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British employers with noisy premises are legally obliged to check sound
levels with a sound pressure level meter. The meters must be accurately
calibrated and checked every two years. The Association of Noise Consultants in
Royston, Hertfordshire, has been working on a system that lets employers
calibrate meters without sending them all off to a specialist laboratory (GB 2
326 478). Their calibration CD contains 69 test tracks of fixed level and plays
on an ordinary CD player. An interface unit connects the CD player to the sound
level meter, amplifying the signal from the CD so that it always delivers a
standard level to the meter.