I just got a 07 Mazdaspeed3 with 64000 miles there's this Bose coming from driver back side when I hit bumps and its loud but little bumps at slow speeds still loud but not As bad 10 to 15mph no noise what could this be stabilizer heat shield??

 

i assume bose was autocorrected from noise?
what's this noise sound like, heavy, tinny, plastic, single thunk or a clatter etc..