Using chronic electrodes placed on the round window membrane, changes of action potential (AP) and summating potential (SP) were measured following the application of repeated noise in rabbits. The intensity of the noise ranged between 80 and 100dB (SPL).
The results were as follows;
1) (+) SP/AP was increased following noise exposure.
2) (+) SP/AP increasement was found while hearing was impaired progressively.
3) It was suspected, however, that (+) SP/AP did not increase when temporary threshold shift (TTS) was found.
It is difficult to anticipate permanent hearing disorders by investigation of TTS. (+) SP/AP increasement following noise exposure may be the useful parameter of the permanent hearing disorders.
