WHAT ARE “PHONS”?

Otago Daily Times, Issue 22723, 8 November 1935, Page 12

WHAT ARE “PHONS”?

NOISE LIMIT FOR MOTORS SPECIAL COMMITTEE’S PLAN (From Our Own Correspondent) (By Air Mail) LONDON, October 12. People will he hearing a great deal about “ Phons ” in the near if the Minister of Transport adopts the proposals made in a report presented to him by a Departmental Committee who have been considering ’the question of noise. The Minister has argued that noise must be limited not only to preserve the amenities of the road, but also for safety, because the noisy driver is often found to drive dangerously. Excessive noise has for some time past been illegal, but the law has in practice been ignored, for there was no definition of what constituted an offence? This committee recommends the imposition of of a noise-limit calculated in terms of “ phons ” —the latest unit used in measuring noise. The committee proposes that after August 1: No new motor car, cycle, or lorry shall be allowed to make more than 90 phons of noise When running at 30 m.p.h. on full throttle; or More than 95 phons when, with the vehicle stationary, the engine is running at full speed. The committee came to the following conclusions: — Except at high engine speeds—over 50 m.p.h., or racing the engine with the vehicle stationary—the average car today is not unduly noisy. A number of sports cars are too noisy, but could be quietened. Except at moderate, steady speeds many motor cycles are too noisy. “It is evident that the high performance of such machines has outpaced the art of quietening them.” Certain commercial vehicles are somewhat noisy, but could probably be iniprived by attention to engine and gear. SCALE OF PHONS. As for the scale of measui ement, the “ phon ”is the unit used. ero is the “threshold of audibility," and the scale of sounds is as follows: — Noise. Phons. Quiet country house 20-30 Watch ticking at 3ft 30 Quiet street ... 30-40 Conversation 60-75 Interior of express train, windows open 80-85 Busy typing office 90 Interior of tube train, windows open 90-95 Loud motor horn 100-'OS Printing room or pneumatic drill 110 Aeroplane engine 110-120 When 130 phons are reached pain is caused to the hearer.