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).
Analysis of wind noise mechanics and test results for a Bentley 4 Door Saloon with a sunshine roof.
| Identifier | ExFiles\Box 160\2\ scan0173 | |
| Date | 20th February 1934 guessed | |
| - 3 - All tests are made with the Sunshine roof closed, (if any) and the windows up. MECHANICS OF WIND NOISE. Relatively, the car may be considered to be stationary and the airstream coming towards it. There appears to be possibly two fundamental sources of noise:- (1) The passage of a blade of air over an opening having a sharp edge and having a resonance cavity behind (The organ pipe). (2) The passage of a blade of air over a diaphanous surface, causing the latter to vibrate. (Musical Drum). In category (1) come the doorshuts and sunshine roof joints, and in (2) comes the sunshine roof and shield. We have appreciated both of these and have formed the opinion that (1) is the chief offender. Below a certain airspeed the air vibrations are not set up. Once set up they increase with speed. The speeds used during the test were from 25 m.p.h. to 80. m.p.h. 1ST DAY'S TESTS. Weather fine, dry, Very cold - Barometer high. No wind. Venue, Watford Bye-Pass - speeds 25-80. BENTLEY 4 Door Saloon - Sunshine Roof (B.73-AE - Mulliner, Chiswick). This body was very similar to our standard saloon. The wind noises were very bad - the worst we have heard. (a) On opening the Sunshine roof 1 3/4", a very big cure was made, so we covered over the joint of the leading edge with adhesive tape and produced the same improvement - about 50%. The sliding roof stood proud of the eddy-free front. | ||