Aircraft Acoustic Panel Structure for Low-Frequency Noise Absorption
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Solution Overview
Problem
Existing honeycomb acoustic panels struggle to effectively absorb low-frequency sound waves due to the need for large cavities, which results in thick panels unsuitable for aeronautical applications.
Innovation Solution
A sound insulation device with a honeycomb structure comprising a first perforated sheet, a second solid sheet, and a coating formed by joining longitudinal strips to create quarter-wave and Helmholtz cavities, along with sacrificial portions to maintain acoustic permeability and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If large-diameter propulsion systems are used to generate low-frequency acoustic waves, then the acoustic treatment requirement is improved, but the panel thickness increases making it unsuitable for aeronautical applications
Solution Approach 1:
The invention divides the acoustic treatment function into two distinct cavity types: quarter-wave cavities for low-frequency resonance and Helmholtz cavities for broadband absorption. This segmentation allows each cavity type to be optimized for its specific function, achieving effective low-frequency noise attenuation without requiring uniformly thick panels throughout, thus resolving the contradiction between noise treatment effectiveness and panel thickness for aeronautical applications.
Solution Approach 2:
The patent implements local quality by creating regions with different cavity characteristics - quarter-wave cavities positioned to target specific low-frequency ranges and Helmholtz cavities for broader frequency absorption. This localized optimization allows the panel to achieve effective acoustic treatment at specific frequencies while maintaining thinner overall panel thickness, making it suitable for aeronautical applications where weight and thickness are critical constraints.
2Object-affected harmful factors
If the first sheet is pierced to make it permeable to acoustic waves, then the acoustic absorption is improved, but the Helmholtz cavity structure is damaged
Solution Approach 1:
The invention introduces sacrificial portions as intermediary elements that are specifically designed to be removed or pierced during the perforation process. These sacrificial portions act as mediators that allow the first sheet to be pierced for acoustic permeability while protecting the critical Helmholtz cavity structure from damage. The sacrificial portions are positioned and dimensioned to be selectively removed without compromising the integrity of the Helmholtz cavities, thus resolving the contradiction between acoustic wave permeability and cavity integrity.
3Strength
If conventional honeycomb structures are used, then the structural rigidity is maintained, but the low-frequency acoustic absorption is insufficient
Solution Approach 1:
The patent creates a composite acoustic panel structure that combines the rigid honeycomb framework with two types of acoustic cavities (quarter-wave and Helmholtz). The honeycomb structure provides the necessary structural rigidity and mechanical strength, while the integrated cavities provide specialized acoustic absorption functions. This composite approach allows the panel to simultaneously achieve structural integrity and effective low-frequency noise attenuation, resolving the contradiction between strength and acoustic performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device efficiently treats low-frequency sound waves while maintaining structural qualities and industrial feasibility, avoiding damage to resonators during perforation and optimizing mass and thickness.
Implementation Method 1
at least one cavity, open at the level of the first sheet and whose section gradually narrows between the first sheet and the second sheet until the said cavity is closed, called the quarter-wave cavity
Implementation Method 2
a first joining of two walls, respectively of the first band and the second band, in contact with each other, so that a passage is provided between said cavity and another cavity, said other cavity, called the Helmholtz cavity
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to an acoustic insulation device, at least one cavity (9), called quarter-wave cavity, a first joining of two walls (4-1, 5-1), respectively of the first strip (4) and of the second strip (5), in contact with each other, so that a passage (10) is provided between said cavity (9) and another cavity (8), said other cavity (8), called Helmholtz cavity, closed by a closing edge, a second joining of two walls (4-2, 5-2), respectively of the first strip (4) and of the second strip (5), in contact with each other, each of the walls (4-1, 5-1; 4-2, 5-2) of said first and second joinings comprising a portion disposed along said closing edge of the Helmholtz cavity (8), called sacrificial portion and forming end of the coating (1).