Hearing Aid Microphone Segmentation for Feedback Control
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Solution Overview
Problem
Hearing instruments face a trade-off between achieving good sound quality and directionality, with traditional microphone placements either compromising sound quality due to occlusion issues or limiting amplification, and existing solutions do not effectively address feedback and noise separation.
Innovation Solution
A hearing assistance device with an audio input transducer located in the ear canal and supplementary input transducers placed behind the ear, utilizing the 'law of the first wavefront' to delay signals between 1 and 20 milliseconds for enhanced amplification and directionality, while incorporating multiple input transducers for noise reduction and feedback suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a microphone is placed at the entrance to the ear canal, then sound quality is improved, but amplification is limited due to acoustic feedback
Solution Approach 1:
The system divides the microphone function into two separate microphones: one at the ear canal entrance for high-quality sound capture, and another behind the pinna for feedback control and directionality. This segmentation allows each microphone to serve its specific function without the limitations that would constrain a single microphone.
Solution Approach 2:
The second microphone positioned behind the pinna acts as an intermediary for capturing feedback signals and providing directional information. It mediates between the sound source and the processing system, enabling feedback suppression and directionality control while the primary microphone maintains optimal sound quality.
2Adaptability or versatility
If a directional microphone system is implemented, then directionality and noise separation are improved, but sound quality deteriorates due to frequency colorations and phase changes
Solution Approach 1:
The directional functionality is separated from the primary sound capture function. The first microphone maintains omnidirectional characteristics for natural sound quality, while the second microphone provides directional information and feedback control, allowing directionality without compromising the primary audio signal.
Solution Approach 2:
Instead of using a single directional microphone that degrades sound quality, the system uses a second microphone to create a copied directional reference signal. This copied signal is used for feedback suppression and spatial processing without directly affecting the primary audio path.
3Adaptability or versatility
If microphones are spaced 1 cm apart for directional system, then directionality is improved, but system complexity and noise increase
Solution Approach 1:
The system places microphones at specific locations with distinct local characteristics: one at the ear canal entrance for optimal sound capture and another behind the pinna for feedback control. Each location provides specific local information that contributes to the overall directional and feedback control functionality.
Solution Approach 2:
The second microphone creates a copied reference signal that simplifies the processing requirements. Rather than complex beamforming with multiple widely-spaced microphones, the system uses the copied signal from the second microphone for feedback suppression and directional control.
Data Source
AI summary
The application relates to a hearing assistance device (HAD) comprising (a) an input transducer system comprising (a1) an audio input transducer (AIT), and (a2) a first supplementary input transducer (SIT1), (b) an output transducer (OT) for converting a processed output signal to a stimulus perceivable by said user as sound, and (c) a signal processing unit (SPU) operationally connected to said audio input transducer (AIT), to said first supplementary input transducer (SIT1), and to said output transducer (OT), said signal processing unit (SPU) being configured for processing said electric audio input signal, and said first supplementary electric input signal, and for providing said processed output signal. The audio input transducer (AIT) is adapted for being located in an ear of the user. In a NORMAL mode of operation, electric audio input signal is processed in the signal processing unit and the supplementary electric input signal(s) are used to control the processing.