Hearing Device Dual Microphone Feedback Reduction
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Solution Overview
Problem
Conventional hearing aids face challenges with acoustic feedback and spatial cue preservation due to the placement of microphones, leading to suboptimal sound quality and directional response.
Innovation Solution
A hearing device with two input sound transducers, one in the ear canal and one behind the pinna, processes level differences between the signals to generate an output sound signal, improving sound quality and directional response by compensating for feedback and optimizing microphone placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single microphone is placed in the ear canal, then the device can capture sound for amplification, but acoustic feedback occurs and spatial cues are degraded
Solution Approach 1:
The patent divides the sound capture function into two separate microphones positioned at different locations: one in the ear canal and one behind the pinna. This segmentation allows the system to process signals from multiple spatial positions, reducing acoustic feedback while preserving spatial hearing cues that a single microphone cannot capture.
Solution Approach 2:
The patent adds a spatial dimension to sound capture by placing microphones at different anatomical positions (ear canal vs. behind pinna). This dimensional separation creates distinct acoustic pathways that reduce feedback loops while maintaining directional information, transforming a single-point capture into a multi-point spatial sampling system.
2Measurement precision
If microphones are placed to optimize directional response, then spatial hearing is improved, but feedback control becomes difficult
Solution Approach 1:
The patent segments the microphone system into two distinct positions with different directional characteristics. The ear canal microphone captures front-facing sounds with natural pinna filtering, while the behind-pinna microphone provides omnidirectional coverage. This segmentation simplifies feedback control by creating spatially separated capture points that reduce feedback coupling.
Solution Approach 2:
The patent applies local quality by giving each microphone position a specialized function: the ear canal microphone optimizes for forward-facing speech capture with pinna enhancement, while the behind-pinna microphone provides ambient sound capture and feedback suppression. This localized functional differentiation improves directional response without complicating overall system control.
3Object-generated harmful factors
If the ear canal is closed to prevent feedback, then feedback is reduced, but natural sound and device-generated sound create comb filter effects
Solution Approach 1:
The patent extracts the feedback-prone ear canal environment from the sound capture process by placing one microphone behind the pinna, outside the closed ear canal system. This extraction removes the microphone from the feedback loop created by the occluding ear canal, eliminating comb filter effects while maintaining feedback reduction benefits.
Solution Approach 2:
The patent introduces the behind-pinna microphone as an intermediary sound capture point that mediates between the closed ear canal system and the external environment. This intermediary position provides acoustic information without being part of the feedback path, allowing feedback reduction while preserving natural sound quality.
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
The device enhances sound quality and spatial hearing by reducing feedback and improving directional response, allowing for better consonant audibility and directivity, especially for lower frequencies.
Implementation Method 1
a first input sound transducer (12), configured to be arranged in an ear canal or in an ear of a user, to receive acoustical sound signals from the environment for generating a first electrical acoustic signal
Implementation Method 2
a second input sound transducer (14), configured to be arranged behind a pinna or on/ behind or at the ear of the user, to receive acoustical sound signals from the environment for generating a second electrical acoustic signals
Implementation Method 3
an output sound transducer (18), configured to be arranged in an ear canal of the user, to generate an acoustical output sound signal in accordance with the electrical output sound signal
Implementation Method 4
The pinna serves to collect sound by acting as a funnel, which may amplify sound pressure level by about 10 to 15 dB in a frequency range of 1.5 kHz to 7 kHz
Implementation Method 5
Sound waves running through the ear canal are amplified in the frequency range of about 3 kHz to 4 kHz, corresponding to the fundamental frequency of a tube closed on one end
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A hearing device comprising a first and a second input sound transducers, a processing unit, and an output sound transducer. The first transducer is configured to be arranged in an ear canal or in the ear of the user, to receive acoustical sound signals from the environment and to generate first electrical acoustic signals from the received acoustical sound signals. The second transducer is configured to be arranged behind a pinna or on, behind or at the ear of the user, to receive acoustical sound signals from the environment and to generate second electrical acoustic signals from the received acoustical sound signals. The processing unit is configured to process the first and second electrical acoustic signals. The output sound transducer is configured to be arranged in the ear canal of the user and to generate acoustical output sound signals from electrical acoustic signals.