Every time a character speaks during a cutscene there is a “click” sound when they finish speaking. Very noticable during cutscenes where there isn’t much other sound.
EDIT: I should add that this is on the Halo MCC PC Flight Three.
If you haven’t already, please check the known issues list on the support site in case this is a bug that the devs are aware of.
If it isn’t, submit a ticket detailing the issue - this is the best way to bring it to their attention.