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Biomedical subjects

T Spillmann

Publications and source records attributed to T Spillmann.

12 recordsLinked to original sources
PubMed1992

Digital speech processing for cochlear implants.

A rather general basic working hypothesis for cochlear implant research might be formulated as follows. Signal processing for cochlear implants should carefully select a subset of the total information contained in the sound signal and transform these elements into those physical stimulation parameters which can generate distinctive perceptions for the listener. Several new digital processing strategies have thus been implemented on a laboratory cochlear implant speech processor for the Nucleus 22-electrode system. One of the approaches (PES, pitch excited sampler) is based on the maximum peak channel vocoder concept whereby the spectral energy of a number of frequency bands is transformed into appropriate electrical stimulation parameters for up to 22 electrodes using a voice pitch synchronous pulse rate at any electrode. Another approach (CIS, continuous interleaved sampler) uses a maximally high pitch-independent stimulation pulse rate on a selected number of electrodes. As only one electrode can be stimulated at any instance of time, the rate of stimulation is limited by the required stimulus pulse widths (as determined individually for each subject) and some additional constraints and parameters which have to be optimized and fine tuned by psychophysical measurements. Evaluation experiments with 5 cochlear implant users resulted in significantly improved performance in consonant identification tests with the new processing strategies as compared with the subjects own wearable speech processors whereas improvements in vowel identification tasks were rarely observed. The pitch-synchronous coding (PES) resulted in worse performance compared to the coding without explicit pitch extraction (CIS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Comparison of hearing aids and cochlear implants in profoundly and totally deaf persons.

Cochlear implants are increasingly used in the rehabilitation of the profoundly and totally deaf. Usually, insufficient gain of speech discrimination with a powerful conventional hearing aid is considered as a prerequisite for a cochlear prosthesis. With recent improvements of electronic systems, the criterion for this decision may change. To keep pace with the technical progress, a battery of speech sound tests suited for minimal auditory capabilities (MAC-battery) was developed and applied to groups of patients fitted with conventional instruments and with two different types of cochlear implants. Based on the comparison of the MAC-battery results of hearing aid groups, with the average performance of an implanted group, most conventionally fitted regular users of hearing aids should not be considered as candidates for cochlear implantation. The MAC-battery, although not a strictly standardized procedure, is a useful instrument for patient counselling and for the selection of implant candidates.

Adolescent↗
PubMed1989

Hereditary distal muscular atrophy with vocal cord paralysis and sensorineural hearing loss: a dominant form of spinal muscular atrophy?

In 1980 Young and Harper described a family with an unusual form of distal spinal muscular atrophy associated with vocal cord paralysis. We report a family with three similarly affected subjects. Progressive sensorineural hearing loss was an additional feature in our patients. Electrophysiological and histological investigations did not exclude an involvement of sensory neurones. Whether the classification of this dominant disorder with the spinal muscular atrophies is justified will depend on additional studies in further families.

Acoustic Impedance Tests↗
PubMed1989

Comparison of single-channel extracochlear and multichannel intracochlear electrodes in the same patient.

A postlingually deaf patient who had been using a single-channel extracochlear implant for 5 years was reimplanted in the same ear with a 22-channel intracochlear device after electrical failure of the internal receiver. In the subsequent follow-up period, auditory performance was investigated in a series of tests with nonspeech and speech material. Two weeks after processor fitting most test scores were equal or better with the new implant. Three months later, with only minimal training, the patient's performance in sentence, numerals and vowel tests was markedly improved. Analysis of vowel confusion matrices indicated a high percentage of F2 information perceived (53% compared with 5% with the single-channel device) and somewhat less F1 information (35% compared with 4% using the single-channel device). Further improvements of speech discrimination (especially consonant recognition) are conceivable if the fine temporal resolution provided by some single-channel devices can be combined with the spectral resolution of multichannel systems.

Cochlear Implants↗
PubMed1988

[Perception of acoustic speech features with single channel cochlear implants and hearing aids. A comparative analysis].

A newly developed battery of 12 multiple-choice tests for the German language (graded according to difficulty) comprising identification of sentences, words and syllables was applied to 8 patients with single-channel cochlear implants and to 35 deaf hearing-aid users. Phoneme confusion matrices were analysed using sequential information transmission analysis (SINFA) and multi-dimensional scaling (SINDSCAL). Acoustic parameters of the digitally stored test items were compared with the outcome of SINFA and SINDSCAL. It was found that cochlear implant and hearing-aid users relied on the same perceptual dimensions which were correlated to acoustic signal properties of the speech sounds. Best perceived acoustic features were time and amplitude structure of the speech sound (envelope). Fundamental and first formant frequency are evaluated both by implant and hearing-aid users. The use of higher frequency spectral information depends on the amount of residual hearing.

Auditory Threshold↗
PubMed1986

Stapedius reflex in multiple sclerosis.

The stapedius reflex (StR) was studied in humans by impedance audiometry. Ipsilateral and contralateral reflexes, obtained from 48 multiple sclerosis (MS) patients and 26 controls, were analysed. MS patients showed smaller reflex amplitudes, longer onset latencies and higher contralateral reflex thresholds. Using onset latencies, 33% of all MS patients had at least two abnormal ipsi- and/or contralateral StRs. If the diagnosis was MS of the definite type, this figure was 39%. The StR is therefore a useful tool for detecting a subclinical lesion in the brainstem and can contribute to the early diagnosis of MS.

Acoustic Impedance Tests↗
PubMed1979

[The prognostic value in tympanoplasty surgery of eustachian tube function tests (author's transl)].

A study was undertaken to test the validity of preoperative Eustachian tube ventilation measurements in 107 patients with conductive deafness and chronic middle ear disease. By standard static aspiration and deflation tests and with the Valsalva probe correlations were found in some patients between tubal function and the extent of middle ear damage as shown by the air-bone gap on audiometry and the findings at operation. However no prognostic information was evident with these measures since no relationship existed between tubal function and operative success as judged by closure of the air-bone gap or by healing of the tympanic membrane defect.

Ear Diseases↗
PubMed1978

[Electrical stimulation of hearing in humans: a survey of the actual state of development of an implantable prosthesis for sensorineural deafness (author's transl)].

Recent clinical results show that electrical excitation of hearing sensations with implanted electrodes in the inner ear can be successful in suitable deaf persons. A critical literature review shows that some results have been described too vaguely and that there still exist numerous methodical and technical deficiencies. Even with multichannel stimulation, true tonotopical hearing could not be achieved. Periodicity hearing alone is not sufficient for the discrimination of one-syllable words. However, most deaf persons fitted with surgically implanted electrodes judged the new hearing sensations as being agreeable and quite useful. There seem to be no long term harmful effects of these implants upon the state of the acoustic nerve. However there are still a series of basic questions in auditory physiology pending which can only be solved through intensive collaboration of the clinical disciplines involved.

Animals↗