var
   FDSCB           :iDirectSoundCaptureBuffer;
   FDSC            :IDirectSoundCapture8;
   FDSCBDesc       :TDSCBUFFERDESC;
begin
...
 FResult:=DirectSoundCaptureCreate8(FGUID,FDSC,nil);
 if FResult<>DS_OK then
 Begin
 ...
 end;

 ZeroMemory(@dsEffect[0],sizeof(TDSCEffectDesc));
 dsEffect[0].dwSize := sizeof(TDSCEffectDesc);
 dsEffect[0].dwFlags := DSCFX_LOCSOFTWARE; //DSCFX_LOCHARDWARE
 dsEffect[0].guidDSCFXClass := GUID_DSCFX_CLASS_AEC;
 dsEffect[0].guidDSCFXInstance:=GUID_DSCFX_SYSTEM_AEC;
 dsEffect[0].dwReserved1:=0;
 dsEffect[0].dwReserved2:=0;

 ZeroMemory(@dsEffect[1],sizeof(TDSCEffectDesc));
 dsEffect[1].dwSize := sizeof(TDSCEffectDesc);
 dsEffect[1].dwFlags := DSCFX_LOCSOFTWARE; //DSCFX_LOCHARDWARE
 dsEffect[1].guidDSCFXClass := GUID_DSCFX_CLASS_NS;
 dsEffect[1].guidDSCFXInstance:=GUID_DSCFX_SYSTEM_NS;
 dsEffect[1].dwReserved1:=0;
 dsEffect[1].dwReserved2:=0;

 with FDSCBDesc do
 Begin
   dwSize:=sizeof(TDSCBUFFERDESC);
   dwFlags:=DSCBCAPS_CTRLFX;
   dwBufferBytes:=notifysize*notifycount;
   lpwfxFormat:=FFormat;
   dwFXCount:=2;
   dwReserved:=0;
   lpDSCFXDesc:=@dsEffect;
 End;

 FResult:=FDSC.CreateCaptureBuffer(FDSCBDesc,FDSCB,nil);
 if FResult<>DS_OK then
 Begin
   //тут сообщается об ошибке, что выше.
 end;