Porous Acoustic Panel Laminate for Low-Frequency Noise Absorption
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Solution Overview
Problem
Acoustic attenuation panels used in space launchers and other structures face challenges in effectively reducing noise in low and medium frequency ranges, with existing solutions having low sound absorption coefficients at frequencies like 63 Hz and 125 Hz, and requiring improvements that do not compromise performance at higher frequencies or increase weight.
Innovation Solution
An acoustic attenuation panel comprising a melamine resin foam main layer with specific density and porosity, a fabric coating layer, and a thermoplastic adhesive film with through holes, assembled via lamination and thermal treatment to enhance sound absorption and airflow resistance, while maintaining lightweight and thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If panel thickness is increased to improve low frequency absorption, then sound absorption at low frequencies improves, but weight increases
Solution Approach 1:
The patent modifies the airflow resistance parameter of the foam by introducing defects rather than increasing thickness. This allows achieving improved low frequency absorption (coefficient ≥ 0.3 at 63 Hz) while maintaining a thin panel design (10 cm), thereby avoiding weight increase.
Solution Approach 2:
The patent optimizes the porous structure of the foam by creating a specific distribution of open and closed cells, bridges, and nodules. This optimized porous structure enhances low frequency absorption through modified airflow resistance without requiring increased panel thickness, thus preventing weight gain.
2Measurement precision
If dense foam material is used to improve sound absorption, then acoustic performance improves, but airflow resistance increases reducing pressure equalization capability
Solution Approach 1:
The patent segments the foam structure into open-cell regions and closed-cell regions, connected by bridges and nodules. This segmentation allows the material to provide both sound absorption (through open cells) and air permeability (through closed cells and bridges), resolving the contradiction between acoustic performance and pressure equalization capability.
Solution Approach 2:
The patent applies local quality by creating different microstructures in different regions of the foam. Open-cell regions provide sound absorption while closed-cell regions and bridges maintain air permeability. This local differentiation allows the panel to achieve both high sound absorption coefficient and sufficient airflow resistance for pressure equalization.
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 panel achieves improved sound absorption coefficients of at least 0.3 at 63 Hz and 0.55 at 125 Hz, reducing noise levels by 2 dB in critical frequency bands and maintaining performance across frequencies, while being 30% lighter than previous designs, thus enhancing payload capacity and structural integrity.
Implementation Method 1
a first layer, so-called main layer, made of a porous material
Implementation Method 2
The aim of the main layer and the coating layer is to contribute to the sound absorption of the panel
Implementation Method 3
the coating layer is air permeable... to make it possible to depressurise the air trapped in the cells or cavities of the main layer
Implementation Method 4
the main layer and the coating layer being assembled one with the other by an adhesive film that is disposed at the interface between the main layer and the coating layer
Implementation Method 5
assembled via lamination and thermal treatment
Data Source
AI summary
An acoustic attenuation panel including: a main layer made of a porous material and having two opposite faces; a coating layer arranged on one of the two faces of the main layer; an adhesive film, arranged at the interface between the main layer and the coating layer to assemble same. The main layer is a body made of melamine resin foam having a density between 6 and 6.8 kg/m3 and a porosity rate between 0.978 and 0.984; the coating layer is a fabric with a density between 484 and 526 kg/m3 and a porosity rate between 0.771 and 0.817; the adhesive film is a film made of a thermoplastic material provided with holes passing through and having a surface density between 40 g/m2 and 56 g/m2.