Ferroelectret Polymer Foam Microphone for Hearing Instruments

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Solution Overview

Problem

Conventional hearing instruments' microphones are susceptible to debris contamination, leading to operational failures, as they require acoustic loading with small air volumes and orifices that can be occluded by debris.

Innovation Solution

Integration of ferroelectret polymer foam as a transduction element within hearing assistance devices, which provides robustness against debris contamination and does not require a bias voltage or power supply, allowing for easy integration on complex surfaces and functioning as both a microphone and momentary switch sensor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional microphones (electret condenser or MEMS) are used in hearing instruments, then they can provide adequate sound sensing capability, but they are susceptible to debris contamination through orifices and on transduction mechanisms, leading to operational failure

Engineering Contradiction:

Improvemicrophone reliabilityVSAvoiddebris contamination

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent removes the vulnerable orifice structure from the microphone design by using a ferroelectret polymer foam that responds directly to sound pressure waves without requiring an acoustic loading volume or opening. This extraction of the orifice eliminates the primary entry point for debris contamination while maintaining microphone functionality through the foam's piezoelectric response to pressure changes.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The ferroelectret polymer foam acts as a flexible, porous material that can be integrated directly into the hearing instrument housing. Its foam structure allows sound pressure transmission while its ferroelectret properties enable direct conversion of mechanical pressure into electrical signals, providing both protection and transduction in a single component.

Inventive Principle:

Principle #30Flexible shells and thin films

2Reliability

If barriers (meshes, screens, membranes, coatings) are added to protect microphones from debris, then they may postpone failure, but they add device complexity and do not prevent failure when debris attaches to transduction mechanism or occludes orifices

Engineering Contradiction:

Improvemicrophone protectionVSAvoidbarrier structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the protective barrier function with the transduction function into a single ferroelectret polymer foam component. Instead of adding separate protective elements in front of the microphone, the foam itself serves as both the protection layer and the sensing element, eliminating the need for additional orifices, meshes, or screens that would complicate the device structure.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The ferroelectret polymer foam performs multiple functions simultaneously: it acts as a protective barrier against debris, a sound pressure sensor, and a transduction element. This multi-functionality eliminates the need for separate protective components while maintaining or enhancing reliability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If ferroelectret polymer foam is used as microphone and momentary switch sensor, then robustness against debris contamination is achieved, but additional integration complexity on complex surfaces must be managed

Engineering Contradiction:

Improverobustness against debrisVSAvoidintegration on complex surfaces

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The ferroelectret polymer foam can be conformally applied to complex curved surfaces such as battery drawers or ear tip surfaces. Its flexible foam structure allows it to adapt to irregular geometries while maintaining its debris-resistant properties and sensing capability, making it suitable for various integration locations within hearing instruments.

Inventive Principle:

Principle #30Flexible shells and thin films

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 ferroelectret polymer foam offers improved robustness against debris, maintaining performance even when contaminated, and reduces the risk of microphone and switch failures, enabling efficient sound pressure sensing and directional systems without the need for additional barriers.

Implementation Method 1

ferroelectret (also referred to as piezoelectret) polymer foam

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

Ferroelectret foam produces a positive d33 coefficient of piezoelectricity when the thickness of the foam is decreased

Methodology Applied

Scientific EffectPiezoelectricity: Piezoelectric Effect

Data Source

PatentUS9386384B2Hearing instrument transduction apparatus using ferroelectret polymer foam

Publication Date: 2016.07.05 STARKEY LABORATORIES INC

AI summary

The present subject matter provides method and apparatus for hearing assistance devices, and more particularly to hearing assistance devices using ferroelectret (also referred to as piezoelectret) polymer foam. Various embodiments include ferroelectret polymer foam on or in the hearing instrument as a microphone. Various embodiments include ferroelectret polymer foam on or in the hearing instrument as a momentary switch sensor.