MEMS Microphone Interposer With Damping Membrane for High-SPL Measurement
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Solution Overview
Problem
Existing MEMS microphones are unsuitable for aeroacoustic measurements due to their inability to measure high sound pressure levels without distortion, and they are either too large, expensive, or both, which affects airflow and are not suitable for precise, cost-effective installation on vehicle surfaces.
Innovation Solution
A MEMS microphone system with an elastic and vibratable damping membrane mounted in front of the sound inlet opening, which distributes sound energy between the damping membrane and the microphone membrane, allowing for distortion-free measurement of high sound pressure levels up to 200 dB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If MEMS microphones are used for aeroacoustic measurements, then compactness and low cost are achieved, but they cannot measure high sound pressure levels without distortion
Solution Approach 1:
A damping membrane is introduced as an intermediary element between the sound field and the microphone diaphragm. This damping membrane absorbs and attenuates high sound pressure levels before they reach the microphone diaphragm, enabling accurate measurements at SPLs up to 200 dB while protecting the sensitive microphone element from distortion and damage.
Solution Approach 2:
The damping membrane is designed with specific material properties and geometric parameters (thickness, density, surface area) that can be optimized to achieve the desired sound pressure level attenuation. By adjusting these parameters, the system can be tuned to handle different ranges of high SPL while maintaining measurement accuracy.
2Measurement precision
If larger microphones are used to measure high sound pressure levels, then measurement capability is improved, but they interfere with airflow and are not suitable for vehicle surface installation
Solution Approach 1:
The measurement system is segmented into two functional components: the damping membrane that handles high SPL attenuation and the compact MEMS microphone that performs precise measurement. This segmentation allows the microphone to remain small and non-intrusive to airflow while the damping membrane provides the necessary high SPL measurement capability.
Solution Approach 2:
The damping membrane is implemented as a thin, flexible film that can be integrated into the microphone housing or vehicle surface without creating significant protrusions or disruptions to the surrounding airflow, enabling high SPL measurements while maintaining aerodynamic cleanliness.
3Measurement precision
If additional damping components are added to extend measurement range, then measurement capability is improved, but device complexity increases
Solution Approach 1:
The damping membrane is merged with the microphone housing or mounting structure, combining the damping function with the existing structural components. This integration approach extends the measurement range to 200 dB without requiring separate, complex damping assemblies, thereby minimizing additional complexity while achieving the extended measurement 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 system enables high-resolution, distortion-free measurement of sound pressure levels up to 200 dB, maintaining signal-to-noise ratio and avoiding airflow interference, while being compact and cost-effective for aeroacoustic applications.
Implementation Method 1
the damping membrane is excited to vibrate by the sound waves, so that the sound energy of the sound waves is distributed between the damping membrane and the microphone membrane
Implementation Method 2
the damping element comprises an elastic and vibratable damping membrane
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
In a first aspect, the invention relates to a system (1) comprising a MEMS microphone (3) having a sound inlet opening (5), an oscillatory microphone membrane (7) and an electronic circuit (9), wherein, when the microphone membrane (7) is excited by sound waves entering through the sound inlet opening (5), an electrical signal that is dependent on the sound waves is generated by oscillations of the microphone membrane (7). A damping element (11) for reducing a sound pressure level of the sound waves acting on the microphone membrane (7) is mounted upstream of the sound inlet opening (5), wherein the damping element (11) comprises a resilient and oscillatory damping membrane (11) and wherein the damping element (11), in addition to the microphone membrane (7), is excited into oscillation by the sound waves such that sound energy of the sound waves is divided between the damping membrane (11) and the microphone membrane (7). This makes it possible in particular to extend the measuring range of the MEMS microphone (3) to high sound pressure levels without distortion.