Bone Conduction Microphone With Metal Shielding for Higher SNR
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Solution Overview
Problem
Bone conduction microphones suffer from insufficient signal-to-noise ratio (SNR) due to electromagnetic interference affecting the MEMS and ASIC chips, which compromises sound quality in noisy environments.
Innovation Solution
A bone conduction microphone design incorporating a metal cover with electromagnetic shielding properties, a porous or meshed top wall, and a vibration assembly to reduce interference and improve SNR, while also protecting the chips from vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bone conduction microphone uses MEMS and ASIC chips for signal conversion, then it can convert bone vibrations into electrical signals, but electromagnetic interference affects the chips and reduces the signal-to-noise ratio
Solution Approach 1:
The patent introduces a metal cover as an intermediary shielding structure between the electromagnetic interference source and the MEMS/ASIC chips. This metal cover acts as a mediator that blocks harmful electromagnetic fields while allowing the bone conduction vibration transmission to proceed unchanged, thus protecting the chips without affecting the core function.
Solution Approach 2:
The metal cover creates an electromagnetic shielding environment around the chips, effectively isolating them from external electromagnetic interference. This shielding environment protects the sensitive electronic components from harmful electromagnetic fields while maintaining the operational integrity of the bone conduction microphone system.
2Reliability
If the vibration member is positioned close to the MEMS chip for direct vibration transmission, then vibration transmission efficiency is improved, but the chip is vulnerable to impact damage
Solution Approach 1:
The metal cover serves as a protective intermediary between the vibration member and the MEMS chip. It allows vibration transmission to reach the chip while simultaneously protecting the chip from direct impact damage, thus resolving the contradiction between transmission efficiency and impact resistance.
Solution Approach 2:
The metal cover provides beforehand protection to the MEMS chip against potential impact damage from the vibration member. By positioning the metal cover between the vibration member and chip, it cushions and absorbs impact forces before they can reach the sensitive chip, while still allowing vibration transmission to occur.
3Object-affected harmful factors
If a solid metal cover is used for electromagnetic shielding, then electromagnetic interference is blocked, but vibration transmission may be obstructed
Solution Approach 1:
The patent employs a porous metal structure for the metal cover, which combines the electromagnetic shielding properties of metal with the vibration transmission capabilities of porous materials. The porous structure allows vibration waves to pass through while still providing effective electromagnetic interference blocking, thus resolving the contradiction between shielding effectiveness and vibration transmission.
Solution Approach 2:
The metal cover is designed as a composite structure that integrates electromagnetic shielding materials with vibration-transmissive materials. This composite design enables the cover to simultaneously block electromagnetic interference and allow bone conduction vibrations to pass through to the MEMS chip, addressing both requirements without compromise.
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 design enhances SNR and reliability by shielding against electromagnetic interference and protecting the MEMS and ASIC chips, thereby improving sound quality and durability.
Implementation Method 1
the metal cover has the function of electromagnetic shielding, so as to reduce the electromagnetic interference affecting the MEMS chip and the ASIC chip
Implementation Method 2
Bone conduction microphones convert slight vibrations of bones of the head and neck caused by human voice into electrical signals
Implementation Method 3
a MEMS chip disposed in the first cavity and fixed to the circuit board. The vibration of the vibration member is transmitted to one side of the MEMS chip through the first conduction cavity, the acoustic channel and the back cavity
Data Source
AI summary
A bone conduction microphone is disclosed. The bone conduction microphone includes a circuit board, a housing engaged with the circuit board, a metal cover engaged with the circuit board for forming a first cavity, a vibration assembly, and a MEMS chip disposed in the first cavity. The metal cover includes a top wall and a side wall. The vibration assembly engages with the top wall for forming a second cavity and includes a vibration member and a spacer member. A first conduction cavity is formed by the housing, the vibration assembly, the metal cover and the circuit board. A vibration of the vibration member is transmitted to one side of the MEMS chip through the first conduction cavity, an acoustic channel of the circuit board and a back cavity of the MEMS chip. The bone conduction microphone reduces the electromagnetic interference and improves the SNR.