After getting rear-ended, the blower on my TM doesn't sound the same. It was a minor fender bender with no visible damage to the TM. Can the bearings have been damaged?
Rob have you checked the mounting bolts to the unit. Is it possible one or more could be allowing vibration causing the blower to sound different. Assuming it's a slide-in.
If the blower to the muffler is connected with flexible hose it could have torn. Even with a small tear the blower changes its tone. I have blown out chunks of old blower hose while working and the volume of the blower screams. Fairly easy fix.