Mr. B doesn't quite have all his animal sounds figured out (okay he makes the gggaaaaahhhhh sound for pretty much every animal besides the pig) but he sure knows his tractor sounds. One of his favorite things at the orchard is watching the tractor drive around (an occasional tractor ride sure thrilled him too) and when he got this tractor from 'Papa Tractor' himself, he knew just what noise to make. Buhbuhbuhbrroooom is obviously the noise tractors make. Ask the farming expert yourself. :)
PS- check out how he pushes it with his tummy to get it to move. :)