bluuebunny/crossref_metadata_2025 huggingface dataset:
Variability of the slope of the loudness function in normal and impaired hearing
Authors: Hellman Rhona P. , Meiselman Carol H.
Published: October 2005

The variability of the slope of the loudness function was determined within and across groups of people with normal and impaired hearing. Slope values were obtained from magnitude estimation and production of loudness and from cross-modality matching and magnitude estimation of apparent length. Loudness judgments were made for 1-s tone bursts at a frequency in the 500- to 2000-Hz range by more than 30 people from the general population with normal hearing in the midfrequency region. Twenty people also judged loudness at three frequencies in the same ear, two in the region of impaired heating and one in the region of normal hearing. Over a wide stimulus range, the relation between loudness and sound pressure for normal hearing was a power function with a slope in log-log coordinates close to 0.60. Both the means and standard deviations of the slopes increased with the degree of hearing loss. These results are compared to those reported in a current paper [R. P. Hellman and C. H. Meiselman, J. Acoust. Soc. Am. 88 (in press)] for five different groups, one with normal hearing and four with noise-induced cochlear impairments. [Work supported by the Rehabilitation Research and Development Service of the VA.]
Auditory filters in noise-masked normal and hearing-impaired listeners
Authors: Leek Marjorie R. , Van Summers W.
Published: October 2005

It has been suggested that the poorer-than-normal frequency resolution often observed in hearing-impaired listeners is a direct result of the sensitivity loss and the high stimulus levels required for testing these listeners, rather than an additional processing deficit. The purpose of this study was to determine whether continuous noise masking simulating a hearing impairment in normal-heating listeners results in auditory filter bandwidths similar to those found in hearing-impaired listeners. Auditory filter characteristics were determined using a notched noise method, assuming a rounded exponential form of the filter. Measurements were made at center frequencies at 500 and 2000 Hz, under conditions of quiet and for two levels of continuous background noise. At 500 Hz, filter bandwidths remained almost constant with increasing threshold levels, with little filter asymmetry. In contrast, at 2000 Hz, normal-hearing listeners' bandwidths increased somewhat when thresholds were elevated by the continuous noise, but remained smaller than bandwidths for heating-impaired listeners with similar thresholds. These data, therefore, do not support the assumption that the impaired frequency resolution of hearing-impaired listeners is totally attributable to their reduced sensitivity. [Work supported by NIH.]
Effects of increased speaking rate on temporal and spectral information for coarticulated vowels
Authors: Stack Janet W. , Strange Winifred , Aguilar Manuela , Clarke William D.
Published: October 2005

As part of a larger study of the role of dynamic (time-varying) spectral information in the perception of vowels, we are analyzing American English vowels spoken in bisyllables imbedded in a carrier sentence by one female who normally speaks rapidly. Eleven vowels in six /hə C1VC2/ contexts (C1 = b,d,g; C2 = d,t) were produced at the subjects' normal speaking rate and at a “rapid” rate (69% of normal sentence duration). Durations of test syllables were systematically reduced; rapid/normal ratios were 75% for CVd syllables and 83% for CVt syllables. Relative durations were well maintained; the correlation between rapid and normal syllable durations was +0.93, and showed only a slight curvilinear trend suggesting almost no limit of compressibility for the shortest vowels. Dynamic spectral structure and “target undershoot” is also being analyzed. Formant frequencies at three points—one-third, one-half, and two-thirds through the vocalic nucleus—will be compared to explore whether “vowel-inherent” spectral change differs as a function of speaking rate. [Work supported by NIDCD-00323.]
A novel method for assessing the annoyance of aircraft overflights in outdoor recreational settings
Authors: Fidell Sanford , Silvati Laura , Harrison Robin
Published: October 2005

Conventional social survey and noise measurement techniques are not well suited to characterization of exposure and collection of prompt reactions to aircraft overflights in outdoor recreational settings. For example, place-oriented measurements cannot be assumed to represent personal exposure as in residential settings, and exit and mailback surveys introduce inevitable delays in responding. A miniaturized, computer-based instrumentation system for simultaneous real-time monitoring of noise exposure and recording of responses may provide a cost-effective alternative to traditional methods of assessing aircraft noise impacts in parks and wildernesses.
Room reverberation measurement by conventional methods and by the MLSSA measurement system
Authors: Kleiner Mendel , Svensson Peter
Published: October 2005

Experiments have been made to compare the measured T60 values measured by conventional analysis equipment to those measured by equipment using the maximum length sequence (MLS) correlation technique such as the commercial MLSSA system. Experiments have also been done using MLSSA impulse response results in conjunction with signal postprocessing in MatLab. Results show that the MLSSA system yielded values which differed by up to 10% from those obtained by conventional techniques. The reasons for this are not entirely clear. MatLab postprocessing also allows signal postprocessing to improve the dynamic range of measurement and the implementation of routines for more specialized room acoustic measures. [Work supported by the Swedish National Council for Building Research.]
Using audiometric database analysis results to prevent occupational hearing loss
Authors: Royster Julia Doswell , Royster Larry H.
Published: October 2005

When audiometric monitoring results for individuals are used to identify employees whose hearing changes indicate inadequate protection from noise exposure, threshold shifts must occur before actions are triggered to increase protection for the affected person. In contrast, when audiometric results for groups of noise-exposed employees are evaluated using audiometric data base analysis (ADBA), the presence of high variability in threshold measurements across the population alerts hearing conservation program (HCP) personnel to program deficiencies before many individuals develop significant threshold shifts. This warning allows HCP personnel to improve the program, thereby preventing hearing loss. Several case histories of successful ADBA applications will be detailed to illustrate how ADBA results can be used to assess program effectiveness for different noise exposure groups, to answer specific questions about hearing protector adequacy, and to set priorities on noise control projects. The preventive benefits from applying the ADBA procedures recommended by ANSI S12 Working Group 12 provide a strong justification for the audiometric phase of the HCP. With more effective programs, reduced employer liability for occupational hearing loss is expected.
Single and combined effects of noise, whole body vibration, ambient temperature, illumination, and different work tasks on changes in experienced subjective stressfulness
Authors: Manninen Olavi J.
Published: October 2005

Presently, there is a lively discussion about how to develop and design new exposure standards for the combined effects of noise and vibration. In order to provide a sound basis for this kind of standardization work and to reach a better understanding of the interactions between the combined effects of the environmental factors involved, seven different experiments were carried out in a special exposure chamber. The studies focused on characterizing the changes in experienced subjective stressfulness. The experiments were either based on block design or factorial experimental design and 192, 80, 10, 15, 90, 108, or 60 healthy male volunteers participated. Results showed that the scores of subjective stressfulness ratings varied greatly depending on the type of the exposure combination and the stressfulness increased with the duration of the exposure. It appeared that exposure situations involving simultaneous noise (85, 90, 95 dBA) and sinusoidal 5-Hz whole body vibration (Z axis; 2.12 m/s2, 2.44 m/s2) were rated more stressful than noise or vibration alone. An elevated environmental temperature (30, 35 °C) increased stressfulness in situations where the subjects were exposed to stochastic vibration (2.8–11.2 Hz) and noise. In particular, young persons (19–25 yr)—in comparison to middle-aged (26–39 yr) or older (40–54 yr)—rated the additional stress caused by noise higher when they were in a competitive situation or doing physically strenuous work and were simultaneously exposed to a whole body vibration at 35 °C. The illumination level of lighting together with smoking seemed to affect the experienced stressfulness, too. [Work supported by the Acad. of Finland.]
J. C. R. Licklider, psychologist
Authors: Miller George A.
Published: October 2005

Personal recollections of working with Licklider at Harvard and MIT between 1943 and 1955, while he still considered himself to be a psychologist. At the Harvard Psycho-Acoustic Laboratory he conducted his definitive studies of the effects of amplitude modulation on the intelligibility of speech and proposed a theory of pitch perception. At MIT in the early 1950s, while continuing his interest in psychoacoustics, he also created a graduate program in experimental psychology and contributed to the creation of the Lincoln Laboratory.
J. C. R. Licklider as computer scientist
Authors: Swets John A.
Published: October 2005

Licklider was a national leader in the development of computer science. His theme was to make computers easier for humans to use, in the interests of aiding human cognition—what he termed “man-computer symbiosis.” Some of his seminal ideas, as developed mainly at BBN during the years 1958–1962, will be described and illustrated.
Active vibration control of a flexible cylinder subjected to periodically shedding vortices
Authors: Kim M. , Baz A.
Published: October 2005

A mathematical model is developed to simulate the dynamics of a flexible cylinder subjected to vortex-induced excitation. The finite element method is used to describe the dynamic characteristics of the cylinder. The fluctuating lift forces induced on the cylinder are assumed to satisfy a modified Van der Pol equation and are determined by the wake-oscillator approach. The dynamic equations of the cylinder are coupled with the modified independent modal space control (MIMSC) method, which actively suppresses the dominant mode of the vibration. The performance of the active controller of the vortex-induced vibrations is obtained at various flow speeds and control weighting parameter. To verify the mathematical model, the computed results are compared with experimental data obtained in a low-speed wind tunnel over a range of Reynolds numbers between 5500 and 7500. Good agreement is observed between the theory and experiments. It was found that the controller is effective in attenuating the transverse vibrations of the cylinder by approximately 40% for all the flow speeds considered.
Excitation of thin beams using asymmetric piezoelectric actuators
Authors: Gibbs Gary P. , Fuller Chris R.
Published: October 2005

In order to analyze the excitation of a complex beamlike structure comprised of arrays of piezoelectric actuators (that may not be arranged in symmetric pairs), it is necessary to determine the effect of a single asymmetric actuator. Using the superposition principle, the excitation of the entire structure can subsequently be analyzed. New analytical relations for the excitation of beams by a single piezoelectric element located on the surface of the beam (asymmetric excitation) were developed. A single asymmetric piezoelectric element when excited produces both flexural and extensional motion in a beam. The relations are used to study excitation of both flexural and extensional waves in beams using a pair of actuators as a function of: actuator length, relative voltage magnitude and phase, and frequency of excitation. The work presented here represents an important step because it is the analytical basis by which simultaneous active control of both flexural and extensional motion in flexible structures can be studied.
Experiments on active isolation using PVDF distributed error sensors
Authors: Lefebvre Sylvie , Guigou Catherine , Fuller Chris R.
Published: October 2005

The work described in this paper is an experimental appraisal of active techniques for the isolation of harmonic vibrations. In particular, the use of polyvinylidene fluoride (PVDF) strips as distributed error sensors on a receiving plate is studied and contrasted to the use of point sensors such as accelerometers. The experimental rig consists of an upper vibrating beam supported via natural rubber passive isolators on a receiving plate with two clamped boundaries. The control approach used is a two-channel adaptive LMS algorithm implemented on a Texas Instrument TMS320C25 DSP chip. The control forces are applied through electromagnetic devices, in parallel with the passive isolators. In general, the results show that the PVDF sensors improve the control performance in terms of global reduction of the response of the receiving structure, by limiting control spillover. The behavior of the system in terms of attenuation is demonstrated to be strongly dependent upon the forcing frequency and the location and nature of the error sensors. For example, the use of the accelerometers located close to the control actuators, while providing high local reduction, can lead to an increase of the global response. [Work supported by NASA Langley and DARPA/ONR.]
Neural networks in articulatory speech analysis/synthesis
Authors: Rahim M. G. , Kleijn W. B. , Schroeter J.
Published: October 2005

A major difficulty in articulatory analysis/synthesis is the estimation of vocal-tract parameters from input speech. The use of neural networks to extract these parameters is more attractive than codebook look-up due to the lower computational complexity. For example, a multilayer perceptron (MLP) with two hidden layers, trained and evaluated on a small data set was shown to perform a reasonable mapping of acousticto-geometric parameters. Increasing the training data, however, revealed ambiguity in the mapping that could not be resolved by a single network. This paper addresses the problem using an assembly of MLP's, each designated to a specific region in the articulatory space. Training data were generated by randomly sampling the parameters of an articulatory model of the vocal system. The resultant vocal-tract shapes were clustered into 128 regions, and an MLP with one hidden layer was assigned to each of these regions for mapping 18 cepstral coefficients into ten tract areas, and a nasalization parameter. Networks were selected by dynamic programming, and were used to control a time-domain articulatory synthesizer. After training, significant perceptual and objective improvements were achieved relative to using a single MLP. Comparable performance to codebook look-up with dynamic programming was obtained. This model, however, requires only 4% of the storage needed for the codebook, and performs the mapping faster by a factor of 20.
Considerations on speaking style and speaker variability in speech synthesis
Authors: Nord Lennart , Granström Björn
Published: October 2005

In the exploration of speaking style and speaker variability, a multispeaker database and a speech production model is used. The structure of the database, which includes professional as well as untrained speakers, makes it possible to extract relevant information by simple search procedures. In perceptual studies both F0 and duration has had an indisputable effect on prosodics but the role of intensity and of segmental variation has been less dear. This has resulted in an emphasis on the former attributes in current speech synthesis schemes. Intensity has a dynamic aspect, discriminating emphasized and reduced stretches of speech. A more global aspect of intensity must be controlled when an attempt is made to model different speaking styles. Specifically, attempts have been made to model the continuum from soft to loud speech. Systematic variation in speech synthesis has been used as a tool to explore possible speaker dimensions, among them reduced and over-articulated speech. Listening experiments have been carried out with the aim to investigate whether it is possible to describe synthesis samples according to different attitudinal and emotional dimensions.
On calculation of the acoustic field in a water layer with variable depth placed on a liquid half-space
Authors: Galanenko Valery B.
Published: October 2005

The wave problem for the variable depth Pekeris waveguide with special cross sections is discussed by means of the cross-section method. The wave field is expanded as the sum of a series and integrated with a regular kernel or by summing a series of mode components only. Both are equivalent to the usual expansion as sums of coupled modes and waves of continuous spectra. A system of coupled differential and integral equations or an equivalent set of differential equations only is obtained. Some numerical results are presented and it is shown that mode reflection coefficients for a near-coast wedge with a typical bottom are less than 0.03 if the incident angle θ = 0.03 and they increase to 0.8 when θ = 60.
Derivation of one-way wave equations for vector wave propagation problems
Authors: Fishman Louis
Published: October 2005

The recent application of pseudodifferential and Fourier integral operators and functional integral methods to the factored scalar Helmholtz equation has resulted in extended parabolic wave theories, corresponding path integral solutions, and a numerical marching algorithm for a variety of acoustic wave propagation problems. These known techniques are applied here to vector wave equations (Maxwell's and elasticity), resulting in new first-order Weyl pseudodifferential equations, which are recognized as exact one-way wave equations for transversely inhomogeneous environments. Perturbation treatments of the appropriate Weyl composition equations for the operator symbol matrix yield high-frequency and other asymptotic wave theories. Unlike the scalar Helmholtz equation case, the one-way vector equations (and a scalar analog provided by the Klein-Gordon equation of relativistic physics) require the solution of generalized quadratic operator equations. While these operator solutions do not have a simple formal representation as in the straightforward (acoustic) square root case, they are conveniently constructed in the Weyl pseudodifferential operator calculus. This is an exact formulation at the level of the wave field—no special symmetry and/or far-field assumptions are made. [Work supported by NSF, AFOSR, ONR.]
Magnus expansion and split-step PE error analysis
Authors: Ryan F. J.
Published: October 2005

A practical problem involved with implementing parabolic wave equation (PE) computer codes is the optional selection of depth mesh and range step-size. Efficiency requires that a varying range step-size be used. An objective method for automatic range step-size selection in split-step PE codes can be derived by an error budget analysis based upon the Magnus expansion of an exponential operator. The method will be described and examples shown for PE propagation in range-dependent environments.
Perth, Bermuda (1962): A shot heard round the world according to adiabatic mode theory
Authors: Heaney K. , Kuperman W. A. , McDonald B. E.
Published: October 2005

A 1962 experiment is examined in which sound from an underwater explosion near Perth, Australia, was detected near Bermuda. A recent attempt [Munk et al., J. Phys. Ocean. 18, 1876 (1988)] to calculate propagation paths for this event included rotational flattening of the Earth and horizontal refraction due to the mean equatorward temperature gradient. That calculation left Bermuda in a shadow zone. The current work invokes adiabatic mode theory to include refraction due to horizontal variations in the vertical mode structure. The results include separate horizontal rays for each of the first few vertical modes, using an archival data set of 230 ocean sound profiles to generate the modes numerically. Where appropriate, interaction with bathymetry was included (scattering and bottom losses). This solution possesses two eigenray groups: group A passes just south of the Cape of Good Hope, at which point group B is almost 1000 km to the south. Intermediate rays are blocked by islands. Group A proceeds unimpeded to Bermuda for a total time-of-flight of 13 360 s, while group B interacts slightly with bathymetry off Brazil, arriving 37 to 45 s behind group A, and suffering 8 to 10 dB more bottom attenuation. These numbers are within experimental uncertainties (main arrival at 13 3644±5 s; pulse train half-width ∼15 s; second arrival ∼30±5 s later). [Work supported by ONR.]
Scale-model acoustical analysis of the Performing Arts Center at Swarthmore College
Authors: Soon Ming Hin , Everbach E. Carr
Published: October 2005

The Lang Performing Arts Center is a newly constructed facility that will house the Departments of Drama and Dance at Swarthmore College. The facility contains a 1000-seat theater with adjustable staging and a moveable concrete wall that can bisect the space into two separate theaters for simultaneous use. A 1/48 scale model of the theater has been constructed and an analysis of the model and a comparison of the model and measurements made in the theater itself are presented. Of special interest are some of the devices that were developed to provide acoustic excitation in the model and in the full-scale theater.
Photoacoustic monopole radiation from laser irradiated fluids
Authors: Diebold G. J. , Khan M. I. , Sun T. , Park S. M.
Published: October 2005

The temporal profile of photoacoustic waves generated by irradiation of fluid bodies with laser light is determined by the wave equation for pressure. Consider excitation where the heating is described as a product of a spatial heating function multiplied by a delta function in time. Solution of the wave equation in one dimension shows that the deposition of heat in space is mapped directly into the time profile of the photoacoustic wave. In three dimensions, spherically symmetric deposition of heat gives a photoacoustic wave proportional to the product of the retarded time with a symmetrized spatial heating function. The wave equation also gives solutions for photoacoustic waveforms generated by long light pulses. In one dimension the acoustic wave is proportional to exciting pulse, in three dimensions the emitted wave is proportional to the first derivative of the exciting radiation, whereas in two dimensions the acoustic wave is a complicated function of time. For long light pulses, the time profile of a photoacoustic wave depends only on the dimension of the wave and the time dependence of the exciting radiation. Expressions for acoustic multipole radiation from irradiated bodies are derived as well. Acoustic waves generated by irradiation of fluids with the output of a Nd:YAG laser are compared with the theoretical results.
Deconvolution problems in a pulsed photoacoustic measurement of methane vibrational lifetimes at 77 K, 0.01 Torr
Authors: Burt J. A. , Yang K. , Halthore R. N. , Allen J. E. , Caldwell J. J. , Delaney P.
Published: October 2005

A conventional gas phase photoacoustic measurement has proved to be less than straightforward due to difficulties associated with deconvolution of the microphone (Bruel and Kjær) response from the vibrational quenching lifetimes measured for methane in various binary buffer gases. The application of the lifetime data is to the aeronomy of Jupiter and preliminary results have been reported [Halthore et al., “Implications of the methane relaxation time measurements for the atmospheres of outer planets and Titan,” 21st Ann. Mtg. Div. Planetary Sci., AAS, 1989]. However, when extensive, accurate recordings were obtained this summer, a systematic error was noted that was attributed to convolution of the microphone's impulse response into the molecular relaxation dynamics. For this reason, it is felt that cw chopped laser excitation would be superior to the Nd-YAG pulsed laser excitation presently used to pump the asymmetric stretch mode of methane at 3.3 μm. [Work supported by the Institute for Space and Terrestrial Physics, Space Astrophysics Laboratory, Toronto.]
The roles of pitch differences and modulation incoherence in concurrent sound segregation
Authors: Carlyon Robert P. , Demany Laurent , Semal Catherine
Published: October 2005

Listeners discriminated pairs of complex sounds, each consisting of two groups of components. Only those components in the lower-frequency group were resolvable by the peripheral auditory system. For the standard stimulus, the F0's of the two groups were frequency modulated coherently at about 125 Hz, so that they were always equal. For the signal, the two F0's were modulated incoherently so that they differed by an amount that oscillated between values proportional to the depth. of FM. Listeners could perform the discrimination when the zero-peak FM depth was about 7%, and two findings indicate that they did so by simultaneously comparing the pitches of the two groups of components. First, listeners could do the task when the lower group consisted of only odd harmonics of 125 Hz (pitch = 125 Hz), but not when it consisted of even harmonics (pitch = 250 Hz). This shows that they were not comparing the rate of amplitude modulation, caused by beating between adjacent components in the lower group, to that in the upper group: These rates were the same in both conditions. Second, performance was at chance when the F0's of the two groups differed (e.g., 100 and 225 Hz), indicating that listeners could not detect FM incoherence per se.
Application of surface waves for antifouling
Authors: Shanker B. , Varadan V. V. , Varadan V. K. , Shaw B. A.
Published: October 2005

Marine fouling in ships and biofouling in condenser tubes, etc. cause numerous problems and a large reduction of fuel efficiency. Conventional methods include toxic paints and hull vibration. A nontoxic solution would be to excite Love waves on the surface and prevent the very first bio-attachment on the surface. A thin PZT film with IDTs (InterDigital Transducers) flush mounted to the surface is used to launch these waves. Experimental results of this technique, which seems viable and cost effective, and most importantly, nontoxic, will be discussed.
Digital time delay network for active underwater acoustic coating
Authors: Howarth Thomas R. , Bao Xiaoqi , Varadan Vijay K. , Varadan Vasundara V.
Published: October 2005

A digital time delay system has recently been developed for control of an active underwater coating. The active coating contains piezoelectric polymer sensors and a piezocomposite actuator encapsulated within a host polymer. The coating is for layering on submerged objects to actively reduce underwater sound reflection. The control system incorporates time delay circuitry as opposed to the analog phase delays used in previous studies. The type of control is an open-loop velocity feedback. This system prevents feedback instability because the acoustic reflection is decoupled from the actuator. The digital controller can characterize both the incident acoustic pressure and the reflected pressure through parallel multichannel processing. The reflected pressure is monitored at the sensors for determination of the effective sound reduction. Experimental results were obtained in a water-filled acoustic pulse tube terminated at its boundary with the active coating. Echo reduction comparisons as functions of sound reduction and bandwidth will be presented.
Voiced versus voiceless inaspirates: Acoustic measurements of English stops
Authors: Koenig Laura L. , Abramson Arthur S. , Lisker Leigh
Published: October 2005

Attention is focused on intervocalic stops in trochaic words. Embedded in semantically plausible sentences, tokens of six pairs of words like robing and roping were recorded by three speakers of American English. These included only places of articulation, labial and dorsovelar, for which the voicing opposition is reliable for all dialects in natural speech. Four acoustic properties were examined because they are considered relevant and they are amenable to editing for perceptual experiments. They are closure pulsing, closure duration, stressed-vowel duration, and release-burst amplitude. The only entirely reliable correlate is presence versus absence of closure pulsing. A fairly good correlate is vowel duration. Vowels before voiced stops are somewhat longer, although there is overlap between the two ranges. Another fairly good correlate is closure duration. Voiceless closures are somewhat longer, although here, too, there is overlap. The amplitude of the burst is a poor correlate, even though voiceless bursts tend to be more intense. These data furnished a baseline for our paper on perception. [Work supported by NIH Grant HD-01994.]
Effects of track fixation on ground-borne noise of train passage
Authors: Barnes James D. , Iacovino Frank N.
Published: October 2005

Vibration measurements were obtained at selected sites along the new rapid transit track of the Southwest Corridor in Boston, MA during dedicated rapid transit train passages. The sites were selected to compare the vibrations associated with the following track fixation techniques: direct fixation, floating slabs, direct fixation with Cologne Egg, timber ties on stone ballast, concrete ties on stone ballast, and timber ties in concrete. In addition, ground vibrations associated with revenue commuter and Amtrak train passages were measured at eight community sites prior to and following the realignment and upgrade of this corridor. The various track fixation techniques and measurements will be described and compared for both the rapid transit and commuter/Amtrak service lines. The ground-borne noise expected for each condition will be discussed and compared to appropriate criteria.
The acoustic material signature for a cracked surface using a point focus acoustic microscope
Authors: Rebinsky D. A. , Harris J. G.
Published: October 2005

Using an asymptotic model of a point focus scanning acoustic microscope, the acoustic material signature for a cracked surface is calculated. The scattered wave fields in the coupling fluid are related to the output voltage by an electromechanical reciprocity relation. This relation may be calculated using either asymptotically approximated wave fields or their asymptotically approximated spectra. Because this relation is linear, the component of the acoustic signature produced by the crack may be separated from that produced by a defect-free surface. The component arising from the scattering from the crack is calculated from approximations to the wave fields rather than their spectra. It is assumed that the crack opening does not perturb the geometric wave field, but that it does strongly scatter the leaky Rayleigh wave, excited by the microscope. It is also assumed that scattering of the Rayleigh waves from the crack can be characterized by reflection and transmission coefficients. The wave fields scattered from the crack are thus calculated geometrically and the corresponding contribution to the acoustic signature is estimated. [Work supported by the MRC at UIUC.]
Psychoacoustic demonstrations of adaptation in hearing
Authors: Champlin Craig , Thibodeau Linda , McFadden Dennis
Published: October 2005

Adaptation in sensory systems involves a decline in the responsiveness to a steady stimulus with time. Three acoustic demonstrations will be presented to illustrate psychoacoustic phenomena that are thought to be related to adaptation processes. (1) Overshoot: The detectability of a brief tonal signal is often improved when its onset is delayed relative to the onset of a wide-band masker. (2) Enhancement for nonspeech sounds: The detectability of a pure-tone component in a complex sound is often improved when it is preceded by a complex in which the energy in the corresponding frequency region has been reduced. (3) Enhancement for speech sounds: Vowel-like sounds are often perceived from spectrally flat harmonic complexes when they are preceded by complexes in which the energy in the frequency regions corresponding to that vowel's formants has been reduced.
Finite-amplitude wave propagation through a two-phase system using coupled generalized Burgers' equations
Authors: Benharbit A. , Marguiles T. S. , Schwarz W. H.
Published: October 2005

The propagation of finite-amplitude acoustic waves through a system of fluid particles in a fluid matrix (aerosols or emulsions) has been examined theoretically by using the continuum volume-averaged balance equations and linear constitutive equations for a two-phase system. Utilizing the technique developed by Lighthill for clean perfect gases, and by Davidson [G. A. Davidson, J. Sound Vib. 38, 475–495 (1975)], who employed the equations of Marble to dilute aerosol media, coupled Burgers' equations for each phase were obtained and analyzed by a perturbation method. The behavior of the higher harmonics of an initial sinusoidal plane wave was determined, and compared to previous work. The present results are applicable to moderately concentrated particulate systems. Also, the use of two-phase equations obtains the effects of viscosity of the media, and also phoresis, such as thermophoresis, on the waveforms.
Phase-space description of random fluid—structure interaction
Authors: Dimitriadis E. K. , McCoy J. J. , Beran M. J.
Published: October 2005

Random dynamic excitation of plates in contact with fluids generally extends over a finite region of the plate. Consequently both excitation and response fields are spatially inhomogeneous. Two-point correlations of such fields are here described as functions of an average and a distance coordinate. The latter is subsequently Fourier transformed and the resulting wave-vector spectrum Γ(x,k;ω) (often called the Wigher distribution function), defined simultaneously in physical and wave-vector space, namely a phase-space, loosely describes energy flow at x associated with the length scale and direction of k. It is shown that the Wigner functions for the response for the excitation are related through a convolution with a kernel function Gs (x—r,k;ω) that depends only on a small number of nondimensional system parameters. The nature of this kernel function and the resulting energy flow directivity are discussed and interpreted. In addition, results are presented for a specific example of an infinite plate in contact with a heavy fluid and excited by a finite region of turbulence in the fluid.
A structural modeling of torsional ship motions
Authors: Cengiz Dökmeci M.
Published: October 2005

This study is concerned with a structural modeling for torsional motions of thin-walled girders of ships by beam idealization on the basis of three-dimensional theory of elastodynamics. In the modeling, (1) the fundamental equations of elastodynamics are expressed in a unified variational form that is expressed by means of Hamilton's principle through Friedrichs's transformation [M. C. Dökmeci, IEEE Trans. UFFC-37, 369–385 (1990)]. Next, (2) a series representation in the aerial coordinates of cross section is introduced for the displacement field. Mindlin's averaging procedure in the variational form is used so as to derive the one-dimensional governing equations of torsional motions. The governing equations that are expressed both in local and variational forms incorporate all the significant effects of motion; the warping of cross section, the geometrical nonlinearity, and the fluid effect by the added mass concept of ship are all taken into account. Further, (3) special cases are discussed and, in particular, the fully linearized governing equations are studied. The sufficient conditions are enumerated for a unique solution of the linearized governing equations by use of the logarithmic convexity argument.
Acoustic target zones for naturally produced vowels in running speech
Authors: Kramer Frank E. , Meyer Donald J. , Fourskis Marlos , Miller James D.
Published: October 2005

Acoustic measures of 2304 vowel tokens of Midwestern American English were collected by one of us (Fourakis). The vowels [i, ɪ, ɛ, æ, ɑ, ɔ ᴜ, u, ʌ] occurred in [bVd] or [hVd] syllables imbedded in sentences spoken with different rates of speech and different stress patterns. There were four male and four female speakers. Two methods of automatic classification of this corpus of acoustic measures into vowel categories are evaluated. One method derives from parametric statistical theory and has been used often in studies of speech sounds. This method is linear discriminant analysis (LDA). The other method assigns each point in the acoustic space a most likely “vowel classification” by a “spatial windowing” procedure. Then an edge-detection algorithm automatically finds the edges of regions with similarly classified interior points. This is called the target-zone method (TZM). Both methods are applied completely automatically to the acoustic descriptions of the vowels. When the vowels are described acoustically in terms of Miller's auditory-perceptual space [J. D. Miller, J. Acoust. Soc. Am. 85, 2114-2134 (1989)], the target zones automatically generated by TZM classify about 85% of the tokens correctly. The LDA method does not achieve this level of performance.
Effects of experimental manipulations of auditory feedback upon vowels
Authors: Tobey Emily A. , Cooper Dawn , Switzer Heidi , Svirsky Mario
Published: October 2005

The role of auditory feedback upon intermediate vowel production was explored by manipulating the amount and type of information provided by a Nucleus multichannel cochlear implant. Four experimental conditions ,were examined: (a) two types of control conditions, the implant turned on versus off, and (b) two experimental conditions that varied the channels being stimulated. Twenty repetitions of the vowels [ɪ], [ɛ], [i], [u] in an hVd context were acquired from four adventitiously deafened adults using multichannel implants. Two of the vowels, [ɪ] and [ɛ], were selected because of previous work indicating significant changes in formant frequencies when the implant was turned on versus off. The vowels [i] and [u] were included as controls since previous work indicated that their formant frequencies failed to change when the implant was turned off. Recordings were digitized at a 20-kHz rate and analyzed using CSpeech. Fundamental frequency, formant frequencies, and duration measures were acquired for each token. Data were statistically treated using a repeated measures ANOVA. Preliminary data indicates that the intermediate vowels rely upon relevant auditory information more heavily for their production than the control, point vowels. [Work supported by NIDCD.]
Musical duplex perception: Does perceptual dominance reflect general principles or specialized modules?
Authors: Hall Michael D. , Pastore Richard E.
Published: October 2005

In a variant of duplex perception (DP), a phonetic module is claimed to take precedence over nonspeech processing based upon maintained phonetic perception despite discontinued nonspeech perception of the critical stimulus component. Recent attempts to replicate these findings with nonspeech stimuli fail to meet proposed criteria for stimuli used in strong demonstrations of DP. The present musical experiment first established threshold intensities for detecting the sinusoidal, chord-distinguishing note in the context of constant-intensity piano notes. Here, AX chord discrimination followed with distinguishing notes varying in intensity. As with speech, complex perception of chords was maintained at intensities significantly below detection threshold for component perception. Both speech and music findings could demonstrate general principles of perception, with multiple-component stimuli preserving a strong integrative relationship between components more readily perceived as singular events with less stimulus energy than is required for isolating individual components. [Work supported by NSF.]
A psychological space for place of articulation
Authors: Li Xiao-Feng , Pastore Richard E.
Published: October 2005

A psychological space for place of articulation was explored using synthetic /ba/ and /da/ stimuli factorially varying in F2- and F3-onset frequencies. The data from a goodness judgment experiment were subjected to the multidimensional scaling. Within the derived space of each phoneme category, the stimulus centered (or the closest to the center) was designated as the prototype. The results from a speeded classification task indicated that the response time to each phoneme is an ordinal function of the goodness measure. The heterogeneity of the resulting goodness spaces and response times in classification suggests that classification of place of articulation could be the consequence of the subject evaluating the membership function relative to the prototype. [Work supported by NSF.]
Perception of prominence in CV sequences by Estonian and English listeners
Authors: Lehiste Ilse , Fox Robert Allen
Published: October 2005

In previous work [I. Lehiste and R. A. Fox, J. Acoust. Soc. Am. Suppl. 1 87, S72 (1990)], the perception of “prominence” in sequences of noise tokens by native Estonian and American English listeners while independently manipulating individual token duration and amplitude were examined. The present study used the same basic experimental paradigm but with synthetic CVs ([ba]) rather than noise bursts. The basic CV token was 400 ms in duration with 40-ms formant transitions and a 360-ms steady-state vowel. However, in the experimental trials, one token in each sequence could be lengthened to 425, 450, 475, or 500 ms and/or one token (not necessarily the same token) could be increased in amplitude by 3 or 6 dB—these duration and amplitude changes were independent. Listeners were required to indicate which CV in the sequence was “more prominent.” Listening tests were given to 33 native speakers of English in Columbus, Ohio and to 40 native speakers of Estonian in Tallinn, Estonia. As in the earlier study, the responses showed that Estonian listeners were more sensitive to token duration in making their “prominence” decisions than were the English listeners. Differences between the two sets of results (obtained using noise versus speech stimuli) will be discussed.
Discrimination of synthetic /la-ra/ by birds
Authors: Dooling Robert J. , Brown Susan D. , Best Catherine T.
Published: October 2005

Discrimination latencies were measured for two species of birds tested using pairs of tokens drawn from three synthetic continua based on the /la/ and /ra/ contrast: full-formant syllables, their sinewave-speech analogs, and the critical F3 distinctions as isolated sinewaves. For the full-formant continuum, both species showed a marked improvement in discrimination near the /l/-/r/ boundary, whereas for the F3 continuum, neither species showed a peak near the phonetic boundary. These results are comparable to human discrimination of the same continua [Best et al., Percept. Psychophys. 45, 237–250 (1989)]. However, for the sinewave-speech continuum, budgerigars showed a performance peak mirroring that for the full-formant syllables, like humans who perceived the sinewave-speech stimuli as speech, while zebra finches showed a linear function mirroring their performance for the F3 sinewaves, like humans who perceived the sinewave speech as nonspeech. These data provide new evidence of species similarities and differences in the discrimination of speech and speechlike sounds that strengthen and refine previous findings of sensitivities of the vertebrate auditory system to several acoustic distinctions associated with speech sound categories. [Work supported by NIH Grant DC00198 to RJD.]
Analog speech processor based on the auditory periphery
Authors: Liu Weimin , Andreou Andreas G. , Goldstein Moise H.
Published: October 2005

Neurophysiological studies of the auditory periphery show that synchrony coding is a robust representation of speech signals. Recent research demonstrated that models of the auditory periphery give superior performance as the front-end signal processor of a speech recognition system, especially when speech inputs are corrupted by noise [H. M. Meng and V. W. Zue, International Conference on Spoken Language Processing, 1053–1056 (1990)]. Here, an auditory periphery model is realized on silicon with analog integrated semiconductor technology to provide a real-time, low-power dissipation preprocessor for speech processing tasks such as speech recognition and aids for the deaf. The model, including the middle ear, the basilar membrane and the hair cell, and synapses, is presented along with the design features of analog CMOS implementation. The pattern of the multichannel outputs resembles the neurogram of the auditory-nerve fibers, i.e., the time-varying instantaneous discharge rates in fibers of various characteristic frequencies, in response to speech signals such as consonant-vowel syllables [H. E. Secker-Walker and C. L. Searle, J. Acoust. Soc. Am. 88, 1427–1436 (1990)].
Loudness levels of three complex stimuli and model predictions
Authors: Jeng Patricia S. , Hall Joseph L. , Levitt Harry
Published: October 2005

Loudness levels were measured for three test stimuli (speech, narrow-band noise, and square wave) at three levels in three test conditions (test stimulus in quiet, test stimulus in presence of masker, and total loudness of test stimulus plus masker). Loudness levels were measured in the traditional way by matching loudness of the test stimulus to that of a 1-kHz tone. In addition, loudness levels were measured using a narrow-band noise as the reference stimulus. The bandwidth of the narrow-band noise used as test stimulus (NBN-150) was 150 Hz, and the bandwidth of the narrow-band reference stimulus (NBN-120) was 120 Hz. Both stimuli were arithmetically centered at 1 kHz. The loudness level functions for speech and for NBN-150 have slopes of approximately unity. However, the loudness level function for the square wave has a slope of greater than unity below about 50 dB SL and the slope decreases above about 50 dB SL. Loudness predictions of two models are computed and compared to the experimental measurements.
Human frequency following responses to vowel-like stimuli
Authors: Ananthanarayan A. K. , Gopal H. S.
Published: October 2005

The frequency following response (FFR) reflects sustained neural activity within the brain stem, phase locked to the cycles of the stimulus waveform. Auditory-nerve single unit responses have been shown to utilize the property of phase locking to represent the stimulus spectrum of steady-state vowels. The purpose of this study was to determine if the scalp-recorded FFR would reveal similar neural representation of steady-state vowels. Scalp-recorded FFRs were obtained from six normal-hearing subjects in response to five different synthesized steady-state vowels [/a/, /i/, /u/, /æ/, and /o/] presented binaurally at 70, 50, and 30 dB nHL. Spectral analyses of the FFRs indicated that, for each vowel, phase locking is robust at the fundamental frequency and the first three harmonics with phase locking to the fundamental preserved even at stimulus levels close to response threshold. Spectral peaks corresponding to the first two formants were observed at only the higher intensities. These results, while not entirely consistent with the single-unit data, seem to suggest that the FFRs reflect neural activity related to the processing of low pitch.