A3D was a technology developed by Aureal Semiconductor

Aureal Semiconductor

Aureal Semiconductor Inc. was an American electronics manufacturer, best known throughout the mid-late 1990s for their PC sound card technologies including A3D and the Vortex The company was the reincarnation of the, at the time, bankrupt Media Vision Technology...

 for use in their Vortex

Aureal Vortex

The Vortex audio accelerator chipset line from Aureal Semiconductor was designed to improve performance of their then-popular A3D audio technology. The first member of the line, the Vortex AU8820, was announced on July 14, 1997, and was used in by a number of sound card manufacturers, like Yamaha...

 line of PC sound chips to deliver three-dimensional sound through headphones, two or even four speakers. The technology used head-related transfer function

Head-related transfer function

A head-related transfer function is a response that characterizes how an ear receives a sound from a point in space; a pair of HRTFs for two ears can be used to synthesize a binaural sound that seems to come from a particular point in space. Some consumer home entertainment products designed to...

s (HRTF), which the human ear interprets as spatial cues indicating the location of a particular sound source. Many modern sound card

Sound card

A sound card is an internal computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces that use software to generate sound, as opposed to using hardware...

s 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

Environmental audio extensions

The environmental audio extensions are a number of digital signal processing presets for audio, present in Creative Technology's later Sound Blaster sound cards and the Creative NOMAD/Creative ZEN product lines...

.

A3D differs from various forms of discrete positional audio

3D audio effect

3D audio effects are a group of sound effects that attempt to widen the stereo image produced by two loudspeakers or stereo headphones, or to create the illusion of sound sources placed anywhere in 3 dimensional space, including behind, above or below the listener.There are several types of 3D...

 in that it only requires two speakers, while surround sound

Surround sound

Surround sound encompasses a range of techniques such as for enriching the sound reproduction quality of an audio source with audio channels reproduced via additional, discrete speakers. Surround sound is characterized by a listener location or sweet spot where the audio effects work best, and...

 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

Surround sound

Surround sound encompasses a range of techniques such as for enriching the sound reproduction quality of an audio source with audio channels reproduced via additional, discrete speakers. Surround sound is characterized by a listener location or sweet spot where the audio effects work best, and...

.

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

Environmental audio extensions

The environmental audio extensions are a number of digital signal processing presets for audio, present in Creative Technology's later Sound Blaster sound cards and the Creative NOMAD/Creative ZEN product lines...

 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 http://web.archive.org/web/19990829025202/www.aureal.com/cgi-bin/pub/display.pl?template=press_aur_detail.htm&serial=76, 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. 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.