Sound Research

Bats in Cave
http://soundbible.com/1939-Bats-In-Cave.html

Crowd Applause
http://soundbible.com/1964-Small-Crowd-Applause.html

Drilling
http://soundbible.com/1108-Drilling.html

Dirt Bike Noise
http://soundbible.com/735-Dirt-Bikes-Racing.html

Fishtank Bubbles
http://soundbible.com/293-Fishtank-Bubbles.html