Elastic Sheet Sound Reflection Structure for 1500-2500 Hz
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Solution Overview
Problem
Existing soundproofing materials, particularly acoustic metamaterials, fail to exhibit sufficient soundproofing performance over a wide frequency range of 2000 Hz or less, and specifically in the critical range of 1500 to 2500 Hz, which is sensitive to human hearing.
Innovation Solution
A sound-reflecting structure is designed with a sheet having elasticity and a support portion that partitions the sheet into partition portions, where the surface rigidity and density satisfy a specific relationship, and is disposed separated from the substrate, utilizing both mass and rigidity laws to enhance sound reflection in the 1500 to 2500 Hz range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional soundproofing materials are used to achieve soundproofing performance, then sound absorption and insulation are improved, but weight increases
Solution Approach 1:
The invention uses composite materials combining metal foam (providing sound absorption and damping) with plastic resin (providing structural support and sound reflection). This composite structure achieves effective soundproofing performance while maintaining lightweight characteristics, resolving the contradiction between soundproofing effectiveness and weight reduction.
Solution Approach 2:
The soundproofing cover employs different materials with different properties in different regions: metal foam in areas requiring sound absorption and damping, and plastic resin in areas requiring sound reflection and structural support. This localized material selection optimizes soundproofing performance across different frequency ranges without uniformly increasing weight.
2Weight of moving object
If acoustic metamaterials are used to achieve lightweight soundproofing, then weight is reduced, but soundproofing performance over wide frequency range deteriorates
Solution Approach 1:
Rather than using a single acoustic metamaterial, the invention combines multiple materials (metal foam and plastic resin) with complementary soundproofing mechanisms. The metal foam provides low-frequency sound absorption through its cellular structure, while the plastic resin provides mid-to-high frequency sound reflection, achieving wide frequency range coverage while maintaining lightweight design.
Solution Approach 2:
The soundproofing cover is divided into functionally distinct regions: a sound absorbing/damping portion made of metal foam and a sound reflecting portion made of plastic resin. This segmentation allows each material to optimize its performance in its designated frequency range, collectively achieving broad-spectrum soundproofing without the weight penalty of conventional homogeneous materials.
3Reliability
If sound reflecting portion is added to improve sound reflection, then sound reflection performance is improved, but device complexity increases
Solution Approach 1:
The sound reflecting portion is integrated into the same cover structure as the sound absorbing portion, using a different material (plastic resin) rather than adding a separate component. This composite material approach provides sound reflection functionality while maintaining a unified, relatively simple overall structure, avoiding excessive complexity increase.
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 achieves significant improvement in sound reflection performance in the 1500 to 2500 Hz range, even with a lightweight design, by controlling the surface rigidity and density of the sheet to meet a predetermined relationship, thereby enhancing sound reflection effects.
Implementation Method 1
when a sound wave of a frequency on a single wall made of a homogeneous material is vertically incident, a value of transmission loss (TL) by the single wall is calculated as TL ≈ 20 log 10 (m·f)-43 [dB] using a frequency (f) and a surface density (m) of the single wall (mass law)
Implementation Method 2
utilizing both mass and rigidity laws to enhance sound reflection in the 1500 to 2500 Hz range
Implementation Method 3
a sound-reflecting material disposed on the substrate at a position separated from the substrate, wherein the sound-reflecting material includes a sheet having elasticity
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
To provide a means capable of further improving the sound-reflecting performance in a frequency range of 1500 to 2500 Hz. A sound-reflecting material including a sheet having elasticity, and a support portion partitioning the sheet into a partition portion while supporting the sheet is configured so that a surface rigidity (k) of the sheet and a surface density (m) of the sheet in the partition portion satisfy a relationship of the following Expression 1. Further, the sound-reflecting material is disposed on a substrate so that the sheet is separated from the substrate to configure a sound-reflecting structure: 12πkm>900Hz