Deafening Weapon Fusion
(from Starfinder Core Rulebook)
With the deafening fusion, a weapon releases a blast of low- frequency sonic energy on impact. The weapon gains the deafen critical hit effect. If the weapon already has a critical hit effect, when you score a critical hit, you can apply either the weapon’s normal critical hit effect or the deafen effect. Only weapons that deal bludgeoning, piercing, slashing, or sonic damage can benefit from a deafening fusion.