Sound in Bacmann F7 a/b

[Crofthead]

I have these units which are dcc only and would like to put in sound.
Any recommendations?
Even if it meant changing the whole decoder for one with sound, no problem, (but where the speaker would go?).
I also thought about stripping the motor and chip out of the B unit to use for the speakers and permanently join them together.
if that is the case, which decoder should I go for?

[Maletrain]

Rather than strip a powered unit of its motor, why not start with a dummy B unit?  Or even with a box car that you will leave attached the diesel units all of the time? 

And, of course, there is another manufacturer who now sells F-7 A and B units that come with DCC and sound.  Just getting a B unit from them would work, too.  But, you would probably need to do some speed matching in the DCC speed table to run their B with the Bachmann units.

[Crofthead]

Thanks.
I really do not wish to strip out a pefectly working DCC decoder. I quite like the idea of a box car permanently attached.
Pleas forgive if my english seems a bit odd. I live in Scorland, UK

[rich1998]

Look at the SoundTraxx decoder selector for Bachmann N scale locos. Bachmann has use SoundTraxx for a few years for sound.

http://www.soundtraxx.com/choose/step1.php?s=N-Bachmann

Rich

[Crofthead]

Thanks, Ill do that