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).
Exhaust boom noise issues at certain speeds and potential remedies.
| Identifier | ExFiles\Box 93\1\ scan0068 | |
| Date | 7th December 1936 | |
| J23 Wyman Noted you S/W. Rm.{William Robotham - Chief Engineer} c. to SE. C: " HS.{Lord Ernest Hives - Chair} C: " BY C: " E.{Mr Elliott - Chief Engineer} Exhaust Boom - GUL-1. Cx{Major Len W. Cox - Advertising Manager}3/KW8.12.36. Dictated 7.12.36. I have now had an opportunity of using this car further in order to get impressions of the exhaust boom. I have tried it with and without the flattened extension piece with which you sent it back to us. Without this extension piece the car under certain conditions, mostly with a following wind at speeds from 27-30, is much noisier than we like. Between those speeds there is a combination of exhaust and tyre noise, which together are very pronounced. Possibly the elimination of one of them or the minimising of both of them would produce a standard of silence which nobody could criticise, but in my view the car is not beyond criticism in that way at present. The difference in the silence of the car at 25 m.p.h. and 28.m.p.h. is most noticeable. At the former speed both tyres and exhaust are practically inaudible, and between 27 and 30 are both at their worst. Also, I can definitely say that the car is more silent at 35 m.p.h. than at anything between 27 and 30. Were it not for the fact that to-day one is forced to drive quite a lot at 30 m.p.h. it is quite possible that these objections would not have become so pronounced, but we do feel that if a substantial improvement could be effected in the noise apparent at 27-30 m.p.h. the car would be a very much nicer one at these speeds. Possibly we are on the right track already with your suggestion to try rubber between the body and chassis frame, and we are hoping to have this car converted in that way at an early date. The tests to which I refer were carried out with new tyres. We take it that you are not in favour of the use of the tail piece because of the hiss at high speeds, because there is a possible slight restriction with consequent loss of power at the higher speeds. Re service complaint, although I have seen at least one complaint of exhaust boom at 30 m.p.h. in one of the (contd) | ||