ICE running noise issues

So far I am loving my used 2013 Volt that I just recently bought. It has 65K miles on it, most of that on the ICE with about 11k on electric. Everything on the car is doing great. The only issue (and I have searched the forum for info) that I have is that when the ICE is running you can feel engine vibration in the car. Especially at certain RPM's. I swear sometimes it sounds like an airplane propeller or a motorboat echoing through the car. I can't imagine it sounding like this when it was new for it is quite noticable. It is almost like there is something (shield or something) that vibrates when the engine rev's up through it's rpms and it sends vibrations throughout the car or maybe the exhaust is touching the frame or body somewhere. The car has not had any accidents that I can tell. Carfax was clean and it was a fleet car so I have all maintenance records on it and no issues have been noted. The engine appears to run fine though and I don't have any messages or codes. It is just the vibration and the noise. Is this something that is common? I have not had the opportunity to ride in another Volt to see how others sound when running on the ICE. Just wanted to see if anyone else has had any excessive engine vibration/noise issues and what they may have found or done to get it fixed.