Sound Absorbing Panel with Tuned Resonant Cavities
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Solution Overview
Problem
Existing sound absorber designs face challenges in achieving broadband and high-efficiency acoustic energy absorption over a broad frequency range due to narrow absorption bandwidth and practicality issues, such as impractical thickness and durability problems in airborne sound absorption.
Innovation Solution
A sound absorbing panel with non-uniform openings and space-coiled cavities, where each unit cell is tuned for different frequency ranges, forming a super cell structure that provides multiple resonant modes for broadband absorption within a thinner thickness than conventional designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional Helmholtz resonator or micro-perforated panel designs are used, then high acoustic absorption can be achieved at specific frequencies, but the absorption bandwidth is narrow
Solution Approach 1:
The panel is divided into multiple unit cells, each containing resonators with different geometries (spheres, cylinders, cones) and dimensions. Each unit cell is tuned to absorb sound at different frequencies, and the combination of multiple unit cells creates a broadband absorption effect covering the entire audible range.
Solution Approach 2:
Different regions of the panel have different resonator configurations - varying sizes, shapes, and distributions of resonators are placed in different locations. This local variation in resonator properties allows different frequency ranges to be absorbed at different spatial locations, achieving broadband absorption overall.
2Adaptability or versatility
If the panel thickness is increased to achieve broader frequency ranges, then absorption bandwidth improves, but the device becomes impractically thick
Solution Approach 1:
Instead of increasing thickness to achieve broadband absorption, the invention uses lateral variation in resonator properties across the panel surface. By distributing different types and sizes of resonators horizontally across the panel rather than stacking them vertically, broadband absorption is achieved without increasing panel thickness.
Solution Approach 2:
Multiple resonators of different sizes and types are nested within a compact panel structure. Small resonators are positioned alongside larger ones, and various geometric shapes are arranged to maximize absorption efficiency within the limited thickness constraint.
3Length of stationary object
If uniform tension membranes are used to achieve deep-subwavelength scale, then thin panel design is possible, but fabrication challenges and durability issues arise
Solution Approach 1:
The invention removes the membrane component from the design entirely, replacing it with rigid resonator structures (spheres, cylinders, cones) that are directly attached to the panel backing. This extraction of the membrane element eliminates the need for uniform tensioning while maintaining the thin-panel capability.
Solution Approach 2:
The design uses simple, easily manufactured resonator shapes that can be produced using conventional techniques. These rigid structures are more durable and easier to fabricate than tensioned membranes, sacrificing the extreme thinness that membranes would provide but gaining significant improvements in manufacturability and reliability.
4Adaptability or versatility
If damping is increased to improve bandwidth of single resonator, then absorption bandwidth improves, but the design becomes impractical or requires impractically thick panels
Solution Approach 1:
Instead of over-damping a single resonator to broaden its absorption band, the invention segments the absorption function across multiple lightly-damped resonators, each optimized for a specific frequency range. This segmentation allows each resonator to maintain high Q-factor and efficiency while the collective system achieves broadband absorption.
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 panel achieves high acoustic absorption across a broader frequency range with a specific thickness, effectively addressing the limitations of existing designs by creating multiple resonances within a given frequency range, resulting in an average absorption coefficient of 90% between 224-447 Hz.
Implementation Method 1
each of the plurality of resonant cavities is tuned for a different frequency range
Implementation Method 2
high efficiency acoustic energy absorption over a broad frequency range
Implementation Method 3
Each set of openings is configured to provide fluid communication between one of the plurality of resonant cavities and the environment
Data Source
AI summary
A sound absorbing panel includes a cavity section having a plurality of resonant cavities and a front panel having a plurality of sets of openings. Each set of openings is configured to provide fluid communication between one of the plurality of resonant cavities and the environment. Each of the plurality of resonant cavities has different dimensions from the remaining plurality of resonant cavities such that each of the resonant cavities is tuned for a different frequency range. Each of the sets of openings can differ from the remaining sets of openings in opening size, length, and distance between openings.