Hearing Aid Feedback Suppression Parameter Initialization
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Solution Overview
Problem
The initialisation process of Digital Feedback Suppression Circuit in hearing instruments often causes user discomfort due to the high level and duration of the probe signal required for accurate feedback path estimation, especially in open solutions where feedback paths have long impulse responses.
Innovation Solution
A new initialisation process that ramps the probe signal from an inaudible level, monitoring quality parameters to determine when to maintain or reduce the signal level, ensuring the probe signal level and duration are minimised for effective feedback path estimation without user discomfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high level probe signal is used for feedback path estimation, then measurement precision is improved, but user discomfort increases
Solution Approach 1:
The probe signal level is made dynamic rather than static. The system automatically adjusts the probe signal level based on the estimated feedback path characteristics and impulse response length. For open solutions with long impulse responses, the system uses a higher probe signal level to ensure adequate excitation and measurement accuracy, while for closed solutions with short impulse responses, it uses a lower level to minimize user discomfort.
Solution Approach 2:
The system changes the probe signal parameters (level and duration) based on the specific feedback path characteristics being measured. By adapting the signal level and duration to the measured impulse response properties, the system achieves accurate feedback path estimation while minimizing unnecessary high-level signal exposure that would cause user discomfort.
2Measurement precision
If a long duration probe signal is used for feedback path estimation, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The probe signal duration is made adaptive based on the measured feedback path characteristics. The system initially uses a longer probe signal to capture the complete impulse response including late reflections in open solutions, then shortens subsequent probe signals based on the identified impulse response length, reducing overall initialisation time while maintaining measurement accuracy.
Solution Approach 2:
The system performs a preliminary measurement phase with a longer probe signal to characterize the feedback path and determine the impulse response length. This preliminary action provides information that enables subsequent shorter measurements, reducing the total time required while ensuring accurate feedback path estimation from the outset.
3Reliability
If the probe signal level is increased to account for long impulse responses in open solutions, then reliability of feedback suppression is improved, but user discomfort increases
Solution Approach 1:
The system dynamically changes the probe signal level parameter based on the detected feedback path type and impulse response characteristics. For open solutions with long impulse responses, it temporarily increases the probe signal level during the measurement phase to ensure reliable feedback path capture, then reduces it to a comfortable level during normal operation, maintaining feedback suppression reliability while minimizing user discomfort.
Solution Approach 2:
The system uses periodic probe signal bursts at elevated levels interspersed with lower level periods during the initialisation process. This allows adequate excitation of the long impulse response paths in open solutions for reliable measurement, while limiting the cumulative exposure time at high levels to reduce user discomfort.
Data Source
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AI summary
The present invention relates to a hearing instrument, such as a hearing aid, with digital feedback suppression circuitry having parameters that are initialised, e.g. during fitting of the hearing instrument to a specific user, according to a method of modelling a feedback path from a receiver to a microphone of the hearing instrument, comprising the initialisation steps of transmitting an electronic probe signal to the receiver for conversion into an acoustic probe signal output by the receiver while recording the microphone output signal, and determining at least one parameter of the feedback path based on the recorded microphone output signal, and wherein the step of transmitting a probe signal to the receiver comprises the steps of increasing the level of the probe signal while monitoring values of a first quality parameter calculated based on the recorded microphone output signal, and refraining from further increasing the level of the probe signal when the determined first quality parameter has reached a predetermined first threshold value.