We live close to the train tracks about ~150-200 feet away. Luckily the freight train comes very infrequently...maybe once or twice a day.
When the train rolls by, we'll hear noise from the engine (more high frequencies...such as screeching), and once the engine passes, we'll hear low rumbling (low frequencies) from all the train cars that the engine is pulling.
My question is, how do I minimize what I hear inside the house? What is the least intrusive way to solve this. What I mean is that I can't start knocking down walls or tearing up floors to add sound proofing materials.
This post touches on this issue a bit but there weren't that many solutions.