A class of brief waveforms (10 msec) having identical energy spectra and different phase spectra (Huffman sequences) were used in a series of masking experiments. The peak factor of these waveforms can be systematically varied, thus changing the distribution of the energy over the duration of the waveforms. When these waveforms are used as signals, they are equally detectable in white Gaussian noise. However, when these waveforms are used as maskers of sinusoidal signals, they do not produce equal masking. The masked threshold for the sinusoids changes as much as 30 dB as a function of the peak factor of the maskers. [Research supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare, and by a research grant awarded to the Center for Human Information Processing.]
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