Acoustics – Sound-modifying means – Sound absorbing panels
Patent
1993-04-13
1995-05-09
Blankenship, Howard B.
Acoustics
Sound-modifying means
Sound absorbing panels
181294, 181210, E04B 182
Patent
active
054142326
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to noise attenuation panels and is particularly, although not exclusively, concerned with noise attenuation panels for use in the attenuation of noise in aero engines.
DESCRIPTION OF THE BACKGROUND ART
In patent application publication GB-A- 2223448 there is disclosed a noise attenuation panel having a backing component part, a facing component part and a cellular component part having a multiplicity of open-ended juxtaposed cells, the backing component part extending across the ends of the cells of the cellular component part at the rear thereof and the facing component part extending across the ends of the cells of the cellular component part at the front thereof. In addition, the facing component part comprises or includes an outer facing sheet which is made of a porous permeable thermoplastics material. Preferably, the porous permeable thermoplastics material is produced by powder sintering of a thermoplastics materials.
In one embodiment of the invention described in GB-A-2223448, the cellular component part comprises a single cellular element having wall portions which extend across the element from the front face thereof to the rear face thereof and which provide bounding surfaces for an array of open-ended juxtaposed cells.
In another embodiment of the invention described in GB-A-2223448, the cellular component part is sub-divided into a front cellular element and a rear cellular element positioned to the rear of the front cellular element with a septum element extending between the two cellular elements. Each cellular element has wall portions which extend across the element from the front face thereof to the rear face thereof and which provide bounding surfaces for an array of open-ended juxtaposed cells.
While the panel disclosed in GB-A-2223448 has been found to be successful for use in aero engine environments, drawbacks may be found in using a cellular component part formed as a single cellular element or as two cellular elements in which the element or each element is formed as described.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a noise attenuation panel comprising a first cellular component part which has a front face and a rear face and which has wall portions which extend across the first cellular component part from the front face to the rear face and which provide bounding surfaces for an array of cells, a second cellular component part which has a front face and a rear face and which is in the form of an open-celled structure, a backing component part which is secured to or adjoins the rear face of one of the cellular component parts, the front face of which is secured to or adjoins the rear face of the other cellular component part and a facing component part which is secured to or adjoins the front face of the other cellular component part.
By "open-celled structure" is meant a cellular structure having a multiplicity of intercommunicating cells obtained by aggregation of particulate material or by the displacement of material by a dispersion or like technique from a body of material in liquid phase followed by a solidifying step.
In one embodiment of the invention hereinafter to be described, the wall portions of the first cellular component part provide bounding surfaces for a multiplicity of open ended juxtaposed cells which terminate in open ends at the front and rear faces of the first cellular component part.
The wall portions of the first cellular component part may be made from an impermeable material which may be a non-porous impermeable thermoplastics material. Alternatively, the wall portions of the first cellular component part may be made of a porous permeable thermoplastics material.
In an embodiment of the invention hereinafter to be described the second cellular component part is made of a porous permeable thermoplastics material. Preferably, the porous permeable thermoplastics material is produced by powder sintering a thermoplastics material.
The secon
REFERENCES:
patent: 3868297 (1975-02-01), Jamison et al.
patent: 4088723 (1978-05-01), Norton
patent: 4235303 (1980-11-01), Dhoore et al.
patent: 4671841 (1987-06-01), Stephens
Blankenship Howard B.
Dang Khanh
Short Brothers PLC
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