It sounds like someone's walkie talkie more than a police frequency.
Same thing on departure 135.900, you get the beeping which sounds like some sort of internal radio function (priority beep ?), and then I've heard what sounds like some guys doing maintenance on a golf course. DJ
I'm listening to JFK Departure and it's doing it again. CAMRN and ROBER were doing something similar this morning as well. Sounds just as you say, a priority beep and some sort of walkie-talkie or HAM frequency mixing in with the chatter of "New York Departure."