An in-canal hearing device includes a receiver, battery, and microphone assembly with a housing. The housing has an air and sound opening which is covered with a structure to inhibit the entry of cerumen and moisture. The structure may be in the form of an end cap having passages with walls which are both hydrophobic and oleophobic to prevent the entry of water, cerumen and other liquids. The structure may also include a flexible tube or a rigid perforated shell surrounding the passages that inhibit the deposition of solid cerumen and other debris onto the passages.