[Auditory steady-state response to sinusoidally amplitude-modulated tones. First report: investigation of response in the awake state].
Basic characteristics of the steady state response (SSR) evoked by sinusoidally amplitude-modulated tone (SAM tone) were studied in 26 awake adults with normal hearing. This study was designed to determine how this response to SAM tone effects the objective hearing test. The responses to 2048 stimuli were averaged with an analysis time set at 102.4 ms and were digitally filtered with a pass band of 30-100 Hz. The results obtained are as follows. With a carrier frequency of 500 Hz, the response amplitude was maximal at a modulation frequency of 30 or 40 Hz and decreased rapidly at 50 Hz. The response amplitude increased linearly with an increase in the modulation depth shown on a logarithmic scale. The mean latency of this response, as determined by the Diamond method, was 37.5 ms. The response amplitude increased with an increase in the stimulus intensity, but the rate of increase was highest at a carrier frequency of 500 Hz and tended to become smaller with increasing carrier frequency. At carrier frequencies of 500 and 1000 Hz, response detectability reached 100% with a stimulus intensity of 30 dBnHL, while at the higher frequencies, 100% detectability was attained at 40-50 dBnHL. The mean response thresholds were 15.0 dBnHL, 13.1 dBnHL, 25.3 dBnHL and 30.0 dBnHL at 500, 1000, 2000 and 4000 Hz, respectively.
Department of Otolaryngology, Shinshu University School of Medicine, Matsumoto.
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Umegaki
D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D001300:Audiometry, Evoked Response; D005260:Female; D006320:Hearing Tests; D006801:Humans; D008297:Male; D014851:Wakefulness / Q000502:physiology*