Ha I think mine has that noise because I fly with the gopro case on. The props are pretty well balanced and there's only sometimes just a hint of jello so I think vibrations are good. At higher throttle it goes away so I'm assuming my combination of props, rpm, gopro case causes some kind of resonance. Bearings are pretty new too.
Here are some edited ones with music - part of our family vacation.
Hmmf. Honestly then I really don't know. As you can see by the video, there really isn't that much vibration. I started with a wood frame then the DJI and now the flip and they've all made that noise in the video. The one thing I did move from one quad to the last are the motors. The HK 'hacker style' 1050kv motors. However they are basically the same motors that are offered in lots of kits. I have recently replaced all the bearings too with Align/abec bearings. If you listen to the part where it flies overhead you can hear it sounds pretty smooth from the outside as well. I'm OK with the noise it flies perfectly fine (50 flights?) without fail.
I use a layer of gel tape on top and on bottom of the front tab so the camera mounting hardware doesn't touch any part of the frame. Could be that.
I know Grand Canyon has a restriction that is spelled out. I didn't see one for Yellowstone. But if you don't want to ruin it for anyone else, be smart about it. Notice I didn't fly at crowded places like Old Faithful or anything. I didn't go above a bunch of cars or people - maybe a little alongSIDE the road and only over myself and my group. There was one time where people showed up AFTER I had taken off and I had my friends and family clear my landing spot so there was no danger. Just use common sense. Don't do anything you are pretty sure will get rangers or other visitors upset. Otherwise enjoy the scenery and capture some footage that would otherwise be impossible!