What is a Phon?

Auckland Star, Volume LXVIII, Issue 300, 18 December 1937, Page 8 (Supplement)

What is a Phon?

A new measure has been added t» the list of standard weights and measures recognised in Britain, and before long it will be as familiar as the knot, the therm and the watt. Known as the phon, it is to represent the British unit of loudness, and it has already found itself in print on a noise-meter devised by the National Physical Laboratory. Before long the phon will make its bow in the Courts of Law, for * committee of the Ministry of Transport has recommended that no noise exceeding 90 phons should be emitted from any motor vehicle. We may all hope, says a London journal, that the motor cyclist nuisance who rushe* past us with a shriek of 900 phons will now disappear from the streets; too long has he been allowed to indulge his brutal selfishness at eTerybody else's expense. The nois« meter fa * mechanical ear and can estimate the degree of loudness not only when the sound is continuous hut also when it is intermittent, like the throbbinp- of an enjrine. The dejrrce of loudness is #ihown by a pointer moving over a dial, and we may look forward to one more gadjret for the dashboard of our motor ears.