bluuebunny/crossref_metadata_2025 huggingface dataset:
Middle-ear response in the chinchilla and its relationship to mechanics at the base of the cochlea
Authors: Ruggero Mario A. , Rich Nola C. , Robles Luis , Shivapuja Bhagyalakshmi G.
Published: October 2005

The responses of the malleus and the stapes to sinusoidal acoustic stimulation have been measured in the middle ears of anesthetized chinchillas using the Mössbauer technique. With ‘‘intact’’ bullas (i.e., closed except for venting via capillary tubing), the vibrations of the tip of the malleus reach a maximal peak velocity of about 2 mm/s in responses to 100-dB SPL tones in the frequency range 500–6000 Hz; vibration velocity diminishes toward lower frequencies with a slope of about 6 dB/oct. Opening the bulla widely increases the responses to low-frequency stimuli by as much as 16 dB. At low frequencies, malleus response sensitivity with either open or intact bullas far exceeds all previous measurements in cats and matches or exceeds such measurements in guinea pigs. Whether measured in open or intact bullas, phase-versus-frequency curves closely approximate those predicted from the magnitude-versus-frequency curves by minimum phase theory. The stapes responses are similar to those of the malleus, except that stapes response magnitude is lower, on the average, by 7.5 dB at frequencies below 2 kHz and 10.7 dB at 2 kHz and above. Comparison of the responses of the middle ear with those of the basilar membrane at a site 3.5 mm from the stapes indicates that, at frequencies below 150 Hz, the basilar membrane displacement is proportional to stapes acceleration. At frequencies between 150 and 2000 Hz, basilar membrane displacement is proportional to stapes velocity.
A comparison of maximum length and Legendre sequences for the derivation of brain-stem auditory-evoked responses at rapid rates of stimulation
Authors: Burkard Robert , Shi Ying , Hecox Kurt E.
Published: October 2005

Experiments were performed in which brain-stem auditory evoked responses (BAERs) were elicited by two types of pseudorandom pulse trains: maximum length sequences (MLS) and Legendre sequences (LGS). In experiment 1, each pulse sequence was presented at 50 dB nHL with minimum pulse intervals varying from 1 to 10 ms. Wave V latency increased and wave V amplitude decreased with decreasing minimum pulse intervals, with no significant effect of the type of sequence (MLS vs LGS), and no significant interaction between sequence and minimum pulse interval in terms of wave V amplitude or latency. In a second experiment, the minimum pulse interval was held constant at 4 ms, while MLS and LGS levels were varied from 20 to 60 dB nHL. With increasing click intensity, there is a decrease in wave V latency and an increase in wave V amplitude. There was no significant effect of type of sequence (LGS vs MLS) or interaction between type of sequence and stimulus intensity for wave V amplitude or latency. Despite the obvious violation of the assumptions (linearity and stationarity) underlying the application of maximum length sequence analysis and Legendre sequence analysis, both techniques produced reliable responses remarkably similar in morphology to evoked responses obtained by conventional averaging. The results of these experiments support the possibility that analysis methods based on pseudorandom pulse sequences may prove more efficient in data collection and provide a more thorough description of the electrophysiologic behavior of the auditory system compared to conventional averaging.
Binaural forward and backward masking: Evidence for sluggishness in binaural detection
Authors: Kollmeier Birger , Gilkey Robert H.
Published: October 2005

The threshold of a short interaurally phase-inverted probe tone (20 ms, 500 Hz, Sπ ) was obtained in the presence of a 750-ms noise masker that was switched after 375 ms from interaurally phase-inverted (Nπ ) to interaurally in-phase (No ). As the delay between probe-tone off set and noise-phase transition is increased, the threshold decays from the Nπ Sπ threshold (masking level difference=0 dB) to the No Sπ threshold (masking level difference=15 dB). The decay in this ‘‘binaural’’ situation is substantially slower than in a comparable ‘‘monaural’’ situation, where the interaural phase of the masker is held constant (Nπ ), but the level of the masker is reduced by 15 dB. The prolonged decay provides evidence for additional binaural sluggishness associated with ‘‘binaural forward masking.’’ In a second experiment,‘‘binaural backward masking’’ is studied by time reversing the maskers described above. Again, the situation where the phase is switched from No to Nπ exhibits a slower transition than the situation with constant interaural phase (Nπ ) and a 15-dB increase in the level of the masker. The data for the binaural situations are compatible with the results of a related experiment, previously reported by Grantham and Wightman [J. Acoust. Soc. Am. 65, 1509–1517 (1979)] and are well fit by a model that incorporates a double-sided exponential temporal integration window.
Lateralization thresholds obtained under conditions in which the precedence effect is assumed to operate
Authors: Saberi Kourosh , Perrott David R.
Published: October 2005

Interaural differences of time (IDT) thresholds were measured with 600-μs transients. The initial experiment was a successful replication of previous experiments that have obtained the precedence effect in lateralization paradigms (e.g., Yost and Soderquist, 1984). When a dichotic click followed a diotic click with an interclick interval (ICI) less than 1 ms or larger than 5 ms, IDT thresholds were generally less than 40 μs. For ICIs between 1 to 5 ms, IDT thresholds increased to approximately 220 μs. Poorest performance was observed for ICIs of 1.75 to 2.35 ms. During the course of conducting a series of planned experiments on this effect, a substantial drop in IDT thresholds was observed across the ICIs of maximum interest (1 to 5 ms). The precedence effect, which we had replicated in our initial experiment, essentially ‘‘disappeared’’ when the subjects were given sufficient practice on the lateralization task. A number of conditions were explored in an unsuccessful attempt to recover the precedence effect in these experienced subjects. The implications of these results are discussed.
Perceptual linear predictive (PLP) analysis of speech
Authors: Hermansky Hynek
Published: October 2005

A new technique for the analysis of speech, the perceptual linear predictive (PLP) technique, is presented and examined. This technique uses three concepts from the psychophysics of hearing to derive an estimate of the auditory spectrum: (1) the critical-band spectral resolution, (2) the equal-loudness curve, and (3) the intensity-loudness power law. The auditory spectrum is then approximated by an autoregressive all-pole model. A 5th-order all-pole model is effective in suppressing speaker-dependent details of the auditory spectrum. In comparison with conventional linear predictive (LP) analysis, PLP analysis is more consistent with human hearing. The effective second formant F2′ and the 3.5-Bark spectral-peak integration theories of vowel perception are well accounted for. PLP analysis is computationally efficient and yields a low-dimensional representation of speech. These properties are found to be useful in speaker-independent automatic-speech recognition.
Phoneme discrimination using connectionist networks
Authors: Watrous Raymond L.
Published: October 2005

The application of connectionist networks to speech recognition is assessed using a set of eight representative phonetic discrimination problems chosen with respect to a theory of phonetics. A connectionist network model called the temporal flow model (TFM) is defined which represents temporal relationships using delay links and permits general patterns of connectivity. It is argued that the model has properties appropriate for time varying signals such as speech. Networks are trained using gradient descent methods of iterative nonlinear optimization to reduce the mean-squared error between the actual and the desired response of the output units. Separate network solutions are demonstrated for all eight phonetic discrimination problems for one male speaker. The network solutions are analyzed carefully and are shown in every case to make use of known acoustic phonetic cues. The network solutions vary in the degree to which they make use of context-dependent cues to achieve phoneme recognition. The network solutions were tested on data not used for training and achieved an average accuracy of 99.5%. It is concluded that acoustic phonetic speech recognition can be accomplished using connectionist networks.
On effective spectrum-based ultrasonic deconvolution techniques for hidden flaw characterization
Authors: Chen C. H. , Sin S. K.
Published: October 2005

From the pioneering works of Gericke [O. R. Gericke, J. Acoust. Soc. Am. 35, 364–368 (1963)] and some other researchers [L. Adler, K. V. Cook, and W. A. Simpson, ‘‘Ultrasonic frequency analysis,’’ in Research Techniques in Nondestructive Testing, edited by R. S. Sharpe (Academic, London, 1977), Vol. 3; A. F. Brown, ‘‘Ultrasonic spectroscopy,’’ in Ultrasonic Testing, edited by J. Szilard (Wiley, New York, 1982)], frequency spectra of ultrasonic returns form hidden flaws carry a rich amount of information usable for flaw characterization. With a proper modeling of these ultrasonic echoes, the effectiveness of such frequency analyses can be further enhanced by a process called deconvolution or inverse filtering. In this paper, the performances of several deconvolution algorithms when applied to ultrasonic pulse echoes from artificial flaws embedded in some aluminum blocks are investigated. The relative computational complexities of these algorithms are also analyzed and compared. Empirical results shall justify the applications of these algorithms for flaw characterization. Furthermore, on comparing the experimental results, simpler implementations and higher efficiencies should favor the use of the spectrum-based deconvolution techniques over time-domain techniques.
Speed of sound in E
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Authors: Foote Kenneth G.
Published: October 2005

The speed of longitudinal sound waves in Antarctic krill has been measured by the time-of-flight method. The result of 17 separate measurement series on different assemblages of living krill is that the animal’s sound speed exceeds that of seawater at the same temperature by 2.79±0.24%. The mean lengths vary from 29.4 to 38.9 mm, with overall mean 32.2 and s.d. 2.5 mm. The corresponding density of krill of mean length 31 mm is 1.0647±0.0069 g/cm3 . Measurement temperatures varied from 5.3 to 12.1 °C; corresponding salinities varied from 32.5 to 33.87 ppt, which also represent the ambient state. The ambient sea temperature was 2.0±0.3 °C.
Ultrasonic reflection and guided wave propagation in biaxially laminated composite plates
Authors: Chimenti D. E. , Nayfeh Adnan H.
Published: October 2005

This paper presents the results of numerous ultrasonic reflection measurements on plates of laminated composites in which the angle of incidence of a finite-aperture acoustic wave and its frequency have been varied. These experiments have been carried out on biaxially laminated graphite–epoxy specimens utilizing water as a fluid-coupling medium. The stacking sequence of the individual laminae is restricted such that in each layer a principal material axis lies in the incident plane of the acoustic wave. The data are compared to the results of a recent theoretical analysis based on an analytical treatment of wave propagation in orthotropic media in conjunction with a transfer matrix approach. Reflection and transmission coefficients are derived from which the characteristic behavior of the system is identified. Results are presented both as reflection spectra and dispersion curves. In general, very good agreement is found between prediction and experiment. Moreover, significant changes in the reflection spectra are observed, depending on the layer ordering in the composite plates.
Static and dynamic behavior of a porous solid saturated by a two-phase fluid
Authors: Santos Juan E. , Corberó Jaime M. , Douglas Jim
Published: October 2005

A method is presented to determine the elastic constants for an isotropic, porous, elastic solid saturated by a two-phase fluid. Assuming that the shear modulus of the empty matrix is known, it is shown that the six additional coefficients in the stress–strain relations can be uniquely determined by performing two ideal experiments referred to as ‘‘generalized jacketed and partially jacketed compressibility tests,’’ in analogy with the single-phase theory of Biot. Under reasonable assumptions on the behavior of the material, the experiments yield expressions for the coefficients in terms of the material properties of the individual phases and the capillary pressure function relating the pressures in the two fluid phases. Finally, numerical results showing properties of the phase velocities and attenuations for the four different types of body waves are presented and analyzed.
Benchmarks: An option for quality assessment
Authors: Felsen L. B.
Published: October 2005

Benchmarks furnish one option for assessing the quality of numerical computation schemes. The brief introduction here recalls the sequence of events that has led to the group of papers addressing two benchmark problems in underwater acoustic propagation.
Numerical solutions of range-dependent benchmark problems in ocean acoustics
Authors: Jensen Finn B. , Ferla Carlo M.
Published: October 2005

Accurate numerical solutions are presented for benchmark problems associated with propagation in a wedge with different bottom boundary conditions as well as in a plane-parallel waveguide with changing profile with range. The benchmark problems are solved with three different general-purpose numerical codes: (1) a coupled-mode code providing a full-spectrum two-way (backscatter included) solution of the wave equation, (2) a finite-difference PE code providing a wide-angle solution of the one-way parabolic approximation of the wave equation, and (3) a split-step PE code providing a more narrow-angle solution of the one-way parabolic approximation of the wave equation. Only the two-way coupled-mode results can be considered accurate solutions of the benchmark problems.
Ray model solutions to the benchmark wedge problems
Authors: Westwood Evan K.
Published: October 2005

A ray method is used to calculate the acoustic field in the shallow-water, penetrable wedge problems proposed as benchmarks by the Acoustical Society of America. Agreement is excellent between the ray solution and the two-way coupled-mode solution. The ray approach not only constitutes an independent method for comparison with other models, but also provides an intuitive picture of the propagation in terms of eigenrays. An analysis of the eigenray information provided by the ray model reveals that the effects of backscatter are totally insignificant for the penetrable wedge problems considered. The computation time required on a Cyber 180-830 to calculate the field at a single point varies from 5 s near the source to 60 s near the apex of the wedge. The calculation of the field at 400 points along a horizontal line requires less than 10 min.
On the validity of ‘‘fractal’’ finite-element methods
Authors: Sornette D. , Roux S.
Published: October 2005

A new approach for solving plate vibration problems has been introduced by using the Sierpinski gaskets and finite-element method [Jeng et al., J. Acoust. Soc. Am. 82, 1829 (1987)]. In this comment, the nature of the approximation inherent to this approach and its compatibility with the essential constraints of conformity which must hold in finite-element mesh are analyzed. It is shown that the method of Jeng et al. corresponds to solving a different problem to the one initially posed, namely, the problem of a plate cut hierarchically along the segments of the Pascal–Sierpinski gasket. A direct extension of the method to correct this drawback leads to a very complex finite-element scheme in which a whole set of different interpolation polynomials of high degrees must be used. Therefore, the implementation of a fractal mesh for regular objects reduces neither computing time nor memory requirement unless conformity is not satisfied. Finding a recursion relationship relying on fractal mesh thus remains a difficult open problem.
Direction-dependent spectral properties of cat external ear: New data and cross-species comparisons
Authors: Musicant Alan D. , Chan Joseph C. K. , Hind Joseph E.
Published: October 2005

Free-field to eardrum transfer functions were measured in anesthetized cats inside an anechoic chamber. Direction-dependent transformations were determined by measurement of sound-pressure levels using a small probe tube microphone surgically implanted in a ventral position near the tympanic membrane. Loudspeaker and probe microphone characteristics were eliminated by subtraction of the signal recorded in the free field with no animal present. Complexities of the transfer function, which include the presence of prominent spectral notches in the 8- to 18-kHz frequency region, are due primarily to the acoustical properties of the pinna. Differential amplification of frequency components within the broadband stimulus occurs as a function of source direction. Spectral features vary systematically with changes in both elevation (EL) and azimuth (AZ). The contrast between a notch and its shoulders is enhanced in the interaural spectral records. Spectral data from single source locations and spatial data for single frequencies at many locations are presented and comparisons with other species are drawn. It is suggested that spectral features in the 8- to 18-kHz region provide some of the necessary spectral information for sound localization and that the contrast in spectral energy between the frequencies at the notch and its shoulders is a potential directional cue.
The effects of a surround on vibrotactile thresholds: Evidence for spatial and temporal independence in the non-Pacinian I (NP I) channel
Authors: Van Doren Clayton L.
Published: October 2005

Detection thresholds were measured for sinusoidal vibrations applied to the thenar eminence and volar forearm. Stimuli were applied via a 0.72-cm2 circular contactor, with and without a rigid surround. At low frequencies, below about 40 Hz, the thresholds were higher without the surround than with the surround. However, in contrast to earlier reports, the shape of the threshold function was the same with and without the surround, suggesting that the temporal and spatial tuning characteristics of the non-Pacinian I (NP I) channel are independent.
Active control of noise transmission through a panel into a cavity: I. Analytical study
Authors: Pan Jie , Hansen C. H. , Bies D. A.
Published: October 2005

A technique for controlling noise transmitted into the interior of a cavity involves use of point force actuators on the boundary structures. This paper is an analytical study of the nature of the control mechanism. A rectangular panel–cavity system has been used as a model for this study. The test panel was selected so that the resonance frequencies are well separated. The responses of the structural vibration and the cavity sound field are examined under both controlled and uncontrolled conditions. Results obtained demonstrate that there are two different control mechanisms. If the system response is dominated by panel-controlled modes, sound energy in the cavity is minimized by suppressing the panel modes that radiate into the cavity. If the system response is dominated by cavity-controlled modes, the control force is used to change the panel velocity distribution and thus adjust the radiation of each panel mode. In this latter case, the real part of the sound power radiation into the cavity is minimized, but there may be an increased local reactive intensity field and increased panel-vibration level.
Resonances and surface waves in the scattering of an obliquely incident acoustic field by an infinite elastic cylinder
Authors: Bao Xiao-Ling , Cao Hui , Überall Herbert
Published: October 2005

The relationship between resonances and surface waves in the scattering of an obliquely incident acoustic wave from an infinite elastic cylinder is discussed. From the three-dimensional normal-mode solutions for a free cylinder, the resonance frequencies of the cylinder and, correspondingly, the phase velocities of helical surface waves and their relation to the helical angles are obtained. Furthermore, as the cylinder is excited by sound waves incident through ambient water, the dispersion of phase velocity for helical surface waves as a function of the angle of incidence has also been derived. Comparing the results of the present work with the results given by Flax et al. [J. Acoust. Soc. Am. 68, 1832 (1980)], it was found that, for the case of oblique incidence, the resonance frequencies are basically in agreement with the frequencies of the minimum values of the form function, analogous to the case of perpendicular incidence.
An alternative mathematical description of the relationship between noise exposure and hearing loss
Authors: Bies David A. , Hansen Colin H.
Published: October 2005

Retrospective investigation of large populations has provided means for determining quantitative relationships between the hearing levels of non-noise-exposed populations and age, and between the hearing levels of noise-exposed populations and age and noise exposure. In the latter case, noise exposures have been predominantly steady state over many years and no way of measuring the effects of noise alone, excluding the effects of age, has ever been demonstrated. In the following paper, attention is confined to the problem of developing a mathematical description of an existing set of empirically determined hearing level data; questions of audiology are not of concern here. It is shown that the mathematical analysis traditionally used to determine the contribution of noise exposure alone to hearing level is not unique; an alternative formulation is possible and indeed is demonstrated. Whereas the traditional formulation leads to the conclusion that noise-induced hearing loss scales on the integral of sound pressure squared with time, and thus, to the equal energy hypothesis, the alternative formulation leads to the conclusion that noise-induced hearing loss scales on the integral of pressure with time. Since either formulation adequately describes the data, and the equal energy hypothesis has never been adequately substantiated, use of the latter hypothesis to extend the findings of steady-state exposures to application for unsteady exposures is not justified. The alternative formulation presented here is recommended for consideration.
Vibration transmission through frame or beam junctions
Authors: Moore James A.
Published: October 2005

A model of vibration transmission through junctions of one-dimensional frame members has been developed. The formulation is flexible in allowing from two to four frames at the junction where the frames lie in the same plane and intersect each other at 90° orientations. The extension to arbitrary orientations in the same plane was derived and the approach for arbitrary orientations in three dimensions is suggested. The model allows for torsional, longitudinal, and bending deformation about two axes. When the frames all lie in the same plane a decomposition into in-plane and out-of-plane motions occurs that simplifies the solution procedure. Calculations for a frame construction representative of helicopter airframes indicate that out-of-plane bending and in-plane longitudinal motion are strongly transmitted across frame junctions. Torsion and in-plane bending are more weakly transmitted. The effect of junction asymmetries in producing transmission into otherwise unexcited motions is pointed out.
Propagation and interaction of two collinear finite amplitude sound beams
Authors: Naze Tjo/tta Jacqueline , Tjo/tta Sigva , Vefring Erlend H.
Published: October 2005

Propagation and interaction of two collinear finite amplitude sound beams is investigated using Fourier series expansions and numerical methods to solve the nonlinear parabolic equation. The analysis extends to ranges beyond the shock formation distance. Propagation curves and beam patterns for various components of the acoustic field (harmonics and combination frequencies) are shown. Wave profiles at various ranges are also presented. In order to fully appreciate the importance of nonlinear effects on the parametric generation of sound, the results obtained from the fully nonlinear model are compared with those obtained for sources operating at moderate intensity (linear/quasilinear theory) for various source levels, downshift ratios, and absorption lengths. Also discussed is the possibility of matching the solutions of the nonlinear parabolic equation and of the spherical Burgers equation in the far field. The numerical results are compared with some earlier experimental observations by other authors.
Excitation of a Helmholtz resonator by an air jet
Authors: Khosropour Roset , Millet Peter
Published: October 2005

The internal spectra of several air jet excited Helmholtz resonators with natural frequency f0 of approximately 250 Hz, as a function of jet speed v between 0 and 5000 cm/s, were surveyed. Above the edge tone region the frequency of oscillation ranged between 140–305 Hz. Domains of jet speed in which a single frequency Helmholtz mode occurs are separated by narrow transition zones where Helmholtz modes of very low amplitude having two different frequencies either produce a heterodyne or alternate. The Helmholtz mode is excited throughout the range of v considered. Harmonics of the Helmholtz mode occur in the highest and next to highest domains and frequency mixing between it and the lowest standing wave mode occurs in the highest domain. In the highest domain a standing wave mode at approximately 6f0 cooperatively excites the Helmholtz mode. An approximate linear model incorporating an empirical dispersion relation is used to explain the major features of frequency versus jet speed behavior. The effects of varying jet width and neck length are examined.
Sound-producing sources as objects of perception: Rate normalization and nonspeech perception
Authors: Fowler Carol A.
Published: October 2005

In a variety of experiments and paradigms, researchers have attempted to determine whether or not speech perception is specialized by comparing perception of speech syllables to perception of nonspeech analogs. While nonspeech analogs appear optimal as comparisons to speech because they are acoustically similar without being recognized as speechlike, it is argued that the comparison they offer is confounded and uninterpretable. Two experiments are designed to show that, in auditory perception generally where acoustic signals are causal consequences of mechanical events, perceptual experiences are of the mechanical events themselves, not of the acoustic signal. This has two consequences. One is that there is a confounding in comparisons of speech with sine wave analogs that, whereas the one perceived as speech also has a definite causal source, the other, perceived as nonspeech, has an indeterminate or ambiguous source. A second is that response patterns in classification tasks such as those used in the literature comparing speech to nonspeech will reflect properties of the perceived sound-producing event; they will not provide a clear window on auditory system processes used to recover event properties. Experiment 3 is designed to show that perception of many acoustic-signal-producing events can appear to be special by the logic of speech–sine wave comparisons—even events that cannot plausibly be supposed to involve a specialization.
Phonological primitives: Electromyographic speech error evidence
Authors: Mowrey Richard A. , MacKay Ian R. A.
Published: October 2005

Speech error data have been used to argue for the psychological reality of distinctive features and phonemes as well as the hierarchical ordering levels of processing for speech production. The models of production that have emerged from analysis of these data are nearly unanimous in characterizing (implicitly or explicitly) the motor output level as entirely governed by prior selection and processing of larger units, especially the phoneme. This study reports on the laboratory elicitation of sublexical speech errors by means of tongue twisters. Simultaneous audio and electromyographic recordings were analyzed. Where possible, single-motor unit discrimination was carried out to preclude the possibility of signal contamination by activation of adjacent musculature. The results indicate that traditional methods of data collection on which most speech error corpora are based are inadequate. Production models based on these corpora are not supported by the electromyographic data and must accordingly be revised.
Gender comparisons of children’s vocal fold contact behavior
Authors: Robb Michael P. , Simmons John O.
Published: October 2005

Vocal fold contact behavior was examined in separate groups of boys and girls through application of an electroglottograph (EGG). In general, a contact quotient (EGG duty cycle) showed minimal differences within and between boys and girls during sustained production of the vowels /i/, /u/, and /a/. The findings are discussed with respect to the laryngeal behavior of prepubescent children as well as the clinical utility and applicability of the EGG for examining phonatory behavior among young children.
Uncertainty about the correlation among temporal envelopes in two comodulation tasks
Authors: Wright Beverly A. , McFadden Dennis
Published: October 2005

The threshold of a 1250-Hz tonal signal was measured in the presence of five noise bands (each 50 Hz wide, centered at 850, 1050, 1250, 1450, and 1650 Hz) under five conditions of uncertainty about the waveform type (‘‘correlated’’ or ‘‘uncorrelated’’), and/or the specific waveform sample to be presented. The waveform type was correlated when the temporal envelopes of all of the noise bands were the same, and was uncorrelated when the temporal envelope of the band centered on the signal differed from the common envelope of the other bands. At the low-uncertainty end of the continuum of conditions, the same waveform type was presented throughout an entire block of trials, and, in addition, the same waveform sample was presented on the two observation intervals of a single trial (but changed across trials). At the high-uncertainty end of the continuum, both the waveform type and the waveform sample were chosen at random for every observation interval. Threshold estimates obtained from trials in which both observation intervals contained the same waveform type were not affected by uncertainty about the waveform sample within a trial, nor by uncertainty about the waveform type introduced across trials. Thus the comodulation masking release, or CMR (the difference in the thresholds obtained with the uncorrelated and correlated waveforms), calculated from these types of trials was robust across all of the uncertainty conditions. However, on those trials in which one correlated interval and one uncorrelated interval were paired, threshold estimates were influenced by a bias for listeners to choose the uncorrelated interval as the signal interval, whether or not it actually contained the signal. This bias reveals the importance of recognizing the contribution of the nonsignal interval in experiments involving masker uncertainty. Parallel results were obtained using the comodulation detection difference (CDD) task. In some conditions, marked individual differences were observed.
Cochlear action potential tuning curves recorded with a derived response technique
Authors: Salt Alec N. , Garcia Philip
Published: October 2005

Previous action potential (AP) tuning curve methods have used a reduction in amplitude of the probe-elicited AP as an indication of tone-induced masking. The reduction criterion used in different studies has varied from 25% to 100%. For low level probe stimuli, which elicit a low-amplitude AP, this is a sensitive indicator. In contrast, for high-amplitude AP responses elicited by high-level stimuli, the required reduction in absolute terms is large, making it an insensitive indicator. AP tuning curves have been recorded using a sensitive method for detecting masker/probe interaction with a fixed criterion, unrelated to the unmasked AP amplitude. For each masking condition, a derived response was obtained by digitally subtracting the tone-masked AP waveform from the unmasked response. Derived responses are generated if there are ANY changes in the AP waveform induced by the masker, including amplitude changes, latency changes, or even changes in AP morphology not necessarily associated with the major peaks. A fixed criterion (10 μV) of tone-derived (TD) response was used as an indication of interaction of the responses to the masker and probe. Tuning curves generated by this method were compared with those generated by conventional amplitude reduction (AR) methods. TD tuning curves show different characteristics, especially with respect to increasing probe levels. They appear to give a good representation of the array of afferent fibers responding to a probe stimulus. In addition, frequency regions making minor contributions to the AP are better represented in TD tuning curves.
Temporal responses of primarylike anteroventral cochlear nucleus units to the steady-state vowel /i/
Authors: Winter Ian M. , Palmer Alan R.
Published: October 2005

It has previously been shown that a population of units classified as ‘‘primarylike’’ and located in the ventral cochlear nucleus of the anesthetized guinea pig was unable to signal the position of the higher formant-related peaks (>1.5 kHz) of steady-state vowels in terms of a temporal–place representation [Palmer et al., J. Acoust. Soc. Am. 79, 100–113 (1986)]. In this paper, it is demonstrated that units characterized by a prepotential in their spike waveform and a primarylike post-stimulus time histogram shape can encode the relative position of the formant peaks present in the spectra of steady-state vowels in terms of a temporal–place code. The possible reasons for the differences in the present results and the previous report are discussed.
A model for the computation and encoding of azimuthal information by the lateral superior olive
Authors: Reed Michael C. , Blum Jacob J.
Published: October 2005

A structural model is proposed for the processing of interaural intensity differences by the lateral superior olive. One fundamental assumption is that the incoming excitatory projections from the ipsilateral anteroventral cochlear nucleus innervate columns of LSO neurons serially according to threshold. A second fundamental assumption is that the inhibitory innervation from the ipsilateral medial nucleus of the trapezoid body is also serially arranged according to threshold but in the opposite direction along the LSO column. Using neurophysiological and neuroanatomical data for neuronal response curves, connectional patterns, and cell and synapse numbers, the model was formulated quantitatively and implemented for machine computation. Azimuthal location is encoded by the position along the LSO column where LSO cell firing first goes to zero. Accuracy of coding was tested for three different connectional schemes, for variations in neuronal parameters, and for cell and synapse death. Encoding is shown to be independent of absolute sound level and to vary linearly with interaural intensity difference.
Fundamental frequency of beams of nonuniform cross section by means of the integral equation approach and Rayleigh’s optimization suggestion
Authors: Gutierrez Roberto H. , Laura Patricio A. A. , Rossi Raul E.
Published: October 2005

The present paper deals with the solution of the title problem applying Lord Rayleigh’s optimization concept when solving integral equations by means of the Ritz method. Polynomial expressions containing a power-law term with an undetermined exponent ‘‘γ’’ are used. Since the calculated eigenvalue constitutes an upper bound, by minimizing it with respect to γ, one is able to improve the value of the frequency coefficient. A lower bound is then determined using the method of traces. It is shown that both sets of results, upper and lower bounds, are quite close and are also in agreement with the numerical results obtained by means of a finite element algorithm.
Range resolution and the possible use of spectral information in the echolocating bat, E
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Authors: Mogdans Joachim , Schnitzler Hans-Ulrich
Published: October 2005

Individuals of the echolocating bat Eptesicus fuscus were trained to discriminate simulated two-wave-front targets with internal time delays of 0 to 100 μs between the wave fronts from a one-wave-front target. The ability of bats to discriminate between such targets can be referred to as range resolution. In Eptesicus fuscus, this ability is limited to distinct internal time delays (12, 32–40, and 52–100 μs) between the two wave fronts of a double-wave-front target. Analysis of the simulated two-wave-front echoes reveals periodic frequency minima in the spectrum. Position and separation of these spectral minima depend on the time delay between the two wave fronts. The occurrence of spectral minima within the frequency range of the first harmonic in the echo of the bats’ echolocation call correlates to the bats’ ability to discriminate a one-wave-front echo from two-wave-front echoes, suggesting that Eptesicus fuscus uses spectral differences within the first harmonic in echoes for range resolution.
Sound transmission through single plates with absorptive facings: Improved theory and experiment
Authors: Takahashi D.
Published: October 2005

This article forms a complement to a theoretical investigation into the problem of sound transmission through a single plate with absorptive layers attached on source and/or receiver side, previously published [D. Takahashi, J. Acoust. Soc. Am. 83, 1453–1457 (1988)]. The theory is improved on several points regarding both the absorptive layer and acoustic coupling at the radiation boundary. An expression with a simple form for predicting the transmission loss, having consistency with the well-known transmission theory of single plates, is obtained. Also, the principle of reciprocity holds in the improved theory. The accuracy of the theoretical prediction is discussed by comparison with experimental data measured by using the reverberation-room method. The results are in good agreement in the trend of the effect of absorptive layer on the transmission loss.
On the level-dependent penalty for impulse sound
Authors: Vos Joos
Published: October 2005

At relatively low A-weighted equivalent levels (Leq ), road-traffic sounds are rated to be less annoying than impulse sounds. The differences, however, decrease with increasing Leq of the sounds, which indicates that the penalty for impulse sound seems to be level dependent. It was questioned whether the decrease of the penalty with increasing Leq might, at least partly, have been a consequence of the use of the ten-point rating scale. In experiments 1 and 2, the relevance of the level-dependent correction was therefore studied further by using the method of adjustment. The mean results again showed that, at least for gunfire sounds (small arms), the penalty is level dependent. The drawing of firm conclusions, however, was hampered by a relatively large bias in the adjustments. In addition, the overall size of the penalty was lower than obtained in previous rating experiments. The question about the relevance of the level-dependent penalty was reopened in experiment 3 by applying the method of paired comparison. The results confirm the previous findings obtained with the rating experiments: For gunfire sounds at relatively low indoor Leq values, a penalty of about 10 dB is required, and a penalty lower than 5 dB can be applied only in conditions with rather high sound exposure. The results further showed that especially at indoor Leq values higher than about 45 to 50 dB(A), application of a negative penalty may become relevant for specific sounds such as those produced by the 0.50-in. machine gun. Consequently, acoustic measures from which to predict the value of the penalty are highly needed.
Selective reflectivity of viscoelastically coated plates in water
Authors: Strifors Hans C. , Gaunaurd Guillermo C.
Published: October 2005

A detailed study of the reflection of a plane acoustic continuous wave incident on a fluid-loaded elastic plate is presented. The purpose of the work is to determine and describe how, and how much, the reflection selectively is reduced by covering the plate with an ideally bonded viscoelastic coating. The equations of acoustics, elastodynamics, and viscoelastodynamics govern the behavior of the external fluid, the elastic plate, and the absorbing coating, respectively. By means of a recently developed viscoelastic formulation that can account for as many relaxation time constants as is physically required to model the dynamic response of the coating, the losses in the absorber can be determined. The absorbing layer can be homogeneous or inhomogeneous, with inclusions/perforations or not. The formulation is based on a general, thermodynamically admissible form of linear, isotropic viscoelasticity. Combining it with the solution of a suitably posed boundary-value problem for the bilaminar plate, the reflection (or transmission) coefficient for the coated structure is easily constructed. A number of calculated plots for the echo reduction levels and their associated phase shifts are plotted versus frequency in a variety of situations in wide bands. The results agree well with measurements reported earlier and with the prediction—obtained by other methods—that the echo reduction is greatest at the eigenfrequencies of the resonating air-filled cavities often placed within the viscoelastic layer. The procedure is useful to assess the effectiveness of the coating in reducing the structure’s reflectivity within certain selected frequency bands.
Near-field acoustic holography for an axisymmetric geometry: A new formulation
Authors: Sarkissian Angie
Published: October 2005

Near-field acoustic holography has recently been extended to nonseparable coordinate systems by applying the boundary elements method. The formulation currently implemented applies singular value decomposition to treat the presence of evanescent waves in the near field of the structure. A new method is introduced for an axisymmetric geometry that is better suited for broadband data than the singular value decomposition algorithm, enabling reduced computation time and providing a new expansion for the surface field with a set of functions that can be expressed as real functions, independent of frequency and independent of the choice of a measurement surface. The method is tested on numerically generated data.
Anisotropy of the ultrasonic attenuation in soft tissues: Measurements i
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Authors: Mottley Jack G. , Miller James G.
Published: October 2005

This study was designed to measure the ultrasonic attenuation within phantoms and tissue samples over a broad bandwidth and at many angles of incidence with respect to intrinsic orientations in order to elucidate both the frequency and angular dependence of the attenuation coefficient. Significant angular dependence, or anisotropy, of the attenuation was observed in canine myocardium (maximum to minimum ratio: 2.2 to 1) and a tissue mimicking phantom of oriented graphite fibers in gelatin (max to min: 2 to 1). In control studies, insignificant anisotropy was observed in the attenuation in canine liver samples and phantoms with graphite powder suspended in gelatin. Comparisons of the magnitude of variations of the oriented-fiber phantom to that predicted by a viscous relative motion model are presented.
English consonant recognition in noise and in reverberation by Japanese and American listeners
Authors: Takata Yoji , Nábělek Anna K.
Published: October 2005

English consonant recognition in undegraded and degraded listening conditions was compared for listeners whose primary language was either Japanese or American English. There were ten subjects in each of the two groups, termed the non-native (Japanese) and the native (American) subjects, respectively. The Modified Rhyme Test was degraded either by a babble of voices (S/N=−3 dB) or by a room reverberation (reverberation time, T=1.2 s). The Japanese subjects performed at a lower level than the American subjects in both noise and reverberation, although the performance difference in the undegraded, quiet condition was relatively small. There was no difference between the scores obtained in noise and in reverberation for either group. A limited-error analysis revealed some differences in type of errors for the groups of listeners. Implications of the results are discussed in terms of the effects of degraded listening conditions on non-native listeners’ speech perception.
Temporal decline of masking and comodulation detection differences
Authors: McFadden Dennis , Wright Beverly A.
Published: October 2005

Comodulation detection differences (CDDs) were studied using flanking bands that were either gated simultaneously with the signal band (burst) or gated at varying times prior to signal onset (fringed). Used for these experiments were a signal band centered at 1250 Hz and four flanking bands centered at 450, 850, 1650, and 2050 Hz; all bands were 100 Hz wide. In different conditions, the temporal envelope of the signal band was either the same as (correlated), or different from (uncorrelated), the common envelope of the four flanking bands, or the temporal envelopes of all of the bands were different (all-uncorrelated). For 8 of the 13 listeners, signal detectability improved by as much as 25 dB as the temporal fringe of the flanking bands was increased from 5 to about 700 ms. This temporal decline of masking was similar, but not identical, for the correlated, uncorrelated, and all-uncorrelated conditions. Results of this sort are reminiscent of several related findings that have been attributed to auditory adaptation or enhancement, or to a temporally developing critical-band filter. The other 5 of the 13 listeners were generally more sensitive than the majority, and they showed little or no improvement in detectability as fringe duration was varied. Large individual differences of this sort are not uncommon in the adaptation and comodulation literatures. As signal duration was changed from 50 to 240 ms, temporal integration was less in the correlated condition than in the uncorrelated condition, thereby producing a larger CDD with the longer signal. When the fringe followed the observation interval instead of preceding it, the results were equivocal because detectability improved for the majority of subjects and worsened for the minority. In follow-up experiments, different subsets of these four flanking bands were used. When temporal gaps of varying duration were inserted into the flanking band(s) immediately prior to the observation intervals, it was found that a temporal gap as long as 355 ms was not sufficient to reset the mechanisms underlying the temporal decline of masking.