A simple mathematical model for TTS

Published data on Temporary Threshold Shift (TTS) suggest that in many cases the rms pressure at threshold during and after exposure to noise varies in a simple exponential manner, and that the ultimate shift of pressure threshold for exposure to steady noise is dependent on the mean square pressure of that noise. This response could occur if some part of the hearing mechanism were heated by exposure to noise and were at the same time subject to Newtonian cooling, and if the change in the pressure threshold were proportional to the change of temperature. This model can explain the shapes of many growth and recovery curves given in dB, why time constants found for recovery from TTS appear greater than those for growth and why threshold shifts on ears with elevated thresholds appear smaller than those for ears with low thresholds. Because of individual variation, averaged dB results mask the nature of the processes involved. Hence, for a better understanding of TTS, individual ears should be studied separately, and, if possible, measurements should be made in rms Pa instead of dB.