What are noise sensors for?

[paintballphreak]

I bought a new liquid cooling system, and I see that a lot of systems come with a "noise sensor" that you tape to the underside of one of the cooling blocks. what purpose do these serve?

[bluflame]

To kill it if it's hissing because of a leak?
I have no clue, personally.
I've never been fond of liquid cooling, myself.