A method of operating a lock from a portable remote device includes sending a radio frequency identification signal from the portable remote device to a controller for the lock, and receiving the radio frequency identification signal at the lock controller and identifying the remote device as an authorized user of the lock. The method then includes sending a sound frequency identification signal from the portable remote device to the lock controller, receiving the sound frequency identification signal at the lock controller and identifying the remote device as an authorized user of the lock. The method further includes authorizing operation of the lock in accordance with the radio or sound frequency identification signal from the portable remote device. A system for practicing the method includes a lock controller capable of receiving a radio frequency identification signal and a sound frequency identification signal from the portable remote device.