You never want your bike too close to the aluminum skin unrestrained . Bad bad costly dings and sometimes deep lacerations .
Like the earlier posts, go outside your rig and turn the two latches holding the kitchen exhaust flap down. Manually flip the flap open and find something to hold it open while you go inside to turn the fan on. Check the noise level and if still too loud for you, then do the modifications. If ok, then clean the flap to remove any sticky oily debris lack of use. Remember to close the flaps when not in use to avoid rodents invasion .