Maybe a different username would help get a response..... Just kidding 

politician wrote:

Hello! I'm hoping somebody might be able to help me diagnose and remedy a fault with one of my Lab 5s. Since Saturday night, the left-hand speaker has been produced an annoying high-pitched whistle (almost like a bicycle that needs oiling) whenever it's switched on. The sound is coming from the calibration microphone in the base rather than the speaker itself. Attempts to recalibrate have produced a series of awful grinding noises rather than the usual sounds, and the sequence never completes. Unplugging and replugging the speaker has made no difference whatsoever. Does anyone have any idea what is going on?

Does the microphone come out for measuring the usual way? If not, it might be a mechanical problem.

Yes, the microphone extends normally when I attempt to recalibrate, so it is not a mechanical issue. Could it be some kind of software fault? Also, is it possible to switch off the microphone in some way? That would resolve the problem instantly, as the speaker is playing perfectly normally.

Fantastic. Thanks!