bluuebunny/crossref_metadata_2025 huggingface dataset:
Age as a factor in the perception of temporal information in speech
Authors: Price P. J. , Simon H. J.
Published: October 2005

Many older people have greater difficulty processing speech at suprathreshold levels than can be explained by audiometric configurations. Some of the difficulty may involve temporal information. This information can cue “rapid” versus "“rabid” longer first vowel and shorter silent closure cue “rabid”; shorter vowel and longer silence cue “rapid.” Productions of “rabid” were low-pass filtered at 3500 Hz, and edited to create vowel and closure duration continua. Pure tone audiograms and speech discrimination scores were used to select the ten best hearing subjects among 50 volunteers over age 55. Randomizations of the stimuli were presented for labeling to this group, and to ten normal hearing volunteers under age 25 at 60 and 80 dB HL. Results show highly significant interactions of age with the other factors. These data indicate that the use of temporal information could be more fully exploited in audiological evaluations, and that age may affect which cues are used by a given subject in speech perception. [Work supported by NIH and by VA RER&D.]
A thermal microstructure measurement system (TMMS) to support high-frequency acoustic experiments
Authors: Posey J. W. , Levenson C. , Branch G. H. , Carver M. J.
Published: October 2005

A microprocessor-based, high-resolution thermal microstructure measurement system (TMMS) has been developed and tested which provides near real time at sea measurements of temperature, conductivity, depth, and current direction. The system has been developed in support of the Naval Ocean Research and Development Activity High-Frequency Acoustic Program [cf. J. W. Posey and C. Levenson, J. Acoust. Soc. Am. Suppl. 1 72, S60 (1982)]. Spatial correlations of temperature and conductivity fluctuations obtainable from TMMS measurements are required for the prediction of fluctuations of high-frequency acoustic signals. The array consists of a cross braced 2.3×2.3 m frame designed to orient itself normal to existing currents with 15-cm fixed sensor positioning bars protruding from the cross bars. Twelve matched thermistors, two conductivity probes, and a recording inclinometer are mounted on the frame. A compass and pressure transducer are contained in an electronics package suspended below the array. The array is deployed on a taut mooring below a subsurface float which effectively decouples it from surface perturbations. Data are serially digitized in the electronics package, transmitted on four conductor kevlar cables to a surface buoy and then transmitted via a VHF-FM radio link to a shipboard control console. Digitally available data are selectively displayed on a printer/plotter. Planned upgrading includes more rugged thermistors with closer tolerances and a digital inclinometer system. [Work supported by NORDA.]
List equivalency among five Tennessee Tonality Test lists: A preliminary investigation
Authors: Koike Kazunari J. M. , Brown Beth , Hobbs Harriet , Asp Carl W.
Published: October 2005

The Tennessee Tonality Test (TTT) is a speech discrimination test which has frequency selectivity in the test words rather than the commonly used phonetical balance of the test words. It was assumed that frequency selectivity in the test words could be achieved by dividing them into the low, mid, and high categories based on the pitch of the words which was termed “tonality.” The TTT was administered to seven normal hearing (23 to 32 years old) and seven hearing-impaired adults (20 to 70 years old). The subject was asked to repeat each prerecorded word which was presented at the subject's MCL and the tester wrote down the response. The criterion measure was the percentage correct of the test words correctly repeated among the total of 30 words in each list. The results indicated that there were no significant differences among the mean tonality scores of the five different lists for normal hearing and for hearing impaired adults. The need for future studies will be discussed. [Work supported by NIHR.]
Tonal confusions in Thai listeners with sensorineural hearing loss
Authors: Carney A. E. , Gandour J. T.
Published: October 2005

In this experiment, native Thai speakers with sensorineural hearing losses identified both natural and synthetic tokens of five contrastive lexical Thai tones, traditionally labeled: mid, low, falling, high, and rising. All hearing-impaired subjects had essentially flat losses, and were grouped by degree of hearing loss into mild-, moderate-, and severe-hearing loss categories. Identification data from these subjects were compared to those obtained from normal-hearing Thai listeners. Results indicated that the accuracy of identification decreased with severity of hearing loss in an orderly manner for both natural and synthetic tokens. However, error rates were much higher for synthetic stimuli across all subject groups. For natural tokens, tonal confusions from subjects with mild and moderate losses were similar to those from normal listeners; listeners with severe losses had a qualitatively different pattern of errors. In contrast, for synthetic tokens, tonal confusions from all hearing-impaired subjects differed from those made by normal listeners both qualitatively and quantitatively. Results will be discussed with respect to the nature of the acoustic cues needed by hearing-impaired listeners for intonation perception.
Voice fundamental frequency training of hearing-impaired speakers by visual feedback
Authors: Mahshie James , Hasegawa Akira , Mars Marguerite , Herbert Eugene , Brandt Fred
Published: October 2005

The real-time fundamental frequency (f0) extraction/display system described by Hasegawa et al. at this meeting (Paper NN8) is currently being used to provide visual feedback in an f0 training program with hearing-impaired adolescents/adults. An assessment protocol, utilizing displays of: f0 distribution, f0 contours, and f0 levels, determines the appropriate entry point for each subject into training. Systematic instruction has been developed using the f0 extraction/display system and focuses on both nonlinguistic and linguistic tasks. These tasks include: increasing and shifting the range of f0; development of appropriate tone groups; development of various pitch contours used in English; and instruction concerning English intonation rules. The rate and extent of f0 modification by subjects in the present program will be discussed, along with indications of the value and limitation of a single parameter system for modification of hearing-impaired speakers vocal behavior. [Work is supported by the National Institute of Handicapped Research and the Gallaudet Research Institute].
Acoustical features and cognitive features of stuttered speech: Their correlates and implications for management
Authors: Agnello Joseph G.
Published: October 2005

Data obtained from well over 100 stutterers pertaining to acoustical features (voice onset, co-articulatory patterns, F-patterns, pitch contours, and temporal features of phrasing) will be reviewed. Further, data obtained on attitudes and other cognitive aspects will be related to the acoustical (descriptive) features and implications for management. In the management discussion a device (microprocessor) for training stutterers to hit idealized speech onset targets will be presented.
Localization of sounds and targets in air and water by echolocating animals
Authors: Simmons James A.
Published: October 2005

Mammals that use echolocation, or biological sonar, to perceive the locations of objects in their environments have unusually acute capacities for localizing sound (echo) sources and for perceiving reverberation since they rely upon echolocation for spatial perception. Both bats in air and porpoises in water determine the distance to targets from the arrival time of echoes. The sonar signals which they emit are directional, with the possibility that porpoises may transmit different waveforms as well as different signal amplitudes in different directions. The hearing of echolocating animals is also directional, with reception through the external-ear system in bats and through the lower jawbone in porpoises. Directional hearing provides binaural cues for horizontal localization of targets. In bats, the external ear has directional amplitude and phase responses which the bat uses for vertical localization of targets. In porpoises it is possible that the transmitted waveform contributes to vertical localization by analogous means. The acuity of localization in echolocating animals is adequate to provide acoustic images of orientation in three dimensions.
Multiple scattering effects in water saturated beads
Authors: Schwartz L. , Plona T. J.
Published: October 2005

Ultrasonic measurements have been used to study the propagation of longitudinal waves in systems comprised of unconsolidated glass and Plexiglas spherical beads saturated with water. In each sample there is roughly a 20% spread in the sphere diameters. The mean diameters vary between 100 and 500 μm. In every sample the porosity is about 38%. We find that the measured velocity dispersion and attenuation are in generally good agreement with the results of multiple scattering calculations based on the quasicrystalline approximation. In these calculations, the average sphere diameter and porosity of the samples are modeled in terms of the radial (i.e., two site) distribution function, and the scattering properties of the individual spheres are treated exactly. Surprisingly, we find that the properties of the glass and Plexiglas bead samples are remarkably similar. This is true in spite of the fact that the elastic properties of the two materials are quite different. At the lowest frequencies, we show that essentially equal sound speeds for the glass and Plexiglas systems can be understood on the basis of the Biot theory.
Resonance studies of submerged elastic spheroids for several materials
Authors: Werby M. F.
Published: October 2005

The T-matrix formalism may be employed to calculate backscattered acoustical fields from submerged objects. One can plot backscattering functions with respect to frequency change to determine surface resonances associated with material properties of the solids. We perform calculations for six different methods. Our results show that the surface resonance locations are functions of the shear velocity of the material and that the shape of the form function both of the shear velocity of the material and the density. We show how it is easy to relate the location of the resonances with simple geometrical arguments. It has been noted in the past that in the absence of resonances the form function is a function of a solid behaves as a rigid object. We illustrate this point for materials with shear velocities and densities above a certain limit but that it tends to break down for objects with low shear velocities or densities.
Piezoelectric polymer velocity hydrophone
Authors: Josserand Michel A.
Published: October 2005

In underwater acoustical low frequencies applications, a hydrophone with intrinsic directivity is often needed. Velocity-sensitive hydrophones are not the only devices having this property: so have vector-sensitive devices as displacement, acceleration or gradient-pressure hydrophones. Poled polyvinylidene fluoride (PVF2) bimorphs are suitable for design of velocity hydrophones. Because of its softness and mechanical flexibility, a PVF2 bimorph, associated with an inertial structure, follows water particles movement and so the output current from the hydrophone is proportional to the particle velocity of the incident wave. Moreover, the PVF2 bimorphs manufactured in our laboratories,whose thickness may reach 1 mm, make possible a compromise between two opposite requirements: a high sensitivity which needs a thick polymer, a high mechanical flexibility of the membrane to get the lowest possible resonance frequency, that requires a thin bimorph. The study of a low frequency particle velocity calibration system, made possible the achievement of small lightweight PVF2 velocity hydrophones, showing an intrinsic directivity below 100 Hz.
Holographic interferometry in application to the study of dynamic behavior of transducers and arrays
Authors: Fein Howard
Published: October 2005

Experiments have shown that the physical motion of transducers and transducer arrays can be observed using simple techniques of Holographic Interferometry. Certain characteristics of motion and displacement are expected to model the ideal behavior of these devices by defining specific geometries and symmetries in time-average holographic interference fringe patterns. This work resulted in successful characterization of the behavior of both individual transducer modules and multitransducer arrays. These characterizations have led to accurate qualitative performance predictions for transducer systems and are shown to be of great value in understanding their actual operating dynamics. Holographic data and comparisons are presented and discussed.
Three-phase composite backing materials for piezoelectric broadband transducers
Authors: Bar-Cohen Y. , Stubbs D. A. , Hoppe W. C.
Published: October 2005

An accepted technique of producing a broadband ultrasonic signal is by using a piezoelectric crystal backed with a material having a high attenuation and an impedance close to that of the crystal. For this purpose two-phase composites are widely in use, usually consisting of an epoxy matrix and a tungsten powder filler. The tungsten/epoxy is used for its potential in providing a large range of impedances between 3×105 and 1000×105 g/cm2 s, with sufficiently high attenuation. The characteristic curve of impedance versus volume fraction shows a very slow increase in impedance for increasing volume fraction of tungsten up to about 80% above which a sharp increase occurs. To obtain the necessary high impedances of about 25×105 to 30×105 g/cm2 s requires a high volume fraction of tungsten, which is subject to physical packing limits. Moreover, the steep slope in this range makes reproducibility of backing impedance difficult to obtain. These obstacles are common to all two-phase combinations which serve as potential backing materials. In this recent work, it was found that addition of a third phase allows a significant reduction in the volume fraction of the fillers and produces an impedance curve having a relatively low slope. Thus, it provides an important design tool for tailoring transducer characteristics. The analytical results have been verified for several three-phase mixtures and show very good agreement with experimental data.
Diffraction at a fixed point on a plate
Authors: Waterhouse Richard V. , Archibald Frank S.
Published: October 2005

Plane waves at a fixed frequency travel along an infinite thin plate, and are scattered from a fixed point on the plate. The point is constrained to have zero displacement, but the plate is free to rotate about the point. This boundary condition allows the expression for the nearfield diffraction pattern to be obtained in closed form: it contains the Bessel functions J0 and Y0 and the modified Bessel function K0. Computations of this expression have been made, giving contours of the rms displacement out to a distance of five wavelengths from the fixed point. The energy scattered to infinity is also considered.
Tactile aids for the profoundly deaf
Authors: Goldstein Moise H.
Published: October 2005

This paper concerns acoustic-tactile devices for deaf individuals who obtain negligible help from conventional hearing aids. For the postlingually deaf potential benefits include help in lipreading and in maintaining good speech production, and awareness of environmental sounds such as doorbells, telephones, traffic, etc. For the prelingually deaf, simple awareness of sound may facilitate the early acquisition of lipreading and aid production. Wearability of aids and early provision to the prelingually deaf are important considerations. Though the importance of vibrotactile stimulation to the deaf has been apparent through the ages, advances in technology make possible special aids which would have been completely impractical even a decade ago. At present the field has more questions than answers: Are wearable multistimulator devices practical? Do they have a significant advantage over single stimulator devices? What are the best acoustic-tactile transforms? Does the skin sense have adequate channel capacity to serve as a sensory substitute for hearing? How do these aids compare with cochlear implants—as communication aids?—in relieving the isolation of deafness? Current outlook gives optimism that answers to some of these questions will be soon forthcoming.
A tactile display of pitch period for use in sensory substitution
Authors: Boothroyd Arthur
Published: October 2005

A real-time tactile display of fundamental frequency was constructed. This device accepts a train of pitch-synchronous pulses from a pitch extractor and feeds them to one of eight miniature solenoids. Frequency resolution is approximately 1/3 of an octave over a range of 1 1/2 octaves. With the solenoids spaced by 1/4 in., and the index finger as the tactile input site, psychophysical studies showed excellent discrimination among normal English intonation contours and between normal and abnormal contours. The display is currently being used in a study of sensory aids with deaf children in which auditory, visual, and tactile inputs are being compared.
Vowel categorization by 3-year-old children
Authors: Kubaska Cathy A. , Aslin Richard N.
Published: October 2005

A new two-alternative forced-choice procedure was used to assess perceptual constancy for vowel categories in 3-year-olds. The stimuli were edited natural tokens of /i/ and /a/ produced by male and female adults and male and female children. Subjects were visually reinforced for making an appropriate pointing response to one of two televisions. Initial training of the pointing response consisted of pairing an adult male /i/ with one television and an adult male /a/ with the other. After reaching an 80% correct criterion on the training stimuli, subjects were presented with blocks of eight stimuli (four /i/s and four /a/s). For subjects in the vowel group, all the /i/s were assigned to one pointing response, and all the /a/s to the other. For subjects in the arbitrary group, two /i/s and wo /a/s were assigned to each pointing response. The vowel group showed nearly perfect perceptual constancy for vowel categories by ignoring differences in speaker; the arbitrary group performed near chance. The success of this 2AFC pointing procedure will be discussed with respect to additional data on vowel normalization and identification of tokens from various synthetic continua.
Preliminary observations concerning children's labio-mandibular dynamics
Authors: Smith B. L. , Gartenberg T. E.
Published: October 2005

Acoustic measures of children's speech often evidence longer segment and phrase durations than those of adults. From acoustic data alone, however, the cause of these longer durations is unclear. Children might execute their articulatory gestures more slowly than adults, or they might require longer “steady-state” periods for planning subsequent articulatory movements. Because speakers with small oro-facial structures may not move their articulators as rapidly as those with larger oro-facial structures [Kuehn and Moll, J. Phonet. 3, 303–320 (1976)], children could also show slower articulatory movements as merely anatomical artifacts. This pilot study investigated anatomical, physiological and phonetic factors that affect the rates of which children move their articulators. A straingage transduction system was used to monitor inferior-superior movements of the upper and lower lips and mandible during the production of various labial consonants. Subjects were four 4–7-year-old children and three adults. Results indicate that although the children evidenced articulator displacements comparable to those of the adults, the children generally moved their articulators considerably more slowly. [Supported by NIH Biomedical Sciences Support Grant 5 S05 RR07028.]
Stop-vowel coarticulation in the speech of normal 3- and 5-year-olds
Authors: Turnbaugh K. , Daniloff R. , Hoffman P.
Published: October 2005

Three 5- and three 3-year-old children were trained to produce five repetitions of symmetrical CVC syllables; C = stop consonants, V = [i, æ, u, a] in a carrier phrase. Recordings were spectrally analyzed. Frequency measurements were normalized for determination of vowel induced shifts in consonant loci. Results will be compared with adult productions in order to display age-linked changes in coarticulatory patterns, such as were observed by Stevens, House, and Paul (1966).
Non-segmental structure in foreign accent
Authors: Mitleb Fares
Published: October 2005

Typological studies have shown that “voicing” contrast for obstruents is more marked in syllable-final position and least marked in initial position. Also, implicational universal relations suggest that fricatives are more marked than stops and voiced segments are more marked than voiceless ones. The markedness differential hypothesis (MDH) whose underlying claims stem from such studies predicts that syllable-final voicing contrast should be difficult for Germans speaking English since German neutralizes voicing in a marked position. MDH, also, predicts more difficulty for Arabs with English /v/ than with /p/, which are absent from Arabic phonemic inventory, on the basis of markedness. A spectrographic test of English minimal pairs spoken by ten Germans, however, revealed that Germans have acquired control of English voicing in syllable-final position. Another spectrographic test of English minimal pairs spoken by eight Arabs revealed that they had considerable difficulty learning the correlates of English voicing. These results prove that MDH can not correctly predict the relative degree of difficulty in second language aquisition. Instead we propose that nonsegmental similarities and/or differences between languages play an important role in second language acquisition. Thus, due to the similarity between English and German and the differences between English and Arabic with respect to vowel duration difference as a function of voicing, Germans contrasted English obstruents for voicing but Arabs did not. [Research supported by Yarmouk University.]
Lateralization of complex sounds
Authors: Hafter Ervin R.
Published: October 2005

At one time it was felt that interaural differences of time could affect the localization only of low frequencies. Psychoacoustic support for this view came from observations with sinusoidal stimuli that showed a total insensitivity to interaural delays in tones above about 1.5 kHz. In recent years, however, it has become increasingly clear that listeners can detect interaural delay in signals of high-frequency content, as long as the spectrum is complex. For example, performance can be excellent when the signal is a high-frequency carrier that has been modulated in amplitude. The purpose of this paper is to discuss functional differences between simple and complex sounds, with an eye toward development of a model of binaural interaction that accounts for the responses to both. Toward this end, special attention will be paid to stimulus factors that differentiate the two classes. In the preceding paper, Yost compares the responses to interaural differences of time in the stimulus onset and in the waveform. That notion will be expanded here in a model which attributes a spectral role to onsets and which visualizes both individual peaks in the envelopes of high frequencies and the oscillations of low frequencies as successions of mini-onsets.
The noise cues of English and Spanish fricatives
Authors: McCasland George P.
Published: October 2005

In a previous investigation by the writer [J. Acoust. Soc. Am. Suppl. 1 66, S88 (1979)], spoken /f,θ/ noise was amplified to a level typical of /s,∫/ noise with respect to the vowel and spliced into tokens of spoken /si,sα,su, ∫i, ∫α,∫u/ fricative-vowel CV syllables to replace natural /s/ and /∫/ noise segments. Speakers of American English judged the consonant percepts in the modified syllables to be mostly /s/, some /∫/ and infrequently /f,θ/. The high intensity of the amplified /f/ and /θ/ noise in the modified syllables cued the /s,∫/ percepts. Spanish American subjects are currently being tested using the original stimuli. A high % /f/ percepts have been reported. The Spanish speakers find the noise spectrum of the spliced-in /f/ and /θ/ noise segments to be a sufficient cue for an /f/ percept. The response differences between the Spanish and English speaking subjects are attributable to their respective phonological systems. The results are an example of phonetic organization in perception. Our findings are in agreement with Manrique and Massone [J. Acoust. Soc. Am. 69, 1145–53 (1981)], who tested Spanish and English speaking subjects usng a synthetic stimulus continuum.
Computer simulation and laboratory experiments to evaluate the acoustic intensity method
Authors: Seybert A. F. , Thornton W. R.
Published: October 2005

In spite of its elementary physical foundations the acoustic intensity method (AIM) possesses a number of practical contraints that complicate its use when one attempts to implement the method for the purpose of estimating sound power. These constraints are due to the problems associated (1) with estimating the normal component of the intensity vector when multiple acoustic sources are present and (2) with determining a reliable estimate of the sound power by the approximate integration of a finite number of spatially discrete estimates of the intensity on some arbitrary closed surface. To help unravel some of these problems we have constructed a computer simulation of the AIM. This presentation will focus on some of our efforts to use the computer simulation to study the performance of the AIM for various configurations of sources and surface geometries. We will also report the results of laboratory experiments comparing the AIM with other methods of determining sound power.
Use of acoustic intensity technique to measure sound transmission loss of structures
Authors: Crocker Malcolm J.
Published: October 2005

The measurement of the sound transmission loss of structures has traditionally been made with the two reverberation room transmission suite method. If the transmitted acoustic intensity is measured with a two-microphone probe, the transmission loss of a flat panel can be measured using only one reverberation room. Besides the savings in facility costs, this new intensity approach also enables the transmission loss of different areas of a panel to be determined. This information cannot be obtained with the traditional suite method. If an anechoic or reverberation room is available, the transmission loss of more complicated structures such as cylinders and aircraft cabins can also be determined using the new intensity approach. Measurements obtained with the intensity approach of the transmission loss of flat panels, cylinders and aircraft cabins are compared with those obtained from the traditional approach and theory. Agreement is encouraging. The precautions which must be taken with the intensity approach are described. [Work supported by NASA Langley, Hampton, Virginia under Grant N. NAG-1-58].
Combustion noise in industrial burners and furnaces
Authors: Faulkner Lynn L.
Published: October 2005

Two different types of combustion noise generation and reduction are considered: combustion roar and combustion-driven oscillations. The important characteristic of combustion roar sound generation for industrial-size burners is chemically related amplification where the peak frequency is independent of flow-velocity and jet noise amplification where the peak frequency varies directly with flow velocity. Combustion-driven oscillations have an acoustic feedback mechanism which sustains the oscillations and are characterized by a discrete acoustic frequency with higher harmonics. The efficiency of conversion of chemical energy to acoustic energy is considerably higher for combustion-driven oscillations than for combustion roar and the resulting acoustic pressure amplitudes can cause fatigue failures in furnace structures, damage brickwork, and destroy instrumentation. Understanding of the various sound producing mechanisms and the combustion system operating parameters results in the design of quieter equipment or the retrofit of existing combustion facilities for noise reduction. Elimination of combustion-driven oscillations by design or by retrofit is necessary to prevent structural damage to the system.
Engine noise
Authors: Steyer Glen C. , Burton Thomas E.
Published: October 2005

The application of standard techniques of noise estimation to complex machinery has confronted us with several practical problems. Our solutions to some of these problems for internal-combustion engines and transmissions are reviewed here. Designed to estimate the sound radiated from a proposed machine, the methods center on the synthesis of finite-element (FEM) models and test data of related machinery with a finite-element prediction of the conceptual machine. For example, engines similar to a conceptual engine are experimentally characterized in terms of surface vibration velocities and radiation efficiencies over the surface of an engine, with frequency, type, and location of structural excitation as parameters. Finite element models of these engines supplement the data as necessary, leading to a radiation model of the engines which must be analytically modified to apply to the conceptual engine. Then, a detailed FEM model of the conceptual engine predicts transfer functions between structural excitation (combustion, rotation of internals, etc.) and surface velocities. These functions, together with the radiation model, can predict the noise emission from the new engine. Some difficult practical issues are the prediction of differences in forcing functions and vibration transfer functions between existing and proposed machinery, the characterization of combustion noise, and the simplification of models for surface vibration and radiation efficiency. These issues arise in part from a desire to reduce the time and expense of numerical computations.
Experimental measurements of Rayleigh angle scattering from liquid-solid interface
Authors: de Billy M.
Published: October 2005

Experimental results will be presented to demonstrate the existence of a leaky wave generated at the Rayleigh angle by a finite ultrasonic beam incident at any angle of incidence to a liquid-solid interface. This important observation enables us to consider the study on the backscattering phenomena as a particular case of this general mechanism. Different parameters affecting the amplitude of the backscattered signal will be discussed. The choice of these parameters has been suggested by theoretical analysis of Bertoni and Tamir [Appl. Phys. 2, 157–172 (1973)]. The experimental results show that the backscattered energy increases with the Schoch displacement Δs and decreases with the beamwidth.
Back reflection of ultrasonic waves from a liquid-solid interface
Authors: Norris Andrew N.
Published: October 2005

The problem of back reflection of ultrasound from a liquid-solid interface is considered analytically. In experiments it has been observed that the back reflected energy radiates from the interface at the Rayleigh critical angle, irrespective of the incident angle. Mathematically, this radiation corresponds to the complex leaky Rayleigh wave pole of the reflection coefficient. The back-reflected amplitude is proportional to the Fourier transform of the incident field on the interface evaluated at the pole wavenumber. The transforms are calculated for several different ultrasonic beam profiles. The beams are characterized by the field on the transmitting transducer. A Gaussian profile is shown to produce a very small back reflection. Similar results hold for a beam composed of an array of Gaussian beams. This beam has the useful property that as limiting cases it reduces to a simple Gaussian beam and a regular SINC beam. Other beam profiles are examined which give a larger effect than these. The role that the radiation function of the transmitter plays in the back reflection is discussed.
Backscattering at Rayleigh and other angles: A theoretical prediction
Authors: Mayer Walter G. , Ngoc Tran D. K.
Published: October 2005

The spectral representation approach used to calculate beam profile changes upon forward reflection T. D. K. Ngoc and W. G. Mayer, IEEE Trans. Sonics Ultrason. SU-27, 229 (1980)] is extended to include negative angles of reflection, i.e., backscattering. Calculations show that the amplitude of the backscattered beam is a strong function of the incident beam profile. For example, backscattered intensity is predicted to be insignificant when the incident beam is Gaussian but quite measurable for profiles associated with commonly used transducers. This formulation enables one to evaluate reflected field profiles at backscattering and other angles. [Work supported by the Office of Naval Research, U.S. Navy.]
Reducing mooring motion and clock drift noise in acoustic tomography
Authors: Cornuelle Bruce
Published: October 2005

For 300-km ranges the expected size of the rms travel time variations due to eddies in the MODE region is 40 ms. Low-power oscillators can drift 40 ms per month, mooring anchor position uncertainty is ±2 km, and instruments move hundreds of meters as moorings lean in currents. Without sophisticated mooring tracking and clock corrections, the oceanic signal is swamped by this mooring “noise.” The preliminary inversions presented by the Ocean Tomography Group [Nature 299, 121–125 (1982)] were limited to a few days when all corrective systems were operating and required an initializing CTD survey because of the unknown anchor positions. After identifying the structure of mooring and clock offsets, they may be included in the inverse to produce estimates of clock offset and mooring position along the sound-speed maps. This yields useful inversions without mooring tracking or CTD data, so future tomography experiments can be designed with more flexibility, and ship-based tomography is possible even without 1-m navigation accuracy. [Work supported by NSF and ONR.]
Direct and inverse wave propagation theories and the factorized Helmholtz equation
Authors: Fishman Louis , McCoy John J.
Published: October 2005

The reduced scalar Helmholtz equation for a transversely inhomogeneous half-space supplemented with an outgoing radiation condition and an appropriate boundary condition on the initial-value plane defines a direct acoustic propagation model. This elliptic formulation admits a factorization and is subsequently equivalent to a first-order Weyl pseudo-differential equation which is recognized as an extended parabolic propagation model. Perturbation treatments of the appropriate Weyl composition equation result in a systematic development of approximate wave theories while exact inversions for several nontrivial profiles provide for an analysis of strong refractive and diffractive effects. The analysis, in a natural manner, provides for the formulation and exact solution of a multidimensional nonlinear inverse problem appropriate for ocean acoustic, seismic, and optical studies. Backscatter effects in both the direct and inverse problems can be included through weak-backscatter and spatial-dimensional (imbedding) perturbation methods. Moreover, the n-dimensional reduced scalar Helmholtz equation for the transversely inhomogeneous medium is naturally related to parabolic propagation models through (1) the above mentioned n-dimensional extended parabolic (Weyl pseudo-differential) equation and (2) an imbedding in an (n + 1)-dimensional parabolic (Schrödinger) equation. The first relationship provides the basis for the parabolic-based Hamiltonian phase space path integral representation of the half-space propagator. The second relationship provides the basis for the elliptic-based path integral representations associated with Feynman/Fradkin, Feynman/Garrod, and Feynman/Dewitt-Morette. The path integrals allow for a global perspective of the transition from elliptic to parabolic wave theory in addition to providing a unifying framework in the direct and inverse formulations for dynamical approximations, resolution of the square root operator, and the concepts of an underlying stochastic process and free motion on curved spaces, the wave equation and path integral analysis foreshadows computational algorithms, extension to (1) the vector formulation appropriate for elastic media and (2) the bilinear formulation appropriate for acoustic field coherence, and application to wave propagation in random media.
The backward projection of acoustic fields from cylindrical vibrators
Authors: Chen H. W. , Stepanishen P.
Published: October 2005

An approach is presented to backward project an acoustic harmonic wavefield to the vibrating cylindrical source of the field. The approach is based on expanding the known pressure field on a cylindrical surface of the fluid into a series of circumferential modes with axially varying coefficients. After Fourier transforming the coefficients, each mode can be back projected to the source via the use of a backward propagator in the transform domain. As a result of the use of FFT methods the modal characteristics of the backward projected acoustic nearfield and/or the radial surface velocity of a finite cylindrical vibrator with a general velocity can be readily investigated. Numerical results are presented to illustrate the types of numerical problems and the resolution which can be obtained via the use of the method.
Transmission lines and acoustical filters studied by G. W. Stewart
Authors: Savage William R.
Published: October 2005

In the years from 1922 to 1936, G. W. Stewart and his students investigated the properties of transmission lines and acoustic filters. Recently a box that contained most of these filters was discovered in one of the attic rooms of the physics building he designed. The filters are formed from a central small diameter tube with side branches of various types. Some transmission lines have a single side branch and others have a small number of identical side branches. The experiments of the expected transmission by the filters were done by Stewart and his students with sufficient accuracy for a comparison with theory. Electric transmission lines formed the model of construction and analysis of the filter response. The general method of analysis is that used for chains of identical lumped parameter networks. Stewart used telephone receivers for sound sources and his hearing or Rayleigh disks for detectors. Transmission lines and filters based on the Stewart filters could be used with modern sources and detectors in an acoustics laboratory.
Sound localization acuity in mammals and its relation to visual fields
Authors: Heffner Rickye S. , Heffner Henry E.
Published: October 2005

It has often been suggested that the ability of mammals to localize sound is closely tied to visually locating the sound's source. If this is so, then there might exist some parameter of vision which is closely correlated with sound-localization ability. To determine whether some aspect of the visual fields might be linked with sound localization, the extent of the binocular and panoramic fields was measured in fourteen species of mammals whose sound localization acuity is known. It was found that the degree of binocular overlap in mammals is positively correlated with sound-localization acuity for frontally placed sound sources (r = 0.83). In other words, animals with frontally-placed eyes and, therefore, a high degree of binocular overlap, are better able to localize sounds in front of them than are animals whose vision is directed more to the side. However, whether this correlation indicates a close link between sound localization and visual localization or whether it simply indicates an increased interest in frontally-occurring events on the part of an animal remains to be determined. [Work supported by NSF and NIH].
Sound localization and high-frequency hearing in horses
Authors: Heffner Henry E. , Heffner Rickye S.
Published: October 2005

The ability of mammals to hear high-frequency sounds has often been attributed to the need to use binaural intensity differences (ΔI to localize sound [e.g., R. S. Heffner and H. E. Heffner, J. Comp. Physiol. Psychol. 96, 926–944 (1982)]. However, this explanation does not seem to account for the ability of horses to hear high-frequency sounds. Specifically, while horses are able to localize low-frequency tones, they are unable to localize tones above 1 kHz even though they can hear up to 35 kHz. These results suggest that while they can use interaural phase or time differences (Δt) to localize sound, they lack the ability to use the binaural ΔI cue. However, localization tests using filtered noise and sound sources located off to the side indicate that horses use pinna cues to localize sound and rely heavily on the high-frequency content of a sound in order to prevent front-back reversals. It appears, then, that horses have lost the ability to use binaural ΔI and rely primarily on binaural Δt and pinna cues in order to localize sound. Furthermore, since it seems unlikely that horses engage in ultrasonic communication, it apepars that they have evolved high-frequency hearing primarily in response to the need to use pinna cues to localize sound. [Work supported by NSF and NIH.]
Temporal and capacity limitations of auditory memory
Authors: Watson Charles S. , Foyle David C.
Published: October 2005

Certain limits of auditory memory were estimated in a parametric study using tonal patterns. In a same-different task, seven listeners were presented patterns consisting of sequences of equal duration, 300 Hz to 3 KHz tones. A threshold tracking procedure was used to determine the number of tones for which constant-duration patterns could be discriminated. Six pattern durations were investigated, 62.5 to 2000 ms. Seven types of pattern differences were used, including the interchange of component tones, the frequency change of a component tone, replacement of a component tone by a gap, and a change in the temporal position of a gap. For patterns that differ by the presence of gaps, or in gap position, performance is limited by the duration of a just-detectable gap. For discriminations in which the pitch of each component must be processed, there are no clearly defined optimal durations for whole patterns or for pattern components. These results are discussed in terms of the hypothesis that certain types of auditory pattern discrimination are limited by channel capacity (in terms of components per unit time) while others are determined by spectral or temporal resolving power. [Work supported by NIH/NINCDS.]
Vasomotor response to pure tones using multifinger photoplethysmography
Authors: Sarb Eileen Ayres , Mojdehi Ruth , Weiler Ernest M.
Published: October 2005

Changes in digit pulse volume were measured in ten normal hearing, awake adults with a multifinger photocell ploethysmograph (Wasserman et al. 1979). Pure tone stimuli were presented at 500, 1000, and 2000 Hz to determine the threshold required for a verifiable vasomotor response. Results yielded a mean value across frequencies of 32.75 dB SL with a range of 0 to 85 dB relative to voluntary auditory threshold. There was a significant interaction between trials and frequency. The average was comparable to Mojdehi (1980) who reported values equal to 38.18 dB SL for white noise. The pure tone analysis required approximately 2 h per subject. The authors question the practical usefulness of extending the original white noise screening to pure tone assessment.
Evidence of consistent double and triple vocal fold vibratory patterns during pulse register phonation
Authors: Whitehead Robert L. , Metz Dale E. , Whitehead Brenda H.
Published: October 2005

It has been suggested by Hollien et al. [Folia Phoniatr. 29, 200–205 (1977)] that vocal fold vibratory patterns during pulse register phonation may consist of single and/or multiple pulses. These authors did admit, however, that quantifiable evidence for the existence of multiple pulsing was limited. In the present investigation, high-speed laryngeal films (4000 frames/s) were obtained during phonation of the vowel /ɑ/ in pulse register by a normally hearing and speaking adult female. Glottal area-time functions were calculated for 15 consecutive vibratory cycles from a frame-by-frame analysis. The results indicated that the vowel sample was phonated at an average fundamental vocal frequency of 34 Hz. In addition, it was found that each complete vibratory cycle was comprised of either a double or triple pulsing of the vocal folds prior to achieving total closure of the vocal folds, for a substantial period of time, at the completion of each vibratory cycle. These data are discussed with reference to previously reported findings on the physiologic and acoustic features of pulse register phonation. [Work supported by U.S. Department of Education.]
Real-time ultrasound visualization of the tongue surface: Displacement and curvature
Authors: Stone Maureen , Sonies Barbara C. , Morrish Kathleen A.
Published: October 2005

Real-time ultrasound was used to image the tongue surface during speech. Reliability measures were obtained for two judges. The tongue surface was examined during the production of steady state vowels (i, ɑ, u) and rest position, as well as vowels embedded in a carrier phrase (i, ɑ, æ, o, u). The steady state vowels were repeated five times each by five subjects and were examined with respect to radial displacement, curvature, and variability of tongue position. The embedded vowels were part of a carrier phrase which was repeated ten times by four subjects. A curvature equation was used to determine the first and second derivative (slope and concavity) of the tongue surface curvature. The resultant waveform provided amplification of subtle differences seen in the posterior 2/3 of the tongue for the vowels. Results will be discussed with regard to current models of vowel production.
The effects of white noise masking and low-pass filtering on speech kinematics
Authors: Forrest Karen , Abbas Paul J. , Zimmermann Gerald N.
Published: October 2005

High-speed cinefluorography (100 fps) was used to monitor articulator movement of subjects received (1) normal auditory information, (2) their own production of the utterance, low-pass filtered at 600 Hz, or (3) wideband noise. It was hypothesized that if the acoustic speech signal contains information critical to production, specific kinematic alterations would occur as auditory information was reduced. The speech sample was designed to investigate movements of the tongue tip and tongue dorsum under these conditions. The kinematic parameters affected included displacement, steady state duration, and interarticulator timing; however, the direction of change and the articulatory gestures in which these changes occurred were not consistent across subjects. An acoustic analysis of the data indicated changes in formant frequency, formant frequency range, and fundamental frequency. Again, the effects were not consistent across subjects. The results will be discussed to suggest that auditory information “maintains” speech kinematic behavior, either by facilitating or inhibiting muscles of articulation.