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.
Why does the above not apply to the INITIAL also?
The reality (which I happen to be familiar with) is that the CAA will not give you an IR if one ear is outside the renewal limits, even when it's obvious that the pilot would easily meet the requirements in my quoted section above.
This is CAA+JAA gold-plating. ICAO doesn't require this.