ASA 127th Meeting M.I.T. 1994 June 6-10

4aPP17. Interaction of three different types of maskers.

Walt Jesteadt

Christina J. Kessler

Donna L. Neff

Boys Town Natl. Res. Hospital, 555 N. 30th Street, Omaha, NE 68131

Models of additivity of masking typically assume that the same compressive nonlinear transformation is applied to all individual masking effects before they combine. The results for combinations of three different types of maskers are not easily predicted, however, if some pairwise combinations of maskers show more compressive effects than others. To explore this question, adaptive thresholds were obtained for a 24-ms, 1600-Hz signal in the presence of three different maskers presented alone and in various combinations: (1) a 400-ms broadband noise simultaneous masker; (2) a 400-ms octave-band noise simultaneous masker centered at 500 Hz, and (3) a 296-ms, 1600-Hz forward masker with a 4-ms signal delay. The broadband noise was presented at 10 dB No; the other two maskers were presented at seven levels that produced a range of masked thresholds 15 dB above and below that for the broadband noise. Results will be discussed in terms of an associative model in which the effects of two maskers combine and the pairwise effect then combines with the third masker. This model could be applied to data for listeners with sensorineural hearing loss, where the hearing loss is treated as a masking effect. [Work supported by NIDCD.]