The modification of Nl -N2 Audiograms before and after loudtone exposure onto the tympanic membrane of guinea pigs was examined. The exposure was a loud continuous tone of 106 dB SPL intensity at 10 KHz for 10 minutes. The comparison between Wl-H2 Audiograms pre and post loudtone exposure indicates that the exposed cochlea permanently lost its normal hearing function. The largest threshold shifts wore found between 12-13.2KHz. The functional change of the cochlea after the loudtone exposure depends on the state of the cochlea before the trauma. More sensitive cochlea is more critically damaged in its function after the trauma than less sensitive cochlea.