Clearly not all of them, though, as by the end of the year, 1282 people had been prosecuted under the act, despite noise being unquantifiable. That would soon change: in 1937, by which point “silence had rather fallen away from the golden standard”, we enjoyed our first try of a sound measuring machine.
Already two units of sound had been devised: the decibel, a pure measurement of mechanical energy, and the phon, one of loudness to the human ear, accounting for variables in how it perceives differing frequencies.
The Ministry of Transport had recommended that no car should exceed 90 phons – slightly above the potency of sitting by an open window on an express train. The Wolseley saloons that we tested peaked at 77 when cruising at 30mph in top gear, 18ft from the microphone.
More regulation was introduced in 1955, as car ownership became democratised: “Every [ICE] vehicle shall be fitted with silencer, expansion chamber or other contrivance suitable and sufficient for reducing as far as may be reasonable the exhaust noise.”
Yet, as an MP argued in 1959, “many vehicles are particularly obnoxious in this respect, especially motorcycles and sports cars. They probably do not make an excessive noise when they come from the manufacturers but, after having been improved in the view of the owners, a hellish noise is created which is completely unnecessary.”