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).
Patent specification detailing claims for a sound-attenuating apparatus.
| Identifier | ExFiles\Box 147\1\ scan0079 | |
| Date | 10th April 1933 | |
| 8 417,935 the passage 140 consists of a single resonance chamber 150 which communicates with the sound wave passage through the perforations in the section 5 of the passage 140 which it surrounds. The section B4 of the unit consists of two resonance chambers 151 and 152 which constitute elements of a two chamber series-compound resonance unit which 10 surrounds the sections 146 and 147 of the passage 140 and communicates with the sound wave passage through the passage 153 and the perforations in the section 146. 15 The detailed description hereinbefore given of the construction and operation of the sound wave attenuating unit shown in Figures 1, 2 and 3 is believed to render any further description of the 20 sound wave attenuating units shown in Figures 4 to 7 superfluous. It will, of course, be understood that although I have illustrated and described my invention as embodied in the 25 exhaust system of an internal combustion engine, the principles upon which it is based and many of the features thereof may be utilized in attenuating sound waves in practically any installation in 30 which they occur in an enclosure or travel through a passage of finite dimensions. Having now particularly described and ascertained the nature of our said inven- 35 tion and in what manner the same is to be performed, we declare that what we claim is:— 1. Apparatus for attenuating sound waves set up by forced vibrations in a 40 sound wave passage, including a unit of at least one chamber for attenuating a lower characteristic (fundamental or lower harmonic) of the passage, the said unit communicating with the passage at 45 or near a nodal point of the characteristic to be attenuated. 2. Apparatus for attenuating sound waves set up by forced vibrations in a sound wave passage, including a unit of 50 at least one chamber so proportioned and dimensioned that it responds to and attenuates by resonance sound waves the frequency of which is equal to the fundamental frequency of the passage or a 55 lower harmonic. 3. Sound wave attenuating apparatus according to claim 2, wherein the said unit communicates with the sound wave passage at or near a nodal point of the 60 fundamental or of the lower harmonic to which the unit responds. 4. Sound wave attenuating apparatus according to any preceding claim, wherein the unit communicates with the 65 sound wave passage through an opening or openings so formed that flow of fluid through the passage cannot substantially disturb the vibrating body of fluid in the said unit. 70 5. Sound wave attenuating apparatus according to any preceding claim, wherein the unit communicates with the sound wave passage through an opening or openings with which baffles are asso- 75 ciated for the purpose set forth. 6. Sound wave attenuating apparatus according to claim 4, wherein the unit is immediately adjacent the sound wave passage and communicates therewith 80 through a large number of small perforations formed in the wall of the said passage. 7. Sound wave attenuating apparatus according to claim 6, wherein the wall of 85 the sound wave passage is perforated throughout the entire longitudinal extent of the unit along the passage. 8. Sound wave attenuating apparatus according to claim 6 or 7, wherein the 90 said perforations are approximately 1/16th inch across and are spaced apart approximately 1/4th inch from centre to centre. 9. Sound wave attenuating apparatus according to any preceding claim, 95 wherein the wall of the sound wave passage adjacent the unit is made up of a plurality of relatively immovable perforated layers, with the openings in one layer larger than those in another and 100 with the unit communicating with the passage through the said openings. 10. Sound wave attenuating apparatus according to claim 9, wherein the centre to centre spacing of the openings in one 105 layer is greater than that of another. 11. Sound wave attenuating apparatus according to any preceding claim, wherein the apparatus comprises a plurality of chambers. 110 12. Sound wave attenuating apparatus according to claim 11, wherein the chambers are intercommunicating and the sound wave passage communicates directly with one or more chambers. 115 13. Sound wave attenuating apparatus according to claim 1 or 2, comprising a sound wave passage and a plurality of resonance chambers of different sizes independently connected therewith. 120 14. Sound wave attenuating apparatus according to any of claims 11 to 13, wherein the openings in the wall between the sound wave passage and the chambers are of different sizes whereby the sound 125 wave passage communicates with one or more chambers through a plurality of larger openings and with another or others through a plurality of smaller openings. 130 15. Sound wave attenuating apparatus 417,935 9 according to any of claims 11 to 14, a series-compound resonance unit in which the sound wave passage is of a larger cross section in one portion than in another and communicates with one or more chambers at a zone of larger 5 cross section and with another or others at a zone of smaller cross section. 16. Sound wave attenuating apparatus according to any preceding claim, comprising multiple-compound and series- 10 compound resonance units communicating with a sound wave passage. 17. Sound wave attenuating apparatus according to any preceding claim, having a tubular sound wave passage and a sur- 15 rounding shell with the chamber or resonance unit disposed between the passage and the shell. 18. In combination with the exhaust system of an internal combustion engine, 20 apparatus according to any preceding claim, the sound wave passage of said apparatus forming a part of the exhaust pipe of said engine. 19. A sound wave attenuating device 25 for use on internal combustion engines, comprising a tube adapted to be connected to and form part of the exhaust pipe, and a complex multiple-compound 30 resonance unit in acoustic communication with said tube the acoustic communication of each component unit of said resonance unit being effected at a point adjacent a node of the respective sound 35 wave to whose frequency the component unit is tuned. 20. A sound wave attenuating device for use on internal combustion engines, comprising a tube adapted to be con- 40 nected to and form part of the exhaust pipe, and acoustic communication with said tube the acoustic communication of said resonance unit being effected at a point adjacent a node of the respective sound 45 wave to whose frequency the component unit is tuned. 21. A sound wave attenuating device for use on internal combustion engines, comprising a tube adapted to be con- 50 nected to and form part of the exhaust pipe, and a multiple-compound resonance unit in acoustic communication with said tube the acoustic communication of each 55 component unit of said resonance unit being effected at a point adjacent a node of the respective sound wave to whose frequency the component unit is tuned. 22. Sound wave attenuating apparatus 60 substantially as described with reference to Figures 1 and 2 of the accompanying drawings. 23. Sound wave attenuating apparatus substantially as described with reference 65 to Figure 4 of the accompanying drawings. 24. Sound wave attenuating apparatus substantially as described with reference to Figure 5 of the accompanying 70 drawings. 25. Sound wave attenuating apparatus substantially as described with reference to Figure 6 of the accompanying drawings. 75 26. Sound wave attenuating apparatus substantially as described with reference to Figure 7 of the accompanying drawings. Dated this 10th day of April, 1933. MARKS & CLERK. Redhill: Printed for His Majesty's Stationery Office, by Love & Malcomson, Ltd.—1934. | ||