Aureal
Semiconductor appeared on the scene shortly after Microsoft had released the first version of DirectSound3D in 1996. It was a meld of Crystal River Engineering, who had done audio stuff for professional customers like NASA and MediaVision who had produced rather good soundcards. The idea was to raise sound quality and real-time
response by using a specialized DSP chip on the soundcard and better algorithms than the very rough ones of DS3D.
They had problems creating a chip which would handle all DSP and also connect to the PCI bus. Furthermore, MediaVision wore the stigma of the people who had cloned Sound Blaster 16 cards. The first A3D soundcard (Monster Sound XL) was based on a programmable AD2181 DSP that had not been developed for the special purpose of positional audio and therefore was rather weak yet expensive; it could process "only" eight 3D voices simultaneously. This number had been the maximum polyphony of most DOS game engines since 1993, therefore games used mostly short sounds, hence this limitation was not as bad as it may look. A3D-capable hardware and the A3D API which roughly used the syntax of Microsoft's DirectSound3D API was a success: Many games released from 1997 to 1999 used it.
Few people used four (or more) speaker setups in the late 90's, thus Aureal implemented special algorithms for two speakers and especially headphones. This can sound impressive in A:B comparisons and had been further improved by Sensaura, but true three-dimensional sound means either at least 6 speakers or headphones plus detection of head movement.
When DirectX 5 came out in 1997, DirectSound3D (DS3D) was no longer bound to rendering on the CPU, but could use a DSP chip. In Autumn 1998, just over 1 year after the first A3D soundcard, the Sound Blaster Live was released. Creative Labs was ramping up efforts to battle Aureal.
In 1997 Aureal announced A3D 2.0:
"Aureal Wavetracing parses the 3D geometry description of a space to trace sound waves in real-time as they are reflected and occluded by passive acoustic objects in the 3D environment. This means that sounds cannot only be heard as emanating from a sound source in 3D space, but also as they reflect off of walls, leak through doors from the next room, get occluded as they disappear around a corner, or suddenly appear overhead as you step into the open from a room". At the time, the only consumer chip that supported A3D 2.0 was the Vortex 2 (AU8830).
A3D used 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 only simulated the environment with an adjustable reverb - it didn't calculate any actual reflections off the 3D surfaces. While A3D 1.0/2.0 did not generate reverb, Aureal was steadily moving towards filling that gap soon. Creative Labs opted to apply a quick solution that was already common in music production studios (static reverb machines) to gaming audio that could be sold to the masses. EAX sounded richer than A3D, and its superficiality seemingly did not matter.
Since A3D was a proprietary licensed standard, many developers dropped A3D as soon as a free alternative was there. EAX, DS3D were free - but not necessarily open standards. Besides, Wavetracing hardware is useless if games were not using it. Aureal was interested in providing a well-sounding translation to EAX and DS3D. The industry preferred to go on with the high market share and low technical competence of Creative Labs. Adding to that, the shipping of Vortex 2 boards was delayed some months beyond the SB Live, and Aureal's partnership with Diamond Multimedia suffered setbacks. In the press EAX was the star while A3D 2.0 was rarely talked about.
In 1998 Creative sued Aureal for patent infringement. Aureal countersued because they believed Creative was guilty of patent infringement.
In 1999 newer versions of DS3D and Creative Labs' EAX were released. There were rumors that Creative Labs and Microsoft had established a close communication in order to fix bugs, ease software development and implement some features of A3D - of course under new labels so they could avoid strengthening A3D and paying licensing to them. DS3D soundcards came with a pseudo "a3d.dll" which answered the A3D calls that a game may make and translated them into DS3D calls.
In 2000 Aureal announced the Vortex SQ3500 Turbo:
"We expect our latest offering to make some real waves in the PC audio community," said Brendan O'Flaherty, Aureal's senior vice president of operations. "The SQ3500 uses the unprecedented power of both the Aureal Vortex2 processor and our new Turbo DSP module to deliver acceleration for A3D 3.0, advanced geometry-based reverberation, and Dolby Digital decoding, resulting in a package that should appeal to all PC audio users."
The announcement was not fulfilled and the SQ3500 never shipped (there are rumors of some of these cards in the wild however). The result of the previously mentioned lawsuits was the courts ruling in Aureal's favor, but it was ultimately a Pyrrhic victory. Legal fees along with losing financial backing from Diamond Multimedia (and others) sealed their fate. Aureal filed for bankruptcy later that year. After a bidding war with Hercules / Guillemot which reached 21 million USD, Creative bought them out shortly afterward. Creative had succeeded in killing off their biggest competitor (and arguably setting back 3D audio for years). Following Aureal's acquisition by Creative, support for the A3D API was discontinued.
Creative Labs
EAX (Envionmental Audio Extensions) is a sound system developed by Creative Technology Ltd. used by many older games for realistic reverb, surround sounds, doppler effect simulation, surround sound and more.
EAX is compatible with Creative and Realtek (via 3D Soundback software) soundcards.
Hardware accelerated DSP processing of EAX only happens on cards with EMU chips.
Sensaura Technology
Sensaura is a technology and a brand name that was originally developed by Sensaura Ltd., a UK-based company, which specialized in audio technologies and solutions for the personal computer market.
Sensaura's technologies aimed to enhance audio experiences by providing advanced features such as 3D positional audio, environmental sound effects, and software-based audio processing.
Sensaura's technology was used in a variety of sound cards and onboard audio solutions, particularly in the late 1990s and early 2000s.
The company and its technologies were later acquired by Cirrus Logic, which integrated Sensaura's audio processing technology into its audio chipsets.
QSound Labs
Q3D Interactive is a 3D sound positioning technology that is closely coupled to a multi-channel mix engine. Q3D takes one or more signals representing individual voices, instruments, or sound effects, applies processing to position each input independently at the chosen location in 3D space, and mixes the results down to the number of channels required
for the target delivery system.
AMD
TrueAudio is the first serious attempt since the early 2000s to improve the quality and quantity of audio spatialization and effects on the PC.
Starting with Windows Vista, hardware acceleration for DirectSound and DirectSound3D has been dropped. With multi-platform titles (i.e. console ports) becoming increasingly common, PC audio has by most metrics regressed since 2005.
This has led to game audio ranging anywhere from good to terrible, depending on the capabilities of the audio stack used in a game.
The best of games will offer a solid spatialization algorithm (and spend the CPU time to do it) while the worst of games will usually be optimized for a 2 and 5.1 speaker setups, mixing down from that for other setups while using minimal environmental processing and effects.
The entire AMD TrueAudio hardware block is built directly into the die of certain AMD Radeon Rx 200 series cards; most notably the R9 295X2, R9 290X, R9 290 and R7 260X GPUs.
As well as Kaveri and Carrizo-based APUs, including the PlayStation 4.
