Not calibrated
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The article by Tony Wilding under the heading "Noise regulations not enforceable" (CM May 24), says that "scepticism exists on the question of accuracy in taking readings" on noise meters, this statement being apparently based upon discrepancies of up to 2 decibels between readings for the same vehicle on six meters with their microphones set close together, at the Brands Hatch demonstration.
It should be pointed out that while the sound meters in use conformed to the BS 3539 specification laid down in the regulations, they had not been calibrated and certified by the National Physical Laboratory —as those to be used for enforcement will have to be—and the minor diserepancies noted were, therefore, understandable.
J. P. MORRIS, Head of Information, Ministry of Transport.