When you are underground and have a lot of underground rail near each other, the sound can be heard from miles away if you're looking in the right direction.

I recently created another bug report involving the fact that you cannot hear the sound very well if you're not looking directly at the object making the sound - this is the complete opposite. If you're looking in the correct direction - right at it, even if you are 30 or 40 blocks away from the source of the sound, it is still full blast - as if it's right next to you.

This isn't gamebreaking however it's annoying, especially for someone like me who has a lot of underground subway.