A3D 1.0


A3D is a highly acclaimed, industry leading positional 3D audio solution. A3D technology uses Head Related Transfer Functions (HRTFs) to fully emulate 3D sound from two speakers. A3D is available under license from Aureal for inclusion in DSP and integrated semiconductor devices.

Aureal provides both source and binary A3D licensing packages. Both packages enable full hardware acceleration of all 3D features in Microsoft’s DirectSound standard (specifically DirectSound3D, which is part of DirectSound version 3.0 and higher), as well as any additional features required to accelerate software game titles that have been designed to directly support A3D technology.

A3D has been successfully ported to multiple DSP and CPU architectures

What is A3D?

Aureal A3D is a breakthrough new audio technology that enables a real-life audio experience by surrounding the listener with sounds in all three dimensions using only a single pair of ordinary speakers or headphones. Aureal 3D is based on recreating all the hearing cues that allow us to perceive sounds in everyday life. The key to A3D lies in the following fact: since we can hear sounds three dimensionally in the real world with only two ears, it must be possible to create sounds from two speakers that have the same effect.

A3D technology forms the basis for two groups of applications:

  • A3D Surround: produces Dolby(r) certifiable playback of surround sound encoded soundtracks over a single pair of speakers or headphones.
  • A3D Interactive: enables interactive 3D audio - a highly immersive and realistic 3D listening experience - for video games, 3D Internet sites and other interactive software applications.

A3D Compared to other "3D" Technologies

Since the late 1970's, several audio technologies have been developed to advance the state of the art in audio reproduction beyond stereo. They can be grouped into three areas:

Stereo Extenders

This method takes an existing stereo signal and filters it to make it appear to originate from outside the physical locations of the speakers. The result is an added sense of depth and spaciousness that can improve the stereo listening experience, especially on low-end equipment. The disadvantage of this approach is that by relying on existing stereo content it "inherits" the biggest limitation of stereo: it is one-dimensional (left/right). Additionally, this form of processing usually introduces headphone incompatibilities and some coloration of the original audio content. Extended stereo technologies such as SRS(tm), Spatializer(tm) and QSound(tm) are sometimes marketed using the labels "3D Sound" or "3D Stereo".

Surround Sound

The concept of surround sound is based on physically adding speakers (usually to a total of five) to surround the listener with sounds coming from five instead of two directions. Audio en-coding technologies such as Prologic(r) or AC-3(r) are employed to compress the additional audio channels for transmission and delivery. While not designed for interactive environments, surround sound is very effective for movie soundtracks and other pre-recorded audio environments. The cost and setup complexity of additional speakers, decoders and amplifiers can be a limitation.

Interactive 3D Audio (Aureal A3D)

Using a pair of ordinary speakers or headphones, this method recreates the same audio cues that allow us to pin-point the location of a sound in the real world. The result is a real-life listening experience with sounds surrounding the listener in all three dimensions. In addition to added dimensionality, this technology allows for real-time placement of sounds via an application programming interface to enable fully interactive applications.

Since 3D usually refers to the three dimensions of X, Y and Z (front/back, up/down, left/right), only the "Interactive 3D Audio" category should be called 3D sound. Unfortunately, all of the above types of sound processing have been labeled "3D" sound in the past. The good news is that both Microsoft and Apple have publicly announced plans to provide APIs (Application Programming Interfaces; Direct3D-Sound(tm) in Microsoft's case) to give software developers access to technologies of the "interactive 3D audio" category. These APIs are expected to help clarify what capabilities are expected from a "3D" audio device. What this all means is that a new breed of applications bringing tremendous realism and excitement to users is getting enabled. And people are choosing Aureal A3D to make it happen today.

Aureal A3D Interactive

What is interactive 3D audio? Interactive applications are based on the idea of creating a virtual environment that can be navigated by a user while a story line unfolds in unpredictable ways based on the user's actions and inputs. The most fun and engaging environments are the very realistic ones that put the participant in the middle of a three-dimensional world with action happening all around: racing games, 3D Internet sites, flight simulators or first person video games to name a few. 3D environments are wildly popular and have actively pushed the envelope of 3D graphics systems in recent years. But what about audio? For audio to be interactive, it needs to be created "on-the-fly", just like the visuals. And to make the audio as realistic as the visuals, it needs to unfold all around the listener. If a monster enters a scene from behind you, its roar has to sound like it's coming from behind, so you can swirl around and face it.

Today's audio systems are not capable of such effects: stereo can only put a sound left or right. Extended stereo (a.k.a. 3D stereo) can put it a little further left or right, but still not above, below or behind. Surround sound can do behind, but won't work for interactive applications because the soundtrack needs to be pre-encoded. What is needed is a new technology that is interactive and allows for realistic, fully three-dimensional placement of sounds - Aureal A3D Interactive is that technology.

Aureal A3D Surround

Aureal A3D Surround is based on Aureal A3D audio technology that allows exact placement of sound sources in the 3D space surrounding a listener using just two ordinary speakers or a pair of headphones. The key to A3D Surround is to combine Aureal A3D technology with a surround sound decoding technology such as Dolby(r) ProLogic(r) or Dolby(r) Digital AC-3(r). The surround sound decoder produces five audio streams that have been pre-mixed in a recording studio to create a sound field that surrounds the listener. Instead of playing those five streams back on five physical speakers, they are passed through the A3D Surround process that projects 5 "virtual speakers" into space. The result is a Dolby certifiable surround sound experience from just two speakers!