Ok, guys, I don't know if it is a bug or just me as a noob, but I have a bizarre behavior with my sound effects, so I decided to bring to 'how do' list assuming that is my mistake.
1) put the sound effects like the normal way in event sheet:
Player colides with Object: [sound name] > play > audio file + not looping + volume 0 + ""
2) testing preview with two Browsers: Firefox and Edge
2.2) after preview C2 game test, the Browsers STILL with no sound in another applications that have no relation with C2 (like Youtube, for example)
3) Export game to NW.js: the sound is ok, everything works fine.
4) Cleaning cache and history browisng solves the 'no sound' issue with Browsers.
Question: is that some C2 setting that I did not understand or this is some bizarre bug with sound system?