Since the latest update, all co-op players and my own character sounds have been replaced by tiger/ sabretooth sounds that all players hear.
Actions like attacking, moving/ sprinting, taking damage, and any emotes with sound or voicelines are now replaced by these Cat sounds (roars, growls, etc.)
both myself and my co-op partner are affected, both of our actions make the sound fx and we both hear the other persons cat fx.