PickyPerkins,
If it were to fail, it is outside the aircraft, the length of the aircraft away from the cockpit, with the aircraft moving away from the noise in relative motion, and a cockpit door that is closed, and well insulated. Think about how quiet it is in an aircraft with the engine noise just outside. Can you hear the APU running whilst on the ground with a cockpit door open ?
The term "loud noise/bang" I would suggest could only be something relatively close to be heard in a closed cockpit.