Autorotations are not exactly quiet. The CH-53 sounds like a Stuka dive bomber (at least from inside the cockpit) during the first part of an autorotation. Then the big roar comes in when you pull pitch at the bottom. Sounds kinda like a C-130 reversing props on a short field landing.
If you can hit an LZ power on, you also should be able to in a planned autorotation. My guess is that the first bird into the LZ did not land far enough forward, leaving too little room for Dash 2. Wiser to hang your tail over the wall than to hit your ride out (the first bird) with your rotor blades.
Just a guess.
Then the big roar comes in when you pull pitch at the bottom.
I have never been through one. I can imagine this to be true but I would think is all quieter than engines running.