Notable appearances: Batman Begins, The Dark Knight, The Dark Knight Rises
In another example of combining style with function, the microphones hidden in the pointed ears of Batman’s cowl give Bruce Wayne the perfect listening device to eavesdrop on the citizens of Gotham. This move was more out of necessity than anything because without these microphones, Batman’s tight mask would render him deaf.
In the comics, the microphones in the hollowed-out bat ear transmit the audio to a sound amplifier next to his real ear that allows him to hear anything he’s pointed at—even if he’s nowhere near the target. This helps when he’s spying on potential enemies from long distances. He can even hear people’s conversations through windows and thick walls.
This device wasn't introduced into the character's cinematic universe until Batman Begins when Christopher Nolan actually showed just how Batman created his complex cowl.