Function DBtoLIN

extlibs/soloud/src/audiosource/speech/klatt.cpp:198–247

Convert from decibels to a linear scale factor */

/* Convert from decibels to a linear scale factor */
static float DBtoLIN(int dB)
{
	/*
	* Convertion table, db to linear, 87 dB --> 32767
	*                                 86 dB --> 29491 (1 dB down = 0.5**1/6)
	*                                 ...
	*                                 81 dB --> 16384 (6 dB down = 0.5)
	*                                 ...
	*                                  0 dB -->     0
	*
	* The just noticeable difference for a change in intensity of a vowel
	*   is approximately 1 dB.  Thus all amplitudes are quantized to 1 dB
	*   steps.
	*/

	static const float amptable[88] =
	{
		0.0, 0.0, 0.0, 0.0, 0.0,
		0.0, 0.0, 0.0, 0.0, 0.0,
		0.0, 0.0, 0.0, 6.0, 7.0,
		8.0, 9.0, 10.0, 11.0, 13.0,
		14.0, 16.0, 18.0, 20.0, 22.0,
		25.0, 28.0, 32.0, 35.0, 40.0,
		45.0, 51.0, 57.0, 64.0, 71.0,
		80.0, 90.0, 101.0, 114.0, 128.0,
		142.0, 159.0, 179.0, 202.0, 227.0,
		256.0, 284.0, 318.0, 359.0, 405.0,
		455.0, 512.0, 568.0, 638.0, 719.0,
		811.0, 911.0, 1024.0, 1137.0, 1276.0,
		1438.0, 1622.0, 1823.0, 2048.0, 2273.0,
		2552.0, 2875.0, 3244.0, 3645.0, 4096.0,
		4547.0, 5104.0, 5751.0, 6488.0, 7291.0,
		8192.0, 9093.0, 10207.0, 11502.0, 12976.0,
		14582.0, 16384.0, 18350.0, 20644.0, 23429.0,
		26214.0, 29491.0, 32767.0
	};

	// Check limits or argument (can be removed in final product)
	if (dB < 0)
	{
		dB = 0;
	}
	else
	if (dB >= 88)
	{
		dB = 87;
	}

	return amptable[dB] * 0.001f;
}