I have no idea what causes the special attack to be silent or muffled.
I made a bug report a number of days ago thinking it was having a dwarf in the group that caused this issue to happen somehow but it isnt, when loading up the game today it was happening in the keep.
This is the error code i got when kruber bot getting hooked crashed my game [Script Error]: …states/player_character_state_grabbed_by_pack_master.lua:309: attempt to compare nil with number.