Spectral Effect and Overshoot in Simultaneous Masking by Broad-Band Noise Bursts

Abstract

The behavior of a making transient which indicates that simultaneous masking of a short signal by a longer broad-band noise burst is larger at the onset of masker burst than later was investigated. The masked threshold of signal pulses as a function of different variables such as rise-fall time of signal and masker, cut-off frequency of masker, frequency of signal, delay time between onset of masker and onset of signal, and duration of signal and masker was measured.The results were as follows:1) The overshoot depended on the masker components about three critical band away. As a consequence, the spectral effect was not responsible for most of the overshoots.2) This overshoot increased up to 12dB when masker is white noise.3) The same overshoot occured at the slopes of high-passed and low-passed noise as well as on the plateau. This means that the overshoot could not be interpreted as the development of the critical band. But the overshoot which can be measured on the center frequency of bandsuppressed noise masker increased.4) The overshoot could not show any influence of signal duration on the shape of the threshold pattern for longer duration than 20msec.5) The masked threshold rose up several decibels when the duration of the masker decreased until approximately 50msec. The same high threshold appeared even for 20msec duration. This indicated that the maximal excitation of the masker appeared almost instantaneously.