Various implementations include wearable audio devices and related methods for controlling such devices. Some approaches include controlling a wearable audio device by: determining a magnitude of an acoustic transfer function based on an electrical signal from an internal microphone and an audio signal from an acoustic transducer at one or more predetermined frequencies; calibrating a proximity sensor; detecting a change in the state of the wearable audio device from one of: off-head to on-head, or on-head to off-head using both the calibrated proximity sensor and the magnitude of the acoustic transfer function; and adjusting at least one function of the wearable audio device in response to detecting the change from the on-head state to the off-head state or detecting the change from the off-head state to the on-head state.