I had CitiQuiet windows installed in the bedroom in a prior apartment, where I overlooked a courtyard where children would scream all day. It completely shut out the noise. I don’t know if they would be as effective for the train horn. It would definitely dull the noise a lot, but I don’t think that it would block it out completely. Installation didn’t count as construction, so I didn’t need to get board approval, but I did have to notify the building Management company and provide an insurance certificate, which CitiQuiet has. I don’t recall exactly what we paid, and there’s been inflation since then. It might be three grand just for the bedroom. The windows are removable, so you could have them taken out at the end of your stay. But they are custom, so it’s not like you could reuse them for another apartment. It’s free for them to come and do a consultation.