Earmuff Acoustic Structure Using High-Aspect Air Gaps
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Solution Overview
Problem
Existing earmuff hearing-protection devices often fail to effectively attenuate sound due to the use of porous materials that do not provide sufficient sound insulation, leading to unwanted noise transmission.
Innovation Solution
Incorporation of a non-porous, sound-attenuating body within the earmuff shell, featuring inwardly-extending columns and ribs that create high aspect ratio air gaps to absorb sound through frictional and visco-thermal effects, reducing sound transmission through the shell and enhancing sound attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If porous materials are used as sound absorbers in earmuffs, then the device can be manufactured with simple structure, but the sound attenuation performance is insufficient
Solution Approach 1:
The patent changes the physical parameters of the sound-attenuating material from porous to non-porous, and from soft to rigid, while modifying the geometric parameters by introducing high aspect ratio air gaps (depth to width ratio of at least 8:1) between columns. This transformation achieves superior sound attenuation performance (reducing sound transmission by 2 dB or more in the 1000-8000 Hz range) while maintaining ease of manufacture through injection molding processes.
Solution Approach 2:
The patent creates a composite structure combining rigid non-porous material columns with high aspect ratio air gaps. This composite design integrates the sound absorption capabilities of porous materials with the structural stability and manufacturability of rigid materials, achieving both improved sound attenuation performance and ease of manufacture through modern molding techniques.
2Device complexity
If conventional porous sound absorbers are used, then the earmuff structure remains simple, but sound attenuation effectiveness is reduced
Solution Approach 1:
The patent segments the sound-attenuating body into multiple rigid columns arranged in an array, where each column is separated by high aspect ratio air gaps. This segmentation creates numerous interfaces that reflect and absorb sound waves, significantly improving sound attenuation effectiveness while the modular column structure maintains relatively simple device overall complexity and facilitates manufacturing.
3Object-affected harmful factors
If non-porous materials with high aspect ratio air gaps are used, then sound attenuation performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes the geometric parameters of the columns and air gaps to achieve effective sound attenuation. By controlling the aspect ratio (depth to width of at least 8:1) and the spacing between columns, the design achieves superior sound blocking performance while the parameters are configured to be compatible with standard injection molding processes, thus managing manufacturing complexity.
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 non-porous sound-attenuating body significantly increases sound attenuation by 2 dB or more in the 1000-8000 Hz range, minimizing noise transmission without the need for conventional porous materials, thereby improving hearing protection.
Implementation Method 1
absorb sound through frictional and visco-thermal effects
Implementation Method 2
absorb sound through frictional and visco-thermal effects
Data Source
Figure 1
Figure 2
Figure 3a
AI summary
An earmuff hearing-protection device (1) including a non-porous, sound-attenuating body (50) disposed within an interior space (31) defined by a shell (30) of an earmuff of the device, the non-porous, sound-attenuating body including sound-attenuating members (100) arranged and spaced to define a set of high aspect ratio air gaps (e.g. 300) between major side surfaces of neighboring members.