Broadband Sound Absorber Using Distributed Helmholtz Resonators
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional sound absorbers are ineffective in attenuating low-frequency noise over a large frequency range due to their bulky structure and narrow operation bandwidth, and existing acoustic metamaterial-based solutions often rely on unreliable membrane structures or increased lateral dimensions.
Innovation Solution
The use of distributed Helmholtz resonators with extended necks, arranged in a checkerboard fashion with varying neck lengths or diameters, provides a compact sound absorber that achieves broadband noise reduction by shifting resonance frequencies to lower ranges and allowing for thin thickness designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional sound absorbers are used, then they provide noise reduction at resonance frequency, but they suffer from narrow operation bandwidth and bulky structure
Solution Approach 1:
The sound absorber is divided into multiple independent resonant units (Helmholtz resonators with extended necks) arranged in an array. Each unit can be designed with different geometric parameters to target different frequency ranges, enabling the overall structure to achieve broadband absorption through segmentation of the frequency spectrum.
Solution Approach 2:
Different regions of the sound absorber feature resonant units with locally optimized geometric parameters (neck length, cavity volume, opening area). This local variation in quality allows each region to resonate at different frequencies, collectively covering a broad frequency spectrum while maintaining compact dimensions.
2Ease of manufacture
If resonant-type absorbers are used, then they achieve good noise reduction at resonance frequency, but they require bulky structure for low-frequency attenuation
Solution Approach 1:
The patent introduces extended necks that protrude from the main absorber body in a direction perpendicular to the sound propagation path. This dimensional extension allows the resonant frequency to be tuned to lower values without increasing the thickness of the absorber body, effectively decoupling the resonance frequency control from the overall volume constraint.
Solution Approach 2:
The extended necks are integrated into the overall absorber structure with the cylindrical cores nested within the perforated plate framework. This nested arrangement allows the extended necks to provide low-frequency resonance capability while the compact cylindrical cores maintain the thin profile of the overall absorber.
3Volume of moving object
If membrane structures are used in acoustic metamaterials, then deep-subwavelength absorption is achieved, but reliability decreases
Solution Approach 1:
The patent replaces fragile membrane structures with robust solid components (perforated plates and cylindrical cores). These solid structures are mechanically stronger and more reliable while achieving similar or better acoustic performance through the extended neck design that enables low-frequency resonance without membranes.
Solution Approach 2:
The sound absorber employs a composite structure combining perforated plates with extended necks and cylindrical cores. This composite design integrates multiple functional elements (resonance control, structural support, acoustic flow management) into a single robust system that eliminates the need for unreliable membrane components.
4Volume of moving object
If coiled structures are used to reduce thickness, then lateral dimensions increase
Solution Approach 1:
Instead of coiling the resonator structures laterally to reduce thickness (which increases footprint), the patent extends the necks in the thickness direction. This dimensional reorientation allows thickness reduction to be achieved without sacrificing lateral space, as the extended necks utilize the thickness dimension for resonance tuning rather than lateral coiling.
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
This configuration results in a thin, efficient sound absorber with quasi-perfect absorption coefficients across a wide frequency band, effectively addressing the limitations of conventional absorbers by achieving broadband noise attenuation with a compact form factor.
Implementation Method 1
distributed absorption units each having an extended neck. The absorption units can be, for example, Helmholtz resonators with extended necks (HRENs)
Implementation Method 2
Resonant-type absorbers possess good noise reduction performance at the resonance frequency
Implementation Method 3
Each absorption unit of the plurality of absorption units can achieve a peak absorption of incident acoustic energy at its resonance frequency
Data Source
AI summary
Sound absorbers using distributed absorption units each having an extended neck are provided. The absorption units can be, for example, Helmholtz resonators with extended neck (HRENs). The absorption units can be distributed in a lateral fashion, for example, in a checkerboard fashion with laterally, non-diagonally adjacent units having a different extended neck length and/or diameter. Each absorption unit can be, for example, a cylinder-structure core sandwiched between a back wall and a perforated plate.