The IDirectSound3DBuffer::SetConeAngles method sets the inside and outside angles of the sound projection cone for this sound buffer.
HRESULT SetConeAngles(
  DWORD dwInsideConeAngle,  
  DWORD dwOutsideConeAngle,  
  DWORD dwApply             
);
 | DS3D_DEFERRED | Settings are not applied until the application calls the IDirectSound3DListener::CommitDeferredSettings method. This allows the application to change several settings and generate a single recalculation. | 
| DS3D_IMMEDIATE | Settings are applied immediately, causing the system to recalculate the 3-D coordinates for all 3-D sound buffers. | 
If the method succeeds, the return value is DS_OK.
If the method fails, the return value may be DSERR_INVALIDPARAM.
The minimum, maximum, and default cone angles are defined in Dsound.h as DS3D_MINCONEANGLE, DS3D_MAXCONEANGLE, and DS3D_DEFAULTCONEANGLE. Each angle must be in the range of 0 degrees (no cone) to 360 degrees (the full sphere). The default value is 360.
  Windows NT/2000: Requires Windows 2000.
  Windows 95/98: Requires Windows 95 or later. Available as a redistributable for Windows 95.
  Header: Declared in dsound.h.
  Import Library: Use dsound.lib.
IIDirectSound3DBuffer::GetConeOutsideVolume, IDirectSound3DBuffer::SetConeOutsideVolume