From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Page 2 of a letter from India Tyre & Rubber Company Ltd. regarding tyre noise testing.
| Identifier | ExFiles\Box 30\5\ Scan140 | |
| Date | 7th October 1935 | |
| Page 2. W. A.{Mr Adams} Robotham Esq., 7th October, 1935. The test was made by mounting the tyre on a driven test drum having a smooth surface and running the tyres at varying speeds at 30 lbs. and 25 lbs. inflation pressure with a 10 cwt. load. The machine for measuring the noise was one that we obtained from the Standard Telephones & Cables Limited and its principle of operation is the "Offset Receiver" method of measurement in which the observer listens simultaneously to the noise under observation and to a standard reference noise in a head phone receiver which is held a fixed distance from his ear. The figures are the average of those obtained by these observers at different positions around the tyre and, of course, the human element enters into the results obtained but this is offset to some extent by having these observers. One difficulty in the test was that the motors and drive to the wheel made a considerable amount of noise and a reading was taken for the general noise in the room without the tyre running. In order to obtain a true measurement of the noise produced by the tyres these figures should be subtracted from the larger figures leaving a figure which is so low from a noise standpoint that it is difficult to measure accurately. The testing apparatus when set to produce a noise of this magnitude is almost inaudible. Of course, we realise that we have not reproduced road conditions accurately with this test but it has value as a comparison of different designs of tread. We are now proposing to carry out further tests under road conditions. We should be pleased to have your report re the 7.00/18 tyres and you may be assured that we will do everything possible to give you a tyre which will meet your requirements. Yours faithfully, INDIA TYRE & RUBBER COMPANY LIMITED. Works Manager. | ||