Embodiments may involve a computing device with a mechanical interface, such as a mechanical button or slider. The mechanical interface can be configured to generate, when actuated, vibration and/or acoustic signals having a characteristic pattern. The computing device can detect actuation of the mechanical interface by: receiving acoustic signal data generated by an acoustic sensing unit of the computing device; receiving vibration signal data generated by a vibration sensing unit of the computing device; and determining, based on a comparison of the acoustic and vibration signal data with the characteristic acoustic and vibration patterns, that the mechanical interface has been actuated.