function CalcFreqFactor(Freq: Double; SampleRate: Double; PData: PSmallInt; SampleCount: Longint): Double;
var  i          :	Longint;
     fSin, fCos :	Extended;
     fSinSum    : Double;
     fCosSum    : Double;
     d          : Double;
begin
     fSinSum  := 0.0;
     fCosSum  := 0.0;
     d        := 2 * Pi * Freq / SampleRate;
     for i := 0 to SampleCount - 1 do
     begin
          SinCos(d * i, fSin, fCos);
          fSinSum := fSinSum + pData^ * fSin;
          fCosSum := fCosSum + pData^ * fCos;
          Inc(pData);
     end;
     Result:= (abs(fSinSum) + abs(fCosSum)) / SampleCount;
end;