Sound distortion when using psychtoolbox back-end

[gbirot]

We noticed on two different MEG experiments that the sound is sometimes distorted. The issue is not systematic and occurs randomly. We usually have to restart the task solve the issue (at least momentarily). Both scripts use psychoolbox (PTB) to handle the sound. One is with the Matlab PTB and the other one with psychopy using PTB back-end. The issue never happened when we don't use PTB (e.g. e-prime, ExVR,...), therefore we are almost certain that the problem comes from PTB.

Since the issue happens randomly, it is very difficult to reproduce and to troubleshoot. We know that the MEG center at San Sebastian also have this issue using the same Matlab script as we use here. There are also online forums where a similar problem is reported but none gives a consistent way of solving the issue.

On our side, we are still troubleshooting the issue. We will update this post as soon as we have news.