A canal phone incorporates a transducer within an isolation sound chamber for reproducing sound from an audio source, and a sound-transmission passageway, or ambient sound port, for allowing ambient sounds to enter the isolation sound chamber. The passageway has inner and outer apertures, one oriented towards the ambient noise environment outside of the listener's ear and the other oriented toward the isolated chamber formed by the space between a loudspeaker diaphragm within the canal phone and the tympanum of the listener's ear. The canal phone has a port blocking switch mechanism that selectively opens or closes the aperture of the passageway that is open to the ambient noise. This switch mechanism may also electrically disconnect the transducer and seal either the outer or the inner end of the passageway in different embodiments of the invention.