bluuebunny/crossref_metadata_2025 huggingface dataset:
Testing the ‘‘center of gravity’’ effect for vowel-like complex sounds
Authors: Feth Lawrence L. , Lester Julie L. , Xu Qiang , Ross Jaan
Published: October 2005

Chistovitch and Lublinskaya [Hear. Res. 1, 185–195 (1979)] reported that listeners’ judgments of vowel quality are influenced by the relative level of spectral peaks that fall within a critical distance (3.5 Bark). They suggest that the listeners respond to a ‘‘perceptual formant’’ at the spectral center-of-gravity (COG) for the peaks falling within the critical distance. This study was designed to determine whether the COG of the presumed neural excitation pattern might serve as a better predictor of listener performance than the COG of the signal spectrum. Listeners adjusted the center frequency of a simple spectral peak to match the location of the ‘‘perceptual formant’’ in several two- or three-formant signals. The relative level of the surrounding peaks was varied (−20 to +20 dB in 10-dB steps) to shift the location of the perceptual formant. In general, listeners were able to match the perceptual formant at each relative level. However, the matches were tightly grouped about the lower frequency peak when its level was 20 dB greater but more scattered when the higher frequency peak had the higher level. Neither COG of spectra, nor COG of excitation patterns are adequate to explain these differences. [Work supported by AFOSR.]
Discrimination of logarithmically and harmonically spaced static and dynamic spectral profiles with and without roving level
Authors: Drennan Ward R. , Watson Charles S.
Published: October 2005

Listeners’ abilities to discriminate profile stimuli were measured using 11-component profiles with component frequencies from 200 to 2200 Hz. The effects of logarithmic versus harmonic spacing of the components and static versus dynamic temporal contours were examined, with and without roving level (20-dB range). Dynamic profiles had a linear frequency glide with a beginning-to-end frequency ratio of 1.28 Hz. The middle component was always the target. Four listeners in the final experiment were the only ones in an initial group of 22 with thresholds below −10 dB (target re: context). The results showed a strong interaction between component spacing and temporal contour. The dynamic changes hinder performance when the spacing is logarithmic and enhance performance when spacing is harmonic. The results are consistent with and without rove. Drennan and Watson [J. Acoust Soc. Am. 99, 2565(A) (1996)] obtained similar results with less stringently selected listeners tested in a no-rove condition. Stimulus properties that might explain this interaction are considered in terms of recent models of complex auditory pattern processing. [Work supported by AFOSR.]
Effects of tempo changes on auditory pattern discrimination
Authors: Kidd Gary R. , Watson Charles S. , Rogers Catherine L. , Port Robert F.
Published: October 2005

The effect of a change in tempo on the ability to detect frequency changes in sequences of tones was examined after extensive training with four patterns. In a previous study, uniform tone-duration increases of up to 300% were found to have little effect on frequency discrimination thresholds under high-uncertainty testing [G. R. Kidd and C. S. Watson, J. Acoust. Soc. Am. Suppl. 1 84, S141 (1988)]. The present study examined the effect of tempo changes under low-uncertainty testing after prolonged training at a single tempo. Twelve listeners were trained for several days (over 3000 trials) with a set of four isochronous ten-tone patterns (750-ms total duration). Following training, frequency discrimination was evaluated at five tempos (total pattern durations of 375, 536, 750, 1050, and 1500 ms) using a 2AFC remembered-standard paradigm in which one pattern on each trial differed from a training pattern by a single altered frequency. Although the slowest tempo produced a slight threshold elevation for some listeners, only the fastest tempo consistently produced a substantial threshold elevation, with little or no effect of the smaller tempo changes. These results suggest that the representation of both unfamiliar and familiar tone patterns are relatively insensitive to uniform tempo changes. [Work supported by NIDCD and ONR.]
Phase locking to complex stimuli at high sound levels and in noise-damaged ears
Authors: Young Eric D. , Miller Roger L. , Wong Jeff C.
Published: October 2005

Phase locking of auditory-nerve fibers to the vowel /ε/ was studied in normal cats and in cats with a noise-induced hearing loss. In normal cats, phase locking to the formant-frequency components of the vowel dominates responses among fibers with BFs near the formant frequencies. At moderate stimulus levels (50–70 dB), in fact, the responses of such fibers are captured by the formant, in that the fibers respond only to the formant frequency. This synchrony capture is not observed in noise-damaged animals. It is reported here that it is also not observed in normal fibers at high sound levels (near 90 dB). Synchrony capture is a nonlinear phenomenon in that it reflects suppression of response to stimulus components within the tuning curve by the strongest component, at the formant frequency. Using simple cochlear models, the conditions necessary for synchrony capture with a vowel stimulus will be demonstrated and related to the changes occurring in deafened animals and at high sound levels. [Work supported by NIH Grant No. DC00109.]
Magnesium concentration and susceptibility to noise-induced hearing loss
Authors: Walden Brian E. , Henselman Lynn W. , Morris Elena
Published: October 2005

Joachims et al. [J. Acoust. Soc. Am. 74, 104–108 (1983)] reported that magnesium (Mg) intake influenced susceptibility to noise-induced hearing loss (NIHL), with noise-exposed rats fed a Mg-deficient diet incurring significantly greater NIHL than animals fed a Mg-rich diet. Subsequently, Joachims et al. [Mag. Bull. 9, 130–131 (1987)] reported a highly significant negative correlation between serum Mg concentration and NIHL in 24 Israeli Air Force pilots who had been frequently exposed to high-level noise. If reliable, these findings have far-reaching implications for predicting susceptibility and preventing NIHL. This study sought to replicate Joachims et al. (1987) results. Sixty-eight U.S. Army soldiers who had been routinely exposed to potentially hazardous military noise over a 10–15 year period provided pure-tone audiograms following a noise-free period of ≳15 h. Blood samples were obtained following a fasting period of 6–12 h. Samples were analyzed via atomic absorption spectrophotometry to determine the concentrations of Mg in serum, mononuclear cells, and erythrocytes. Results revealed no significant correlation between audiometric thresholds and any of the Mg measures. [Work supported by the Department of Clinical Investigation, Walter Reed Army Medical Center.]
The effects of noise during recovery from an acute acoustic trauma
Authors: Ahroon William A. , Hamernik Roger P.
Published: October 2005

Groups of chinchillas were exposed to ten 160-dB peak SPL reverberant blast waves from a conventional shock tube at a rate of one blast per minute. Immediately following exposure, the animals were (1) returned to the quiet (approx. 40 dBA) animal colony or (2) placed in a 72-dB SPL rms broadband noise for 24 h. The broadband noise caused no temporary or permanent hearing losses nor significant sensory cell losses in a control group of six subjects. Subjects that recovered from the blast-wave exposure in the 72-dB noise averaged significantly more permanent threshold shifts than groups of animals recovering in the quiet animal colony. If the subjects were placed into the quiet animal colony for 2 h immediately following the blast-wave exposure and then allowed to recover for 24 h in the 72-dB noise, their mean permanent thresholds shifts were indistinguishable from the group that recovered in quiet only. Results indicate that there is a short period of time following an acute acoustic trauma in which the cochlea is vulnerable to stimuli that can exacerbate the hearing loss. Therefore, post-traumatic treatment protocols may be developed to reduce hearing loss. [Research supported by the Deafness Research Foundation.]
The effects of continuous and interrupted 1-kHz narrow-band impact noise exposures on hearing: Energy considerations
Authors: Hamernik Roger P. , Ahroon William A.
Published: October 2005

Threshold shifts (TS) which decrease over several days of an interrupted noise exposure, despite continuing exposure, have given rise to the notion of a ‘‘toughened’’ cochlea. The ‘‘toughening’’ phenomena was explored in chinchillas, as the noise peak SPL was varied from 109 to 127 dB. Exposure: A narrow-band (400 Hz), 1 kHz center frequency (CF) impact, presented 1/s; 6 h/day over 20 days or 24 h/day for 5 days. Pairs of exposures with equal peaks had equal energy. Results: Initial TSs of 40 dB developed at 1 kHz and increased very little as impact intensities increased while 3 to 4 octaves above the impact CF, initial TSs increased by as much as 60 dB. ‘‘Toughening,’’ which amounted to 20–30 dB, was typically greatest 2 or 3 oct above the impact CF and tended to shift toward the higher audiometric test frequencies as impact intensity increased. There were no statistically significant differences in PTS or sensory cell losses between the two sets of equal energy exposures. These results suggest that the TTS and PTS components of TS have different substrates and that the decrement in TS, identified as ‘‘toughening,’’ is a modulatable component of TTS. [Research supported by NIOSH Grant No. R01 OH02317.]
The effects of continuous and interrupted narrow-band impact noise exposures on hearing: Frequency considerations
Authors: Ahroon William A. , Hamernik Roger P.
Published: October 2005

The ‘‘toughening’’ effect in chinchillas exposed to interrupted impact noises was explored as the center frequency (CF) of a narrow-band (400 Hz), 115-dB peak SPL impact exposure was varied. CFs were: 0.5, 1.0, 2.0, 4.0, and 8.0 kHz; impacts were presented 1/s, 24 h/day, for 5 days or 6 h/day, for 20 days. Each pair of exposures had equal energy. Results: Initial threshold shifts (TS) for both the 5- and 20-day groups were similar; 40 to 50 dB at the most affected audiometric test frequency. ‘‘Toughening’’ in the interrupted exposures amounted to at most 30 dB. The 1-kHz impact was most effective in producing ‘‘toughening’’ at all audiometric test frequencies that showed a TS. The maximum effect was seen at 4 kHz; two octaves above the impact CF. For impact CFs ≳1.0 kHz the ‘‘toughening’’ effect, when it was measured, was small (<10 dB) and most audiometric test frequencies showed no ‘‘toughening.’’ When PTS and sensory cell losses were compared across the 5- and 20-day exposures, at all impact CFs, there were no statistically significant differences. The TS toughened cochlea is not necessarily a protected cochlea. [Research supported by NIOSH Grant No. R01 OH02317.]
Temporal and spectral factors in loudness sensation
Authors: Zhang Chaoying , Zeng Fan-Gang
Published: October 2005

Loudness has been estimated traditionally based on spectral properties of the sound and critical band analysis of the ear: Spectral components add energy within the critical band and add loudness across critical bands. This traditional model is successful in predicting loudness of steady-state sounds but has not been verified with dynamic sounds like speech. This study conducted three experiments using modern loudness balance procedures to study temporal and spectral factors in loudness sensation. Experiment 1 repeated Zwicker’s two-tone and three-tone complex experiment in which frequency and phase differences between tones were varied systematically [Zwicker and Fastl, Psychoacoustics (Springer-Verlag, 1990), pp. 189–190]. While the results generally were consistent with the traditional model, a deviation occurred for the frequency difference less than 10 Hz, where loudness was affected by the low-frequency temporal envelope and was greater than that predicted by the energy summation model. To further separate spectral from temporal factors and to rule out the influence of critical bands, experiment 2 used sinusoidally amplitude-modulated noises in normal-hearing listeners and experiment 3 used cochlear implant listeners. Data from experiments 2 and 3 indicated that the temporal envelope in modulated stimuli can increase loudness by 3 dB compared with unmodulated stimuli of equal rms level.
An effect of temporal energy distribution on loudness
Authors: Stecker G. Christopher , Hafter Ervin R.
Published: October 2005

This study examines the effect of dynamic changes in signal amplitude (temporal energy distribution) on loudness. Pure-tone (330-Hz) signals were gated with asymmetric temporal envelopes whose rise and fall times were unequal. These were presented either forward or reversed in time so that peak amplitudes appeared either early or late in the signals. Subjects judged late-peaking signals to be louder than early-peaking signals. The result is not in accord with an automatic gain control (AGC) model, which would predict that signals with a more rapid rise time would be less affected by AGC and thus appear louder. Alternative explanations to be discussed include (a) forward masking of the stimulus tail by the onset, and (b) a form of perceptual constancy whereby the slowly decaying stimulus tail is treated as reverberation and thereby not included in the judgment of loudness. [Work supported by NSF 9355034 and NIDCD 00087.]
Cavitation threshold measurement by spectral observation
Authors: Takahashi Sumio , Takahashi Nobuaki
Published: October 2005

The spectrum of acoustic pressure was measured as a function of excitation level of the transducer in distilled water, salt water, and seawater using an acousto-optic detection system. A cylindrical piezoelectric transducer was used. The sensing beam of an optical heterodyne interferometric system passes through the center of the transducer where cavitation is produced, and the acoustic pressure is detected. The acousto-optic detection does not disturb the acoustic field. The heterodyne output was demodulated and observed by the spectrum analyzer. Cavitation thresholds of seawater and distilled water were compared by observing the spectral change against the excitation level. The dip of the spectral level of harmonic components or the emergence of subharmonic and anharmonic components is characteristic of cavitation inception. The measurements were conducted in both cases: One is the case where the sensing beam passed through the cavitation site and the other is the case where the sensing beam passed near the cavitation site.
Otoacoustic emissions and threshold shift correlations following asymptotic threshold shift producing noise exposures
Authors: Jock Brenda M. , Hamernik Roger P. , Ahroon William A.
Published: October 2005

Cubic distortion product emissions (3DPE) were measured in four groups of chinchillas (N=4 or 5/group) exposed for 5 days, 24 h/d, to 121-dB peak SPL, narrow-band (400 Hz) impacts having center frequencies (CF) of 1.0, 2.0, 4.0, or 8.0 kHz. The noise exposure produced an asymptotic threshold shift (ATS) at audiometric test frequencies showing a threshold shift (TS). Levels of ATS up to 80 dB were measured at and above the CF of the impact. Surprisingly, the 1.0- and 2.0-kHz CF impacts produced the largest ATS at 16 kHz. There was, in general, a congruence between the ATS and 3DPE changes following exposures to CFs ≥2.0 kHz. However, with the 1.0-kHz CF impact exposure, the two metrics were not in general agreement. Relations among permanent thresholds shifts (PTS), 3DPEs and outer hair cell (OHC) losses were quite variable for low- and mid-frequency (≤2.0 kHz) biased lesions. For the 4.0- and 8.0-kHz CF impacts, 3DPE changes reflected OHC losses and PTS rather closely. DPEgrams using primary levels of 40 through 70 dB SPL in 10-dB increments were found to be most effective in the evaluation of OHC lesions than was any single DPEgram. [Research supported by NIOSH Grant No. R01 OH02317.]
Temporal aspects of pitch perception at high and low S/N ratios
Authors: Ciocca Valter
Published: October 2005

The study investigated the integration of nonsimultaneous frequency components into a single pitch in quiet and in noise. Using a pitch matching paradigm, the shifts produced by a mistuned harmonic in the pitch of a target complex were measured either with a pre-target component (when the mistuned component stopped as the target started) or with a post-target component (when the mistuned component immediately followed the target tone) [J. Acoust. Soc. Am. 98, 2946(A) (1995)]. The stimuli were presented in quiet or in the presence of a band of noise, low-pass filtered at a frequency cutoff of 3 kHz (approx. −23-dB S/N ratio around the frequency of the mistuned component). In quiet, post-target and simultaneous mistuned components produced larger pitch shifts than pre-target components. In noise, shifts in the pre-target condition were identical to those produced by simultaneous and post-target components. The duration of the interval which separated the nonsimultaneous components and the target tone was varied in a second experiment. The results suggest that the period over which nonsimultaneous components contribute to the pitch of the target is longer in noise than in quiet for both pre- and post-target conditions. [Work supported by HKRGC Grant No. HKU362/94M.]
Auditory short-term memory interference: Deutsch’s demonstration revisited
Authors: Ueda Kazuo
Published: October 2005

The effect of intervening sounds on pure-tone pitch recognition was investigated. Intervening sounds were (1) none, (2) pure tones, and (3) naturally spoken numbers uttered by a female and a male speaker. Nine subjects who possessed no absolute pitch were tested for (1) pure-tone pitch recognition, (2) serial recall of the spoken numbers, and (3) both pitch recognition and number recall. GLM analysis was performed on the arcsine transformed error rates. It revealed that, when the intervening sounds were numbers, the pitch recognition error rates were significantly increased for 4.6%–16.6% if number recall was also required, and vice versa (0.9%–16.6% increases in number recall error). Contrary to the previous notion [D. Deutsch, Science 168, 1604–1605 (1970)], these results indicate that a number recall task does interfere with pure-tone pitch recognition, and that speech sounds interfere with pure tones in auditory short-term memory. Although the pure tones caused larger pitch recognition interference than the spoken numbers for 2.8%–32.4%, this should be attributed to the fact that pitch of speech is less distinct than that of a pure tone.
Infants’ perception of the pitch of rippled noise
Authors: Clarkson Marsha G. , Rogers E. Christine , Miciek Sheridan G.
Published: October 2005

Previous research has revealed qualitative parallels between infants’ and adults’ perception of the pitch of the missing fundamental, yet it is unclear whether infants’ performance is quantitatively the same as adults’. To begin to quantify some aspects of infants’ pitch processing, 7-month-old infants’ detection of an iterated rippled noise (IRN) was tested in a conditional head-turn procedure. A 500-ms Gaussian noise was repeated at a rate of 1/s, and infants learned to turn their heads when an IRN (with a delay of 2 ms, no attenuation applied to the delayed signal, and 16 iterations) was presented for 6 s. The parameters of the IRN represented a delay that is in the middle of the ‘‘best’’ pitch range for adults; an attenuation that produces the strongest pitch for adults; and a number of iterations that provides a very clear pitch for adults. Throughout testing the overall stimulus level roved from 63 to 67 dBA (over a background of 28 dBA). All infants reliably detected the introduction of the ripple in the spectrum, indicating that infants, like adults, can detect the pitch of IRN. Future research will address the questions of how well and under what conditions infants can discriminate IRN. [Work supported by NICHD and NIDCD.]
Infants’ sensitivity to broadband noise
Authors: Werner Lynne A. , Boike Kumiko
Published: October 2005

Detection thresholds for broadband noise bursts were measured for 6 to 10-month-old infants and for young adults. The noise bursts were 500 ms in duration, repeated four times with 500 ms between bursts. The stimulus was presented monaurally using an insert earphone. Listeners learned to respond when they heard noise bursts, but not at other times. The probability that noise bursts would be presented on any trial was 0.5. A one-up, two-down adaptive procedure was used to estimate thresholds. The difference between the average infant threshold and the average adult threshold for noise bursts was 6–7 dB. This is in contrast to an average threshold difference of about 15 dB for a 1000-Hz tone [Bargones et al., J. Acoust. Soc. Am. 98, 99–111 (1995)]. Infants greater relative sensitivity for broadband noise is consistent with the hypothesis that infants do not listen selectively in the frequency domain. Immaturity of the middle ear and inattention may account for the difference between infant and adult thresholds for broadband noise. [Work supported by NIDCD DC00396.]
A fundamental study of hearing aids for music
Authors: Saito Mutsumi , Tsumura Takashi
Published: October 2005

The purpose of this study is to develop compensation methods for the hearing disorders of hearing-impaired persons listening to music as well as to speech. In this study the difference in effectiveness of compensation methods between speech and music was investigated. Several compensation processes (equalization and compression) were subjectively evaluated with adjective pairs in both speech and music. In this experiment the signal processing was run only for simulating a certain hearing disorder including recruitment characteristics. The results show that ‘‘naturalness’’ and ‘‘easiness’’ relate to overall evaluation in music perception, while ‘‘clearness’’ relates to overall evaluation in speech perception.
Electron microscopic histochemistry for acetylcholinesterase in the dorsal cochlear nucleus of rat
Authors: Yao Weiping , Godfrey Donald A.
Published: October 2005

Acetylcholinesterase (AChE), the enzyme which catalyzes hydrolysis of the neurotransmitter acetylcholine, is located in cholinergic neurons, cholinoceptive neurons, and extracellularly in the synaptic clefts of cholinergic synapses. In the rat cochlear nucleus, high activities of AChE have been found in locations rich in granule cells. In the rat dorsal cochlear nucleus (DCN), light microscopic histochemistry for AChE is characterized by stained dots and some patches, especially in its middle, fusiform soma layer, which contains a dense population of granule cells. The fine structure of AChE staining in the DCN has not previously been described. Electron microscopic histochemistry for AChE was performed on perfusion-fixed rat brains. Preliminary results indicate that AChE is distributed differentially across DCN layers. In the molecular layer, AChE staining was found in the extracellular space between nerve fibers and inside the cytoplasm of some dendrites. In deeper layers, extracellularly located AChE was less common, but staining was found inside some of the larger dendrites, some large neuron somata (probably fusiform cells), and some glomeruluslike structures. There appeared to be some labeled fibers coursing in the acoustic striae. [Supported by NIH Grant No. DC00172.]
Electrophysiological and behavioral measurements of spectro-temporal processing: Comodulation masking release
Authors: Eddins David A. , Eddins Ann Clock
Published: October 2005

Behavioral experiments using the comodulation masking release (CMR) paradigm indicate that the auditory system is able to encode and compare the temporal characteristics of stimuli across multiple frequency regions. Such processing leads to improved signal detection under certain masking conditions. While there is growing electrophysiological evidence of the coding of temporal patterns at a single spectral region (e.g., the envelope-following response), few electrophysiological studies have demonstrated (directly or indirectly) across-frequency processing of temporal patterns. In the present study, behavioral and electrophysiological estimates of signal detection were obtained in masking conditions that typically lead to a CMR. Detection by normal-hearing human adults was estimated behaviorally using an adaptive staircase technique and electrophysiologically by recording late auditory-evoked potentials (N1-P2). Thresholds were estimated for a 1000-Hz sinusoidal signal (100-ms duration) in the presence of continuous, narrow-band noise maskers. Masker conditions included a single narrow-band noise masker centered at 1000 Hz and maskers composed of five noise bands (centered at 600, 800, 1000, 1200, and 1400 Hz) having either independent or identical (comodulated) temporal envelopes. Behavioral results indicated a masking release of about 8 to 12 dB while physiological estimates revealed somewhat smaller, but substantial, CMRs.
Outer hair cell stereocilia attachment to the tectorial membrane
Authors: Santi Peter A. , Tsuprun Vladimir L.
Published: October 2005

In the chinchilla, attachment of the hair cell stereocilia to the tectorial membrane appears to occur at the distal tips of the longest rows of stereocilia of the outer hair cells. The present report investigates the macromolecules involved in this attachment and their relationship with the type B fibrils of the tectorial membrane. Cochleas were fixed and stained with glutaraldehyde/Cuprolinic blue and revealed sulfated macromolecules at the tips of the longest rows of the outer hair cell stereocilia. These macromolecules extend from the tips of the stereocilia into cup-shaped attachment sites of the tectorial membrane which consist only of type B fibrils. It is not know whether these macromolecules form direct or indirect links with the type B fibrils of the tectorial membrane. This attachment would provide a firm contact between the tectorial membrane and the hair cell. However, since these attachments are limited only to the distal tips of one row of the hair cell stereocilia they may be vulnerable to acoustic overstimulation. [Work supported by the NIDCD.]
A case of hearing loss due to bilateral temporal lobe infarction
Authors: Tanahashi Teiji , Tanahashi Kyoko
Published: October 2005

A 40-year-old, right-handed female showed cortical deafness and aphasia following a brain stroke. A CT scan showed that a low-density area occupied both of the temporal lobes. In the basal ganglia and thalamus no lesions were observed. Results of audiological examination were as follows. (1) Pure-tone audiometry revealed a mild bilateral hearing loss. An audiogram showed a type of C4 dip. (2) Békésy audiometry showed that the thresholds were extremely unstable. (3) Speech audiometry showed very poor discrimination scores. (4) Discrimination of musical instruments was remarkably poor. (5) An aural reflex test showed normal responses. (6) The auditory brain-stem response elicited by click stimuli was normal in pattern and latency. (7) Middle latency response was almost normal. Auditory function in the cochlea and the brain stem appeared to be almost intact, but cortical and/or subcortical damage of hearing function was suspected bilaterally. The conclusion from these data is that bilateral partial temporal lobe infarction produced a clinical picture of cortical deafness.
Optically measured spatio-temporal distribution of excitation and inhibition evoked by two-tone sequences within the guinea pig auditory cortex
Authors: Horikawa Junsei , Hosokawa Yutaka , Nasu Masahiro , Taniguchi Ikuo
Published: October 2005

Spatio-temporal distributions of excitation and inhibition in the anterior (A) and dorsocaudal (DC) fields of the guinea pig auditory cortex after two-tone stimuli were studied in anesthetized animals (Nembutal 30 mg/kg) using an optical recording method (voltage-sensitive dye RH795, 12×12 photodiode array). Each first (masker) and second (probe) tone was 30 ms long and the probe delay was varied from 30 to 150 ms. Frequencies of the masker and the probe were either the same or octave-separated. With same-frequency pairs, responses to the probe were suppressed completely after probe delays of less than 50 ms and the inhibition lasted for 130 ms. With different-frequency pairs, they were not suppressed completely even after probe delays as short as 30 ms, and the inhibition lasted for only 90–110 ms. The magnitude of the inhibition induced by the same-frequency masker was very similar among locations within the cortical fields, but that by the different-frequency masker differed according to the location. These results are discussed in terms of spectro-temporal masking effects. [Work supported by HFSP and the Ministry of Education in Japan.]
Response characteristics of neurons in columnar organization of the primary auditory cortex of Mongolian gerbils
Authors: Sugimoto Shunji , Sakurada Masaki , Horikawa Junsei , Taniguchi Ikuo
Published: October 2005

Response characteristics of neurons in each column of the primary auditory cortex (Al) of Mongolian gerbils were studied by single-unit recording. Tone-burst stimuli were presented to the ear contralateral to the recording side. During a near-radial microelectrode penetration of Al in steps of 100 μm, best frequencies (BFs), best thresholds, best amplitudes (BAs), latencies, tuning curves, and Q10 dB’s, defined as BF/(frequency bandwidth 10 dB above the best threshold), were measured. Neurons in single penetrations had similar BFs, showing columnar organization of frequency, but had various values of best thresholds (19.1–81.3 dB SPL), BAs (44.9–102.1 dB SPL), latencies (5–80 ms), and Q10 dB’s (0.34–17.53). There was a tendency for high Q10 dB’s to be located around layer IV, while there was no tendency in the distribution of low Q10 dB’s, best thresholds, and BAs. These results provide a layer specificity of tuning properties within a single column of frequency.
Electrode interactions measured by loudness summation in cochlear implant listeners
Authors: Fu Qian-Jie , Shannon Robert V. , Zeng Ian-Gang , Chatterjee Monita
Published: October 2005

Electrode interactions in a multichannel cochlear implant have been assumed to be a key factor affecting speech recognition performance. This study investigates whether loudness summation can estimate the degree of interaction between electrodes and whether the electrode interaction can be modeled mathematically. Thresholds and uncomfortable loudness levels in a two-electrode stimulation were measured in cochlear implantees, where the distance between electrodes was varied systematically. In two-electrode simultaneous stimulation, for two totally dependent electrodes, threshold was reached when the sum of current levels on the two electrodes equaled the threshold of either electrode. On the other hand, for two independent electrodes, threshold was not reached until the current level exceeded the threshold of either electrode. These data are consistent with linear summation of electrical fields. In the suprathreshold measure, loudness was due to the summation of electrical field strength, or loudness sensation, or both. A model has been developed to account for both the effect of electrical field summation in the cochlear and the effect of loudness summation in the sensation. Electrode interaction data will be related to speech recognition performance in these subjects. [Work supported by NIH.]
Frequency resolution and phoneme recognition by hearing-impaired listeners
Authors: Van Tasell Dianne J. , Clement Bart R. , Schroder Anna C. , Nelson David A.
Published: October 2005

The relationship between auditory frequency resolution and speech perception was investigated in 11 hearing-impaired listeners who differed widely in terms of hearing-loss severity, hearing-loss configuration, and frequency resolution abilities. First, the function relating articulation index (AI) to percent correct phoneme recognition was determined for 19 normal-hearing listeners at a variety of speech levels and S/N ratios. Eleven hearing-impaired subjects were then tested with the same speech materials throughout a wide range of AI conditions. Simultaneous-masked psychophysical tuning curves were also obtained at probe frequencies of 0.5, 1, 2, and 4 kHz from all hearing-impaired subjects. When phoneme recognition scores were weighted by AI, the performance of 10 of the 11 hearing-impaired subjects was within normal limits. A modest correlation was observed between high-frequency tuning curve slope and the error in the AI prediction relative to the normal AI data. Results indicate that although listeners with poor frequency resolution tend not to be able to extract as much information from the acoustic speech signal as normally hearing listeners, their phoneme recognition abilities are nevertheless not greatly diminished. [Work supported by NIDCD DC00110.]
Spatial auditory augmentation of visually guided tasks
Authors: Elias Bartholomew
Published: October 2005

The ability of the auditory system to provide localization cues beyond the field of view provides individuals with critical directional information needed to visually acquire objects in the periphery. In recent years, the performance benefits of augmenting visual tasks with stationary auditory cues have been demonstrated in numerous laboratory studies. The research program described in this presentation adds to these initial findings by demonstrating that dynamic auditory cues conveying information regarding object position, velocity, and trajectory can aid performance in visually guided tasks. In the first experiment, the effects of spatial auditory preview cues were examined in a visual target aiming task. A moving sound source provided cues regarding the position and velocity of a moving visual target prior to its appearance on the visual display. The provision of the dynamic spatial auditory cue significantly reduced error magnitudes in aimed firing responses directed at the visual target. In the second experiment, headphone simulations of spatial auditory cues provided preview information regarding target position, velocity, and trajectory beyond the field of view in a dynamic visual search task. The provision of spatial auditory preview cues significantly reduced response times and error rates in acquiring and identifying the dynamic visual targets.
Masker fluctuation and the masking level difference
Authors: Grose John H. , Hall Joseph W.
Published: October 2005

The cues for detecting an Sπ signal masked by an No noise are driven by the signal-to-masker ratio. If the detection process can resolve epochs of low-masker energy such as dips in a fluctuating masker, it would be expected that greater weight would be given to portions of the signal which occur during these epochs. This prediction was tested using the time-domain version of COSS analysis [S. Buus et al., J. Acoust. Soc. Am. 99, 2288–2297 (1996)]. The masker was a 50-Hz-wide noise centered at 500 Hz; the signal was a train of six 500-Hz tone bursts each 50 ms in duration. The level of each tone burst was independently perturbed during each trial around levels previously determined for both NoSo and NoSπ thresholds. For each signal phase condition, 5000 trials were collected from each of four listeners, yielding a total of 30 000 signal+masker combinations per listener. The listeners’ responses were analyzed with respect to both signal level and corresponding short-term masker level. Results showed that listener weights were relatively constant across all short-term masker levels for the NoSo condition but, for the NoSπ condition, were higher during masker dips and lower during masker peaks. [Work supported by NIDCD.]
Localization interference between free-field signals
Authors: Jensen Eric R. , Hafter Ervin R.
Published: October 2005

With headphones, the perceived lateral position of one frequency band (the target) can be affected by the presence of a second band with different interaural parameters (the interferer). This binaural interference persists despite a stimulus onset asynchrony (SOA) from interferer to target of up to 320 ms [L. R. Bernstein and C. Trahiotis, J. Acoust. Soc. Am. 94, 735–742 (1993)]. The current study presented targets and interferers in anechoic space from pairs of speakers chosen from an array of 12. A visual pointer was used to indicate the perceived location of the target. Localization of a sinusoidally amplitude-modulated (SAM) target (carrier = 500 Hz, modulator = 250 Hz) was unaffected by the presence of an SAM interferer (carrier = 4000 Hz). When the target was the higher frequency, however, there were large individual differences, with some listeners showing interference while others did not. Unlike the studies with headphones, when interference was seen a distractor to target SOA of only 40 ms was sufficient to eliminate the interference. [Work supported by a grant from the NIH, NIDCD 00087.]
Interaural-delay sensitivity to frequency modulation
Authors: Saberi Kourosh
Published: October 2005

Data are presented on experiments that compare binaural sensitivity to sinusoidal amplitude and frequency modulation (SAM and SFM). Among the stimulus parameters examined are carrier frequency (3–8 kHz), modulation rate (25–800 Hz), and depth (β=0.1–2). Observers are most sensitive to interaural delays in SAM tones at rates of about 50 to 300 Hz, while for SFM tones, best sensitivity occurs at rates of 200 to 400 Hz. Interaural-delay thresholds for SFM tones are quantitatively predicted from a stochastic AM-envelope model whose parameters are uniquely determined from data on SAM tones. The model uses short-term cross-correlation analysis of Hilbert envelopes at the outputs of a bank of peripheral bandpass filters. The envelopes are subsequently convolved with the impulse response of a low-pass FIR filter, followed by additive noise, and a decision device whose output is a position estimate. The expected value and variance of estimates are stochastically approximated, from which the model adaptively tracks the 0.707 probability of a correct response (d′=0.78) on the observer’s forced-choice psychometric function. [Work supported by NIH.]
Effect of interaural intensity and time difference on the neuronal activity pattern of the guinea pig auditory cortex observed by optical recording
Authors: Hosokawa Yutaka , Horikawa Junsei , Nasu Masahiro , Taniguchi Ikuo
Published: October 2005

The effects of interaural intensity difference (IID) and interaural time difference (ITD) on neural activity in the pentobarbital-anesthetized guinea pig auditory cortex were studied by optical recording with a 12×12 photodiode array. The exposed auditory cortex was stained with a voltage-sensitive dye (RH795). Optical signals were recorded and transformed into sequential two-dimensional images. When both ears were stimulated dichotically by tone bursts (14 kHz, 75 dB SPL), excitatory responses appeared in anterior (A) and dorsocaudal (DC) fields of the auditory cortex. The increase in intensity of ipsilateral stimulation from 75 to 95 dB SPL while the contralateral intensity was kept constant (75 dB SPL) caused a decrease in neural activity of isofrequency bands in fields A and DC. The increase of ipsilateral leads from 0 to 10 ms resulted in a gradual decrease of amplitude of the excitatory responses. Strong inhibition induced by the ipsilateral lead was observed in field DC and the ventral portion of field A. The ipsilateral lead which induced large inhibition was much longer than the time difference (80 μs) calculated from the interaural distance of the guinea pig. These results indicate that IID is more important than ITD for sound localization in the guinea pig. [Work supported by HFSP and the Ministry of Education in Japan.]
Understanding variability in speech: A requisite for advances in speech synthesis and recognition
Authors: Stevens Kenneth N.
Published: October 2005

Current systems for speech recognition and synthesis are limited by our incomplete knowledge of the variability in the acoustic properites of speech sounds depending on the context, the speaker, and the mode of speaking. A biproduct of this variability is that there is redundancy in the acoustic correlates of phonetic units, and this redundancy can be used to advantage when speech is modified by noise or other distorting influences. A goal of research in the next decade is to quantify these sources of variability and to incorporate this knowledge into models for speech generation and reception. Variability in the acoustic properties of speech sounds is a consequence of articulatory variability. This process is illustrated with data for place-of-articulation features for stop consonants in English, and with formant data for the vowels /ε/ and /■/. There is systematic variation in the bursts and formant transitions for individual stop consonants across speakers and contexts that can be explained in terms of shapes of cavities anterior and posterior to the consonant constriction. Variability in formants for the vowels can be accounted for by the requirements on the tongue-body position and tongue-body dynamics for the adjacent segments. [Supported in part by NIH Grant DC02978.]
Toward cross-language global communications
Authors: Yamazaki Yasuhiro , Sagisaka Yoshinori , Higuchi Norio
Published: October 2005

In the upcoming 21st century, the demand for ‘‘global communication among speakers of different languages’’ will become more and more pressing. According to recent survey results, spontaneous speech translation will come into practical use by about 2010–2020. Despite the great expectations of society for efficient speech translation systems, there remain a number of difficult problems related to acoustic and linguistic phenomena yet to be overcome. In particular, the variety of spontaneous speech makes it difficult to simply extend current work done on read speech. For example, speech rate can vary considerably and there are often disfluencies and diversities of pronunciation (with ensuing spectral variations) resulting from different speaker characteristics and situations. This presentation describes research targets for the year 2000 for spontaneous speech translation, emphasizing improvements in speech recognition, prosody processing, synthesis of natural-sounding speech, and system integration, for spoken-language translation between Japanese and other languages such as English, Korean, and German. This research activity is being carried out under international collaborations by the international Consortium for Speech Translation Advanced Research (C-STAR II), which was established in 1994 to begin research activities aimed at an international experiment on multilanguage speech translation planned for 1999.
The role of speech processing in the multimedia communications revolution
Authors: Rabiner Lawrence
Published: October 2005

Historically, the first major revolution in communications occurred around the turn of the 20th century when the concept of ‘‘Universal Service’’ became the rallying point for creating a system where everyone had access to a telephone and could connect automatically and without operator assistance to any other telephone user. The next major revolution in communications, which began about a decade ago and will take us well into the next century, promises to deliver to every home and office the capability of multimedia communications with seamless, and easy-to-use, integration of voice, image, video, handwriting, and data. Speech processing plays a major role in this communications revolution by providing the coding technologies that allow people to efficiently store and transmit speech and audio, and by providing machines with a mouth (to speak to a customer), with an ear (to listen to a customer), and with the ability to understand what is being spoken. Related work in user interfaces provides the easy-to-use mechanisms for technology integration. This talk will review the current status of technology in several areas of speech processing and will discuss the research and technology opportunities that will be seen in the next several years.
Speech in multimodal human–machine communication
Authors: Mariani Joseph J.
Published: October 2005

Speech communication with machines is a research area per se and includes speech recognition and synthesis, as well as speaker or language recognition. Large efforts have been devoted in that field, and much progress can be reported from the recent past. However, it appears that communication between humans usually involves different modalities, such as speech and face/lip ‘‘reading.’’ It results in a more robust communication, or may allow for a more natural and more efficient communication when speech is used together with gesture and vision. Bringing this multimodal communication ability to the field of human–machine communication is now a big challenge and raises difficult problems, such as the integration over time of speech and gesture stimuli, or the use of a common visual reference shared in a human–machine dialog. Another interesting aspect of the work in this area is the possibility of transferring the information from one modality to another, such as vision to speech, or speech to gesture, in order to help handicapped people to communicate better with the machine. Finally, it is thought that, in the long term, the study of multimodal training is necessary in order to develop a single communication mode system.
Modeling of spoken dialogue
Authors: Shirai Katsuhiko , Morikawa Emi
Published: October 2005

Recent progress in the fundamental technologies, including speech signal processing, statistical modeling, and language processing, gives a high performance of speech understanding. However, the speech interface that can communicate with humans naturally has not been constructed yet. In order to realize such a system, it is necessary to analyze how humans behave when they communicate with each other by speech and to implement the structure of the spoken dialogue into the speech conversational system. This paper will describe the results obtained by analyzing several different types of spoken dialogue. A nontask oriented dialogue model is introduced on the basis of the dialogue corpora for several tasks, and is integrated into the speech conversational system. The dynamic structure of the function of each utterance, turn-taking, interrupt, and so on, can be modeled by the statistical method. The same method is applicable for the case in which the visual information channel exists along with the speech channel. In the coming multimodal dialogue system of the future, the use of visual information will be useful and both auditory and visual channels should be modeled simultaneously.
Adaptive language and semantic models
Authors: De Mori Renato
Published: October 2005

In a spoken dialogue system, semantic interpretations are based on relations with words and phrases. Automatic learning of these relations is discussed and a solution based on semantic classification trees is presented. Interpretations can be complete if they provide the dialogue component with all the required information needed to produce an answer to the user. They can also be incomplete or there may be more than one complete or incomplete interpretations in competition, due to inherent ambiguities of the spoken message or to imprecision of the recognizer. Solutions for semantic completion and disambiguation will make dialogue systems more powerful and flexible. Preliminary results and future perspectives are discussed. Conceptual and language models (LM) can be dynamically adapted taking the dialogue history into account. Histories can be clustered into ‘‘dialogue situations’’ by considering the predicates used in the logic formula for generating an output message and selecting the one that is more likely to condition the answer. A dynamic probability can be expressed as combination of LM probabilities in various situations. Each probability is weighted according to the dialogue situation. Better LMs conceived with these principles will make future dialogue systems more robust.