Train horns and rolling stock

I live approximately 1/2 of a mile north, as the crow flies, from the CSX main here in upstate NY. Some days/nights the trains go by and the overall sound is very faint as if the railroad is nowhere close to me. Then there are other days/nights where the sound of the horns is very loud and the locomotives rumbling through town sound like thunder. The trailing freight is loud too. Are some trains just more noisy than others or does this have something to do with the air?

This is one of those lifelong questions I have thought about off and on over the many years and would finally like to put it to rest once and for all with the help of you. Thanks.

The answer to your question is "Yes, all of the above." Air density, humidity, wind direction, other noises (i.e., noise pollution) and noise of the train all play factors on how well you can hear the train off in the distance. On a hot, humid day, the noises will be muffled. On a clear, crisp, quiet night (3:00 a.m.) you can hear a truck going down the highway two miles away. Some trains are indeed noisier than others - an empty autorack train going at speed will sound like a trash compactor, but a loaded coal train will be deeper, heavier sounding.

It's either all of the preceding, or maybe your hearing's going and you need some medical care. Personally - I'd go with the former, not the latter.