I have not done anything, not swimming, not any other unusual activity. Every time the mic get suspended, if i reboot the watch it works again for 30-40 min, and get suspended. However, like i mention, if i remove Noise app from face, it is never suspended, running in background. Start thinking it is mic problem with the watch.
P.S. installed beta 8.4, and if i put it back to face, it gets suspended very quickly (myabe 10-15 min), but that resume itself for short period of time and get suspended again for good, that require restart.