Binaural Unmasking of Vocalic Signals

Abstract

Binaural unmasking was studied using vowels as the target signals. The vowels /a/, /i/, and /u/—each produced naturally and by an electrical analog device at three vocal frequencies—were presented to listeners for detection in a variety of interaural signal-noise configurations. In all listening conditions, the noise was correlated, while the interaural phase relations of the signals were manipulated. A number of conditions were used in which the portion of the signal above or below three selected frequencies—250, 500, and 1000 Hz—was interaurally out of phase, while the remainder of the signal was normal. The data suggest that binaural unmasking of complex amplitude-varying stimuli is best accounted for by the amount of energy in the 250–500-Hz band of the signal relative to the characteristic spectral maxima in the signal. The data also suggest that interaural phase inversions outside the 250–500-Hz band have differential effects on unmasking depending upon the amplitude relations in the band and the energy outside it.