Adaptive Directivity Control for Compact Microphone Arrays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Compact IC recorders with closely disposed microphones face challenges in achieving directivity control due to small phase differences, leading to complex computations and reduced sensitivity in low-frequency sound collection, especially when multiple delay devices and long filter coefficients are required.
Innovation Solution
A directivity control method that alternately interchanges input signals from two microphones and updates a coefficient using a recurrence formula to emphasize or suppress sound from specific directions with reduced computational load, involving a coefficient updating circuit that calculates the error signal and adjusts the coefficient for each sample.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If two microphones are closely disposed to achieve compact IC recorder size, then portability and miniaturization are improved, but phase difference becomes extremely small making directivity control difficult
Solution Approach 1:
The patent changes the parameter of microphone spacing from fixed to variable through adaptive filtering. By dynamically adjusting filter coefficients based on incoming sound signals, the system compensates for the small physical distance between microphones, effectively enhancing phase difference detection sensitivity without increasing physical separation.
Solution Approach 2:
The patent replaces the mechanical approach of increasing microphone physical distance with a signal processing approach. Instead of mechanically separating microphones to increase phase difference, the system uses digital signal processing with adaptive filters to synthetically create sufficient phase difference for effective directivity control.
2Measurement precision
If multiple delay devices and long filter coefficients are used to achieve directivity control with closely disposed microphones, then directivity control capability is improved, but computing complexity increases
Solution Approach 1:
The patent implements dynamic adaptation where filter coefficients are continuously updated based on real-time sound signal analysis. This dynamic approach allows the system to achieve effective directivity control with adaptive filtering that converges to optimal values, avoiding the need for excessively long fixed filter coefficients or multiple delay devices.
Solution Approach 2:
The adaptive filtering system is self-adjusting, automatically optimizing its own filter coefficients based on the statistical properties of the incoming sound signals. This self-service mechanism eliminates the need for complex manual configuration or excessive computational resources, as the system autonomously finds the optimal filtering parameters for current acoustic conditions.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Directivity control method and device which can emphasize or suppress sound deriving from an arbitrary direction with a little computation using two microphones closely disposed are provided. An interchange circuit 2 alternately interchanges a pair of input signals InL, InR for each one sample to generate a pair of interchanged signals InA, InB. A coefficient updating circuit 3 multiplies the one InB of the interchanged signals by a coefficient m to generate an error signal between the interchanged signals InA, InB. A recurrence formula of the coefficient m containing the error signal is calculated to update the coefficient m for each one sample. Subsequently, the pair of input signals InL, InR are multiplied by the sequentially updated coefficient m, and output.