[Multifrequency impedance audiometry and study of occupational deafness: "Teflag", a new test]

The mechanical acoustic theory compares the annular ligament of the stapes to an elastic plot; plot # 2. The coupled stapedial muscle and annular ligament partly ensure the dampening of acoustic impulses (low frequencies in particular) and helped by the stapes footplate, their transmission, by hydraulic pressure to the liquids of the cochlea. This muscle ligament couple represents the true impedance adaptor for the middle ear region. So as to study plot # 2 we have set up a test, called Teflag, using the otoadmittancemetre produced by Grason Stadler. This apparatus enables us to measure the functional state of the ligament (by the study of susceptance, representing the inverse of the reactive forces linked to the inertial mass of the system and to its compliance; in fact that of the ligament. We can also measure the level of the resistive intra-cochlear forces and those of the annular ligament (the study of conductance). Our study compares 25 normal hearing patients and 64 ears with professional deafness. The Teflag gives us an evaluation of the functional state of the annular ligament, from morphological abnormalities of susceptance. Age induced hearing loss differs from professional deafness. A classification into 5 stages has been established following evaluation of functional annular ligament pathology. There is no hearing without oscillation (of a molecular order) of this ligament, which clearly seems to be the key point of the receptor organ, and ensures the detection of sound.