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W M Rabinowitz

Publications and source records attributed to W M Rabinowitz.

30 records · Page 2Linked to original sources
PubMed1988

Preliminary results of speech-reception tests obtained with the synthetic Tadoma system.

In the Tadoma method of speech reception used by some deaf-blind individuals, speech is understood by placing a hand on the face of the talker and feeling certain mechanical actions of the face associated with speech production. The synthetic Tadoma system is a computer-driven artificial face that simulates these mechanical actions. This paper reports some preliminary data on the discrimination of nonsense syllables with the synthetic system. Although further work is required to produce an accurate simulation, the results suggest that such a goal is indeed achievable.

Blindness↗
PubMed1987

Multidimensional tactile displays: identification of vibratory intensity, frequency, and contactor area.

Experiments were conducted to determine the ability of subjects to identify vibrotactile stimuli presented to the distal pad of the middle finger. The stimulus sets varied along one or more of the following dimensions: intensity of vibration, frequency of vibration, and contactor area. Identification performance was measured by information transfer. One-dimensional stimulus sets produced values in the range 1-2 bits and, for most subjects, three-dimensional sets produced values in the range 4-5 bits. Of the three dimensions considered, performance on the intensity variable was most affected, and performance on contactor area least affected, by simultaneous variations in the other dimensions.

Attention↗
PubMed1987

Multimicrophone adaptive beamforming for interference reduction in hearing aids.

To reduce interference in monaural hearing aids from sound sources that are spatially separated from a target source, we are investigating methods for combining information from multiple microphones. In this paper, we describe an adaptive beamforming method that functions to preserve target signals arriving from straight-ahead of a microphone array while minimizing output power from off-axis interference sources. In a preliminary evaluation of a two-microphone system, sentence intelligibility tests were administered to normal-hearing subjects using processed and unprocessed materials from simulated environments in which the target was on-axis, the interference (speech babble) was 45 degrees off-axis, and the reverberation mimicked that of a living room, a conference room, and anechoic space. Compared to listening through a single microphone, the two-microphone beamformer reduced the target-to-interference ratio required to achieve 50 percent keyword intelligibility by 30, 14, and 0 dB in the anechoic, living-room, and conference-room conditions, respectively. The corresponding improvements over binaural listening (one microphone to each ear) were 24, 9, and 0 dB. Further tests in the living-room environment using the same beam-forming system but with filter impulse responses shortened by a factor of four (which would decrease the adaptation time by a factor of four) decreased the improvement by 5 dB. These results are sufficiently encouraging to warrant further tests involving more realistic reverberant conditions, multiple sources of interference, and time-varying acoustic environments.

Acoustics↗
PubMed1985

Research on the Tadoma method of speech communication.

In Tadoma, speech is received by placing a hand on the talker's face and monitoring actions associated with speech production. Our initial research has documented the speech perception, speech production, and linguistic abilities of deaf-blind individuals highly trained in Tadoma. This research has demonstrated that good speech reception can be achieved through the tactile sense: Performance is roughly equivalent to that of normals listening in noise or babble with a signal-to-noise ratio in the range 0-6 dB. It appears that the principal cues employed are lip movement, jaw movement, oral airflow, and laryngeal vibration, and that the errors which occur are caused primarily by inadequate information on tongue position. Our current research includes (1) learning of Tadoma by normal subjects with simulated deafness and blindness, (2) augmenting Tadoma with a supplemental tactile display of tongue position, and (3) developing a synthetic Tadoma system in which signals recorded from a talker's face are used to drive an artificial face. This research is expected to increase our understanding of Tadoma and its relation to other tactile communication methods, show that performance obtained through Tadoma does not represent the ultimate limits of the tactile sense, and provide a research tool for studying transformations of Tadoma.

Adult↗
PubMed1984

Standardization of a test of speech perception in noise.

All 10 forms of the test of Speech Perception in Noise (SPIN) were presented to 128 listeners who had some degree of sensorineural hearing loss. Presentation of the speech track was at 50 dB above the estimated threshold for the babble track. Signal-to-babble ratio was 8 dB. Half of the subjects listened through headphones and half via loudspeaker. Half were tested in a single session and half in two sessions spaced 2-4 weeks apart. Two markers independently scored every test session. Statistical analyses indicate that transducer, number of visits, and order of test form presentation have little or no effect on test scores, and differences between markers, although significant, are quite small. The subtests consisting of items with strong contextual cues generate an average reliability coefficient of .91, whereas the value for the low-context subtests is .85. The 10 forms do not, however, constitute a set of equivalent forms, and there are large differences in mean performance on the low-context portions.

Adult↗
PubMed1984

Intensity perception. XIII. Perceptual anchor model of context-coding.

In our preliminary theory of intensity resolution [e.g., see N. I. Durlach and L. D. Braida, J. Acoust. Soc. Am. 46, 372-383 (1969)], two modes of memory operation are postulated: the trace mode and the context-coding mode. In this paper, we present a revised model of the context-coding mode which describes explicitly a process by which sensations are coded relative to the context and which predicts a resolution edge effect [L. D. Braida and N. I. Durlach, J. Acoust. Soc. Am. 51, 483-502 (1972); J. E. Berliner, L. D. Braida, and N. I. Durlach, J. Acoust. Soc. Am. 61, 1256-1267 (1977)]. The sensation arising from a given stimulus presentation is coded by determining its distance from internal references or perceptual anchors. The noise in this process, combined with the sensation noise, constitutes the limitation on resolution in the model. In the revised model the probability density functions of the decision variable are not precisely Gaussian (and cannot be expressed analytically in closed form). This paper outlines the predictions of the model for one-interval paradigms and for fixed-level two-interval paradigms and derives estimates of the values of model parameters.

Discrimination Learning↗
PubMed1984

Interaction of spontaneous oto-acoustic emissions and external sounds.

Spontaneous oto-acoustic emissions (SOAEs) were detected in eight of 19 ears from 12 persons with normal hearing. On a subset of these individuals, additional characteristics of SOAEs were studied including the suppression of SOAE level caused by an external tone. For suppressor tones below and slightly above the frequency of an SOAE, suppression is quite abrupt (about 5 dB of SOAE level reduction per dB increase in suppressor level); however, as suppressor frequency increases above the SOAE, the rate of suppression decreases. A release from suppression was demonstrated by the interaction of an SOAE with two external tones. When a tone above the SOAE frequency causes suppression, a second tone above the suppressor frequency can cause the SOAE to increase nearly to its ambient level. This finding is interpreted as the second tone having suppressed some aspect of the intracochlear influence of the first tone. The growth rate of this secondary suppression appears to be near 1 dB/dB, a value similar to rates derived from existing measures of two-tone suppression observed in auditory-nerve-fiber recordings in laboratory mammals.

Acoustic Stimulation↗
PubMed1981

Measurement of the acoustic input immittance of the human ear.

A method is presented for measuring acoustic immittance (admittance or impedance) in the human ear canal and its validity is demonstrated for frequencies from 62 Hz to 4 kHz. Special attention is given to estimating the residual ear-canal space between the eardrum and the tip of the measuring device; estimates were determined, in part, using immittances measured with static pressures applied in the ear canal. Immittance estimates at the eardrum are reported for four normal subjects. Below 500 Hz, the immittance is compliance dominated. Our averaged compliance equivalent to 0.70 cc agrees with that reported by others. From 1 to 4 kHz, the immittance is resistance dominated. Our resistance values exceed those generally reported previously; they are, however, similar to those of Mehrgardt and Mellert [J. Acoust. Soc. Am. 61, 1567--1576 (1977)] and to values suggested from analysis of other acoustical measurements on the external ear.

Acoustic Impedance Tests↗
PubMed1980

Two-tone masking in normal hearing listeners.

Psychophysical measurements of two-tone masking [E. Zwicker, Acustica 4, 415-420 (1954)] were made at 0.25, 0.5, 1, 2, and 4 kHz utilizing a masker level of 62 dB SPL/tone. Fifty-eight "untrained" subjects were tested using a single run of a 4IFC adaptive procedure for each condition. Individual data were highly variable. Average data were systematic; they were analyzed using a two-line-regression procedure and the obtained critical-bandwidth estimates approximated normative values. Analysis of the literature revealed that a substantial increase of estimated critical bandwidth versus masker level occurs in two-tone masking. A portion of this increase appears artificial and stems from the relative effectiveness of the higher frequency masker tone at high masker levels. An alternative masker-frequency spacing is suggested to reduce level effects. Implications for an underlying critical-band mechanism are discussed.

Adolescent↗
PubMed1977

Analytic study of the Tadoma method: background and preliminary results.

Certain deaf-blind persons have been taught, through the Tadoma method of speechreading, to use vibrotactile cues from the face and neck to understand speech. This paper reports the results of preliminary tests of the speechreading ability of one adult Tadoma user. The tests were of four major types: (1) discrimination of speech stimuli; (2) recognition of words in isolation and in sentences; (3) interpretation of prosodic and syntactic features in sentences; and (4) comprehension of written (Braille) and oral speech. Words in highly contextual environments were much better perceived than were words in low-context environments. Many of the word errors involved phonemic substitutions which shared articulatory features with the target phonemes, with a higher error rate for vowels than consonants. Relative to performance on word-recognition tests, performance on some of the discrimination tests was worse than expected. Perception of sentences appeared to be mildly sensitive to rate of talking and to speaker differences. Results of the tests on perception of prosodic and syntactic features, while inconclusive, indicate that many of the features tested were not used in interpreting sentences. On an English comprehension test, a higher score was obtained for items administered in Braille than through oral presentation.

Adult↗