Once again the FAA are very progresssive on this health issue. It looks like the JAA are imposing hearing requirements that probably date back to the days when radios and nav aids were very crackly and there was a lot of interfering noise in the cockpit, It is redundant in this day and age of active noise reducing headsets and quiet flight decks.
Here is how the FAA handle the issue.
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FAA Certification Standards for Hearing
The current regulations require that any applicant for an airman medical certificate be able to hear an average conversational voice in a quiet room, using both ears, at a distance of 6 feet from the examiner, facing away from the examiner.
For persons who cannot meet that requirement, the FAA allows for a Statement of Demonstrated Ability, or waiver, to be issued following satisfactory completion of additional testing. The Guide for Aviation Medical Examiners details how the FAA determines that the hearing standard is met. Hearing aids are acceptable for any class of medical. If a hearing aid is required to meet the hearing standards, the aviation medical examiner may issue a medical certificate with the limitation "valid only with use of hearing amplification". If a headset is used in place of a hearing aid while flying, the FAA will require a medical flight test. After successful completion of the flight test, a Statement of Demonstrated Ability waiver (SODA) will be issued.
For pilots who are asked to take a Medical Flight Test, the FAA inspector will be observing any or all of the following, as explained in the Flight Inspectors Handbook (FAA 8700.1 Chg. 3 10-1/89):
the ability to hear radio, voice, and signal communications (marker beacons, Morse code identifiers)
the ability to understand a normal, conversational voice level with the engine off and running, on the ground and while airborne, and with the engine at different power settings, and ensure the applicant is not lip reading by having the applicant respond to questions while looking away from the inspector.
the ability to estimate a glide by sound in relation to speed
the ability to recognize an approaching stall by change in sound related to a change in speed
2. Observe an applicant with a total hearing loss demonstrate the following:
Recognition of engine power loss or engine failure by a change in vibration and by instrument scan
Recognition of approaching stall by aerodynamic buffet and visual cues
Recognition of retractable gear emergencies (if in retractable gear aircraft) by observing gear warning lights
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Totally deaf pilots are allowed fly in the US, But not to airports or in airspace where radio communication is required, again this applies to any class of medical, so it is possible to get a first or second (comercial in the US) class medical restricted as above and to fly for hire (dropping parachutists, pipeline inspection etc) as long as you don't go somewhere that you have to talk to someone.
The JAA are way out of line on this and many other medical issues. Individuals who are a little hard of hearing pose no risk to flight safety, they just need to turn the volume on the headset up a little. they have been doing so for years in the US and are not over represented in the accident statistics. They crash airplanes for the same reasons that people with perfect hearing do, most commonly continued vfr flight into imc conditions and all the other usual suspects but never because of something that they did'nt hear, refusing to let these people become pilots is unreasonably preventing otherwise well qualified individuals from doing a job that they are cabable of doing just as well and safely as anyone else.