Bluetooth phone quality is bad

Hi everyone,
Just got a 2013 Frontier and am enjoying it quite a bit. It has about 38,000 miles on it, but compared to the '99 Ranger I had with 240,000 miles, that's practically new!

Anyway, I've only noticed a couple things so far...one being a high-pitched steady squeal from the serpentine belt. I think I need to replace it, and have found discussion on the tensioner pulley maybe being a problem, too. I thought that issue was resolved around 2009 or so.

The other issue I've found is the Bluetooth mic quality. I've been somewhat spoiled with my other cars having hands-free and I was a little disappointed to hear that people I'm talking to hear a LOT of background noise. I've left myself voicemails to listen for myself, and it is pretty bad.

I've done a couple things to try and make it better, though, one of which is to stuff green high density foam (seat foam) around the plastic area where the mic is located. This has helped a bit, but not completely. I made a couple calls with the plastic cover both on and off (over the mic) and found that the quality greatly improves with the cover removed. I ended up drilling the cover hole much wider to about 1/2 inch and now the quality is the same as when the cover is removed.

I pulled the mic out of it's mounting hole and looked up the part number...those things run about $50 at the cheapest, but I'm not convinced the mic is bad. Really seems to get a lot of ambient noise. I thought maybe the noise canceling circuitry is bad...but not sure.

Anyone have any ideas to fix the noise issue? I was hoping the Radio (AV system without Nav) would have a menu item for mic sensitivity, but it doesn't.

Thanks!