bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of phoneme class and duration on the acceptability of temporal modifications in speech
Authors: Kato Hiroaki , Tsuzaki Minoru , Sagisaka Yoshinori
Published: July 2002

Human subjective acceptability of durational distortions in speech segments or portions is significantly affected by various segmental and sequential properties, e.g., the vowel color and temporal position in a word [Kato et al., J. Acoust. Soc. Am. 101, 2311–2322 (1997); 104, 540–549 (1998)]. The current study focused on the effects of phoneme class and original duration of speech portions in isolated words. In experiment 1, the effect of four classes of phoneme, i.e., vowel, nasal, voiceless fricative, and silent closure, on the acceptable modification range was tested. Six listeners evaluated the temporal acceptability of each of 49 words where one of the steady-state portions was subjected to durational modification from −75 ms (for shortening) to +75 ms (for lengthening) in 7.5-ms steps. The results showed that the listeners’ acceptable modification ranges were narrowest for vowels, and widest for voiceless fricatives and silent closures, with nasals in between. The mean acceptable ranges for the least vulnerable phoneme class, i.e., voiceless fricative and silent closure, reached 143% or more of that for the most vulnerable class, i.e., vowel. The observed variation in the acceptable modification range due to the different phoneme class was highly correlated with the inherent loudness in each phoneme class. A larger inherent loudness yielded a narrower acceptable range. Experiment 2 tested the effect of the original, as produced, duration of steady-state speech portions using 30 words where the factors of phoneme class and original duration were designed in a factorial way. The results showed that the original durations affected the listeners’ absolute acceptable ranges; the ranges were narrower for shorter original durations. There was a significant interaction between the factors of phoneme class and original duration. The effect of the original duration was larger for vowels than for fricatives. This interaction could be accounted for by the difference in the temporal structure spanning beyond the modified portion itself.
Learning to perceive pitch differences
Authors: Demany Laurent , Semal Catherine
Published: July 2002

This paper reports two experiments concerning the stimulus specificity of pitch discrimination learning. In experiment 1, listeners were initially trained, during ten sessions (about 11 000 trials), to discriminate a monaural pure tone of 3000 Hz from ipsilateral pure tones with slightly different frequencies. The resulting perceptual learning (improvement in discrimination thresholds) appeared to be frequency-specific since, in subsequent sessions, new learning was observed when the 3000-Hz standard tone was replaced by a standard tone of 1200 Hz, or 6500 Hz. By contrast, a subsequent presentation of the initial tones to the contralateral ear showed that the initial learning was not, or was only weakly, ear-specific. In experiment 2, training in pitch discrimination was initially provided using complex tones that consisted of harmonics 3–7 of a missing fundamental (near 100 Hz for some listeners, 500 Hz for others). Subsequently, the standard complex was replaced by a standard pure tone with a frequency which could be either equal to the standard complex’s missing fundamental or remote from it. In the former case, the two standard stimuli were matched in pitch. However, this perceptual relationship did not appear to favor the transfer of learning. Therefore, the results indicated that pitch discrimination learning is, at least to some extent, timbre-specific, and cannot be viewed as a reduction of an internal noise which would affect directly the output of a neural device extracting pitch from both pure tones and complex tones including low-rank harmonics.
Sources of DPOAEs revealed by suppression experiments, inverse fast Fourier transforms, and SFOAEs in impaired ears
Authors: Konrad-Martin Dawn , Neely Stephen T. , Keefe Douglas H. , Dorn Patricia A. , Cyr Emily , Gorga Michael P.
Published: July 2002

DPOAE sources are modeled by intermodulation distortion generated near the f2 place and a reflection of this distortion near the DP place. In a previous paper, inverse fast Fourier transforms (IFFTs) of DPOAE filter functions in normal ears were consistent with this model [Konrad-Martin et al., J. Acoust. Soc. Am. 109, 2862–2879 (2001)]. In the present article, similar measurements were made in ears with specific hearing-loss configurations. It was hypothesized that hearing loss at f2 or DP frequencies would influence the relative contributions to the DPOAE from the corresponding basilar membrane places, and would affect the relative magnitudes of SFOAEs at frequencies equal to f2 and fDP. DPOAEs were measured with f2=4 kHz, f1 varied, and a suppressor near fDP. L2 was 25–55 dB SPL (L1=L2+10 dB). SFOAEs were measured at f2 and at 2.7 kHz (the average fDP produced by the f1 sweep) for stimulus levels of 20–60 dB SPL. SFOAE results supported predictions of the pattern of amplitude differences between SFOAEs at 4 and 2.7 kHz for sloping losses, but did not support predictions for the rising- and flat-loss categories. Unsuppressed IFFTs for rising losses typically had one peak. IFFTs for flat or sloping losses typically have two or more peaks; later peaks were more prominent in ears with sloping losses compared to normal ears. Specific predictions were unambiguously supported by the results for only four of ten cases, and were generally supported in two additional cases. Therefore, the relative contributions of the two DPOAE sources often were abnormal in impaired ears, but not always in the predicted manner.
Gender differences in vocal fold contact computed from electroglottographic signals: The influence of measurement criteria
Authors: Higgins Maureen B. , Schulte Laura
Published: July 2002

EGGW is a phonatory parameter that can be derived from electroglottographic (EGG) signals and used to infer the relative degree of vocal fold contact. Vocal fold models predict that men will exhibit medial bulging of their vocal folds during phonation but women will not. These models lead us to expect gender differences in the magnitude of EGGW. Nevertheless, significant gender differences in EGGW for adults with normal voices have not been documented in previous studies when EGGW was computed from criterion lines placed at 25%–40% of the amplitude of the uninverted EGG wave form. We hypothesized that EGGW would better reflect gender differences in vocal fold adductory patterns if EGGW was computed from portions of the wave form that were associated with more vocal fold contact. EGGW was measured for seven men and seven women with normal voices. When EGGW was computed from segments of the wave form that were associated with relatively greater vocal fold contact (i.e., using criterion levels of ⩾55%), findings were consistent with the gender-specific adductory patterns that have been proposed from vocal fold models. Guidelines for appropriate placement of criterion lines when computing EGGW are discussed.
A simple formula for the Lamb modes in a plate
Authors: Ahmad Faiz
Published: July 2002

The dispersion relation for the Rayleigh–Lamb modes in an elastic plate can be replaced by a simpler equation, which admits exact solution. The approximation is valid for almost all modes when the phase velocity is between cT and cL.
The effects of turbulent intermittency on scattering and estimates for the degree of saturation
Authors: Norris David E. , Wilson D. Keith
Published: July 2002

Turbulent fluctuations in atmospheric wind and temperature fields are observed to be erratic in time; strong activity is typically interspersed with periods of relative calm. This property, referred to as turbulent intermittency, has an observable effect on the statistics of scattered acoustic signals. For fully saturated scattering, large intensity deviations about the mean result in a divergence from log-normal intensity probability density functions (pdfs) typically used to describe such statistics. Previous studies have developed the theory to predict the intensity pdf’s that account for both turbulent intermittency and the degree of saturation [Norris et al., J. Acoust. Soc. Am. 109, 1871–1880 (2001); Wilson et al., J. Acoust. Soc. Am. 99, 3393–3400 (1996)]. The new formulation with intermittency is compared to the generalized gamma pdf previously proposed for propagation in random media. It is also compared to data collected over a 140 m line-of-sight path at 110 to 525 Hz. Experimental characterization of the pdf parameters relating to intermittency and signal saturation is attempted with partial success. Strength/diffraction parameters and complex signal moments are computed to further define the scattering effects as a function of frequency and help identify limitations in the theory.
A comparison of variable structure control strategy to classical control strategies for active vibration control of distributed structures
Authors: Pan Jiaqiang , Pan Shuwen
Published: July 2002

Independent Modal Space Control (IMSC) is known as an essential method of active vibration control of distributed elastical structures. However, Meirovitch, who advanced the method at the beginning of the 1980s, and other researchers have only investigated modal control law and control performance due to employing classical linear control strateries (e.g., pole allocation, optimal control, etc.) since the 1980s. In this study, authors theoretically and experimentally investigate the modal control law and control performance as using a nonlinear control strategy called variable structure control (VSC) in IMSC of the distributed structures, and then give a comparison of them to the results from using classical control strategies. Besides strong stablity robustness of VSC, the theoretical analysis also shows that, when the sensor–actuator couples employed are less than the number of the modes one desires to control, use of VSC can efficiently avoid the control spillover that often happens at residual modes. For active vibration control of the elastical structures with the classical control strategies, the control spillover usually is a difficult problem to deal with. [Work supported by Zhejiang STPF, PROC.]
Robust wideband matched-field processing with a short vertical array
Authors: Czenszak Stephen P. , Krolik Jeffrey L.
Published: July 2002

This paper addresses the problem of matched-field passive localization of broadband underwater acoustic sources with a short vertical array. In previous work, incoherent averaging of narrow-band Bartlett ambiguity surfaces has been proposed to improve the robustness of matched-field processing (MFP) to environmental uncertainties. While computationally efficient, the effectiveness of this approach is dependent on the type of environmental mismatch present. In this paper, to provide robust source localization performance for short arrays, an alternative wideband MFP method is proposed which utilizes the fourth-order statistics of the data. The method is “coherent” in that it exploits cross-frequency dependencies in the random acoustic channel response. The proposed coherent wideband minimum variance method with environmental perturbation constraints (MV-EPC) consists of minimizing the squared output power of a beamformer subject to constraints defined across the signal band. The constraints are designed to provide robustness over an ensemble of random environmental realizations. Monte Carlo simulation results using a canonical shallow-water scenario indicate that the coherent wideband MV-EPC method yields improved probability of correct localization performance versus incoherent averaging of narrow-band Bartlett ambiguity functions with a short array above a threshold signal-to-noise ratio.
Determination of the higher-order elastic compliance constants of metals from measurements of the dependence of ultrasound velocity on stress
Authors: Kato Masaru , Sato Takuso , Ando Kazutaka
Published: July 2002

A new approach to describe the dependence of ultrasound velocity on stress in metals is presented to analyze the relation between acoustoelasticity which shows that the change of the ultrasound velocity depends on the stress in metals and the macroscopic characteristics of metals. It uses the effective higher-order elastic compliance constants which are determined from measurements of the ultrasound velocity in a metal. First, the nonlinear relation between stress and strain is described in terms of the second-, third-, and fourth-order elastic constants. Then, for the quasilongitudinal and quasitransverse waves which propagate in the symmetry planes of the metal, the ultrasound velocities in the statically stressed metals are presented by using these constants. They are explicitly derived as a function of the applied stress. The measurements of the dependence of ultrasound velocity on the applied stress due to the uniaxial compression in an aluminum alloy are performed and their results show the nonlinear dependence on the applied compressive stress. Finally, on the basis of the dependence, the effective elastic and elastic–plastic constants are determined by means of the least-squares method and the nonlinear acoustoelastic contribution to the deformation in the metal is discussed through the determined effective constants.
Predicting developmental shifts in perceptual weighting schemes
Authors: Nittrouer Susan , Miller Marnie E.
Published: July 2002

Recent models of developmental changes in speech perception suggest that the weights assigned to acoustic properties change as children gain experience with a native language. Empirical evidence supports this position, but few suggestions have been offered as to what guides this shift. These three experiments were designed to improve our ability to predict how perceptual weighting schemes change with development. The specific hypothesis explored was twofold: (1) the weight assigned by adults to any one acoustic property differs across phonetic environments according to how informative that property is in each environment; and (2) the weight assigned by children to any one acoustic property differs less across phonetic environments because children have not fully learned the patterns of covariation between phonetic informativeness and environment for each property. Experiment 1 replicated previous findings of age-related differences in the weights assigned to noise spectra and formant transitions in labeling of syllable-initial fricatives (/s/ or /∫/). In experiment 2 the variation in F3-onset frequency associated with place of fricative constriction was eliminated. This property differs more (i.e., is more informative) in /u/ than in /ɑ/. Accordingly adults’ transition effect was reduced more for /u/ than for /ɑ/ from experiment 1. Children’s transition effect was similarly reduced across vowel environments. In experiment 3, F3-onset frequency was appropriately manipulated for both vowels, and adults transition effect increased more for /u/ than for /ɑ/ from experiment 2. The increase in children’s transition effect was more similar across vowels. We conclude that the children had not fully learned how information provided by F3 transitions varies across /ɑ/ and /u/ environments, and suggest that developmental weighting shifts may be guided by children learning the relation between phonetic informativeness and environment.
Calibration methods of voltage-to-distance function for an electromagnetic articulometer (EMA) system
Authors: Kaburagi Tokihiko , Honda Masaaki
Published: July 2002

In electromagnetic articulometer (EMA) systems, the relationship between the voltage of the received signal and the distance between the transmitter and receiver coils is represented by a voltage-to-distance (VD) function. This paper describes an adaptive calibration method for determining unknown parameters in the VD function in which the parameters are determined using automatically selected local calibration data. This method is compared with the conventional fixed method in which the parameters are computed from calibration data covering the entire measurement area. Experimental results show that the measurement error of the adaptive method is 0.106 mm for a 14×14-cm measurement area and is less than half of that in the fixed method. In addition, this error is the same as that when the region of the receiver position is restricted to a 4×4-cm local area in the fixed method.
Bounds and approximations for elastic wave speeds in cubic crystals
Authors: Zuo Q. H. , Hjelmstad K. D.
Published: July 2002

Unlike an isotropic elastic medium, the wave speeds in an anisotropic medium depend on the direction of wave propagation. In this paper, bounds are developed on the speeds of waves propagating along an arbitrary direction in a cubic crystal through an additive split of the acoustic tensor into two parts, the eigenproperties of which are trivial to determine. The bounds are obtained by applying the minimax property of eigenvalues. Linear estimates of the wave speeds are obtained from a first-order expansion of the eigenvalues of the acoustic tensor, with respect to an anisotropy index, about the value of that index for which anisotropy vanishes.
Comments on “Analysis of the numerically implemented angular spectrum approach based on the evaluation of two-dimensional acoustic fields. Part I and Part II” [J. Acoust. Soc. Am. 99, 1339–1348, 1349–1359 (1996)]
Authors: Assaad Jamal , Rouvaen Jean-Michel
Published: July 2002

The aim of this Comment is to show that, when the normal velocity of the transducer is no longer constant, the algorithm that has been recently proposed by Wu et al. [J. Acoust. Soc. Am. 99, 1339–1348 for Part I and 1349–1359 for Part II (1996)] cannot eliminate aliasing nor remove the phase error in the angular spectrum. In fact, in recent articles, Wu et al. proposed and used a new numerical algorithm for eliminating the aliasing in the spectrum. Moreover, they have shown that the phase error can be easily removed. In their investigation they used a planar transducer and linear array. To show the effectiveness of their algorithm, the normal velocity of the planar transducer or of the elementary transducers (in the case of the array) has been supposed constant.
Vibration and wave localization in a nearly periodic beaded string
Authors: Óttarsson Gisli , Pierre Christophe
Published: July 2002

The dynamics of an exact, linear model of a string with attached beads are examined. A study of the perfectly periodic system is performed using a transfer matrix formulation. A closed-form solution for the natural frequencies of the finite system is obtained. The relationship between natural frequencies and the passbands and stop bands of propagating waves is studied. The effect of random disorder of (a) bead spacing and (b) bead mass is examined and interesting, fundamental differences are observed. In the case of bead-spacing disorder both weak and strong localization occur, whereas bead-mass disorder only causes weak localization. Localization, the spatial confinement of vibration energy due to periodicity breaking disorder, is quantified by the localization factor. Analytical approximations of the localization factor are derived, in the limits of large and small coupling to disorder ratios. The results are verified through Monte Carlo simulations. The natural frequencies and modes of the disordered system are examined. A dispersion of the natural frequencies is evidenced, presented as a curve veering phenomenon. The existence of localized mode shapes is demonstrated.
Influence of contralateral noise on distortion product latency in humans: Is the medial olivocochlear efferent system involved?
Authors: Giraud Anne Lise , Wable Jocelyne , Chays André , Collet Lionel , Chéry-Croze Sylviane
Published: July 2002

To test the hypothesis of temporal modifications of cochlear responses when medial efferents are activated, otoacoustic emission latencies were estimated in 16 normal human subjects, in the presence and absence of a contralateral broadband noise, using measurements of the phase of the 2f1−f2 distortion product (group latency method). Significant decrease in the latency of lower frequency (0.8–2.7 kHz) emissions was found in the presence of increasing levels of contralateral sound, and this effect disappeared when the primary-tone levels increased to 60 dB SPL. To ensure that effects were not attributable to mechanisms involving middle ear structures, susceptible to activation by contralateral sound, latency measures were performed in seven subjects whose efferents were severed during a vestibular neurotomy and in two subjects with paralyzed stapedial muscle. Results in patients were compared to those obtained in three surgical control patients with intact efferent bundle, and in eight other normal subjects. All the subject groups exhibited a decrease in latency under contralateral sound except the patients with the severed efferent system who showed increased latencies.
Two-channel resonant scattering theory: Application to an absorbing elastic cylinder
Authors: Franklin H. , Conoir J.-M. , Izbicki J.-L.
Published: July 2002

The scattering of a plane sound wave normally incident on an absorbing elastic cylinder immersed in water is investigated theoretically. Because of the loss of acoustic energy due to absorption, the unitarity condition of the usual S matrix arising from the classical resonant scattering theory fails. However, it is shown that this unitarity condition can still be met by constructing a new S matrix which is nondiagonal. This construction is analogous to the multichannel scattering theory of particle physics. Computations are performed considering an absorbing elastic cylinder in order to check the validity of the theory.
Discrimination of temporal asymmetry in cochlear implantees
Authors: Lorenzi Christian , Gallégo Stéphane , Patterson Roy D.
Published: July 2002

Several studies have recently demonstrated that normal-hearing listeners are sensitive to short-term temporal asymmetry in the envelopes of sinusoidal or noise carriers. This paper presents a study in which cochlear implantees were presented trains of current pulses with temporally asymmetric envelopes through one channel of an implant that stimulates the auditory nerve directly, thereby bypassing cochlear processes. When the level of the stimuli was adjusted to fit their audibility range, the implantees were able to discriminate temporal asymmetry over a much wider range than normal-hearing listeners. The results suggest that the perception of temporal asymmetry is limited by compression in the normal cochlea.
The spatial inhomogeneity of pressure inside a violin at main air resonance
Authors: Vandegrift Guy , Wall Eccles
Published: July 2002

The fluctuating pressure inside a violin is investigated at the A0 (main air) resonance, under the assumption that the walls are kept rigid. Three effects are shown to contribute to a reduction in the fluctuating pressure near the violin’s f-holes. The strongest effect arises from a tendency to form a standing wave within the relatively long, thin shape of the upper bout. A second and smaller effect arises from the violin’s nonuniform shape, and is modeled by treating the upper bout as an acoustical waveguide with nonuniform cross section. A third effect is associated with the Green’s function of an acoustical radiator, and will significantly reduce the fluctuating pressure in the immediate vicinity of the violin’s f-hole. Experimental verification of the theory is obtained by measuring the fluctuating pressure inside a rectangular box, with the resonance being driven by a small loudspeaker located outside the aperture.
Wave propagation in a pyroelectric cylinder of inner and outer arbitrary shape
Authors: Paul H. S. , Nelson Vazhapadi K.
Published: July 2002

The wave propagation in a long pyroelectric cylinder of crystal class 6 with inner and outer irregular shape is considered. The frequency equation has been derived for the traction free, earth connected, and thermally insulated surfaces. The boundary conditions at the arbitrarily shaped boundaries are satisfied using the Fourier series expansion collocation method. The longitudinal and flexural vibrations of barium titanate ceramic, which belongs to the (6 mm) class, have been analyzed numerically. The numerical results in the case of elliptical and cardioidal cross sections with an elliptical cavity are tabulated and are presented graphically.
Sound amplification by stimulated emission of radiation in nonlinear mode
Authors: Zavtrak S. T. , Volkov I. V.
Published: July 2002

The operation of the sound amplification by stimulated emission of radiation in the nonlinear mode is considered. Liquid with gas bubbles serves as an active medium. Pumping is produced by alternating electric field. The amplification of the useful wave in the plane resonator is investigated analytically.
Closed form solutions to the vibroacoustic response of strip structures
Authors: Ting Carina , Shen I. Y.
Published: July 2002

This paper presents some closed form expressions for the radiated power from flat elastic radiating strip structures of infinite length and finite width in an ambient light acoustic medium. New analytical expressions for the structural displacements, the wave number transforms of the structural displacements, the far-field pressure, and the total radiated sound power associated with an arbitrary strip that has been subjected to constant frequency loads including concentrated loads, boundary loads, or incident plane pressure waves are developed through the method of distributed transfer functions. With the exception of the radiated power from a structure subjected to a plane pressure wave, all of the expressions obtained are in closed form. The solutions presented are independent of the specific differential equations and boundary conditions governing the structure. An example analysis of a structure consisting of a bare aluminum strip with an active control scheme using boundary actuation that is subjected to an incident plane pressure wave is performed to illustrate the advantages of the new solutions.
The use of an array to explain the sound characteristics of secondary small plate tones produced by the impingement of an axisymmetric choked jet
Authors: Henderson Brenda , Powell Alan
Published: July 2002

The secondary small plate tones, referred to as S2 tones by Henderson and Powell [J. Sound Vib. 168, 307–326 (1993)], occur over a more limited range of pressures and nozzle-to-plate spacings than do the primary small plate tones [see B. Henderson and A. Powell, J. Acoust. Soc. Am. 99, 153–162 (1996)] but are still quite intense. Secondary tones are usually produced when plates are positioned near the location of the second cell ending in the free jet. Their power spectra usually contain a single discrete peak, the fundamental frequency, although occasionally the first harmonic is also present. Timed shadowgraph photographs indicate that the axial location and shape of the shock waves change randomly with time and are not connected with the production of tones. The motion of the shock wave is small in comparison to the motion observed for the primary small plate tones. Results of experiments conducted with a nozzle reflector indicate that these tones are part of a feedback loop to the nozzle. A four-element simple-source array with the array elements located at the approximate shock wave positions in the jet and the flow along the plate has been found to explain the measured frequencies and directivities.
Harmonic distortion in silicon condenser microphones
Authors: Pedersen Michael , Olthuis Wouter , Bergveld Piet
Published: July 2002

The nonlinear effects causing distortion in condenser microphones are investigated and modeled with special attention paid to microphones made with silicon micromachining technology. A model of the distortion, based on the quasistatic properties, is described and solved numerically using finite differences. The results of the model show that the distortion is mainly caused by both the inverse relation between the microphone capacitance and the deflection of the diaphragm, as well as the nonlinear electrostatic forces generated by the applied dc bias voltage. The results of the model are compared with measurement results on a silicon/polyimide microphone, and good agreement is found.
Generation of an enhanced acoustic streaming in a bounded space
Authors: Murata Yorinobu , Kimura Satoshi , Takei Seiji , Minagawa Keiji , Takimoto Jun-ichi , Koyama Kiyohito
Published: July 2002

A procedure to generate enhanced acoustic streaming into a bounded space has been studied. Under continuous ultrasound radiation, it was difficult to generate enhanced acoustic streaming in bounded space because of disturbances by reflected waves. Efforts were made to remove the disturbances by adjusting the repeat time of tone bursts of ultrasound. An experimental system has been developed for visualizing acoustic streaming. As a consequence of experiments, the streaming velocity in the bounded space has been enhanced by about 2.5 times by using a series of tone bursts of ultrasound.
Acoustic reverberation from a laboratory model of a shelf break
Authors: Li Saimu , Clay C. S.
Published: July 2002

Continental boundaries have a shallow sloping bottom that changes to a steeper slope. Our laboratory acoustic models (simulations) have (1) a 11° slope that changes to a 50.5° slope and (2) a 35° slope change to a 59° slope. The surface and bottom of the acoustic model are dry wall construction board. The source is a spark and the receiver is a small microphone. The Biot–Tolstoy exact time-domain solution was used. [I. Tolstoy and C. S. Clay, Ocean Acoustics (American Institute of Physics, New York, 1987), 2nd ed., Appendix 5, and C. Feuillade and C. S. Clay, J. Acoust. Soc. Am. 96, 501–514 (1994)]. The image-reflection and diffraction components depend on source and receiver locations. In model (1), source and receiver were within the 11° wedge and gave reverberations that were mainly from the 11° wedge. Source and receiver beyond the shelf break gave reverberations that were mainly from the 50° part of the model. In model (2), the source was up slope and receiver was near the break to observe diffractions. The finite number of arrivals (images) obeyed the Biot–Tolstoy rule. Experimental signals matched the theory in amplitudes and arrival times. Most reverberations were caused by multiple reflections in the wedge waveguide. The amplitudes of the image-reflection paths were an order of magnitude larger than the diffraction arrivals.
Automated evaluation of acoustic talker direction finder algorithms in the varechoic chamber
Authors: Morgan Dennis R. , Parikh Vipul N. , Coker Cecil H.
Published: July 2002

Acoustic talker direction finders have potential applications to camera pointing for teleconferencing and to microphone array beam steering for audio communication and voice processing systems. This paper describes a laboratory setup and computer interface that was developed for testing talker direction finder algorithms in the Bell Labs Varechoic chamber, a room with computer-controlled absorbing panels. The procedure exploits the full capability of the facility by automatically stepping through a sequence of room panel configurations, outputting a digital speech signal, running the processor, and collecting the data. The advantage of this technique is that it allows for testing under a multitude of different acoustic conditions in the same physical location, thereby enabling a general characterization of the algorithm under evaluation. As an example of the technique, we have implemented the Fischell–Coker talker direction finder algorithm using real-time C-code running on an SGI workstation, which is the same machine that is used to orchestrate the automatic testing procedure.
The effects of amplitude perturbation and increasing numbers of components in profile analysis
Authors: Lentz Jennifer J. , Richards Virginia M.
Published: July 2002

In a profile-analysis task, the effect of randomly perturbing the amplitudes of the components of multi-tone stimuli was studied in two experiments. In the first experiment, thresholds for a signal added in-phase to the central component of a standard were measured for different numbers of components in two conditions. In one condition thresholds were measured in blocks for six different “jagged” standards, and in another, thresholds were measured when one of the six standards was chosen randomly on a presentation-by-presentation basis. Regardless of condition, thresholds did not depend on the numbers of components and increased magnitude of perturbation increased thresholds. Moreover, the slope relating thresholds to number of components did not increase with increasing magnitude of perturbation. In the second experiment, the signal consisted of an increase in amplitude of the central components and a decrease in amplitude of the outer components of the standard (a stimulus type which has been shown to maximize the change in threshold with increasing number of components). The amplitudes of component tones were selected randomly on a presentation-by-presentation basis. Thresholds fell with increases in the number of components, but the slope relating thresholds to numbers of components did not change as the magnitude of perturbation increased. The latter result contrasts with that reported by Kidd et al. [J. Acoust. Soc. Am. 90, 1340–1354 (1991)].
Estimation of elastic moduli and bending stiffness of the anisotropic outer hair cell wall
Authors: Spector Alexander A. , Brownell William E. , Popel Aleksander S.
Published: July 2002

The outer hair cell makes both passive and active contributions to basilar membrane mechanics. The outer hair cell mechanics is strongly coupled to the elastic properties of the cell lateral wall. The lateral wall experiences both in-plane deformations and bending under physiological and experimental conditions. To characterize the outer hair cell wall, the model of an orthotropic cylindrical shell is used. The elastic constants of the wall are estimated by solving a set of three equations based on the analyses of three independent experiments. The first equation is derived from a new interpretation of the micropipet experiment; the other two are obtained from the axial loading and the osmotic challenge experiments. The two Young’s moduli corresponding to the longitudinal and circumferential directions and two Poisson’s ratios are estimated. The longitudinal, circumferential, and mixed modes of the bending stiffness are also estimated. The sensitivity of the derived constants to the variation of the cell axial stiffness, which has been measured by several independent groups, is examined. The new estimates are also compared with results obtained by using the assumption of the wall isotropy.
The effects of different envelope patterns and uncertainty for the detection of a tone added to SAM complex tonal maskers
Authors: Richards Virginia M. , Buss Emily , Tian Lijun
Published: July 2002

Thresholds for the detection of a tone added in-phase to the carrier of a fully modulated SAM tone were measured. In some conditions the signal was added to a single SAM tone, and in other conditions the signal was added to the sum of three or more SAM tones. Level equalization ensured that the addition of the tonal signal did not lead to increases in energy. When multiple SAM tone maskers were used, a small number of reproducible maskers were tested, each masker being composed of SAM tones with a variety of relative modulator phases. The maskers were either fixed across intervals and trials, roved across trials but fixed across intervals, or randomly chosen across both intervals and trials. The frequency separation between the signal-centered and off-frequency SAM tones was also varied. For small signal-centered/off-frequency SAM tone frequency separations, a separation ratio of 1.3, thresholds in the fixed condition depend on the relative modulator phases, and a simple mixture model reasonably predicted thresholds in the roving condition based on thresholds in the fixed condition for two of the three observers. For signal-centered/off-frequency SAM tone frequency separation factor of 1.68, effects of relative modulator phases were not obtained. Thresholds in the target-alone condition were generally superior to thresholds measured with the comodulated masker. Comodulated thresholds were better than target-alone thresholds only when level equalization was not used, and so the addition of the signal led to increases in level.
Relative intensity comparisons between a tone and spectrally remote noise: Effects of onset asynchrony
Authors: Hill Nicholas I. , Bailey Peter J.
Published: July 2002

The present experiment investigated the effect of onset asynchrony on listeners’ ability to make relative intensity comparisons between a 1-kHz tone and a band of noise high-pass filtered at 3 kHz. In the synchronous condition, the tone and noise were gated on and off simultaneously. In the two asynchronous conditions, either the tone was gated on before the noise or vice versa, both stimuli terminating simultaneously. In the sequential condition, the offset of the tone coincided with the onset of the noise. The task of the six listeners was to indicate in which of the two presentation intervals the level of the tone was incremented relative to that of the noise. To deter the use of strategies based on successive, within-channel level comparisons, the overall level of the stimuli was randomized on each presentation. For all listeners thresholds were lowest in the synchronous condition, and highest in the sequential condition, the difference ranging from approximately 7 to 18 dB (signal re: pedestal amplitude). Furthermore, five of the six listeners had significantly lower thresholds in the noise-leading condition than in the tone-leading condition, the average difference across listeners being approximately 5 dB. The results are discussed in terms of auditory grouping and the possible strategies available to the listeners.
The Rayleigh equations for a multi-sinusoidal periodic surface
Authors: Purcell Anthony
Published: July 2002

It was shown by Purcell [J. Acoust. Soc. Am. 100, 2919–2936 (1996)] that the Rayleigh equations in the Fourier domain for the reflection coefficients for scattering of a plane wave from a pressure-release sinusoid are valid if the maximum slope of the sinusoid Kd<0.6627. This current work finds the corresponding constraint sufficient for the validity of Rayleigh’s equations for a more general periodic surface consisting of a finite sum of sinusoids. The mathematical basis of the derivation of the Rayleigh equations from the Helmholtz integral formula is a Fourier series given by Oberhettinger. Unlike the single sinusoid case developed by Purcell (referenced above), the analysis of the general periodic surface given here requires an analytic continuation argument. In addition, a set of (infinite linear) equations of the “second kind” is derived for the reflection coefficients for the general periodic surface. This guarantees that the truncation solutions for the reflection coefficients converge and are unique. The matrix elements involved in these equations of the second kind require the numerical evaluation of a finite integral (a generalization of Bessel’s integral for the integer index Bessel functions) and all calculations required can be performed by desktop computing.
Dichotic presentation of speech signal using a critical filter bank for bilateral sensorineural hearing impairment
Authors: Chaudhari D. S. , Pandey P. C.
Published: July 2002

Sensorineural hearing-impaired listeners face a particular problem in view of a decrease in the frequency resolving capacity of an ear due to the spread of masking of frequency components by adjacent frequency components. Filtering a speech signal by a bank of critical band filters and adding signals from alternate bands for presenting to the two ears is likely to reduce the effect of the spread of masking along the cochlear partition, and thus may help in improving the speech intelligibility. This processing scheme has been implemented with 18 critical bands for experimental evaluation through listening tests. The scheme was found to be helpful in improving recognition scores and transmission of speech features in listening tests with normal hearing subjects with simulated sensorineural hearing loss. Listening tests were carried out using 12 vowel–consonants–vowel and consonant–vowel nonsense syllables presented in quiet (no masking noise), on ten subjects with mild to very severe sensorineural hearing loss. The stimulus response confusion matrices were analyzed using relative improvement in recognition scores and information transmission analysis. The relative improvement in recognition scores is up to 25%. Information transmission analysis indicated that the overall improvement is contributed to by improvements in transmission of the speech feature of voicing, place, and manner. The mean response time has also been found to decrease significantly.
Voice transmission through vibration pickups
Authors: Giua Paolo E.
Published: July 2002

Devices that pick up vibrations induced in the body by the speaker voice have been used in speech communication for many years in order to enhance intelligibility in noisy environments. This and other interesting applications seem to justify a study of this ‘‘accelerometric’’ speech in order to obtain useful correlations with the ‘‘microphonic’’ speech. Many factors seem to influence the voice spectrum of the accelerometric speech. A constant general factor is the low-pass filter effect of the acoustical bone conduction. But the main one seems to be the coupling of the voice to the bony transmission channel. This coupling is phoneme dependent. For instance, voiced stop consonants are more amplified than voiced fricatives, while vowels are modified according to their qualities. Moreover speaker features and accelerometer features are to be taken into account. The present results refer to an accelerometer inserted in the ear canal. Main features of this type of accelerometric speech are shown and intelligibility measurements as a function of speakers and their vocal effort are reported. An attempt to recover microphonic speech corrupted by noise by means of a simultaneous accelerometric speech is described.
Subjective versus objective intelligibility of sentences in listeners with hearing loss
Authors: Cienkowski Kathleen M. , Speaks Charles , McKee Amy S.
Published: July 2002

The relation between estimated intelligibility and correct key-word repetitions of sentences was examined in listeners with normal hearing and hearing loss. The ten lists of CID sentences [S. R. Silverman and I. J. Hirsh, Ann. Otol. Rhinol. Laryngol. 64, 1234–1245 (1995)] were arranged in two randomly ordered groups. Listeners were asked to complete two tasks: (1) rate the intelligibility of 50 sentences on a scale of 0% to 100%, (2) repeat each of the 50 sentences, which were scored as the number of key words repeated correctly. Sentences were presented at five signal-to-noise ratios, +6, +4, +2, 0, and −2 dB. The 0 dB S/N point was established by the method of adjustment using the revised speech intelligibility rating passages to reach a criterion of 50% intelligibility. Correlations of rated intelligibility and correct repetition of key words were 0.85 for listeners with normal hearing and 0.87 for listeners with hearing loss. These findings confirm earlier work [Speaks et al., J. Speech Hear. Res. 15, 590–602 (1972)] with listeners with normal hearing and demonstrate that listeners with hearing loss preserve the ability to rate intelligibility of speech.
Continuous assessment and modeling of speech transmission quality
Authors: Hansen Martin , Kollmeier Birger
Published: July 2002

This paper addresses the question of whether subjects are able to assess the perceived time-varying quality of speech material continuously. A method inspired by Hamberg and de Ridder [J. Opt. Soc. Am. A 12, 2573–2577 (1995)] is presented by which subjects continuously rate the perceived speech quality by moving a slider along a graphical scale. In this way, temporal variations in quality can be monitored quantitatively and differences between, for example, alternative speech transmission systems, can be analyzed in an informative way. The usability of this method is illustrated with an experiment in which different sequences of sentences with a total duration of 40 s were degraded in quality with a modulated noise reference unit. The modulation depth was varied with time and the subjects task was to assess the perceived quality. The results show that subjects can monitor speech quality variations closely with a delay of approximately 1 s. The subjective results are discussed in view of a psychoacoustically motivated objective speech quality measure [Hansen and Kollmeier, ICASSP ’97, 1387–1390 (1997)].
Coherence-based sub-band decomposition for efficient reverberation and noise removal in enclosed sound fields
Authors: Gonzalez-Rodriguez Joaquin , Ortega-Garcia Javier
Published: July 2002

The issue of speech enhancement in reverberant rooms has been extensively addressed. The use of sub-band decomposition through nested linear arrays has been shown to be very efficient for this task. Recently, the coherence/noncoherence nature of the sound field has been used to separate the wideband speech signal in two sub-bands, obtained from the sinc function that characterizes the diffuse field prediction for a given separation between microphones when many independent sources are present and the reverberation time is not too short. The processing scheme proposed here takes advantage of both ideas. After a sub-band decomposition from a linear log-spaced 15 microphone array, a further subdivision is made in each processing band, dividing in a coherent sub-band, where a Generalized–Sidelobe–Canceller is applied, and a noncoherent sub-band, where a Wiener postfilter is used, resulting in a total of six analysis sub-bands. Promising results have being obtained with room simulations (image method), and further results are being obtained with the Carnegie Mellon University (CMU) multichannel-recorded database. The authors thank Dr. Finn Jacobsen (Technical Univ. Denmark) for his fruitful discussions about spatial coherence, and Dr. Richard Stern (CMU, PA, USA) for the multichannel database. [Work supported by CICYT under Project TIC97-1001-C02-01.]
Synthesis of fricative sounds using an aeroacoustic noise generation model
Authors: Sinder Daniel J. , Krane Michael H. , Flanagan James L.
Published: July 2002

Results from speech synthesis with an aeroacoustic fricative source model are presented. The source model, which is implemented in the time domain, is based on Howe’s reformulation of the acoustic analogy [Howe, J. Fluid Mech. 71, 625–673 (1975)]. It specifies the source as a function of flow conditions and the geometry of the vocal tract downstream from a constriction where a turbulent jet is formed. This is accomplished by combining elements of aeroacoustic theory and a model for jet behavior with a traditional model for wave propagation in the vocal tract. Using this formulation, the source strength, impedance, and spectrum can be determined through post-processing. The fricative model is implemented in an articulatory speech synthesizer. Evaluation of the resulting synthesis is emphasized. Comparisons are made with physical experiments in static configurations. Additionally, speech fricatives are compared with natural speech as well as synthetic speech from other models. These comparisons are made in the frequency domain and through listening tests in which fricatives in V-C-V sequences are judged for naturalness and intelligibility. [Research supported by NSF/ARPA IRI-9314946 and ARPA DAST 63-93-C-0064.]