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).
Test report comparing horsepower output with various silencer configurations at different engine speeds.
| Identifier | WestWitteringFiles\I\October1922\ Scan46 | |
| Date | 17th October 1922 guessed | |
| Test No. | Conditions | Horse power --- | --- | --- | | 1500 | 2000 | 2500 | 3000 1 | Standard silencer | 30.3 | 39.5 | 44.7 | 48.3 2 | With no silencer fitted. | 31.7 | 42.5 | 48.4 | 51.2 3 | Silencer made to M.Sch.1304 - cut-out closed. | 30.6 | 39.9 | 45.2 | 48.2 4 | As above - cut-out open. | 30.9 | 40.2 | 47.8 | 48.0 5 | As No.3 - with two extra baffles - cut-out closed. | 30.3 | 39.3 | 45.0 | 45.2 6 | Experimental silencer with butterfly cut-out as per sketch - cut-out closed. | 30.3 | 39.9 | 45.0 | 45.3 7 | As No.6 - cut-out open. | 30.9 | 40.2 | 48.0 | 48.0 8 | Standard silencer with cut-out arranged in similar position to 40/50. | 31.7 | 42.0 | 48.4 | 50.8 | ||