Hello, my name is Rusty. Do you have the camera with you?
Ok, no problem, I'll tell you how to fix it. I'm a sound engineer, and that really helps me at this desk job... AGC is automatic gain control. It's not the mic causing the noise, but you are correct, it's "desperate to record sound." It's raising the gain to pick up sound when there is none, and you're hearing the hiss that is caused by that.
Go to your menu, camera/mic menu, manual settings, and that is where you will find the AGC Limit setting. It looks like 24 is actually -24, which is the one you want to use. It turns off the AGC. 0 should be full volume, and causes the sound. These are engineering levels, not all manufacturers use them, so it may be backwards depending on how they built the camera.
That should clear up your problem and give you audio with dynamics. If you find he's quiet at times, find a place in the middle between 24 and 0, and it will use partial AGC, instead of full AGC.
When we are finished, please don't forget to rate my service with you today with 3-5 stars so I can get credit for helping you. Rating does not close the question, and you can communicate with me at no extra charge.
Click here, and refer to the bottom of page 103. AGC is what causes the room noise to get louder. Its technical term is a compressor. AGC is an automatic compressor that keeps the gain at a steady level, which causes significant room noise when silent.
No problem Jan, those are automated emails sent from the site, not myself. Keep one of them so you can get back here when you get to your camera. I'm confident that the AGC is what is causing the problem. I have racks of equipment used for that purpose. The fact that your camera only has one setting for the AGC, makes it easy to adjust.
There is also an AGC for the video, it's what gives the brightness of the video. You want the one with the setting between 24 and 0.