MEMS Microphone Cantilever Structure for Low-Pressure Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional directional microphones with fixed-fixed transducer structures have high acoustic impedance and resonant frequencies above 20 kHz, limiting their ability to sense low differences in pressure and resulting in reduced sensitivity and signal-to-noise ratio.
Innovation Solution
The use of a cantilever structure with multiple sound ports positioned to minimize acoustic impedance and align with the transducer, ensuring the combined acoustic impedance of the channels is less than that of the transducer, thereby maintaining low resonant frequencies and improving sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed-fixed transducer structure is used, then the transducer has high acoustic impedance and high resonant frequency, but the sensitivity to low pressure differences is reduced
Solution Approach 1:
The patent changes the structural parameters of the transducer from fixed-fixed to fixed-free (cantilever) configuration, which fundamentally alters the acoustic impedance and resonant frequency characteristics. This parameter change enables the transducer to achieve low acoustic impedance and low resonant frequency while maintaining structural stability, thereby improving sensitivity to low pressure differences.
2Reliability
If the transducer has high acoustic impedance, then the resonant frequency is high (above 20 kHz), but the ability to sense low pressure differences is limited
Solution Approach 1:
The patent modifies the transducer structure from fixed-fixed to fixed-free configuration, changing the boundary conditions and resulting acoustic impedance parameters. This enables the transducer to operate at low resonant frequency with low acoustic impedance, improving pressure differential detection capability while maintaining structural integrity.
3Adaptability or versatility
If traditional directional microphone structure is used, then the microphone can separate sound sources directionally, but the sensitivity is reduced due to high resonant frequency
Solution Approach 1:
The patent applies parameter changes to the transducer structure, transitioning from fixed-fixed to fixed-free configuration. This changes the resonant frequency and acoustic impedance parameters, enabling the directional microphone to achieve high sensitivity to sound pressure while maintaining sound source separation capability through its directional structure.
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 cantilever structure with aligned sound ports enhances sensitivity and signal-to-noise ratio by allowing the transducer to sense low pressure differences, while minimizing the impact of package impedance on the transducer's sensitivity.
Implementation Method 1
As sound hits the microphone, the sound couples into one of the air volumes through the sound port and changes the pressure. This creates a difference in pressure between the front volume and back volume that creates a force on the transducer and drives its motion.
Implementation Method 2
The MEMS transducer comprises a cantilever structure... the at least two sound ports are positioned on the package in a manner that ensures that the respective acoustic channels have a combined second acoustic impendence that is less the first acoustic impedance of the MEMS transducer
Data Source
AI summary
An acoustic sensor device comprises a package and a substrate disposed in the package. The acoustic sensor device also comprises a microelectromechanical system (MEMS) transducer formed in the substrate, the MEMS transducer i) comprising a cantilever structure and ii) having a first acoustic impedance and at least two sound ports positioned on the package on opposing sides of the MEMS transducer. The at least two sound ports coupling the MEMS transducer to an ambient environment via respective acoustic channels formed in the package, wherein the at least two sound ports are positioned on the package in a manner that ensures that the respective acoustic channels have a combined second acoustic impendence that is less the first acoustic impedance of the MEMS transducer.