Now, let’s move on to the well known hearing function, that we practice every day in our life and our job : SECONDARY hearing, i.e. communication hearing.
Having a hearing test is not only doing one’s best with the only pure tone audiometry. The pure tone audiometry use pure sounds, and the ear is not a frequency sensor. We can test the ear through this method, but it is not made for this. Morover, pure tone audiometry only tests cochlea.
Thus, we leave aside whatever is happening in the auditory pathways, from the cochlear nuclei to the primary auditory cortex, including : the superior olivary complex / lateral lemnicus / inferior colliculus / medial geniculate body.
So, if we want to test hearing, we must absolutely perform a speech audiometry.
That’s the reason why Professor J.C.LAFON has developped his lists, and amongst others, the integration list.
You said Integration, but what’s this ?
The integration mechanism, related to the hearing function, is what enables us to identify what we hear. This is how we can understand. If a person has a bad integration, he/she will have a troubled understanding.
Professor J.C. LAFON tell us more about it : » The sound message received by the cochlea and adapted by the organ of Corti into a nerve message, has to be integrated into neurological circuits. I call integration the fact of superimposing within the same system and in the same time, two phenomena far apart in time and space. This very general definition addresses the integrative power of sensorial systems, as well as complex memory-based circuits. Identifying a signifiant message among a set of sounds is comparing this acoustic structure to another one that we knew previously, and to which we have linked a symbolisation. It’s the comparison in present time of two signals, a memory-based signal and a current or recently passed one. The cochlea memory is represented by the time of vibratory persistence taken by a pulse ; that of neurological circuits can spread over a whole life ; human knowledge is based upon ancient integrations. Those are the three memory scales, from the split second to the millenia. Integration leads to knowledge »(1)
It’s so beautiful that you’re invited to read this paragraph a second time !
So during all our respective lives and faced to any auditory message oncoming to us, we compare it to what we have memorized since we were children. If what happens relates to something we’ve already met, it is identified and it becomes significant. If what happens is not like anything else that we’ve already met, we indentify nothing, and it is unsignificant : this is only « noise ». Faced to an unknown foreign language, we don’t understand a single word, it just sounds like noise.
In order to try to be more explicit, I shall give an example taken from the visual world : let’s imagine you come across someone in the street, and you look at him/her. Automatically, you compare the persone’s visual image to all the images you have recorded. If it matches a visual image already memorized, you can identify and recognize the person. This is what integration is.
If auditory integration is defective, then hearing aid will be difficult, to implement, and it’s a really poor prognosis for speech understanding in noisy conditions.
(1) Professor J.C. LAFON « message and phonetics » page 57.