Applications can specify the distances at which 3-D sounds stop getting louder or quieter. For an overview of these values, see Distance Measurements.
The default minimum distance, defined in Dsound.h as DS3D_DEFAULTMINDISTANCE, is currently 1 distance unit (normally 1 meter). The default maximum distance, defined as DS3D_DEFAULTMAXDISTANCE, is effectively infinite.
An application sets and retrieves the minimum distance value by using the IDirectSound3DBuffer::SetMinDistance and IDirectSound3DBuffer::GetMinDistance methods. Similarly, it can set and retrieve the maximum distance value by using the IDirectSound3DBuffer::SetMaxDistance and IDirectSound3DBuffer::GetMaxDistance methods.
By default, distance values are expressed in meters. See Distance Factor.