can be operated safely and efficiently at, and even beyond, their design limits. In turn, this is putting pressure on the designers and manufacturers of the computer-based instrumentation subsystems that actually perform the tasks of sensing, measuring, analyzing, processing, and storing information and data essential to every condition monitoring and diagnostics system. The problems associated with meeting these sometimes conflicting requirements are discussed here.
Surface tension and viscosity from damped oscillations of acoustically levitated viscous droplets.
Authors: Bayazitoglu Yildiz
Published: October 2005

Modulated shape oscillations of acoustically levitated droplets have been of great interest in recent times, both due to its intrinsic value in studying interfacial dynamics of liquid droplets, and the possibility of developing methods to measure surface tension and viscosity of liquids from the oscillatory behavior. First, the damped oscillations of viscous droplets will be considered in detail, and the effect of the fluid properties on the dynamics will be examined. The inverse problem of measuring surface tension and viscosity from known frequency of oscillations and damping rate will also be addressed. These results are, however, for a freely oscillating, spherical droplet. The presence of acoustic forces at the interface will, doubtless, distort the shape of the droplet. Droplet distortion, in turn, affects the resonance characteristics of the droplet. For example, the usual fivefold degeneracy of the natural frequency no longer holds well. Oscillations of an aspherical droplet subjected to external forces will be analyzed, and the solution will be particularized for the acoustic case. It will be shown that the frequency split can be taken into account while measuring the surface tension, and that this task is relatively simple in the case of acoustic levitation due to the nature of the radiation pressure. The improvement in the surface tension measurement will be demonstrated using a previous experimental result, and the talk will be concluded with a look at future directions. [Work supported by JPL/NASA and TATP Texas.]
Statistical analysis of bilingual speaker’s speech for cross-language voice conversion
Authors: Abe Masanobu , Shikano Kiyohiro , Kuwabara Hisao
Published: October 2005

The goal of cross-language voice conversion is to preserve the speech characteristics of one speaker when that speaker’s speech is translated and used to synthesize speech in another language. In this paper, two preliminary studies, i.e., a statistical analysis of spectrum differences in different languages and the first attempt at a cross-language voice conversion, are reported. Speech uttered by a bilingual speaker is analyzed to examine spectrum difference between English and Japanese. Experimental results are (1) the codebook size for mixed speech from English and Japanese should be almost twice the codebook size of either English or Japanese; (2) although many code vectors occurred in both English and Japanese, some have a tendency to predominate in one language or the other; (3) code vectors that predominantly occurred in English are contained in the phonemes /r/, /æ/, /f/, /š/, and code vectors that predominantly occurred in Japanese are contained in /i/, /u/, /N/; and (4) judged from listening tests, listeners cannot reliably indicate the distinction between English speech decoded by a Japanese codebook and English speech decoded by an English codebook. A voice conversion algorithm based on codebook mapping was applied to cross-language voice conversion, and its performance was somewhat less effective than for voice conversion in the same language.
The interaction of energy flows of underwater ambient noise and a local source
Authors: Shchurov V. A. , Ilyichev V. I. , Kuleshov V. P. , Kuyanova M. V.
Published: October 2005

This paper describes the phenomenon of cancellation of opposing acoustic energy flows observed in an oceanic waveguide. One of the flows is a vertical (or horizontal) energy flow of dynamic underwater ambient noise, and the other (opposing) one is a vertical (or horizontal) energy flow from a local source. Results of a field experiment in the deep ocean are presented which show that the above-mentioned phenomenon leads to the destruction of coherence between the vertical and horizontal components of the particle velocity and pressure.
Application of a hard truncated wedge theory of diffraction to wide barriers
Authors: Don C. G.
Published: October 2005

A recently developed theory by Tolstoy [IEEE J. Ocean Eng. 14, 4–16 (1989); J. Acoust. Soc. Am. 85, 661–669 (1989)], which exactly calculates the attenuation produced by a truncated wedge barrier, has been adapted to assume a line source parallel to the barrier. The theoretical results are compared with experimental measurements obtained using acoustic impulses and rectangular barriers up to 0.45 m wide. The results are also compared with other wide-barrier prediction techniques. It is shown that the refinement to include multiple scattering between the vertices is generally unimportant and can lead to erroneous results if the necessary series are not summed over hundreds of terms. The phase information provided by the theory is evaluated by comparing predicted and measured impulse waveforms obtained behind the barrier.
Chairman’s introduction: Measurement of pressure fluctuations in turbulent boundary layers
Authors: Zuckerwar Allan J.
Published: October 2005

The motivation for organizing the session and a brief introduction to each speaker are presented.
The wave-vector-frequency spectrum of pressure on a smooth plane in turbulent boundary-layer flow at low Mach number
Authors: Chase David M.
Published: October 2005

Properties of the wave-vector-frequency spectrum of fluctuating pressure on a smooth planar wall in turbulent boundary-layer flow at low Mach number are reviewed. In the low but incompressive wave-number range, where ω/c≲K≲max(δ−1,U∞/ω), consistent with the Kraichnan–Phillips hypothesis for inviscid flow, the dependence would be expected to be as K2, but no experimental substantiation exists. In a higher subconvective range where δ−1≲K≲ω/U∞, most pertinent experiments suggest that the spectrum is instead wave-number-white. In the acoustic domain a peak is predicted at K=ω/c. A mean-shear contribution proportional to the square of streamwise wave number appears predominant in the convective domain. An explicit model spectrum is specified that conforms in an appropriate domain to the principle of wall similarity and corresponds to boundary-layer velocity spectra that are planar isotropic in a convected frame. The model potentially encompasses the entire inviscid domain, including the acoustic range. An alternative model exhibits a factorable dependence on the wave-number components. In the acoustic range, the model forms are totally unvalidated by experiment. In the convective domain, the state of determination suffices for many applications, but a preference between model forms and assured choice of parameter values awaits further analysis and perhaps certain further measurements. An addendum based on recent work suggests that the wall pressure at low but incompressive wave numbers may be dominated by a wave-vector-white contribution originating in the viscous wall condition.
Matrix solution of transient high-order ultrasonic scattering
Authors: Cavicchi Thomas J.
Published: October 2005

With the advent of large storage and high speed capabilities of digital computers, computations previously considered intractable have become feasible. One area in which this fact is especially relevant is in the numerical modeling of wave propagation. In this paper, a sequel to a previous one [T. J. Cavicchi, ‘‘Transient high-order ultrasonic scattering,’’ J. Acoust. Soc. Am. 88, 1132–1141 (1990)] a time-domain moment method expansion is, through computer simulations, demonstrated to be capable of solving a temporal forward scattering problem for small, fairly strong cylindrical scatterers. It is, however, very computationally intensive, so detailed studies of the matrix structure are presented. Such studies are useful in optimizing the current method in order to make feasible more practical medical imaging studies.
Reflection and transmission properties of elastic waves on a plane interface for general anisotropic media
Authors: Mandal Batakrishna
Published: October 2005

The reflection and transmission coefficients of elastic waves are calculated numerically at the interface (solid–solid) for general anisotropic media oriented in any arbitrary direction. The plane-wave solutions in anisotropic media are considered. The eigenvalues (slownesses) and the eigenvectors (polarizations) are computed from the 6×6 system matrix A of each medium using a numerical approach. The z component of the Pointing vector and the radiation condition are used to separate the up- and down-going propagations. The solution of reflection and transmission coefficients at the interface are computed in terms of a scatterer operator approach (connecting the up- and down-going wave components of the two sides of the interface). In this procedure, all the possible wave types (nine combinations as: @/iqP−qP, qP−S1, qP−S2, S1−qP, S1−S1, S1−S2, S2−qP, S2−S1,@/r and S2−S2) of the reflection and the transmission coefficients are at the interface. It is preferable to represent the coefficients as a function of slowness, rather than the conventional angle of incidence, because a common reference for P and S waves can be used, thus displaying many of the characteristics more clearly. The coefficients depend, in general, on the polar and azimuthal angles of incidence, and the relative values of the elastic constants in the media on the two sides of the interface. Results for fractured media are presented. Some comparisons with the isotropic model are also presented to clarify the behavior of wave propagation in anisotropic media. Complete synthetic waveforms from an explosion source are computed to observe the effects of anisotropy on amplitude and phase at both sides of the interface.
Derivation of closed-form expressions for the T matrices of Rayleigh–Rice and extinction-theorem perturbation theories
Authors: Roginsky J.
Published: October 2005

Closed-form expressions are derived for the Rayleigh–Rice and extinction-theorem perturbation theories for the case of Dirichlet boundary conditions. It is shown that the two theories are related through the reciprocity transformation to all orders. It follows that a proof of invariance of either of the theories with respect to the reciprocity transformation would imply the formal equivalence of the two theories. Using the reciprocity relationship between the two theories, a recursion relation is derived for an nth-order term of the extinction-theorem perturbation theory (similar to the one for the Rayleigh–Rice perturbation theory). In spite of considerable effort, no general proof of invariance of the terms of the two perturbation series with respect to the reciprocity transformation was obtained. Two possible approaches to such a proof are suggested. While the question of convergence of the two series is not examined in this work, it is possible that the formulas derived here will prove useful in such a study.
Syllable recognition using hierarchical self-organizing maps.
Authors: Noda Hideki
Published: October 2005

A self-organizing neural network model that is able to learn and recognize temporal pattern sequences in speech such as syllables is described. This model has a hierarchical structure and consists of three parts: a feature-detecting part (feature map), a phoneme-detecting part (phoneme map), and a syllable-detecting part (syllable map). The feature-detecting part is composed of three feature maps which represent static, dynamic, and global feature of a short-time speech segment, respectively. The phoneme map is to identify a phonemelike unit to which each short-time segment belongs, using the response patterns of the three feature maps. The syllable map tries to recognize a time sequence of response units in the phoneme map as a syllable. The time sequence may be represented in a single map by superimposing the response pattern at time t on a decayed pattern of the pattern at t−1. It is shown that the proposed network can be self-organized using the Kohonen learning rule and it works reasonably through phoneme and syllable recognition experiments.
The energy spectrum of an impulse: Its relation to hearing loss
Authors: Hamernik Roger P. , Ahroon William A. , Hsueh Keng D.
Published: October 2005

Permanent threshold shifts obtained from 242 chinchillas that were exposed to various impulse noise paradigms have been related to the energy spectra of the impulses. The impulses were generated by three different shock tubes that produced impulse noise spectra whose A-weighted energies showed peaks at 0.25, 1, and 2 kHz. The results show that there is an increasing susceptibility to NIPTS as the audiometric test frequency increases from 0.5 to 16 kHz. This increase in susceptibility to NIPTS is further accentuated by approximately 5 to 10 dB for impulses whose spectra peak at 2 kHz.
Source location in thin plates using cross-correlation
Authors: Ziola Steven M. , Gorman Michael R.
Published: October 2005

In this paper an alternative method to first threshold crossing for acoustic emission (AE) source location is presented. For wave propagation in dispersive media, the accuracy of source location can be improved by locating corresponding phase points on the transducer outputs to determine the difference in arrival times. The phase point location was done by cross-correlating the transducer outputs with a single frequency cosine wave modulated by a Gaussian pulse. Experiments were performed using a lead break as the AE source on the surface of an aluminum plate. Due to the plate geometry and source orientation, the wave produced was highly dispersive. Although this wave was unsuitable for first threshold crossing techniques, the time differences needed for triangulation could be determined using the cross-correlation technique.
Final lengthening: Speaking rate effects.
Authors: Bell-Berti F. , Regan Sheila , Boyle Mary
Published: October 2005

Recent studies have revealed that although durations of sentences produced by a group of ataxic dysarthric subjects were significantly longer than those of a control group (sometimes twice as long), and that durations of segments occurring early in sentences were significantly longer in the speech of the dysarthric subjects, there was an absence of final lengthening [Bell-Berti etal., J. Acoust. Soc. Am. Suppl. 1 88, S128 (1990)]. One explanation offered for the lack of final lengthening is that the speech was already so slow (and the individual segments so long) that further lengthening was not possible. The present study of three normal speakers was undertaken to examine the possibility that the magnitude of the final lengthening is related to speaking rate and the extent of final lengthening. Indeed, at very slow rates, utterance-final segments may even be shorter than they would in sentence-medial positions. [Work supported by St. John’s University and NINDCD Grant DC-00121 to Haskins Laboratories.]
Estimating order-of-accuracy for numerical wave propagation solutions in heterogeneous media.
Authors: Fricke J. Robert
Published: October 2005

Solutions to heterogeneous media wave propagation problems are often computed using numerical methods. The accuracy of such solutions is affected not only by spatial and temporal discretization errors but also by errors associated with the source injection schemes, absorbing boundary conditions, and approximations to the heterogeneous media. This paper presents a methodology for estimating order-of-accuracy (OOA) for the overall numerical simulator. As the discretization intervals in space and time decrease, the solution computed using a consistent scheme approaches the analytic solution ever more closely. The methodology shows whether this, in fact, happens, and if so, the rate of convergence. The paradigm for estimating accuracy is based on an analytic Taylor series expansion of the exact solution. Since the analytic solution is not known, a reference solution computed using a fine grid is chosen as the benchmark against which coarser solutions are compared. The order-of-accuracy of a Lax–Wendroff finite difference scheme illustrates the method. Starting with the Taylor series paradigm, a numerical estimate of OOA is formulated using an errorenergyratio. While the underlying Lax–Wendroff difference scheme is second-order accurate in a homogeneous material, the numerical estimate of OOA for scattering from an ice edge shows that the convergence is superlinear, though not quadratic. The short fall in rate of convergence is attributed to heterogeneity, absorbing boundaries, added dissipation near internal boundaries, and source injection errors.
The importance of ‘‘temporal pattern’’ in traumatic impulse noise exposures
Authors: Danielson R. , Henderson D. , Gratton M. A. , Bianchi L. , Salvi R.
Published: October 2005

The equal energy hypothesis (EEH) was evaluated for impulse noise. Specifically, the experiments evaluated the importance of the temporal distribution of impulses; the trading relation between the number of impulses and peak level and the difference between continuous and impulse noise. Monaural chinchillas were exposed to one of seven conditions. Their hearing was evaluated before, immediately after, and 30 days after the exposure. Hair cell damage was reported in the form of a cochleogram. The experiments show that the EEH is more appropriate for low-level impulse (135-dB peak); for equal amounts of energy, 150-dB impulses produce more hearing loss and hair cell damage than 135-dB impulses; for equal amounts of energy, impulses presented in rapid bursts cause less damage than impulses presented at ‘‘1/s’’ and 50 μs. Pairs of impulses presented at ‘‘1/s’’ produce the largest amount of damage. The results are discussed in terms of implications for the EEH.