H Meister1, H Klüser, H v Wedel, M Walger. 1. Klinik und Poliklinik für Hals-, Nasen-, Ohrenheilkunde, Kopf- und Halschirurgie, Universität zu Köln. hartmut.meister@uni-koeln.de
Abstract
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.
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.