What is the possible mason for the candidates fail to get jobs at the BBC? [br]

The British Broadcasting Corporation is rejecting more and more candidates applying for jobs, because they suffer from hearing loss. And this is due to a wide use of personal stereo systems, According to officials at the corporation, about three per cent of them fail to win jobs for this reason. The figure indicates that people suffering from hearing defects are more common than a decade ago.
    Candidates applying for jobs at the British Broadcasting Corporation have always had hearing tests, but the techniques for such tests were not standardized until five years ago. The ’corporation says officially that there is no proof to link personal stereos with hearing disabilities, but frequent exposure to high level of sounds can diminish a person’s understanding of speech. That will rule out his chances of being an engineer taking care of sound quality in recording.
    So experts are now calling for manufacturers of personal stereos to provide a warning light. It flashes when the sound is too loud. One British manufacturer accepted this suggestion. And this manufacturer has made a device that switches itself off when the level of sound is too high. This device is of great significance and the situation changes a lot ever since.