Hearing Instrument Echo Cancellation With Adaptive Residual Feedback Filtering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hearing instruments experience acoustic feedback and echo during voice calls due to the coupling of interlocutor's voice contributions into the microphone, causing a delay of several milliseconds to several seconds, which is irritating for the user.
Innovation Solution
Implement an adaptive first filter to generate a compensation signal for reducing echo, using filter coefficients and error signals to control a second filter for rejecting residual feedback, and apply frequency-band-oriented gain factors to attenuate the intermediate signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output signal is routed to an output transducer for acoustic reproduction, then the wearer can hear the voice contributions of the interlocutor, but acoustic feedback occurs from the output transducer to the microphone causing echo
Solution Approach 1:
The patent implements a feedback mechanism where the output signal is fed back through an adaptive filter to generate a compensation signal. This compensation signal is subtracted from the input signal to cancel the acoustic feedback path, allowing the system to maintain reliable communication while eliminating the harmful echo effect.
Solution Approach 2:
The patent introduces an adaptive filter as an intermediary element between the output transducer and the microphone signal path. This filter acts as a mediator that processes the output signal to predict and cancel the feedback component, preventing the harmful acoustic feedback from reaching the transmission signal.
2Object-affected harmful factors
If echo reduction filters are applied to the transmission signal, then echo is reduced, but processing time and computational complexity increase
Solution Approach 1:
The patent applies echo reduction filtering to the transmission signal before it is sent to the communication device. By performing the filtering operation in advance, the system reduces echo effectively while minimizing additional processing time during real-time communication, as the filter coefficients are pre-calculated based on the acoustic feedback path.
Data Source
AI summary
A method reduces echo in a hearing instrument. A first input transducer generates a first input signal from ambient sound. A communication unit receives an external input signal from an external device. The first input signal and the external input signal are used to generate an output signal. The output signal is used in a first filter to generate a compensation signal for reducing echo and/or acoustic feedback. The first input signal and the compensation signal are used to generate an error signal. Filter coefficients of the first filter and/or a comparison of the error signal with the compensation signal and/or with the first input signal are/is used to generate a control variable. The control variable is taken as a basis for applying a second filter for rejecting a residual echo or a residual feedback to an intermediate signal derived from the input signal, and a transmission signal is generated.