bluuebunny/crossref_metadata_2025 huggingface dataset:
Phonemic resetting versus postural adjustments in the speech of cochlear implant users: An exploration of voice-onset time
Authors: Lane Harlan , Wozniak Jane , Matthies Melanie , Svirsky Mario , Perkell Joseph
Published: October 2005

Voice-onset time (VOT) was measured in plosive-initial syllables uttered by five cochlear implant users prior to and repeatedly at intervals after activation of their speech processors. In ‘‘short-term’’ experiments, the elicitation set was read after the subject’s processor had been off for 24 h, then turned on, then off again. Four out of five implant users increased voiceless and/or voiced VOTc (VOT corrected for changes in syllable duration) from preimplant baselines to final recordings made 1–3 years later. Measured acoustic correlates of speech ‘‘posture’’ (average SPL, F0, and low-frequency spectral slope) changed concurrently. Results in the short-term study were largely consistent with the long term. Significant multiple regressions relating changes in VOTc to accompanying changes in postural correlates were found in both studies. This outcome is consistent with hypotheses that predict changes in both VOTc and in postural correlates with the restoration of some hearing and that allow for linkages between the two. Some of the reliable VOTc increases obtained over the long term that were not correlated with postural changes may have been caused directly by auditory validation of articulatory/acoustic relations that underlie synergisms for phoneme production.
The role of distortion products in masking by single bands of noise
Authors: van der Heijden Marcel , Kohlrausch Armin
Published: October 2005

Masking experiments with frozen-noise maskers were conducted to investigate the role of distortion products generated by the interaction between the components of a bandpass noise masker. In the first experiment, thresholds of a 900-Hz sinusoidal signal with a duration of 50 ms (10-ms ramps included) were measured in the presence of bandpass noise maskers ranging from 1 to 2 kHz. In all measurements the same 500-ms noise sample was used (frozen noise), presented at overall sound-pressure levels of 35, 50, 65, or 80 dB. The signal was temporally centered in the masker. Four subjects participated in the experiment. Threshold variations of more than 10 dB were observed on varying the signal phase. The pattern of threshold versus signal phase resembled a sinusoid; the signal phases at the minimum and maximum thresholds differed by about 180 deg. The phase pattern shifted with increasing masker level. The individual shift for the masker range of 45 dB was between 100 and 200 deg. The direction of this shift agreed with data on the phase of cubic difference tones as a function of the level of sinusoidal primaries. In a second experiment a large number of different frozen-noise samples were used as maskers in order to evaluate the generalizability of the phase effect. Two types of noise maskers were used: a low-frequency masker (0–800 Hz) and a high-frequency masker (1000–2000 Hz). For each noise sample, thresholds of a 900-Hz signal were measured for two signal phases, 0 and 180 deg. An analysis of variance showed that signal phase played a significant role for the high-frequency, but not for the low-frequency, masker.
Age effects on duration discrimination with simple and complex stimuli
Authors: Fitzgibbons Peter J. , Gordon-Salant Sandra
Published: October 2005

This study examined age-related changes in temporal processing by measuring DLs for signal duration using simple and complex stimuli. Previous research has shown that elderly listeners exhibit difficulty discriminating duration changes in simple sounds, suggesting the possibility of age-related changes in central timing mechanisms. The present experiments examined the interactive effects of aging, hearing loss, and stimulus complexity on duration discrimination. Four groups participated: young and elderly listeners with normal hearing, and young and elderly listeners with hearing loss. Duration DLs were measured for 250-ms tone bursts and for silent gaps between tone bursts that were presented either in isolation or embedded as target stimuli within tonal sequences. The tone sequences were composed of five sequential 250-ms components. Stimulus complexity was varied by changing the sequential order of tone frequencies and the location of an embedded target component across listening conditions. Analyses of results revealed the following: Elderly listeners performed more poorly than younger listeners in nearly all stimulus conditions, the effects of stimulus complexity on discrimination were greatest among elderly listeners, and hearing loss had no systematic effect on discrimination performance.
Analytical expressions for the envelope correlation of certain narrow-band stimuli
Authors: van de Par Steven , Kohlrausch Armin
Published: October 2005

Analytical solutions are presented for the correlation between the envelopes of certain narrow-band stimuli which are typically used in binaural research. These stimuli are either the sum of an in-phase masker and an out-of-phase signal, or they are two partially correlated noises. Because an envelope has a nonzero mean, the solutions differ depending on whether the envelope correlation is expressed as the normalized cross correlation or as the normalized cross covariance (Pearson product-moment correlation). The envelope correlation depends on the statistics of the masker and the signal whereas the waveform correlation depends on neither. This influence only disappears for the normalized envelope cross correlation provided that the correlation is close to one. In this case, the normalized envelope cross correlation is equal to the square root of the waveform correlation. The results for two partially correlated noise bands are also of relevance for experiments dealing with monaural envelope discrimination and comodulation masking release.
Some temporal parameters in vibrotactile forward masking
Authors: Gescheider G. A. , Migel Naomi
Published: October 2005

Tactile thresholds for detecting a 250-Hz signal of variable duration presented at variable times after the termination of a 250-Hz 700-ms masking stimulus were measured. It was found that the threshold shift resulting from the presentation of the masking stimulus declined as functions of the duration of the signal and the duration of the time interval between the masking stimulus and signal. Both of these effects were found to be attributable to an increase in the time interval between the offset of the masking stimulus and the offset of the signal.
Applications of inverse beamforming theory
Authors: Wilson James H.
Published: October 2005

The underlying theory for the significant (≳10 dB) performance gains described in a companion paper [J. P. Fabre and J. H. Wilson, J. Acoust. Soc. Am. 98, 3252–3268 (1995)] using measured noise data from Outpost SUNRISE is developed in this paper. Recent theoretical papers [J. H. Wilson, J. Acoust. Soc. Am. 73, 1648–1656 (1983); A. Nuttall and J. H. Wilson, ibid. 90, 2004–2019 (1991)] on inverse beamforming (IBF) [patent on inverse beamforming obtained by J. Wilson, J. Donald, and A. Nuttall, NUWC, New London, CT (Patent No. NC73991)] have dealt only with the solutions to the inverse beamforming integral equation and the performance properties of the IBF solutions are described in this paper. IBF consists of three separate algorithms: a beamforming algorithm called the Fourier integral method (FIM), a data thresholding technique called the eight nearest-neighbor peak picker (ENNPP), and a three-dimensional ‘‘M of N’’ tracker. The properties of each algorithm are discussed and it is shown that IBF has a 3-dB array noise gain (ANG) advantage over conventional beamforming (IBF) under ideal conditions. This 3-dB ANG advantage is proven theoretically and illustrated with measured noise data from Outpost SUNRISE. The 3-dB ANG advantage leads to a minimum detectable level (MDL) advantage of over 10 dB for IBF as shown in a companion paper. The spikiest solution to the IBF integral equation is derived using standard Backus–Gilbert inverse theory and this solution is identical to FIM at array design frequency.
The generalized Debye series expansion: Treatment of the concentric and nonconcentric cylindrical fluid–fluid interfaces
Authors: Danila E. B. , Conoir J. M. , Izbicki J. L.
Published: October 2005

A new method for the calculation of the scattered field due to a plane wave incident on a structure involving one or several cylindrical fluid–fluid interfaces is presented. This method involves the generalized Debye series expansion (GDSE). The GDSE allowed for the decomposition of the global physical process in a series of local interactions: reflections and refractions at each interface of the scatterer. In this manner, the logical organization of the local interactions is obtained. In this sense the GDSE method brings a better physical understanding than the classical calculation. A detailed analysis for the cases of the fluid cylinder and the concentric fluid shell is presented in order to explain the GDSE construction. The energy conservation law and the characteristic equation are expressed by means of the modal reflection and refraction coefficients. The method is extended for a fluid shell defined by two nonconcentric cylindrical surfaces and for some more complicated cylindrical structures.
Complex power, reciprocity, and radiation modes for submerged bodies
Authors: Chen Pei-Tai , Ginsberg Jerry H.
Published: October 2005

This study of the surface interaction between a submerged body and the surrounding fluid begins by developing reciprocity relations between alternative pressure and normal velocity distributions on the wetted surface. A corollary of these principles is proof of the symmetry of the matrix representing the acoustic contribution to the structural impedance, even in situations where the acoustic relation between surface pressure and normal velocity is not symmetric. The reciprocity properties lead to two eigenvalue problems, whose solution yields velocity and pressure radiation modes, each of which decouples the complex surface acoustic power. The matrices required to obtain the eigensolutions are shown to arise in the ordinary course of modeling fluid–structure interaction. Further analysis reveals that the velocity and pressure modes occur in a one-to-one correspondence, with a relative phase angle that decreases monotonically as the radiated power increases relative to the reactive power. Using the radiation modes to form modal series for the surface pressure and normal velocity due to a specified excitation offers a new perspective for acoustic interaction phenomena. In an example, the acoustic equations for a slender spheroidal body are used to evaluate the radiation mode patterns in a range of frequencies. These modes are then used to decompose the surface velocity and pressure fields corresponding to a uniform breathing motion of the spheroidal surface.
Measurement and prediction of time domain waveforms in fiber-reinforced laminates
Authors: Scudder L. P. , Hutchins D. A. , Green E. R.
Published: October 2005

Accurate measurements have been made of the surface displacement produced by a laser-generated impulse in a cross-ply CFRP sample, whose laminae are thick in comparison to the wavelength of the ultrasound. Theoretical predictions of the expected surface displacements resulting from an impulsive source were made using the global matrix method, which predicts the behavior of guided waves in laminated structures. Good agreement is seen between experiment and theory when the bandwidths assumed by theory match those of the experiments.
Wave space resolution in ultrasonic scattering measurements
Authors: Mast T. Douglas , Waag Robert C.
Published: October 2005

The spatial-frequency spectra of the spatial properties of a scattering medium can be determined from measurements of scattering over a number of angles or frequencies. In such measurements, the spatial localization associated with transducer beam patterns and time gates causes an uncertainty in the measured spatial-frequency domain properties of the scatterer. This uncertainty is analyzed using an analytic and computational model in which system effects are represented by a spatial-frequency domain function. Wave space resolution in a particular direction is shown to be inversely proportional to the spatial-frequency spread of the system function in that direction. In the backscatter case, wave space resolution is limited in the direction of the scattering vector by a convolution of the emitted pulse and the detector time gate, and resolution in the lateral direction depends mainly on the transducer aperture, increasing approximately in proportion to the aperture diameter. In the case of backscatter measurements, smooth aperture apodization improves lateral resolution somewhat but has little effect on resolution in the direction of the scattering vector. For angular scattering measurements, resolution in all directions depends on both the aperture size and (for sufficiently short time gates) on the time gates employed. Illustration of the practical importance of wave space resolution is provided using analysis of two previously published tissue characterization experiments.
Russian (Soviet) contributions to musical acoustics
Authors: Galembo Alexander
Published: October 2005

The former isolation of Russia has made many scientific works and results unknown to researchers in the Western countries. This is unfortunate, as the history of musical acoustics in Russia shows many interesting ideas and pioneer results reached by highly talented and enthusiastic scientists. Best known is probably Lev Termen with his ‘‘theremin’’—the first application of electronic technology to musical art. A. V. Rimski-Korsakov, one of the most distinguished Russian acousticians, started his scientific career with investigations of stringed instruments. This paper presents a bibliography of Russian-Soviet publications on musical acoustics (in English translation), covering the period 1885–1994.
The perceptual representation of voice gender
Authors: Mullennix John W. , Johnson Keith A. , Topcu-Durgun Meral , Farnsworth Lynn M.
Published: October 2005

The perceptual representation of voice gender was examined with two experimental paradigms: identification/discrimination and selective adaptation. The results from the identification and discrimination of a synthetic male–female voice continuum indicated that voice gender perception was not categorical. In addition, results from selective adaptation experiments with natural and synthetic voice stimuli indicated that the perceptual representation of voice adapted is an auditory-based representation. Overall, these findings suggest that the perceptual representation of voice gender is auditory based and is qualitatively different from the representation of phonetic information.
Estimation of bottom scattering characteristics from acoustic reverberation special research program bistatic data
Authors: Bondaryk Joseph E. , Dyer Ira , Dorfman Eugene
Published: October 2005

For many years, sonar practitioners have used Lambert’s law on a flat bottom to describe clutter due to bottom reverberation. This examination of a subset of the bistatic data from the B′ site of the ARSRP natural laboratory examines the validity of this approximation. Eight pings transmitted by the CoryChouest and received by the Alliance were chosen to cover the bistatic angular range of −90 to +90 deg with respect to B′. Transmission loss and area corrections to a flat bottom of representative depth were calculated using the ARTIST ray-tracing program. These corrections were applied to the data to compute scattering strength in each beam-time bin. This scattering strength was averaged over areas with similar grazing angle to transmitter, grazing angle to receiver and bistatic angle. Again, these are angles to a flat bottom scenario. The scattering strength plotted versus these three angles shows that neither Lambert’s law nor the generalized version by Nayar etal. describe bistatic scattering. [Research supported by ONR.]
Effects of shear elasticity on high-frequency bottom scattering
Authors: Ivakin Anatoliy N. , Jackson Darrell R.
Published: October 2005

It is known that marine sediments can support both compressional and shear waves. However, published work on scattering from irregular elastic media has not examined the influence of shear on seabed scattering in detail. Here, a perturbation model for high-frequency sound scattering from an irregular elastic bottom is considered. The seabed is assumed homogeneous on the average and two kinds of irregularities are assumed to cause scattering: roughness of the water–seabed interface and volume inhomogeneities of the sediment mass density and the velocities of compressional and shear waves. The first-order small perturbation approximation is used to obtain expressions for the scattering amplitude and average intensity of the scattered field. The angular dependence of the backscattering strength is calculated for different types of sediments and the influence of shear elasticity is examined by comparison with the case of a fluid bottom. Shear effects on both roughness and volume scattering are found to be rather strong (up to 5–7 dB) for dense sandy sediments at near-critical and subcritical grazing angles. The difference between the angular dependencies of roughness and volume scattering is examined and features of interest for remote acoustic characterization of seabeds are noted. [Work supported by ONR.]
The effects of speaking rate on the intelligibility of speech for various speaking modes
Authors: Krause Jean C. , Braida Louis D.
Published: October 2005

In adverse listening conditions, large and robust increases in intelligibility can be achieved by speaking clearly. The most striking differences between clear and conversational speech are associated with differences in speaking rate. To understand these differences, the intelligibility of speech in a variety of speaking modes was investigated at three different speaking rates. Talkers with significant speaking experience were asked to produce clear and conversational speech at slow, conversational, and quick rates. Previous studies show that the speaking rate for clear speech is roughly one-half that of conversational speech. Therefore, during training, the talkers were given feedback on their intelligibility in order to elicit the clearest possible speech at conversational and quick speaking rates. Talkers also recorded sentences in several other speaking modes such as soft, loud, and conversational with pauses inserted, as required for input to some automatic speech recognition systems. All speech materials recorded were nonsense sentences which provide no semantic context to aid listeners in identifying key words. The effects of changes in speaking rate on intelligibility of various speaking modes for normal hearing listeners in a background of wideband noise are discussed. [Work supported by NIH.]
Speech modulation transfer functions for different speaking styles
Authors: Payton Karen L. , Braida Louis D.
Published: October 2005

The speech transmission index (STI) is highly correlated with speech intelligibility scores when the environment is degraded by noise and/or reverberation and/or the listener’s hearing is impaired [e.g., Payton etal., J. Acoust. Soc. Am. 95, 1581–1592 (1994)]. The STI is typically computed from modulation transfer functions (MTFs) that are determined theoretically, based on effective SNR, or on measurements using the RASTI procedure. In principle, however, MTFs can be computed directly from speech envelope spectra. For the current study, envelope spectra were computed for both conversational and clearly articulated speech. Three environments were considered: quiet/anechoic, reverberant (0.6 s RT), and additive noise (0 dB SNR). Results indicate that reliable MTFs can be computed from speech envelope spectra if the coherence function is used to limit the range of modulation frequencies (to reduce the effects of computational artifacts). Also, while MTFs for the two speaking styles are very similar in additive noise, in reverberation MTFs differ as one would expect on the basis of the higher intelligibility of clear speech in reverberant environments. [Work supported by NIH.]
Speech intelligibility of a multiple loudspeaker public address system in long enclosures
Authors: Kang Jian
Published: October 2005

Multiple loudspeaker public address systems are often used in long enclosures, such as underground stations, where one dimension is much greater than the other two. Classic room acoustic theories cannot be used in long enclosures as the assumption of a diffuse sound field is not satisfied. In this research a theory of reverberation in long enclosures is established [J. Kang, Acustica (to be published)]. It is shown that the reverberation in long enclosures varies systematically with the source–receiver distance. Based on the theory, a computer program for calculating the speech transmission index (STI) of multiple loudspeakers in long enclosures was developed, with which the optimal loudspeaker directionality and spacing can be determined. With the help of this program, a series of treatments for improving the speech intelligibility of multiple loudspeakers were investigated in a 1:16 scale model of St. John’s Wood station in London. It was found that the STI can be improved effectively by diffuse treatments and strategic positioning of absorption. Some of the above results are being used for the new Hong Kong airport-underground project. [Work supervised by Dr. R. J. Orlowski and supported by MTRC, ORS, and COT.]
Intelligibility of normal speakers: Vowel space characteristics
Authors: Torretta Gina M. , Bradlow Ann R. , Pisoni David B.
Published: October 2005

Even within careful speaking conditions, normal speakers vary in intelligibility. This study investigated vowel space characteristics as one correlate of variation in intelligibility. Data consisted of 100 Harvard sentences, spoken by 20 speakers and transcribed by ten listeners per speaker. Formant measurements (mel transformed) of six tokens each for three vowels [i,a,o] provided a basis for assessing the vowel-space characteristics. First, vowel-space area was calculated as the Euclidean area between vowel category means. Across all 20 speakers, this area did not correlate with intelligibility. However, for a subset of the speakers (three highest, three lowest in intelligibility) there was a moderate positive correlation (r=+0.34). Second, vowel-space dispersion was calculated as the mean distance from the center of the triangular space to all 18 tokens. This dispersion measure showed a moderate, positive correlation with intelligibility across all 20 speakers (r=+0.43), suggesting the importance of individual token location for overall intelligibility. Finally, minimum and maximum formant values gave a measure of F1 and F2 range covered by vowel tokens. This measure revealed that F1 range correlated positively with intelligibility (r=+0.53), whereas F2 range did not. The results will be discussed in the context of talker variability and intelligibility.
Visual-speech intelligibility for syllables: A comparison of conversational and clear speech
Authors: Gagné Jean-Pierre , Rochette Anne-Josée
Published: October 2005

The visual speech intelligibility of /C–v/ and /C–v–C/ syllables spoken under conversational-like and clear speech conditions was compared. The syllables consisted of voiced consonants, varying in place of articulation (i.e., /b,d,g,v,z,j/), presented in three vowel contexts (/a,i,u/). Talkers were six female adults, and each produced four iterations of the stimulus set for each of the two speaking conditions. The 1728 videotaped items (36 syllables ×2 manners of speech ×4 iterations ×6 talkers) were edited, randomized, and shown (without sound) to viewers with normal hearing. Viewers’ completed a consonant-recognition task and these data were used to determine a visual speech-intelligibility score for each stimulus set produced under the conversational and clear speech conditions. Results revealed that, despite significant within-talker variability in both speaking conditions, significantly higher speech intelligibility scores were observed for the production of clear speech. A significant talker effect, and a talker × manner interaction also emerged. The magnitude of the clear speech effects and the within- and across-talker variability in visual-speech intelligibility will be discussed.
A comparison between cerebral-palsied and normal adults in the perception of auditory-visual illusions
Authors: Siva Nithya , Stevens Erica B. , Kuhl Patricia K. , Meltzoff Andrew N.
Published: October 2005

Listeners obtain information about speech both from listening to a talker and by using visual cues from the talker’s face. As demonstrated in the McGurk effect, conflicting auditory and visual cues produce illusions. The present experiment investigated whether lack of experience with normal speech production affects the perception of auditory-visual illusions. Adults with cerebral palsy (CP) who have been severely dysarthric since birth were compared to normally speaking adults on two types of illusions: (1) auditory /aba/ paired with visual /aga/ which typically produces a /da/ illusion; and (2) auditory /aga/ paired with visual /aba/ which typically produces a /bga/ illusion. The number of illusory responses was compared for each group. There was no difference between groups in the number of /da/ illusions. However, adults with CP perceived fewer /bga/ illusions than normal adults. These results suggest that lack of experience articulating speech inhibits a listener’s ability to perceive unusual English phoneme clusters like /bga/. [Research supported by NICHD.]
Results of take-home trial for a nonlinear beamformer used as a noise reduction strategy for cochlear implants
Authors: Margo Vena , Terry Mark , Schweitzer Christopher , Shallop Jon
Published: October 2005

A nonlinear frequency domain beamforming algorithm was evaluated as a noise reduction technique with eight cochlear implant patients, in a take-home trial. The subjects wore the prototype device coupled to the Nucleus processor for 5–8 weeks. The subjects were tested both before and after the take-home trial with a single noise source at 45 deg ipsilateral to the implant and with sentence type material. The results strongly favored the coupled device for noisy environments and indicated no additional benefits from a period of continued use. The subjective reports indicated that the two-microphone coupled device had a more robust sound quality and is preferred in noisy environments to the stand alone device. Currently the performance measures are being extended to cover sentence scores in a diffuse noise field (four speakers at different locations) and the results for both noise jammer arrangements will be reported.
Temporal characteristics of the speech of a deaf-blind person with a cochlear implant
Authors: Limbach Lynn , Soffer Chavi Goodman , McGarr Nancy S. , Bell-Berti Fredericka
Published: October 2005

Many of the early studies of the effects of cochlear implants on speech production focused on the speech of persons with profound adventitious hearing loss. More recently, there has been substantial interest in the effects of implants on the speech of persons with congenital hearing loss. This study extends the research in this area to a woman who has been profoundly hearing impaired since birth and sustained a sudden loss of vision in her late teens. She has received extensive speech training, and is also a fluent reader of Braille. For this study, she was recorded reading a passage aloud one month postimplant, and then twice again at three month intervals. During each recording session, she read the six-sentence passage with the implant activated and then with the implant turned off. Analyses of temporal characteristics of each sentence, including relative speech and pause durations and word durations, will be presented. [Work supported by St. John’s University and by NIH Grant DC-00121 to the Haskins Laboratories.]
Acoustic properties of alaryngeal speech
Authors: Roussel Nancye C.
Published: October 2005

One of the current options for the restoration of speech in individuals, who have undergone total laryngectomy, is the use of artificial (electronic) larynx devices. These devices can be classified as either transcervical devices, which transmit the acoustic signal to the vocal tract through the skin and other tissues of the neck, or intraoral in which the signal is directed into the oral cavity through a short piece of plastic tubing. Differential effects on single word intelligibility as a function of artificial larynx type were studied. All judges had no previous experience listening to alaryngeal speech. Four brands of the artificial larynx devices were tested and the results revealed a significant increase in intelligibility with the use of transcervical devices. These results were somewhat surprising as earlier informal surveys had intraoral devices rated higher in terms of listener preference. Perceptual error matrices were constructed and are being analyzed, as are acoustic representations of test stimuli to determine possible factors to account for these intelligibility differences. Results of these analyses will be presented.
The structural organization of the mental lexicon and its contribution to age-related declines in spoken word recognition
Authors: Sommers Mitchell S.
Published: October 2005

Three experiments were conducted within the framework of the Neighborhood Activation Model of spoken word recognition to examine how the structural organization of the mental lexicon may contribute to age-related declines in spoken language processing. According to the model, lexically hard words are items that are phonetically similar to many other high-frequency words and should be identified less accurately than easy words which are phonetically similar to relatively few, low-frequency items. The results of experiment 1 demonstrated that lexical difficulty had differential effects on older and younger listeners. Specifically, relative to young listeners, older adults exhibited significantly poorer identification scores for lexically hard items. Experiment 2 indicated that these age differences in the effects of lexical difficulty were maintained under conditions in which performance for easy words was the same for older and younger listeners. In the third experiment, reducing the resources available for perceptual identification, by changing from single to multiple talkers, produced greater effects of lexical difficulty for older, compared to younger, listeners. Explanations for the results based on diminished cognitive resources and impaired inhibitory control will be discussed. [Work supported by Washington Univ.]
Age differences in the effects of talker familiarity on spoken word recognition
Authors: Yonan Cynthia A. , Sommers Mitchell S.
Published: October 2005

Recent evidence has demonstrated that young adults achieve improved spoken word recognition performance when words are produced by familiar, as compared to unfamiliar, voices [Nygaard etal., Psych. Sci. 5, 42–45 (1994)]. This benefit for familiar voices is hypothesized to be a result of reduced perceptual normalization demands when listeners have previous knowledge of source characteristics. The present study investigated whether normal-hearing older listeners exhibit a similar improvement for familiar voices. Younger and older volunteers were trained to discriminate four voices and were then tested on a perceptual identification task with familiar and unfamiliar voices. Although voice discrimination did not differ as a function of age, only the older participants exhibited improved word recognition performance for familiar talkers. Word recognition performance was also examined separately for words at two levels of lexical difficulty: (1) words that are phonetically distinct from others (easy words), and (2) words that are phonetically similar to others (hard words). The largest benefit of voice familiarity was observed for older listeners identifying lexically hard words. The implications of these findings for age differences in the use of voice information will be discussed.
Implicit memory for hybrid silent-center syllables
Authors: Hura Susan L.
Published: October 2005

A growing body of evidence suggests that information about specific voices and specific exemplars of words is encoded in memory, as observed in results of implicit memory tasks in which subjects perform perceptual classification of stimuli. Hura [dissertation, University of Texas (1994)] found identification performance on silent-center (SC) syllables improved with previous exposure to corresponding full syllables, implying that representations of individual full syllables were encoded in memory and accessed in identification of SC stimuli. The current study investigates whether prior exposure to SC syllables improves performance on full syllables. Ten /bVt/ syllables spoken by multiple talkers were used to generate SC and hybrid SC stimuli (which combine the initial CV transition from one talker and the final VC transition from another). A subset of SC syllables, varying for identity of talker or vowels presented, were presented to subjects for identification. After a variable delay subjects were tested on a subset of full syllable stimuli. The magnitude of implicit memory effects in each case is assessed to address the claim that dynamic vowel information is speaker independent as suggested by the theory of dynamic specification.
Task demands affect lipreaders’ search for information
Authors: Lansing Charissa R. , Minch Heather D. , McConkie George W.
Published: October 2005

Two experiments were conducted to determine whether a lipreader’s task (making phonemic or prosodic distinctions about the spoken message) changes the regions of the talker’s face from which information is needed, and whether lipreaders are sensitive to these changes. An initial experiment found that when face movement was limited to the talker’s lips-plus-mandible region, the accuracy of intonation judgments was reduced but the accuracy of phonemic judgments was not. A second experiment then recorded gaze direction of lipreaders as they attempted to make judgments about the phonemic, stress, or intonation contour characteristics of short utterances. Results indicated that they spent more time looking at upper portions of the face when judging intonation contours than in the other conditions. Other differences in the eye movement patterns were also found among task conditions. Thus lipreaders are aware that different aspects of the speech information are signaled at different facial regions, and can adjust their direction of gaze to take advantage of this knowledge. [Work supported by NIH.]
Calming the capillary waves on the surface of a bubble using an insoluble surfactant
Authors: Asaki Thomas J. , Thiessen David B. , Marston Phillip L.
Published: October 2005

The excess damping of capillary waves caused by a surfactant monolayer was demonstrated for the quadrupole shape mode of an isolated acoustically trapped bubble in water. A known amount of the water-insoluble surfactant stearic acid was deposited on the bubble surface from a microliter of ethanol solution. As the bubble dissolves, its surface area decreases thus compressing the monolayer. Compression rates ranged from 0.09 to 0.18 Å2 per molecule per minute for different bubbles and surfactant coverage ranged from 20 to 37 Å2 per molecule specific area. This technique was tested for accuracy and reproducibility by application to pendant bubbles and subsequent measurements of the static surface tension. Shape oscillations were induced by modulation of the ultrasonic radiation pressure and the free decay was recorded by an optical extinction technique. Local maxima in the normalized damping and frequency were observed near 26 Å2 per molecule coverage in agreement with similar studies of capillary waves on flat interfaces. An unexpected increase in the frequency was observed at high coverage and may be associated with the solidification or collapse of the monolayer. Any effects due to the presence of ethanol were shown to be negligible. [Work supported by ONR.]
Observation of nonlinear scattering of acoustical waves at a subsurface bubble layer
Authors: Ostrovsky Lev A. , Klusek Zygmund , Sutin Alexander M. , Soustova Irina A. , Matveyev Alexander I. , Potapov Andrey I.
Published: October 2005

To observe nonlinear acoustic effects in a subsurface bubble layer, two echo sounders working at different frequencies were used. The experiments were performed in the shallow area of the southern part of the Baltic Sea aboard the research vessel ‘‘Oceania.’’ Two echo sounders were run at 30 and 37 kHz; each had a power of about 0.3 kW. The depth of the echo sounders was about 15 m and the intensity of the acoustic signal in the subsurface bubble layer was enough to observe nonlinear effects. The sum and difference frequency components in the spectra of the scattered signal were determined. A theory of such a nonlinear scattering, based on summarizing the signals scattered by separate bubbles, was developed. It was shown that the sum frequency component was due to a noncoherent reverberation in the bubble layer and the difference frequency component was coherent. This component was generated in the process of primary wave propagation and can be received after sea surface reflection. Experimental and theoretical results have shown that the nonlinear scattering can be used to determine bubble density at sea. [Work was supported by ONR.]
Recent progress in the INRS speech recognition system
Authors: O’Shaughnessy Douglas , Li Zhishon , Farhat Azarshid
Published: October 2005

For large-vocabulary continuous-speech recognition, a two-pass search allows inexpensive first-pass models, with pruned search spaces represented by word graphs. Powerful language models and detailed acoustic-phonetic models follow. A first-pass Viterbi lexicon search is avoided via tables of estimates of phone scores and durations, from backward-Viterbi searches of much smaller graphs, which impose diphone rather than full lexical constraints on phonetic transcriptions. These estimates of phone scores and durations are used to calculate approximate acoustic matches for arbitrary phonetic transcriptions (one floating-point operation/phone). The speaker-independent system uses WSJ0 data (5000-word vocabulary), with separate male and female models: 3-state full right-context models, and code books of 14 static and 15 dynamic cepstral parameters. The first pass uses VQ models with one covariance matrix and 256 means. The word inclusion rate is about 97%. For the second pass, trigram language models with perplexity 104 and continuous-HMM acoustic models achieved about 90% word-recognition accuracy on the development set. To achieve good trade-offs between acoustic models’ complexity and trainability, a shared-distribution approach for clustering has distortion measures based only on the weights of Gaussian mixtures rather than all parameters. Word accuracy increased by 6% for the ATIS corpus. [Work supported by NSERC-Canada.]
Seafloor backscatter measurements using explosive line arrays
Authors: Holland Charles W. , Neumann Peter
Published: October 2005

Current survey techniques typically measure seafloor backscattering from 30–50 deg in grazing angle. Low-angle measurements (less than about 30 deg) of seafloor backscattering require vertical directionality in the source and/or receiver to eliminate paths that have more than one bottom interaction. Several experiments using explosive line arrays (ELA) have been conducted to explore the potential for measurement of low-angle seafloor scattering. Air deployable explosive line arrays are attractive because they are relatively inexpensive, are command activated, and appear to be quite stable from ping to ping. Seafloor scattering measurements conducted with the ELAs will be compared with co-located measurements using SUS as well as a low-frequency coherent source array. [Work supported by the ONR/AEAS Program.]
High-frequency bistatic scattering by sub-bottom gas bubbles
Authors: Chu Dezhang , Williams Kevin L. , Tang D. , Jackson Darrell R.
Published: October 2005

The acoustic scattering by sub-bottom inhomogeneities has received increased attentions in recent years. However, most of the previous studies were restricted to monostatic or backscattering. To better understand the complicated scattering process, a bistatic scattering involving both grazing and azimuth angles dependence is desirable. As part of the Coastal Benthic Boundary Layer Special Research Program (CBBLSRP), along with a previously reported backscattering experiment, a bistatic scattering field experiment using Mobile Benthic Receiver Arrays (MBRA) operated at 40 kHz was conducted at Eckernfoerde Bay, Germany in April 1993. It has been found in previous studies that high-frequency backscattering measured is due to methane gas bubbles buried about a meter beneath the seafloor. In this paper, a bistatic scattering model is proposed as an extension of the previously developed backscattering model to account for the three-dimensional (out-of-plane) scattering effect. In the model, as in the backscattering model, gas bubbles were assumed to be oblate spheroids with varying aspect ratios. While the parameters used in the model to fit backscattering data are kept unchanged, the model prediction for the bistatic scattering is satisfactory. It is found that the scattering strength exhibits a mild azimuthal dependence and is sensitive to the scattering geometry. [Work sponsored by ONR.]
Measurements of the acoustic (200 kHz) backscatter from a carbonate sediment at low grazing angles
Authors: Altenburg Robert A. , Chotiros Nicholas P.
Published: October 2005

A multibeam sonar, mounted on a remotely operated vehicle, and operated at 200 kHz was used to acquire bottom backscatter data at nine different sites in the Dry Tartugas near Key West, Florida. The bottom in this area is carbonate mud and biogenic carbonate detritus (hermitific corals, shells, etc.). Bottom backscattering strength as a function of grazing angle for each site, supported by bottom core sample analyses, is presented. A wide range of bottom backscattering strength values were measured and some correlation between bottom type and backscattering strength was found. [Work sponsored by ONR under management by NRL/SSC under the Coastal Benthic Boundary Layer Special Research Program.]
Acoustical ray-tracing insonification software modeling of reverberation at selected sites near the Mid-Atlantic Ridge
Authors: Lupien Vincent H. , Bondaryk Joseph E. , Baggeroer Arthur B.
Published: October 2005

The software package ARTIST is used to model reverberation in a series of pings at selected sites in both monostatic and bistatic configurations. ARTIST is a ray-tracing-based program incorporating array positions and orientations, sound-speed profiles, bathymetry, and beam patterns. Simulated beam-time data are generated by integrating the energy at the seafloor from both arrays, incorporating all sidelobe effects. It is shown that prominent features in the beamformed data match excellently with direct and surface-reflected paths to the seafloor and that these features are dominated by shadowing effects and average grazing angles. The received data show appreciable returns in regions where no direct or surface-reflected paths exist. It is postulated that these returns are part of an underlying, slowly varying reverberation envelope which changes little from ping to ping and is present in bistatic cases as well. Possible physical mechanisms leading to this behavior are presented. The scattering strength of selected seafloor features is presented along with its dependence on grazing and bistatic angles.
Construction and tuning of steelpans
Authors: Alexis Clifford
Published: October 2005

During its 50 years of existence, the steelpan has evolved from a folk instrument in its native Trinidad to a versatile instrument capable of performing a wide range of musical styles from symphonic to calypso. Tonal design of the various instruments is approaching standardization but still there is considerable experimentation in the physical design of individual instruments. The construction of the various instruments in the steel drum family is discussed, and the tuning of notes on a cello pan is demonstrated.
Music of the steelband
Authors: Alexis Clifford , O’Connor Allan , Teague Liam
Published: October 2005

Established in 1973 as the first actively performing steelband in an American university, the NIU Steel Band has toured in the United States and Asia, recorded three albums on disk, cassette, and CD, and has performed with five symphony orchestras, including the St. Louis Symphony and the Chicago Sinfonietta. The program will include classical, popular, and calypso selections, as well as a work composed specifically for them which utilizes an East African Amadinda xylophone.
A model for sound absorption by and sound transmission through limp fibrous layers
Authors: Katragadda Srinivas , Lai Heng-Yi , Bolton J. Stuart
Published: October 2005

In recent tests it was found that the measured surface normal impedance and transmission loss of limp, fibrous materials could be predicted more accurately when using an elastic porous material model rather than a rigid porous material model: i.e., the motion of the solid phase was found to be acoustically significant. However, it was noted that if the frame stiffness was set to too small a value in the elastic porous model, the boundary value problem that must be solved to yield the surface impedance or transmission coefficient becomes singular. Thus it was of interest to develop a porous material model in which it is assumed from the beginning that the solid phase may move, but that it has no bulk stiffness. Under these circumstances, the Biot model for elastic porous materials may be simplified to yield a single second-order wave equation governing the propagation of a single wave type in the limp porous material. The solutions to that wave equation in combination with appropriate boundary conditions may then be used to predict either the sound absorption by or sound transmission through layers of limp fibrous material without concerns regarding the numerical stability of the predictions.
On the assumption of normal reaction in acoustic characterization of air-filled rigid porous materials
Authors: Sabatier James M. , Hickey Craig J. , Frederickson Carl K.
Published: October 2005

The ground has been modeled as a rigid air-filled porous media for the purpose of determining the characteristic impedance important to outdoor sound propagation. It is possible to use these models to acoustically measure the porous parameters of the ground important to agriculture. To completely determine the porous parameters, both reflection and transmission measurements must be made. For both measurements, the ground has been considered to be locally reacting giving transmitted signals that propagate in a direction normal to the surface. This is not nessessarily the case. Using the local reaction assumption, transmission measurements only determine the normal component of the propagation constant. This error lowers the caclulated value of the tortuosity. The error in the tortuosity depends on the angle of incidence of the incident signal. There is no effect on the calculated effective flow resistivity. A theoretical determination of the tortuosity correction will be presented along with data that demonstrate the effect. [Work supported by USDA.]