Microphone Accelerometer Vibration Compensation
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Solution Overview
Problem
Capacitive microphones face the challenge of 'body noise' suppression due to mechanical vibrations, which cause unwanted electrical signals, and existing solutions cannot effectively compensate for nonlinear transfer functions.
Innovation Solution
Incorporating an accelerometer on the same die as the microphone allows for electronic signal subtraction to cancel mechanical vibrations, providing additional functionality such as device control through shaking or orientation changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an accelerometer is added to the microphone device, then body noise suppression capability is improved, but device complexity increases
Solution Approach 1:
The accelerometer and microphone are integrated into a single device package, sharing common structural elements and manufacturing processes. The accelerometer is formed in the same die as the microphone, combining two functional components into one unified device that simultaneously provides audio capture and vibration sensing capabilities.
Solution Approach 2:
The integrated device serves multiple functions: the microphone captures acoustic signals while the accelerometer detects mechanical vibrations and body noise. This multi-functional design allows the single device to perform both audio recording and vibration-based control operations without requiring separate components.
2Measurement precision
If signal processing is used to compensate for body noise, then measurement precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
The accelerometer provides real-time feedback about mechanical vibrations and body noise to the signal processing system. This feedback loop enables dynamic compensation where the processed accelerometer signal is used to cancel out vibration-induced noise from the microphone output, continuously adapting to changing vibration conditions.
Solution Approach 2:
The accelerometer acts as an intermediary sensor that indirectly measures the mechanical vibrations affecting the microphone. Rather than directly measuring the acoustic signal with high precision, the system uses the accelerometer's vibration data as a mediator to compute and subtract the body noise component from the microphone output.
3Ease of manufacture
If the accelerometer is placed on the same die, then manufacturing cost is reduced, but area constraints become more severe
Solution Approach 1:
The accelerometer structure is nested within the same die footprint as the microphone, utilizing available space efficiently. The capacitive structures of both components are arranged to share common fabrication layers and processing steps, allowing compact integration without requiring proportional increases in die area.
Solution Approach 2:
The integration leverages the third dimension (vertical stacking) by forming both the microphone and accelerometer capacitive structures in multiple layers within the same die. This multi-layer approach allows both components to coexist in a compact footprint by utilizing vertical space rather than only horizontal expansion.
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 accelerometer effectively suppresses body noise and enables new device functionalities without increasing manufacturing costs or silicon area, ensuring a linear response to mechanical vibrations within the audible frequency range.
Implementation Method 1
forming a MEMs capacitive accelerometer comprising a suspended mass
Implementation Method 2
An electrically detectable signal, proportional to the sound pressure, is available due to modulation of the air gap by the sound pressure difference
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A microphone and a method for manufacturing the same is presented. The microphones comprises a substrate die (24); and a microphone (20) and an accelerometer (22) formed from the substrate die. The accelerometer is adapted to provide a signal for compensating mechanical vibrations of the substrate die.