The automatic tone decay test as part of dynamic measurement of threshold.

Only dynamic recording of the tone threshold can give information on pathologic adaptation, auditory fatigue, and aggravation. We have therefore automated the tone decay test. This was achieved by modifying the Grason-Stadler audiometer E 800 and, concurrently, by developing a special device with integrated circuits for this purpose. The print-out is made by a commerical x-y-recorder which is also used for recording the impedance test results. During the automatic tone decay test the patient himself increases the intensity of the tone only until he can hear the tone again, the intensity of the tone otherwise remaining constant. Thus, we obtain either a flat (adaptation) or a sharply declining (auditory fatigue) curve which correlates with the Békésy continuous tone curve, but may show a distinctive separation. The tone decay test is - in contrast to all other suprathreshold tests - independent of the amount of hearing loss. It can therefore give information on the kind of hearing impairment for normal short duration thresholds as well.