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Biomedical subjects

W M Rabinowitz

Publications and source records attributed to W M Rabinowitz.

At least 19 recordsLinked to original sources
PubMed1996

Assessment of blood donor privacy during health history interviews.

BACKGROUND: Given the personal nature of health history interviews, it is important to provide donors with both visual and auditory privacy. Privacy is affected by variables such as background noise, the use of visual screens, and the loudness of the donor's voice. STUDY DESIGN AND METHODS: In Phase I of this study, an interview station and waiting area were simulated. To measure auditory privacy, a speech intelligibility test was given to subjects with and without the use of a free-standing privacy screen and masking noise device. Phase II was a field trial designed to evaluate screens and masking noise. Background noise was measured during each blood collection operation, and donors completed a survey. RESULTS: In Phase I, speech intelligibility test scores ranged from 78 to 5.1 percent, depending on the type of visual screen and the number of masking noise devices used. In Phase II, with the use of screens, 94 percent of donors rated visual privacy as "good to excellent," compared with 74 percent who did so when no screens were used. At many blood drives, the background noise level exceeded the level of the masking noise. CONCLUSION: The use of visual screens increases donors' perception of visual privacy. The use of masking noise is effective only when the health history interview is conducted under conditions of low background noise levels.

Blood Donors↗
PubMed1995

Effects of channel-to-electrode mappings on speech reception with the ineraid cochlear implant.

OBJECTIVE: Research was conducted to assess multichannel saliency with the Ineraid cochlear prosthesis. The goal was to determine whether tonotopically ordered stimulation benefits speech reception. DESIGN: In a single high-performing subject, changes in speech reception were studied during two dramatic alterations to the normal (tonotopic) mapping between the sound-processors's four filter channels and the intracochlear electrode array: In one alteration, the four filter outputs were summed and delivered to one electrode; this single-channel mapping was worn for 7 days. In another alteration, the four filter outputs were connected in reverse tonotopic order to four intracochlear electrodes; this reversed mapping was worn for 3 days. RESULTS: When using the implant in conjunction with speechreading, all three mappings provided large gains over speechreading alone on the recognition of words in sentences. When using the implant alone (without speechreading), tests of consonant and vowel recognition, and the recognition of words in isolation and in sentences all showed substantial decreases in performance across the three mapping conditions: normal > single-channel > reversed. The patterns of segmental confusions and the relations among scores on different tests were highly consistent. Finally, the performance with the altered mappings was, in some ways, remarkably good. With single-channel mapping, 15% word recognition was obtained, much less than the 54% obtained with the normal mapping, but demonstrative of some open-set speech reception. With the reversed mapping, high levels of consonantal voicing and manner information were received, indicating good reception of time-intensity cues, but open-set word recognition was near zero. CONCLUSIONS: Despite the extensive spread of current associated with monopolar intracochlear stimulation, the Ineraid electrode array affords a degree of perceptual selectivity that substantially aids speech reception.

Adult↗
PubMed1993

Intensity perception. XIV. Intensity discrimination in listeners with sensorineural hearing loss.

Intensity discrimination of pulsed tones (also called level discrimination) was measured as a function of level in 13 listeners with sensorineural hearing impairment of primarily cochlear origin, one listener with a vestibular schwannoma, and six listeners with normal hearing. Measurements were also made in normal ears presented with masking noise spectrally shaped to produce audiograms similar to those of the cochlearly impaired listeners. For unilateral impairments, tests were made at the same frequency in the normal and impaired ears. For bilateral-sloping impairments, tests were made at different frequencies in the same ear. The normal listeners showed results similar to other data in the literature. The listener with a vestibular schwannoma showed greatly reduced intensity resolution, except at a few levels. For listeners with recruiting sensorineural impairments, the results are discussed according to the configuration of the impairment and are compared across configurations at equal SPL, equal SL, and equal loudness level. Listeners with increasing hearing losses at frequencies above the test frequency generally showed impaired resolution, especially at high levels, and less deviation from Weber's law than normal listeners. Listeners with decreasing hearing loss at frequencies above the test frequency showed nearly normal intensity-resolution functions. Whereas these trends are generally present, there are also large differences among individuals. Results obtained from normal listeners who were tested in the presence of masking noise indicate that elevated thresholds and reduced dynamic range account for some, but not all, of the effects of recruiting sensorineural impairment on intensity resolution.

Acoustic Stimulation↗
PubMed1993

On the potential of fixed arrays for hearing aids.

Microphone arrays with fixed (time-invariant) weights are directed at enhancing a desired signal from one direction (straight ahead) while attenuating spatially distributed interference and reverberation. Using the theory of sensitivity-constrained optimal beamforming [Cox et al., IEEE Trans. Acoust. Speech Sig. Process. ASSP-34, 393-398 (1986)], free-field arrays of head-sized extents were studied. The key parameters affecting array design and performance are the set of transfer functions from the target direction to each array microphone [H(f)] and the intermicrophone cross-spectral densities for isotropic noise [Szz(f)]. Design variables included the orientation of the array, the number, and [as motivated by Soede, Ph.D. thesis, Delft University of Technology (1990)] the directionality of the microphones within the array, and the complexity and robustness of the required processing. Performance was characterized by the broadband intelligibility-weighted directivity (gain against isotropic noise) and noise sensitivity (reflecting the array's sensitivity to uncorrelated noise, as well as device tolerances). For broadside orientation, a variety of arrays based on cardioid and hypercardioid microphones gave very similar performance. They can provide directivities of 7-8 dB with easily implemented weights (simple scalars). For endfire orientation, as Soede (1990) recognized, similar directivities result with weights based on analog gains and pure time delays. However, with weightings chosen independently for each frequency, directivities up to approximately 11 dB may be obtained, although the increased noise sensitivities of these arrays require practical evaluation. Because of sound diffraction, placement of arrays onto the head potentially impacts both their design and performance. In-situ measurements of H(f) and Szz(f) as well as simplified theoretical models are suggested to explore the optimization of head-mounted arrays.

Acoustic Stimulation↗
PubMed1992

Analytic study of the Tadoma method: improving performance through the use of supplementary tactual displays.

Although results obtained with the Tadoma method of speechreading have set a new standard for tactual speech communication, they are nevertheless inferior to those obtained in the normal auditory domain. Speech reception through Tadoma is comparable to that of normal-hearing subjects listening to speech under adverse conditions corresponding to a speech-to-noise ratio of roughly 0 dB. The goal of the current study was to demonstrate improvements to speech reception through Tadoma through the use of supplementary tactual information, thus leading to a new standard of performance in the tactual domain. Three supplementary tactual displays were investigated: (a) an articulatory-based display of tongue contact with the hard palate; (b) a multichannel display of the short-term speech spectrum; and (c) tactual reception of Cued Speech. The ability of laboratory-trained subjects to discriminate pairs of speech segments that are highly confused through Tadoma was studied for each of these augmental displays. Generally, discrimination tests were conducted for Tadoma alone, the supplementary display alone, and Tadoma combined with the supplementary tactual display. The results indicated that the tongue-palate contact display was an effective supplement to Tadoma for improving discrimination of consonants, but that neither the tongue-palate contact display nor the short-term spectral display was highly effective in improving vowel discriminability. For both vowel and consonant stimulus pairs, discriminability was nearly perfect for the tactual reception of the manual cues associated with Cued Speech. Further experiments on the identification of speech segments were conducted for Tadoma combined with Cued Speech. The observed data for both discrimination and identification experiments are compared with the predictions of models of integration of information from separate sources.

Blindness↗
PubMed1992

Relations among different measures of speech reception in subjects using a cochlear implant.

A comprehensive set of speech reception measures were obtained in a group of about 20 postlingually deafened adult users of the Ineraid multichannel cochlear implant. The measures included audio, visual, and audiovisual recognition of words embedded in two types of sentences (with differing degrees of difficulty) and audio-only recognition of isolated monosyllabic words, consonant identification (12 alternatives, /Ca/), and vowel identification (8 alternatives, /bVt/). For most implantees, the audiovisual gains in the sentence tests were very high. Quantitative relations among audio-only scores were assessed using power-law transformations suggested by Boothroyd and Nittrouer [J. Acoust. Soc. Am. 84, 101-114 (1988)] that can account for the benefit of sentence context (via a factor k) and the relation between word and phoneme recognition (via a factor j). Across the broad range of performance that existed among the subjects, substantial order was observed among measures of speech reception along the continuum from recognition of words in sentences, words in isolation, speech segments, and the retrieval of underlying phonetic features. Correlations exceeded 0.85 among direct and sentence-derived measures of isolated word recognition as well as among direct and word-derived measures of segmental recognition. Results from a variety of other studies involving presentation of limited auditory signals, single-channel and multichannel implants, and tactual systems revealed a similar pattern among word recognition, overall consonant identification performance, and consonantal feature recruitment. Finally, improving the reception of consonantal place cues was identified as key to producing the greatest potential gains in speech reception.

Adult↗
PubMed1991

Better speech recognition with cochlear implants.

HIGH levels of speech recognition have been achieved with a new sound processing strategy for multielectrode cochlear implants. A cochlear implant system consists of one or more implanted electrodes for direct electrical activation of the auditory nerve, an external speech processor that transforms a microphone input into stimuli for each electrode, and a transcutaneous (rf-link) or percutaneous (direct) connection between the processor and the electrodes. We report here the comparison of the new strategy and a standard clinical processor. The standard compressed analogue (CA) processor presented analogue waveforms simultaneously to all electrodes, whereas the new continuous interleaved sampling (CIS) strategy presented brief pulses to each electrode in a nonoverlapping sequence. Seven experienced implant users, selected for their excellent performance with the CA processor, participated as subjects. The new strategy produced large improvements in the scores of speech reception tests for all subjects. These results have important implications for the treatment of deafness and for minimal representations of speech at the auditory periphery.

Cochlear Implants↗
PubMed1990

Robustness of an adaptive beamforming method for hearing aids.

We describe the results of computer simulations of a multimicrophone adaptive-beamforming system as a noise reduction device for hearing aids. Of particular concern was the system's sensitivity to violations of the underlying assumption that the target signal is identical at the microphones. Two- and four-microphone versions of the system were tested in simulated anechoic and modestly-reverberant environments with one and two jammers, and with deviations from the assumed straight-ahead target direction. Also examined were the effects of input target-to-jammer ratio and adaptive-filter length. Generally, although the noise-reduction performance of the system is degraded by target misalignment and modest reverberation, the system still provides positive advantage at input target-to-jammer ratios up to about 0 dB. This is in contrast to the degrading target-cancellation effect that the system can have when the equal-target assumption is violated and the input target-to-jammer ratio is greater than zero.

Computer Simulation↗
PubMed1989

Analysis of a synthetic Tadoma system as a multidimensional tactile display.

The Tadoma method is a means of speech reception based on tactile monitoring of the articulatory process. A "synthetic" Tadoma system, involving an artificial face with six facial actions, has been developed as a first-order approximation to the natural Tadoma system. Experiments were conducted to explore the information-transmission characteristics of the synthetic Tadoma system in terms of the four facial movements it incorporates: upper lip in-out, lower lip in-out, lower lip up-down, and jaw up-down movements. Discrimination experiments showed that the just-noticeable difference associated with each movement is about 9% of the reference displacement. One-dimensional (1-D) absolute identification experiments produced, on the average, 1.6 bits of information transfer. Four dimensional (4-D) identification experiments produced information transfers in the range of 3-4 bits. Of the four dimensions considered, performance on the lower lip up-down movement was most affected, and performance on the jaw up-down movement was least affected, by simultaneous roving movements on the other dimensions. As a result of the interaction among the movement channels, the sum of the 1-D information transfers exceeds the 4-D information transfer. However, the sum of the 1-D information transfers obtained from tests with roving parameters is approximately equal to the 4-D information transfer (possibly exemplifying a "generalized information-transfer additivity law"). In general, both the discrimination and identification results appear unexceptional and, hence, the reception of facial movement information by itself does not appear to account for the extraordinary success of the Tadoma method.

Humans↗
PubMed1989

Manual discrimination and identification of length by the finger-span method.

Experiments were conducted on length resolution for objects held between the thumb and fore-finger. The just noticeable difference in length measured in discrimination experiments is roughly 1 mm for reference lengths of 10 to 20 mm. It increases monotonically with reference length but violates Weber's law. Also, it decreases when the subject is permitted to maintain a constant finger span between trials; however, it tends to increase when the nondominant hand is used. As would be expected from studies of other stimulus dimensions in other sense modalities, resolution is considerably poorer in identification experiments than in discrimination experiments. For stimulus sets that cover a broad range (90 mm), the total information transfer is roughly 2 bits; for those that cover a relatively small range (18 mm), it is roughly 1 bit. The data are analyzed and interpreted using analysis techniques and models that have been used previously in studies of audition (e.g., Durlach & Braida, 1969).

Adult↗
PubMed1988

Ear canal acoustic distortion at 2f1-f2 from human ears: relation to other emissions and perceived combination tones.

Two aspects of the intermodulation distortion product at 2f1-f2 generated by normal human ears and measured acoustically in the ear canal were studied: (1) its relation to tone-evoked and spontaneous otoacoustic emissions, and (2) its relation to the perceived combination tone at the same frequency. With regard to (1), substantial differences among ears in the detectability of emissions were observed; ears tended to exhibit all or none of the emission types that were sought. Within ears possessing emissions, the magnitudes of tone-evoked emissions and acoustic distortion showed a similar dependence on frequency. With regard to (2), a three-primary-tone stimulus was employed to ask whether the ear canal acoustic distortion tone is canceled under the same stimulus conditions that produce perceptual cancellation. Simultaneous cancellation of perceptual and acoustic distortion was produced rarely. Results are interpreted qualitatively with a model in which primary tones produce distortion at their interaction region within the cochlea; this distortion propagates to the distortion-frequency place where it mediates perception. This same distortion wave produces emission components at additional locations, including the primary-tone interaction region, which sum vectorially to mediate the emitted acoustic distortion product.

Acoustic Stimulation↗
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↗