Abstract
As a part of experimental study on the relative noisiness of the steady sounds and the periodically intermittent sounds, four series of psychoacoustical experiments were carried out in order to clarify the difference of habituation of these sounds as the duration increased up to two hours. By the ordinary psychophysical methods, two sound stimuli could be directly compared only within the span of about one minute at most. So a tentative method was devised here as an alternative on the ordinary methods. Subjects were exposed alternately to the steady sounds and to the intermittent sounds for a set duration, and just prior to and after the exposure they were asked to judge the relative noisiness of these sounds by adjustment method or a paired comparison method. The habituation by the exposure made the post-exposure judgement lower than the pre-exposurejud-gement. The difference were analyzed according to the types of stimuli and the lengths of exposure. The results obtained from the four series of experiments can be summarized as follows : 1) The habituation of the perceived noisiness of periodically intermittent sounds is larger than that of the steady sounds. 2) The difference of habituation increases as the duration increases up to 30 minutes. 3) The difference of habituation, however, is comparatively small with a maximum of 1 to 2dB(A). 4) The difference shows a high positive correlation with the relative burst levels of the intermittent sounds.
