bluuebunny/crossref_metadata_2025 huggingface dataset:
Voice development under training with and without the influence of real-time visually presented biofeedback
Authors: Rossiter David , Howard David M. , DeCosta Mike
Published: October 2005

This paper describes an investigation into the developmental nature of the voice under training with and without the influence of real-time visually presented biofeedback. Two subjects who had not previously experienced any form of vocal training took six singing lessons. One was taught conventionally, while the other was taught with the aid of a system known as Acoustic and Laryngeal Biofeedback Enhancement Real Time (ALBERT). Real-time biofeedback was presented based upon measures of (i) larynx closed quotient (CQ), (ii) spectral amplitude in the singer’s formant frequency band relative to the spectral amplitude of the full band (ratio), and (iii) both parameters combined in a manner based upon previously observed correlations between them. Results indicate generally increased sound pressure levels (SPL) of acoustic output and generally consistent increases in the level of CQ and ratio across consecutive lessons for both subjects.
Control effort weighting in feedforward adaptive control systems
Authors: Rossetti D. J. , Jolly M. R. , Southward S. C.
Published: October 2005

Active control of noise and vibration in large dimensional complex systems is generally accomplished with adaptive feedforward control algorithms based on the steepest descent optimization approach. This paper examines the effects of incorporating control effort weighting into the cost function that is minimized by an adaptive control algorithm. When the plant matrix is rank-deficient, the least-squares solution to which the control algorithm converges is nonunique. In such situations, the control signals can drift with no change in performance. Small amounts of uniform control effort weighting can enforce a unique solution at the expense of decreased performance. A nonuniform form of control effort weighting is introduced that yields a unique solution without a performance penalty. With ill-conditioned systems, small amounts of effort weighting can provide significant reductions in the control signals with only a very small increase in residual error. A form of effort weighting is introduced for ill-conditioned systems based on the results for the rank-deficient case. Stability and robustness issues are examined for each form of weighting. It is shown that the nonuniform forms of control effort weighting can significantly diminish the trade-off between performance and robustness in the presence of plant model error.
Oblique scattering of an elastic wave from a multilayered cylinder in a solid. Transfer matrix approach
Authors: Huang W. , Wang Y. J. , Rokhlin S. I.
Published: October 2005

The scattering of an elastic wave obliquely incident on a multilayered cylinder in a solid is studied using a transfer matrix approach. Scattering of longitudinal and shear waves with arbitrary polarizations are considered. To facilitate the derivation of the solutions for scattering in the multilayered cylindrical system, a 6×6 transfer matrix is introduced for each cylindrical layer to relate the stresses and displacements on the inner and outer boundaries of that layer. A total transfer matrix relating the elastic field in the surrounding matrix to that in the cylinder core is obtained as a product of individual transfer matrices of intermediate layers. Numerical examples are given for a coated multiphase SiC fiber in a titanium matrix. Frequency and angle dependencies of specularly reflected and forward-scattered waves, and of the total scattering cross section, are calculated for different fiber-matrix interphase properties.
Effects of pinna position on head-related transfer functions in the cat
Authors: Young Eric D. , Rice John J. , Tong Samuel C.
Published: October 2005

To measure the effects of the pinna position on spectral sound localization cues, the head-related transfer function (HRTF) from the free-field to a point in the ear canal was measured for anesthetized cats with their pinnae in three positions: the relaxed, anesthetized position; pulled forward into an approximation of the ‘‘alert cat’’ posture; and pulled back. The general features of HRTFs are not changed by moving the pinna, although the mapping of particular HRTF features onto directions in space is changed. As an approximation, the pinna behaves like a fixed-shape sound collector, so that HRTFs shift with the pinna when it moves; however, pinna movement changes some quantitative details of HRTFs beyond what is predicted by this approximation. When viewed as directional gain, pinna movements serve to optimize listening conditions. However, when considering sound localization, pinna movements lead to ambiguities regarding source location. If pinna position is not incorporated into the computation, and spectral cues alone are used for localization, the ambiguity is about 60° in azimuth and 30° in elevation. Pinna movements produce similar azimuthal ambiguity in interaural level differences. Interaural time difference cues could be used to reduce the ambiguity in azimuth, but a knowledge of pinna position seems to be necessary to resolve ambiguities in elevation.
Elastic pulsed wave propagation in media with second- or higher-order nonlinearity. Part II. Simulation of experimental measurements on Berea sandstone
Authors: Van Den Abeele Koen E-A , Johnson Paul A.
Published: October 2005

The theoretical 1-D wave propagation model described in Part I is applied to laboratory data from dynamic propagating wave experiments on a 2-m-long cylindrical rod of Berea sandstone as previously reported by Meegan et al. [J. Acoust. Soc. Am. 94, 3387–3391 (1993)]. Using the iterative procedure, good agreement is obtained limiting model parameters up to cubic anharmonicity (i.e., two nonlinear terms proportional to β and δ in the stress-strain polynomial expansion). Both the data and simulations illustrate that nonlinear response is likely to occur even at extremely small strains (order 10−7). As generally expected for disordered materials, the resulting values for the nonlinear parameters are several orders of magnitude larger than those for intact (uncracked, noncompliant) materials. The values obtained for the dynamic nonlinearity parameters are discussed in relation to commonly obtained static and resonance results which suggest the need to include more complicated phenomena such as hysteresis in the theory.
Mutual interaction between a bubble and a drop in a sound field
Authors: Doinikov Alexander A.
Published: October 2005

The behavior of the radiative interaction force between a gas bubble and an immiscible liquid drop at separation distances comparable to their sizes is investigated. The wavelength of an incident sound field is assumed to be much larger than the distance between the centers of the particles concerned, which allows one to treat both the surrounding liquid and the one inside the drop as incompressible. Viscous effects are also neglected. The interaction force is expressed as an infinite series, the terms of which are found by means of recurrence formulas. Numerical examples show that at small separations between the bubble and the drop their mutual interaction can become rather complex, especially if the driving frequency is close to the natural frequencies of shape oscillations of the bubble or the drop. The most interesting result is that the interaction force can change, sometimes even twice, its sign as the separation between the bubble and the drop is shortened. This occurs in the case of a drop both denser and less dense than the surrounding liquid.
Active acoustic noise cancellation with audio signal enhancement based on an almost-symmetrical time-varying autoregressive-moving average model
Authors: Tong Wen , Plotkin Eugene I. , Swamy M. N. S.
Published: October 2005

The basic idea of active noise cancellation (ANC) is to generate a controllable secondary source which compensates a noise in a certain spatial region. In headset applications, it is desirable to generate a secondary source which cancels the acoustic noise field, while preserving the useful audio field. This requires that the cancellation algorithm possess an ability to differentiate between the useful audio signal and the cancellation residual at the secondary-sensor output. This is a formidable task for the conventional linear time-invariant filtering approach, since the Fourier spectra of acoustic noise and the audio signal occupy the same frequency bandwidth. In this paper, a two-sensor ANC scheme is presented with application to a noise-reduction headset. The active noise cancellation carried out is based on the concept of the separation of superimposed signals with complete overlapping spectra by using an almost-symmetrical time-varying autoregressive-moving average model (ASTV-ARMA). The significant advantages of our proposed selective noise cancellation approach are the cancellation of the undesirable noise field and the preservation of the useful audio wave field. Simulation results indicate that a noise reduction of over 30 dB can be achieved, thus resulting in a high-quality audio in the presence of a strong environmental acoustical noise.
Spatial periodicity in the cochlea: The result of interaction of spontaneous emissions?
Authors: van Hengel P. W. J. , Duifhuis H. , van den Raadt M. P. M. G.
Published: October 2005

In this study the results of simulations with a nonlinear macromechanical model of the human cochlea are presented. In this model it is possible to investigate the interactions between large numbers of spontaneous emissions. The focus of this study is on the effect of a local maximum in emission strength on its direct surroundings. The suppression that such an emitter causes depends on the distance between suppressor and suppressee in a strongly nonmonotonic manner. This nonmonotonicity leads to natural minimal distances between emission frequencies, without additional assumptions about the mechanics of the cochlea. The origin of this nonmonotonicity in the suppression lies in reflection of the generated energy at the stapes. The fact that these minimum distances correspond to distances observed between measured SOAE frequencies in adults, but not in newborns, suggests that the nonmonotonicity may play a role in the development of the cochlea in the early years of childhood.
A quantitative model of the ‘‘effective’’ signal processing in the auditory system. I. Model structure
Authors: Dau Torsten , Püschel Dirk , Kohlrausch Armin
Published: October 2005

This paper describes a quantitative model for signal processing in the auditory system. The model combines a series of preprocessing stages with an optimal detector as the decision device. The present paper gives a description of the various preprocessing stages and of the implementation of the optimal detector. The output of the preprocessing stages is a time-varying activity pattern to which ‘‘internal noise’’ is added. In the decision process, a stored temporal representation of the signal to be detected (template) is compared with the actual activity pattern. The comparison amounts to calculating the correlation between the two temporal patterns and is comparable to a ‘‘matched filtering’’ process. The detector itself derives the template at the beginning of each simulated threshold measurement from a suprathreshold value of the stimulus. The model allows one to estimate thresholds with the same signals and psychophysical procedures as those used in actual experiments. In the accompanying paper [Dau et al., J. Acoust. Soc. Am. 99, •••–••• (1996)] data obtained for human observers are compared with the optimal-detector model for various masking conditions.
Placement of observations for the efficient estimation of a psychometric function
Authors: Lam Chan F. , Mills John H. , Dubno Judy R.
Published: October 2005

Psychometric functions for different psychophysical tasks describe the relationship between physical stimuli and subjects’ responses. Although a psychometric function is of considerable value, characterizing the function is time consuming and, hence, is not carried out routinely in psychophysical experiments. A principal reason for the lack of efficiency in characterizing the psychometric function is the use of unimodal (e.g., Gaussian and uniform) sampling methods. As an alternative, a multimodal four-point sampling method is proposed. A psychometric function is then fitted to the four data points (each with several trials) to estimate the threshold and slope parameters of the psychometric function. Results from three examples demonstrate that a 60% savings in data-collection time can be achieved.
Some acoustic features of nasal and nasalized vowels: A target for vowel nasalization
Authors: Feng Gang , Castelli Eric
Published: October 2005

In order to characterize acoustic properties of nasal and nasalized vowels, these sounds will be considered as a dynamic trend from an oral configuration toward an [■]-like configuration. The latter can be viewed as a target for vowel nasalization. This target corresponds to the pharyngonasal tract and it can be modeled, with some simplifications, by a single tract without any parallel paths. Thus the first two resonance frequencies (at about 300 and 1000 Hz) characterize this target well. A series of measurements has been carried out in order to describe the acoustic characteristics of the target. Measured transfer functions confirm the resonator nature of the low-frequency peak. The introduction of such a target allows the conception of the nasal vowels as a trend beginning with a simple configuration, which is terminated in the same manner, so allowing the complex nasal phenomena to be bounded. A complete study of pole-zero evolutions for the nasalization of the 11 French vowels is presented. It allows the proposition of a common strategy for the nasalization of all vowels, so a true nasal vowel can be placed in this nasalization frame. The measured transfer functions for several French nasal vowels are also given.
Acoustic characteristics of less-masculine-sounding male speech
Authors: Avery Jack D. , Liss Julie M.
Published: October 2005

This study compared samples of less-masculine-sounding (LMS) and more-masculine-sounding (MMS) male speech to identify acoustic characteristics, other than fundamental frequency, that might contribute to the perception of these categories. In the first phase, audiorecorded speech samples provided by 35 males were presented to 35 female listeners in a paired-comparison perceptual experiment. Nineteen of the male speech samples were judged reliably to fall within the LMS or MMS categories. Within those 19 samples, 8 speakers (4 LMS and 4 MMS) exhibited similar distributions of habitual fundamental frequency values in connected speech and in sustained phonation. In the second phase of the experiment, various acoustic measures of these eight connected speech samples were conducted. Significant differences between measures of fundamental frequency contours, vowel formant midpoint values, and in the first, third and fourth spectral moments of two fricatives were revealed. These findings may be useful in creating stylized synthetic speech that varies on the dimension of masculinity, and they may have clinical relevance for patients wishing to modify the perception of masculinity invoked by their speech.
Consonant recognition for spectrally degraded speech as a function of consonant–vowel intensity ratio
Authors: Balakrishnan Uma , Freyman Richard L. , Chiang Yuan-Chuan , Nerbonne G. Patrick , Shea Kelly J.
Published: October 2005

Normal-hearing subjects’ recognition of spectrally degraded speech was evaluated under conditions in which the consonant–vowel (C–V) intensity ratio was modified. Subjects identified 22 consonants presented in an /■–Consonant–■/ format at suprathreshold and near threshold conditions. Prior to C–V ratio modification, the stimuli were processed to limit spectral information. In the suprathreshold experiment, stimuli were presented at the natural C–V ratio and at six modified C–V ratios. C–V ratio manipulations had dramatic effects on recognition scores for some groups of consonants. Scores for glides and sibilant fricatives increased with increasing C–V ratio, while scores for nasals and weak fricatives were best at low C–V ratios. Recognition scores for the stops and affricates were generally independent of C–V ratio. For nearly all consonants, changes in recognition scores as a function of C–V ratio were associated with changes in a general response bias toward those sounds. Performance was poor when the spectrally smeared VCVs were presented at low SN ratios in a second experiment. The influence of C–V ratio on percent correct scores was generally similar to the suprathreshold results, but consonant audibility, which was not a factor in the suprathreshold experiment, appeared to alter the effect of C–V ratio modification for some consonants.
Vowel discrimination in cats: Acquisition, effects of stimulus level, and performance in noise
Authors: Hienz Robert D. , Aleszczyk Cynthia M. , May Bradford J.
Published: October 2005

The ability of cats to discriminate accurately among different synthetic, steady-state vowels was examined across a range of stimulus levels and in background noise. Cats were trained to press and hold down a lever to produce a pulsed train of a standard vowel stimulus, and to release the lever only when a different vowel sound occurred. Five synthetic vowels were tested (/ε/, /æ/, /a/, /■/, and /■/) at levels of 30, 50, 70, and 90 dB SPL. In separate experiments, each of these vowels served in turn as the standard vowel. All cats discriminated among the vowels accurately, and in general performed at least as well at high stimulus levels as at low levels. Where differences in vowel discriminability occurred, they were correlated with the relative changes in first and second formant peaks. Cats appear to predominantly utilize upward frequency changes in either the first or second formants of the vowels to make the discriminations; downward formant changes produced considerably lower discrimination performances. In background noise, high vowel discriminability was still maintained at an average signal/noise ratio of −12.3 dB. Thus cats can discriminate among vowels at high signal levels and in background noise, despite the fact that the neural representations of vowels based on rate responses in the auditory nerve can be severely degraded under these conditions.
Time compression of M-sequence transmissions in a very long waveguide with a moving source and receiver
Authors: Heard Garry J. , Schumacher I.
Published: October 2005

The results of correlation processing of the Heard Island Feasibility Test (HIFT) M-sequence transmissions are presented in this paper. Phase modulated M-sequence signals, with a carrier frequency of 57 Hz, originating from the vicinity of Heard Island (Australia) were received by (Canadian Forces Auxiliary Vessel) CFAV ENDEAVOUR in the Northeast Pacific at a range of 17 400 km. The signals were beamformed, Doppler processed using a novel phase-tracking method, and correlated with replica sequences to yield information about the time-spreading of the multi-path arrivals and path stability. The signal-to-noise ratios (SNR) were very low, so that only a few of the HIFT transmissions could be used to obtain useful correlation results; however, the results indicate that the arrival spread was of the order of 28 s, and that propagation paths were stable for periods of minutes despite the motion of both the towed source and towed receiver.
Physical mechanisms to explain the observed features of ambient noise in shallow water
Authors: George Jacob
Published: October 2005

Possible physical mechanisms for two features of ambient noise observed in shallow water in the Pacific are explored. These features are (a) non-Gaussian distribution of the probability density function, and (b) the fact that probability density function plots whose X scales are normalized by the standard deviation of the power decibel levels of each hydrophone are independent of depth. The results of the analysis show that variation in multipath interference of distant shipping noise is an unlikely cause of the observed features. Predictions based on source depth variations caused by wave action when a dominant noise source (such as the hull of a large ship) is located close to the surface agree with the observed features. A parametric match to the experimental probability density functions has been found with the use of non-Gaussian random noise. Future studies are recommended to explore the distributions in other oceanic regions and for other frequency bands, and to identify the underlying ambient noise mechanisms.
The energy partition of underwater sparks
Authors: Roberts Randy M. , Cook Jeffrey A. , Rogers Robert L. , Gleeson Austin M. , Griffy Thomas A.
Published: October 2005

Underwater sparks have long been used by the geophysical prospecting community as a source of intense low-frequency sound. While bubble hydrodynamic models are well developed, the mechanism of transferring energy from the thermal power input, through the various energy conversion channels, to the work done by the bubble has not been adequately studied. In this work an ab initio model of the bubble dynamics, including blackbody ablation, ionization, dissociation, and radiative transport, is developed. This model is a first step in enumerating the important physical mechanisms within bubbles generated by underwater sparks. The predictions of this model are compared with experimental results. Experimental work is still needed to validate the model, and to determine if and how model parameters related to actual physical parameters and measurable effects.
Compensation to articulatory perturbation: Perceptual data
Authors: Baum Shari R. , McFarland David H. , Diab Mai
Published: October 2005

The perceptual adequacy of vowels, stop consonants, and fricatives produced under conditions of articulatory perturbation was explored. In a previous study [McFarland and Baum, J. Acoust. Soc. Am. 97, 1865–1873 (1995)], acoustic analyses of segments produced in two subtests (immediate compensation and postconversation) revealed small but significant changes in spectral characteristics of vowels and consonants under bite-block as compared to normal conditions. For the vowels only, adaptation increased subsequent to a period of conversation with the bite block in place, suggesting that compensation may develop over time and that consonants may require a longer period of adaptation. The present follow-up investigation examined whether the acoustic differences across conditions were perceptually salient. Ten listeners performed an identification and a quality rating task for stimuli from the earlier acoustic study. Results revealed reductions in identification scores and quality ratings for a subset of the vowels and consonants in the bite-block conditions relative to the normal condition in the immediate compensation subtest. In the postconversation subtest, quality ratings for the fricatives in the bite-block condition remained low as compared to those in the normal condition. Perceptual results are compared to the previous acoustic data gathered on these stimuli.
Speech formant frequency and bandwidth tracking using multiband energy demodulation
Authors: Potamianos Alexandros , Maragos Petros
Published: October 2005

In this paper, the amplitude and frequency (AM–FM) modulation model and a multiband demodulation analysis scheme are applied to formant frequency and bandwidth tracking of speech signals. Filtering by a bank of Gabor bandpass filters is performed to isolate each speech resonance in the signal. Next, the amplitude envelope (AM) and instantaneous frequency (FM) are estimated for each band using the energy separation algorithm (ESA). Short-time formant frequency and bandwidth estimates are obtained from the instantaneous amplitude and frequency signals; two frequency estimates are proposed and their relative merits are discussed. The short-time estimates are used to compute the formant locations and bandwidths. Performance and computational issues of the algorithm are discussed. Overall, multiband demodulation analysis (MDA) is shown to be a useful tool for extracting information from the speech resonances in the time–frequency plane.
Microphone-array localization error estimation with application to sensor placement
Authors: Brandstein Michael S. , Adcock John E. , Silverman Harvey F.
Published: October 2005

This paper presents a means for predicting the error region associated with a speech-source location estimate obtained from a set of microphones in a room environment. The error predictor presented is derived assuming a specific source-sensor geometry consisting of pairs of closely spaced sensors for which a delay estimate associated with the potential source has been evaluated. The accuracy of the predictor is evaluated through a set of Monte Carlo simulations and an application of the predictor to microphone-array design in the context of a video-conferencing scenario is presented.
Statistics of the log-compressed echo envelope
Authors: Dutt Vinayak , Greenleaf James F.
Published: October 2005

Log compression of A lines to produce B-scan images in clinical ultrasound imaging systems is a standard procedure to control the dynamic range of the images. The statistics of such compressed images in terms of underlying scatterer statistics have not been derived. The statistics are analyzed for partially formed speckle using a general K distribution model of envelope statistics to derive the density function for the log-compressed envelope. This density function is used to elucidate the relation between the moments of the compressed envelope, the compression parameters, and the statistics of the scatterers. The analysis shows that the mean of the log-compressed envelope is an increasing function of both the backscattered energy and the effective scatterer density. The variance of the log-compressed envelope is a decreasing function of the effective scatterer density and is independent of the backscattered energy.
Optimization of the performance of thermoacoustic refrigerators applying the short stack boundary layer approximation.
Authors: Wetzel M. , Herman C.
Published: October 2005

A systematic approach to optimize the performance of thermoacoustic refrigerators by using the COP (coefficient of performance) is presented. For this purpose four main modules of the thermoacoustic refrigerator were identified: (i) the thermoacoustic core, (ii) the resonance tube, (iii) the acoustic driver, and (iv) the heat exchangers. The main objective of the analysis was the optimization of the thermoacoustic core, which consists of the stack region of a thermoacoustic refrigerator, by applying the short stack boundary layer approximation. For the enthalpy and work flux equations of the short stack boundary layer approximation, which are the base for the calculations of the thermoacoustic core’s COP, 20 independent design parameters were identified, and summarized in a multidimensional parameter space. Introducing a normalized multidimensional parameter space the number of design parameters was reduced to ten. Setting limits on the normalized design parameters allowed us to identify the three most significant design parameters: (i) normalized stack length, (ii) normalized stack center position, and (iii) normalized temperature difference. Theoretical calculations of the thermoacoustic core’s COP indicate competitive values with commercially available refrigeration techniques. [Work supported by the Office of Naval Research; Martin Wetzel is also supported by a scholarship from DAAD.]
An analytical and numerical study of nonlinear bubble oscillations in viscoelastic fluids.
Authors: Allen John S. , Roy Ronald A.
Published: October 2005

The acoustically forced oscillations of gas bubbles in Newtonian fluids have been studied extensively; however, these oscillations have not been as thoroughly investigated in non-Newtonian fluids. An understanding of the non-Newtonian effects of viscoelasticity on this phenomena is particularly important to medical acoustic applications involving oscillatory bubble behavior in biological tissues and fluids. The stress tensor formalisms for non-Newtonian fluids used in previous works are reviewed and scrutinized. Inconsistencies in the literature and subsequent questions about the trace of the stress tensor are highlighted. As an initial step, a weakly nonlinear perturbation method is used to examine forced single bubble oscillations in a viscoelastic fluid. A novel analytical formulation is employed to make the perturbation approach (method of multiple scales) to the problem more tractable. Furthermore, this new formulation also allows for complementary numerical solutions. The physical limitations and relevance of this work with respect to medical applications are also discussed. [Work support by NIH through Grant No. RO1 CA39374.]
Acoustic reflex decay for modulated signals.
Authors: Cook Raymond D. , Ferguson Michael O. , Hall Joseph W. , Grose John H. , Pillsbury Harold C.
Published: October 2005

Temporal decay of the acoustic reflex provides the basis for an objective audiological test that differentiates cochlear from retrocochlear pathologies. The classic sign of a neural lesion is a rapid decay of the reflex under conditions of pure-tone stimulation for frequencies 1000 Hz and below. This restriction to lower frequencies is due to the fact that even normal ears show decay for higher-frequency signals. At present, it is unclear whether the acoustic reflex decay (ARD) seen in normal ears is related to frequency-specific channels or whether the critical variable is the timing information coded within the channels. This study examined ARD in subjects with normal hearing and middle ear function. The degree of ARD was measured for both modulated and unmodulated carrier frequencies of 500, 1000, 2000, and 4000 Hz with modulation rates of 50 – 400 Hz. The dependent variable was the half-life of the decaying reflex (ARD 50%) over a 12-s stimulation interval. Significant ARD was present for high-frequency unmodulated carriers, but not for low-frequency carriers. For all listeners, ARD was diminished for all modulated stimuli, suggesting that resistance to ARD is mediated by the temporal characteristics of the stimulus. [Work supported by the American Hearing Research Foundation.]
Is higher acoustic energy at faster rates necessary for the click-rate-induced improvement in acoustic reflex thresholds?
Authors: Rawool Vishakha W.
Published: October 2005

Ipsilateral click thresholds can improve by approximately 21 dB, with an increase in the click repetition rates from 50/s to 300/s [Rawool, Scand. Audiol. 24, 199–205 (1995)]. When click-trains are presented over the same duration (e.g., 1.5 s), the number of clicks presented at the lower rates is less than the number of clicks presented at the higher repetition rates. Thus there is more total energy for the higher repetition rates. Therefore, it has been proposed that an important factor contributing to the threshold advantage for higher repetition rates could be the number of clicks. This investigation was designed to evaluate acoustic reflex thresholds at various repetition rates using a constant number of clicks (constant acoustic energy). Ipsilateral acoustic reflex thresholds were obtained from 19 normal female left ears by presenting 300 clicks at the repetition rates of 50, 100, 150, 200, and 300/s. The frequency of the probe tone was 226 Hz (85 dB SPL). The results showed a significant improvement (mean = 17 dB) in acoustic reflex thresholds with the increase in repetition rates. Thus the improvement in acoustic reflex thresholds with the increase in the repetition rate can occur as a function of the rate itself, even if a constant number of clicks are presented at each rate.
Effect of hearing impairment on the click-rate induced facilitation of the acoustic reflex thresholds in older individuals.
Authors: Rawool Vishakha W.
Published: October 2005

Ipsilateral click thresholds can improve by approximately 21 dB, with in increase in the click repetition rates from 50/s to 300/s [Rawool, Scand. Audiol. 24 199–205 (1995)] in young normal individuals. This improvement is significantly reduced in older individuals [Rawool, J Gerontol. Biol. Sci. (in press)]. The current investigation was designed to evaluate the effect of age-related hearing impairment on the rate-induced improvement in the acoustic reflex thresholds. Ipsilateral acoustic reflex thresholds were obtained from 60 older ears in the age range of 50 to 74 years. The subjects were divided into four groups: (I) Normal. Hearing within normal limits (20 dB). (II) Mid high-frequency impairment. Hearing within normal limits up to 2 kHz, and an average impairment of 17.5 to 25 dB at 3, 4, 6, and 8 kHz. (III) Moderate high-frequency impairment. Hearing within normal limits up to 2 kHz and an average impairment of 35 to 61 dB at 3, 4, 6, and 8 kHz. (IV) Flat hearing impairment. Hearing impairment across the test frequencies. Ipsilateral acoustic reflex thresholds were obtained from the left and/or right ear by presenting clicks at the repetition rates of 50, 100, 150, 200, and 300 clicks/s. No significant differences were apparent in the rate-induced improvement (11 to 14 dB) in the acoustic reflex thresholds across the four groups.
Relationship between the frequency microstructure of the pitch-level effect and the microstructure of synchronous evoked otoacoustic emissions.
Authors: Burns Edward M.
Published: October 2005

The relationship between the frequency microstructure of the behavioral threshold and the frequency microstructure of the strength of synchronous evoked otoacoustic emissions (SEOAEs) and delayed evoked otoacoustic emissions is well documented [e.g., Zwicker and Schloth, J. Acoust. Soc. Am. 75, 1148–1154 (1984)]. In a previous report from this laboratory [Burns et al., J. Acoust. Soc. Am. Suppl. 1 80, S93 (1988)], it has been shown that there is also a correlation between the microstructure of the behavioral threshold and the microstructure of the pitch-level effect. In this paper, the relationship between changes in the microstructure of SEOAEs as a function of the level of the evoking stimulus and pitch shifts as a function of level is examined. [Work supported by NIDCD and the Virginia Merrill Bloedel Hearing Research Center.]
New evoked cochlear responses: Double chirp-evoked distortion products and double click-evoked otoacoustic emissions.
Authors: Keefe Douglas H.
Published: October 2005

A novel family of evoked OAE responses controls probe distortion using a stimulus presentation method well-suited to research and clinical applications. The family allows a complementary representation between DP measurements and double click-evoked OAE measurements. Each stimulus sequence includes three, equal-duration sub-sequences defined as follows: s1(t) is a single chirp or click, s2(t)=εs1(t−τ) is a copy of s1 with relative amplitude ε and delay τ (0−5 ms), and their superposition s12(t)=s1(t)+s2(t). The pressure response to each sub-sequence is p1, p2, and p12, respectively. The double chirp-evoked distortion product (2ChDP) and double click-evoked OAE (2CEOAE) are defined by pD=p12−p1−p2. This subtraction of click respones is similar to Kemp et al. (1986) in eliminating the linear response, but differs in that particular choices of {s1(t),τ,ε} improve measurements of 2CEOAEs at high frequencies by eliminating time-gating, and at low frequencies by reducing probe distortion, especially when two acoustic sources are used. With a 16 kHz sample rate, 2ChDP and 2CEOAE responses have been obtained from 350-7900 Hz. A 2CEOAE special case is τ=0, resulting in a wide bandwidth, single click-evoked OAE measurement without time-gating. Methodological refinements in real-time artifact rejection and nonlinear coherence help reduce noise. [Work supported by NIH Grant No. P01 DC00520.]
Discriminability of two-component complex tones by normal-hearing and hearing-impaired listeners.
Authors: Arehart Kathryn Hoberg , Fine Peninah S.
Published: October 2005

The discriminability of complimentary two-tone complex tones (Voelcker pairs) was investigated in normal-hearing and hearing-impaired listeners using a 2AFC task. A two-component complex consists of two pure tones (f1,f2) which differ in frequency (Δf Hz) and intensity (ΔI dB). When ΔI=0 dB, the pitch of the complex corresponds to the center frequency (fc) where fc=(f1+f2)/2. When ΔI≳0 dB, the pitch shifts toward the more intense component. In one tone of a Voelcker pair, the intensity of f1(I1) is greater than the intensity of f2(I2) by ΔI; in its complement, I1<I2 by ΔI. Discriminability of the pitches of Voelcker pairs was measured as a function of Δf (10 through 1000 Hz), for three fcs (1000, 2000, 4000 Hz) and for two ΔIs (1, 3 dB). Normal-hearing listeners’ results were similar to previous results [Feth et al., J. Acoust. Soc. Am. 72, 1403–1412 (1982)]. Thresholds for discrimination of Voelcker pairs by hearing-impaired listeners were abnormally large across all center frequencies. Results will be discussed in terms of predictions of EWAIF/IWAIF models [Anantharaman et al., J. Acoust. Soc. Am. 94, 723–729 (1993)] and hearing-impaired listeners’ deficits in using temporal cues in pitch perception.
Age-related hearing loss, temporary threshold shift and permanent threshold shift in four strains of mice.
Authors: Shiau Yea-Wen , Weiler Ernest M. , Kretschmer Laura , Ball Angel Dell’aira , Baker Mary Anne
Published: October 2005

A total of 96 mice from two inbred and two hybrid strains were tested for TTS (temporary threshold shift) and PTS (permanent threshold shift) using electrophysiological procedures for auditory brain-stem responses. Testing continued for up to 3 months following 2 h of exposure to 110-dB broadband noise. The inbred and hybrid strains carrying genes for age-related hearing loss showed TTS almost equal to their PTS ‘‘thus anticipating their tendency to hearing loss.‘‘ On the other hand, the inbred and hybrid strains not carrying those genes showed considerable recovery from their original TTS losses. Those with age-related hearing genes were very susceptible to noise-induced PTS. An additional effect was the presence of strong correlations between TTS and PTS for both inbred strains, but no correlation for the two hybrid strains. Noise exposure history plays a role in the noncorrelations between TTS and PTS typically found in humans. Could genes influence correlation between TTS and PTS in humans?
The effect of head protectors on warning sound perception in noisy workplaces.
Authors: Fortin Martin , Hetu Raymond , Tran Quoc Hung , Denis Stephane
Published: October 2005

The acoustic response of head protectors was assessed by means of a mecano-acoustic head simulator. The following protective devices were tested: welders’ mask, fire-fighter helmet, aluminized hood, leather hood, sand-blasting hood, dust protection hood, and emergency respirator. The tests were conducted in an hemi-anechoic chamber with a wideband noise presented at 100 dB SPL. The effect of 36 horizontal combined with 13 vertical angles of incidence was assessed. Generally speaking, head protectors are responsible for insertion gains of 5 to 10 dB in the low frequencies and for insertion losses of up to 30 dB in the high frequencies. The acoustic response of head protectors considerably varied with the angle of incidence. With the welder’s mask, when the source is coming from the rear, a systematic gain is observed at almost all frequencies; the mask acts as a low-pass filter in the frontal quadrant. These findings hold implications with respect to health and safety issues. In term of risk of hearing damage, the wearing of a head protector may significantly increase the noise exposure level of a worker. In terms of safety, such devices may interfere with signal detection in noise and sound source localization. [Work supported by IRSST.]
Physiological correlates of the time-intensity trade in auditory late responses.
Authors: Redner Joelle , Clock Eddins Ann
Published: October 2005

Numerous psychophysical studies have demonstrated that behavioral detection thresholds decrease with increasing stimulus duration, often referred to as the time-intensity trade. Few studies, however, have evaluated the physiological correlates of this trading relationship. The purpose of the present study was to examine the effect of stimulus duration on evoked potential thresholds known as the auditory late response (ALR). Behavioral and ALR thresholds were estimated for 1000 and 4000 Hz tone bursts at 8, 16, 32, 64, and 128 ms in five normal-hearing, young adults. Evoked responses were recorded in 2-dB steps from 20 dB to −4 dB SL re: behavioral threshold. ALR threshold was estimated as the lowest level at which the N1-P2 complex was visually detected by two independent judges. Preliminary results show that both behavioral and ALR thresholds decreased as a function of increasing duration. For the 1000-Hz stimulus, both ALR and behavioral thresholds decreased by approximately 23 dB HL over the range of durations tested. Average ALR and behavioral thresholds for the 4000-Hz stimulus decreased by about 19 dB HL. These results show that the time-intensity trade can be demonstrated physiologically using the auditory late response.
Estimates of spectral weights and internal noise in the discrimination of spectral variance.
Authors: Lutfi Robert A. , Oh Eunmi
Published: October 2005

An experiment was conducted to measure the relative contribution of spectral weights and internal noise in the discrimination of spectral variance. The stimuli were simultaneous tone complexes comprised of the six octave frequencies from 250 to 8000 Hz. On each presentation the levels of components in dB were drawn independently and at random from one of two normal distributions having identical means but different variances (σN = 1 dB, σS = 2–10 dB). In the standard 2IFC procedure, the listener’s task was to choose the complex having the greater variance in component level. The shape of the psychometric function for all five listeners was markedly different from that of an observer limited only by additive internal noise. It was consistent with an observer that gives weight to only one or two components in the complex. This result, however, was inconsistent with the weighting functions computed from the trial-by-trial data from these listeners. Both measures can be reconciled if it is assumed that listener weights vary from trial to trial, or equivalently that observations are corrupted by multiplicative rather than additive internal noise. [Work supported by NIDCD RO1 DC01262-04.]
Intensity weighted average of instantaneous frequency computations using time-frequency representations.
Authors: Anantharaman Jayanth N. , Krishnamurthy Ashok K. , Feth Lawrence L.
Published: October 2005

The intensity weighted average of instantaneous frequency (IWAIF) has been used to model listener performance in complex signal discrimination [Anantharaman et al., J. Acoust. Soc. Am. 94, 723–729 (1993)]. Short-term [Krishnamurthy and Feth, J. Acoust. Soc. Am. 93, 2387(A) (1993)] and multichannel [Mokheimer et al., IEEE Proc. First Intl. Conf. on Electronics Circuits and Systems, Cairo, Egypt (1994)] implementations of the model have been proposed. Time-frequency representations (TFRs) offer a convenient way to process signals over the time-frequency plane. TFRs can be used to compute the IWAIF. TFRs can also be used to compute the short-term IWAIF and the multi-channel IWAIF. These will be presented along with preliminary developments of both the short-term IWAIF and the multichannel IWAIF. The necessary properties of the TFRs to be suitable for use in these models will be discussed. [Work supported by a grant from AFOSR.]
Comodulation masking release as a function of masking noise-band temporal envelope similarity in normal hearing and cochlear impaired listeners.
Authors: Mendoza Lee , Schulz Mari L. , Roberts Richard A.
Published: October 2005

Thresholds for a pure-tone signal (1000 Hz) were obtained from both normal hearing and hearing-impaired listeners in a variety of masker conditions. Masking stimuli consisted of five Gaussian noise bands, each 20 Hz wide, and centered on 500, 750, 1000, 1250, and 1500 Hz. Two such base stimuli were created. In the first stimulus set, all noise bands had the same temporal envelope (comodulated). In the second set, each noise band was generated independently of the other bands, and thus each had independent temporal envelopes. Additional masking stimuli were generated by combining the comodulated and independent bands at specific comodulated/independent intensity ratios (CIR = 25, 20, 15, 10, and 5 dB), with overall level of the combined noise bands held constant. The result of increasing CIR was a progressive increase in the similarity of temporal envelopes of the noise bands masking the signal. Compared to threshold for the pure-tone signal in independent bands of noise, threshold steadily decreased as the CIR increased for normal hearing listeners. Cochlear-impaired subjects also showed decreased threshold with increasing CIR; however, the improvement was seen to plateau at relatively low CIRs. [Work supported by DRF and USARC.]
Discrimination of harmonic- and log-spaced profiles and of static and dynamic profiles by good and poor profile listeners.
Authors: Drennan Ward R. , Watson Charles S.
Published: October 2005

Most profile experiments have employed static profiles with logarithmic spacing. Many naturally occurring sounds have harmonic spacing and vary dynamically in time. Watson and Drennan [J. Acoust. Soc. Am. 97, 3272(A) (1995)] examined profile discrimination using both static and frequency-glide profiles with harmonic and logarithmic component spacing. Subjects detected an intensity increment in the middle component of 11-component, 400-ms profiles with a frequency range of 200–2200 Hz. Differences among the seven subjects were considerably larger than differences among the types of profiles, confirming earlier observations of a large range of abilities to discriminate profiles. Another experiment was therefore conducted to estimate the distribution of profile discrimination abilities for normal-hearing listeners. Forty-six subjects were screened using static-log profiles. The distribution of thresholds was roughly normal with a range of −2 to −26 dB (signal level relative to component level) and an s.d. of 4.8 dB. No dichotomy in profile discrimination ability was found. Subjects were selected from each tail of the distribution and tested using the static-log, static-harmonic, dynamic-log, and dynamic-harmonic profiles. The order of presentation of conditions significantly affected the results; however, whatever the order, static profiles yielded lower thresholds than the frequency-glide profiles. [Work supported by NIH/NIDCD and AFOSR.]
Across-channel processes in frequency modulation detection.
Authors: Furukawa Shigeto , Moore Brian C. J.
Published: October 2005

This study examined whether the detection of frequency modulation (FM) on two carriers depends on the coherence of the FM across carriers. Psychometric functions were measured for detecting sinusoidal FM of carriers with frequencies 1100 and 2000 Hz. The modulators for the two carriers were either in phase (coherent) or in anti-phase (incoherent). The modulation rate was either 2.5, 5, or 10 Hz. One or more cycles of modulation were used. The modulation of each carrier was equally detectable, as determined in a preliminary experiment. A continuous pink noise background was used to mask the outputs of auditory filters tuned between the two carrier frequencies. Detectability was better for coherent FM than for incoherent FM. The effect of FM coherence was greatest at the lowest modulation rate, possibly indicating that phase locking plays a role [B. C. J. Moore and A. Sek, J. Acoust. Soc. Am. 97, 2468–2478 (1995)]. The detectability of the coherent FM was well above the value predicted on the assumption that information from the two carrier frequencies was processed independently and combined optimally. These results imply the existence of one or more mechanisms sensitive to FM coherence. [Work supported by the MRC(UK), the British Council, and an ORS award.]