Search PubMed⌕ Search

Biomedical subjects

R E Eilers

Publications and source records attributed to R E Eilers.

At least 37 records · Page 2Linked to original sources
PubMed1991

Optimization of automated hearing test algorithms: simulations using an infant response model.

Computer simulation was used to evaluate several parameters of an automated hearing test algorithm in an attempt to optimize the algorithm for accuracy and efficiency. An infant response model was developed to guide the simulations. Test parameters of interest were starting intensity and stopping rule and their interaction with a measure that is thought to emulate infant reliability, probability of task orientation. Results indicated that stopping rule, within the ranges investigated, had little effect on accuracy but had major impact on efficiency. Starting intensity interacted with the hearing status of pseudosubjects in influencing accuracy. Accuracy was most influenced by probability of task orientation. The simulated test data are compared to data from infants and young children in the accompanying article so that the response model can be evaluated.

Algorithms↗
PubMed1991

Optimization of automated hearing test algorithms: a comparison of data from simulations and young children.

A five-up, five-down automated staircase procedure was used to explore the effects of variable starting and stopping rules as they interact with infant behavior in influencing the accuracy and efficiency of infant auditory threshold testing. Results from 146 infants were compared to results from computer simulations (see accompanying article) in order to evaluate an infant response model used in the simulations. Results indicate that the automated procedure successfully discriminated between infants with normal versus abnormal tympanograms. In addition, the model accurately predicted infant results in terms of the effects of starting and stopping rules. The model was less useful in predicting the relationship between minimum response levels and false positive rates.

Algorithms↗
PubMed1991

The stop/glide boundary shift: modelling perceptual data.

Research in speech perception has suggested that listeners often adjust category boundary locations for differing contexts. The stop/glide (e.g.,/ba/vs./wa/) boundary shift occurring with changes in syllable duration has been interpreted as reflecting 'rate normalization' by some, whereas others have suggested an auditory basis for the shift. Clarification of both the causes and the effects of the stop/glide shift is being sought through experimentation intended to expand our knowledge of variations in the shift across different experimental treatments. The present study extends research on the stop/glide shift by (1) showing that the shift is not an artifact of a particular stimulus pattern that had been present in all the previous studies of the effect, (2) further demonstrating the nonlinear character of the identification shift, (3) providing additional evidence of the role of presentation format (mixed vs. blocked) in the identification shift, and (4) exploring boundary locations in various discrimination paradigms. The complex outcomes of the studies reported here as well as a variety of previous results are interpreted as compatible with expanded versions of the durational contrast hypothesis. Two versions are considered, one in which the shift is seen as due to a mechanism of contrastive perception that applies to events of comparable duration, and one in which the shift is seen as a perceptual error that occurs when the auditory system attempts to track frequency trajectories that change (i.e., pivot) over time.

Adult↗
PubMed1990

Computer methods for on-line hearing testing with auditory brain stem responses.

On-line computer methods were developed and evaluated for automated hearing testing with auditory brain stem responses (ABR). The system contained (1) a response recognition unit which recognized the presence or absence of an ABR response and (2) a threshold tracking unit which adjusted stimulus intensity and determined the ABR threshold. Two methods, one nontemplate (variance ratio) and one template (cross-correlation), were evaluated for response recognition while three threshold tracking methods were explored: clinical, Békésy, and PEST (parameter estimation by sequential testing). Both response recognition and threshold tracking units were evaluated by computer simulations for on-line operation using a standard set of experimentally recorded ABRs. The results indicated that while all the response recognition methods were reasonably accurate, their on-line use resulted in significant differences in test efficiency due to differences in tracking methods.

Acoustics↗
PubMed1990

Classification of audiograms by sequential testing using a dynamic Bayesian procedure.

A new method for estimating audiograms using behavioral responses is presented. The method is based upon a modification of the Bayesian probability formula in which an outcome is predicted from a static set of events. In the new method, classification of audiograms by sequential testing (CAST), the probabilities of occurrence of audiogram patterns are dynamically updated according to the outcome of each test trial. Computer simulation using an infant response model suggests that the procedure is efficient, sensitive, and specific.

Algorithms↗
PubMed1989

Multisensory speech perception by profoundly hearing-impaired children.

Four children in Study 1 (ages 5-7 years) and 4 children in Study 2 (ages 8-11 years) received unimodal (tactual) word recognition training with tactual speech perception aids. Two of the subjects in Study 1 were trained with a 2-channel device and 2 with a 16-channel aid. All of the subjects in Study 2 used a 16-channel aid. Following training, subjects were tested on a list containing equal numbers of trained words and of tactually new words in three conditions: (a) aided hearing alone (H), (b) tactual aid alone (TA), and (c) combined (TA + H). Results indicate that subjects performed significantly better in the combined condition on both trained and tactually new words, providing evidence for significant sensory integration following unimodal training.

Child↗
PubMed1989

Multisensory narrative tracking by a profoundly deaf subject using an electrocutaneous vocoder and a vibrotactile aid.

A congenitally, profoundly deaf adult who had received 41 hours of tactual word recognition training in a previous study was assessed in tracking of connected discourse. This assessment was conducted in three phases. In the first phase, the subject used the Tacticon 1600 electrocutaneous vocoder to track a narrative in three conditions: (a) lipreading and aided hearing (L + H), (b) lipreading and tactual vocoder (L + TV), and (c) lipreading, tactual vocoder, and aided hearing (L + TV + H). Subject performance was significantly better in the L + TV + H condition than in the L + H condition, suggesting that the subject benefitted from the additional information provided by the tactual vocoder. In the second phase, the Tactaid II vibrotactile aid was used in three conditions: (a) lipreading alone, (b) lipreading and tactual aid (L + TA), and (c) lipreading, tactual aid, and aided hearing (L + TA + H). The subject was able to combine cues from the Tactaid II with those from lipreading and aided hearing. In the third phase, both tactual devices were used in six conditions: (a) lipreading alone (L), (b) lipreading and aided hearing (L + H), (c) lipreading and Tactaid II (L + TA), (d) lipreading and Tacticon 1600 (L + TV), (e) lipreading, Tactaid II, and aided hearing (L + TA + H), and (f) lipreading, Tacticon 1600, and aided hearing (L + TV + H). In this phase, only the Tactaid II significantly improved tracking performance over lipreading and aided hearing. Overall, improvement in tracking performance occurred within and across phases of this study.

Adult↗
PubMed1989

The effects of vocoder filter configuration on tactual perception of speech.

Perception of synthetic speech continua through the sense of touch and audition was compared utilizing a 32-channel spectrally-oriented electrocutaneous vocoder display and standard auditory psychophysical procedures. Perception of a consonantal and a vocalic continuum was evaluated utilizing three vocoder filter configurations: logarithmic, linear, and average (geometric mean of logarithmic and linear). Results indicated a close correspondence between tactual and auditory discrimination and identification for the vowel (/a/-/e/) and the consonant (/sta/-/sa/) continuum regardless of the filter characteristics.

Deafness↗
PubMed1988

Similarities between tactual and auditory speech perception.

Perception of synthetic speech continua through the sense of touch and audition was compared utilizing a 32-channel spectrally oriented electrocutaneous display and standard auditory psychophysical procedures. Results indicated a close correspondence between tactual and auditory discrimination and identification for a vowel (/a/-/e/) and a consonant (/sta/-/sa/) continuum. These results suggest that at least some aspects of speech perception are amodal.

Humans↗
PubMed1988

Speech perception by congenitally deaf subjects using an electrocutaneous vocoder.

Two congenitally profoundly deaf adults were trained to perceive words through the Tacticon 1600 electrocutaneous vocoder, an artificial hearing prosthesis. The subjects learned to identify 50 words during 47 hours (Subject One) and 41 hours (Subject Two) of training, with a 41.6 percent rate of success across all sessions. Both subjects showed consistent error patterns during the training phase. Analysis of these error patterns suggested that they were employing word identification strategies based on some general aspects of tactual patterns. Specific characteristics of the tactual patterns that they appeared to be using included: syllable number, tactual locus of word ending, direction of pattern movement, and position of bursts (/t/, /k/, /d/, for example). Following training, the subjects were tested for their abilities to integrate tactual and aided-auditory cues in word identification. Three conditions of aided-audition alone (A), tactual vocoder alone (TV), and aided-audition with tactual vocoder (TV + A) were used. The stimulus-word list for this phase consisted of the 50 words acquired in tactual vocoder training, and 50 "tactually-new" words, i.e., words that had not been presented to them in tactual vocoder training sessions. They correctly identified 93 percent (Subject One) and 56 percent (Subject Two) more trials in the TV + A condition than in the A condition. Tactually-new vocabulary was correctly identified 78 percent (Subject One) and 50 percent (Subject Two) more often when sensory modalities were combined, than when only aided-audition was used. Subjects identified tactually-new vocabulary better than chance in the TV condition.

Adult↗
PubMed1988

The role of audition in infant babbling.

The traditional belief that audition plays only a minor role in infant vocal development depends upon evidence that deaf infants produce the same kinds of babbling sounds as hearing infants. Evidence in support of this position has been very limited. A more extensive comparison of vocal development in deaf and hearing infants indicates that the traditional belief is in error. Well-formed syllable production is established in the first 10 months of life by hearing infants but not by deaf infants, indicating that audition plays an important role in vocal development. The difference between babbling in the deaf and hearing is apparent if infant vocal sounds are observed from a metaphonological perspective, a view that takes account of the articulatory/acoustic patterns of speech sounds in all mature spoken languages.

Acoustics↗
PubMed1988

Assessment techniques to evaluate tactual aids for hearing-impaired subjects.

In order to optimize the use of tactual aids for the deaf, it is important to have a battery of assessments to determine the potential contribution of the aids to acoustic perception and speech identification. We have designed such a battery to be used with young hearing-impaired children. The tasks were developed so that they could be implemented with standard audiometric equipment and applied to subjects of varying age and to different types of tactual aids. Illustrative results from four profoundly hearing-impaired children showed that tactual vocoders allowed detection of high frequencies that were not available to the subjects through aided audition. In most cases with these subjects, performance on simple detection and discrimination tasks showed facilitative effects with tactual vocoders. Facilitative effects were further evidenced in more complex phonemic identification tasks for all subjects. The tasks can be used to determine possible benefits of tactual aids for individual hearing-impaired children.

Auditory Perception↗
PubMed1985

Prespeech vocalizations of a deaf infant: a comparison with normal metaphonological development.

A comparative study of the speech-like vocalizations of a deaf infant and a group of 11 hearing infants was conducted in order to examine the role of auditory experience in the development of the phonological and metaphonological capacity. Results indicated that from 8 to 13 months of age, the deaf subject differed strikingly from hearing infants of comparable age. She produced no repetitive canonical babbling, whereas all the hearing infants produced many canonical syllables. The topography of the deaf infant's vocalizations resembled that of 4-6-month-old (i.e., Expansion stage) hearing infants. Detailed comparisons of the proportion of production of various metaphonologically defined categories by the deaf infant and Expansion stage hearing infants demonstrated many similarities in vocalization, although possible differences were noted. It is concluded that hearing impairment notably affects vocalization development by the end of the first year of life, if not earlier. Spectrographic displays illustrate the categories of infant sounds produced by the deaf and hearing infants.

Child Language↗
PubMed1985

The effect of frequency change on discrimination of pulse bursts in an electrocutaneous tactual vocoder.

Tactual vocoders (artificial hearing systems) transduce the acoustic energy of speech into patterns of stimulation that are presented to the skin. In an electrocutaneous tactual vocoder, energy within an acoustic-frequency band is generally represented at a particular skin locus by the rate or frequency of brief electrical pulse bursts. At present little is known about tactual sensitivity for changes in the frequency of brief, bipolar electrical pulses used in several current electrocutaneous vocoder designs. Accordingly, discrimination of frequency change of electrocutaneous bipolar signals was evaluated for standard frequencies of 48, 100, 148, 200, and 248 Hz at signal durations of 50, 100, and 250 ms. Bipolar pulses (height = 10 mA, width = 13 microseconds) were presented on a single electrode placed slightly above and 8 cm to either the left or right of the navel. In a same-different task, three practiced subjects judged pairs of stimuli separated by an interstimulus interval (ISI) of 300 ms. For standard frequencies of 48 and 100 Hz, psychometric functions were similar for all subjects and all signal durations. For these frequencies, delta f/f was constant at approximately 0.3. By contrast, for standard stimuli greater than 100 Hz, the Weber fraction was found to increase dramatically as a function of both standard frequency and signal duration. In a second, similar experiment the Weber fraction for a 248-Hz standard increased as ISI was decreased below 300 ms. By contrast, ISI had little effect on sensitivity for standard stimuli of 48 and 100 Hz. Overall, these results suggest guidelines for possible intensity coding schemes for future electrocutaneous vocoder designs.

Adult↗
PubMed1985

Infants' discrimination of final syllable fundamental frequency in multisyllabic stimuli.

Two groups of nine, 5- to 11-month-old infants were tested for discrimination of a change in peak fundamental frequency (F0) within the final syllable of multisyllabic speechlike stimuli. A visually reinforced headturn discrimination procedure was used to determine sensitivity to increments in peak F0 in synthetic speech in both bisyllabic (CVCVC) and trisyllabic (CVCVCVC) contexts. Discrimination performance was above chance expectation for increments of 10, 20, and 30 Hz relative to a 150-Hz standard. There were no differences in performance attributable to syllable-number context. In a second experiment reassessing two-syllable stimuli, performance was above chance for increments of 5, 10, and 30 Hz relative to the same 150-Hz standard. Both experiments indicated a relatively flat function relating discrimination score and F0 increment. Overall, infant and adult absolute thresholds for a change in F0 appear similar. Effects of threshold, increment, and syllable number are contrasted with earlier results for infant discrimination of both peak-intensity changes and vowel duration increments in the same multisyllabic stimuli.

Cues↗
PubMed1984

Tactual perception of speech-like stimuli with an electrocutaneous vocoder.

A deficiency in current tactual vocoder designs is the relatively poor transmission of rapid spectral changes (formant transitions). To understand better the application of electrocutaneous tactual stimulation as a basis for an artificial hearing system, the tactual discrimination of rapidly changing patterns was studied. Stimuli were presented on a belt containing 32 electrodes that was worn in a linear array 5 cm above the navel. Bipolar pulse trains (height 10 mA; width 13 microseconds) of specified frequencies (200, 400, or 1,000 Hz) were presented sequentially to adjacent electrodes to simulate a tactual vocoder equivalent of simple frequency transitions. Discrimination of the direction of stimulation movement (i.e., stimulation on the belt to either a subject's left or right) was assessed with one experienced subject as a function of both electrode number (four or eight electrodes) and stimulation frequency. Identification of the direction of stimulation movement was influenced both by the number of stimulus channels and by the frequency of electrocutaneous stimulation. These preliminary results indicate that the discrimination of formant trajectory transmitted in an electrocutaneous vocoder scheme is within the temporal limits typically imposed by natural speech.

Adult↗