Thin Sound Absorbing Body Using Porous Foam and Fibrous Layer
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Solution Overview
Problem
Existing sound absorbing materials struggle to effectively absorb sound waves in the low frequency region due to their thickness and mass per unit area limitations, and they often fail to provide a broad frequency sound absorption across all regions.
Innovation Solution
A thin sound absorbing body composed of a non-woven fabric or laminate with specific properties, including fiber diameters less than 3,000 nm, unit thickness flow resistance between 4.0 E+06 Ns/m^4 and 5.0 E+08 Ns/m^4, bulk density between 70 kg/m^3 and 750 kg/m^3, porosity less than 0.92, and a peak sound absorption of less than 3,000 Hz, utilizing synthetic resin and/or elastomer fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If porous sound absorbing materials are made thin, then the material thickness is reduced, but sound absorption in the low frequency region becomes difficult
Solution Approach 1:
The patent employs a porous foam material as the core sound absorbing structure. The porous structure allows sound waves to penetrate and dissipate energy through friction and viscosity effects within the pores, enabling effective sound absorption even in thin configurations. The specific porosity range (0.7-0.95) is optimized to balance sound penetration and energy dissipation.
Solution Approach 2:
The patent creates a composite structure by combining the porous foam material with a fibrous layer on at least one surface. This composite configuration allows the foam core to handle low frequency absorption while the fibrous surface layer enhances high frequency absorption, achieving broad-spectrum sound absorption in a thin overall structure.
2Reliability
If materials with high mass per unit area are used, then sound absorption in low frequency region improves, but the material becomes thicker and heavier
Solution Approach 1:
The porous foam material provides high sound absorption efficiency without requiring high mass per unit area. The porous structure creates acoustic resistance that dissipates sound energy effectively, replacing the traditional approach of using heavy dense materials. The foam's low density combined with optimized porosity achieves sound absorption performance comparable to or better than traditional heavy materials.
Solution Approach 2:
The composite of porous foam and fibrous layer creates a lightweight alternative to traditional heavy sound absorbing materials. The foam provides the bulk absorption capability while the fibrous layer adds surface absorption, together achieving broad frequency coverage without the mass penalty of conventional materials.
3Reliability
If traditional sound absorbing materials are used, then middle and high frequency sound absorption is achieved, but low frequency sound absorption remains insufficient
Solution Approach 1:
The patent designs a composite structure where the porous foam material serves as the core for low frequency absorption, while a fibrous layer is applied on the surface to enhance high frequency absorption. This multi-layer composite approach enables the single material system to effectively absorb sound across the entire frequency spectrum from low to high frequencies.
Solution Approach 2:
Different regions of the sound absorbing material are assigned different functions: the porous foam core is optimized for low frequency absorption through its cellular structure and porosity, while the surface fibrous layer is optimized for high frequency absorption through its fine fiber structure. This spatial differentiation of functional properties enables broad-spectrum 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 solution provides a thin sound absorbing body that effectively absorbs sound waves across a broad frequency range, including the low frequency region, suitable for use in various applications such as construction materials, motor vehicles, and electrical products.
Implementation Method 1
highly porous materials having connected voids
Implementation Method 2
absorption of sound in the low frequency region is generally difficult
Data Source
AI summary
A sound absorbing body comprises a non-woven fabric or a non-woven fabric laminate, the non-woven fabric or the non-woven fabric laminate comprises a fiber that has an average fiber diameter of less than 3,000 nm, the non-woven fabric or the non-woven fabric laminate has a thickness of less than 10 mm, the non-woven fabric or the non-woven fabric laminate has a unit thickness flow resistance of greater than 4.0 E+06 Ns/m4 and less than 5.0 E+08 Ns/m4, and the non-woven fabric or the non-woven fabric laminate has a bulk density of greater than 70 kg/m3 and less than 750 kg/m3.