http://imgur.com/WKpnWt8
By default I don't have the acid launcher effects playing, only hearing the incorrect sounds. It looks like your reporter had a mod?
Where is this string being pulled from the command? I believe that this is the actual issue.
animation = "fire_lightning_rifle_single_1",
Side notes about what I seen/think so far.
*The lightning cannon shares the same 'weaponEffect' as the other heavy weapons. I did change it client side to be it's own with no change to the sound.
*I'm thinking that the command string is mixing up what sound to pull, not the client... But I wouldn't know since I cannot find where the string is being used again.