Hello ChaddLind, since you are new here first of all welcome to the asylum.
And regarding your question, given the fact that this website is primarily for and by collectors of the physical media (DVD, Blu-ray, and Ultra HD Blu-ray), questions regarding MKV container files are not of our daily concern.
These kinds of questions are more suited by the likes of sites as
videohelp.com.
However, since you are asking here and I don't want to be THAT guy, your question does raise even more questions, like DustyFlow already addressed, such as:
1. What is the nature of the MKV (codecs used for audio)?
2. What kind of playback device do you use (PC, Mac (which is
also a PC but alas), NMT, HTPC, etc.)?
3. OS plus version used at the playback device (incl. possible hotfixes).
4. Which player (brand, type, and/or version) are you using?
5. Does this issue happen with all or only some MKV files?
6. What kind of output device are you using? (TV, Receiver, Soundbar, etc.)
7. Did this issue always happen in the past or just recently?
8. Does this issue also happen on other devices?
9. The list of questions does not even end here, but I think I have mentioned the important ones by now.
And finally, I hope this post is not some form of spam and indeed a genuine question of a fellow movie enthusiast.