binaural (adj.)

"dual, twofold, double," mid-15c., from Late Latin binarius "consisting of two," from bini "twofold, two apiece, two-by-two" (used especially of matched things), from bis "double" (from PIE root *dwo- "two"). Binary code in computer terminology was in use by 1952, though the idea itself is ancient. Binary star in astronomy is from 1802.

1844, "pertaining to the ear," from Latin auris "the ear as the organ of hearing" (see ear (n.1)) + -al (1). The meaning "received or perceived by ear" is attested by 1860. Related: Aurally.