Multi-layer acoustic linings
AssigneeROLLS-ROYCE plc
InventorJohn F. Chapman
Life of this patent
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Abstract
A multi-layer acoustic lining, e.g. for a flow duct in a gas turbine aeroengine, includes Helmholtz-type and tube-type resonators sandwiched between backing and facing sheets. In the invention, the ends of the tube-type resonators abut the Helmholtz resonators but are acoustically divided from them by partition means in such a way that the tube-type resonators differ from each other in resonant frequency. Variation of resonant frequency in the tube-type resonators is achieved by variation of their lengths according to which portion of the partition means acoustically divides them from the Helmholtz-type resonators, the partition means being arranged either step-wise or inclinedly between the backing and facing sheets.
Claims10
A multi-layer acoustic lining for a fluid flow duct comprising:
- an impermeable backing layer;
- a sound permeable facing layer spaced from said impermeable backing layer;
- a plurality of Helmholtz resonators sandwiched between said backing layer and said sound permeable facing layer, said plurality of Helmholtz resonators being defined by a first set of resonator compartments, each of which is acoustically coupled to said sound permeable facing layer by a resonator neck means having a cross-sectional area restrictive relative to the cross-sectional area of the resonator compartments of the Helmholtz resonators;
- a plurality of tube-type resonators sandwiched between said backing layer and said facing layer, said plurality of tube-type resonators being defined by a second set of resonator compartments, each of which is acoustically coupled directly to said permeable facing layer;
- and
- partition means providing an acoustic division between at least some of said first set of resonator compartments for said plurality of Helmholtz resonators and said second set of resonator compartments for said plurality of tube-type resonators, said partition means providing at least some of said plurality of tube-type resonators with different resonant frequencies.
Dependencies are inferred from the claim text.