Living in LA, the LAPD helicopter noise really is incessant.
It's hilarious to hear flying cops try to be intimidating through when dispersing illegal concerts or singling individuals out in non-violent crowds. It's impotent posturing and an obvious waste of money. They really don't need to send 5 squad cars and a helicopter for noise complaints.
I will say though that the loudspeaker on those things are surprisingly clear, even through the buzzing of a helicopter.