The invention relates to a device for ventilating the middle ear by means of a ventilation tube which is made of a tissue-compatible material, preferably titanium, and with a through-channel for air communication between the cavity of the middle ear and the outside air. The measurement device comprises a sensor ring which may be positioned adjacent to and in close contact with the inner ring or outer ring of the bearing, the sensor ring having at least one weakening at its circumference and at least one sensor being positioned in the at least one weakening. The mould can be inserted in an autoclave and the reservoir is configured to permit the transfer of the resin from the reservoir to the inlet duct under the effect of the temperature and of the pressure that are produced in the autoclave, thus allowing the resin to be injected into the mould. The approximated integrated reflectance response of the aperture is then determined based on the reflectance response at the first point and the second point and the weighted average of the reflectance response at the first point and the second point.