An earphone device (1) to be worn in the ear, which earphone device (1) comprising a main body (18) to be arranged in the concha (19) of the outer ear (14) of a user and an optical sensor (35), which optical sensor (35) comprises a light emitter (16) and a light detector (17). The earphone device (1) comprises window means (8, 9) through which light emitted by the light emitter (16) can be transmitted. The window means (8, 9) comprises an end face (31) adapted to abut a conchal wall (37) at a sensing position (36). The main body (18) comprises a speaker protrusion (26) to be inserted into to ear canal (15). The distance between the speaker protrusion (26) and the end face (31) is adjustable.