Thundering Weapon Fusion
(from Starfinder Core Rulebook)
The thundering fusion imbues a weapon with heightened frequency vibrations. Half the weapon’s damage type is replaced with sonic damage. You can activate or deactivate the thundering fusion as a swift action. If the weapon already deals two types of damage, replace one of them with sonic (you decide which damage type to replace each time you activate the thundering fusion). You can add this fusion only to a weapon that does not already deal sonic damage. This fusion never causes a weapon that normally target KAC to target EAC.