None of the previous posts indicate HOW noisy. I have separate two rail and three rail layouts on the same tables. The 3 rail uses Atlas track, and the two rail uses MicroScale Engineering track. I measured the noise level of the same size freight train on each track. The difference was 3dB. This doesn't sound like much of a difference, but since dB is measured using a log scale,, every 3dB is about twice the noise energy, but NOT double the sound intensity to a human ear. The 3 rail sounds like a bucket of bolts when compared with 2 rail. I think that the wider wheel treads, much larger flanges, and engine pickup rollers are the culprits.
On a 2 rail train, the train is quieter, the cars couple much closer together and look more prototypical. If someone (anyone?) would offer a three rail turnout (I use Atlas) that can accommodate two rail equipment, I would standardize on only two rail cars for both layouts. As info, I also ran the same size 2 rail freight train on my 3 rail layout, and it was over 2 dB quieter, and indication to me that the 3 rail sintered iron wheelsets originate most of the noise, with the engine's pickup rollers adding the rest...
