How hearing works

It is the vector for understanding the beings and things around us. It carries both useful meanings for life and clues about the intentions, moods and emotional tone of those who speak to us. Understanding the mechanisms that make this link with the outside world possible has led to the development of solutions to compensate for the deficiencies that can affect our hearing. Because when we are deprived of sound, we are deprived not only of meaning, but above all of harmonious relationships with others.

Sound is not received passively by the ear. It is processed and transformed several times. Even if we have the impression of immediate reception, its perception is actually constructed. It's a kind of conversion exercise that mobilises both our ear and our brain. The ear is an organ whose role is to convert sound waves into electrical currents that our brain decodes and then translates into sounds. The process of hearing is therefore intricate, resulting from a multitude of operations that we are unaware of. Yet, without it, the world would remain a vast collection of mute things.

The visible part of the ear, the pinna, picks up sound. The sound then travels through the external auditory canal to the eardrum. These three parts - pinna, auditory canal and eardrum - form what is known as the external ear. At this stage, sound is still a set of vibrations in the air, expressed in terms of wavelength.

The eardrum is a thin membrane that marks the boundary between the outer and middle ear. Sound waves cause the eardrum to vibrate. As it vibrates, its inner wall sets in motion the ossicles of the middle ear, which transmit and amplify the vibrations to the oval window, the thin membrane that leads to the inner ear.

The essential function of the inner ear is to convert sound waves into electrical impulses through nerve cells called hair cells. The liquid in the inner ear, moved by the vibrations received, stimulates these cells, which convert the physical information into electrical information. The electrical impulses from the cells are transmitted to the brain via the auditory nerve. 
At the end of this process, the brain transforms the electrical flow into sounds that we perceive and interpret in a way that seems immediate to us, whereas this is the result of a genuine physico-chemical exchange between the outside and the inside.