Foamed Earplug Recesses for Sound Absorption
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Solution Overview
Problem
Conventional earplugs fail to allow sound permeability while maintaining sound reduction, leading to interference from otoacoustic emissions, bone conduction, and the occlusion effect, which affects communication and ambient noise perception.
Innovation Solution
The earplug features surface-enlarging inner and outer central longitudinal recesses separated by a transverse wall, increasing the surface area for sound absorption and reducing reflection, while maintaining stability and fit, and includes casing recesses and a collar-like widening for ease of use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional earplugs close the ear canal completely to achieve maximum sound insulation, then sound reduction is improved, but interference from otoacoustic emissions, bone conduction, and occlusion effect increases
Solution Approach 1:
The inner end face is segmented into multiple recesses (first recess, second recess, third recess) that divide the surface into different functional zones. This segmentation allows selective sound absorption in specific frequency ranges while maintaining overall sound insulation, reducing the occlusion effect and interference noise.
Solution Approach 2:
Different regions of the inner end face are given different acoustic properties through the recess configuration. The first recess targets high-frequency sounds, the second recess targets mid-frequency sounds, and the third recess targets low-frequency sounds, creating local quality variations that reduce specific interference noises while maintaining overall sound reduction.
2Loss of energy
If the ear canal is completely blocked for maximum sound insulation, then sound reduction is improved, but communication and ambient noise perception deteriorates
Solution Approach 1:
The segmented recess structure on the inner end face creates frequency-selective sound absorption. By targeting specific frequency ranges (high, mid, low frequencies) with different recesses, the design reduces unwanted noise while preserving important communication frequencies, maintaining ambient noise perception capability.
3Loss of energy
If surface area at inner end face is increased for sound absorption, then sound permeability is improved, but structural stability may deteriorate
Solution Approach 1:
Instead of creating one large cavity that would compromise structural integrity, the design segments the inner end face into multiple smaller recesses. This segmentation increases the effective surface area for sound absorption while distributing the material removal across multiple small features, maintaining overall structural stability of the earplug base body.
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 allows for defined sound permeability, reducing unwanted noise and occlusion effects, while maintaining effective sound insulation and ease of use, with improved manufacturing and fit.
Implementation Method 1
the inner recesses in particular form cavities, which increases the surface area at the inner end of the earplug. As a result of this surface enlargement, in contrast to a spherical cap-shaped surface in conventional earplugs, the reflection of the sound waves is reduced and in particular a directed reflection is avoided.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The surface of an ear plug made of foamed material has recesses (5, 6) on the surface of the ear plug in the area of the face of the inner end (2) in order to achieve a defined damping and to avoid interference from inherent noises. The ear plug comprises a base body (1) which has a central longitudinal axis (12) and in the direction of said central longitudinal axis (12) has an inner end face relative to the axis (2) and an outer end face relative to the axis (3). In the area of the inner end face (2), inner surface-increasing recesses (5, 6) are provided, one of which extends as an inner central recess (6) beginning from the inner end face (2) along the length of the central longitudinal axis towards the inside. In addition an outer central longitudinal recess (8) is provided which, beginning from the outer end face (3), extends along the central longitudinal axis (12) towards the inside. The inner and the outer central longitudinal recess (6, 8) are separated from each other by a continuous transverse wall (7) running perpendicularly to the central longitudinal axis (12).