bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of shear modulus on the behavior of acoustically transparent materials
Authors: Dubbelday Pieter S. , Rittenmyer Kurt W.
Published: October 2005

Materials are under development that match density (ρ) and dilatational sound speed (c) to the values of seawater as closely as possible while maintaining sufficient rigidity to serve for structural purposes. Another paper in this meeting by C. M. Thompson and J. R. Griffith (preceding abstract) describes the composition of the material and some of its properties. Matching of density and speed results in transparency for fluids only; the shear modulus in a solid admits the presence of a shear wave which causes deviation from ideal ρ-c behavior. In this paper, the effect of a finite shear modulus on the reflection of plane waves by an infinite plane is analyzed. The shear modulus of the material was measured following a method developed by R. L. Adkins in 1966. Examples are given of the reflection coefficient as a function of incidence angle for values of ρ and c close to those of the medium, and various ratios of plate thickness to dilatational wavelength. The effect of a finite loss tangent in the shear modulus is shown. [Work supported by the Office of Naval Research.]
Dynamic bulk moduli of several elastomers
Authors: Burns Jay , Dubbelday Pieter S. , Ting Robert Y.
Published: October 2005

Dynamic hulk moduli are given as functions of frequency for several types of elastomers over a temperature range of − 10 °C to + 40 °C. Measurements were made by a modification of the acoustic coupler method of McKinney et al. [J. Appl. Phys. 27, 425 (1956)]. Values of K′, the real or storage part of the complex modulus, fell into the range 2 to 4 GPa, typical of values for organic liquids. The loss tangents fell into the range below 5% and were mostly less than 2%, also typical of many liquids. This similarity to liquids suggests that similar short-range dynamic mechanisms dominate the compressional free-volume models. One neoprene sample exhibited the full transition from low to high limiting values of K″ over the experimental temperature range, thereby providing a good test for the applicability of WLF-type temperature “shifting” in these materials. A master curve was constructed for this sample. It gave evidence for a relatively broad spectrum of relaxation times.
Material measurements of two independent viscoelastic coefficients using the Metravib-04 viscoanalyzer
Authors: Kasper R. G. , Bruno A. B.
Published: October 2005

A number of dynamic mechanical measurements have been completed on the Metravib-04 viscoanalyzer for a variety of solid materials. The materials tested were elastomers, foams, and metal/elastomeric composites. For each batch, the materials were tested in the tension-compression mode and in the shear mode in a frequency range of 5.0 Hz to 1.0 kHz at constant temperature. The data produced two independent complex elastic modulii, Young's modulus and shear modulus, as a function of frequency at room temperature. For assumed isotropic and homogeneous conditions, the dilatational and shear-wave speeds were independently calculated for each material. The imposition of the material incompressibility condition (i.e., Poisson's ratio equal to 0. 5) was not required. These values were used as input functions for numerical models of transducer isolation components subjected to various harmonic excitations. A number of examples will be discussed.
Pitch perception in impaired listeners
Authors: Burns Edward M.
Published: October 2005

The study of pitch perception in hearing-impaired listeners is of interest primarily because of the hope that measurements of deficits in pitch perception in listeners with particular types of impairments, in conjunction with other psychoacoustic and physiologic measurements of these same impairments, will lead to insights into the process by which pitch information is encoded in the normal system. This paper reviews studies of frequency discrimination, and pure- and complex-tone pitch perception, in impaired listeners. Among the impairment-related phenomena which will be discussed are: (1) the degradation of frequency discrimination and increase in pitch-matching variability; (2) the exaggeration of various pitch-shift phenomena such as pitch-level effects, diplacusis, musical paracusis, and post-stimulatory pitch shifts; and (3) the degradation of complex tone pitch perception. In addition, other anomalous pitch-related phenomena, which may or may not be considered impairment related, such as tonal tinnitus, tonal monaural diplacusis, and polyacusis, will be reviewed. Finally, the perception of pitch-like sensations by cochlear implantees will be examined.
Physiological observations on the neural representation of complex pitch
Authors: Evans E. F.
Published: October 2005

Pitch models which depend on the manner in which the frequencies of pitch-evoking stimuli are encoded in the temporal discharge patterns of neurones in the auditory periphery, would be easier to test if it were possible to predict the temporal discharge patterns in response to such complex stimuli. As an extreme case, the effects of variants of the click trains, whose pitch has been the subject of controversy between Whitfield and Moore (see Evan's chapter in Hearing—Psychological Bases and Psychophysics, edited by R. Klinke and R. Hartmann (Springer, New York, 1985) have been studied at the level of the cat's cochlear nerve. In particular, the following stimuli have been used on fibers with characteristic frequencies up to 4 kHz: pulse trains with even intervals of 5, 10, 20 ms; uneven intervals of 4.5/5.5 ms, 4.6/5.4 ms, 4.8/5.2 ms, and even intervals of 2.5 and 5 ms with alternate click phases. Autocorrelations have been performed of the spike discharge patterns evoked by the stimuli. To a first approximation, temporal patterns of discharges evoked by the even and uneven interval click trains can be predicted on the basis of simple linear filtering, with filters having the shape and bandwidth characteristics of the fiber's frequency threshold (tuning) curve (FTC). A simple probabilistic model of a cochlear fiber [E. F. Evans, J. Physiol. 298, 6–7 (1980)] preceded by a linear filter having these characteristics predicts the observed patterns well. In particular, the temporal patterns are determined by the degree to which individual harmonics of a complex stimulus interact, after appropriate weighting by the cochlear filter. Two important consequences of this follow. One is that the dominant region for pitch could be considered to be the range of cochlear fiber characteristic frequencies over which sufficient spectral resolution for place models coexists with sufficient interaction of spectral components as required by pitch models based on the microstructure of the temporal pattern of spike discharges. The second is that spectral filtering needs to be incorporated into any temporal fine-structure model: One result is the observed relative insensitivity of the temporal patterns to stimulus component phase, contrary to the objection frequently raised against temporal fine-structure models.
Complex pitch—Effects of context and experience
Authors: Hall Joseph W. , Peters Robert W. , Soderquist David R.
Published: October 2005

Complex pitch perception is influcenced not only by the physical composition of the stimulus, but also by the context in which the stimulus occurs, and by previous pitch stimuli to which the listener has been exposed. Three complex pitch effects will be discussed: (1) Pitch for nonsimultaneous harmonics presented in quiet and in a noise background; (2) short-term complex pitch adaptation effects; (3) long-term changes in complex pitch perception where the pitch associated with one complex tone changes to the pitch associated with a second complex, after the two complex tones are paired and presented to the listener over several hours of listening. Findings will be related to pitch theories, plasticity of pitch perception, and possible organization of complex pitch “channels.”
Interaural contrast effects in vowel perception
Authors: Fox Robert Allen
Published: October 2005

Many recent experiments have suggested that the contrast effect found in vowel identification is not a function of response bias or detector fatigue, but rather of perceptual processes such as adaptation level. However, it is unclear as to whether these contrast effects are both peripheral and central in nature and whether or not subjects must attend to (and/or identify) the contrasting elements. In the present anchoring experiment, subjects identified vowels from a hid-head continuum under two conditions: an equiprobable control condition and an anchoring condition. In the control condition, the stimuli were only heard in one ear, but there were three different anchoring conditions: (1) both targets and anchors occurred in one ear only; (2) targets occurred in one ear while anchors occurred in the opposite ear—all tokens were identified; (3) targets occurred in one ear while anchors occurred in the opposite ear—only targets were identified. As expected, when all stimuli were heard in the same ear, anchoring produced a significant shift in the hid-head phoneme boundary. However, when achors occurred in the opposite ear, a significant shift was obtained only when the anchor was identified. It will be suggested that these results indicate that the vowel contrast is central in nature and may require the focus of attention-driven mechanisms.
Toward a massively parallel system for word recognition
Authors: Wong Maurice K. , Chun Hon Wai
Published: October 2005

This paper describes a massively parallel system for word recognition. Based on the connectionist network model, the system consists of a large number of simple neuronlike processing units, or nodes, which represent words, phonetic segments, or phonetic features. The computation consists of constant updating of activation levels of all nodes, resulting from the excitatory links and inhibitory links between the nodes. Input to the system consists of frame-by-frame scores of similarity to a set of predefined spectral filters, which represents the set of phonetic segments necessary for distinguishing between words in the vocabulary. These similarity scores are combined into phonetic feature indexes for each frame of speech as input to the feature nodes in the network. A linguistic knowledge base is built into the network, allowing both data-driven processing and top-down prediction to cooperate or compete in working toward the correct lexical hypothesis. The system has been implemented using a software package simulating massively parallel networks on a lisp machine. Preliminary testing of the system using digits and nine letters by one speaker is 100% successful in spite of the low frame-by-frame recognition accuracy.
Automatic analysis of speech using parallel cellular pipelined processor
Authors: Hemdal John F. , Longheed Robert H.
Published: October 2005

Early results of analyzing natural speech using a parallel processor were reported before this society in Minneapolis in the fall of 1984. This paper is a presentation of subsquent results obtained. The CYTO-HSS™ parallel pipelined processor, used for analyzing speech spectrograms, is a work station for image analysis, optimized for cellular automata algorithms. The HSS has several advantages over typical Von Neumann type machines. One advantage is speed. In performing similar image processing tasks, the CYTO-HSS™ is from 100 to 10 000 times faster than the VAX. The distinctive features of speech are described in mathematical morphological terms and the parallel processor detects the presence of the features. Examples of stop and fricative detection will be described and shown. Potential applications in speech analysis, automatic speech recognition, speech synthesis, bandwidth compression, and speech enhancement are discussed.
Negative binomial probability models for speech intelligibility data
Authors: Smith Caldwell P.
Published: October 2005

Since reporting at ASA*50 on success in fitting negative binomial probability distributions to speech intelligibility data, extensive additional analyses have been made on Diagnostic Rhyme Test intelligibility data from multi-speaker tests. Modeling involves converting feature scores to frequency counts of listener errors, for each speaker's scores. Scores for the four primary feature states for each of the six phonetic attributes of the DRT represent outcomes of presenting eight tokens to eight listeners; thus error frequency counts from zero to 64 are possible, for each of the 24 attribute states. After conversion of scores to frequencies, a cumulative distribution was formed from the ranked data, a “frequency of frequencies” distribution. The mean and variance of these distributions provided parameters for negative binomial distributions, which were compared with chi-squared and Kolmogorov-Smirnov tests. Similar tests were performed on sub-sets of the intelligibility data representing partitioning into scores for individual speakers, for all male speakers, all female speakers, voiced feature scores, and unvoiced feature scores. Analysis of intelligibility data from tests of a variety of conditions revealed that in the majority of cases these distributions did not differ significantly from the negative binomial probability models, either for the composite data or the partitioned data sets. These findings open up new avenues for assessment and interpretations of speech intelligibility data.
The second Born approximation and high-frequency scattering at low grazing angles
Authors: Chin-Bing Stanley A. , Werby Michael F. , Stanic Steve
Published: October 2005

The first Born approximation has proven to be a successful tool to describe scattering from impenetrable interfaces at high frequency providing the existence of secondary scattering from adjacent parts of the surface is unimportant. This usually means that low grazing angle scattering is avoided for a suitably rough surface where secondary scattering becomes important. To treat secondary scattering from adjacent parts of the interface, one must resort to higher-order Born terms. In particular, the second Born term can account for one secondary event which becomes important at a suitably low grazing angle (depending on surface roughhess). In this study, a formulation based on the second Born treatment for scattering is presented and the results are compared with the conventional first Born contribution.
Inversion of data for near-grazing propagation over rough surfaces
Authors: Lucas R. J. , Twersky V.
Published: October 2005

We apply our results for the coherent response to a point source irradiating an embossed plane [J. Acoust. Soc. Am. 76, 1847 (1984)] to interpret and invert data obtained by Medwin et al. [J. Acoust. Soc. Am. 76, 1774 (1984)]. As emphasized earlier [J. Acoust. Soc. Am. Suppl. 1 74, S122 (1983)], key features arise from interference of elementary components of the corresponding Sommerfeld type wave system based on the complex error function complement Q. Simplified analytical approximations are presented to emphasize the essential physics, and to facilitate initial estimates of unknown parameters. Refined estimates using Q integral theory are incorporated in graphical results to display primary data trends of the magnitudes and phases as well as the dependence of the incremental dispersion on both range and frequency.
Angular dependence of under ice reflectivity in the marginal ice zone (MIZ)
Authors: Gruber Patricia L. , Dicus Ronald L.
Published: October 2005

Acoustic reflectivity measurements from sea ice in the MIZ were taken during MIZEX-84. Signals from explosive charges (MK-61 and -82 SUS) received on 12 hydrophones of a 313-m vertical array were processed to separate single bounce ice reflections from direct path and bottom reflected arrivals by replica deconvolution. Ice reflection loss was computed from the ratio of reflected energy to direct path energy after correction for spreading loss differences between the two paths. Signals from different source ranges and receiver depths were collected on the basis of their specular reflection grazing angles spanning the interval 10° to 30°. Data points with estimated standard deviation of reflectivity greater than 0.2 (based on noise estimates) were excluded. The resulting reflectivity versus grazing angle curves at 64, 96, and 128 Hz displayed high variance presumably due to scattering from a single under ice pressure ridge within the Fresnel zone. With angular smoothing the curves showed small angular dependence and losses on the order of 1.5 dB. Comparison of results with model computations will be discussed.
The effect of an El Niño/Southern Oscillation event on underwater sound propagation
Authors: Palmer D. R. , Lawson L. M. , Daneshzadeh Y.-H. , Behringer D. W.
Published: October 2005

From June 1981 through June 1984, 15 separate ocean cruises were made to the equatorial Pacific to collect hydrographic data at 85°W as part of a NOAA climate program. The most recent El Niño/Southern Oscillation (ENSO) event occurred during this period. Temperature and salinity data obtained during the cruises have been processed and merged with archival data to form a series of sound-speed profiles which reflect the onset, evolution, and cessation of the ENSO event. By using computer models, with these profiles as input data, it is shown that propagation conditions fundamentally changed as a result to the ENSO event. Conditions which support a convergence-zone structure for a shallow source disappeared during the event resulting in bottom-limited propagation. While this severe change provides an opportunity to detect and monitor ENSO events using underwater sound, it prevents the straightforward application of acoustic tomography to obtain the temperature field and, hence, to study the dynamics of the event. For a source located at mid-depth, however, tomographic techniques may be applicable since propagation conditions are not as changeable there.
An analysis of the temporal fluctuations of cw acoustic propagation in the marginal ice zone
Authors: Dahl Peter H. , Baggeroer Arthur B. , Mikhalevsky Peter N.
Published: October 2005

Continuous wave (cw) acoustic transmission data from MIZEX 84 (marginal ice zone experiments) were transmitted between two ships separated by approximately 100 km and propagated via a partially ice-covered path. The signals were stepped in frequency between 25 and 200 Hz for 1 h. Both vessels were drifting freely which resulted in a Doppler shift in the received multipath signal. The measured Doppler compares favorably with available navigational data. The quadrature demodulated received signal is modeled as a (locally) wide-sense stationary process. Accordingly, we can exploit the Gaussian correlation structure and estimate the moments of the power spectrum using the covariance method. This method is computationally efficient and relatively unexploited for this purpose. We relate the rms spectral width directly to the variance of the phase rate (ν2). The value of ν2 is a function of oceanic processes which dynamically perturb the sound field. Estimates of ν2 from the MIZEX data are compared with similar experiments carried out in the more quiescent Central Arctic, and in midlatitude regions.
Low-frequency propagation across an East Greenland ice-edge eddy: Winter conditions
Authors: Mellberg Leonard E. , Johannessen Ola M. , Connors Donald N. , Botseas George , Browning David G.
Published: October 2005

A series of small cyclonic eddies have been observed along the ice edge adjacent to the East Greenland current in the vicinity of the Fram Strait. These eddies arc characterized by a unique spiral surface pattern as pack ice is drawn into the circulation. Melt water from this ice contributes to a complicated temperature-salinity structure. An analysis of low-frequency (50 Hz) propagation is presented using environmental range-dependent acoustic prediction models: parabolic equation (PE) and ray model [GRASS]. The environmental data are for winter conditions based on a longitudinal oceanographic transect. Results are compared to previous analyses of a similar eddy in the Fram Strait under summer conditions and the directional dependence of acoustic modes across the East Greenland current frontal zone. [Work supported by NUSC and ONR.]
Human evoked potentials (EP's) reveal central masking events
Authors: Galambos Robert , Makeig Scott
Published: October 2005

Physiological explanations of human masking usually begin and end with hypothetical mechanical interactions of Bekesy waves at the basilar membrane level, although the coexistence of central neural events has often been postulated. We have simultaneously extracted two scalp-recorded EP's—the auditory brain stem (ABR) and the 40-Hz steady-state (SSR) responses—during stimulation with white noise and monaural clicks of fixed intensity. In the ipsilateral, or direct masking situation, the amplitude of ABR wave V (latency about 6 ms) and that of the SSR (latency perhaps 35–50 ms) both decline as the noise level increases, but with somewhat different slopes. When exactly the same noise sequence is delivered to the contralateral ear, ABR wave V is unchanged, whereas the SSR progressively declines to around 50% of its control size. The results indicate that during masking the neural activity initiated by either ipsi- or contralateral noise interacts centrally with any stimulus-related neural activity delivered to the brain by the auditory nerve. [Work supported by NIH.]
Effects of contralateral stimulation on auditory-evoked potentials
Authors: Zerlin Stanley
Published: October 2005

The effects of contralateral stimulation on wave V amplitude of the auditory brain stem response (ABR) over a range of interaural intensities were studied. Wave V amplitude of a “reference” ear was elicited by 4-kHz tone bursts (10/s) at 85 dB SPL; simultaneous, contralateral, 4-kHz tone bursts were presented at levels of 85, 75, 65, 55, and 45 dB SPL in addition to a no-stimulus condition. (Interaural relations were thus 0, − 10, − 20, − 30, and − 40 dB and a monaural condition.) Resulting wave V amplitudes measured on the reference side were expressed as ratios with respect to the amplitude of the monaural condition. Ratios greater than 1.0 indicated enhancement and ratios less than 1.0 indicated suppression. The 0-dB interaural condition gave a ratio of 1.5–2.0; the − 10-dB condition yielded a ratio greater than 1.0, while the − 20-dB condition gave a ratio of approximately 1.0. The − 30 and − 40-dB conditions yielded ratios well below 1.0, suggesting suppression effects at the brain stem level.
Observations of acoustic wave propagation in the Arctic Ocean—Preliminary results from AATE
Authors: Ewart Terry E. , Reynolds S. A.
Published: October 2005

Preliminary results are presented for the AIWEX acoustic transmission experiment (AATE). Pulsed tones at 2, 4, 8, and 16 kHz were transmitted from a fixed source to three depth cycling receivers for 12 days (spanning a depth of 150 m) and to a fixed receiver 100 m away (for the last 7 days). The plane of the four receivers was perpendicular to the transmission path. Extensive oceanographic measurements in the ray path region were made simultaneously as part of the Arctic internal wave experiment (AIWEX). The depth-time sampling of the acoustic field satisfied the Nyquist criteria. Preliminary analysis indicates a weak fluctuating environment. The acoustic phase is geometric with variations due mostly to the mean sound-speed profile. The internal wave field is weak, the amplitude and travel time fluctuations are much smaller than those observed in the open ocean, and the statistics are not stationary. These acoustic observations, where the statistics of the medium are well known, will provide a thorough test of available predictions of WPRM in depth, range, and time. [Supported by ONR code 425AR, NORDA, and Marconi Systems Ltd.]
The perception of tactile distance: Influences of body site, space, and time
Authors: Cholewiak Roger W.
Published: October 2005

Vibrotactile stimuli are often presented to different body sites. Of the many factors that can affect identification of such patterns are the body site tested and the spatiotemporal influences of nearby stimuli. The data obtained by Kaas, Merzenich, and their colleagues indicate that the degree of “cortical magnification” across different body regions is inversely related to cutaneous receptive field size. Consequently, measures influenced by field size should show similar variation. Geldard and Sherrick have shown such a variation in one tactile illusion, cutaneous saltation. In the series of studies to be discussed, magnitude and matching judgments of patterns consisting of stimuli presented to separated sites, either within tactile matrixes or across separate larger contactors, demonstrate that apparent distance on the skin is inversely related to the interstimulus interval between the two stimuli, directly related to the physical separation between the two, and shows a consistent relationship to cortical magnification. [Work supported by NIH grant NS-04775.]
Measures of temporal processing of vibrotactile stimuli
Authors: Weisenberger Janet M.
Published: October 2005

Knowledge about the ability of the tactile system to process temporally varying stimuli is of interest not only for its additions to understanding the general functioning of the tactile system and its comparability to other sensory systems, but also for the design of tactile aids to alleviate blindness and deafness. In the present paper, previous measures of temporal processing of vibrotactile stimuli are summarized and compared with our recent measures of vibrotactile temporal modulation transfer functions. The modulation transfer function has been found to be a useful framework for describing temporal processing in other sensory modalities. In our studies, sinusoidally amplitude-modulated vibratory carrier signals were presented to the thenar eminence. Results indicated variations in the shape and level of transfer functions with carrier frequency, and considerably better performance for sinusoidal carrier waveforms than for noise carriers. The obtained tactile transfer functions are compared to those for auditory stimuli, and are examined in view of results from studies of vibrotactile temporal masking, to help provide a more complete picture of temporal processing in the tactile system. The implications of these results for the design of tactile aids for sensory impairments are discussed. [Work supported by NSF and NIH.]
A music synthesis system using a personal computer, drum sensor, and MIDI-controlled synthesizer
Authors: Bart D. , Kohut J. , Mathews M. V.
Published: October 2005

A music synthesis system has been built. It consists of an AT&T 6300 computer connected to a Yamaha DX-7 synthesizer and to an electronic drum sensor on which the performer plays. With the exception of the electronic drum, all components in the system can be purchased, the total cost being about $5000. Device driver and interrupt handler programs have been written to interface the computer with the synthesizer and sensor hardware. A real-time control program, RTLET, has been written. In RTLET a set of real-time control processes are activated by sending dated letters between processes. A postmaster program, responsible for overall timing, receives and delivers letters to a control process and activates the process at the date time specified on the letter. RTLET has been used to implement conductor control processes in which the performer controls the playing of a score stored in the computer memory by means of drum strokes.
Handlebars for the Yamahas: The struggle toward more intuitive programming of FM synthesizers
Authors: Gibian G. L. , Hamden E. N. , Bort D. L.
Published: October 2005

One currently popular technique for synthesis of musical sounds employs audio-rate frequency modulation (FM). Although this technique was first suggested in the 1970s [Chowning, J. Audio Eng. Soc. 21, 526–534 (1973)], it is still somewhat difficult to control. The specification of a particular tone color in terms of traditional Fourier amplitudes remains problematic, especially for time-varying spectra because the relative amplitudes of all the components are governed by Bessel functions. Conversely, the natures of the spectra resulting from various configurations of carriers, modulators, and modulators of modulators are not intuitively obvious. Preliminary work on a Fourier-to-Bessel mapping program which is intended to simplify FM implementations of specific spectra will be reported.
The consonance of Pierce scale dyads and triads
Authors: Chowning M. , Roberts L. A. , Mathews M. V.
Published: October 2005

A study of the judged consonance of dyads and triads formed from chromatic intervals in the Pierce scale was carried out. One group of subjects listened to dyads in which the maximum interval was 16 steps or 3 steps more than a tritave (13 steps) and the minimum interval was 1 step. Results showed that: (1) the tritave is very consonant; (2) a single-step interval is very dissonant; (3) intervals of 4 and 6 steps, which make up the “major” and “minor” Pierce scale chords, are relatively consonant; and (4) other intervals have a pattern of consonance which is not yet fully understood. Results also showed that the judged consonance is independent of the average frequency of the dyad. Another group of subjects judged the consonance of Pierce scale triads as well as the dyads which comprised these triads. An additive model gave an excellent fit to the data, that is, the perceived consonance of individual dyads contained in a triad predicts judgments for the triad.
Ray trace calculations of ultrasonic fields
Authors: Johnson J. A. , Carlson N. M. , Tow D. M.
Published: October 2005

A computer code has been written to calculate realistic ultrasonic fields in solids. The program calculates the field due to a transducer coupled to the solid through either a fluid medium such as water or a solid medium such as a plastic shoe with a thin layer of fluid couplant. In this technique the transducer face is divided up into many small areas, each of which is assumed to be a source of spherical waves. A ray is traced from each source point, through the coupling medium and into the solid to the requested field point. The vector sum of the fields of each of the rays is then calculated to find the total incident field at that point for a particular frequency. The calculations have been compared to the fields predicted by the models of Thompson and Gray [R. B. Thompson and T. A. Gray, “Analytic Diffraction Corrections to Ultrasonic Scattering Measurements,” in Review of Progress in QNDE 2, edited by D. O. Thompson and D. E. Chimenti (Plenum, New York, 1983), pp. 567–586] and Thompson and Lopes [R. B. Thompson and E. F. Lopes, “The Effects of Focusing and Refraction on Gaussian Ultrasonic Beams,” J. Nondestruct. Eval. 4, 107–123 (1984)] and with experimental results. [Work supported by the U. S. Department of Energy, Office of Energy Research, Office of Basic Energy Sciences, under DOE Contract No. DE-AC07-76ID01570.]
Acoustic radiation from an impulsive point source in an anisotropic solid
Authors: van der Hijden J. H. M. T.
Published: October 2005

The wave propagation problem of calculating the radiation of elastic waves from a source in an anisotropic medium was formally solved by Duff [G. F. D. Duff, Philos. Trans. R. Soc. London Ser. A 252, 249–273 (1960)], by using the standard method of multiple Fourier transforms. Duff's solution however contains integrals over the wave surface and integrals over the volume between the wave surface and the convex envelope of that surface. Because these wave surfaces can have cusps, Duff's solution is unsuitable for numerical calculation. The farfield approximate solution is known explicitly [E. A. Kraut, Rev. Geophys. 1, 401–448 (1963); and M. J. Lighthill, Philos. Trans. R. Soc. London Ser. A 252, 397–470 (1960)]. It uses the Gaussian curvature of the slowness surface. Even this approximate solution is quite involved when computed numerically. We present the solution as derived by using the Cagniard-de Hoop method. The complexity of the solution is now reflected in the Cagniard-de Hoop contours that represent the mapping from real time to complex ray parameter. These contours can be computed quite easily. Therefore the final expressions are not only very elegant but also computationally friendly. We will show some examples of the results.
Theoretical analysis of the angle beam ultrasonic testing method of unidirectional graphite/epoxy composite material
Authors: Rokhlin S. I. , Bolland T. K. , Adler Laszlo
Published: October 2005

The reflection and refraction of an ultrasonic beam on the boundary of separation between a coupling medium and a unidirectional composite material is studied. The composite material is considered as an anisotropic material of hexogonal symmetry. Two variants of the coupling are studied: first is the immersion variant, when the ultrasonic beam is incident from the liquid; second is the contact variant, when the ultrasonic beam is incident from an isotropic solid wedge and the slip boundary condition, between the solid wedge and the composite material, is used. The energy reflection and refraction coefficients are analyzed as a function of the angle of incidence, with the angle of the orientation of the fibers relative to the incidence plane as a parameter. Principal attention is given to critical-angle behavior and the deviation of the energy flux from the wave normal in the composite material.
Guided waves in nonuniform media
Authors: Lindevald Ian M. , Benade A. H.
Published: October 2005

A waveguide is characterized by three parameters. These are the waveguide cross section A(z), the medium's inertia (density) μ(z), and its elasticity σ(z). The coordinate system is defined by the positions of the guided wave's (constant z) isophase surfaces. The one-dimensional wave-guide equations for generalized effort ε and flow φ can be written ζ = (σ/μ) [ζ″ + 2(ln Rζ)′ζ′] where ζ is either ε or φ, a dot denotes ∂/∂t and a prime ∂/∂z. In the approximation that the wavefronts are parallel, Rε = (A>/μ)1/2 and Rφ = (σ/A)1/2. For non parallel wavefronts greater accuracy can be gained by redefining the R's in terms of the M and N functions of Weibel's waveguide equations. The equation for each aspect (ε,φ) leads to its own locally defined phase and group velocities vpζand vgζ. However, the local wave impedance Zw, and the rate of energy transport vw are defined via both aspects jointly. In general, vpζ,vgζ,vw, and Zw depend on all three parameter functions. If all three functions are constant, we find the familiar results Zw = (σμ)1/2/A and vpζ = vgζ = vw = (σ/μ)1/2. When A(z) varies, leaving μ(z) and σ(z) constant, the equation reduces to the familiar “Webster” equation (or modified by Weibel) first studied by D'Alembert, Bernoulli, and Euler. Otherwise the wave parameters are expressible in terms of the waveguide's generalized radius Rζ its taper R′ζ, and its flare R″ζ. [Work supported by NSF and NIH.]
Discrimination of frequency ratios
Authors: Fantini Deborah A. , Viemeister Neal F.
Published: October 2005

Recent work on spectral profile analysis demonstrates that observers can extract amplitude relationships between components in complex stimuli. The experiments to be discussed demonstrate that observers also can extract frequency relationships, specifically, they can discriminate frequency ratios of components in a two-tone complex. The observer is presented with two complexes, one whose components are at frequencies of f and fr, the other with components at f and f(r + Δt), and, in a 2IFC task, is required to choose the observation interval containing the larger ratio. The base frequency f is random both within and across trials; thus, the observer must, in effect, compare the frequencies within each complex to perform well. Good performance is shown with small values of Δr: for example, with r = 1.25 a Δr of 0.017 yields approximately 71% correct when f is randomized over a 400–800 Hz range. This is comparable to the performance shown by trained musicians in discrimination of musical intervals when each of the two tones comprising the interval are presented successively [E. M. Burns and W. D. Ward, J. Acoust. Soc. Am. 63, 456–468 (1978)]. The paper will summarize our initial findings on the effects of varying r and frequency range, and on the form of the psychometric function. [Supported by NINCDS grants NS12125 and NS07889.]
Frequency-based and temporal-based estimates of auditory filter bandwidth
Authors: Velde Therese M. , Hall Joseph W.
Published: October 2005

Estimates of auditory filter bandwidths were examined from measurements of frequency selectivity and temporal acuity. Frequency selectivity was measured using psychophysical tuning curves and comb-filtered noise masking patterns. Temporal acuity was measured using gap detection and temporal masking period patterns. Measurements for all four experimental paradigms were made at 500 and 3500 Hz using both normal-hearing and hearing-impaired listeners. The results are discussed in terms of the relation between frequency selectivity and temporal acuity as predicted by the auditory linear filter model. The results of the hearing-impaired listeners are compared to the results of the normal-hearing group and are discussed re: the predicted relation between frequency selectivity and temporal acuity.
Temporal invariance for word identification
Authors: Reilly W. , Port R. , Maki D. , Dorffner G.
Published: October 2005

Attempts were made to learn how well timing alone could be used to differentiate words from each other when speakers and tempo vary. In addition, we wanted to determine if this information is being missed by some commercial speech recognizers. A set of 12 phrases and words was selected describable in terms of the same sequence of acoustic intervals but differing in stress, consonant voicing, vowel tensity, etc.: accuse, Otis, advise, it froze, outhouse, appease, abbeys, etc.). The lists were recorded at two tempos by four speakers and prominent intervals were measured. First, discriminant analysis was employed on the measurements to identify the words. Second, the recordings were used with a commercial isolated-word speaker-dependent recognizer for training and testing. Many simple experiments were conducted with these two systems comparing their performance with training on (1) one tempo, testing on the other, (2) one speaker, testing another, and (3) one versus several speakers. The results show that (1) a temporal description for each word can be reliably made that is invariant across speakers and speaking tempo, and (2) for these words, timing performs about as well as the commercial system but made different errors, thus suggesting that such timing information might improve recognizer performance.
The perception of voice quality: Multidimensional scaling evidence
Authors: Kreiman Jody , Papçun George
Published: October 2005

Forty-four listeners aged 21–74 rated the similarity of all possible pairs of ten male voices. Three three-way multidimensional scaling analyses were performed, including all listeners, listeners aged 21–44, and listeners aged 45 or older. A six-dimensional solution was selected for the group data (r2 = 0.655); the dimensions were interpreted as “masculinity,” “sincerity,” “harshness,” “variability,” “breathiness,” and “liveliness.” Although significant differences in discrimination ability have been observed for the two age groups [Kreiman and Papçun, J. Acoust. Soc. Am. Suppl. 1 77, S9 (1985)], individual solutions provided no evidence for differences in perceptual strategies. The distance between each pair of stimuli on each dimension was then compared with the number of times those stimuli were confused. Differences on the first dimension correlated significantly with confusions (r = − 0.74), but no other single dimension was significantly associated with confusability. Moreover, the total distance between stimuli (summed across all dimensions) was no better correlated with confusability than was distance on the first dimension alone. It is hypothesized that listeners evaluate voice quality using a small number of general features that apply to all voices in a population, and a relatively large number of local features that are specific to individual voices.
Effect of forward masker duration on menures of frequency selectivity
Authors: Bacon Sid P. , Jesteadt Walt
Published: October 2005

The effect of forward masker duration on measures of frequency selectivity was examined in two experiments. Masker duration was 50 or 400 ms, and signal duration was 20 ms, with no delay between masker offset and signal onset. In the first experiment, growth-of-masking functions were measured for four normal-hearing subjects for masker frequencies below, at, or above the 1-kHz signal frequency, and straight lines were fitted to those functions using a least-squares criterion. Psychophysical tuning curves (PTC's) and input filter patterns (IFP's) were derived from the fits. In the second experiment, masking patterns (MP's) were measured for a 1-kHz masker presented at 50, 70, and 90 dB SPL. All three measures (PTC's, IFP's, and MP's) show better frequency selectivity for the 400-ms masker particularly on the high-frequency side for the PTC's and IFP's, and on the low-frequency side for the MP's. These data are consistent with a sharpening of frequency selectivity at a stage prior to the adaptation observed in forward masking. [Work supported by NIH.]
Mapping auditory phase sensitivity with timbre discriminations
Authors: Patterson Roy D.
Published: October 2005

A flat-spectrum periodic sound composed of 31 equal-amplitude harmonics was used to investigate the effects of phase on timbre. Listeners discriminated a pulse train, wherein the harmonics start in cosine phase from (1) nonmonotonic alternating-phase waves wherein successive harmonics have fixed phases p and q, and (2) monotonic, decelerating-phase waves wherein successive harmonics are phase shifted by an ever decreasing amount. Both phase manipulations produce detectable timbre changes for pulse rates below 400 Hz but monotonic phase increments have to be much larger than alternating phase differences for equivalent performance. For periodic sounds, the output of an auditory filter with center frequency above the fourth harmonic is a modulated sine wave and the modulator's characteristics appear to determine performance. Alternating-phase waves produce a local maximum in the modulator trough which enables the discrimination to be made within each frequency channel. (These waves sound an octave above the pulse train.) Monotonic-phase waves produce strictly sinusoidal modulators and so the discrimination requires detecting modulator phase differences across filters which is more difficult. (These waves sound like damaged pulse trains.)
Pitch-intensity effects and model calculation of the level dependence of VIIIth nerve response functions
Authors: Tubis Arnold , Jones Kenneth , Burns Edward M.
Published: October 2005

It has been suggested that pitch intensity effects may be correlated with level-dependent shifts in the location of peaks in the VIIIth nerve interspike interval (ISI) histogram [K. Jones, A. Tubis, and E. M. Burns, J. Acoust. Soc. Am. Suppl. 1 74, S8 (1983)]. In order to further explore this possibility, we have carried out a detailed numerical simulation of these shifts and compared them with average human pitch-intensity data. We use the conventional stochastic neural firing model in which the conditional probability for a firing in the brief time interval (t, t + Δt) subsequent to the last previous firing at time t′ is s(t)r(t − t′)Δt, where s(t) is the signal-excitation function and r(t − t′) is the neural refractory function. We use the empirical PST response function of D. H. Johnson [Ph.D. thesis, MIT (1974)], the neural refractory function of R. P. Gaumond [Ph.D. thesis, Washington University (1980)], and the technique of K. Jones, A. Tubis, and E. M. Burns [J. Acoust. Soc. Am. 78, 90–94 (1985)] for extracting s(t) from the PST response. [Work supported by NIH.]
Frequency regionalization in the fish ear
Authors: Cox Mardi , Rogers Peter H. , Popper Arthur N. , Saidel William M. , Fay Richard R.
Published: October 2005

The exact mechanism for frequency discrimination by bony fishes is unknown; however, the results of an experimental study by P.S. Enger [Hearing and Sound Communication in Fishes (Springer, New York, 1981), pp. 243–255] suggest the existence of frequency regionalization on the saccular macula in the ears of codfish. Frequency regionalization is similar to the place mechanism in the cochlea in that different frequencies stimulate different areas of the saccular and lagenar maculae. In this investigation, goldfish are subjected to a single-frequency tone, about 140–150 dB above threshold, for two hours in order to damage areas sensitive to that frequency. During this exposure, the fish is constrained inside a waveguide with controllable acoustic pressure and particle velocity characteristics. The extent of regionalization on the maculae is determined based on electrophysiologically measured degradation of frequency tuning, and hair cell damage found in examination under a scanning electron microscope. In addition, the separate effects of acoustic pressure and particle velocity on frequency regionalization are compared. [Work supported in part by ONR and NIH.]
A computational model for the calculation of field potentials resulting from given conductivity and current source density matrices
Authors: Lambert David C. , Harris David M.
Published: October 2005

If a one-dimensional current source density (CSD) analysis is to be valid, certain conditions must be satisfied: (1) There must be an inherent geometric symmetry to the region being measured, and measurements must be made along an axis of symmetry. (2) Elements within the region must be activated synchronously. (3) The region must have a fairly homogeneous conductivity. We may quantify the relative influence of different factors affecting the CSD by constructing a computational model. The model is based upon the mathematical solution to the general differential equation for the calculation of the CSD. The solution gives the field potentials as a function of position in space, conductivities, and CSD distribution of the region of interest. Numerical integration methods are used to evaluate these field potentials. Once the potentials have been computed, values for the CSD along a given path through the field potential matrix can be derived and compared to the CSD distribution used to calculate the matrix. Using observations concerning the geometry and physical properties of auditory nuclei, this model will augment the construction of CSD distributions based on empirically derived data. [Work supported by NIH.]
Turbulence noise sources in the vocal tract
Authors: Stevens Kenneth N.
Published: October 2005

Theoretical and experimental results relating to the generation of turbulence noise in the vocal tract are reviewed. When the turbulence occurs at the vocal-tract walls or at an obstacle, the source can be modeled as a distribution of dipole sources, which in turn can be represented in one dimension as sources of sound pressure. The source distribution is dependent on the vocal-tract configuration, so that there is interaction between the source and the mechanical configuration of the vocal tract. However, given the flow distribution for a given configuration, the acoustic properties of the airway do not appear to influence the source characteristics except under special circumstances. Calculations of spectra of the radiated sound are made for vocal-tract shapes corresponding to several aspirated and fricative consonants with various assumed distributions for the noise sources. The calculations lead to estimates of the relative level of excitation of each of the natural frequencies or formants, determined by the location and spectrum of the source. The results of the calculations are compared with measured spectra for these sounds, and from these comparisons estimates are made of the probable source distributions. [Work supported by a grant from NINCDS.]