Two ears improve detection, localization, and masking resistance over one.

Evidence

Two ears provide binaural summation, or improvements in detection, discrimination, and identification for two ears compared with one. … Two ears provide the ability to localize sound. The duplex theory of sound localization describes the relationship between acoustic cues and perception, with ITDs driving localization for low-frequency sounds and ILDs driving localization for high-frequency sounds. … Listening with two ears reduces the effect of masking in the following ways: The better-ear effect - an acoustic effect in which the auditory system can take advantage of the ear with the better SNR. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 1596

Categorization

• XREF: connects to: Human sound localization is remarkably accurate given it processes only two ear signals. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1423