An off-head detection system for an in-ear headset comprises an input device that receives an audio signal, a feed-forward microphone signal, and a driver output signal; an expected-output computation circuit that predicts a value of the driver output signal based on a combination of the audio signal and the feed-forward microphone signal from the signal monitoring circuit, and off-head data from the off-head model; and a comparison circuit that compares the observed output signal provided to the driver and the computed expected output to determine an off-head state of the in-ear headset.