Abstract
A RECENT report by Science Service gives a resume of the discussions during the annual general meeting of the Society of Automotive Engineers at Detroit. It was stated that in the earlier days of motoring the thrill of passing another motorist was incomplete unless your motor had a louder and deeper roar than his. Now motorists are worried even by the amount of noise their tyres make. Modern car mechanisms are so improved that at speeds below 40 miles an hour this noise is clearly audible. In fact some motorists utilise it to keep the speed constant. The low buzz or flutter is due to the trapping of air in parts of the tyres. Noise in motor-cars can be eliminated in two ways, either by absorption or cancellation by interference. In mufflers which absorb sound, the sound energy is converted into heat by resonators owing to the friction of waves passing through small holes and the use of porous materials. Mufflers that depend on wave interference get one part of the sound in opposition in phase with the other, so that they partially cancel. One new type of muffler passes part of the exhaust gas through a venturi tube and it then operates the windshield cleaner. A silencer which utilises both resonance chambers and absorbing materials is sometimes effective in preventing intake noise (power roar). The noise to passengers can be considerably reduced by padding the bodies of the saloon by sound absorbing material in the same way as the acoustical properties of radio studios can be improved. One result of making motor-cars quieter is that the driver often unconsciously increases the speed.
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Quieter Motor-Cars. Nature 133, 904 (1934). https://doi.org/10.1038/133904b0
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DOI: https://doi.org/10.1038/133904b0