DirectSound3D (along with DirectSound, is refereed to as DirectX Audio) was introduced in 1996 with DirectX 3 as an addition intended to provide support for 3D Audio in the Microsoft Windows operating systems.
Other DirectX related glossary:
DirectDraw
Direct2D
Direct3D
DXGI
DirectInput
DirectPlay
DirectPlay Voice
DirectSound
DirectSound3D
DirectMusic
DirectX Audio
DirectX Media
DxDiag
DirectX Media Objects
DirectSetup
XAudio2
