there are some Breville Blender troubleshooting tips here
. Tied in with that, a high pitched noise could come in from a few directions:
Some blenders will use reduction gears to get more torque and power out of a high RPM, lower power motor. If this is the case, the whine could be from the motor, though if you hadn't noticed before, that would not be reassuring.
Per the troubleshooting, check that the blade is firmly attached, and that the coupling from jug to base is firm. If there are gaps or loos spots, there can be buzzing or whining between sort-of-spinning parts and shafts or bolt threads.
Check the motor base for dried spilled-on margarita mix or marinara sauce or what have you. they try to seal this pretty tight in a blender, but it has to spin, so food spills can get in the gap and cause friction and resistance, which can in turn cause whining noises from parts not expecting the load. If you do any cleaning or poking there, make sure you unplug the blender first. Shocks are not fun.
likewise, make sure that blade rotates easily from turning the coupling on the outside of the jug. If not, the bearing may be siezed or contaminated. That you'd likely want to fix by replacement.
Hope this helps!