The temporary threshold shift (TTS) produced by intermittent noise of duty cycle less than 4 minutes was examined on five subjects with normal hearing acuity. The net duration of exposure was fixed as long as thirty minutes and the on fraction (R) and duty cycle (D) of intermittent noise were varied as follows. R: 0.2, 0.4, 0.5, 0.6, 0.8 D: 1, 4, 16, 60, 120, 240 sec. TTS at 2, 3, 4, 6, and 8 kc following each exposure of total thirty combination of R and D were compared with TTS produced by continuous exposure. Results obatained were as follows. 1. TTS at any test frequency (form 2 kc to 8 kc) was approximately proportional to the on fraction (when duty cycle was in the range from 1 second to 4 minutes). 2. Although TTS produced by noise of which duty cycle was 2 minutes or 4 minutes seemed to be smaller than those by shorter duty cycles, no signicant differences were recognized in the analysis of variance among duty cycles.

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According to the latest tendency of health supervision at enterprises in our country, the need for the mental and psychological technique is intensively felt because of the change in the nature of work. From the above stand point, the author checked up the mental and psychological functions by means of MMPI and several other tests and compared the accident-prone group with the control group. The results were as follows; (1) As to MMPI patterns, there were more persons with a high score in the accident-prone group than in the control group. Those with a high score in MMPI could be put into 3 groups, high in 6, 8 (Pa, Sc), high in 1, 3 (Hs, Hy) or sometimes high in 1, 3, 7, (Hs, Hy, Pt), and high in 4 (Pb). (2) All of those who had high score codes in MMPI and at the same time belonged to the abnormal or questionable type by the Uchida-Kraepelin test belonged to the accident-prone group. None out of them was found in the control group. (3) Though many reports of the mental and psychological analysis have discussed the number of affirmitive answers ("yes" answers) in CMI-health questionnaire, the few- "yes" persons were found to be included in those having high score codes in MMPI. A significant and suggestive correlation was seen between their personality and accident liability. (4) Persons who had accidents of a certain frequency within a definite term was chosen, and the results of the tests performed on the accident-prone group with those on the control group were compared. The present method proved to be efficient in screening the accident-proneness. Though we cannot decide finally that certain people are accidentprone by choosing them through such a simple mechanical method, it seems to have a significant value as a first step in the screening.

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