The voice audio for any callouts by NSO characters are extremely quiet. Calling out to allies for things like ammo or healing rarely gets heard, and the few times it does might just be because of the minimap icons. I can't remember the last time I heard an NSO callout by another player. This makes it harder for NSO to coordinate with other players while simultaneously allowing NSO infiltrators to spot enemies with much smaller risk of being heard and found. It's a very frustrating experience to yell at the top of your lungs for a medic in a room full of allies, but your voice gets drowned out by most sounds in the game. I have already turned up character voice volume to double of all the other audio sources and can hear my own characters voice a bit better now, but other players are still oblivious.
