3D audio effects are a group of sound effects that manipulate the sound produced by stereo speakers, surround-sound speakers, speaker-arrays, or headphones. This frequently involves the virtual placement of sound sources anywhere in 3 dimensional space, including behind, above or below the listener.
There are several types of 3D audio effects:
- Those that only widen the stereo image by modifying phase information.
- Those that can place sounds outside the stereo basis.
- Those that include a complete 3D simulation.
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Stereo widening[edit]
Widening of the stereo image can be achieved by manipulating the relationship of the center signal M and the side signal S: 
. A positive part of the side signal S is now fed into the left channel and a part with its phase inverted to the right channel. Some boomboxes feature such a process.
Another way of looking at this same effect, without extrapolating a center and side signal from the left and right signals, is to simply add the left signal, slightly attenuated and phase inverted, into the right channel and vice-versa. Taking this a step further, a small delay (20-100ms) can be added to the inverted signal before mixing it back in to the original for output, adding a slight reverberation to the effect.
Placement of sounds outside the stereo basis[edit]
By manipulating parts of the sound according to psychoacoustic findings in phase and sound, it is possible to create sounds beyond the stereo basis. Effects from QSound Labs have been used on albums from Sting and Madonna in the beginning of the 1990s, as well as in the videogame Super Street Fighter II. Similarly, the pioneering work of researchers (Sibbald et al.) at EMI Central Research Labs in England in the 1980s, and later with Sensaura, produced "3D Audio" CDs...
Complete 3D positional audio[edit]
The 3D simulation is the most advanced group of 3D audio effects. Using head-related transfer functions and reverberation, the changes of sound on its way from the source (including reflections from walls and floors) to the listener's ear can be simulated. These effects include localization of sound sources behind, above and below the listener.
Some 3D technologies also convert binaural recordings to stereo recordings. MorrowSoundTrue3D converts binaural, stereo, 5.1 and other formats to 8.1 single and multiple zone 3D sound experiences in realtime.
3D Positional Audio effects emerged in the 1990s in PC and Game Consoles. As a medium, interactive games would benefit perhaps more than any other. However, although some technologies do seem to work better than others, 3D sound in games is still accurately reproduced usually only through headphones.
3D audio techniques have also been incorporated in music and video-game style music video arts. The Audioscape research project, provides musicians with a real-time 3D audiovisual content authoring and rendering environment, suitable for live performance applications.
A site with animations and theory of a system using HRTF's to create 3D Audio: ISVR Virtual Acoustics.
True representation of the elevation level for 3D loudspeaker reproduction become possible by the Ambisonics and Wave field synthesis Principle, MorrowSound True3D and A&G 3D-EST.
3-D audio presentations[edit]
Some amusement parks have created attractions based around the principles of 3-D audio. One example is Sounds Dangerous! at Disney's Hollywood Studios at the Walt Disney World Resort in Florida. Guests wear special earphones as they watch a short film starring comedian Drew Carey. At a point in the film, the screen goes dark while a 3-D audio sound-track immerses the guests in the ongoing story. To ensure that the effect are heard properly, the earphone covers are color-coded to indicate how they should be worn. This is not a generated effect but a binaural recording.
MorrowSoundTrue3D soundscapes include Torino Winter Olympics, ProFootball Hall of Fame, Great Lakes Children's Museum, NokiaWorld 2008 Barcelona, Denver Museum Nature and Science Gates Planetarium, New York Historical Society, Copenhagen International Theatre, Gallery Rachel Haferkamp Köln, Muu Gallery Helsinki, New Sounds New York, ZHDK Zurich, OKKO Design Stockholm, BAFTA Awards London, Collection of Diana Zlotnick Studio City, CA, as well as Ecsite, AAM, ASTC and IPS conventions. These range from single 8.1 to 64.3 True3D installations, some interactive.
Nick Cave's novel The Death of Bunny Munro was recorded in audiobook format using 3D audio.
The song "Propeller Seeds" by English artist Imogen Heap was recorded using 3d audio.
See also[edit]
- Ambiophonics
- Ambisonics
- Binaural recording
- Crossfeed
- Dummy head recording
- Software API for computers Operating systems : Microsoft's DirectSound3D and XAudio, OpenAL
- Sound spatialization
- Surround sound
- Wave field synthesis
External links[edit]
- 3D Audio | AM3D
- Example of 3D sound played back in normal stereo headphones. Requires the Adobe Flash Player
- Listen With Your Own Ears - 3D audio demos
- 3D Audio and Applied Acoustics Lab - at Princeton University
- 3D Sound and music tracks
- il Suono in 3D
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