Abstract: An earbud may include capacitive sensor electrodes and a capacitance-to-digital converter that is configured to make capacitance measurements with the capacitive sensor electrodes. The earbud may have a housing in which a speaker is mounted. A tubular portion of the housing may have a passageway that is aligned with the speaker. The tubular portion may be received within the ear canal of a user. The tubular portion may include a tubular member on which the capacitive sensor electrodes are formed. The tubular member may be formed from a compressible tubular member that is compressed when the earbud is worn in the ear of the user. Ring-shaped electrodes and other electrodes may be formed on the compressible tubular member. Control circuitry in the earbud may determine whether the earbud is fully or partially within the ear of a user based on the capacitance measurements.

Abstract: An electronic device such as an earphone may have sensor circuitry. The sensor circuitry may include optical proximity sensors and capacitive sensor circuitry. An ear support structure such as an ear hook may be used to hold the earphone adjacent to an ear of a user. In this position, a speaker in the earphone may be used to present audio to the user. The ear hook may be formed from an insulating elastomeric polymer. A stainless steel wire or other bendable structural support member may be embedded within the elastomeric polymer. The bendable member may hold the ear hook in a desired bent shape after bending by the user. The capacitive sensor circuitry may include one or more capacitive sensor electrodes coupled to capacitance-to-digital converter circuitry. Control circuitry may activate the optical proximity sensors in response to detection of a capacitance to confirm that the earphone is being worn.