An embodiment provides a continuous wear hearing device to be worn entirely within the ear canal, comprising a receiver assembly sized to be positioned in the bony portion of the canal, a battery assembly and a microphone assembly. The receiver assembly includes a receiver for supplying acoustic signals to the tympanic membrane. The battery assembly is coupled to the receiver assembly and includes a metal-air battery and a battery vent. The microphone assembly is coupled to the battery assembly and includes a microphone and a microphone sound port. The sound port faces a medial direction with respect to the canal. The orientation and position of the microphone in the canal are configured to reduce fouling of the port by cerumen. The positioning of the microphone assembly defines an air cavity disposed between the microphone assembly and the battery assembly with the port and the vent fluidically coupled to the cavity.