Hearing loss and radiotelephony intelligibility in civilian airline pilots

Airline pilots with a mild to moderate hearing loss are regularly examined in the Netherlands National Aerospace Medical Centre. If this hearing loss exceeds the national hearing standards not only a tone-audiometric test but also routine speech-audiometry is performed. The maximal discrimination of phonetically balanced monosyllable words (20 word lists) in 16 airline pilots (32 ears) with such a hearing loss varies between 65%-100%. However, none of these pilots complains of a bad speech-intelligibility in the cockpit. This may indicate that there is a poor relation between the routine speech discrimination and the speech intelligibility in the working situation. We developed a "speech-audiometric" test (RT-test) which is completely based on the aviation jargon used in radiotelephony (RT) communications. In our group of 16 pilots the maximal discrimination in the RT-test was excellent. Even for ears with a maximal discrimination of 65%-70% in the routine speech-audiometric test the maximal RT-discrimination was 99%-100%. These pilots were all very experienced (average: 14,360 flying hours). Undoubtedly, this experience is of great importance in radiotelephony-intelligibility.