>>33
When mine are going off, they're audible.

That aside, I think the easiest way to find out if a guy likes you is to find an excuse to touch him. Find a way to "accidentally" touch his arm. If he doesn't move away, or if he moves away only as a reflex and then accepts it, then he likes you. If at the same time his pupils dilate to the size of marbles, then he likes you a lot.

The pupils are probably better since it's harder to fake it or prevent it.