Time-intensity relations in Békésy audiometry.
Threshold and amplitude measurements were made for fixed frequency Bekesy pure tones on subjects with normal hearing, sensorineural hearing impairment, and functional hearing loss. Following conventional Bekesy audiometry (intensity change 4 dB/sec), -20 dB was added to a signal at the threshold of audibility (bottom of the spike). When sensation was lost at the threshold of inaudibility (top of the spike), +20 dB was added. Adding +/- 20 dB in subjects with normal hearing reduced the amplitude of the spike about 4 dB, corresponding to 1 second, for both pulsed and continuous tones. Adding +/- 40 dB produced essentially similar findings. Adding +/- 20 dB in subjects with sensorineural loss with reduced amplitude of continuous tone tracings also reduced the amplitude approximately 4 dB for pulsed tones, but 3 dB, corresponding to 0.75 seconds, for continuous tones. Abnormal rapid adaptation may account for this reduced amplitude of the spikes. A subject with multiple sclerosis producing excessive abnormal adaptation showed spectacular increased amplitude for continuous tone only when -20 dB was added at bottoms and +20 dB at tops of spikes. An explanation based on slow adaptation is offered. Subjects with functional hearing loss may emphasize either time or intensity in their inappropriate responses when +/- 20 dB is added at tops and/or bottoms of spikes.