An earphone comprises an acoustic waveguide (305), for coupling sound waves from an acoustic transducer into an ear (5), the waveguide having an outer end (315) and an inner end (320), at least the inner end being open. The acoustic transducer (310) is arranged at the outer end (315) of the acoustic waveguide and the inner end (320) of the acoustic waveguide is configured to be located in the ear (5). The acoustic waveguide (305) has a neck (340) between the outer end (315) and the inner end (320), and has a cross section at the neck that is smaller than a cross section at each of the outer end and the inner end.