bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical considerations in laryngeal paralyses and their effect on laryngeal vibration
Authors: Smith Marshall E. , Gerratt Bruce R. , Berke Gerald S.
Published: October 2005

The neurologic causes of vocal fold paralyses have been well documented; however, the effect of these disorders on laryngeal vibration are not as well understood. Treatment of laryngeal paralysis with current surgical techniques (phonosurgery) also requires a knowledge of their effects on phonation. A theoretical model of the larynx, a four mass model based on the work of Ishizaka [J. Acoust. Soc. Am. 60, 1193–1198 (1976)] and Koizumi et al. [J. Acoust. Soc. Am. 82, 1179–1192 (1987)], was developed and adapted to simulate laryngeal biomechanical behavior, as understood by current research. The model was then applied to an evaluation of various states of asymmetric laryngeal vibration. Input parameters that correlate laryngeal function and model simulation were developed. Laryngeal paralyses were simulated by their predicted effect on these parameters. Simulations were compared with available data on glottal vibration in laryngeal paralyses. Complex modes of vibration were seen with certain combinations of asymmetric lower mass stiffness and initial glottal gap. The limitations of a lumped mass model of asymmetric laryngeal vibration are also discussed.
Acoustic and electroglottographic analyses of adductor spastic dysphonia speech
Authors: Owen Ann S. , Espinoza-Varas Blas , Parker Ebony
Published: October 2005

This paper describes acoustic and electroglottographic (EGG) analyses of utterances produced by adductor spastic dysphonia (SD) patients. The SD patients produced a set of monosyllabic words (e.g., boom, boot) at conversational, fast, and slow rates. The acoustic and EGG waves were tape recorded, digitized at 10 kHz, and stored on a computer disk. Using a waveform editor, measurements were obtained of (a) the amount of vocal cord vibration preceding the onset of the utterances (prevoicing); (b) the onset and duration of vocal cord spasms; (c) fundamental frequency; and (d) correlations between acoustic and EGG events. At the acoustic level, a wide range of abnormality was observed including utterances with periods of vocal cord spasm lasting several milliseconds and utterances with a significant amount of prevoiced activity. The acoustic abnormalities showed significant context effects; vocal cord spasms were most likely with syllables beginning and ending with voiced consonants. Correlations were observed between the acoustic events and the EGG waves. [Work supported by OCAST Grant HSO-005 and Presbyterian Health Foundation.]
Mid-ocean basin manifestation of continental margin downslope converted energy
Authors: Hodgkiss W. S.
Published: October 2005

In July 1989, the Marine Physical Laboratory carried out a downslope conversion experiment in the region of the continental margin NW of Pt. Conception, CA. These carefully controlled and well-documented measurements of downslope signal propagation were made to study the physics of downslope propagation, which has been suggested as one mechanism by which acoustic energy from surface sources such as storms and shipping traffic gets coupled into the sound channel [e.g., R. A. Wagstaff, J. Acoust. Soc. Am. 69, 1009–1004 (1981)]. At long distance, this downslope converted energy is seen as a large contribution to the ambient noise level arriving near the horizontal. This paper will discuss the downslope conversion experiment and will compare the observed vertical arrival structure from a source in deep water and a source traveling across the continental margin. [Work supported by ONR.]
Statistical properties of the sea surface sound dipole source
Authors: Kennedy Robert M.
Published: October 2005

A broadband measurement (40–4000 Hz) of the vertical directional spectrum of the underwater ambient acoustic field was made in an acoustically isolated area where the ambient is dominated by well-documented local sea conditions. Measurements, made over a 1-year period, sampled a wide range of sea conditions and made possible a statistical analysis of the effects of the sea surface condition on the acoustic field. Having the total directional spectrum, unperturbed by long-distance sources, allowed the partitioning of the measurement into multiple source types, each type distinguished by its unique vertical directional pattern. An important component of the sea-surface-generated radiation is a diffuse distribution of vertical dipole sources. A unique property of the present data analysis is that the dipole source strength “area density” is found by matching only that part of the total measured pressure field exhibiting a dipole pattern. This is accomplished by parametric spectral estmation procedures. The frequency spectrum of the dipole source strength is found to be a bandpass function whose parameters are statistically related to the wind-generated surface friction velocity. The results of the analysis contribute an important element to an accurate modeling of the space-time statistics of sea surface sound.
Measurements of the source level of ambient noise due to wind
Authors: Chapman N. Ross , Cornish James W.
Published: October 2005

Measurements of the source level of wind-generated ambient noise in the deep ocean are presented for the frequency band 10–350 Hz. The data were obtained using a vertical line array deployed in the deep sound channel at various sites in the Northeast Pacific. The array response was steered vertically upward to measure the local sea surface noise and eliminate distant shipping noise. The beamforming was carried out in the frequency domain using a Kaiser-Bessel window to reduce sidelobe levels. The beam power levels obtained were referenced to a source level at the sea surface using a simple propagation model. The estimated wind noise levels N were fitted to the wind speed v at a specific frequency using a model of the form N = A + 20 n log v. The data indicate two we!l-defined regions, with a weak wind-speed dependence at low wind speeds before wave breaking occurs and a stronger dependence at higher wind speeds. The values of n for wind speeds > 10 kn were in the range from 1.1–1.8. The source levels are compared with other measurements reported in the literature.
Acoustics, architecture, and speech: A student inquiry
Authors: Egan M. David , Lee Peter R.
Published: October 2005

A hands-on student project aimed at identifying an acoustics problem and correcting it was undertaken during a special 2-day period set aside by the Clemson University College of Architecture to encourage innovative learning methods. The exercise combined acoustics theory and problem definition with architectural design response and testing of the solution. The pastor of a local church was concerned that worshipers had difficulty hearing sermons. Examination of the sanctuary space revealed that speech intelligibility was being degraded by reverberation and long-delayed sound reflections. In situ experimentation led to the conclusion by students that a canopy could control sound emanating from the pulpit and effectively direct it toward the congregation. Following the exploration of alternate student designs, a final canopy model was constructed at full scale and placed over the pulpit for testing purposes. Before and after measurements with a portable meter measuring the speech transmission index [T. Houtgast and H. J. M. Steeneken, J. Acoust. Soc. Am. 77, 1069–1077 (1985)] revealed that listening conditions in the church improved significantly with the installation of the canopy. Similar findings emerged from surveys of church members conducted during the period of time the canopy remained in place.
Linking physical acoustics to musical acoustics: An aural demonstration for architectural students
Authors: Kinzey Bertram Y.
Published: October 2005

An appreciation of the contribution of room acoustics to the attributes of musical sound requires that architectural students first understand the harmonic sturcture of musical sounds in order to produce desired timbres and ensembles. A brief introduction to scale and chordal formation, consonance, and dissonance provides a foundation for a subsequent demonstration in which the terms, reverberation, clarity, balance, intimacy, etc., can be understood and appreciated. An effective introduction requires that it be an aural experience, and the organ is an excellent resource for the demonstration. An audio tape indicates the substance of the session as presented to students.
Buildings that sing
Authors: Bodine Willis
Published: October 2005

The influence of acoustical conditions in a performance space upon the design, composition, and aufführungsṕraxis of Western liturgical music was examined for correlations between architectural characteristics (volume; proportion; reverberation; selective absorption; placement of sound-producing elements; and liturgical purpose) and musical characteristics (performing resources; melodic and contrapuntal density; rate of harmonic change; intervalic consonance as derived from the harmonic series; timbre of solo, chorus, and instrumental sounds; and relative intelligibility of sung texts). Gregorian chant, melismatic organum, iso-rhythmic motets, Renaissance masses, Baroque cantatas and oratorio, 19th-century symphonic forms, and 20th-century compositions were studied in the context of the worship spaces and theological currents for which they were developed. The unique factor of vocal participation by the “listener” in the presentation of liturgical music in the Western tradition was heavily weighted [E. A. Sövik, The Hymn 41 (3), 10–14 (1990)], and the analogy of proportion between the geometry of Medieval worship buildings and the vertical harmonic structure of triads was explored [R. Lawlor, Parabola 3(1), 12–17 (1978)].
Acoustical models in the design studio
Authors: Siebein Gary W.
Published: October 2005

Acoustical model studies have been incorporated in graduate architectural design studios and elective courses. Recent studies have included modeling outdoor urban spaces in Chicago and Beijing; modeling the Thomas Center (an existing building on the National Register of Historic Places) to determine appropriate acoustical modifications to the building that would also satisfy the requirements of the historic preservation guidelines; and design alternatives to solve some of the acoustical problems in a barrel-vaulted lecture hall proposed for an actual building. The studio work has been shown to be an effective method to let students explore the interaction between applied acoustical design problems and general architectural design issues.
Outdoor-indoor noise reduction and outdoor noise
Authors: Segal Alexander
Published: October 2005

Two computer programs were used to demonstrate the relation between outdoor-indoor noise-level reduction and outdoor noise spectra. The first program (interior noise analysis or INA) estimates noise level inside a room exposed to any one of over 30 sources of exterior noise. The program allows the user to see the effect of a noise source location relative to a building facade and the effect of the method by which the outdoor noise level was defined. The second program (noise spectra mixer) estimates a composite 1/3-octave or octave-band noise-level spectrum attributable to several outdoor noise sources. The study revealed that the use of a composite noise spectrum can significantly simplify the process of the outdoor-indoor noise propagation analysis. However, the use of a composite noise spectrum when incidence angles of multiple outdoor noise sources differ may lead to incorrect results. Similar problems may occur when different techniques are used to define the outdoor noise levels. The programs' ability to demonstrate the above problems can be beneficial to education in acoustics.
Thermal noise in simple electrical and mechanical devices
Authors: Garrett S. L.
Published: October 2005

This presentation will provide an introduction to thermal noise as a process that limits the minimum detectable signal in a vibroacoustic sensor system. Starting with single degree-of-freedom systems, represented by a series RLC network and a damped simple harmonic oscillator, the equipartition theorem will be used to determine the mean-square value of the noisy variable. Consideration of the dissipative element will then lead to the concept of noise spectral densities and the general fluctuation/dissipation relations such as the well-known result for Johnson noise (v* = 4kBTR) in an electrical resistor. Generalization of this approach to three-dimensional systems with a quasicontinuous distribution of normal modes will illustrate the connection between thermal noise and traditional concepts of “blackbody radiation” and introduce the concept of a quantum limit to the “white” noise spectrum. These results will be applied to the calculation of minimum detectable signals in interferometric fiber-optic vibroacoustic sensors and compared to other noise sources such as receiver shot noise in the demodulator. [Work supported by the Naval Sea Systems Command and the Naval Postgraduate School Direct Funded Research Program.]
Comparisons of backscattering from cylindrical shells described by shell and elasticity theories
Authors: Radlinski Ronald P. , Vogelsong Richard D. , Dragonette Louis R.
Published: October 2005

For kah < 1, where k is the fluid wave number, a is the radius of the cylinder, and h is the wall thickness, scattering from infinite cylindrical shells at normal incidence can be described by a combination of specular reflection and the zeroth-order symmetric Lamb wave (S0). Thin-shell theory is found to closely describe the resonance behavior from this two-wave interaction. At higher values of kah, additional scattering from the antisymmetric Lamb modes above the plate coincidence frequency of the shell material is predicted by elasticity theory. For materials with longitudinal wave speeds greater than the fluid, and shear wave speeds less than for the fluid, no coincidence frequency is predicted by plate nor shell theory. Accordingly, backscattering from this class of materials described by shell theories, which include bending, show no evidence of the antisymmetric Lamb wave. For materials where both the compressional and shear wave speed are greater than the sound speed in fluid, the adequacy of the shell theory to describe the antisymmetric Lamb wave response is determined by comparison with full elasticity theory and with the results of Veksler and Korsunskii [J. Acoust. Soc. Am. 87, 943–962 (1990)].
Noise in piezoelectric sensors
Authors: Moffett Mark B. , Powers James M.
Published: October 2005

Piezoelectric sensor noise generation mechanisms will be reviewed. The sensor needs to be considered as part of a sensor-preamplifier system whose output signal-to-noise is to be maximized. When the preamplifier noise is dominant (as is often the case), an appropriate figure-of-merit for the piezoelectric sensor material is the gd product, where g and d are the appropriate piezoelectric coefficients, i.e., the signal-to-noise ratio produced by a given volume of piezoelectric sensor material is proportional to gd. On the other hand, if Johnson noise produced in the sensor resistance is dominant, the appropriate figure-of-merit is gd/tan δ, where δ is the dielectric loss angle of the piezoelectric sensor material, i.e., the sensor resistance is introduced via the tan δ factor. The figures-of-merit of a number of piezoelectric hydrophone materials will be compared.
The noise and detection limit of fiber-optic lever sensors
Authors: He Gang , Cuomo Frank W.
Published: October 2005

The noise mechanisms that limit the performance of optical fiber level sensors are presented. These noise sources can be characterized by those present in the optoelectronic detector as well as the random fluctuations of the sensing membrane. Based on a theoretical model, attention will be given to shot noise and thermal noise while the membrane motion under various temperature conditions will be analyzed. For the case of elevated temperatures and harsh environments, such as found in hypersonic wind tunnels, the blackbody radiation from the reflective membrane will also be evaluated. Depending on the sensor structure and the various parameters used, such radiation effects can significantly increase the shot noise at high temperatures. A comparison between the level of each noise source will be made and the sensor response, membrane displacement, and pressure detection limit will be considered. Finally, improved methods to increase sensor response will be discussed.
Vacuum-isolation vessel for measurement of thermal noise in microphones
Authors: Ngo Kim Chi T. , Zuckerwar Allan J.
Published: October 2005

In the past, the inherent electronic and thermal noise in a condenser microphone and the associated preamplifier were measured in facilities with poor acoustic isolation properties, especially at low frequencies where 1/fn (n = 1,2) noise sources are dominant. These background noise levels constitute one of the most important specifications of a microphone, for they determine the lowest sound pressure that can be detected. Therefore, a new method for measuring the thermal agitation noise within a bandwidth 1–25 000 Hz has been developed. The presentation will discuss the theoretical and experimental measurements of thermal agitation noise in a condenser microphone by using a high-vacuum isolation apparatus to achieve an acoustically quiet and vibration-free environment. The 1-in. condenser microphone is placed inside the isolation vessel where the pressure inside is atmospheric. The isolation vessel is suspended inside a larger vessel, in which the intervening air is evacuated. This method gives an accurate measurement of the inherent noise of the complete system. Measurements of sound propagation into the acoustic isolation vessel as a function of vacuum at different frequencies are compared to theory. The measurements are made at ambient temperature and at isolation pressures ranging from atmospheric down to about 5×10−6 Torr.
Thermal acoustic tomography
Authors: McNeil Roderick , Greif Robert , Collier Robert D.
Published: October 2005

Monitoring of furnace exit gas temperature is important for the efficient maintenance of operating parameters within utility boilers. Since gas temperature is related to the acoustic wave speed, a noninvasive technique based on transit time measurements along selected paths of known length can be used to develop an analytical model capable of predicting temperature within the gaseous medium. Integration of the resulting equations, after substitution of a Fourier series for the inverted sound speed, yields an exact inversion algorithm relating transit time, through the Fourier coefficients, to the medium's spatial temperature distribution [S. F. Green, J. Acoust. Soc. Am. 77, 759-763 (1985)]. Simulation utilizing the inversion algorithm with multiple transit time paths was performed to reproduce temperature fields of known magnitude. Matrix condition, through eigenvalue and noise perturbation analysis, and RMSSD error measurement indicated low tolerance for uniform sensor arrangements, and dependence on highly accurate, repeatable transit time measurements. Results also demonstrate the effect of increasing the number of transit time paths on matrix condition and path information content. A versatile scaled experimental configuration with 100-kHz transducers is described together with preliminary experimental data.
Computer simulation ofa Backus experiment on the trumpet
Authors: Dudley J. Duane , Strong William J.
Published: October 2005

Some time ago, John Backus developed an experiment to investigate harmonic generation in trumpet tones [J. Backus and T. C. Hundley, J. Acoust. Soc. Am. 49, 509–519 (1971)]. Incorporating Martin's conclusion that a player's lip opening varies almost sinusoidally [D. W. Martin, J. Acoust. Soc. Am. 13, 305–308 (1942)], he constructed a rectangular slit whose opening could be controlled by a sinusoidal driver. Attaching the slit to the mouthpiece of a trumpet and applying a constant blowing pressure, he then measured and analyzed the mouthpiece pressure as a function of time. The purpose of this paper is to report a computer simulation of that experiment, in which different parameters of the system are varied to assess their relative importance in the generation of tones. The effects of varying the slit dimensions, blowing pressure, and amount of closure occurring in each cycle will be examined, and curves will be shown to illustrate the slit opening, mouthpiece pressure, and input volume velocity as functions of time. The frequency dependence of the mouthpiece pressure response will also be discussed.
Analysis and resynthesis of the trumpet bore
Authors: Ayers R. Dean
Published: October 2005

Experimental studies of impulse responses in a trumpet bore have suggested a divide-and-conquer approach in which the contributions of the major elements (input end, uniform pipe, and output end) can be examined and understood separately. Multiple convolutions are then used to assemble these into the time-domain response (Green's function) of the complete instrument. The resynthesis is most easily understood for simpler structures in which the input end can be modeled adequately by lumped elements. Spatially extended input ends are handled by a more complicated formalism involving transmission impulse responses, but the spirit of the calculation is the same. Fourier transforming this work allows us to untangle partially the contributions of the major elements to the input impedance function of the complete instrument. [Work supported by a CSULB Summer Res. Grant and Equipment Grants from Hewlett-Packard. Special thanks are also due to Lowell J. Eliason for his long-term support of the experimental work and to William T. Cardwell, Jr. for our continuing dialogue on what is really happening in a trumpet's bore.]
Sound production in air-jet driven wind instruments
Authors: Keefe Douglas H. , Valeriu Ioana
Published: October 2005

Models of sound production in air jet-driven wind instruments are constructed in which the air-jet flow need not be small relative to the flow through the mouth of the organ flue pipe (or embouchure hole of the flute). This case is important for initial transients in wind instruments. The transverse flute differs from the organ in that the air jet interacts with two resonators rather than one, and this interaction is modeled using mass and momentum conservation to the mixing region of the air jet with the acoustical field. The linear system difference is most important. Separate reflection functions, defined in terms of pressure, are needed for the main body of the flute and the flute head joint volume. The dynamical system is expressed in terms of three first-order differential equations involving the air-jet flow, and the displacement and volume flow through the mouth. Transverse instabilities propagating along the jet are controlled by the current and time-delayed mouth displacement, the latter reflecting the wave speed of the instability across the mouth [N.H. Fletcher, J. Acoust. Soc. Am. 60, 926–936 (1976)], but our calculations are limited insofar as the frequency dependencies of the delay time and amplification factor of the transverse instability are neglected. Time domain simulations are well suited for investigating the relative importance of nonlinear flow and momentum injection mechanisms, and preliminary results will be discussed.
Uncertainties in noise criteria
Authors: Norris Thomas R. , Lukas Jerome S.
Published: October 2005

Clearly defined noise level criteria are needed to design an industrial facility efficiently. Many communities and states have regulations limiting noise levels, usually by land use category, but these limits are often ill defined or do not address sources of possible annoyance. For example, the operating and atmospheric conditions under which a limit must be met may not be defined. Also, it may not be clear if the limits apply to noise from trucks and trains, which are federally regulated, or the ambient noise level may already exceed the limit. Regulations based on existing ambient levels may not define how to determine the ambient, and acceptance of ambient levels may be delayed by regulators until after construction has started. Problems can arise even when all noise regulations are met, because courts or regulators may require additional noise control to alleviate complaints. Uncertainties in setting noise level criteria to respond to regulations are discussed and examples given.
Risks in licensing an industrial facility
Authors: Brittain Frank H.
Published: October 2005

During licensing and environmental assessment of an industrial facility, predicting, assessing, and planning to control noise are sometimes easy and sometimes difficult, but always important. Technical and economic risks are associated with licensing, primarily from insufficient attention to noise and from the many uncertainties and incomplete design information characteristic of a project's early stages. Unfortunately, these risks are often not apparent until financial commitments have been made or the plant begins operation. Even when the acoustical part of the licensing process is relatively easy, there may be major risks. Sources of major risks are identified and discussed, including uncertain criteria, lack of knowledgeable personnel, delays, difficulties in procuring sufficiently quiet equipment, effect of controls on plant design and operation, and costs. These risks are viewed from the perspectives of the design engineer, the client, and the public.
Case histories in licensing an industrial facility
Authors: Hoover Robert M.
Published: October 2005

In recent years, there has been a proliferation in the siting of small to moderate sized power-generating facilities in noise-sensitive communities. Some of these communities have little or no experience with industrial facilities and some have adverse experience. In many cases, this has led to noise-control requirements in the form of ordinances or licensing requirements that are overly strict. In addition, many of the personnel involved in the early development of plant budgeting, contracting, and conceptual design have little experience with technology for evaluating or controlling sound. Consequently, this has often led to inadequate attention to noise control requirements in the early stages of plant contracting and design. Several examples of noise-control problems frequently encountered in the licensing of these power generating facilities are described.
Large amplitude radial pulsations of a single, driven gas bubble: Comparison between theory and experiment
Authors: Gaitan D. Felipe , Crum Lawrence A. , Church Charles C. , Roy Ronald A.
Published: October 2005

In a previous paper [J. Acoust. Soc. Am. Suppl. 1 87, S141 (1990)], the observation of a single gas bubble pulsating radially and acoustically levitated in a stationary wave system at a pressure amplitude on the order of 1.5 bars with a relative pulsation amplitude Rmax/R0⩾3, was reported. This discovery was rather unexpected since the surface instability threshold under these conditions should have been on the order of 0.8 bars [S. Horsburgh, Ph.D. dissertation, University of Mississippi (1990)] and surface instabilities usually result in the break up of the bubble, preventing large radial pulsation amplitudes. The bubble was also observed to be undergoing sonoluminescence, a phenomenon in which light is emitted from the bubble, probably due to the high temperatures associated with the bubble collapse. In this paper, a comparison between the predicted and measured values of the pulsation amplitude, phase of collapse (radial minimum), and the number of radial minima per acoustic period will be presented. The theoretical calculations were made using three of the most current formulations of bubble dynamics, two of which include the energy and mass conservation equations of the gas inside the bubble to evaluate the dynamic temperatures and pressures. The experimental results have been used to test the applicability of these theories. In addition, the pressure amplitude threshold for light emission measured during the experiments has been used to determine the theoretical minimum temperature necessary to generate sonoluminescence. Comparison with previously measured temperatures inside cavitation bubbles during sonoluminescence activity will be made. [Work supported by ONR.]
The effect of extracorporeal shock wave lithotripsy (ESWL) on electrophysiological parameters across abdominal frog skin: Real time observations
Authors: Dinno Mumtaz A. , Kennedy Wendy , Crum Lawrence A. , Church Charles C.
Published: October 2005

The side effects of ESWL, such as increased sodium excretion and proteinuria, may be explained by structural and functional changes that lead to an increase in permeability across the renal tubule. This preliminary study was undertaken to examine the feasibilty of such an explanation. Frog skin was used in this investigation, since sodium transport across it is similar to that of the distal convoluted tubule in the kidney. Exposure of the skin to a single shock at 20-kV electrode voltage caused a significant but reversible decrease in transepithelial membrane potential, a decrease in ionic current (primarily sodium), and an increase in total ionic permeability. It is of interest to note here that these results are similar to those reported by Dinno et al. [Ultrasound Med. Biol. 15, 461–470 (1989)] on the effect of therapeutic ultrasound (1 MHz, 60–480 mW/cm2) on frog skin. Those similarities suggest a common mechanism. On the basis of this observation and other unpublished results, acoustic cavitation, and consequent free radical formation, seem to be an important factor contributing to the observed side effects. [Work supported by NIH under Grant No. 5-RO1-CA-39374-05. We gratefully acknowledge Dornier for making available their experimental lithotripter.]
Measurements of ultrasonic pulse arrival time differences produced by abdominal wall specimens
Authors: Sumino Yoichi , Waag Robert C.
Published: October 2005

The influence of propagation medium inhomogeneities on pulsatile ultrasonic fields has been investigated experimentally. The study employed a special curved transducer to produce a hemispherical wave pulse and a linear array to measure the resulting field along a line in a plane. Translation of the array in the elevation direction yielded data over a two-dimensional aperture. Time delay across the aperture was calculated by adding delay differences obtained by crosscorrelating signals on adjacent elements and noting the position of the crosscorrelation peaks. Received waveforms were shifted an amount given by the difference between the actual arrival time and a calculated geometric delay to isolate arrival time differences due to propagation path inhomogeneities. Waveform and time delay difference plots, as well as histograms and statistics derived from them for propagation through a water path and for propagation through five specimens of human abdominal wall, indicate that arrival time fluctuations in the presence of human abdominal wall specimens are significantly greater than for a water path, and that degradation in focusing through human abdominal wall can be expected in ultrasonic imaging systems that operate in the low megahertz range and employ a relatively large aperture.
Phase relations in ultrasonic light diffraction spectra
Authors: Sliwinski A.
Published: October 2005

In the phenomenon of light diffraction by ultrasound, the light intensity distribution in diffracted spectra depends on the power, frequency, and the width of the ultrasonic wave. It is known that, due to these dependences, the output light in given diffraction orders is modulated in phase. In the paper, some interesting relations are examined against ultrasonic power in the case of a single ultrasonic beam, as well as for two adjacent beams of various frequency ratios (in MHz range) that were experimentally observed and adequate numerical calculations were verified.
Acoustical tweezers: Its principles and applications
Authors: Wu Junru
Published: October 2005

A stable force potential well was generated by two collimated focused ultrasonic (3.5-MHz) beams propagating along opposite directions. Latex particles (270 μm in diameter) and clusters of frog eggs were trapped in the potential well. The trapped object can be moved axially or laterally by moving one of the PZT focusing transducers that generate the ultrasonic focused beams. The axial position of the trapped object can also be maneuvered by tuning the frequency of the electrical voltage applied on the transducers. [Work supported by NIH HL45161.]
Transient response of the line parametric array with arbitrary taper
Authors: Westervelt Peter J.
Published: October 2005

The pressure impulse response of an array with arbitrary taper τ(y′) is shown to be P = βE(4πa)−1[ψeτ(x0 − R0)].00 in which ψc = a(x0 − x1)−1θ(x0 − R) [see Eq. (6), in P. J. Westervelt, Acta Phys. Pol. 27, 831–841 (1965)], β is the coefficient of nonlinearity, and E is the impulse energy. Applied to the truncated array of length L with a square wave input of duration T, it can be shown, by methods similar to those used by Westervelt [P. J. Westervelt, JETP Lett. 4, 225–228 (1965)], that the far-field pressure is given by P = βE(8πR0cT sin2 φ){δ(x0 − R0) − δ(x0 − R0 − cT) − δ[x0 − R0 − L(1 − cos φ)] + δ[x0 − R0 − L(1 − cos φ) − cT]}, in which R0 is the length of the vector from the transducer to the field point, L is the length of the vector from the transducer to the absorber, φ is the angle between R0 and L, and E is the energy of the square wave.
Novel electromagnetic generation of subsonic waves on a membrane and a wave-number-selective differential optical detector
Authors: Matula Thomas J. , Marston Philip L.
Published: October 2005

Associated with a subsonic disturbance of a plane surface is an evanescent wave in the surrounding fluid. There has been interest in techniques for generating such disturbances [D. H. Trivett et al., J. Acoust. Soc. Am. 87, 2535<2540 (1990)]. An electromagnetic generator of subsonic waves on an electrically conducting layer is described. The method was used to generate waves having a velocity cm≈62 m/s on an aluminized Mylar membrane in air. A meander line (a serpentine coil) is driven by a tone burst of current. The plane of the meander line is parallel to that of the Mylar with a distance b between the center of adjacent lines. A spatially and temporally oscillating Lorentz force is generated on the membrane with the application of a current pulse across the aluminized Mylar simultaneous to the tone burst. Selection of the burst frequency f to be cm/2b, maximizes the amplitude of the tone burst launched on the membrane. Unlike conventional EMAT sources, no permanent magnets were used. The propagating membrane wave was detected by reflecting (off the membrane) a laser beam into a knife-edge photodetector. A modified wave-number-selective knife-edge detector was also demonstrated, which made use of a retroreflective prism. The modification is designed to reduce the sensitivity to background low-frequency vibrations. [Work supported by ONR.]
Studies of various electrode configurations for a plasma sound source
Authors: Cook Jeffrey A. , Thepsoumane Sirian , Gleeson Austin , Rogers Robert
Published: October 2005

Several different types of electrode configurations, including gap, exploding-wire, and various others, have been studied in an attempt to garner better understanding of the mechanisms by which acoustic pulses are generated. It is hoped that this research will allow the shaping of these acoustic pulses for specific applications and yield a repeatable broadband sound source. To this end, current, voltage, and acoustic data have been taken for each electrode firing, and a high-speed photographic record made of selective firings to increase understanding of the hydrodynamical properties of the spark-induced bubble. Relations have been studied between such parameters as breakdown time, energy at breakdown, and energy delivered in the acoustic pulse, in the hope of characterizing various electrode types by easily measured criteria.
Assessment of a directional microphone array for the hard-of-hearing
Authors: Soede W. , Bilsen F. A. , Berkhout A. J.
Published: October 2005

Hard-of-hearing people often have great difficulty to understand speech in surroundings with background noise. A directional hearing aid might be beneficial in improving the effective signal-to-noise ratio. Based on array techniques, two microphone models were developed with strongly directional characteristics. Particular emphasis was given to optimization and stability. Free-field simulations show that an average directivity index of about 9 dB can be obtained. The simulations were verified with free-field measurements on two portable models. The influence of the human head on the performance of the microphone arrays was measured with help era KEMAR manikin. In a diffuse sound field, an improvement of the signal to noise ratio with 7 dB was obtained. For the clinical assessment, an experimental setup was made in a sound insulated listening room with one (speech) loudspeaker in front of the hearing impaired subject and eight loudspeakers placed on the edges of a cube producing a nearly diffuse background noise. The SRT in noise for simple Dutch sentences was determined with a single omnidirectional microphone and with one of the microphone arrays. The results of the listening tests with 46 hearing-impaired subjects show an average improvement of the S/N ratio of more than 6.5 dB for monaural fitting.
Elastic wave scattering from large linear arrays of bounded obstacles
Authors: Lim Raymond , Hackman Roger H.
Published: October 2005

At a previous meeting of the Society [R. Lim and R. H. Hackman, J. Acoust. Soc. Am. Suppl. 1 87, S40 (1990)], an improved transition matrix formulation for multiple scattering calculations was suggested, capable of exact numerical results at low to moderate ka. Exact results for acoustic scattering from finite linear arrays of up to ten spherical shells were presented. In the far field, comparisons with the field due to truncated infinite arrays showed remarkable agreement. Hence it is possible to approximate the acoustic far field due to moderate to large finite groups of scatterers with fast calculations involving infinite arrays. In this presentation, results for the scattering from finite and infinite linear arrays imbedded in elastic hosts will be given. Here the strong coupling, possibly due to the host's shear degrees of the freedom, causes end effects to be more important. Energy cross sections for both compressional and shear wave incidence are presented and discussed.
Complex resonance frequencies in acoustic wave scattering from impenetrable spheres and elongated objects
Authors: Bao X. L. , Überall Herbert
Published: October 2005

Complex resonance frequencies of impenetrable (rigid or soft) elongated objects, namely, spheroids and cylinders with hemispherical endcaps, including the spherical limit of the latter, are studied. Complex resonance frequencies are obtained from the principle of phase matching of surface waves. Substantial differences are found between the two mentioned objects, and are explained physically. For the case where the surface waves are generated by plane acoustic waves at broadside incidence, the simultaneous presence of cylindrical circumferential-wave resonances and of the resonances of meridionally propagating surface waves is discussed; this effect is also known from the observation of elastic surface wave resonances on hemispherically endcapped elastic cylinders (G. Maze and J. Ripoche).
Analysis and comparison of three-dimensional angular distributions of rigid, soft, and elastic spheroidal targets
Authors: George J. , Werby M. F.
Published: October 2005

Three-dimensional angular distributions are calculated for rigid, soft, and elastic spheroidal targets. The elastic targets also include resonance locations and the results of the predictions of the three classes of targets are compared at both resonance values (for the elastic target) and non-resonance values. Both similarities and differences of the patterns are outlined over a broad frequency range and explained.
Observations of transverse cusp diffraction catastrophes produced by reflecting long and short ultrasonic bursts from a curved metal surface in water
Authors: Frederickson Carl K. , Marston Philip L.
Published: October 2005

Transverse cusp caustics are predicted to be produced when sound or light from a point source is reflected by a smooth curved surface having the general shape h(x,y) = h1x2 + h2xy2 + h3y2 + h4x + h5y (with h2≠0) [P. L. Marston, in Acoustical Imaging (Plenum, New York, 1988), Vol. 16, p. 579]. The transverse cusp curve partitions space into regions where either one or three rays contribute to the wave field. The diffraction pattern exhibited by a cusp caustic is proportional to the Pearcey function. Experiments were conducted that produced a transverse cusp using a focused source of 1-MHz sound and a smooth curved metal surface as a reflector. The shape of the reflector was measured to determine the parameters in h(x,y) for that particular surface. Long tone bursts were used to simulate a steady-state signal in order to image the acoustical wave field in a plane distant from the reflector. Experimental and calculated diffraction patterns are in fair agreement when the measured values of h1 and h2 were used in the calculation. Single-cycle bursts were used to show the transition from the three-ray to the one-ray region across the cusp curve. Temporal records manifest the transition expected for slices through the imaged wave field. An optical source and receiver replaced the acoustical source and receiver to image the corresponding optical wave field. A distinct optical cusp curve was visible as expected for the short wavelength limit. [Work supported by ONR.]
Temporal masking and the intelligibility of compressed noisy speech
Authors: Haas Gustav F.
Published: October 2005

Speech in noise is considered as a series of intervals containing, alternately, speech plus noise and noise only. While compression amplification cannot change the simultaneous masking effect of noise during a speech-plus-noise interval, forward and backward masking from adjacent noise-only intervals can be expected to affect intelligibility. This effect is seen as crucially dependent on attack and release times compared to the length of speech intervals and speech pauses, respectively. Attempts at quantitative solutions using temporal masking data are shown to be invalid but qualitative statements are made and compared to the literature on experimental compression/expansion schemes. Conflicting design requirements call for short release times to obtain benefits of “syllabic compression” in quiet, but for long release times to minimize noise interference.
Hearing acoustic details of speech. I. Level discrimination of stop-consonant noise bursts
Authors: Espinoza-Varas Blas , Jessee Tina , Cheung John Y.
Published: October 2005

In this series of experiments, listeners' abilities to detect and discriminate acoustic details of syllables and words are measured. This paper examines the discrimination of increments in the rms level of either the /k/ or the /t/ noise-burst of the word “cat” (/kæt/). A token of /kæt/ produced by a female talker was digitized at 20 kHz, output via a D/A converter, and presented on each interval of a 2IFC task. For one of the observation intervals, the noise-burst sample points were multiplied by (1 + k), 0.05⩽k⩽1.25 [Forrest and Green, J. Acoust. Soc. Am. 82, 1933–1943 (1987)] to obtain rms-level increments ranging from 0.4–7.0 dB. Normal-hearing listeners were instructed to select the interval that contained the louder burst. Level discrimination was studied: (a) for noise-bursts excerpted from the word and presented in isolation (“non-speech” condition); and (b) for the same bursts presented in word context (“speech” condition). Overall noise-burst power was ∼60 dB in both conditions. Discrimination thresholds [P(c) = 75] were interpolated from maximum-likelihood ratio probits fitted to 9-point psychometric functions. Thresholds in isolation expressed as 20 log (1 + k) were about 1.0 dB for both the /k/ and /t/ bursts. Thresholds in word context were higher than in isolation. Worst performance was obtained with the /t/ burst in word context. [Work supported by OCAST Grant HSO-005 and Presbyterian Health Foundation.]
Hearing acoustic details of speech. III. Discrimination of fricative duration
Authors: Boyle Timothy A. , Espinoza-Varas Bias
Published: October 2005

Listeners' ability to dicriminate the duration of the frication noise in the syllable /t∫a/ was measured. An 842-ms token of /t∫a/ produced by a female talker was digitized at 20 kHz, output via a D/A converter and presented on each interval of a 2IFC task. On each trial, one of the intervals contained a 5–35-ms decrement in the duration of the 183-ms frication noise. Duration decrements were obtained by removing segments from the temporal center of the noise. Normal-hearing listeners decided whether the first or the second interval contained the shorter-duration frication noise. Duration discrimination was studied for frication noise presented in isolation and in syllabic context. Duration-discrimination thresholds [P(c) = 75] were interpolated from probits fitted to 7-point psychometric functions. On the average, thresholds in isolation were ∼14 ms or ∼8% of the duration of the frication noise. Thresholds in context were ∼32.0 ms or ∼18% of the fricative duration. Although larger than in isolation, thresholds in context are smaller than 8% of the overall syllable duration. [Work supported by OCAST Grant HSO-005 and Presbyterian Health Foundation.]
Conformal generalized near-field acoustic holography: Theory and algorithm
Authors: Borgiotti Giorgio V.
Published: October 2005

The normal velocity field on the boundary σ of a radiating source is reconstructed with high resolution by using pressure data, measured in the very near field to include evanescent components. The measurement points belong to a surface conformal to σ. The reconstruction is performed by identifying the boundary normal velocity distribution generating the pressure field best mean square fitting the measurement data. The ensuing normal equations are solved by resorting to the singular value decomposition (SVD) of the discretized transformation from the boundary normal velocity to the pressure at the measurement points. The reconstruction boundary normal velocity is represented as a linear combination of basis functions, each associated with a singular value (SV). The errors in the estimation of the coefficients of the linear combination are proportional to the inverses of the corresponding SVs. To achieve robustness, the SVD is truncated to retain the terms corresponding to a limited dynamic range of the SVs. From the normal velocity on σ, the boundary pressure and the intensity field are identified, so that the energy flow from the structure can be studied.