Hearing Aid Gain Processor for Residual Feedback Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hearing aids face limitations in maximum gain due to residual feedback, which cannot be perfectly suppressed by existing feedback suppression circuits, leading to audible distortions and instability.
Innovation Solution
A new method for adaptive feedback suppression in hearing aids, where the residual feedback is estimated based on the input signal's power spectrum, and a gain processor adjusts the feedback compensated audio signal to compensate for the residual feedback, ensuring the output loudness equals that without residual feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If feedback suppression circuit is used to model and subtract feedback path, then feedback signal is reduced, but residual feedback remains causing output level to exceed desired level near instability
Solution Approach 1:
The patent implements a gain processor that uses feedback from the residual feedback signal to dynamically adjust the gain of the feedback compensated audio signal. The residual feedback signal is derived by subtracting the feedback suppression circuit output from the microphone signal, and this residual signal feeds back to the gain processor which adjusts the overall gain to compensate for the imperfect feedback suppression, thereby preventing output level exceedance near instability conditions
Solution Approach 2:
The patent introduces dynamic gain adjustment through the gain processor that adapts to changing feedback conditions. The system dynamically modifies the gain based on the estimated residual feedback signal characteristics, allowing the hearing aid to maintain stability across varying operating conditions rather than using a fixed gain structure
2Productivity
If gain is increased to restore audibility, then hearing aid performance is improved, but feedback instability and audible distortions occur
Solution Approach 1:
The gain processor utilizes feedback from the residual feedback signal to dynamically control the gain application. By continuously monitoring the residual feedback and adjusting the gain accordingly, the system can operate at higher gain levels while maintaining stability, as the feedback mechanism prevents the feedback loop from becoming unstable even when processing signals at elevated gain levels
Solution Approach 2:
The system performs preliminary feedback suppression by modeling and subtracting the feedback path before the gain is applied. This preliminary action removes the majority of the feedback signal in advance, allowing subsequent gain application without triggering feedback instability, thereby enabling higher effective gain while maintaining reliability
3Object-generated harmful factors
If feedback suppression circuit models feedback path with transfer functions, then feedback signal is suppressed, but perfect modeling is unachievable leaving residual feedback
Solution Approach 1:
The gain processor acts as an intermediary that bridges the gap between the feedback suppression circuit and the final output. It takes the feedback compensated audio signal and the estimated residual feedback signal as inputs, and produces a corrected output that compensates for the imperfections of the feedback path model without requiring complex modifications to the original feedback suppression architecture
Solution Approach 2:
The patent segments the feedback suppression function into two distinct stages: first, the feedback suppression circuit models and subtracts the feedback path using transfer functions; second, the gain processor separately estimates and compensates for the residual feedback. This segmentation allows each component to be optimized independently while working together to achieve better overall performance
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A hearing aid includes: an input transducer for generating an audio signal; a feedback suppression circuit configured for modelling a feedback path of the hearing aid; a subtractor for subtracting an output signal of the feedback suppression circuit from the audio signal to form a feedback compensated audio signal; a signal processor that is coupled to an output of the subtractor for processing the feedback compensated audio signal to perform hearing loss compensation; and a receiver that is coupled to an output of the signal processor for converting the processed feedback compensated audio signal into a sound signal; wherein the hearing aid further comprises a gain processor for performing gain adjustment of the feedback compensated audio signal based at least on an estimate of a residual feedback signal of the feedback compensated audio signal, wherein the estimate of the residual feedback signal is based at least on the audio signal.