How to tell someone it's break time in a high noise environment

Sign language. Hold your fists together out in front of you with your thumbs and index fingers touching, as if you were grabbing a stick. Quickly and simultaneously rotate your left fist counterclockwise ninety degrees and your right fist clockwise ninety degrees as if you were snapping the stick. Break time!

Yet another way you might intimate this is to make two thumbs-up signs, hold them in front of your eyes with your left thumb pointing to the left, and your right thumb to the right, and to touch the "meaty" parts of your hands together twice. This action looks almost as if you are crushing something between your fists or pulling a string grasped in your two hands. The gesture might also indicate to the other person that it's time to leave the noisy environment altogether, e.g., the 25-cent drink special in your favorite bar is over, and you're all out of quarters.

This piece of sign language originates from airfields, wherein the pilot of a small craft would use this gesture to communicate with the crew on the ground, since the crew obviously can't hear the pilot speak. With that gesture, the crew knew it's time to pull the chocks from the landing gear wheels so that the pilot can take off.

Scuba divers often use the following, one after the other:
-Tap the wrist in the area of the watch.
-Cock the wrist backwards in a pantomime of chugging a beer.
The resulting meaning: Its miller time.
This is, obviously, not a high-noise environment, but rather its opposite. Same principle, tho. :-)