A3D

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For the military aircraft, see A3D Skywarrior.

A3D (Aureal 3-Dimensional) is a technology developed by Aureal Semiconductor, and used in their Vortex line of products, that delivers holophonic (three-dimensional) sound through headphones, two or even four speakers. A3D version 3.0 incorporated two core elements, A3Dverb and A3Dspace. The technology uses 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 and some features may be licensed under different product names such as EAX.

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.

Creative Labs sued Aureal for patent infringement in March of 1998[1], and Aureal countersued for patent infringement and deceptive trade practices. Aureal won the lawsuit brought by Creative in December of 1999. However, the cost of the legal battle caused Aureal's investors to cease funding operations, forcing Aureal into bankruptcy. Creative then acquired Aureal's assets in September of 2000 through the bankruptcy court with the specific provision that Creative Labs would be released from all claims of past infringement by Creative Labs upon Aureal's A3D technology. While Creative Labs has not chosen to support the A3D API, the underlying advanced features of A3D technology is making its way into Creative Labs' newer EAX incarnations.^{[citation needed]}