Cellular Soundproofing Coating for Low-Frequency Noise
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Solution Overview
Problem
Conventional acoustic panels with cellular structures are ineffective at handling low-frequency sound waves due to their small cell sizes, which require thick panels to absorb these frequencies, making them unsuitable for aeronautical applications where low-frequency noise is prevalent.
Innovation Solution
A soundproofing coating with a cellular structure formed by joining transversely oriented strips, creating a configuration of first and second cavities that function as quarter-wave and Helmholtz resonators, allowing for the absorption of lower frequencies while maintaining structural integrity and being producible on an industrial scale.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional small-sized cellular structures are used in acoustic panels, then the panel thickness can be reduced, but the ability to absorb low-frequency sound waves is lost
Solution Approach 1:
The patent implements a nested cellular structure where first cavities are positioned within second cavities, creating a multi-level nested arrangement. This nesting allows the panel to achieve effective low-frequency sound absorption with reduced thickness by utilizing the three-dimensional space efficiently, with inner cavities providing additional resonance paths without increasing overall panel dimensions.
Solution Approach 2:
The invention transitions from conventional two-dimensional cellular arrangements to a three-dimensional nested configuration. By stacking multiple layers of cavities in the thickness direction and positioning first cavities within second cavities, the design exploits the third dimension to achieve low-frequency absorption capabilities traditionally requiring much thicker panels.
2Reliability
If large-volume cells are used to absorb low frequencies, then low-frequency sound absorption improves, but the panel becomes very thick and unsuitable for aeronautical applications
Solution Approach 1:
Instead of using single large-volume cells that increase panel thickness, the patent nests first cavities within second cavities. This creates multiple resonance chambers in a compact arrangement, achieving the equivalent acoustic volume needed for low-frequency absorption without proportionally increasing panel thickness.
Solution Approach 2:
The invention segments the acoustic absorption function into multiple smaller cavities (first and second cavities) that work together in a nested configuration. Rather than relying on a single large cell, multiple segmented cavities provide distributed resonance paths that achieve low-frequency absorption with compact overall dimensions.
3Reliability
If curved S-shaped cells are used to lengthen cell paths for low-frequency absorption, then low-frequency capability improves, but mechanical strength deteriorates and manufacturing difficulty increases
Solution Approach 1:
The patent divides the cellular structure into discrete first cavities and second cavities with simplified geometries, joined through shared walls. This segmentation into regular, manufacturable units maintains mechanical strength while achieving extended acoustic paths through the nested arrangement, avoiding the need for complex curved S-shaped cells.
Solution Approach 2:
Instead of lengthening cell paths through complex in-plane curves, the invention extends the acoustic path by utilizing the thickness dimension through nested cavities. The first cavities positioned within second cavities create extended resonance paths in the vertical direction, maintaining simpler in-plane geometries that preserve mechanical strength and ease of manufacture.
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 coating effectively handles low-frequency sound waves with improved mechanical strength and reduced thickness, expanding the frequency range it can absorb compared to conventional panels, making it suitable for aeronautical applications.
Implementation Method 1
The first strip and the second strip are configured so that each structure exhibits successively and repeating in the longitudinal direction: a first cavity extending between the first face and the second face and open at the first face... a second cavity, which has a cross section that increases progressively between the first face and the second face and which is closed at the first face and at the second face of the coating by the closure sheet
Implementation Method 2
a first joining of two walls belonging respectively to the first strip and to the second strip in contact with one another over part of the thickness of the coating so that a passage is created between the first cavity and a second cavity
Data Source
AI summary
A soundproofing coating with a cellular structure having several structures connected in a transverse direction, each formed by connecting a first longitudinal strip with a second longitudinal strip. Each structure has, successively in the longitudinal direction, 1) a first cavity, the cross-section of which narrows gradually in the thickness of the coating until it closes, 2) a first connection of two walls, respectively of the first strip and the second strip, in contact with each other over part of the thickness of the coating, which provides a passage between the first cavity and a second cavity that thus form a Helmholtz resonator, 3) the second cavity, the cross-section of which gradually increases in the thickness of the coating and which is closed by a closing sheet, and 4) a second connection of two walls.