A portable electronic device including an enclosure having an enclosure wall that forms an interior chamber. A speaker module is positioned within the interior chamber and includes a speaker and a module wall forming a back volume chamber of the speaker. The back volume chamber includes an acoustic vent port formed through the module wall to acoustically couple the back volume chamber to the interior chamber. The device further including an electromechanical valve for regulating the acoustic coupling of the back volume chamber to the interior chamber. The electromechanical valve is operable to transition between an open configuration in which the acoustic vent port is open to the interior chamber and a closed configuration in which the acoustic vent port is closed off from the interior chamber.