Dynamic study of the acoustic reflex has brought into evidence that 1. age has a significant influence on various reflex response parameters 2. study of dynamic parameters of the acoustic reflex enables changes in the reflex arc to be objectified. This is therefore an objective measurement of recruitment in impedance measurement. The author proposes to study the following parameters: rise time, recovery time, and the variations of maximum amplitude as function of sound stimulation intensity. Study of these three parameters provides a highly sensitive test of change in the dynamics of the acoustic reflex, for indeed this test reveals pathology well before the Reflex Decay Test does so.