Stepped Acoustic Structure for Multi-Degree Impedance Control
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Solution Overview
Problem
Existing acoustic structures with honeycomb cells face challenges in achieving multiple degrees of acoustic freedom due to difficulties in accurately placing septum caps at varying depths, leading to increased adhesive applications and potential alterations in physical properties, especially when the desired depth differences are small or large.
Innovation Solution
A stepped acoustic structure is introduced where septum caps are anchored at the same depth, with steps reducing the cell's cross-sectional area to match impedance changes that would otherwise be achieved by varying septum depths, and depth control portions allow for fine-tuning of septum positions, enabling multiple degrees of freedom with a single adhesive application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If septum caps are anchored at different depths to achieve multiple degrees of acoustic freedom, then acoustic impedance variability is improved, but the number of adhesive applications increases and manufacturing complexity worsens
Solution Approach 1:
The patent transitions from varying septum cap depths (one-dimensional variation) to varying cell cross-sectional areas (introducing a second dimension). By modifying the cell geometry rather than the septum position, the patent achieves multiple degrees of acoustic freedom while maintaining uniform septum anchoring depth, thereby simplifying the manufacturing process to a single adhesive application.
Solution Approach 2:
The patent changes the geometric parameters of the honeycomb cells by introducing steps that reduce cross-sectional area at specific locations. This parameter change in cell geometry provides the necessary acoustic impedance variability without requiring multiple adhesive applications at different depths, thus resolving the contradiction between acoustic performance and manufacturing complexity.
2Manufacturing precision
If multiple adhesive applications are used to bond septum caps at different depths, then acoustic impedance control is improved, but weight and physical property alterations worsen
Solution Approach 1:
The patent eliminates the need for multiple adhesive applications by shifting from depth-based variation to cross-sectional area-based variation. This dimensional shift allows all septum caps to be anchored at the same depth with a single adhesive application, thereby reducing the total adhesive material used and minimizing weight increase while maintaining precise acoustic impedance control through geometric modification.
3Ease of manufacture
If septum caps are anchored at the same depth with steps reducing cross-sectional area, then manufacturing simplicity is improved, but structural complexity worsens
Solution Approach 1:
The patent divides the honeycomb structure into segments with different cross-sectional areas by introducing steps at specific locations. This segmentation approach simplifies the manufacturing process (single adhesive application) while the added geometric complexity is localized to specific cell regions, balancing overall structural complexity acceptance with manufacturing simplicity gains.
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 approach eliminates the need for multiple adhesive applications, reduces weight and physical property alterations, and effectively varies acoustic impedance across cells, providing a multi-degree-of-freedom acoustic structure that accurately matches impedance profiles previously achieved by varying septum depths.
Implementation Method 1
acoustic resonators that contain relatively thin acoustic materials or grids that have millions of holes that create acoustic impedance to the sound energy generated by the engine
Implementation Method 2
The stepped acoustic structure includes a first resonator with a first acoustic impedance and a second resonator with a second acoustic impedance
Data Source
Figure 1~2
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Figure 5
AI summary
A stepped acoustic structure having multiple degrees of acoustic freedom for reducing noise generated from a source. Acoustic septum caps are anchored at the same depth within the cells of the stepped acoustic structure. The multiple degrees of acoustic freedom that is usually provided by locating the septum portions of the septum caps at different depths within the cells is obtained by placing steps within the cells which reduce the cross-sectional area of the cell. Depth control portions are optionally included in the septum caps so that the septum portions of different septum caps are located at different depths within the stepped acoustic structure. Various combinations of steps and depth control portions are used to provide an acoustic structure having multiple degrees of acoustic freedom even though the acoustic septum caps are anchored at the same depth within the structure.