An earpiece includes a body having an acoustic driver and an output aperture. A sealing structure extends from a region adjacent the output aperture to hold the output aperture adjacent to the entrance of a user's ear canal. An acoustic nozzle having an acoustic passage conducts sound waves from the acoustic driver to the output aperture. The acoustic passage has a proximal end adjacent the acoustic driver and a distal end adjacent the output aperture. First acoustic impedance is provided at the proximal end of the acoustic nozzle adjacent the acoustic driver. Second acoustic impedance is provided at the distal end of the acoustic nozzle adjacent the output aperture. The volume of the acoustic nozzle and the first and second acoustic impedances are selected to control resonance in the user's ear canal when the sealing structure is engaged with the entrance to the user's ear canal.