Multi-Sectional Septum for Low-Frequency Noise Absorption
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Solution Overview
Problem
Existing acoustic structures, such as aircraft engine nacelles, face challenges in attenuating a wide range of noise frequencies, particularly low-frequency noise, without increasing thickness or weight, as newer jet engines produce more noise at lower frequencies, requiring deeper acoustic cells which contradicts the goal of maintaining thin and lightweight designs.
Innovation Solution
The use of multi-sectional septums within acoustic cells, which extend vertically and have different acoustic damping properties, effectively increases the acoustic length of the resonator and allows for targeted damping of specific frequency ranges, achieved by varying the material, length, location, and shape of the septum sections, enabling effective low-frequency noise absorption without increasing thickness or cell count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If deeper acoustic cells are used to absorb low-frequency noise, then noise attenuation performance is improved, but nacelle thickness and weight increase
Solution Approach 1:
The acoustic cell is segmented into multiple sections by dividing it into a first acoustic chamber and a second acoustic chamber separated by a partition wall. This segmentation allows each chamber to be optimized for different frequency ranges, enabling effective low-frequency noise absorption while maintaining a compact overall thickness.
Solution Approach 2:
The partition wall extends partially through the acoustic cell depth, creating a three-dimensional configuration that effectively increases the acoustic path length without proportionally increasing the physical thickness of the nacelle. This dimensional approach allows deeper acoustic interaction within a thinner profile.
2Object-affected harmful factors
If deeper acoustic cells are used to absorb low-frequency noise, then noise attenuation performance is improved, but nacelle weight increases
Solution Approach 1:
By segmenting the acoustic cell into multiple chambers with different depths and configurations, the design achieves effective low-frequency noise absorption without requiring a uniform increase in depth throughout the entire structure, thereby reducing the overall material required and nacelle weight.
3Object-affected harmful factors
If the number of acoustic cells is reduced to accommodate larger cell depth, then low-frequency absorption is improved, but the number of available acoustic cells decreases
Solution Approach 1:
The partition wall divides each acoustic cell into multiple functional chambers, effectively creating additional acoustic pathways and resonant cavities within each cell. This increases the total acoustic volume and number of effective acoustic elements without increasing the physical footprint or reducing the number of cells.
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 allows for efficient absorption of lower noise frequencies and targeted damping of specific frequency ranges, maintaining the thin and lightweight design of acoustic structures while effectively addressing the noise challenges posed by modern jet engines.
Implementation Method 1
The use of multi-sectional septums within acoustic cells, which extend vertically and have different acoustic damping properties, effectively increases the acoustic length of the resonator and allows for targeted damping of specific frequency ranges
Implementation Method 2
This approach allows for efficient absorption of lower noise frequencies and targeted damping of specific frequency ranges
Data Source
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AI summary
A multi-sectional acoustic septum 'that includes sections which have different acoustic resistance properties. The multi-sectional acoustic septums extend vertically with the acoustic cell and are capable of increasing the effective acoustical length of the acoustic cell. The multiple acoustic properties provided by the multiple acoustic sections also make it possible to target specific frequency ranges within the overall frequency range of the acoustic cell.