Biomedical subjects

Sebastian Hoth

Publications and source records attributed to Sebastian Hoth.

5 recordsLinked to original sources

PubMed2006

Indication for the need of flexible and frequency specific mapping functions in cochlear implant speech processors.

Categorical loudness scaling of electric and acoustic stimuli was performed in cochlear implant (CI) recipients equipped with Nucleus systems in order to achieve a normal loudness perception in the whole dynamic range of acoustic input. For each electrode, the lower and upper limits of electric stimulus were defined by the values corresponding to "very soft" and "too loud". Within this dynamic range, the stimulus strength intervals associated to the verbal categories "soft", "medium", "loud" and "very loud" were determined. The same loudness categories were used for the scaling of acoustic stimuli. From both scaling experiments, the transduction of the CI system can be assessed and the parameters of the individual mapping function yielding a normal loudness growth can be derived. Deviations from optimum mapping can be corrected at least partially by manipulating the parameters of the mapping function. In many cases, however, one mapping function is not sufficient for all channels. The results argue in favour of the development of flexible and channel-specific mapping function parameters in future CI systems.

Cochlear Implants↗

PubMed2006

Auditory status of persons with intellectual disability at the German Special Olympic Games.

Among persons with intellectual disability, the prevalence of hearing impairments is high. During the German Special Olympics Summer Games 2004, a hearing screening was conducted on 755 athletes with intellectual disabilities. Obligatory screening included ear inspection and recording of otoacoustic emissions, and optional screening included tympanometry and brief pure-tone audiometry. 38.0% of the athletes failed the screening. 53.0% needed ear wax removal. 56.1% of the fails indicated sensorineural hearing loss and 13.6% indicated mixed hearing loss. 12.5% of the fails were caused by unremovable ear wax, 1.4% by ear canal affections, and 16.4% by middle ear problems. Left ear fails were more frequent than right ear fails. A peripheral hearing disturbance can thus be expected in every third subject. The high failure rate, a considerable percentage of previously undetected profound hearing loss (1.1%), and the frequent need for ear wax removal, suggest that nearly half of persons with intellectual disabilities need regular otological or audiological consultations.

Acoustic Impedance Tests↗

PubMed2006

Field study to explore possible effects of styrene on auditory function in exposed workers.

OBJECTIVES: We conducted this study to examine, whether occupational styrene exposures are associated with reduced hearing ability. METHODS: The auditory function was investigated by pure tone audiometry and registration of transitory evoked otoacoustic emissions (TEOAE) in 32 workers of a fibre-reinforced plastic boat building factory. Sixteen subjects were laminators (mean age: 41 yr (SD: 8)) and therefore regularly exposed to styrene with mean duration of exposure to styrene of 7.5 yr (SD 5.0). The tests were applied to a reference group of 16 workers (mean age: 39 yr (SD: 8)) who were not directly exposed to styrene but had a similar noise exposure. RESULTS: A few and isolated correlations between the parameters of hearing acuity and exposure indices, such as current internal styrene exposures (sum of MA and PGA) and duration of styrene exposure, were statistically significant, but no consistent association was found. CONCLUSION: The results of this study do not support the assumption of an ototoxic effect of chronic styrene exposure in workers.

Adult↗

PubMed2004

On a possible prognostic value of otoacoustic emissions: a study on patients with sudden hearing loss.

Otoacoustic emissions (OAE) and pure tone audiogram (PTA) were examined in 26 ears of 25 patients suffering from sudden hearing loss from the 1st day to up to 505 days following the drop of hearing to test the hypothesis whether the OAEs are capable of delivering predictive information about the recovery process. The patients were selected from 50 candidates according to the following criteria: one or both ears exhibited a systematic and significant recovery of pure tone threshold in at least one frequency, OAEs were detectable and PTA available, a conductive hearing loss was excluded, and the auditory brainstem responses (ABR) yielded no signs of retrocochlear disorders. Transitory evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) were measured under constant stimulus and recording conditions in three to nine sessions. The relation between OAE level and actual pure tone threshold was subject to a regression analysis. The correlation between both parameters is small but significant. Even smaller correlations are observed if the OAE level is related to former hearing loss, whereas the correlation improves if the OAE level is compared to the pure tone threshold measured in a later session. The slopes of individual trajectories that connect the successive results of one ear in a plane defined by hearing loss and OAE level show a remarkable accumulation around zero, i.e., in many cases the OAEs remain unchanged even if the hearing loss decreases. The comparison of the OAE levels measured at an early stage with later audiograms shows that there are only a small number of cases with small initial emissions and good final threshold or large initial emissions and bad final threshold. This means that small initial OAEs end up with a remaining final hearing deficit, whereas a high OAE level immediately after drop of threshold correlates with good outcome. The reliability of an individual prediction based on the OAE level combined with the threshold after sudden hearing loss and the consequences for the physiologic mechanisms underlying the sudden hearing loss remain to be proved in further investigations.

Adult↗

PubMedDate not supplied

The interplay between glottis and vocal tract during the male passaggio.

The transition between 'chest' and 'head' register is essential for male opera singers in order to reach the higher pitches. The 'passaggio', which is a scale passage where this transition takes place, but also a maneuver of register equalization, is typically difficult to learn. Studies on parameters for a definition of this transition are restricted to a small number of singers so far. Audio, electroglottographic, and equivalent subglottic pressure signals of 11 male opera singers were recorded while singing scales on open back vowels and passing the register transition. A spectrum analysis of the audio signal revealed that the second harmonic (H2) dominates in 'chest', resonated by the first formant (F1), together with the fourth harmonic (H4), supported by the second formant (F2). During the passaggio, H2 level decreases because it loses the resonance of F1, while the third harmonic (H3) gains the resonance of F2. At this point the H4 level drops because that harmonic is no longer supported by F2. The transition from 'chest' to 'head' register is marked by characteristic changes in the amplitude patterns of the partials H2, H3, and H4, and the frequency progressions of the first two formants, defining an objective distinction between the two registers.

Adult↗