Hearing Device Masking Signal Comb Filter Compensation
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Solution Overview
Problem
Hearing devices experience comb filter effects due to the superposition of output and ambient sound signals, causing unpleasant alterations in sound perception, particularly when the signals have similar volumes, and existing signal processing methods have limited ability to mitigate these effects without impairing user-specific amplification.
Innovation Solution
A method that generates a masking signal based on the expected direct sound and propagation delay to linearly superpose with the preliminary output signal, compensating for destructive interferences and reducing comb filter effects by adjusting the amplitude spectrum of the masking signal to match the expected direct sound, thereby minimizing artifacts and preserving desired sound characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency band filtering is applied in signal processing, then the sound signal is processed according to user's audiological needs, but comb filter effects occur due to time delay in processing
Solution Approach 1:
The patent applies preliminary anti-action by generating a masking signal that anticipates and counteracts the comb filter effects before they fully manifest. The masking signal is created based on the expected direct sound and propagation delay, and is added to the output signal to pre-compensate for the destructive interference that will occur when the delayed output signal combines with the direct sound at the user's ear.
Solution Approach 2:
The masking signal serves as an intermediary element that mediates between the processed output signal and the direct sound. By introducing this intermediate signal that matches the characteristics of the expected direct sound, the patent creates a bridge that reduces the harmful interaction between the delayed output signal and the direct sound, thereby minimizing comb filter effects.
2Ease of operation
If the hearing device does not completely close the ear canal, then occlusion effects are avoided, but ambient sound signals superimpose on the output sound signal
Solution Approach 1:
The patent extracts the problematic component (direct sound that causes superposition) by generating a masking signal that replicates its characteristics. Instead of trying to eliminate the direct sound path (which would require closing the ear canal and causing occlusion effects), the solution extracts the essential features of the direct sound and uses them to create a compensatory masking signal that reduces the harmful superposition effects.
3Reliability
If signal amplification is increased above 1 kHz, then hearing loss compensation is improved, but comb filter effects become more pronounced in the overlap range
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the masking signal parameters (amplitude, frequency content, timing) based on the propagation delay and expected direct sound characteristics. By changing the parameters of the masking signal to match the specific conditions of each situation, the patent effectively reduces comb filter effects across different frequency ranges while maintaining the necessary amplification for hearing loss compensation.
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 comb filter effects by compensating for signal cancellations and amplifications, ensuring that the output sound signal is less affected by interference, even during changes in amplification, thus improving sound quality without significantly altering the hearing device's signal processing.
Implementation Method 1
at least one input transducer of the hearing device generates an input signal from a sound signal from the environment
Implementation Method 2
an output transducer then converts the processed signal into an output sound signal
Implementation Method 3
the output sound signal that has been generated in the hearing device from the output signal of the signal processing unit is superimposed on the ambient sound signal with a slight delay. This may lead to 'comb filter' effects in the overall sound signal
Data Source
AI summary
In a method of operating a hearing device, an input transducer of the hearing device generates an input signal. A preliminary output signal is generated from this input signal through signal processing. An expected direct sound that is expected to be heard at one ear of a user of the hearing device is ascertained based on the input signal. A propagation delay of the preliminary output signal is ascertained with respect to the expected direct sound. A masking signal is generated based on the input signal and/or the preliminary output signal, taking into account the expected direct sound and/or the propagation delay of the preliminary output signal with respect to the expected direct sound. An output signal is generated based on the preliminary output signal and masking signal.