Multi-Passage Resonator Layout for Higher-Mode Suppression
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Solution Overview
Problem
Existing acoustic resonators face challenges in maintaining low acoustic damping at the main resonant frequency while avoiding interference from higher frequency modes, often resulting in undesired behavior due to increased air flow rates and flow noise.
Innovation Solution
A resonator design featuring multiple air passages communicating with an air cavity, where the passages are arranged to gradually decrease in length and cross-sectional area, distributed across multiple surfaces, and calculated using specific formulas to achieve desired acoustic mass and damping, effectively distributing higher modes over a wider frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If sound attenuation material is applied in the air passage to attenuate higher frequency resonances, then higher mode resonances are attenuated, but low acoustic damping at the main resonant frequency cannot be guaranteed
Solution Approach 1:
The single air passage is segmented into multiple parallel air passages, each with different effective lengths. This segmentation allows the system to handle different frequency ranges separately, with longer passages attenuating lower frequency modes and shorter passages allowing higher frequency passage while maintaining overall acoustic damping performance at the main resonant frequency.
Solution Approach 2:
Different air passages are designed with different local characteristics (different effective lengths) to perform different functions. The longer air passages provide attenuation for lower frequency modes, while shorter air passages maintain low acoustic damping for higher frequencies, creating local quality variations that resolve the contradiction.
2Object-affected harmful factors
If the air passage is made short to avoid higher modes, then higher modes in the air passage are avoided, but the air flow rate increases and low acoustic damping cannot be maintained
Solution Approach 1:
The air passage system is segmented into multiple parallel passages with different lengths. This allows the system to avoid higher modes in each individual passage while collectively maintaining the acoustic damping performance through the combination of different passage lengths, preventing the air flow rate increase that would occur with a single short passage.
Solution Approach 2:
The solution moves from a single-dimensional (single air passage) to a multi-dimensional approach by introducing multiple air passages with varying lengths. This dimensional expansion allows simultaneous achievement of higher mode avoidance and acoustic damping maintenance through the distributed passage configuration.
3Quantity of substance
If a single long air passage is used to maintain acoustic mass, then acoustic mass is maintained, but higher modes cause additional resonances at higher frequencies
Solution Approach 1:
The single long air passage is segmented into multiple parallel passages with different effective lengths. This segmentation distributes the acoustic mass across multiple pathways, maintaining the overall acoustic mass while preventing higher modes from causing additional resonances, as each passage length is optimized to avoid specific higher mode frequencies.
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 design ensures the main resonance frequency is maintained with reduced impact from higher modes, preventing nonlinear distortion and flow noise, thus guaranteeing the desired behavior of the resonator.
Implementation Method 1
An acoustic resonator refers to a structure that generates an acoustic resonant frequency, and it is usually a Helmholtz resonator. A Helmholtz resonator typically comprises a cavity and a tube connecting with the cavity.
Implementation Method 2
The air cavity and the plurality of air passages are tuned to generate one or more acoustic resonances.
Implementation Method 3
proper attenuation is desired for any resonances that are higher in frequency than the main (lowest) resonant frequency of the resonator
Data Source
AI summary
Provided is a resonator. The resonator includes: at least one air cavity and a plurality of air passages communicating with the air cavity. The air cavity and the plurality of air passages are tuned to generate one or more acoustic resonances. Therefore, the desired low acoustic damping can be reasonably well maintained, while distributing higher modes over a wider set of frequencies, while also making each of them proportionally weaker. Thus, they may be more easily made weak enough not to interfere with the desired behaviour of the overall acoustic resonator construction.