Sound Dampening When Voice Comm Active

Hey guys, I must be missing something here because I can't find the option to dampen in-game volume when someone is speaking over voice chat. This makes hearing people during arty strikes pretty much impossible. I'm pretty sure I remember the feature in RO1 and RO2, so I must just be blind here.

Can someone tell me where this option is? I don't see it in audio settings.

Thanks.

Sound Dampening When Voice Comm Active