Fig. 1.

Schematic illustration of two-interval forced-choice tone-in-noise detection. In the fixed-level condition (A), adding a near-threshold tone to a narrowband noise stimulus increases the overall energy and reduces the slopes of the envelope fluctuations of the stimulus (Richards 1992; Mao et al. 2013). Both energy and temporal cues are reliable in this condition. In the roving-level condition (B), blue arrows indicate independent level variation for each stimulus interval. The 20-dB rove range is illustrated by the red (mean level, +10 dB), white (mean level, −10 dB), and black (mean level) waveforms in the bottom panels. The level variation across intervals and trials renders energy cues unreliable because the interval containing the tone-plus-noise may be the one with the lower energy. On the other hand, the temporal fluctuations in the stimuli are not affected by the roving-level paradigm, except that they are scaled in amplitude. Thus, metrics that describe temporal envelope cues, such as the normalized slope of the envelope, are unaffected by the roving-level paradigm.