It might be just me, but recently I have been noticing more frequently that certain cars are "noisier". What I mean is that when the bogie passes by me I notice very distinct 'ka-ching ka-ching ka-ching' noise coming from that specific bogie or car end. Most cars pass by with 'wizzzz wizzzz' noise. I notice this in places with continuous rail, so it is not a break or thermal joint in the rail causing this noise. I am not familiar with maintenance practices on NJT, but is this sign of stuck break shoe? Flat wheel? Something else? Most of the time I have observed this with only one car out of a whole consist of 6 to 12 coaches. I have heard it on both Comets and Multi-levels. Multiple times it has been the head car. I have never observed it on the engine, but the engines are generally noisier, even the electric ones, so maybe it has been drowned out by the rest of the noise.