Abstract: Techniques are provided for automatically channelizing a stereo audio signal in a headphone device such that a correct audio channel is output to a user's ear regardless of which ear an earbud is inserted. In an embodiment, at least one earbud is configured with a sensor arranged on a housing of the earbud. The placement of the sensor can be keyed or otherwise positioned to identify a right or left ear based on proximity/contact with certain anatomy of the ear. For instance, the sensor can be in detectable range of ear anatomy such as a tragus/antitragus when inserted in one ear and outside of detectable range of the same when inserted in the other. By automatically detecting which ear an earbud has been inserted, audio channels can be switched as necessary enabling users to insert earbuds without regard for which is a right earbud and which is a left earbud.