An analytical-numerical method for determining the mechanical response of a condenser microphone

Area of Science:

• Acoustics and Mechanical Engineering
• Computational Fluid Dynamics
• Micro-Electro-Mechanical Systems (MEMS)

Background:

• Condenser microphones rely on diaphragm pressure and displacement for accurate sound measurement.
• Understanding the fluid dynamics beneath the diaphragm is crucial for microphone performance analysis.
• Existing methods may lack generality for diverse microphone geometries.

Purpose of the Study:

• To develop and validate a general numerical method for determining reaction pressure on microphone diaphragms.
• To analyze the mechanical sensitivity and noise characteristics of a reference microphone.
• To propose and evaluate a novel micromachined microphone design.

Main Methods:

• Numerical integration of the frequency-domain Stokes system to model air domain pressure and velocity.
• Analytical or numerical calculation of membrane displacement based on pressure distribution.
• Application of the method to a Bruel & Kjaer (B&K) 4134 1/2-inch microphone and a novel micromachined microphone design.

Main Results:

• The method accurately predicts mechanical sensitivity and mechano-thermal noise for the B&K 4134 microphone, aligning with published data.
• Membrane displacement fields were determined for specific frequencies, showing good correlation with measurements.
• The proposed micromachined microphone design exhibits mechanical performance comparable to existing B&K MEMS microphones.

Conclusions:

• The developed numerical method offers a versatile tool for analyzing condenser microphone diaphragm dynamics.
• The study validates the performance of a novel, fully micromachined microphone design.
• This approach facilitates the optimization and development of next-generation MEMS acoustic sensors.