Surface-Mounted Acoustic Filter for MEMS Microphone
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Solution Overview
Problem
Hearing devices with MEMS microphones face issues such as non-linear frequency response, high sensitivity to ultrasonic noise, and mechanical complexity due to the use of electrical low pass filters, which lead to sensitivity losses and increased power consumption.
Innovation Solution
A surface-mounted acoustical low pass or band pass filter integrated with a microphone system on a printed circuit board, allowing for precise placement and reduced need for electrical filters, coupled with an acoustic tube and seal for improved acoustical matching and leakage prevention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two netlike acoustic input filters are used to protect microphones, then microphone protection is improved, but mechanical complexity increases and sensitivity losses occur
Solution Approach 1:
The patent combines the acoustic filter and acoustic tube into a single integrated component that is mounted on the printed circuit board. This merged structure provides both protection and acoustic transmission functions while reducing mechanical complexity compared to separate filter components.
Solution Approach 2:
The acoustic tube serves as an intermediary element that connects the acoustic filter to the microphone while maintaining acoustic transmission. This mediator allows the filter to be positioned away from the microphone, reducing direct mechanical complexity at the microphone assembly.
2Manufacturing precision
If an electrical low pass filter is used at the microphone output, then non-linearity reduction is improved, but sensitivity losses and power consumption increase
Solution Approach 1:
The patent replaces the electrical low pass filter with an acoustic low pass filter implemented through a physically structured acoustic tube. This substitution eliminates the need for electrical filtering circuitry, thereby reducing power consumption while maintaining non-linearity reduction through the acoustic tube's physical dimensions and structure.
3Ease of manufacture
If MEMS microphones are used, then automated mounting is improved, but sensitivity to ultrasonic noise increases
Solution Approach 1:
The acoustic tube acts as an intermediary between the external environment and the MEMS microphone, providing acoustic filtering that reduces ultrasonic noise sensitivity while allowing the microphone to maintain its automated mounting advantage.
4Manufacturing precision
If the filter sound outlet faces the printed circuit board through-hole, then mounting precision is improved, but acoustic alignment requirements increase
Solution Approach 1:
The acoustic tube is designed with an asymmetric structure where one end has a larger diameter for mounting on the printed circuit board and the other end has a smaller diameter for coupling to the microphone. This asymmetric design provides inherent alignment guidance that simplifies both mounting and acoustic alignment.
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 solution reduces non-linearity, increases efficiency, and decreases sensitivity losses while providing a compact and cost-effective design with enhanced acoustic performance and reduced power consumption.
Implementation Method 1
an acoustic tube for coupling the sound inlet to the sound outlet
Implementation Method 2
The seal can be provided with a hole formed through the seal in a longitudinal direction thereof. The filter can be equipped with the seal by simply fitting the seal via its hole on the acoustic tube.
Data Source
AI summary
A filter for a microphone system of a miniature electronic device. The filter includes a sound inlet and a sound outlet, wherein the filter is adapted to be mounted on a surface of a printed circuit board.