From the moment I became interested in the problems of hearing, I have been aware of the studies by the health organizations concerning hearing deficiencies caused by wearing headphones for certain occupations.
The statistics were related to telephone operators, translators, and musicians, and even though I cannot exactly quote the results now, I remember that the people whose hearing had been impaired through occupationally-related causes could obtain an official pension. Thus, it was officially recognized that wearing headphones to listen to speech or music could lead to some hearing damage. Afterwards I was asked by several lawyers to evaluate the percentage of hearing loss of these individuals. This percentage was very different for each person, probably because of differences in the physiological and physical resistance of each person.
If it was admitted that wearing headphones to listen to speech or music could lead to some damage to normal individuals, it is obvious that someone who had been treated with AIT, who had some problem of hearing, would be more sensitive to all hearing aggressions, including wearing headphones. This is the reason why I forbid the use of headphones, or at least, if people have to do this because of their work, to minimize the amount of time for this use.
What causes this hearing problem when headphones are used?
I have never read any official explanation, if one even exists, and have to suggest my own opinion.
Normally, when you hear sounds, such as music, talking, noises from your own behavior, songs of the birds, as well as thunderclaps, any kinds of engines or of explosions, they reach your tympanic drums after passing through a large quantity of atmosphere. This air works as a shock absorber to diminish the intensity of the impact on the eardrum.
However, when you are hearing sounds coming directly from the membrane of the headphone to your tympanic membrane, through the one square centimeter of air included in your outer ear canal, the impact is practically direct, without any possibility of easing this aggression.
This constant aggression is transmitted to the ossicles, then to the inner ear. This explains why many of people working with headphones have a trough, or drop on 4000 Hertz on their audiogram, similar to that of people working in noisy factories.
On the other hand, wearing headphones eliminates all the sounds coming from outside, increasing the sounds coming from your own body, your own voice, creating a sort of echo. This aspect of the problem is more important for people wearing earplugs placed directly in the outer ear canal close to the eardrum. Then there is no more air to help the vibration of the tympanic drum and all your own sounds lead directly to the cochlea and the brain, which is not satisfactory, physiologically or psychologically.
As soon as I became aware of the existence of walkmans, I warned officials of the danger of this type of device, for the same reason ... in vain. Now the same officials are discovering this danger and giving precautions.
It is important to mention that the AIT processed music is therapeutic; and thus, wearing headphones during the listening sessions will not cause any harm.