Recovery model of temporary threshold shifts from exposures with the same L_Aeq,T and different frequency components

Temporary Threshold Shifts (TTS) were determined for 9 subjects exposed to three different band-passed signals taken from one channel of a binaural recording of an industrial mill. The three 2-octave bands were: Low (125 to 500 Hz), mid (500 Hz to 2 kHz), and high (2 kHz to 8 kHz). The band-passed signals were adjusted to give the same equivalent A-weighted sound exposure according to ISO-1999 (1990) and were presented to one ear of the subjects in three separate experimental sessions. The results were used in a recovery model based on a least-squares fit of the data to a superposition of exponential functions. The recovery model showed good agreement with the average TTS across subjects and confirms that the high band caused the greatest TTS. The difference between the TTS caused by exposures with the same A-weighted equivalent level, suggests that the frequency characteristics of exposure signals may not be well characterised by the A-weighting curve. The present paper presents the recovery model and discusses the application of the model to the present TTS data.