Hearing Device Speaker Membrane Holes for Acoustic Bias Control
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Solution Overview
Problem
Hearing devices with active noise control face challenges in achieving predictable and invariant acoustic properties due to the risk of membrane bias and acoustic leakage, particularly with moving coil speakers, which affect low-frequency efficiency and resonance.
Innovation Solution
Incorporating small holes in the speaker membrane or its surrounding frame to equalize pressure and provide a controlled leakage path, allowing the back volume to be coupled to the ambiance, thereby eliminating membrane bias and ensuring a well-defined leakage path without additional resistive members or complex manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the back volume is closed, then the efficiency of the acoustic transducer is reduced at low frequencies, but the membrane bias risk is minimized
Solution Approach 1:
The partition between front and back volumes is made porous by incorporating holes, allowing controlled acoustic leakage. This enables the back volume to be acoustically connected to the front volume without requiring a fully open structure, thus preventing membrane bias while maintaining low-frequency efficiency.
Solution Approach 2:
The partition with holes acts as an intermediary element between the front and back volumes. It provides a controlled acoustic pathway that mediates the pressure equalization, allowing the system to achieve both membrane bias prevention and acceptable low-frequency performance.
2Use of energy by moving object
If the back volume is open to ambience via acoustic port, then low-frequency efficiency is improved, but acoustic resonance properties become unpredictable
Solution Approach 1:
The acoustic properties are controlled by changing the parameters of the partition (number, size, and distribution of holes) rather than relying on the acoustic load from an open back volume. This provides a well-defined leakage path that ensures predictable acoustic properties while maintaining low-frequency efficiency.
3Reliability
If resistive members are added between back volume and ambience, then acoustic resonance side effects are reduced, but device complexity increases
Solution Approach 1:
The functions of the partition and the resistive member are merged into a single element. The partition itself, with its specific hole configuration, performs both the structural separation and the acoustic resistance functions, eliminating the need for separate resistive members and simplifying the device.
Solution Approach 2:
The partition is designed to serve multiple functions: structural separation between volumes, controlled acoustic leakage pathway, and acoustic resistance element. This multi-functionality reduces the overall device complexity while achieving the desired acoustic property invariance.
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 ensures predictable acoustic properties, reduces resonance peaks, and maintains sound quality by mitigating unwanted side effects, while simplifying the design and reducing the risk of obstruction by earwax.
Implementation Method 1
the path through the hole(s), due to the back side being coupled to environment, allow for an equalization of the pressure between the front side and the back side
Implementation Method 2
the hole(s) ensure that the leakage path from the ear canal volume to the ambience is well-defined and predictable
Implementation Method 3
Active noise control is the principle of reducing or suppressing unwanted sound by addition of a sound signal cancelling the unwanted sound
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
According to the invention, a hearing device (earphone, 'hearable', earbud, earplug, hearing aid, etc.) with a moving coil speaker and with an active noise control circuit has at least one hole in the speaker membrane (41) and/or, if present, in another element of the partition between the speaker front side and the speaker back side to which the membrane (41) belongs. Such other element of the partition may for example be a membrane frame (43) surrounding the membrane and connecting it to a housing (40) of the hearing device. The speaker back side is coupled to ambience, for example via at least one rear port (52).