Thanks for the reply.  The engines I have are:
Spectrum 4-4-0 Steam
GE 45ton switcher
GE 70 ton switcher
2-8-0 Consolidated steam
Gas/Elect Doodlebug
GP 40 Diesel
FT-A Diesel
Saddleback 0-6-0 Switcher

Hope this provides the info you need.  I would be more inclined to add sound to the steamers but would love to have it on the doodlebug and the switchers also if possible.  What would be the source of these sound units?
Thanks again,
Joe

I am currently setting up a new layout and have bought all Bachmann engines with DCC.  Unfortunately, that DCC is for control of motion and lighting but not sound.  I am looking for a sound add on so I don't have to loose my investment in the DCC.  If these are not available, then can someone suggest a unit that connects to the 8 pin plug in the engine and provides full control including sound?  I will even consider a change out of the DCC if nothing else is available.  Thanks for your help.