MEMS Microphone Tunable Back Cavity Acoustic Shock
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Solution Overview
Problem
Conventional MEMS microphones have limited acoustic characteristics and lack robustness in withstanding extreme acoustic shocks, such as those encountered in guided drop tests, due to their device characteristics and physical constraints.
Innovation Solution
A MEMS microphone design featuring a tunable back cavity system with a first and second back cavity separated by a tuning port, which can be configured as a baffle assembly to restrict airflow and absorb acoustic impacts, allowing for independent shaping of high-frequency response and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single acoustic back cavity is used in conventional MEMS microphones, then the device structure is simple, but the acoustic characteristics (sensitivity, frequency response) are limited and cannot be tuned effectively
Solution Approach 1:
The single acoustic back cavity is divided into two separate cavities: a first back cavity formed by the MEMS chip and substrate, and a second back cavity formed by the package substrate and cover. This segmentation allows independent tuning of each cavity's acoustic characteristics through separate volume control and independent port configurations, resolving the limitation of fixed acoustic properties in single-cavity designs.
2Reliability
If conventional MEMS microphone configurations are used, then the device meets basic acoustic requirements, but it lacks robustness in withstanding extreme acoustic shocks such as guided drop tests
Solution Approach 1:
The tuning port is configured as a baffle assembly that restricts airflow between the first and second back cavities. This baffle structure acts as a cushioning mechanism that absorbs and mitigates extreme acoustic shock pressures before they can damage the MEMS sensor element, enabling the microphone to withstand guided drop tests and other extreme acoustic events.
3Measurement precision
If the acoustic back cavity volume is increased to improve low-frequency response, then sensitivity at low frequencies improves, but high-frequency peaking increases and acoustic shock absorption capability decreases
Solution Approach 1:
By segmenting the back cavity into two separate volumes, the design achieves independent optimization: the first cavity volume can be tuned for low-frequency sensitivity while the second cavity provides high-frequency response control and shock absorption. The tuning port with baffle assembly further enables independent control of acoustic coupling between cavities, allowing simultaneous optimization of multiple frequency ranges without the trade-offs inherent in single-cavity designs.
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 tunable back cavity design enhances the microphone's ability to withstand acoustic shocks and improve acoustic characteristics by allowing for better absorption of acoustic energy and reduced high-frequency peaking, providing superior robustness and performance.
Implementation Method 1
a tuning port that can separate and/or acoustically couple the first and second back cavities. Additionally, the tuning port can be configured as a baffle assembly that can restrict airflow between the first back cavity and the second back cavity in response to an acoustic impulse
Implementation Method 2
The tunable back cavity design enhances the microphone's ability to withstand acoustic shocks and improve acoustic characteristics by allowing for better absorption of acoustic energy
Data Source
AI summary
Microelectromechanical systems (MEMS) microphones associated with a tunable back cavity are described. Provided implementations can comprise a MEMS acoustic sensor element associated with a first back cavity, which first back cavity can be separated and/or acoustically coupled by a tuning port to a second back cavity. In addition, various physical and acoustic filtering configurations of MEMS microphones and tunable back cavities are described.