Comparison of intensity discrimination, increment detection, and comodulation masking release in the envelope and audio-frequency domains

In the audio-frequency domain, the envelope apparently plays an important role in detection of intensity increments and in comodulation masking release (CMR). The current study addressed the question whether the second-order envelope ("venelope") contributes similarly for comparable experiments in the envelope-frequency domain.

One set of experiments examined the relationship between gated intensity discrimination and continuous-carrier increment detection. In contrast to the asymmetry observed in the audio-frequency domain (listeners are more sensitive to increments), AM-depth discrimination thresholds were found to be the same in conditions with a continuous (modulated) carrier and with traditional gated stimuli for AM frequencies ranging from 4 –64 Hz.

The second set of experiments compared the amount of CMR in a tone-in-noise detection task when slow, regular fluctuations were imposed on the masking waveform in both domains. A significant release from masking of a 32-Hz signal in the modulation frequency domain was obtained only when the venelope fluctuations were slower than 1–2 Hz.

Both experiments suggest a relatively weak contribution of venelope cues in the AM domain when compared to those provided by envelope cues in the spectral domain.