bluuebunny/crossref_metadata_2025 huggingface dataset:
Accounting for Doppler in moving ship tomography
Authors: Metzger Kurt , Birdsall Ted
Published: October 2005

The travel time measurements used in ocean acoustic tomography are based on the use of wideband waveforms. Because of this, the effects of source or receiver motion must be modeled as time compression/expansion and not as simple frequency shifts. Equivalent situations occur when there is a frequency error between the clocks used to generate an ocean acoustic tomography wideband signal and the clock used to digitize the associated reception, and when the clock used to digitize the reception is not “properly” matched to the structure of the transmitted waveform. The common thread is that you have uniformly spaced samples at one set of times but you really need them at a different uniform spacing at a different set of times. The obvious solution is to interpolate. This paper describes the effects of some simple interpolaton techniques on the processing of the wideband waveforms used in making ocean acoustic tomography travel time measurements.
Anomalous sound propagation influenced by Mediterranean water
Authors: Desaubies Yves
Published: October 2005

Sound propagation in the Northeast Atlantic is strongly influenced by the outflow of saline water from the Mediterranean. The resulting sound profiles are characterized by a double channel structure separated by an intermediate sound-speed maximum. A propagation experiment was conducted in 1988 in the Tage Abyssal plain over a 280-km path, with source and receiver placed in the deep channel. Supporting hydrographic data indicated that although the sound-speed perturbations with respect to some mean were not very large, significant variability combined with the particular profile shape gave rise to unusual propagation conditions. The problem of how to characterize the overall shape of the profile, the variability of the depth and magnitude of the intermediate maximum, and the presence of strong fine structure is considered in particular. Angle depth and angle time of arrival plots are useful as characterizations of the channel; it is shown how they are related to the phase integral. Range variability of the intermediate sound-speed maximum can lead to leaking from the deep to the shallow channel. In those conditions it is illusory to attempt to make range-dependent predictions of arrivals. Even range-independent predictions can be unstable. The fine structure is related to internal waves and to the double diffusive processes evident in the area. An attempt to quantify them is made and the effect of various degrees of smoothing on the profiles is evaluated. A tomography experiment is presently being conducted in the Bay of Biscay by SHOM and IFREMER. Some comments on the feasibility of tomography in this region will be made.
Acoustic reflectivity of marine sandy sediment: Effect of the shear modulus gradient
Authors: Hall Marshall V.
Published: October 2005

Acoustic propagation loss in shallow water is sensitive to the reflection coefficient (R) of the sediment to incident plane sound waves. Unconsolidated marine sediment is usually a heterogeneous solid medium; the SV and P displacement potentials do not in general satisfy separate wave equations. Determination of R therefore requires a fundamental analysis of the equations of elastic motion, which is achieved using Richards' method of weakly coupled potentials. Marine sand is modeled as a half-space in which density and the dilational Lame modulus (λ) are constant, whereas the shear modulus (μ) increases with depth in the manner prescribed by contact theory. Providing μ″ (0) = 0, quasi P and S potentials in the sediment satisfy (coupled) second-order linear differential equations. By requiring the displacement and stress to satisfy boundary conditions at the interface, an expression is derived for R that includes, among other things, the gradient μ′ (0) and the ratio Z(0)/Z′(0), where Z(z) is the quasi P potential function. In the Born approximation, this ratio is unaffected by coupling to or from the S wave. The resulting equation for Z is transformed into a Helmholtz equation that is solved by an approximate method. Results for R are presented over the frequency band from 10 to 100 Hz.
Field experiments to study seafloor seismoacoustic response
Authors: Stoll R. D. , Bryan G. M. , Mithal R. , Flood R.
Published: October 2005

Results of a 5-year program to measure the seismoacoustic properties of unlithified sediments in the seafloor are presented. A field technique utilizing a geophone array on the seafloor was used to obtain detailed travel-time curves, and a new signal source powered by electrically detonated, eight-gauge shotgun shells was used to focus energy into the bottom and eliminate much of the high-frequency water-borne noise that usually accompanies explosive sources. A variety of inversion techniques including slant stacking and cross multiplication were used to obtain dispersion curves and constrained least-squares inversion utilizing partial derivatives was employed to develop an iterative method to obtain velocity and attenuation as a function of depth. Data from a wide range of sediments ranging from soft Holocene mud to stiff overconsolidated clay are presented. The resulting geoacoustic models reflect the influence of the present overburden pressure and the geologic history, which largely determines the in situ porosity. [Work supported by ONR, Code 11250A.]
An adaptive tuning procedure for the psychophysical study of complex sounds
Authors: Wakefield Gregory H. , Chiang Chih-ming J.
Published: October 2005

Auditory object perception depends on the subjective criteria used by the observer to decompose an ambiguous acoustic field into auditory sources. Results from discrimination or detection experiments based on objective psychophysical procedures can only provide indirect evidence concerning the nature of the observer's source decomposition rules. Standard subjective psychophysical procedures provide direct evidence, but may be influenced by response bias and more importantly by experimenter bias in the choice of stimulus parameters to adjust. In the present paper, an adaptive tuning procedure is introduced which, unlike the method of adjustment, provides an efficient search over the stimulus space while minimizing experimenter bias in selecting that search space. The psychophysical procedure optimizes the stimulus parameter space according to a perceptual criterion adopted by the observer. It is claimed that inferences concerning the cues for source formation can be drawn from the values of the stimulus parameters to which the procedure converges. The procedure is applied to study the enhancement and degradation of single and multicomponent sinusoids in noise and to comodulated multicomponent sinusoids in noise to evaluate this claim. [Work supported by grants from the AFOSR (AFOSR-87-0193) and the NIH (NINDCD NS21440).]
Relative contributions of envelope maxima and minima to comodulation masking release (CMR)
Authors: Grose J. H. , Hall J. W.
Published: October 2005

Two studies have reported a negative CMR when the signal is presented only during the envelope maxima of the masker [Grose and Hall, J. Acoust. Soc. Am. 85, 1276–1284 (1989); Moore et al., J. Acoust. Soc. Am. 87, 1683–1694 (1990)]. However, another study has observed a positive CMR when the signal consists of the same noise band as the masker centered on the signal, resulting in a uniform increase in energy in both the maxima and the minima of the waveform [Hall and Grose, J. Acoust. Soc. Am. 84, 1669–1675 (1988)]. To investigate this apparent discrepancy, a series of experiments was undertaken to measure CMR as a function of the occurrence of the signal relative to the maxima and minima of the masker envelope. The signal consisted of either tone bursts or noise bands. The uniform finding was that a masking release was observed only when the signal resulted in an energy change during minima in the masker envelope. The implications of these results to proposed mechanisms of CMR will be discussed. [Research supported by AFOSR.]
Modulation detection interference: Interference for discriminating a change in the depth of amplitude modulation
Authors: Yost William A. , Sheft Stanley
Published: October 2005

Discrimination of a change in the depth of sinusoidal amplitude modulation of a sinusoidal probe carrier was measured in a modulation detection interference (MDI) paradigm (discrimination between [1 + mb cos(2πfmt)] [cos)2πfρt)] and [1 + mρ cos(2πfmt)] × [cos(2πfρt)], where mb = baseline depth of modulation; mρ = probe-tone modulation depth to be discriminated from mb; fm = amplitude modulation rate; and fc = carrier frequency). Three conditions were tested for each carrier frequency (1000 and 4000 Hz) and baseline depth (0%, 25%, 50%, 75%, and 100%): probe alone conditions depth discrimination was measured for the probe-tone carrier presented by itself; unmodulated masker condition—depth discrimination was measured for the probe-tone carrier when an unmodulated masker tone was simultaneously presented at the other tonal carrier frequency; and modulated masker condition—depth discrimination was measured when the masker tone was sinusoidally amplitude modulated at 100% depth and at the same rate (11, 20, or 32 Hz) as the probe tone. The depth of discrimination thresholds averaged over five listeners for both probe-tone carrier frequencies for all three modulation rates, and for both the probe alone and unmodulated masker conditions, was approximately the same and decreased as the baseline depth increased from 0% to 100%. However, depth discrimination thresholds increased dramatically for all modulated masker conditions that indicated significant modulation detection interference for depth discrimination as has been shown for modulation detection and modulation rate discrimination [Yost et al., J. Acoust. Soc. Am. 86, 2138–2147 (1989)]. The results will be discussed in terms of cross-spectral modulation interactions. [Work supported by NIDCD and AFOSR.]
An experimental study of the use of PVDF piezoelectric sensors in active structural acoustic approaches
Authors: Clark Robert L. , Fuller C. R.
Published: October 2005

An experimental investigation was performed to determine the feasibility of implementing polyvinylidene fluoride (PVDF) piezoelectric distributed sensors on the surface of a structure as error sensors in an adaptive lms control approach to minimize acoustic radiation. A simply supported rectangular plate was chosen as the test structure and was excited by a point-force steady-state harmonic disturbance. Structural inputs achieved by three piezoceramic actuators bonded to the surface of the panel. Two narrow strip PVDF sensors were positioned on the plate such that the dominant observed response was due to the odd modes (i.e., the more efficient radiators). The error sensors in effect act as spatial wavenumber filters and only observe those components that contribute significantly to far-field sound radiation. Both position and number of piezoceramic actuators were varied during the test to determine the effects on control performance. A variety of test cases was studied for controlling sound radiation due to a disturbance both on and off resonance. Results from these experiments indicate that PVDF sensors and piezoceramic actuators (i.e., an “intelligent” structure) show much promise for controlling acoustic radiation from structures, to a large degree overcoming the need for error microphones in the far field. [Work supported by ONR/DARPA.]
The effect of modal coupling characteristics on one mechanism of active noise control
Authors: Snyder Scott D. , Hansen Colin H.
Published: October 2005

When using vibration sources to actively control sound transmission into coupled enclosures, two physical control mechanisms are possible. The first is an increase in the input impedance of the primary coupled structural mode(s), which results in a decrease in their amplitude. The second is an alteration in the relative phasing and amplitudes of the coupled structural modes. The ability of this second mechanism to provide global sound control is greatly dependent upon the structural/acoustic coupling characteristics of the system. This dependency is demonstrated analytically by contrasting systems of differing coupling characteristics.
Active control of sound radiated from NITINOL-reinforced composite plates
Authors: Poh S. , Baz A. , Gilheany J.
Published: October 2005

Shape memory alloy (NITINOL) wires are embedded at the mid-plane of a fiberglass composite plate as means of controlling the sound radiated from the plate. Activation of the shape memory effect, by heating the wires beyond their martensitic transformation temperature, increases the strain energy of the plate which results in altering its characteristic response parameters, i.e., the modes and mode shapes. With proper activation strategies of the NITINOL fibers, a significant change in the radiation efficiency can be achieved. Experiments are conducted on a 23- ×23- ×0.156-cm fiberglass plate mounted on an anechoic chamber and subjected to broadband incident sound waves. The plate is reinforced by 33 NITINOL wires that are 0.055 cm in diameter. The effect of initial preload of the wires, as well as the number and location of activated wires on the modes and mode shapes of the plate, radiated sound pressure, directivity patterns, and transmission loss, is determined. The results obtained suggest the potential of this class of composite plates as a means of designing sound enclosures for critical applications. [Work supported under grant from ARO.]
The acoustic signatures of laboratory-generated bubble plumes
Authors: Kolaini Ali , Yi Mao , Roy Ron A. , Crum Lawrence A.
Published: October 2005

The results of laboratory experiments designed to characterize the underwater sound field radiated by a breaking wave are presented. Two general types of experiments were performed. First, progressive gravity waves were produced in a flume tank (2×2×12 ft; 7×7×6 ft) by a plunger wavemaker (wedge-shaped) at one end of the flume. Near the other end was placed an airfoil with a given angle of attack forcing gravity waves to break in the tank region. The second series of experiments involved the introduction of a jet of water, simulating a plunging breaker, onto the plane water surface of the tank. The water jet was produced by releasing a fixed volume of water, held in a cylindrical container, onto the surface. The jet characteristics were varied by changing the container's volume and height. The hydrodynamic characteristics of the bubble plumes generated by these two mechanisms were measured by using a high-speed video camera. The underwater acoustic emissions from these air entrainment processes were recorded simultaneously with the high-speed video camera and a digital oscilloscope that possessed a large memory. Concurrent video image, power spectrum, and observed time evolution of the bubble plumes generated by these two mechanisms reveal a dominant acoustic signal occurring at frequencies lower than 200 Hz. [Work supported by ONT.]
Collective oscillations in a bubble column: Higher modes
Authors: Nicholas Michael , Roy Ronald A. , Crum Lawrence A. , Prosperetti Andrea , Lu N. Q.
Published: October 2005

One possible source of ambient noise in the ocean is clouds of bubbles generated by a variety of mechanisms at the sea surface and extending down to depths of several meters [A. Prosperetti, J. Acoust. Soc. Am. 83, 1042–1054 (1988)]. Experimental evidence exists [Yoon et al., J. Acoust. Soc. Am. (1990)] that demonstrates that the sound generated by a cloud of bubbles is characteristic of the gross features of the cloud itself. From the analysis of underwater acoustic emissions of these “collective oscillations,” the numerous modes of vibration of a column of bubbles were studied, including a variety of boundary conditions, and these results compared against theoretical predictions. Because of the excellent agreement that exists between predicted and measured acoustic characteristics of the bubble-filled column, it appears that the theory for describing such collective oscillations is becoming firmly established. [Work supported by ONR and ONT.]
Piezoelectric transducers for the direct measurement of medial forces in the glottis
Authors: Reed Charles G. , Doherty E. Thomas , Shipp Thomas
Published: October 2005

A piezoelectric wafer was introduced between the vocal folds to acquire signals related to the medial forces present during phonatory and vegetative behaviors. A flexible fiber-optic laryngoscope was used to guide the transducer into the glottis and provide visual confirmation of its position. When comparing the acoustic and glottal signals from each sustained phonation, a close relationship can be observed during changes in intensity and in fundamental frequency. This report illustrates the feasibility of this technique. Figures showing traces of the signals from the force transducer and the microphone will be presented.
Low-frequency wind noise, origins, and vertical array effects
Authors: Carey William M.
Published: October 2005

Midbasin vertical array noise measurements located at the sound channel axis show a broadly peaked pedestal about the horizontal that has been attributed to downslope conversion of shipping noise [Wagstaff, J. Acoust. Soc. Am. 69 (1981)] in the Northern Hemisphere and wind-produced noise and the shallowing sound channel in the Southern Hemisphere [Bannister, J. Acoust. Soc. Am. 79 (1986)]. The production of noise by the wind at frequencies less than 500 Hz is shown to be largely due to breaking waves, to have a dipole characteristic, and to vary with the cube of the 10-m wind speed. Measurements and dimensional arguments show that noise will also vary with the type of sea state specrum, Richardson number, and the Reynolds number. Source level characteristics that are based on a distribution of surface dipoles and measured levels are used in calculations of the midbasin noise levels due to wind-produced noise and its interaction with range varying features. It is shown that for Northern Hemisphere water, the interaction of noise from ships and wind with slopes and sea mounts is the dominant cause of the broad pedestal along the horizontal. It is also shown that wind noise is an important contributor.
Ambient noise in the 200- to 300-Hz band in the Greenland Sea
Authors: Lynch James F. , Worcester Peter
Published: October 2005

As part of the Greenland Sea project, a six-mooring acoustic tomography array was deployed in the Greenland Sea from September 1988 to September 1989. Though the primary purpose of the hydrophone arrays on the moorings was to monitor the transmissions of the sources, these arrays also monitored ambient noise in the 200- to 300-Hz band. This was done just before and afer the transmissions, which were made every 4 h during the year. Each mooring had from four to six hydrophones, which allows some studies of vertical coherence, but is insufficient for beamforming studies due to grating lobes. As support for the tomography effort, year long time series of both wind stress and ice coverage were obtained, as well as numerous CTD surveys. This allows one to correlate noise levels against the two largest sources, ice and wind, as shipping traffic is negligible in this region. Correlation of the levels across the array is also of interest, as many large amplitude events do seem to span the array dimension (about 200 km). Of particular interest are two large events seen in the spring, one of which was connected to an “ice Odden” event; these may be connected to the formation of Greenland Sea deep water. [Work supported by ONR and NSF.]
Some work of Robert Bradford Newman Architectural Student Medalists—The first 5 years
Authors: Cavanaugh William J.
Published: October 2005

When MIT's and the Harvard Graduate School of Design's Professor Robert Newman died in 1983, architectural acoustics education lost perhaps its greatest evangelist. A group of his friends and colleagues throughout the acoustics community established the Robert Bradford Newman Student Fund to attempt to continue his work toward seeing that ultimately every student of architecture receives during their undergraduate or graduate training at least the fundamentals of this important architectural technology. In 1985, the first Newman Medals were awarded to graduating students at several universities for “merit in the study of architectural acoustics.” By the end of 1990, there will be over 35 participating architectural schools that offer not only a basic course in the discipline but opportunities for the students to apply this knowledge in their architectural design projects or theses. This paper reviews the range and breadth of work by Newman Medal recipients during the first 5 years of the program including some truly outstanding, and in several cases extraordinary efforts. The Newman Student Medal Program continues to expand and indeed seems to be well on its way toward fulfilling its objectives that incidentally compliment those of the Acoustical Society itself “to increase and diffuse knowledge of acoustics and promote its practical applications.”
Comparison of backscattered echoes predicted from exact theory and from thin-shell theories
Authors: Dean C. E. , Werby M. F.
Published: October 2005

It is not difficult to predict how sound scatters from a fluid-loaded elastic shell based on exact elastodynamic theory, provided the shell is a sphere or an infinite cylinder. Problems arise for more general shapes, however, and although some success has been obtained for spheroids and cylinders with hemispherical end caps, the results are rather tedious, if not disappointing, when one wishes to extend the frequency range or aspect ratio of the target. Some progress has been made for results predicted from thin-shell theories either utilizing finite-element methods in two and three dimensions or T matrices based on thin-shell theories. In this study, some common thin-shell theories that are employed for spherical elastic shells with exact normal mode theory are examined, with the goal of extending the results to elongated targets. Limitations of the various thin-shell theories are explored for both the frequency range and thickness.
Anomalies in the ray synthesis of backscattering from hollow elastic spherical shells
Authors: Kargl Steven O. , Marston Philip L.
Published: October 2005

When the form function for backscattering f(θ = πka) from a hollow spherical shell is described by a ray synthesis based on a generalized surface ray theory [P. L. Marston, J. Acoust. Soc. Am. 83, 25–37 (1988)], two anomalies occur in the vicinity of the first axial longitudinal resonance within the shell. The first anomaly is the manifestation of the longitudinal resonance and a ray synthesis of the specular reflection contribution fsp, which includes a novel curvature correction fcc, seems to properly describe one effect of longitudinal resonances on f [S. G. Kargl and P. L. Marston, J. Acoust. Soc. Am. 88, 1114–1122 (1990)]. The fundamental longitudinal resonance occurs at ka = πcL/[c(1 − b/a)], where k is the wave number of the incident wave, b/a is the inner-to-outer radii ratio of the shell, and cL and c are the longitudinal sound speed of the elastic material and speed of sound in water, respectively. The present ray synthesis contains leaky Lamb wave contributions that account for the circumnavigation of Lamb waves about the shell. The second anomaly occurs where the s1 leaky Lamb wave has a negative group velocity and is highly radiation damped. This occurs for ka slightly below that of the fundamental resonance. It is plausible that the second anomaly may be the result of a direct ray contribution not currently contained in the ray synthesis. [Work supported by ONR.]
Power spectra for noise in open and closed systems: 1/f noise versus the fluctuation-dissipation theorem
Authors: Putterman Seth
Published: October 2005

A great number of physical systems display power spectra that diverge in the limit of low frequency. This divergence that is approximately proportional to the inverse of the frequency f is referred to as 1/f noise. According to the second law of thermodynamics the power spectrum of a closed equilibrium system is determined by the fluctuation-dissipation relation. Except for the unusual case where the coefficient of diffusion is linear in f, the equilibrium power spectrum does not possess a region of 1/f noise. Therefore, 1/f noise is a manifestation of off-equilibrium dynamics. It is due to the dominance of high-order reversible nonlinear processes over the irreversible linear transport response.
Inherent noise of condenser measurement microphones
Authors: Frederiksen Erling
Published: October 2005

Condenser microhones are used for sound measurements in the band from a few millihertz to about 200 kHz. The lowest detectable level depends on the inherent noise of the microphone and the associated preamplifier. Several different microphone types and sizes (diameters) are available for sound measurements. For smaller microphones (1/8 in., 1/4 in.), the preamplifier noise sources are dominating while for larger microphones (1 in. and 1/2 in.) the Brownian movements of the microphone diaphragm make the main contribution to the system noise. The paper will discuss the noise sources of a microphone cartridge and of the radiation impedance, seen by its diaphragm, which together create the noise of the transducer. The state of art with respect to noise of microphone systems will be described. The overall inherent noise of traditional audio condenser microphone systems is 12–15 dB or about 0 dB for 1/3-octave bands. A low-noise principle, based on low damping of the microphone diaphragm, will be mentioned. The inherent noise of a system according to the principle is about 15 dB lower than that of traditional systems which makes it applicable to broadband measurements at levels as low as the threshold of hearing.
Thermal noise in piezoresistive silicon microphones
Authors: Kahng Seun K.
Published: October 2005

Recent developments in micromachining of silicon devices and piezoresistive silicon pressure sensors have led to the consideration of the limitations of silicon pressure sensors as a microphone. Fundamental and technological limits to device scaling are presented, which provide design criteria for sensitivity and pressure accuracy, along with dynamic range and bandwidth. An analysis on the nature of noise and fundamental noise mechanisms is presented to determine the theoretically achievable input resolution. Primary noise considerations are given with regard to thermal noise and shot effects. Performance variation of the sensor in both offset voltage and sensitivity is discussed as a function of temperature and impurity density of a standard bridge configuration. Finally, models of the various noise mechanisms are proposed.
Wideband measurements of thermal noise in condenser microphones
Authors: Zuckerwar Allan J. , Ngo Kim Chi T.
Published: October 2005

The thermal noise of condenser microphones was measured in an instrumentation system incorporating a novel vacuum-isolation vessel (see preceding abstract), at an isolation pressure of 10−5 Tort, and an FFT spectrum analyzer, covering a frequency band from 1 Hz to 25.6 kHz. The contributions to the thermal noise include the mechanical Johnson noise (due to the Brownian motion of air molecules impinging on the microphone membrane), preamplifier noise (1/f and 1/f2 components), and background noise from the analyzer itself. Measurements on a dummy microphone, having the same capacitance as the corresponding measurement microphone, permit the mechanical Johnson noise to be isolated. The experimental results are compared to a theoretical analysis by Tarnow [B&K Tech. Rev. 3-1972].
Chaotic resonance patterns in excitable media
Authors: Abraham Ralph H.
Published: October 2005

Fundamental regions of vibration in excitable media, such as air columns or elastic reeds, may become chaotic in certain domains of the control parameters. Neighboring regions of such chaotic motion then interact in a chaotic analog of resonance. Experiments with real fluids and with two-dimensional lattices of chaotic dynamical systems (in digital simulation with massively parallel processors) reveal highly organized space-time patterns of coherent behavior. These patterns of chaotic resonance are highly suggestive of mechanisms for sound production in wind and percussion instruments, for sound detection in the inner ear, and for sound-to-image transformations. [Work supported by NASA.]
Computer simulations and reality in clarinet tones
Authors: Brown Nicholas E. , Schumacher Robert T.
Published: October 2005

One goal of computer simulations of musical instrument oscillations is to produce oscillations that actually sound like the acoustic instrument being modeled. But for the simulation to aid in the understanding of the physics of the instrument, that model must correctly include the various physical processes that are essential to the oscillations over the pitch range of the instrument. The progress that has been made toward this goal using a clarinet mouthpiece attached to a cylindrical tube as a model system is assessed. The computer implementation of a clarinet model based on the pioneering work of Backus, Benade, and Worman is discussed. Included will be discussions of air flow through the reed aperture, reed modeling, and input impedance modeling. The establishment of criteria for gauging the success of a computer simulation will be emphasized, and some comparisons between the computer oscillations and the instrument being modeled, including particularly the characterization of fluctuations and aperiodicities present in acoustic instrument oscillations will be presented.
The effect of ultrasound on the ionic conductance across frog skin in the presence of free-radical scavengers
Authors: Dinno Mumtaz A. , Kennedy Wendy , Ingraham Robert , Idom Beau , Crum Lawrence
Published: October 2005

In a recent study, Dinno et al. [Ultrasound Meal. Biol. 15, 461–470 (1989).] reported that the increase in ionic conductance across frog skin is primarily due to effects of nonthermal origin. Cavitation was considered to be the major mechanism response for the change in the conductance. Since free radicals (FR), under certain conditions, are known to be generated during cavitation, it was decided to investigate the effect of ultrasound in the presence of free-radical scavengers (FRS). It was found that the presence of 5 mM of either vitamin C or cysteamine caused a significant block to the increase of ionic conductance induced by ultrasound. On the other hand, cystamine, which does not permeate into the cell as readily as the other two FRS, did not interfere as strongly with the action of ultrasound. On the basis of these results, the following indications are suggested: (1) The increase in ionic conductance in the presence of ultrasound is triggered by FR produced by cavitation and (2) in some as-yet-unknown way, secondary effects of cavitation are triggered within the interior of the cell. [Work supported by the NIH under Grant No. 5-RO1-CA-39374-05.]
Analysis of the ultrasonic beam produced by a wedge transducer
Authors: Breazeale M. A. , Du G. , Joharapurkar D.
Published: October 2005

Recently, the wedge transducer has found application in ultrasonic microscopy (J. D. N. Cheeke and L. Germain, IEEE Ultrasonics Symposium, Montreal, 1989). Since the resonance frequency of the wedge transducer varies with position, it is possible to sweep the ultrasonic beam by changing the driving frequency. A theoretical analysis is given of the diffraction pattern produced at a single frequency by a one-dimensional wedge transducer. The relation of resonance frequency with position is by no means linear, which means that the distribution of resonance frequency along the transducer is not symmetric about its center position. A linear relationship between beam frequency and position on the wedge is possible if one uses a curved back surface, however. The effect of the transducer edge on the diffraction pattern is noticeable even at frequencies at which the beam emerges near the center of the wedge. This result is confirmed by comparing with schlieren photographs. The implication of this observation for design of Gaussian transducers is considered. [Research supported by the Office of Naval Research.]
Relationship between hearing handicap inventory for the elderly (HHIE) and pattern of hearing aid utilization by elderly hearing-impaired listeners
Authors: Náběek Anna K. , Tucker Frances M.
Published: October 2005

The differences in perceived handicap among elderly who reported various degrees of hearing aid utilization were assessed. Three groups of 15 listeners each (mean age 74 years, similar mean hearing loss) were: (1) full-time hearing aid users, (2) part-time users, and (3) nonusers. The listeners responded to ten questions of the hearing handicap inventory for the elderly (HHIE) [B. E. Weinstein, ASHA, May, 41–45 (1986)] that quantifies self-perceived handicap. First, groups 1, 2, and 3 responded as if they were not wearing hearing aids. Group 1 assessed themselves as more handicapped than group 3, indicating that people who perceive themselves as handicapped are more likely to rely on hearing aids than people who perceive themselves as marginally handicapped. Second, groups 1 and 2 responded as if they were wearing hearing aids. The full-time users, but not the part-time users, assessed themselves as less handicapped in everyday functions when they wore hearing aids than when they did not wear their hearing aids. Apparently, the HHIE reflected the usefulness of hearing aids for the full-time users. These results will be discussed in reference to background noise levels tolerated by elderly hearing-impaired listeners. [Work supported by AARP Andrus Foundation.]
Broadband holographic reconstruction of the surface field on radiating structures
Authors: Sarkissian Angie
Published: October 2005

In near-field holography, the acoustic field is reconstructed on the surface of a radiating structure from measurements of pressure on a two-dimensional surface in its near field. Since the intensity of the acoustic field decreases away from the surface of the structure, evanescent modes exist that decay exponentially away from the surface, making this inverse problem ill-posed and limiting the resolution that can be attained on the surface. A reconstruction algorithm is implemented, with cogent examples, where at each frequency the surface field is expanded with a set of functions that separate the strongly evanescent field from the field that can be reconstructed. This algorithm is more suitable for broadband data than the singular value decomposition approach because it reduces computation time. The functions are the eigenfunctions of the operator that relates the surface pressure to its normal derivative at vanishing frequency. Defined for an arbitrary surface, the expansion will be the same as a normal-mode expansion for a surface with separable geometry.
Acoustic evaluation of vowels produced by hearing-impaired children
Authors: Fourakis Marios , Geers Ann , Russo Mary , Tobey Emily
Published: October 2005

Three hearing-impaired children were recorded as they attempted to produce monophthongal vowels of American English. Children were matched for age, hearing, and speech and language ability, yet differed in prosthetic devices (a cochlear implant, a tactile aid, or a conventional hearing aid). Children produced vowels with their respective prosthetic aid on and off during four recording sessions over a period of 15 months. Four repetitions of each vowel, in each aid condition, at each recording date were digitized at 20 kHz with 16-bit precision, analyzed using ILS, and formant tracks obtained_ Geometric means of F1 and F2 were used to represent each utterance in Koenig space. Mean Euclidean distance from the Peterson and Barney equivalent vowel for children [J. Acoust. Soc. Am. 24, 1562–1567 (1952)] was computed, along with the standard deviation, for each vowel set. It was predicted that, if a child's productions improved, either longitudinally or as a function of prosthetic device feedback, these distances, and standard deviations, would decrease. Preliminary results for the child with a cochlear implant indicate that these predictions were true for some vowels but not for others. These results will be compared to data from the children with tactile and conventional hearing aids. Conventional measures of variability, such as the ratio of standard deviation to mean formant frequency, will also be discussed and compared with the distance measures. [Work supported by NIDCD.]
Loudspeaker-to-listener distance: Effect on the phoneme identification scores of normal-hearing and hearing-impaired listeners
Authors: Johnson Carole E.
Published: October 2005

Loudspeaker-to-listener distance was assessed for consonant and vowel identification scores of ten adults with normal-hearing and ten adults with high-frequency hearing loss (i.e., pure-tone thresholds >25 dB HL at 2 kHz and higher) in a 415-m3 (18×7.2×3.2 m) lecture hall, with a T = 1.5s (average T at 500, 1000, and 2000 Hz), and an estimated critical distance of 3.3 m. Each listener was seated at two distances within the critical distance (1 and 2 m) and three distances beyond the critical distance (4, 8, and 15 m) at a 0-deg azimuth to the separation between two loudspeakers placed side-by-side. One loudspeaker presented a 25-item CVCV nonsense syllable test at 77 dBA at 1 m. The 20 listeners were tested at all five distances in two speech-to-noise ratio (S/N) conditions: (1) varied—in which the speech level decreased with distance in relation to a 45-dBA ambient noise level resulting in a + 32-dB S/N at 1 m to a + 23-dB S/N at 15 m, and (2) fixed—in which a multitalker babble was presented through the other loudspeaker and adjusted to maintain a + 15 dB S/N at all five distances. Scores were significantly better: (1) for normal-hearing listeners than for hearing-impaired listeners; and (2) in the varied S/N condition than in the fixed S/N condition. While vowel scores were not significantly affected by distance, consonant scores were significantly better within the critical distance than beyond the critical distance. Further, there was no significant decrease in consonant scores as loudspeaker-to-listener distance increased outside the critical distance.
Estimating the reliability of voice quality judgments: Comparing scales and statistics
Authors: Gerratt Bruce R. , Kreiman Jody , Kempster Gall , Erman Andrew
Published: October 2005

Because perceptual measures are the primary means of assessing voice quality in the clinic, the reliability of listeners' judgments is of central importance. However, there is no consensus regarding the stability of trained listeners' judgments under conditions that mimic actual clinical practice, or as to the best method for estimating the reliability of such judgments. The present research compares the reliability of experts' estimates of vocal roughness gathered using equal appearing interval and visual analog scales, in order to determine (1) whether one scale type is inherently more reliable than the other; (2) the most appropriate methods for estimating the reliability of voice rating data; and (3) how reliable listeners actually are when they rate voices using these scales. The advantages and drawbacks of the many statistics used to evaluate reliability data will be discussed, and recommendations for standardizing perceptual measurement procedures will be presented.
Adult perception of nonnative contrasts differing in assimilation to native phonological categories
Authors: Best Catherine T.
Published: October 2005

In cross-language speech research, adults often have difficulty discriminating non-native phoneme contrasts, although this difficulty is not universal nor is it necessarily permanent. Best et al. [J. Exp. Psychol.: Human Percept. Perf. 14, 345–360 (1988)] recently proposed that phonologically mature listeners assimilate nonnative contrasts to native phoneme(s), by four possible patterns: (1) Both phones assimilate to a single category (SC) and are difficult to discriminate; (2) they differ in category goodness (CG) and are discriminated relatively well; (3) they assimilate to two categories (TC) and are discriminated near ceiling; or (4) they are nonassimilable (NA) and are discriminated relatively well as nonspeech sounds. Those authors found evidence supporting their prediction of good discrimination for nonnative NA contrasts. The present research extended to predictions that TC contrasts would be discriminated better than CG contrasts, which, in turn, would be discriminated better if the goodness of fit to the relevant native phone is marked (strong CG contrast) than if the difference is subtle (weak CG contrast). Results were consistent with predictions, thus providing further support for the phonological assimilation model. Additionally, a recency effect in auditory memory was found only for the weak CG contrast. [Work supported by NIH Grants DC-00403 and HD-01994.]
Effects of spatially correlated auditory information on eye motor movements
Authors: Sadralodabai Toktam , Perrott David R.
Published: October 2005

The present study investigated the effects of spatially correlated auditory information on eye motor movements using a two-alternative forced-choice reaction time paradigm. A visual target (0.8 deg) was located at 1 of 17 locations along the horizontal and vertical axes in the frontal plane. The targets were positioned within 17 deg of visual angle relative to the point of fixation. These visual targets were presented alone or they were spatially correlated or uncorrelated with the auditory information (click train). Results indicate a significant three-way interaction between condition orientation (i.e., horizontal or vertical) and distance of visual target from fixation point [F(8,16) = 4.14, p < 0.01]. The implication of the results will be discussed
Designing speech recognition systems to accommodate user behavior
Authors: Jacobs T. E. , Prezas D. P. , Thomson D. L. , Wilpon J. G.
Published: October 2005

There are many potential applications for speaker-independent speech recognition in the telephone network. These include automation of operator services, custom calling feature selection, and call routing. For such applications, recognition under varying background noise levels and speaker characteristics is necessary. In addition, the behavior of untrained users requires the recognizer to be able to: (1) spot keywords embedded in extraneous speech; (2) identify a word as soon as it is spoken, rather than waiting until the end of the recognition window; and (3) determine whether or not the user has spoken a word in the recognition vocabulary. These issues are discussed in this paper in the framework of a hidden Markov model-based speech recognition system incorporated into the AT&T Intelligent Network in Spain. This system is AT&T's first application of speech recognition in the telephone network. A description of how the Spanish speech data used for training the recognizer were collected and tested for a range of user responses is given. The performance of the recognizer, incorporating a three-word vocabulary (“uno,” “dos,” and “tres”), has been evaluated on several thousand speech utterances and correctly recognizes over 98% of all user inputs.
Broadband mode decomposition
Authors: Kille R. , Yang T. C.
Published: October 2005

A method of mode decomposition by averaging over broadband components of impulse signals propagated over long ranges is investigated here for simulations and explosive data collected in the Arctic on a vertical array. This method is based on the assumption that cross-modal terms of the covariance matrix are minimized when averaging over broadband components of an impulse signal [C. S. Clay, “Array steering in a layered waveguide,” J. Acoust. Soc. Am. 33, 865–870 (1961)]. Analysis of simulated data shows that both the mode amplitudes and modal depth functions can be deduced using this method; accuracy depends on how each mode is sampled by the vertical array. This method is developed for the purpose of investigating the modal structure of reverberation returns from explosive signals in the CEAREX 89 experiment. [Work supported by ONR.]
Measurements of low-frequency seat dip attenuations
Authors: Bradley J. S.
Published: October 2005

The low-frequency attenuation of near-grazing incidence sound over audience seating was measured in a large mutlipurpose hall and over scale model seating in an anechoic room. The low-frequency attentuation minima are found to be predominantly related to the vertical angle of incidence of the sound. Octave band measurements in 11 concert halls show the influence of the seat dip attenuation to be related to the geometrical details of the halls and in particular to the average height of the hall and the stage. These measurements as well as measurements of a string bass showed that this phenomenon can have a very significant influence on low-frequency sound levels in auditoria.
Applying fuzzy set theory to the evaluation of concert halls
Authors: Wu Shuo-xian
Published: October 2005

The technique from fuzzy set theory was used in combining the values of several parameters to determine the overall evaluation of concert halls. The factor set was tentatively defined as F = {RT (or EDT), LE, [EDT′(f)], Vmax(10 log LE)}, where LE is lateral efficiency, EDT′(f)} = 1/3 [EDT (2000-Hz octave) − EDT (250-Hz octave)], and Vmax (10 log LE) denotes the maximum difference among 10 log LE values in a hall [V. L. Jordan, Apppl. Acoust. 14, 253–266 (1981)]. The evaluation set was defined as E = {excellent, good, acceptable, no good} and the test set was defined as T = {measurement under full condition, measurement under empty condition}. Weight assignation for the factor set and test set was made as WF = (Wf,, Wf,, Wf,, Wf,) = (0.4, 0.3, 0.15, 0.15) and WT = (Wt, Wt) = (0.6, 0.4). The membership function values matrix R, in which the entry rij represents the impact of ith factor upon jth evaluation rank, was constructed. Last, the overall evaluation vector S, in which the value of ith element denotes the possibility with which the hall would be evaluated to ith rank, was calculated by S = WF⋅R. As examples, ten halls quoted in Jordan's paper were evaluated by using this method.
Strong lateral low-frequency components reflection from canopy complex comprising triangle plates in concert halls
Authors: Nakajima Tatsumi , Ando Yoichi , Fujita Keisuke
Published: October 2005

By using the line integration along the edge of thin rigid plates, which is derived from the integral theorem of Helmholtz-Kirchhoff by Maggi-Rubinowicz transformation, the impulse response of triangle canopy panels of various shapes was calculated. The transfer function (TF) in the frequency domain is obtained by its fast Fourier transformation. Numerical calculations of TF showed that the optimum inner angle of the equilateral triangle, which gave a flat response extending to lower frequencies, was in the range of 95° to 115°. It is interesting to note that the canopy in Tanglewood Music Shed satisfies this optimum inner angle. The TF of small-sized triangle panels installed above the stage in FUJITA HALL 2000, a concert hall designed and constructed by our group, clearly indicates the strong lateral low-frequency components of reflections for the audience. The higher-frequency components of the reflection, however, are from the triangle panel complex suspended in front of the top of the proscenium arch. In this hall it was thus realized that both the lower-and higher-frequency components by reflection made the IACC values at the audio-frequency range low and uniformed expansion of the sound field better.