go into editor, place a unmaned marshal (nato armored) an place a civilian with zeus being set as player about 300m away (either set to go moe or behin a tank as cover). now using zeus place a nato grenaier besides the marshal, take control of him an shoot a grnae at the civilian, an quickly switch back before it lans to hear it land.
now mount in the marshal, put own a csat soldier somewhere an while howering close to him in zeus tell the marshal to engage him.
Now compare the 2 sounds.
-40mm grenade with about 80m/s, not very much of a woosh.
-40mm cannon shell, with about 10 times as much speed, still no woosh or auible punch behind it as far as speed goes.