Receiver Shielding for Hearing Aid EMI Reduction

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Solution Overview

Problem

Miniature listening devices like hearing aids are susceptible to electromagnetic interference from their receivers, particularly due to class D amplifiers, which disrupt wireless communication and are difficult to mitigate without adding complexity or cost.

Innovation Solution

An electrically conductive shield is placed around the receiver, connected to the audio signal processing circuitry or system ground, to passively suppress electromagnetic emissions, reducing interference without modifying the circuitry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a compensation coil and compensation circuit are added around the receiver, then electromagnetic interference is actively compensated, but device complexity and cost increase

Engineering Contradiction:

Improveelectromagnetic interferenceVSAvoidreceiver complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent uses the electromagnetic emissions from the class D amplifier itself to generate a counteracting field. The amplifier's own output drives a compensation coil that produces an opposing magnetic field, converting the harmful emissions into a beneficial cancellation mechanism without requiring external compensation circuits

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The receiver's class D amplifier serves dual purposes: it drives both the audio output and the compensation coil. The amplifier's inherent switching emissions are utilized to generate the counteracting field, eliminating the need for separate compensation circuitry and reducing overall device complexity

Inventive Principle:

Principle #25Self-service

2Object-affected harmful factors

If noise cancellation algorithms are implemented in audio signal processing circuitry, then interference is reduced, but operational complexity increases

Engineering Contradiction:

ImproveinterferenceVSAvoidoperational complexity

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The patent replaces software-based noise cancellation algorithms with a hardware-based electromagnetic cancellation system. By using a compensation coil driven by the class D amplifier to generate counteracting magnetic fields, the solution eliminates complex signal processing operations and simplifies the operational framework

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Use of energy by moving object

If the receiver housing is made transparent to electromagnetic signals, then audio frequency performance is maintained, but electromagnetic interference increases

Engineering Contradiction:

Improveaudio frequency performanceVSAvoidelectromagnetic interference

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent applies electromagnetic shielding selectively around specific components (the class D amplifier and receiver) rather than making the entire housing opaque. This localized approach maintains audio frequency performance while providing targeted interference suppression in the radio frequency range where interference occurs

Inventive Principle:

Principle #3Local quality

4Use of energy by moving object

If class D amplifiers are used in receivers, then power consumption is reduced and implementation is simplified, but electromagnetic emissions increase

Engineering Contradiction:

Improvepower consumptionVSAvoidelectromagnetic emissions

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful electromagnetic emissions from the class D amplifier into a useful cancellation mechanism. The amplifier's switching signals, which cause interference, are also used to drive a compensation coil that generates counteracting magnetic fields, thereby eliminating the harmful effects while maintaining the power-efficient class D topology

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 shield effectively suppresses electromagnetic interference by up to 10 dB across specific frequency ranges, maintaining audio frequency performance and simplifying implementation, with grounded shields offering broader bandwidth suppression.

Implementation Method 1

An electrically conductive shield is placed around the receiver, connected to the audio signal processing circuitry or system ground, to passively suppress electromagnetic emissions

Methodology Applied

Scientific EffectElectromagnetic shielding: Faraday Cage

Data Source

PatentUS7460681B2Radio frequency shielding for receivers within hearing aids and listening devices

Publication Date: 2008.12.02 SONION NEDERLAND BV

AI summary

Method and apparatus are disclosed for reducing or eliminating the interference produced by a receiver in a listening device, such as a hearing aid. The method and apparatus of the invention involves placing an electrically conductive shield around the receiver. Such a shield helps suppress the electromagnetic signals emitted by the receiver, thereby reducing or eliminating the interference from the receiver. The shield is a passive shield and may be one or more wires that are wound around the receiver and shorted together, or it may be an electrically conductive mesh, jacket, sleeve, or the like, that is placed around the receiver. The shield is then connected either to one of the input terminals of the receiver, or to a system ground of the receiver.