int meanoverduration(struct Sum * oldsum) {
oldsum->mean = pow(oldsum->sum / ((double) oldsum->nsamples), 0.500);
oldsum->cmean = pow(oldsum->csum / ((double) oldsum->nsamples), 0.500);
- oldsum->rms = 20*log10(oldsum->mean) + 108.0851;
- oldsum->leqm = 20*log10(oldsum->cmean) + 108.0851;//
- //This must be right because M filter is -5.6 @ 1k Hz that is -25.6 dBFS and to have 85.0 as reference level we must add 25.56 + 85.00 that is 110.6 dB.
- //this value is obtained calibrating with a -20 dBFS.
-
+ oldsum->rms = 20*log10(oldsum->mean) + 108.010299957;
+ oldsum->leqm = 20*log10(oldsum->cmean) + 108.010299957;//
+
+ /*
+How the final offset is calculated without reference to a test tone:
+P0 is the SPL reference 20 uPa
+Reference SPL is RMS ! So 85 SPL over 20 uPa is 10^4.25 x 0.000020 = 0.355655882 Pa (RMS),
+but Peak value is 0.355655882 x sqr(2) = 0.502973372 that is 20 x log ( 0.502973372 / 0.000020) = 88.010299957
+To that one has to add the 20 dB offset of the reference -20dBFS: 88.010299957 + 20.00 = 108.010299957
+ */
+ /*But ISO 21727:2004(E) ask for a reference level "measured using an average responding meter". So reference level is not 0.707, but 0.637 = 2/pi
+ */
return 0;
}
}
void logleqm10(FILE * filehandle, double featuretimesec, double longaverage) {
- double leqm10 = 20*log10(pow(longaverage, 0.500)) + 108.0851;
+ double leqm10 = 20*log10(pow(longaverage, 0.500)) + 108.010299957;
fprintf(filehandle, "%.4f", featuretimesec);
fprintf(filehandle, "\t");
fprintf(filehandle, "%.4f\n", leqm10);