There may be other options, but you can buy battery operated recordable sound modules with push button playback through a small speaker, but you would need to buy one for each station/area that you intend to use it for.
I have several mounted underneath my layout at various locations and play the sounds (gas station, industrial sounds, farm animals, etc. ) as I show the layout to guests and visitors.
They are available on the big A and probably other sites as well.
