Just a thought, have any of you tried to turn the background music off? Not running that one audio stream constantly might just be enough to keep enough resources free to stop the sound effects from distorting.
Turning off the voice audio "fixes" the game for the most part. But their is no reason why this game should be so resource intensive and less reason why its only
Miriam's audio that seems to trigger the issue.
It's an Unreal Engine 4 game, and it uses some pretty high quality assets. If turning BGM off doesn't help, I'm not sure what else to try. I can't reproduce this on my end, so the advice I can offer is limited.
From my previous experience with my FX processor, the FX 6300 you have is supposed to be a six core processor, but it has issues. They're horribly ineffecient, especially when games or programs threads jump from core to core. Try setting your Thread Affinity for the game in Task Manager to Cores 0, 2, 4, and 5. This should keep the game from bunching up the game tasks on any given core. It's bee a while since I've used Windows 7, but if I remember right, you just right click on the game in Task Manager and you can set affinities in there.
Funnily enough, you've got the exact same motherboard I used to have.
If you've not updated your AMD chipset drivers, you might try doing that. https://www.amd.com/en/support/chipsets/amd-9-series-chipsets/970
You probably already have done that, but if not, that may be helpful, since the Microsoft inbox drivers aren't great.
Other than that, the game is certainly not behaving as it should. You're running at 900p with 8GB ram which should be more than fine. Given all the issues the game is having on every platform, I'm not too surprised it's got weird things happening running on lower-spec systems.
I hope some of that helps. It's a great game, if it, you know, decides to work properly.