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).
Performance graph comparing power loss, back pressure and B.H.P for open exhaust, resonance silencer, and standard silencer configurations on a 20/25 HP engine.
| Identifier | ExFiles\Box 179b\2\ img025 | |
| Date | 12th October 1932 guessed | |
| 20/25 HP RESONANCE SILENCER POWER LOSS I ① OPEN EXHAUST ② RESONANCE SILENCER ③ STANDARD SILENCER EXHAUST BACK PRESSURE INS. HG B.H.P R.P.M | ||