Metal Detector in a National Museum in DC?

I'm going on a field trip 5 hours away from home and I need to bring my cell. I have an iPhone 4. We have to go to the Newseum and we have to go through metal detectors so any help on how to go through without it going off?

You better make sure the museum is open first many national museuns in DC are closed due to
government shutdown
if open there should have problem it won't go off because you have cellphone