Hearing Aid Directional Microphone Feedback Control
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Solution Overview
Problem
Hearing aid devices with directional microphone systems face limitations in achieving the greatest possible degree of amplification and directivity, especially in quiet environments with high interference signals, as high directivity settings often lead to feedback and are restricted by the signal level of the acoustic input signal.
Innovation Solution
The hearing aid device sets the greatest possible degree of directivity based on the amplification gain rather than the signal level, allowing for adjustable directional effects through defined threshold values or a continuous functional relationship between amplification and directivity, enabling maximum directivity even in low signal situations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high amplification gain is applied to quiet acoustic input signals, then the hearing aid can provide sufficient amplification for hard of hearing users, but feedback occurs and stable operation cannot be ensured
Solution Approach 1:
The patent applies dynamics by making the directional characteristic of the microphone system adjustable and adaptable to different operating conditions. The system dynamically switches between omnidirectional and directional characteristics based on the amplification gain level and detected acoustic environment, allowing optimal performance across different signal levels while preventing feedback in high-gain situations through omnidirectional operation
2Measurement precision
If a directional microphone system is used to improve sound quality and reduce noise, then the signal-to-noise ratio is improved, but the degree of directivity must be limited when high amplification is applied to avoid feedback
Solution Approach 1:
The system dynamically adjusts the directional characteristic based on the amplification gain and acoustic environment. When amplification is high, the system switches to omnidirectional operation to prevent feedback. When amplification is lower and conditions permit, the system employs directional characteristics to improve signal-to-noise ratio, thus optimizing both quality and stability across different operating conditions
3Adaptability or versatility
If the directional effect is adjusted as a function of the signal level of the acoustic input signal, then directivity can be optimized for different listening situations, but the greatest possible degree of directivity is restricted at low signal levels to prevent feedback
Solution Approach 1:
The system implements dynamic adjustment of the directional characteristic based on multiple parameters including amplification gain, signal level, and acoustic environment classification. This allows the system to adapt to different listening situations while preventing feedback by switching to omnidirectional operation when high amplification is required, thus achieving both adaptability and optimal directivity where conditions permit
4Reliability
If omnidirectional operation is used instead of directional operation, then feedback is avoided and stable operation is ensured, but noise reduction and signal-to-noise ratio improvement are lost
Solution Approach 1:
The system dynamically selects between omnidirectional and directional operational modes based on the amplification gain and acoustic environment. When high amplification is needed for quiet signals, omnidirectional operation ensures stability and prevents feedback. When amplification levels are lower and the acoustic environment permits, directional operation is employed to maximize noise reduction and signal-to-noise ratio improvement, thus optimizing the trade-off between stability and 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
This approach allows for the full exploitation of the hearing aid's technical capabilities by decoupling directivity from signal level, maintaining high directivity in interference-heavy situations and ensuring stable operation by linking directivity directly to amplification settings, thereby enhancing sound quality and reducing noise.
Implementation Method 1
at least one microphone, which picks up an acoustic input signal and converts it into an electrical input signal
Implementation Method 2
it is proposed to increase the signal delay in at least one microphone signal in such a way that the transmission function in the frequency response of the microphone system is increased
Implementation Method 3
The further processing and amplification takes place to compensate for the individual hearing loss of a user, as a rule depending on the signal frequency of the input signal
Implementation Method 4
an output converter, so that the latter perceives the output signal as an acoustic signal. Earphones that generate an acoustic output signal are usually used as output transducers
Data Source
Figure 1
Figure 2~3
AI summary
The device (1) has directional microphones (M1-M3) picking up an acoustic input signal and creating electrical microphone signals (S1-S3). A signal processing unit (2) processes and amplifies the electrical microphone signal, and creates an electrical output signal. An earpiece (3) converts the electrical output signal into an acoustic output signal. The directional microphones provide directional effect based on the amplification of the electrical microphone signal, where the directional effect comprises a first-order directional effect set below a threshold value of the amplification. An independent claim is also included for a method for operating a hearing aid device.