Hearing Device Frequency Gain Adjustment for Comb Filter Reduction
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Solution Overview
Problem
Hearing devices experience unwanted comb filter effects and reduced sound gain at low frequencies due to the superimposition of receiver sound and direct sound, with receiver sound often being masked by direct sound, leading to suboptimal sound perception.
Innovation Solution
A method for adjusting frequency-dependent gain in hearing devices, which involves selecting offset gain values and fitting gain values to determine adjusted gain values that account for direct sound levels, ensuring the receiver sound is sufficiently below direct sound in the bass range to avoid comb filter effects, and applying these adjusted gain values for frequency-dependent amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the hearing device uses a coupling that occludes the ear canal to provide electroacoustic amplification, then sound gain is improved, but comb filter effects occur due to superimposition of receiver sound and direct sound
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the gain values for different frequency ranges based on the detected level of direct sound. When direct sound is detected at low frequencies, the system reduces the gain in that frequency range to prevent the receiver sound from being masked, thereby eliminating comb filter effects while maintaining amplification benefits.
2Power
If the receiver sound is amplified at low frequencies, then perceived sound gain is improved, but the receiver sound gets masked by direct sound
Solution Approach 1:
The patent implements feedback by continuously monitoring the level of direct sound in the ear canal and using this information to adjust the amplification gain. The system detects when direct sound masks the receiver sound and automatically reduces the gain to ensure the amplified sound remains audible and provides perceived benefit to the user.
3Object-generated harmful factors
If the coupling allows direct sound to pass through to avoid occlusion, then comb filter effects are reduced, but ventloss and leakage of amplified sound occur
Solution Approach 1:
The patent applies dynamics by making the coupling characteristics adjustable rather than fixed. The system dynamically modifies the occlusion level of the coupling based on listening conditions, allowing it to adapt between providing adequate amplification and minimizing direct sound interference, thereby resolving the trade-off between ventloss and comb filter effects.
Data Source
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AI summary
A method for adjusting a frequency dependent gain of a hearing device (10) comprises: receiving an amplification level (38) selected by a user of the hearing device (10); selecting offset gain values (40) for frequencies in a bass range (34) based on the amplification level (38); reading fitting gain values (30) for the frequencies stored in the hearing device (10), wherein the fitting gain values (30) have been selected to compensate a hearing loss of the user; determining direct sound indicator values (32) for the frequencies, wherein an direct sound indicator value (32) for a frequency specifies a level of direct sound in front of an ear drum in an ear canal of the user at that frequency; setting an adjusted gain value (36) in each frequency depending on the offset gain value (40), the fitting gain value (30) and the direct sound indicator value (32); applying the adjusted gain values (36) to an amplifier (20) of the hearing device (10), such that a sound signal in each frequency is amplified with the corresponding adjusted gain value (36).