This paper reports the state of the art of the method for predicting TTS following exposure to noise having an arbitrary spectrum and temporal characteristics. Existence of the critical band for TTS was proved by two of the present authors from the results of their experiment. The center frequency and the width of the critical band were calculated, together with their 95% confidence limits. The theory of critical band enabled us to estimate TTS at a given test frequency due to noise having any spectrum content. In order to estimate the growth of TTS with the exposure time, new empirical formulae of TTS growth were determined based on the results obtained in the 8-h TTS experiments with exposure levels from 85 to 95 dB and those obtained in the 24-h TTS experiments with exposure levels from 65 to 86 dB. The formulae assume an asymptotic threshold shift and are expressed as a function of the exposure duration and the spectrum level of the exposure noise at the center frequency of critical band with respect to TTS. TTS due to steady state noise can be estimated by means of the critical band theory and the formulae of TTS growth. For the non-steady noise exposure, application of the method of unit step function is proved useful to estimate the TTS produced. The idea of the method is to approximate the temporal level change of the noise by a step function and then apply the formula of TTS growth to each of the steps where the level of noise is regarded as steady.