I looked and looked and can find very little about the ZS10.
It is a fairly new model and that is some of the problem finding information.
It is also an entry level camera (under $100) and none of the big review websites will review entry level cameras.
I suspect the buzz noise you hear may be inherent because a $100 camera probably has a 25 cent microphone.
The only way to find out, is to get your hands on another camera of the same model and see if it gives the same result.
But I suggest you start with Casio.
Your camera is probably still under warranty with Casio.
Call their service department and ask for help.
The video recording of my Casio Exilim EX-ZS10 is good except for the sound. There's very loud buzzing noise. What can I do to remove it? The sound of the scene I was recording was not very loud. I didn't do any special setup. The loud buzz is heard at playback on either the camera or laptop. Thanks for help.