MEMS Microphone Drop Protection via Speaker Acoustic Pressure

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Solution Overview

Problem

Microelectrical-mechanical system (MEMS) microphones in portable devices are prone to damage when the device is dropped, as the impact causes sudden pressure increases that can damage the dynamic membrane, leading to displacements of up to 1 mm or more.

Innovation Solution

A device comprising a motion detector, a MEMS microphone, and a speaker, where the motion detector determines a drop and the speaker emits a sound according to predetermined parameters to apply acoustic pressure to the microphone membrane, reducing deflection and potential damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the portable device uses a MEMS microphone with a dynamic membrane, then the microphone can effectively capture sound, but the membrane is prone to damage when the device is dropped due to sudden pressure increases

Engineering Contradiction:

Improvemicrophone damage resistanceVSAvoidpressure damage to membrane

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system applies preliminary anti-action by detecting a drop event before impact occurs and activating the speaker to emit a sound that creates acoustic pressure on the membrane in advance. This pre-applied acoustic pressure counteracts the harmful pressure increase that will occur during impact, reducing the net pressure differential and preventing membrane damage.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The system performs preliminary action by using the motion detector to identify a drop event and triggering the speaker to emit the protective sound before the actual impact occurs. This timing ensures the membrane is already under acoustic pressure from the speaker when the external impact pressure arrives, creating a protective effect.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the speaker emits a sound to apply acoustic pressure to the membrane during a drop, then membrane deflection is reduced, but additional energy is consumed by the speaker

Engineering Contradiction:

Improvemembrane protectionVSAvoidspeaker energy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The system applies periodic action by emitting the protective sound only during specific drop events rather than continuously. The motion detector triggers the speaker intermittently based on detected drop conditions, consuming energy only when protection is needed rather than maintaining constant acoustic pressure.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system implements self-service by using the device's own speaker to generate the protective acoustic pressure rather than requiring an external protection mechanism. The speaker, which is already part of the device, is repurposed to serve the dual function of audio output and microphone protection, eliminating the need for additional dedicated protection components.

Inventive Principle:

Principle #25Self-service

3Reliability

If the motion detector triggers the speaker to emit sound during a drop, then the membrane is protected from impact damage, but the system complexity increases due to coordination between components

Engineering Contradiction:

Improvemicrophone impact resistanceVSAvoidcoordination between motion detector and speaker

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system applies universality by making the speaker multi-functional: it serves both as the audio output device for normal operation and as the protective mechanism for microphone damage prevention during drops. This eliminates the need for a separate dedicated protection device, reducing overall system complexity despite the coordination requirements.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system merges the protection function with the existing audio playback function by using the same speaker for both purposes. The motion detector coordinates with the existing speaker hardware rather than requiring a separate protection mechanism, combining multiple functions into a single component to simplify the overall system architecture.

Inventive Principle:

Principle #5Merging (Combining)

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 acoustic pressure emitted by the speaker reduces membrane deflection during a drop, minimizing damage to the MEMS microphone, as demonstrated by displacement curves showing a reduction of about 0.2 mm in membrane displacement with sound application compared to without.

Implementation Method 1

the speaker may be responsively controlled to emit a sound to apply an acoustic pressure to a membrane of the MEMS microphone

Methodology Applied

Scientific EffectAcoustic pressure: Acoustic Radiation Pressure

Data Source

PatentUS10820099B1Device and method to control a speaker to emit a sound to protect a microphone

Publication Date: 2020.10.27 MOTOROLA SOLUTIONS INC

AI summary

A device and method controlling a speaker to emit a sound to protect a microphone is provided. An example device: determines, using a motion detector, when a drop is occurring. The example device, in response to determining that a drop is occurring: controls a speaker of the example device to emit a sound according to one or more predetermined drop parameters, the sound to apply an acoustic pressure at a membrane of the MEMS microphone of the example device to reduce a deflection thereof that results due to one or more of the drop and an impact which ends the drop.