|Microsoft DirectX 9.0|
When using a DirectSound device with the priority cooperative level (DSSCL_PRIORITY), the application has first rights to hardware resources, such as hardware mixing, and can set the format of the primary sound buffer and compact the on-board memory of the device.
Game applications should use the priority cooperative level in almost all circumstances. This level gives the most robust behavior while allowing the application control over sampling rate and bit depth. The priority cooperative level also allows audio from other applications, such as IP telephony, to be heard along with the audio from the game.