Weirdest thing I had happen was during one of my first hunts as an adult. I got back into hunting at around 26, after my uncle had given me a bow for helping re-roof my grandmas garage.
We takes me out to this piece of public he's had lots of success on, and I climb a tree using my climbing stand. I get situated well before dark and the waiting game begins. About an hour after sun up, the biggest flock of crows/blackbirds/ravens I've ever seen starts flying around and cawing. It's so loud I wouldn't have been able to hear anything approaching. This goes on for about an hour and as fast as it started, it just abruptly stops.
A couple hours later, I start to hear the "moo" of cows. Just like the birds, it builds until it's this deafening nonstop mooing, and lasts about an hour before just abruptly stopping.
A couple hours after that, the sound of machinery starts up. Like huge equipment banging and hammering, and I could feel the ground shaking a little. It's deafening, like I'm working on a construction site. This goes on for about an hour before abruptly stopping.
Eventually, I climb down without having seen anything all day, and my uncle walks up the trail to me. I ask him if he heard all these sounds like I did, and if this is normal when he hunts there. He said he heard it too and have never heard anything like it in all the years hunting there. It was just weird how each noise came in waves, and started and stopped suddenly. I've hunted there a lot since, and have never heard anything like that again.