Helmholtz Sound Absorber With Split Resonance Chambers
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Solution Overview
Problem
Existing Helmholtz resonators with low loss coefficients in two-degree-of-freedom systems experience a significant reduction in sound absorption coefficient between their absorption peaks, necessitating additional damping materials to mitigate this issue.
Innovation Solution
A sound absorption device with a configuration that includes a first plate, a second plate facing the first plate, a frame connecting both, and a third plate supported within the frame to vibrate, forming separate internal spaces with varying vibration speeds, allowing for a combination of one-degree-of-freedom and two-degree-of-freedom sound absorption characteristics without additional damping materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a Helmholtz resonator of a two-degree-of-freedom system is used to widen the sound absorption band, then the sound absorption characteristics have two separated peaks, but the sound absorption coefficient in the band between the two peaks is significantly reduced
Solution Approach 1:
The elastic plate is divided into multiple regions with different loss coefficients. The first region has a first loss coefficient and the second region has a second loss coefficient different from the first. This local differentiation allows each region to contribute differently to sound absorption, maintaining high absorption coefficients across the entire frequency band including between peaks.
Solution Approach 2:
The elastic plate is constructed as a composite structure with multiple regions having different material properties or structural characteristics that result in different loss coefficients. This composite approach enables the plate to simultaneously provide the necessary elasticity for two-degree-of-freedom resonance while incorporating varying damping characteristics to suppress the dip between absorption peaks.
2Reliability
If damping material is attached to the elastic plate to suppress reduction in sound absorption coefficient between peaks, then the sound absorption coefficient between peaks is improved, but the device complexity increases
Solution Approach 1:
The damping function is merged into the elastic plate itself by creating regions with different loss coefficients. Instead of attaching separate damping materials to the elastic plate, the plate is designed with inherent regional variations in damping properties, integrating both structural and damping functions into a single component.
Solution Approach 2:
The elastic plate serves dual purposes: providing the necessary elasticity for resonance and providing differential damping through its regions with different loss coefficients. The plate self-regulates the sound absorption characteristics across different frequency bands without requiring external damping materials or additional components.
3Device complexity
If a Helmholtz resonator of a one-degree-of-freedom system is used, then the structure is simple, but the sound absorption characteristics are unimodal with limited band width
Solution Approach 1:
The internal space is separated into a first space and a second space by the elastic plate, creating a two-degree-of-freedom system. This segmentation allows independent vibration modes in each space, generating two separated absorption peaks and widening the overall sound absorption band while maintaining structural simplicity.
Solution Approach 2:
The elastic plate is designed to vibrate with different vibration speeds in different regions: a first vibration speed in the first region and a second vibration speed in the second region. This dynamic behavior enables the system to achieve two-degree-of-freedom sound absorption characteristics without complex mechanical structures.
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 device achieves a wider frequency band with high sound absorption coefficients and reduced dips between peaks, improving sound absorption performance compared to traditional resonators.
Implementation Method 1
The Helmholtz resonator generates resonance in the internal space due to a sound incident via the sound hole
Implementation Method 2
The Helmholtz resonator generates resonance in the internal space due to a sound incident via the sound hole, thereby making it possible to attenuate the vibration energy of the incident sound at a resonance frequency
Data Source
AI summary
According to one embodiment, a sound absorption device includes: a first plate having a plurality of first holes; a second plate facing the first plate in a first direction; a first frame connecting the first plate and the second plate; and a third plate supported by the first frame so as to vibrate in the first direction within the first frame. A first space is formed in the first frame between the first plate and the third plate. A second space is formed in the first frame between the second plate and the third plate. The third plate includes a first portion and a second portion, the second portion having a higher vibration speed than the first portion.