Latenzzeitmessungen der akustisch ausgelösten Impedanzänderung
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Latent period of the impedance change on sound stimulus
The latent period of the acoustic Impedance change depending on the frequency and measured always 10 dB above the reflex level was determined in 100 subjects without middle ear diseases. It is more than ten times higher than the one of the first muscle potentials. The datavaried from 150–200 ms concerning the onset of the impedance change and from 320–450 ms as for the maximum. There are no marked differences between persons of different ages nor between normal hearing persons and patients with inner ear hearing loss. The change of impedance depends on the stimulating frequency whereas—according to the literature—the latency of the muscle potential does not. The impedance change is observed 50–120 ms earlier in middle frequencies than in frequencies above 2000 c/s. In the frequency range of human language the stapedial muscle must be stimulated more efficiently than in higher frequencies.