Pretty sure the guy on the public address says, "please stand and remove your hats." I think all of this removing your hat stuff comes from distinguishing civilian from military. Military, in uniform with "caps" on are to salute when the national anthem is played. Might be old fashioned and more of a ceremonial thing than practical today. but that's my interpretation as a veteran. In my opinion, its waaayyyy more disrespectful to talk and socialize during the anthem, which happens a lot, than to not remove your hat.