I used to have this glitch, not sure how I fixed it though.
You could try (re)installing your headset/soundcard drivers
If you have your headset plugged into the backpanel of your pc or anyother place try plugging it somewhere else eg the front panel.
In audio settings in arma 3 there is an option called sound sources. Not sure of it's use but might be related.
Or maybe your headset/arma is just broken.
Hopefully this will help, if not good luck!