Biomedical subjects
R S Tyler
Publications and source records attributed to R S Tyler.
Consonant recognition and quality judgments of noise-reduction hearing aids.
We evaluated seven different hearing aids worn by 13 experienced hearing-aid users. Two of the aids, the Audiotone A-54 and the Telex 363C, included amplitude compression. The others, two versions of a Maico aid (SP147), a Richards (ASE-B), a Rion (HB-69AS), and a Siemens (283ASP), have circuits designed to attenuate specific frequency regions in the presence of noise. Consonant recognition and quality judgments were measured with the processing circuit on and off in the presence of speech-babble noise and low-frequency noise. The results suggested that only a few subjects benefited from the processing circuits. Quality judgments and consonant recognition scores were not always in agreement.
What should be implemented in future cochlear implants?
Cochlear-implant performance can be improved by focusing on: 1) psychophysical studies to determine hearing limitations; 2) speech perception to suggest the most effective speech-processing strategies; 3) aural rehabilitation to effectively train patients to use the new electrical stimuli. Basic psychophysical studies have shown only weak correlations with speech perception. Perhaps more speech-like stimuli should be explored in psychophysical tasks. Studies on vowel and consonant recognition suggest enhancing all speech features, but particularly frication and place of articulation should help most patients. Probably the feature that would be the most beneficial to enhance is place of articulation, which is poorly coded even in the best patients. Empirical studies are needed to determine the ways in which these cues can be enhanced. Certain types of auditory training are likely to be beneficial, particularly when the signal is new, incomplete or distorted. However, much more research in aural rehabilitation is needed.
Advantages and disadvantages reported by some of the better cochlear-implant patients.
An open-ended questionnaire was administered to 53 of some of the better patients using five different kinds of cochlear implants. The subjects listed the advantages and disadvantages of their cochlear implant. Patients were asked about the time from implantation until maximum benefit and effect of the cochlear implant on tinnitus. Advantages were reported in (1) speech perception when speechreading can be used (85%); (2) environmental sound perception (75%); (3) psychologic effects (70%); (4) speech perception when speechreading cannot be used (64%); (5) lifestyle and social effects (42%); and (6) speech production (32%). Disadvantages were reported in (1) use of equipment (79%); (2) environmental-sound perception (47%); (3) speech perception when speechreading may be used (17%); (4) psychologic effects (11%); (5) speech perception when speechreading is not used (9%); (6) lifestyle and social effects (3.8%); and (7) speech production (1.9%). Ninety-one percent of the subjects indicated that they achieved maximum benefit in the first 7 months of cochlear-implant use. Eighty-one percent of the subjects with tinnitus indicated that the cochlear implant had a positive effect on their tinnitus. In 17 percent of the cases the cochlear implant had no effect on their tinnitus and in 2 percent of the cases it made the tinnitus worse.
Alternating current at the eardrum for tinnitus reduction.
The effectiveness of alternating current (AC) stimulus on tinnitus was investigated in 10 patients who reported constant tinnitus in at least one ear. Patients were first screened to determine their responsiveness to electrical stimulation in relation to tinnitus reduction. The responsive patients were then stimulated for a treatment period of at least 10 min, during which time the tinnitus was measured. The AC stimuli (62 Hz to 8000 Hz) were applied to the eardrum of the patients via a specially constructed electrode. Psychophysical measurements (pitch matching, loudness matching, minimum masking level, and loudness and annoyance scaling) of the patient's tinnitus were made before and after electrical stimulation. Minimal masking level was determined and tinnitus scaling was performed during the treatment period. Electrical stimulation was effective in tinnitus reduction in 5 of the 10 patients. These 5 patients reported that the loudness and the annoyance of their tinnitus decreased during the treatment period. These observations were consistent with psychophysical measures of contralateral broadband noise masking. Poststimulation reduction in tinnitus varied in duration among individuals from 40 s to about 4 hr.
Temporal-gap detection by cochlear prosthesis users.
Minimum-detectable gaps for sinusoidal stimuli were measured for three users of a multi electrode cochlear prosthesis as functions of stimulus level, frequency, and electrode place within the cochlea. Stimulus level was scaled by sensation level and by growth-of-loudness functions generated for each condition by direct magnitude estimation. Minimum-detectable gaps decreased with increase in either sensation level or loudness, up to a plateau. When compared at equal sensation levels, the minimum-detectable gaps decreased with frequency increases. The frequency effect on minimum-detectable gaps is reduced if the data are considered at equal loudness. Comparison across place of stimulation within the cochlea showed minimum-detectable gaps to be shorter for more basal electrode placement at low stimulus levels. No differences in minimum-detectable gap as a function of place were found at higher stimulus levels.
Performance of some of the better cochlear-implant patients.
The main purpose of this study was to provide an independent corroboration of open-set word recognition in some of the better cochlear-implant patients. These included the Chorimac, Nucleus (one group from the U.S.A. and one group from Hannover, Germany), Symbion, Duren/Cologne and 3M/Vienna implants. Three experiments are reported: (1) word recognition in word lists and in sentences; (2) environmental sound perception, and (3) gap detection. On word recognition, the scores of 6 Chorimac patients averaged 2.5% words and 0.7% words in sentences correct in the French tests. In the German tests, the scores averaged 17% words and 10% words in sentences for 10 Duren/Cologne patients, 15% words and 16% words in sentences for 9 3M/Vienna patients, and 10% words and 16% words in sentences (3% to 26%) for 10 Nucleus/Hannover patients. In the English tests, the scores averaged 11% words and 29.6% words in sentences for 10 Nucleus-U.S.A. patients, and 13.7% words and 35.7% words in sentences for the 9 Symbion patients. The ability to recognize recorded environmental sounds was measured with a closed set of 18 sounds. Performance averaged 23% correct for Chorimac patients, 41% correct for 3M/Vienna patients, 44% correct for Nucleus/Hannover patients, 21% correct for Duren/Cologne patients, 58% correct for Nucleus/U.S.A. patients, and 83% correct for Symbion patients. A multidimensional scaling analysis suggested that patients were, in part, utilizing information about the envelope and about the periodic/aperiodic nature of some of the sounds. Gap detection thresholds with a one-octave wide noise centered at 500 Hz varied widely among patients. Typically, patients with gap thresholds less than 40 ms showed a wide range of performance on speech perception tasks, whereas patients with gap-detection thresholds greater than 40 ms showed poor word recognition skills.
The effects of "noise suppression" hearing aids on consonant recognition in speech-babble and low-frequency noise.
We evaluated the performance of experienced hearing-aid users wearing seven different commercially available "noise-suppression" hearing aids. Two hearing aids, the Audiotone A-54 and the Telex 363C, used amplitude compression. The others, two versions of a Maico hearing aid SP147, a Richards ASE-B, a Rion HB-69AS, and a Siemens 283ASP, are designed to attenuate specific frequency regions in the presence of noise. Sixteen subjects listened to 13 consonants in the form (i)-consonant-(i) with six replications per consonant (78 items). Performance was measured with the compression or noise-suppression circuit on and off in the presence of speech-babble noise and in continuous low-frequency noise. Measurements were also obtained with the suppression circuit "off" but without any background noise. The results suggested that only a few subjects benefitted from the noise-suppression circuits, and in several cases performance in noise was poorer with the noise suppression circuit than without it. An information-transfer analysis of the errors indicated that enhanced or decreased performance was generally a result of changes across all phonetic features, not specific ones.
Auditory consonant and word recognition skills of cochlear implant users.
Auditory consonant recognition and sentence recognition tests were administered to two subjects wearing the 3M/House cochlear implant, three subjects wearing the 3M/Vienna implant, seven subjects wearing the Cochlear Corporation (Nucleus) implant and 10 subjects wearing the Symbion implant. For the 14-item consonant test, the Symbion subjects scored an average of 41% consonants correct (17-58%), the Cochlear Corporation subjects scored an average of 34% (25-48%), the 3M/Vienna subjects scored 19% (15-26%), and the 3M/House subjects scored 11% (7-14%). An information transfer analysis performed on the consonant data suggested that subjects perceive the envelope feature relatively well and the place feature relatively poorly. All of the 3M/House and 3M/Vienna subjects scored 0% words correct for the sentence test. The Symbion and Cochlear Corporation subjects scored an average of 35% (0-92%) and 32% (9-45%) words correct, respectively. To better understand the variability in word recognition skills, the scores from the sentence test were correlated with the results of the information transfer analysis. The voicing and duration features did not correlate with the sentence scores very well. Place and frication features were shown to be most predictive of auditory word recognition. This finding suggests that subjects who utilize middle and high-frequency speech information are more likely to score better on open-set word recognition tests than subjects who do not.
The recognition of vowels differing by a single formant by cochlear-implant subjects.
The ability to recognize synthetic, two-formant vowels with equal duration and similar loudness was measured in five subjects with the Cochlear and five subjects with the Symbion cochlear implants. In one set of test stimuli, vowel pairs differed only in the first-formant frequency (F1). In another set, vowel pairs differed only in the second-formant frequency (F2). When F1 differed, four of five Cochlear subjects and four of five Symbion subjects recognized the vowels significantly above chance. When F2 differed, two of five Cochlear subjects and three of five Symbion subjects scored above chance. These results suggest that implanted subjects can utilize both "place" information across different electrodes and "rate" information on a single electrode to derive information about the spectral content of the stimulus.
Synthetic two-formant vowel perception by some of the better cochlear-implant patients.
Synthetic two-formant vowel recognition was tested in some of the better cochlear-implant users to determine their ability to resolve sounds that differ essentially in their frequency content. The vowels /i, epsilon, alpha, u/ were synthesized with equal duration and similar sound pressure level. The formant values were chosen to approximate the values of these vowels in French, German and American English. Performance ranged from 29 to 71% for the 6 patients with the Chorimac implant, from 25 to 67% for the 9 patients with the 3M/Vienna implant, from 63 to 92% for the 10 patients with the Nucleus implant from Hannover, from 17 to 79% for the 10 patients with the Duren/Cologne implant, from 54 to 100% for the 9 patients with the Symbion implant, and from 79 to 100% for the 10 Nucleus patients from the USA. Patients with each of these devices can utilize some spectral information when recognizing steady-state vowels.
Word recognition performance with single-channel and multichannel cochlear implants.
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Open-set word recognition with the 3M/Vienna single-channel cochlear implant.
The author visited Innsbruck (Austria) to evaluate the performance of nine of the better patients implanted in Europe with the 3M/Vienna single-channel cochlear implant. Word- and sentence-level speech recognition tests recorded in German by two speakers from Austria were presented. Performance varied from 15% to 86% correct word recognition on the sentence material, 11% to 57% correct word recognition with word lists, and 21% and 66% correct phoneme recognition on the word tests. These results confirm earlier studies indicating that high levels of open-set word recognition without visual cues can be obtained with the 3M/Vienna single-channel cochlear implant.
A critique of continuous discourse tracking as a test procedure.
Continuous discourse tracking is a versatile aural rehabilitation procedure. However, it is frequently used as a test instrument to evaluate the effectiveness of communication aids and aural rehabilitation strategies or to compare communication performance using auditory and/or visual stimuli. In this report, shortcomings of this practice are reviewed. Continuous discourse tracking has numerous uncontrolled variables related to the sender (i.e., the tester), the receiver (i.e., the subject), the text materials, and repeated presentations. We suggest that tracking is inappropriate for across-subject designs. For within-subject test designs, stringent guidelines are offered to minimize some of the problems. Test developers should focus their future efforts on devising a test that reflects a natural communication interaction--one that engages the subject in a conversational style of listening.
Use of multichannel cochlear implants in obstructed and obliterated cochleas.
Obstruction that occurs within the scala tympani (after meningitis or otosclerosis) has been considered a contraindication for placement of a multichannel cochlear implant electrode. Two patients who exhibited radiographic evidence of intracochlear narrowing and obliteration were implanted with multichannel electrodes. Implantation involved creation of a channel for the electrode to wrap around the modiolus. The middle ear cavity and the external auditory canal also had to be removed to gain access. The response of one of the patients was similar to that of patients with normal cochlear anatomy who use multichannel devices. These early experiences, along with one case in which a single-channel electrode was placed, is presented.
Open-set word recognition with the Duren/Cologne extracochlear implant.
The author visited Duren, West Germany and evaluated the performance of five patients implanted with the extracochlear Duren/Cologne implant who achieved better word recognition levels. Word and sentence speech reception tests were presented live-voice by a familiar German speaker. Performance ranged from 1% to 80% correct word recognition with sentence material, 0% to 63% correct word recognition with word lists, and 13% to 86% correct recognition for phonemes in words. One patient achieved high-level, open-set word recognition without visual cues, using single-channel, extracochlear stimulation. Preimplant auditory thresholds in her implanted ear were 60, 65, 90, and 105 dB HL at octave frequencies from 125 to 1,000 Hz, respectively. There was no measurable hearing at higher audiometric frequencies.
Evaluation of five different cochlear implant designs: audiologic assessment and predictors of performance.
The audiologic performance of 54 postlingually deafened adults wearing cochlear implants was uniformly evaluated. The participants had 9 months' or more experience with one of five different cochlear prostheses (Los Angeles Single Channel (N = 11), Vienna Single Channel (N = 4), Melbourne Multichannel (N = 18), Utah Multichannel (N = 19), San Francisco Multichannel (N = 2). The multichannel designs enabled participants to recognize more environmental sounds, provided more speech reading enhancement, and enabled most users to understand limited speech in the sound-only condition, compared to the single-channel implant group.
Hazardous sound levels produced by extracorporeal shock wave lithotripsy.
Sound emitted from the Dornier system GmbH lithotriptor was found to be of sufficient intensity to warrant concern about noise-induced sensorineural hearing loss. The patients were exposed to impulses of 112 dB. peak sound pressure level. Operating room personnel were exposed to sounds of less intensity, although the number of impulses they were exposed to was much greater, thereby increasing the risk of hearing loss. Hearing protection is recommended for patients and operating room personnel.