If yes - it is common problem in some versions of hero2.
You can change (upgrade or downgrade) firmware - there is no specified version that is works, you have to try.
Then you should do not connect any external microphone (because camera will lock again on external mic).
Some versions of hero2 works good on latest firmware (you can use external or internal mic), but some also locks at external mic.
-
No known workaround for this issue.
+
No known workaround for this issue.
+
+
=== Update (10/27/2015) ===
+
+
Also it is possible that mic cable is broken - you can simply fix it as shown in this tutorial (speaker replacement), but by mistake someone called it speaker while it is internal mic :)
+
+
Also mic can be broken, so you need to buy new one.
Did you plugged external mic into your camera?
If yes - it is common problem in some versions of hero2.
You can change (upgrade or downgrade) firmware - there is no specified version that is works, you have to try.
Then you should do not connect any external microphone (because camera will lock again on external mic).
Some versions of hero2 works good on latest firmware (you can use external or internal mic), but some also locks at external mic.
No known workaround for this issue.