Developed by Creative Labs, the Environmental Audio eXtensions (eax) provide both music enthusests and game developers with the ability to alter sound characteristics, such as pitch, reverb, and echo to preset values. This gives them the ability to give a greater depth to the sound.
Microsoft has incorporated EAX into DirectX, and it will become standard on most sound cards. Aureal has sound card drivers out, for example, that give EAX to their Vortex-based soundcard families.