[Conception and realisation of a prosody test battery]. / Konzeption und Realisierung einer Prosodie-Testbatterie.

BACKGROUND: Prosody reflects rhythmic and melodic aspects in speech and is one of the quality measures that shows--apart from pure speech understanding--a rising interest in the assessment of technical hearing aids, especially of cochlear implants. At present, there is no adequate test battery for the German speaking population. The test battery presented in this study aims to fill this gap. METHODS: The test battery consists of four different modules addressing different prosodic cues, namely duration, question vs statement, sentence stress, and speaker gender. One part of the test battery aims at reflecting everyday situations and was realized with six different speakers representing various pitch frequencies and speak rates. Another goal of the tests is to detect very small differences in prosody perception. Therefore, natural utterances were artificially modified by changing the underlying acoustic parameters (e.g. duration, fundamental frequency). Measurements were performed with 12 normal listeners in order to investigate the properties of the tests. RESULTS: As expected, the normal listeners revealed discrimination rates of close to 100% in that part of the test battery using natural utterances. For the part with the modified stimuli, all four modules revealed very steep discrimination functions indicating that the normal listeners were able to use very small changes in the acoustic parameters as cues for prosody perception. Moreover, the slope of the discrimination function revealed very low variability. CONCLUSIONS: Together with preliminary data from cochlear implant recipients who clearly showed different psychometric functions, the test battery seems suitable for a comprehensive evaluation of prosody perception. This facilitates future examinations of speech processing beyond the pure understanding of speech.

[Experiments on prosody perception with cochlear implants]. / Experimente zur Perzeption prosodischer Merkmale mit Kochleaimplantaten.

BACKGROUND AND OBJECTIVE: Prosody has a myriad of linguistic functions and involves specific aspects of speech, such as stress, intonation and pauses. The underlying acoustic quantities (amplitude envelope, pitch frequency, and temporal structure) can be processed and transmitted by cochlear implants (CI) only to a limited extent. At present, no adequate tests are available in the German-speaking world for evaluation of the perception of prosodic elements. Different experiments have been conducted to address several prosodic cues, and the results are to be used as a basis for appropriate tests. METHODS: Various prosodic materials were used for the experiments. Discrimination was measured for minimal pairs differing in frequency and/or duration, accents in words and phrases, questions versus statements and phrasing. Measurements were performed in ten normal-hearing subjects and five with cochlear implants. RESULTS AND CONCLUSIONS: In all test modules, the subjects with normal hearing proved to have high discrimination rates of 96-100%. The test of word stresses was problematic because the results were influenced by different confounders. The other measurements did prove to be basically suitable for use in the subjects with implants. Early results revealed that the subjects with CI had few problems with prosodic cues based on the temporal structure, the outcome being similar to that of the subjects with normal hearing in these tests. In contrast, the performance of subjects with CI in perceiving prosodic cues based on amplitude variations and, especially, on alterations in pitch frequency was worse, even though some of them achieved very good results in these tests too. These preliminary tests can form the basis for development of a German-language prosody test battery with a limited number of subtests addressing different prosodic cues.

[A measurement system for assessing binaural masking level difference (BMLD) in children]. / Messsystem zur Erfassung der "binaural masking level difference" (BMLD) bei Kindern.

BACKGROUND: The binaural masking level difference (BMLD) is defined as the contrast between homophasic and antiphasic signal conditions, and can be regarded as a measure for noise suppression by the auditory system. METHODS: An adaptive two interval forced choice (IFC) measurement method was designed to assess BMLDs in children. The target tone was a 500 Hz sine pip which was masked with narrow band noise. The presentation of homo- and antiphasic signals was staggered in order to take into account artefacts--such as changes in vigilance--in a similar manner for both conditions. RESULTS: Measurement was feasible in 57 out of 85 children (6-14 y.) with suspected auditory processing disorders. Mean BMLD was 7.4(+/-4.5 SD) dB. Five children revealed a BMLD close to 0 dB suggesting that they had no advantage in signal detection for the antiphasic condition. Eleven children were not able to cope with the task of measurement. In another 17 children, the measurements did not converge to a stable threshold. DISCUSSION: The proposed measurement method was feasible with most of the children. With slight modifications of the threshold convergence, this proportion can be further increased. Whether or not the large inter-individual scatter of the results is an expression of the heterogeneous clinical clientele can only be determined when normative data are available.

[Examination of binaural signal processing in normally hearing subjects using electrophysiological and psychoacoustical measurements]. / Elektrophysiologische und psychoakustische Untersuchungen zur binauralen Signalverarbeitung normalhörender Erwachsener.

BACKGROUND AND OBJECTIVE: At present, only a small number of validated, clinically usable methods for the assessment of binaural hearing capabilities exist. A proposed electrophysiological measure is the registration of the brainstem-based binaural difference potentials (BDP). PATIENTS/METHODS: The BDP is calculated as the difference between the binaurally evoked registration and the sum of the two monaural registrations. Detection and stability of the BDP were examined in 24 normally hearing adults within the framework of conventional registration of auditory brainstem responses. Furthermore, the influence of interaural time differences (ITD) on the BDP was determined. In addition, lateralization of the subjects was assessed using a psychoacoustical method. RESULTS: The components of the BDP could be detected in almost all of the subjects. Moreover, they showed sufficient test-retest reliability. The impact of ITD,which causes lateralization of the stimulus,was clearly detectable for the latencies and the amplitudes of the BDP. CONCLUSIONS: Binaural difference potentials, which are easily and reliably detectable reveal a relationship to the outcome of psychoacoustical assessment of lateralization and have the potential to provide a measure for binaural hearing capacity.