Masking of short probe sounds by tone bursts with a sweeping frequency.

The masked threshold of short (less than or equal to 40 ms) probe tone or a short one-third octave probe noise appears to increase if the frequency of a tonal masker is swept. Frequency sweeps were exponential (octave/s) and unidirectional. Probe sounds were presented in the time center of the masker at the center frequency of the masker. The sweep speed, S, appeared to be an important parameter; masker duration was much less important. For 10-ms tonal probes, in-phase with the masker in their common time center, 100-ms maskers, and upward sweeps, increase of the masked threshold appeared to be maximal at a sweep speed of 30 oct/s and the masked threshold was 21 dB higher than the masked threshold found for the stationary masker (S = 0 oct/s). Above 30 oct/s the masked threshold decreased. For downward sweeps masking was maximal at S = 20 oct/s and the threshold was 15 dB higher. Sweeping upward the increase in masking was 12 dB for both noise probes and tonal probes with phase differing by 90 degrees from the masker in their common time center. The results are inconsistent with current models of masking: sweeping the frequency the masked threshold increases whereas the energy within the critical band at the probe frequency decreases.