Have you try to change which sound is called from here
Divinity - Original Sin\Data\Public\Main\Assets\Sound
Game_Basic.txt

3801417 Steps_Base_Sneakers_Grass_Walk_L05 C:\Develop\ART_ASSETS\EyesOfAChild\Main\Data\Public\Main\Assets\Sound\.cache\Windows\sfx\steps_base_sneakers_grass_walk_l05_32f820ce.wem \Actor-Mixer Hierarchy\Default Work Unit\WET\Movement\Steps\Steps_RatKing_Run\Steps_Animals_Soft\NPCfemSteps_Walk_Grass\NPCfemSteps_Walk_GrassL\Steps_Base_Sneakers_Grass_Walk_L05 11505

Weapons.txt
Event ID Name Wwise Object Path Notes
225874300 Weapon_Crossbow_Insert \Default Work Unit\WEAPONS\Weapon_Crossbow_Insert

you most likely need to first dismantle .wems and figure out where those sound assents then are.