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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 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 1998 , and Aureal countersued for patent infringement and deceptive trade practices. Aureal won the lawsuit brought by Creative in December 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 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. Creative Labs has not chosen to support the A3D API. But the technics have trickled down, as EAX 5.0 features occlusions, which is wavetracing, and CMSS-headphone, which is HRTF.
- "Aureal And Creative Engage In Legal Skirmish". 1998-03-05. Archived from the original on 1999-08-29. Retrieved 1999-08-29. (through Internet Archive)