The DirectX SDK has, in the past, supported two APIs DirectSound and DirectMusic for the handling of sound in games. However recently Microsoft have been introducing Xbox APIs into the PC version of DirectX so XACT has been added. DirectMusic will be removed in the November 2007 SDK release. DirectSound is also being removed in the November 2007 SDK release and is being replaced by a new low level sound API called XAudio2.
To summarise: DirectSound and DirectMusic are deprecated and replaced by XACT and XAudio2 APIs.
XACT provides a complete audio creation tool and API for getting sounds into games and playing them back. XACT is primarily a high level content driven API and therefore does not replace DirectSound. Recently Microsoft have added some lower code driven API elements to XACT but it is still not a suitable replacement for DirectSound. See the XACT Notes
Note: from the November 2007 release of the DirectX SDK DirectSound will be removed. It is being replaced by XAudio2.
See the DirectSound notes:
Notes on how to load WAVE (.wav) data:
There are other APIs available for adding sounds to your game. Just because you might use Direct3D for graphics it does not mean you cannot mix it with other APIs. Two popular ones are: