MASKING PERIOD PATTERNS OF SCHROEDER-PHASE COMPLEXES - EFFECTS OF LEVEL, NUMBER OF COMPONENTS, AND PHASE OF FLANKING COMPONENTS

Masking period patterns (MPPs) were obtained for maskers consisting of harmonics 2-20 of a 100-Hz fundamental. The signal was always a 5-ms 1100-Hz sinusoid presented 152, 154, 156, 158, or 160 ms after the sta rt of a 400-ms masker. Experiment 1 replicated the finding that, for a masker level of 69 dB component, the shape of the MPP depended strong ly on the phases of the components: Summing them in positive Schroeder phase led to a threshold variation of about 18 dB across the MPP, but summing them in negative Schroeder phase produced a flat MPP [A. Kohl rausch and A. Sander, J. Acoust. Soc. Am. 97, 1817-1829 (1995)]. Reduc ing the level of the positive-phase masker resulted in a systematic Ba ttening of the MPP, whereas the negative-phase MPPs were Bat both at h igh and at low levels. Experiment 2 showed that removing all component s of a positive-phase masker except those close to the signal raised t hresholds at the minimum of the MPP. In contrast, a similar manipulati on applied to the negative-phase masker produced a uniform elevation o f the MPP. Experiment 3 showed that an analogous effect could be obtai ned by manipulating the phases of masker components remote from the si gnal. It is shown that several features of the data can be simulated u sing a nonlinear model of the auditory periphery [C. Giguere and P. C. Woodland, J. Acoust. Soc. Am. 95, 331-342 (1994)]. (C) 1997 Acoustica l Society of America.