Increasing the Vertical Image Spread of Natural Sound Sources using Band-Limited Interchannel Decorrelation

An experiment has been conducted to assess the perceptual effect of vertical interchannel decorrelation between pairs of vertically-spaced loudspeakers. The study focuses on band-limiting the vertical decorrelation of natural sound sources in groups of octave-bands, while reproducing the unprocessed octave-bands monophonically through the main-layer loudspeaker. The upper limit of the vertical decorrelation is fixed at the 16 kHz octave-band, with the lower limit varied across eight octave-bands (centre frequencies 63 Hz to 8 kHz). A monophonic unprocessed condition was also included in a multiple comparison test alongside the eight decorrelated conditions. The results demonstrate that vertical decorrelation of the 500 Hz octave-band and above can significantly increase the vertical spread of an auditory image, similar to that of broadband decorrelation. Furthermore, decorrelation of solely the 8-16 kHz octave-bands can significantly increase vertical spread, provided the source signal has sufficient high frequency energy.