Modulation masking produced by masker modulation tone complexes

Abstract

Thresholds were measured for detecting a sinusoidal amplitude modulation in the presence of a masker-modulation tone complex. Both modulations were applied to the same sinusoidal carrier. Two different masker modulations were used: (i) a pair of components beating at the signal-modulation frequency and (ii) a three-tone complex producing a sinusoidal amplitude modulation in the modulation domain whereby the frequency of the slow amplitude variation was equal to the signal-modulation frequency. Masked thresholds were measured as function of the phase of the signal modulation relative to the slow amplitude variation in the masker modulation. In all conditions, thresholds were lower for an in-phase signal modulation compared to an antiphase condition. The maximum threshold difference was 15 dB. The results are in contrast to recent data [B. C. J. Moore et al., J. Acoust. Soc. Am. 106, 908–918 (1999)], where the lowest thresholds were obtained for the antiphase condition. Our data are in line with the idea that a nonlinearity prior to the modulation filterbank extracts the slow variation of the masker modulator. The data could be fitted well by assuming a combination of a peripheral (power-law) compression and a threshold. Peripheral compression alone did not account for the data.