In Experiment I influences of the duration of a intermittent sound, 0.1 or 1 cosec, on the effect of the intermittent sounds on time estimation were examined by the reproduction method in children of 7 to 10 yr. and adults. Frequencies of the intermittent sounds which were given during the reproduced duration were 2.5, 5.0, 7.5, 10.0, 15.0, and 20.0 cps. Main results were as follows: Generally, the higher the frequency of the intermittent sounds was, the shorter the reproduced duration was. The younger the subject was, the greater this effect was. And these tendencies were the same under the two conditions of the duration of one intermittent sound. In Experiment II it was confirmed that the general effect of the intermittent sounds on time estimation above mentioned held good under the large Grange of frequencies from zero to 100 cps. Intermittent sounds of 100 cps were Beard continuous.