Masking of short tones in noise: Evidence for envelope-based, rather than energy-based detection

Abstract

A short tone added to a longer simultaneous masker may be detected by observing an increase in overall acoustic energy. This detection scheme predicts probe thresholds to be independent of the masker’s temporal envelope. A recent study [Jennings et al., J. Assoc. Res. Oto. 19, 717–727 (2018)] revealed that probe thresholds were 10 dB higher for maskers with flattened compared to fluctuating envelopes, suggesting an envelope-based detection strategy. This study test the hypothesis that probe thresholds are proportional to envelope power by measuring detection thresholds for a 4-kHz, 6-ms probe in one of three temporal positions within a 400-ms masker in normal-hearing listeners. The narrow-band, low-fluctuating noise masker was preceded by flattened or fluctuating noise precursors. The precursor’s offset was delayed from the masker’s onset by -2, 0, 10, 25, 100, or 250 ms. Probe thresholds were positively correlated with envelope power (R-squared = 0.75), consistent with masking from precursor envelope fluctuations and from fluctuations introduced by precursor and masker ramps. These findings suggest that future modeling efforts for short probes presented in longer maskers should consider a decision variable based on envelope fluctuations.