Sound Pickup Device Using Coherence Sum for Noise Suppression
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Solution Overview
Problem
Conventional sound pickup devices using beamformers struggle to effectively suppress background noise, especially in environments with strong noise sources like event venues or areas with music, leading to unpleasant abnormal sounds when target area sound is not present.
Innovation Solution
A sound pickup device with a directionality forming unit, target area sound extraction unit, determination information computation unit, area sound determination unit, and output unit that computes and uses amplitude spectrum ratio and coherence sum values to determine the presence of target area sound, suppressing non-target area sound components and only outputting target area sound when determined present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a beamformer is used to pick up sound from a specific direction, then directionality is achieved, but background noise suppression is insufficient in noisy environments
Solution Approach 1:
The patent segments the sound field into target area sound and non-target area sound components using multiple microphone arrays positioned at different locations. Each microphone array processes sound from its specific direction, and the results are combined to achieve comprehensive spatial filtering and noise suppression.
Solution Approach 2:
The patent combines outputs from multiple microphone arrays (MA1, MA2, etc.) that are positioned at different locations and oriented toward the target area from different directions. By merging these multiple directional inputs with complementary spatial filtering characteristics, the system achieves superior noise suppression while maintaining target sound quality.
2Manufacturing precision
If non-target area sound is suppressed to extract target area sound, then target sound quality improves, but abnormal sounds occur when target area sound is not present
Solution Approach 1:
The patent computes determination information (amplitude spectrum ratio and coherence sum) from the processed sound signals and uses this feedback to dynamically control the output. When the determination information indicates absence of target area sound, the system suppresses output to avoid abnormal sounds, while maintaining high extraction quality when target sound is present.
Solution Approach 2:
The patent performs preliminary computation of determination information (amplitude spectrum ratio and coherence sum) before final output to predict whether target area sound is present. This preliminary assessment allows the system to prepare appropriate output control actions, preventing abnormal sounds before they occur.
3Object-affected harmful factors
If multiple microphone arrays are used to improve noise suppression, then background noise is reduced, but device complexity increases
Solution Approach 1:
The patent employs multiple microphone arrays that serve dual functions: each array provides directional sound pickup for target area enhancement and simultaneously contributes to spatial noise filtering. This multi-functionality allows effective noise suppression without proportionally increasing overall system complexity.
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 solution effectively suppresses background noise components, reducing the occurrence of abnormal sounds by accurately determining the presence of target area sound and preventing the output of non-target area sound, even in noisy environments.
Implementation Method 1
A beamformer (BF hereafter) employing a microphone array is conventional technology that selectively picks up only sound from a specific direction (also referred to as a 'target direction' below) in an environment in which plural sources of sound are present. A BF is technology for forming directionality using time differences in signals arriving at respective microphones.
Implementation Method 2
In the subtraction device SUB, strong directionality can also be formed at the blind spot of bidirectionality using spectral subtraction (also referred to as simply 'SS' hereafter) processing. The subtraction device SUB may perform processing to substitute in 0 or a value reduced from the original value (flooring processing) when the result value from performing the subtraction processing employing Equation (4) below is negative.
Data Source
AI summary
A sound pickup device is provided, the device including (1) a directionality forming unit that forms directionality to output of a microphone array, (2) a target area sound extraction unit that extracts non-target area sound from output of the directionality forming unit, and that suppresses non-target area sound components extracted from output of the directionality forming unit so as to extract target area sound, (3) a determination information computation unit that computes determination information, (4) an area sound determination unit that determines whether or not target area sound is present using the determination information computed by the determination information computation unit, and (5) an output unit that outputs the target area sound extracted only in cases in which the target area sound is determined to be present by the area sound determination unit.