Did you configure CoolCV to run from Emulation Station? If so, did you get sound from it? If you have not tried it from ES, would you?
I do not know why you would not get sound from the command line. I have not tried Retropie 3.x yet.

No sound when I try to run coolcv_pi from within Emulation station. This is probably because ES is simply a frontend. However, ES runs emulators via a script that probably activates audio the proper way. Because when I run mame4all from within ES it does have sound (of course) but from the commandline it doesn’t. Think I’ll start a new topic on sound.

[edit] Sound issues from command line solved. See this topic. however, only ColEm still has no sound… Which is a pity because coolcv_pi runs too slow but ColEm can be tweaked to run faster.