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EP-4641560-B1 - ACOUSTIC ATTENUATION PANEL

EP4641560B1EP 4641560 B1EP4641560 B1EP 4641560B1EP-4641560-B1

Inventors

  • DHANAPAL, Karthikeyan

Dates

Publication Date
20260513
Application Date
20250411

Claims (15)

  1. An acoustic attenuation panel to reduce noise that emanates from a source, the acoustic attenuation panel comprising: a porous face layer (31); a back layer (32); an intermediate section (40) positioned between the face layer (31) and the back layer (32), the intermediate section (40) comprising: a cellular member (41) comprising a plurality of cavities (42); acoustic metamaterial members (45) positioned in and extending across the cavities (42); and wherein the back layer (32) is configured to be mounted to a surface in proximity to the source; further comprising at least two of the acoustic metamaterial members (45) positioned in the cavities (42); wherein the at least two acoustic metamaterial members (45) in the cavities (42) are spaced apart by a gap.
  2. The acoustic attenuation panel of claim 1, wherein at least one of the acoustic metamaterial members (45) is positioned in each of the cavities (42).
  3. The acoustic attenuation panel of claim 1 or 2, wherein the acoustic metamaterial members (45) are positioned within a central section of the cavities (42) and are spaced away from each of the face layer (31) and the back layer (32).
  4. The acoustic attenuation panel of claim 1, wherein each of the acoustic metamaterial members (45) positioned in the cavities (42) comprise different shapes.
  5. The acoustic attenuation panel of any one of the preceding claims, further comprising a septum (43) that is porous and that extends across the cellular member (41) between the face layer (31) and the back layer (32) and forms an upper section and a lower section of each of the cavities (42).
  6. The acoustic attenuation panel of claim 5, wherein the acoustic metamaterial members (45) are positioned in the upper section and the lower section of the cavities (42).
  7. The acoustic attenuation panel of any one of the preceding claims, wherein the acoustic attenuation panel is mounted on an engine nacelle of an aircraft; and optionally wherein the face layer (31), the back layer (32), and the intermediate section (40) are flexible to enable the acoustic attenuation panel to be mounted on a curved surface of the aircraft.
  8. The acoustic attenuation panel of any one of the preceding claims, wherein the cavities (42) and the acoustic metamaterial members (45) comprise matching polygonal shapes to enable the acoustic metamaterial members (45) to extend across an entirety of the cavities (42).
  9. The acoustic attenuation panel of any one of the preceding claim; wherein the acoustic metamaterial members (45) are constructed from a polymer.
  10. The acoustic attenuation panel of any one of the preceding claims; wherein the cellular member (41) comprises a honeycomb structure.
  11. The acoustic attenuation panel of claim 1; the cellular member (41) comprising: a first side mounted to the porous face layer (31); a second side mounted to the back layer (32); wherein the cavities (42) extend through the cellular member (41) with open faces at the first side and the second side; and acoustic metamaterial members (45) are connected to the cellular member (41) and sized to extend across the cavities (42).
  12. The acoustic attenuation panel of claim 11, wherein the cellular member (41) comprises a honeycomb structure with the cavities (42) comprising a polygonal sectional shape.
  13. The acoustic attenuation panel of claim 11 or 12, wherein the acoustic metamaterial members (45) comprise a matching sectional shape to the cavities (42); or optionally further comprising: the porous face layer (31) and the back layer (32) constructed from one of metals and carbon fibers; and the acoustic attenuation panel constructed from a polymer.
  14. A method of making an acoustic attenuation panel, the method comprising: positioning a cellular member (41) in an orientation to access a plurality of cavities (42), the cellular member (41) comprises a honeycomb structure with the plurality of cavities (42) that extend through the cellular member (41); mounting acoustic metamaterial members (45) in the cavities (42) with outer edges of the acoustic metamaterials contacting against the honeycomb structure; acoustic metamaterial members comprising at least two of the acoustic metamaterial members (45) positioned in the cavities (42); wherein the at least two acoustic metamaterial members (45) in the cavities (42) are spaced apart by a gap; mounting a face layer (31) on a first side of the cellular member (41) with the face layer (31) spaced away from the acoustic metamaterial members (45); and mounting a back layer (32) on a second side of the cellular member (41) with the back layer (32) spaced away from the acoustic metamaterial members (45).
  15. The method of claim 14, further comprising mounting additional acoustic metamaterial members (45) in the cavities (42) of the cellular member (41); or optionally further comprising mounting the back layer (32) to a surface of an aircraft.

Description

TECHNOLOGICAL FIELD The present disclosure relates generally to the field of noise reduction devices and, more specifically, to noise reduction panels that include acoustic metamaterial members. BACKGROUND Noise regulations limit the allowable noise levels for airports. These regulations limit the impact of aircraft noise on communities that are located near the airports. Various federal and local authorities establish the maximum allowable noise for a given time of the day. Normally, allowable noise levels are higher during the daytime and are reduced during evening and nighttime hours. Some airports have microphones installed around their grounds to monitor the noise levels. Monetary fines or other measures can be taken to enforce the regulations. Aircraft are designed to reduce the amount of noise during operation. Some aircraft position noise reduction materials within the engines. However, these materials are relatively heavy and add weight to the aircraft thereby reducing the performance and fuel efficiency of the aircraft. Further, these materials are also relatively thick to particularly target higher frequency noise. These thicker materials are often difficult to design to effectively reduce the overall noise and the noise at certain frequencies. Further, the attachment of thicker materials within the engine can encroach on components of the engine. The thick materials can also interfere with the integration of the engine core mounted accessories. Noise reduction measures are also used in other environments. One example includes a manufacturing facility that includes industrial equipment that produce high noise levels. Noise attenuation devices are used on the equipment and/or in the area surrounding the equipment in an attempt to reduce the noise levels. However, existing noise reduction measures have drawbacks and are not effective in attenuating the noise and/or have additional issues that make their use impractical. Therefore, there is a need for noise reduction devices that attenuate noise and are able to be effectively designed and manufactured. For aircraft use, the devices should be configured to allow for use with an aircraft engine without interfering with the operation and also be relatively light weight. For other applications, the devices should be configured to be mounted in proximity to the source of the noise. Winkler Julian et al: "High fidelity modeling tools for engine liner design and screening of advanced concepts", INTERNATIONAL JOURNAL OF AEROACOUSTICS, vol. 20, no. 5-7, 24 August 2021, in an abstract states that "With aircraft engines trending toward ultra-high bypass ratios, resulting in lower fan pressure ratios, lower fan RPM, and therefore lower blade pass frequency, the aircraft engine liner design space has been dramatically altered. This result is also due to the associated reduction in both the available acoustic treatment area (axial extent) as well as thickness (liner depth). As a consequence, there is current need for novel acoustic liner technologies that are able to meet multiple physical constraints and simultaneously provide enhanced noise attenuation capabilities. In addition, recent advances in additive manufacturing have enabled the consideration of complex liner backing structures that would traditionally be limited to honeycomb cores. This paper provides an overview of engine liner modeling and a description of the key physical mechanisms, with some emphasis on the use of low to high-fidelity tools such as empirical models and commercially available software such as COMSOL, Actran, and PowerFLOW. It is shown that the higher fidelity tools are a critical enabler for the evaluation and construction of future complex liner structures. A systematic study is conducted to predict the acoustic performance of traditional single degree of freedom liners and comparisons are made to experimental data. The effects of grazing flow and bias flow are briefly addressed. Finally, a more advanced structure, a metamaterial, is modeled and the acoustic performance is discussed." CN117456972A in an abstract states that "The invention belongs to the technical field of aviation noise control, and particularly relates to a novel acoustic metamaterial structure for sound absorption, light weight and bearing, the novel acoustic metamaterial structure is formed by a plurality of unit cells through two-dimensional periodic continuation, and each unit cell comprises an upper wall plate (1), a middle wall plate (3) and a lower wall plate (4) which are arranged in parallel at equal intervals; the first vertical plate (2) and the second vertical plate (5) are arranged between the upper wall plate (1) and the lower wall plate (4) in a crossed mode, the upper wall plate (1), the middle wall plate (3), the lower wall plate (4), the first vertical plate (2) and the second vertical plate (5) form eight mounting grids, each mounting grid is internally provided with an eight-corner tetrahedral