The Effect of Envelope or Carrier Delays on the Precedence Effect

Listeners who hear a pair of acoustic stimuli, such as a speech signals from two different directions with a short delay in between, tend to perceive a fused sound from the direction of the first sound to arrive (the precedence effect). As the delay between signals increases, however, the two sounds are perceived as multiple sounds that reflect the directions of the lead and lag sounds (sound image separation). The present experiments on the perception of sound images used pairs of speech signals that included time delays on either their envelopes for each 1/4-octave band, or the carriers, or both. The speech was wide band, low-pass, or high-pass filtered. The results were consistent with a two process model. A low frequency process produces the precedence effect using carrier delays and image separation using envelope delays. A high-frequency process produces both effects, but only from envelope delays.