Low interaural coherence makes sound events seem diffuse and surrounding

Evidence

When IC is high, as when in an anechoic chamber, the auditory events are localized to be point-like. When a broadband sound signal, such as pink noise, is presented with low IC, either using headphones or multiple loudspeakers, subjects perceive an auditory event that is located in surrounding directions or in many directions at the same time (Blauert, 1996). — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1446

When IC is high, as when in an anechoic chamber, the auditory events are localized to be point-like. When a broadband sound signal, such as pink noise, is presented with low IC, either using headphones or multiple loudspeakers, subjects perceive an auditory event that is located in surrounding directions or in many directions at the same time (Blauert, 1996). It has been found that humans are especially sensitive to coherence at low frequencies with narrowband signals (Culling et al., 2001). However, the perception of broad sources is not limited to low-frequency signals only. When multiple loudspeakers are used to reproduce incoherent high-frequency content, a spatially broad auditory event is perceived (Santala and Pulkki, 2011). In normal rooms, the IC is high when the onset of an impulsive sound arrives at the ear canals, and the IC is lower when reflections and the room effect in general arrive at the ear. Faller and Merimaa (2004) suggest that localization occurs only if the IC has a high enough value. Alternatively, as discussed in the previous section, low coherence also causes ILD and ITD cues to fluctuate randomly with time and frequency (Goupell and Hartmann, 2007). These fluctuations, caused by the low IC, are assumed to lead directly to a perception of surrounding auditory events, and no separate IC cue is computed in the auditory system. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1446

When IC is high, as when in an anechoic chamber, the auditory events are localized to be point-like. When a broadband sound signal, such as pink noise, is presented with low IC, either using headphones or multiple loudspeakers, subjects perceive an auditory event that is located in surrounding directions or in many directions at the same time (Blauert, 1996). It has been found that humans are especially sensitive to coherence at low frequencies with narrowband signals (Culling et al., 2001). However, the perception of broad sources is not limited to low-frequency signals only. When multiple loudspeakers are used to reproduce incoherent high-frequency content, a spatially broad auditory event is perceived (Santala and Pulkki, 2011). In normal rooms, the IC is high when the onset of an impulsive sound arrives at the ear canals, and the IC is lower when reflections and the room effect in general arrive at the ear. Faller and Merimaa (2004) suggest that localization occurs only if the IC has a high enough value. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1446

Categorization

• SHARE: A colleague working in spatial audio rendering would appreciate the direct headphone/loudspeaker application of IC control to convey diffuseness.
• XREF: Links to the reader’s interest in acoustic spatialization applications (surround sound, binaural reproduction, room acoustics).
• QUESTION: Whether the auditory system computes separate IC cues or derives the effect from fluctuating ITD/ILD remains unresolved — worth chasing.
• corroborated: 3 independent passages support this claim — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1446