Voice Line Glitch

Hi, so I opened overwatch, and choose reinhardt. I select a voiceline whilst in spawn and it seems to be super quiet. as though the voiceline glitched and I hear an echo. Unplugging my headphones my speakers are fine and play it as it should be, yet this issue is consistent across all heroes, even after restarting the game. I know this is a QoL bug, but any tips on resolving it?

Assume the hero voice line volume option hasn’t randomly been turned down for some reason??

No, but it gets more bizzare. So its connected to my mic port. Basically I have a jack splitter so my headphones (1 jack) can be split into the input and output jack of my PC. Plugging my headphones into the headphone jack without the splitter fixes it. yet even weirder plugging it into the splitter and into both the mic and headphone jack it fixes the issue. Bear in mind I have used the splitter more as an extension cord. as I have a proper mic connected to the splitte?