@Paul K. not to beat up on you, but next time look at Google Maps, both aerial and street view. Do that before you ever send boots on the ground to the property. Look for proximity to things like train tracks, but also major highways, industrial areas, etc.
The train tracks were there before you owned the house. The city or train operator is under no obligation to accommodate your noise concerns. Cars getting hit on train tracks is a far greater concern than noise. Also be aware that even if tracks are quiet today, they can get busy in the future. I have seen tracks go from one train a day to one coal train every four hours. Coal trains create noise and nasty dust, so just be aware it could be worse. Nothing you can do about the trains, so deal with mitigation.
The curtains may help, but really window replacement is your best bet. My parents live on a busy street and had 1950's era single pain glass windows. They upgraded to new double pain glass windows and the noise disappeared.
Whatever route you choose to rent the property, deal with the noise problem upfront. In your property listing, be very specific about the noise. Put a clause in your lease that the tenants must initial, accepting the noise. Do not hide the noise issue.
As others suggested, consider renting to more challenging tenants. That could be low credit score, felon friendly or accept dangerous dog breeds. Someone with a problem you are willing to look past is willing to look past your noise problem.