The “cocktail-party effect” and prosodic rhythm: Discrimination of the temporal structure of speech-like sequences in temporal interference

A dimension crucial for the perceptual segregation of simultaneous speech sounds is the one of syllabic and subsyllabic envelope fluctuations, indicating that, in the “cocktail-party effect,” prosody plays a definite role. This role was investigated in a psychoacoustic study using a much reduced stimulus configuration to examine the way the rhythmic pattern of a target stream can be segregated from another, irrelevant stream. Both streams consisted of 40-ms bursts of harmonic complexes with different fundamental frequencies and the same average modulation rate. The target stream had a three-burst dactyl or amphibrach rhythm, whereas the interfering stream’s burst rhythmic pattern was random. Results showed that a higher-f0 target mixed with a lower-f0 interference was significantly easier to identify than the opposite, and that difficulty of the task increased with modulation rate. Elderly subjects performed significantly poorer than the young, for both segregating streams based on prosodic rhythm and understanding speech in babble.