Squealing front passenger side

We have a 2005 honda civic hybrid; there is a squealing noise coming from front passenger side, when breaking, when accelerating, decelerating, but not while driving at speeds of 30 mph, straight. Also when backing up, turning wheels. Any suggestions? It’s going to the mechanic on monday for regular maintenance, 100K miles, etc. Thank you!

Have the brakes checked for worn brake pads.

How about a bad tensioner on the serpentine belt?

Put a sock in his mouth.