This hearing reflex is due to the response of the inferior colliculus located at the back of the midbrain to stimuli such as noise. Basically, the inferior colliculus is the main auditorium of the human body. External sounds travel as sensory-auditory signals to the inferior colliculus through electrochemical currents so that they can process this information to the central brain. It consist of two front lobes corresponding to both ears. It regulates frequency recognition, pitch discrimination and signal integration. This is also what facilitates your selective hearing where you cannot hear your self-induced sounds like breathing and chewing.
