MEMS Microphone Thermal Sensor Ventilation Opening
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Solution Overview
Problem
Existing MEMS microphones face challenges in achieving reliable and noise-reduced sound wave detection, particularly at low frequencies, due to their complex construction and sensitivity to external factors like dust and moisture.
Innovation Solution
A MEMS microphone design that utilizes a thermal sensor configured to measure sound waves through a fluid flow created by a ventilation opening, which enables pressure compensation between the interior and exterior of the microphone, reducing noise and enhancing sensitivity across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive MEMS microphone design with perforated backplate is used, then sound wave detection capability is improved, but manufacturing complexity increases and additional noise is generated
Solution Approach 1:
The patent extracts the backplate structure from the traditional capacitive MEMS microphone design, replacing it with a thermal sensor positioned directly at the sound inlet. This eliminates the need for complex perforated backplates and diaphragm-backplate spacing adjustments, thereby reducing manufacturing complexity while maintaining sound detection capability through thermal flow measurement
Solution Approach 2:
The patent substitutes the mechanical capacitive measurement system (relying on diaphragm deflection and capacitance changes) with a thermal measurement system. The thermal sensor detects fluid flow caused by sound waves through heat transfer measurements, eliminating mechanical moving parts and reducing manufacturing complexity while improving reliability
2Measurement precision
If a capacitive MEMS microphone with perforated backplate is used, then sound wave detection is enabled, but noise from perforations degrades measurement resolution
Solution Approach 1:
The patent removes the perforated backplate structure entirely from the design. Instead of having sound waves pass through perforations that generate noise, the thermal sensor is positioned to directly measure fluid flow at the sound inlet, eliminating the noise-generating perforations while preserving sound detection capability
Solution Approach 2:
The patent replaces the mechanical acoustic measurement approach (which inherently generates noise from perforations and diaphragm vibrations) with a thermal measurement approach. The thermal sensor measures fluid flow through heat transfer, providing a noise-free measurement method that does not rely on mechanical acoustic pathways
3Adaptability or versatility
If capacitive MEMS microphone design is optimized for audio range, then frequency response 20Hz-20kHz is achieved, but low frequency detection below 100Hz becomes ineffective
Solution Approach 1:
The patent changes the fundamental measurement parameter from capacitive displacement (which has poor low-frequency response) to thermal flow measurement. Thermal sensors can detect fluid flow at very low frequencies including infrasound ranges because they measure the cumulative effect of flow over time rather than instantaneous pressure changes, thereby extending the effective frequency range to include frequencies below 100 Hz
4Measurement precision
If thermal sensor with ventilation opening is used, then low frequency sound wave detection is improved, but fluid flow measurement requires precise ventilation design
Solution Approach 1:
The ventilation opening serves multiple functions simultaneously: it provides the fluid flow pathway for sound detection, acts as a reference chamber for the thermal sensor, and defines the acoustic compliance of the system. This multi-functionality reduces the need for separate precision components, allowing the same structure to tolerate broader manufacturing variations while maintaining low-frequency detection capability
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 proposed design allows for high-resolution, precise measurement signals over a wide frequency range, including low frequencies, while minimizing noise and external interference, thereby ensuring reliable sound wave detection.
Implementation Method 1
The sensor is a thermal sensor configured to measure sound waves, which lead to a pressure difference between the interior and exterior regions of the MEMS microphone, based on a fluid flow through the ventilation opening
Implementation Method 2
The housing has a ventilation opening that enables fluid communication between the interior region and an exterior region of the MEMS microphone
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3
AI summary
The invention relates to a MEMS microphone for detecting sound waves. The MEMS microphone comprises a sensor and a housing. The housing encloses an inner region of the MEMS microphone and has a ventilation opening that allows fluid communication between the inner region and an outer region of the MEMS microphone. The sensor is a thermal sensor configured to measure sound waves, which result in a pressure difference between the inner region and the outer region of the MEMS microphone, by means of a fluid flow through the ventilation opening. Furthermore, the invention relates to a photoacoustic gas sensor, the sensor chamber of which, analogous to the MEMS microphone, also comprises a sensor and a housing, wherein the housing encloses an inner region of the sensor chamber and the sensor chamber has a ventilation opening that allows fluid communication between the inner region and an outer region of the sensor chamber.The sensor in the sensor chamber, analogous to the sensor in the MEMS microphone, is a thermal sensor configured to measure sound waves based on a fluid flow through the ventilation opening.