Porous Fibrous Soundproof Structure with Density Gradient
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Solution Overview
Problem
Existing soundproof structures are ineffective in attenuating sound waves across a wide frequency band, as they are designed to efficiently absorb sound only in specific frequency ranges due to the arrangement of high and low density layers.
Innovation Solution
A soundproof structure comprising a porous fibrous body with a surface layer and a propagation layer, where the propagation layer has a higher density than the surface layer, and the average fiber diameter is between 0.5 μm and 5 μm, allowing for efficient sound wave attenuation across a wide frequency band by converting sound energy into heat through friction within the fibrous body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high density layer is disposed on the sound source side and a low density layer on the opposite side, then sound waves can be efficiently attenuated in a specific frequency band, but the soundproof structure cannot efficiently attenuate sound waves in a wide frequency band
Solution Approach 1:
The invention applies local quality by creating a density gradient within the porous fibrous body, where the density increases from the sound incident surface toward the back surface. This continuous variation in density (local property) allows different regions to handle different frequency ranges, enabling wide-band sound attenuation while maintaining efficient attenuation in specific frequency bands.
Solution Approach 2:
The invention changes the density parameter continuously throughout the porous fibrous body structure. By arranging fibers with varying densities from the incident surface to the back surface, the structure can interact with sound waves of different frequencies effectively, resolving the contradiction between specialized frequency attenuation and wide-frequency adaptability.
2Reliability
If the porous body uses fibers with smaller diameter, then friction between fibers and air increases improving sound attenuation, but the manufacturing complexity and cost increase
Solution Approach 1:
The invention specifies an optimal fiber diameter range (0.5 μm to 5 μm) that balances sound attenuation performance with manufacturing feasibility. This parameter optimization ensures sufficient friction between fibers and air for effective sound attenuation while avoiding excessive manufacturing complexity associated with ultra-fine fibers.
Solution Approach 2:
The invention varies fiber diameter locally within different density regions of the porous body. By controlling fiber diameter distribution alongside density gradient, the structure achieves effective sound attenuation across wide frequencies while maintaining manufacturability in each local region.
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 structure effectively attenuates sound waves in a wide frequency band, providing improved sound absorption characteristics, with a sound absorption coefficient of 55% or more within the range of 350 Hz to 2000 Hz, reducing noise in various applications such as vehicles, buildings, and electrical appliances.
Implementation Method 1
friction occurs between the fibers or the foam resin and the air, and the sound waves are attenuated by converting energy of sound into heat
Implementation Method 2
an air layer disposed opposite a sound source with respect to the plate resonates with sound waves. Due to the resonance of the air layer, air inside the through hole strongly vibrates, friction occurs, sound energy is converted into heat
Data Source
AI summary
A soundproof structure includes a porous fibrous body that attenuates incident sound waves, wherein the fibrous body is formed of fibers having an average fiber diameter of 0.5 μm or more and 5 μm or less, and includes a surface layer on which the sound waves are incident and a propagation layer that is stacked with the surface layer and that propagates the sound waves from the surface layer, and wherein the propagation layer includes a high density layer having a density higher than a density of the surface layer.