Clock mismatch between player and recorder

Exponential sine sweeps (promoted by A. Farina) is a very nice technique to measure loudspeakers response with a good rejection of noises. But it may have problems when the player or recorder clock are unlocked (ie when you record on a computer that is independant of the player). In this case, the displayed impulse and step responses, spectrograms, wavelets,… may be distorded (don’t worry, the MMM part and so frequency response and correction are not affected). To avoid those problems, we have added in LA2v3 version, another time sync signal at the end of the audio sequence to automatically compensate for clock mismatch. The value of drifted samples is indicated in page p0. If mismatch is less than 200ppm (CD Redbook specifications is 100ppm), the recording is resampled. This corresponds to about +-1600 samples for the stereo file. If mismatch is higher than 200ppm, this is not considered as a clock difference but as a recording problem (ie usb dropouts,…) and so the recording is not resampled.