Multilayer Nonwoven Sound Absorber for Thin Low-Frequency Damping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multilayer sound absorbers fail to effectively absorb low-frequency sound between 400 and 1250 Hz while maintaining a limited product thickness, which is crucial in the automotive industry, especially in e-mobility where tire rolling noise is prominent in this frequency range.
Innovation Solution
A multilayer sound absorber comprising at least two individual flow-resistant nonwoven layers with increasing flow resistance in the direction of sound penetration, where each layer has a flow resistance between 300 Pa s/m and 1800 Pa s/m, and the difference in flow resistance between layers is optimized to enhance sound absorption in the low-frequency range without increasing overall thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the sound absorber is increased to improve low-frequency sound absorption, then the sound absorption in the low-frequency range (400-1250 Hz) is improved, but the product thickness increases which is not acceptable in applications with limited installation space
Solution Approach 1:
The flow-resistant nonwoven is divided into multiple individual layers (at least two) with different flow resistance values. Each layer is arranged in sequence in the direction of sound wave penetration, creating a gradient structure that segments the sound absorption function across multiple interfaces rather than relying on a single thick layer.
Solution Approach 2:
Different regions (layers) of the nonwoven structure are assigned different flow resistance properties. The flow resistance increases from the first layer (300-1800 Pa s/m) to the second layer (300-1800 Pa s/m), creating local quality variations that optimize sound absorption at different depths within the limited thickness.
2Reliability
If the flow resistance is increased to improve sound absorption, then the sound absorption performance is improved, but the product thickness must also be increased which limits installation possibilities
Solution Approach 1:
The flow resistance is made dynamic across the layers rather than uniform. By arranging layers with increasing flow resistance (300-1800 Pa s/m for the first layer, 300-1800 Pa s/m for the second layer) in the direction of sound penetration, the structure adapts to different sound frequencies at different depths, achieving enhanced low-frequency absorption without proportional thickness increase.
3Reliability
If a single layer with high flow resistance is used to achieve sound absorption, then the sound absorption is improved, but the complexity of achieving optimal performance across multiple frequencies increases
Solution Approach 1:
The single-layer approach is segmented into multiple layers, each with specific flow resistance values within the 300-1800 Pa s/m range. This segmentation simplifies the overall design by providing a systematic approach to achieving broadband sound absorption through standardized layer configurations rather than requiring complex single-layer structures.
Solution Approach 2:
The sound absorber uses a composite structure of multiple nonwoven layers with different flow resistance characteristics. This composite approach combines materials with complementary properties to achieve superior sound absorption performance across multiple frequency ranges while maintaining a manageable structural complexity.
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
Significantly improved sound absorption in the low-frequency range and even at high frequencies above 4000 Hz is achieved while maintaining the same product thickness, making it suitable for applications in the automotive sector and building acoustics.
Implementation Method 1
a flow-resistant nonwoven (3) comprising at least two individual flow-resistant layers (5, 6), wherein the individual flow-resistant layers (5, 6) are arranged one above the other in a direction of penetration (2) of the sound waves to be absorbed
Data Source
AI summary
The invention relates to a multilayer sound absorber comprising a flow-resistant nonwoven with at least two individual flow-resistant layers, wherein the individual flow-resistant layers are arranged one above the other in a direction of penetration of the sound waves to be absorbed and each has a flow resistance between 300 Pa s/m and 1800 Pa s/m, preferably between 400 Pa s/m and 1500 Pa s/m, wherein the flow resistance of the respective individual flow-resistant layer increases from individual flow-resistant layer to individual flow-resistant layer in the direction of penetration. The invention also relates to a method for manufacturing the multilayer sound absorber according to the invention and to a use of the multilayer sound absorber according to the invention for sound absorption in the automotive sector, as well as in the field of building and room acoustics.