JAR Class 1 Hearing Standards
UK CAA JAA Class 1 Hearing Standards are here - Audio - JAR Class 1 Hearing Standards | Medical | Safety Regulation
However the hearing of experienced pilots at re-certification can be acceptable even if worse than the levels above, as JAR-FCL 3 Appendix 16 to Subparts B and C, paragraph 2 (b) states that: ‘If satisfactory hearing in a noise field corresponding to normal flight deck working conditions during all phases of flight can be demonstrated, recertification may be considered by the AMS (Aeromedical Section)’. This will usually take the form of a flight (real or simulated) with a training captain or instructor who reports that all tasks involving hearing were performed satisfactorily.
I have had to perform this hearing check on a CPL(H) student after an operation on his ears, which was satisfactory
The hearing loss that I and others flying the S92A have suffered is above 3000Hz thus currently no medical restrictions.