If belodion's advice doesn't work take a look at your owner's manual and see if there is a reset switch. If your tablet has one, it's usually a small pinhole where you'd take a paperclip or something similar and insert it into the hole to reset the device. Again consult your manual to see if your device has one and where it is located. I won't be responsible if you stick a paperclip into your microphone and damage it by mistake...