A3D

A3D (Aureal 3-Dimensional) was a technology developed by Aureal Semiconductor for use in their Vortex line of PC sound chips to deliver three-dimensional sound through headphones, two or even four speakers. The technology used head-related transfer functions (HRTF), which the human ear interprets as spatial cues indicating the location of a particular sound source. Many modern sound cards and PC games incorporated A3D via license from Aureal. Due to Aureal's acquisition (see below) the A3D technology is now part of the intellectual property of Creative Labs.

A3D differs from various forms of discrete positional audio in that it only requires two speakers, while surround sound typically requires more than four. The particular advantage of A3D is for dynamic or interactive environments such as simulations, games, video conference, and remote learning. A3D is not as effective for static productions such as movies which typically employ surround sound.

A3D uses a subset of the actual in-game 3D world data to accurately model the location of both direct (A3Dspace) and reflected (A3Dverb) sound streams (A3D 2.0 can perform up to 60 first-order reflections). EAX 1.0, the competing technology at the time promoted by Creative Labs, simulated the environment with an adjustable reverb—it didn't calculate any actual reflections off the 3D surfaces.