Q: There is a loud humming noise coming from under the car becomes louder when I let off the gas

A common cause of the type of noise you are describing is one or more failed wheel bearings. The exact wheel position can be determined using chassis ears (remote wireless microphones). Not to worry, as replacing wheel bearings on most cars is a very mundane repair and all you need to do is identify which wheel position the fault lies at and install a new bearing. Please note though that there are lots of technical specifications in bearing replacement such as the need to use a calibrated torque wrench to install the axle nut. If the installation is not done according to the instructions, the new bearing is often ruined so if you happen to hire somebody on the side, or even use a "shop" if they are not reading from the Factory Service Manual, do not have a calibrated torque wrench and so on and so forth, the repair will be a waste. If you desire that the origin of the noise be pinpointed, and the bearing(s) replaced as needed, please request a noise diagnostic - suspected bearing noise and the responding certified mechanic will get this taken care of for you promptly. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.