MEMS Microphone Equalization for Resonance Removal

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Solution Overview

Problem

Existing MEMS microphones face challenges with resonance in the audio band, leading to potential damage to listeners and inaccurate sound reproduction, as well as issues with power consumption and reliability in harsh environments.

Innovation Solution

The proposed solution involves an electronic acoustic device comprising a primary MEMS microphone and a reference MEMS microphone, both configured to receive a common acoustic signal. The device includes an equalization module that uses the transduced signals from both microphones to equalize the frequency response of the primary microphone, effectively removing the resonance peak.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional capacitive MEMS microphones are used, then high sensitivity is achieved, but power consumption increases and reliability decreases in harsh environments

Engineering Contradiction:

ImprovesensitivityVSAvoidreliability in harsh environments

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the operating parameters by using piezoelectric materials instead of capacitive structures, eliminating the need for bias voltage and improving reliability in harsh environments while maintaining sensitivity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the capacitive electrical system with a piezoelectric mechanical system that converts mechanical stress directly to electrical signals, eliminating power consumption issues and improving environmental reliability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If resonance frequency is present in the audio band, then microphone structure is simple, but harmful effects occur including potential damage to listeners and inaccurate sound reproduction

Engineering Contradiction:

Improvemicrophone structureVSAvoidharmful effects of resonance

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the resonance peak from the audio band by using a notch filter that removes the specific resonant frequency component, eliminating harmful effects while maintaining the simple microphone structure

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses feedback through a secondary microphone and signal processing to detect and cancel resonance peaks in real-time, preventing harmful effects without complicating the physical microphone structure

Inventive Principle:

Principle #23Feedback

3Measurement precision

If factory calibration with fixed frequency notch is applied, then resonance frequency is compensated, but the solution fails in the presence of unpredictable real-world noise

Engineering Contradiction:

Improvefrequency response accuracyVSAvoidperformance in unpredictable real-world noise

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent transitions from a static factory-calibrated notch filter to a dynamic adaptive system that continuously monitors and adjusts to real-world noise conditions, maintaining frequency response accuracy in unpredictable environments

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent enables the microphone system to self-adjust and self-calibrate in real-time by using its own output and environmental feedback, eliminating the need for fixed factory calibration and adapting to changing noise conditions

Inventive Principle:

Principle #25Self-service

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

This approach allows for the removal of resonance peaks from the audio band, improving the sensitivity and signal-to-noise ratio of MEMS microphones without tradeoffs in frequency response, and is suitable for operation in noisy environments.

Implementation Method 1

Piezoelectric MEMS microphones have been used to address the deficiencies of capacitive MEMS microphones

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a microphone having a frequency response including a resonance frequency

Methodology Applied

Scientific EffectAcoustic radiation pressure: Acoustic Radiation Pressure

Implementation Method 3

Resonance occurs when a physical object or electronic circuit absorbs energy from an initial displacement or source, and then maintains the resultant mechanical or electrical vibrations without an additional force or energy acting on it

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS12297100B2Electronic acoustic devices, MEMS microphones, and equalization methods

Publication Date: 2025.05.13 SKYWORKS SOLUTIONS INC

AI summary

Electronic acoustic devices and methods of operating the same include a microphone having a frequency response including a resonance frequency, a reference microphone having a frequency response including a resonance frequency, the microphone and the reference microphone configured to substantially simultaneously receive a common acoustic signal to produce a transduced signal of the microphone and a transduced signal of the reference microphone, the resonance frequency of the reference microphone being different than the resonance frequency of the microphone, and an equalization module configured to equalize the frequency response of the microphone based on the transduced signal of the microphone and the transduced signal of the reference microphone.