The Bachmann Acela set description includes DCC features listed, but not sound. Does it have sound? If not, how can it be added?
No it doesn't have sound, and in real life the sound of the power is not really audible, so you really would not need anything but a horn and bell. On top of that no one makes sound for the acela for that reason.
Well, the Acela itself doesn't make much noise. What you do hear is wheel noise and some wind noise as it flashes by. That's a much more subtle thing than steam or diesel which do generate a lot of their own noise.