When two sounds which have same spectrum but different amplitude are alternated without silent gap between the sounds, the lower amplitude sound comes to be heard as continuous. This is called “auditory induction” which is one of the most interesting auditory phenomena. The fainter sound is called inducee and the louder sound is called inducer.
The authors previously reported that the addition of interrupted pure tone to continuous white noise induced the pulsed noise. This pulse phenomenon was thought to be a kind of auditory induction; the inducer is the noise image of white noise with the silent part of interrupted pure tone and the inducee is the noise image of white noise with the pure tone part of interrupted pure tone. The authors hypothesized that an auditory filter made with the pure tone of interrupted pure tone generates the two noise images in the continuous white noise. Present experiments were made to investigate the change of “the threshold of interrupted pure tone for inducing the pulse phenomenon” (TIP) when the presentation level of continuous white noise and the frequency of interrupted pure tone are changed. TIP was constant and independent of both the amplitude of continuous white noise and the frequency of interrupted pure tone. All subjets reported that the higher the frequency of interrupted pure tone is, the harder it becomes to hear the pulsed noise image. It is supposed that this phenomenon does not contradict the theory of the auditory filter.
