A humming noise during the spin cycle isn't normal if the machine used to be quiet. With an LG in this class, noise usually appears either from worn drum bearings or when something foreign gets inside - a coin, button, underwire. First, do a simple check: run the machine empty on spin mode and listen to see if the noise is still there. If the sound is the same, it's most likely a problem with the bearings or the seal. If it's quieter - then something's probably stuck between the drum and the tub.
Either way, this requires taking it apart, and it'll be easier with warranty - take it to service while the machine is still under warranty. I wouldn't recommend taking it apart yourself; LGs are built so you have to remove the front panel, and it's easy to damage something else. If the warranty's expired, ask the service for an estimate: bearing replacement usually costs a fair bit, but it's still cheaper than a new machine. The machine will hold up for another month or two, so there's no real urgency.