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EAX Sound Cards

First introduced with its SoundBlaster Live! soundcards in 1998, Creative Technology’s Environmental Audio Extensions (EAX) began as a simple way to add reverberation to DS3D. Reverb – the wash of echoes produced when sound waves bounce off walls in a room – helps us identify an environment. Gunshots in an airplane hangar sound very different than they do in a sewer pipe, for example, but DS3D ignores this fact.

EAX 1.0 was designed to provide developers with the ability to create a convincing sense of environment in entertainment titles and a realistic sense of distance between the player and audio events. The approach Creative took to achieve this was, computationally, significantly easier than the one Aureal had taken with A3D. This was simply to create predefined reverb effects for a variety of environments with different characteristics of reflections and reverberation, different room types and/or room size. EAX 1.0 provided 26 such reverb presets as an open set of extensions to Microsoft’s DS3D. The API also allows for customising late reverberation parameters (decay time, damping, level) and automatic level management according to distance.

Released in 1999, EAX 2.0 enabled the creation of more compelling and realistic environments with tools that allow the simulation of the muffling effects of partitions between environments (such as walls) and obstacles within environments (such as furniture) – it being possible to apply these obstruction and occlusion features each individual audio source. In addition, EAX 2.0 also offers global early reflections – the echoes that immediately precede real-world reverb and provide a better perception of room size and sound-source location – and a tuneable air absorption model. 1999 also saw the announcement of EAX 3.0, which introduced the ability to morph between environments, allows developers to position and control clusters of early reflections, as well as one-shot reflections for ricochet effects and makes full use of technologies such as HRTF for synthesising positional audio on a single pair of speakers.

In late-2000 a number of EAX effects were incorporated into the DirectX Audio component – the functions of which were previously shared between the DirectSound and DirectMusic components – of the latest release of Microsoft’s suite of multimedia APIs, DirectX 8.0. A few months later, Creative unveiled an API platform for games developers wanting to incorporate Dolby Digital content into their games. Earlier soundcards had allowed Dolby Digital to be passed directly through the card and decoded by an external decoder. However, with the 5.1 version of its successful SoundBlaster Live! sound card Creative supported decoding directly through one of their audio products for the first time, the card being able to output straight to six discrete analogue channels.

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