Before moving on from the PRIMARY function of hearing, I would like to qhare with you what Professor J.C. LAFON said in a TV show back in 1985 (1), I already mentioned it in « LAFON 23… », but I am not getting tired of it !
Questioned by someone (that I will name Q for questioner) here is what Professor J.C. LAFON (who will be referred to as Prof.) answered :
« Q: So, there is, inside our ear, an organ sensing the position of our body in space ?
Prof.: Indeed, and that is very interesting. The question has been raised as to why the vestibular system was located near the cochlear system, i.e. the system in charge of hearing being next to that respnsible for maintaining the body’s balance, sharing the same fluid and being affected by similar pathologies. Deafness and impaired equilibrium often come together, in some kind of two-symptom combination for a same disease. But there is a clear explanation to that. The vestibule system helps us estimate where we are, in relation with gravity and statics, and sends us information of dynamic nature, i.e. about movement, whether it be when the head is shifting, or when our whole body is moving, etc.
Q: And whether these are quick or slow movements…
Prof.: Of various velocity… Basically, it allows us to lacate where we are, as individuals, in relation to our surroundings. Whereas the auditory portion gives us a global picture of our environment while helping us locate ourselves within it. And these two pictures are a perfect match.
Q: How can the ear generate a self-centered picture of surroundings ?
Prof.: Acoustics… Les us say that you are standing in a room: there will be sound reflections. These reflections provide information on the size of the room, on the walls nature, they will help you notice any aperture and whether walls are bare or insulated… in terms of acoustics. These reflections thus give you information about the whole volume of the room where you are standing. They also help you estimate how distant the objects in the room are from you: this is echo. You know, this is just like when you go to the mountains and you can assess distance by the difference between the time you hear what you just shout out and the time it takes to hear it back »
(1) This video is still available on INA’s (French National Audiovisual Institute) website, and downloadable for 2.99 euros. TV show title: ENTENDRE
(translated from french by O.B.)