Q: 2009 kia Borrego, low pitched humming noise when i reach 40 mph

It sounds like you may have a failing or worn out wheel bearing. A wheel bearing will usually fail due to pitting or small damage on the surface of the rollers or the bearing race. Both the surface of the rollers and the race is precision machined to tight tolerances and highly polished to allow the rollers to pass easily over the race with the addition of bearing grease for lubrication and cooling. Over time the bearing will wear slightly, allowing microscopic pieces of metal into the grease. Bearing noise can sound a lot like a brake pad dragging or grinding. It can also sound like whirring, whining or humming depending on how much sound deadening material your vehicle has in it. Bearing noise will always be dependent on vehicle speed meaning as you speed up or slow down the noise should change frequency or loudness. Cornering may affect the noise from a damaged front wheel bearing and is usually more pronounced as you make turns. I would suggest having a professional from Your Mechanic come to your location to diagnose and inspect your vehicle.