The most common reason for noise in the water lines is trash or a loose washer (o-ring). Turn the water off at the wall supply valve, take the handles off, remove the nut and pull the cartridge out. You will probably find the problem under the cartridge. Put your cupped hand over the opening and turn the water back on at the wall supply valve (called a stop). This should run any loose trash out of the line and solve the problem. If it doesn't, take the cartridge out and head for the big box store for a matching one (try to learn the brand name first).
Occasionally the hum is from the stop which has a washer in it also. The one in the hot water side will always wear out first but change them both anyway; we don't want to have to come back in a month or so.
To change a stop washer you must turn the water off at the main valve or water meter. Take the packing nut off, unscrew the cartridge, most of them have a common faucet washer stretched over a plastic stub. Simply slip the old one off and a new one on. Screw the packing nut back on, turn the valve off and turn the water main back on. If there is no puddle when you get back to the bathroom, pat yourself on the back, take $100 out of one pocket, put it in another and be glad you saved it. If the packing nut leaks around the stem, tighten the packing nut half a turn or so (if it gets too tight it will not let you turn the valve on or off).