Clearly not all, as by the end of the year, 1,282 people had been prosecuted under the law, even though the noise was not quantifiable. That would soon change: in 1937, when “silence had already moved away from the gold standard,” we enjoyed our first attempt at a sound-measuring machine.
Two units of sound had already been devised: the decibel, a pure measure of mechanical energy, and the phon, a measure of intensity for the human ear, which takes into account variables in the way it perceives different frequencies.
The Ministry of Transport had recommended that no car exceed 90 phons, a power slightly higher than sitting next to an open window on an express train. The Wolseley sedans we tested topped out at 77 when cruising at 30 mph in top gear, 18 feet from the microphone.
More regulations were introduced in 1955, as car ownership became democratized: “Every [ICE] The vehicle shall be equipped with a muffler, expansion chamber or other device suitable and sufficient to reduce exhaust noise to a reasonable extent.”
However, as one MP argued in 1959, “many vehicles are especially unpleasant in this respect, especially motorcycles and sports cars. They probably do not make excessive noise when they come from the manufacturer, but, after having been improved in the opinion of the owners, they make an infernal noise which is completely unnecessary.”
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