There’s several topics on this dating back to KI releasing on PC: When playing as Jago, there is an intermittent sound effect tied to particular moves that is an extremely high-pitched split-second chirp. The chirp is very loud, audible, and painful to the ears on any of my normal audio devices. (Sennheiser RS175 headphones, Polk MagniFi Mini speaker) So much so to the point where I have to stop playing with Jago, lest my ears bleed.
It seems to be mostly at the start of the match, combo breakers, and shadow attacks. From all the various links I could provide on the issue, it seems that this is a cue for a Jago Sound Link action figure: