A method and device for detecting whether a headset is on ear. A probe signal is generated for acoustic playback from a speaker. A microphone signal from a microphone is received, the microphone signal comprising at least a portion of the probe signal as received at the microphone. The microphone signal is passed to a state estimator, to produce an estimate of at least one parameter of the portion of the probe signal contained in the microphone signal. The estimate of the at least one parameter is processed to determine whether the headset is on ear.