Speech masking. I. Simultaneous and nonsimultaneous masking within stop /d/ and flap closures.

This article reports on investigations of the relative roles of simultaneous and nonsimultaneous masking on detection thresholds using natural speech utterances. Thresholds were obtained for 15-ms probe tones placed in the stop or flap closures of /ada/ and /idi/. Threshold elevations due to simultaneous and nonsimultaneous masking could be explained by the dynamics of neighboring speech spectra. Nonsimultaneous effects were related to spectra at least 30 ms around the probe tone. Although simultaneous masking is usually stronger than nonsimultaneous masking, the relative amplitude of adjacent speech segments in natural speech is sufficiently high near formant regions to cause noticeable effects of nonsimultaneous masking.