Auditory ‘images’ have been described as ‘splitting’ into two distinct images when spatial cues fluctuate and are distributed broadly enough across carrier waveforms. If we consider that visual ‘images’ can often have at least two edges, another way of describing this phenomenon is to say that the edges of single auditory images ‘split’ apart when spatial cues are distributed broadly enough.

The following demonstrations are designed to help compare conditions when interaural differences are narrowly or broadly distributed. 🎧 required.

• Edges overlap when noise-bursts are binaurally similar (‘diotic’) and interaural differences are narrowly distributed.
• In contrast, edges ‘split’ apart when noise-bursts are dissimilar or (‘dichotic’) and interaural differences are broadly distributed.

• Noise-bursts are two seconds long with 1/frequency spectra. Each was embedded within six seconds of relatively quiet (-56 dB re: the level of each noise-burst) binaurally independent 1/frequency noise.
• Interaural time differences (ITD) across waveform envelopes are not (yet) shown but are important for the emergence of ‘edges’ at frequencies above ~1 kHz.
• Interaural level differences (ILD) fluctuate with ITDs and may or may not contribute to the emergence of ‘edges’.
• Binaurally ‘Independent’ noise was generated with distributions of ITD and ILD observed under a broad range of typical listening conditions. The distributions are statistically independent except at low frequencies.