From the Beta Forum
Q: Can you actually make a puppet’s mouth move by speaking into a microphone?
If you have a movable jaw on your puppet you can create a key frame of the puppet opening its mouth.
You can then wire the envolope output of a sound into that keyframe.The envelope output is on the outputs tab on a sound (second to last tab)
This works with any sound but it sounds like you want to record your own voice which can be done using the Sound recorder gadget. To find this go to the create menu > Modes > Sound Mode > Tools > Sound Recorder. you should see a red record button when you select the sound recorder but it wont start recording until you start speaking 🙂