[Closed] HTC One Microphone fault

Anyone had this?
the microphone went really quiet, I had to shout to make myself heard.

Lots of people on the internet with the same problem, lots of nonsense being spouted but no real answers. Tried it out of the case, tried clearing the tiny holes in the back with a pin etc etc.

Eventually sent it back for repair where surprise surprise, no fault found.

I'm assuming at the moment that it's a software fault because I wiped it before sending it back and presume they've now put an OS back on it.