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.