Active Emission Cancellation for Hearing Device Sound Leakage
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Solution Overview
Problem
Hearing devices face instability and noise leakage issues due to sound emission from the ear canal to the environment, particularly in scenarios where loud sounds are amplified, leading to disturbance for others and potential feedback problems, even when the device's feedback control system is stable.
Innovation Solution
The implementation of an Active Emission Cancellation (AEC) system in hearing devices, which includes an active emission canceller and an environment-facing loudspeaker that generates an anti-emission signal to cancel or attenuate sound leaked from the ear canal to the outside, using either fixed or adaptive filtering techniques to determine the cancelling signal based on the sound picked up by an eardrum-facing microphone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If sound amplification is increased to compensate for severe hearing loss, then the hearing aid effectiveness is improved, but sound leakage to the environment increases causing disturbance to others
Solution Approach 1:
The patent applies preliminary anti-action by generating an anti-phase sound signal before the leaked sound reaches the environment. The AEC system creates a cancelling signal that is the inverse of the expected leaked sound, playing it through an environment-facing loudspeaker to preemptively neutralize the harmful emission before it disturbs others.
Solution Approach 2:
The patent converts the harmful leaked sound into a beneficial cancellation effect. By capturing the processed signal that would leak and generating its anti-phase version, the system transforms the harmful emission into a useful cancelling wave that reduces environmental sound pollution while maintaining the necessary amplification for the user.
2Stability of the object's composition
If feedback cancellation system is used to stabilize the hearing device, then device stability is improved, but sound leakage to the environment may still occur at high amplification levels
Solution Approach 1:
The patent segments the sound control function into two independent systems: a feedback cancellation system for internal stability (preventing oscillations between microphone and loudspeaker) and an active emission cancellation system for external sound leakage. This segmentation allows each system to optimize its function without interfering with the other, addressing both stability and environmental leakage independently.
Solution Approach 2:
The patent introduces an intermediary environment-facing loudspeaker that acts as a mediator between the processed sound signal and the external environment. This intermediary device plays the anti-phase cancelling signal, serving as a bridge that neutralizes leaked sound without affecting the internal feedback loop stability.
3Object-generated harmful factors
If an active emission canceller with environment facing loudspeaker is added, then sound leakage cancellation is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the environment-facing loudspeaker to serve multiple functions: it acts as both an additional output transducer for sound cancellation and integrates with the existing signal processing chain. The AEC system reuses the processed signal from the hearing aid's forward path, reducing the need for completely separate components and minimizing overall system complexity despite the added functionality.
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
Effectively reduces the audible emission of sound from the hearing device to the environment, minimizing disturbance to others and maintaining device stability by actively cancelling sound leakage, even in scenarios with high sound amplification.
Implementation Method 1
the electric sound cancelling signal is configured to cancel or attenuate sound leaked from the speaker sound outlet to the environment when played by the environment facing loudspeaker
Data Source
AI summary
A hearing device comprises a forward path comprising an input transducer providing at an electric input signal representative of environment sound, a signal processor for processing said at least one electric input signal and providing a processed signal, and a loudspeaker connected to a speaker sound outlet providing an output sound to an eardrum of the user in dependence of said processed signal. The hearing device comprises an ITE-part adapted for being located in an ear canal of the user, an active emission canceller providing an electric sound cancelling signal, and an environment facing loudspeaker providing an output sound to the environment. The electric sound cancelling signal is determined in dependence of said processed signal to attenuate sound leaked from the speaker sound outlet to the environment when played by the environment facing loudspeaker. The environment facing loudspeaker has a sound outlet on an environment facing surface of the ITE-part.