Sensitivität für interaurale Laufzeitdifferenzen als Funktion des Alters und der Form akustischer Stimuli

Sound localization is based on two binaural cues: interaural time and level differences (ITDs/ILDs). In normal hearing (NH) adults, ITD sensitivity threshold is ~20 µs. However, sensitivity to binaural cues can be influenced by various factors (hearing experience, developmental state, type of acoustic stimulus). The development of ITD sensitivity across age and its dependency on stimulus parameters are still under research and was investigated in this study.
Eleven NH (<20 dB HL) children (Ø 9.05 years old) and 10 NH adults (Ø 34.03 years old) were tested on sound lateralization using a closed-field gamified setup. A 0.5 s long tone burst at 250 Hz and a rising slope of 4 ms or 100 ms was used as acoustic stimulus. Participants were tested for ITD of +{25, 50, 100, 200, 400, 800} µs. ITD just-noticeable difference (JND) were calculated for the different test conditions using psychometric functions.
Adults demonstrated significantly better ITD JNDs compared to children across all conditions. For children, ITD sensitivity showed a positive correlation with age under all conditions, indicating developmental improvement. Notably, both cohorts exhibited significantly better ITD JNDs when the auditory stimuli were presented with a rising slope of 4 ms (children: Ø 92.07 µs, adults: Ø 55.78 µs) rather than 100 ms (children: Ø 113.89 µs, adults: Ø 73.28 µs).
In conclusion, auditory networks for ITD-based spatial hearing are still maturing in early childhood, resulting in significantly poorer ITD sensitivity compared to mature, adult networks. Regardless of developmental stage, better ITD sensitivity was achieved with auditory stimuli that contained strong onset ITD information (4 ms rising slope), confirming the importance of onset ITD sensitivity for optimal spatial hearing.

Die Studie wurde finanziell unterstützt von der Firma MED-EL GmbH, Innsbruck, Österreich.