2002 Hyundai Elantra making a sound like a drum roll when idling. When accelerating, the sound of the acceleration seems a bit off, as if it's being played through a lame kazoo. There's also a cyclical noise coming from near the belts, but I'm not sure what's making it. Any ideas? (Video Included)

Car's got 160,000 miles on it. Any clues what that sound is? Inside the car, it's a low loud rumble. When you've got the hood open, the rumble is a little less noticable and you can just hear the hissing belts (or maybe something else?). What do you think? I don't mind the belt noise so much, but the rumble and the engine kazoo worries me a bit.

Video

I just changed the plugs this summer. Oil change a week ago. I posted a question about it a few days ago, but didn't have audio/video, so I went and got some.