Interference Silencing Structure for Compact Low-Frequency Noise Control
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Solution Overview
Problem
Existing silencers using interference for sound reduction face limitations in miniaturization due to the requirement of a specific length difference in branch passages, particularly for low-frequency sounds, leading to larger sizes.
Innovation Solution
A silencing structure that incorporates a main flow passage and a sub-flow passage with a sound absorbing material at their connection points, adjusting the phase difference between sounds passing through both paths to achieve interference-based sound cancellation, allowing for miniaturization while maintaining effective sound reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional interference-type silencer with branch passages of different lengths is used, then sound cancellation is achieved, but the silencer size cannot be miniaturized
Solution Approach 1:
The patent introduces a sub-flow passage that branches off from and returns to the main flow passage, creating a three-dimensional path structure. This allows the sound path length to be extended in the longitudinal direction while maintaining a compact cross-sectional area, effectively decoupling the silencer volume from the required path length difference for interference.
Solution Approach 2:
The sub-flow passage is nested within the space between the main flow passage walls, utilizing the available volume efficiently. The sound absorbing material is disposed at the connection positions, creating a compact integrated structure that achieves the required phase difference without increasing the overall silencer dimensions.
2Reliability
If the path length difference is increased to achieve better interference, then sound cancellation improves, but the silencer becomes larger
Solution Approach 1:
Instead of extending the path length difference only in the longitudinal direction, the patent creates a sub-flow passage that loops back, utilizing the transverse space to add path length. This allows the required λ/2 path difference to be achieved through a combination of longitudinal and transverse path segments, reducing the overall silencer length.
Solution Approach 2:
The sub-flow passage has an asymmetric path configuration where the sound path length from the inlet to outlet through the sub-flow passage is deliberately made longer than the direct main flow passage path. This asymmetric design creates the necessary phase difference for interference while maintaining a compact overall structure.
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 structure effectively cancels sound using interference, enabling a smaller size and reduced weight compared to traditional silencers, with improved performance across a range of frequencies, especially low frequencies.
Implementation Method 1
A silencer deadens sound using interference
Implementation Method 2
a sound absorbing material that is disposed at least at a connection position between the main flow passage and the sub-flow passage
Data Source
AI summary
Provided is a silencing structure that uses interference and can be miniaturized while ensuring silencing performance. A silencing structure includes: a main flow passage that is connected to an inlet and an outlet; a sub-flow passage that branches off from the main flow passage and returns to the main flow passage; and a sound absorbing material that is disposed at least at a connection position between the main flow passage and the sub-flow passage. The sub-flow passage is not directly connected to the inlet and the outlet, and a length of a path that is from the inlet to the outlet and includes only the main flow passage is equal to or less than a length of a path that is from the inlet to the outlet and includes the sub-flow passage. For a sound with a frequency to be cancelled, a phase difference between a sound that passes through the path including only the main flow passage and a sound that passes through the path including the sub-flow passage is greater than 90 degrees and less than 270 degrees such that interference occurs to deaden the sound.