brian wrote:
I would imagine the shriek sound to be the blade revolving on the hub whilst
cutting (slipping), a dull blade just requires more pressure and time to
make a cut.

Slipping seems unlikely. I think there are usually pins in the hub. A
dull blade taking longer and more force to cut is my recollection too.
The saw I used sometimes screeched. It might not be significant.

Best wishes,

Chris