Thanks a lot Kju.
I found a definition that works, taken from BIS missions:
class a1
{
name = "a1";
sound[] = {\sound\a1.ogg, db + 10, 1.05, 500};
titles[] = {0, ""};
};
In my case "500" is the number of meters from the soundsource where you will NOT hear the sound.
Within 500 meters you will hear it, and it will get louder once you get closer.
This new third parameter seems to overwrite the db setting, making it obsolete in a way, but I'm not sure.
Laggy