[Pulse phenomenon of continuous white noise with interrupted pure tone]

The researches of masking made it clear that there is a bandpass like a filter in the auditory system. This is called the auditory filter and its central frequency is thought to be the frequency of an acoustic signal. If there exist this kind of filter, the authors expected that the noise image which is perceived when pure tone and noise simultaneously presented is different from the one which is perceived when noise is presented independently. The authors chose an interrupted pure tone as an acoustic signal and continuous white noise as noise, and experimented to investigate the pure tone effect on perception of white noise. As a result, two stimulus tones induced three sound images, which are sound images of continuous noise, a pure tone and pulsed noise. The sound image which listeners did not expect to hear was the pulsed noise image. This phenomenon was thought to be an auditory induction; the inducer is the sound image of the white noise presented with the silent part of pure tone of interrupted pure tone and the inducee is that of the white noise presented with pure tone part of interrupted pure tone. This pulse phenomenon suggests that pure tone change the loudness of white noise. This finding is interesting for researches of auditory mechanism and for the field of hygienics with protecting the auditory system and improving hearing under the noisy environment.