Go to Google play and Train Horns and sounds, a white app with cross bucks will come up. That works ok.
For 2.99 you can get Railroad companion by Papdigm NOrth Multimedia Group. That paid one is much better, you do a lot more with it and has better sounds. I just downloaded that a couple minutes ag0. If you have apple you could look in your apps too.
See what they have. The nice thing is with android I can put this on my tablets also because it is in my library now.
I hooked up my bluetooth speaker and stuck it behind a false front building and i Had it turned up so loud I thought my engine would come off the track. Sounds nice and would be fun for the kids to do. They have steam and diesel on both, but the paid has better sounds for sure.
I definitely would go with the paid app.
Good luck and Happy Tootin---Bill