Water Softener Making Squealing Noise During Brine/Slow Rinse

Hello,

I'm new to this and I had a question that I can't seem to find an answer to online. My water softener has two tanks and the primary one makes a loud squealing noise during the brine and slow rinse cycle. This started about a month ago and prior to that it worked fine. The noise occurs throughout the brine and slow rinse cycle. This leads me to believe it is not the air check valve being stuck open since it happens during the brine draw. Please help, the person who installed it came to check out the system and essentially told me that it happens and there isn't much that can be done.

Here is a link to show the problem:
http://www.youtube.com/watch?v=iA_mL9yJQsA&feature=youtu.be