The role of the envelope in the discrimination of rippled spectra by listeners with different auditory sensitivity

A sound signal with a rippled spectrum exhibits envelope periodicity, which is absent in signals with a continuous spectrum. The study investigated the role of the signal envelope in discriminating signals with rippled spectra. The test signal was noise with a rippled spectrum and a spectral bandwidth of 2 octaves. Noise with a continuous spectrum was used as a reference signal. The experiments involved listeners with different levels of auditory sensitivity. To assess the ability to distinguish the density of rippled spectrum, a phase-reversal test was applied. Discrimination thresholds for spectral density were determined depending on the ripple spacing for two types of signals: without envelope modulation and with added envelope modulation. A decrease in auditory sensitivity resulted in a reduced ability to discriminate spectral density at all ripple spacing values. Amplitude modulation led to a deterioration in discrimination ability across all listeners and for all ripple spacing values, though not to thresholds determined by spectral mechanisms. It is suggested that discrimination in this task is driven by a temporal analysis mechanism rather than by envelope periodicity. The addition of modulation reduced the perception of repetition pitch.