IN YOUR OPINION
Page 81
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Noise Regulations—and the Sound Meter MY attention has been drawn to the report "Noise kegs.
Held Up for Sound Meter?" which appeared in your journal of February 21. This statement by Mr. Marples would seem to give a completely false impression of the present position.
Extensive tests both in this country and abroad have confirmed that a high-grade sound-level meter can give consistent and reproducible ratings for the noise emitted by motor vehicles. The use of a sound-level meter is already specified in the vehicle noise regulations of many countries abroad and for the international (I.S.O.) noise test procedure.
In this country a British Standar& has been prepared specifying the special characteristics of sound-level meters to meet the legal requirements for such tests. Two classes of equipment are described, "vehicle noise meters" for testing stations and vehicle manufacturers and "traffic noise meters" for roadside checks by the police. These instruments are high-quality sound-level meters with self-checking facilities and simplified operation. The self-checking controls are spring loaded to the normal operating positions and the instrument for police use has only a single, directly calibrated scale so that it is impossible for the controls to be incorrectly set. Both classes of equipment are commercially available from my company.
The delay in finalizing the noise regulations in this country undoubtedly arises from the test conditions and not
the lack of a suitable measuring instrument. The driving conditions which have been agreed for the I.S.O. recommendations for the measurement of vehicle noise now differ from the B.S. 3425 procedure2 on which the draft Ministry of Transport regulations were based. As a result, for some vehicles the I.S.O. method gives a slight, but significantly, higher sound level and for others a lower level than B.S. 3425. Unfortunately, the decision is not a simple one, as there are arguments for and against each method. However, until this matter is resolved, and possibly the General Election is behind us, there seems little chance of vehicle noise legislation.
l B.S. 3539:1962 Specification for sound-level Meters for the Measurement of Noise Emitted by Motor Vehicles. 2 B.S. 3425:1961 Measurement of Noise Emitted by Motor Vehicles.
Director, Dawe Instruments Ltd. Acton, London, W.3. F. W. DAWE,