We have developed a system which predicts TTS (temporary threshold shift) in real-time operation at actual noise induced fields. This system consists of a combination of a sound level meter with one-third-octave band filters and a multi-purpose personal computer. At first, a calculation procedure was considered to enable real-time operation. In this consideration, it was found that the predicted value of TTS can be presented as the convolutional summation of the critical band spectrum level for the test frequencies and the impulse response obtained from the existing prediction equations. For Takagi's prediction equation, a time delay in the growth of the predicted TTS was observed, when the applicable conditions were processed by the same procedure for steady noise. An appropriate procedure to remove the time delay for time-varying noise was also considered.

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The environmental quality standard for noise was revised and the evaluation of the environmental noise was shifted L₅₀ into L_Aeq. In an evaluation of L_Aeq, it is needed generally to take a representative one day of L_Aeq during a year. Therefore, it is thought to become major in measurement of the environmental noise by an automatic measurement without manually operating. However, the stability of L_Aeq is not good agreement by comparing with L₅₀ because a level is often influenced by the loud noise which occurred in the accident. Therefore, it is needed to remove an abrupt and reappearanceless sound in automatic measurement. As the way of search for the representative value of the place by using Grubbs-test and Thompson-test was used in the rejecting outliers on the quite difference data in Kawasaki City, Nagano City and Naha City. From these result, we confirm it is very effective method in measuring L_Aeq without manually operating.

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