Directional Microphone Sound Pickup Device with Correlation-Based Noise Reduction
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Solution Overview
Problem
Conventional sound pickup devices using two non-directional microphones face reduced accuracy due to low frequency phase differences, leading to decreased accuracy in distinguishing between target sounds and distant noise.
Innovation Solution
A sound pickup device comprising a directional microphone and a non-directional microphone, along with a level control portion that calculates correlation between the signals to adjust gain and emphasize near-sound sources, reducing distant noise effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If two non-directional microphones are used, then the device structure is simple, but the accuracy in distinguishing target sound from distant noise is reduced due to low frequency phase differences
Solution Approach 1:
The microphone system is segmented into two distinct types: a directional microphone for capturing sound from a specific direction and a non-directional microphone for capturing omnidirectional sound. This segmentation allows each microphone to serve its specific function, with the directional microphone providing directionality information and the non-directional microphone providing overall sound level information, thereby resolving the accuracy issue without significantly increasing overall system complexity
Solution Approach 2:
Different microphones are assigned different local qualities (directivity characteristics) according to their specific functions. The directional microphone has high directivity quality for capturing sound from a particular direction, while the non-directional microphone has uniform directivity quality for capturing sound from all directions. This local quality differentiation enables accurate distinction between target sound and distant noise by comparing the directional and non-directional signals
2Device complexity
If two non-directional microphones are used, then the device complexity is low, but the phase difference in low frequency components is minimal leading to reduced accuracy
Solution Approach 1:
The system segments the microphone functions into directional and non-directional types, allowing the directional microphone to introduce controlled phase differences through its directional characteristic while the non-directional microphone provides a reference signal. This segmentation enables reliable noise reduction by comparing the phase relationships between the two microphone signals
Solution Approach 2:
The system uses the signal from the non-directional microphone as feedback to process and correct the signal from the directional microphone. By continuously comparing and adjusting based on the non-directional microphone's omnidirectional signal, the system maintains reliable noise reduction performance despite the phase difference limitations of non-directional microphones
Data Source
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AI summary
A sound pickup device (1) comprises a directional first microphone (10A), a non-directional second microphone (10B) and a level control portion (15) that obtains a correlation between a first sound pickup signal to be generated from the first microphone (10A) and a second sound pickup signal to be generated from the second microphone (10B), and performs level control of the first sound pickup signal or the second sound pickup signal according to a calculation result of the correlation. Therein the correlation includes coherence. The level control portion (15) performs the level control based on a ratio of a frequency component of which the coherence exceeds a predetermined threshold value.