Issue with audio on recieving end of Facetime

Not sure what's changed, but recently when trying to Facetime via the built in camera/mic of the TB display, my wife is hearing a lot of static on her end of the call on several occasions. I don't hear anything like that on my end, although I do have to turn up the volume quite a bit.

I do have external speakers hooked up to my MBP and I've verified and re-verified that I have the proper input setting in preferences.

I ended up having my wife call back and picked it up on my iPhone 6s+ and we had no issues at all so I don't think it had anything to do with the line. I'm a bit confused as to what it might be causing this to be honest. I am running El Capitan and my MBP recently had the logic board replaced due to graphics card failure.

Any ideas?? Display issue, MBP issue, or OS??