Frequency Domain Phase Synchronization for Microphone Noise Suppression
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Solution Overview
Problem
Existing microphone array systems struggle to effectively suppress noise from directions other than the main suppression direction, leading to insufficient noise reduction in speech recognition applications.
Innovation Solution
A signal processing apparatus that uses two spectrum signals from microphones to estimate the sound source direction and determine a sound suppressing phase difference range, synchronizing frequency components to generate a filtered spectrum signal by subtracting or adding synchronized signals, thereby enhancing noise suppression across various frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional microphone array systems use subtraction or addition processing based on time difference, then directivity control is achieved, but noise suppression from directions other than the main suppression direction is insufficient
Solution Approach 1:
The patent transforms the noise suppression approach from time-domain subtraction/addition to frequency-domain processing. By converting signals to frequency domain and applying phase difference-based filtering, the system achieves superior noise suppression from multiple directions simultaneously, not just the main suppression direction.
Solution Approach 2:
The system dynamically adjusts phase difference ranges based on target signal likelihood for different frequency components. This adaptive parameter adjustment allows optimal noise suppression across varying acoustic conditions and frequencies, overcoming the fixed limitation of conventional time-domain methods.
2Object-affected harmful factors
If more microphones are added to improve noise suppression, then coverage increases, but device complexity and cost increase
Solution Approach 1:
The patent achieves enhanced noise suppression with only two microphones by transforming to frequency domain and applying adaptive phase difference filtering. This parameter transformation allows two microphones to perform equivalently or better than conventional systems with many more microphones, significantly reducing device complexity.
3Object-affected harmful factors
If frequency-domain processing with phase difference estimation is applied, then noise suppression gain of 10 dB or more is achieved, but computational complexity increases
Solution Approach 1:
The system performs preliminary Fast Fourier Transform to convert time-domain signals to frequency domain before noise suppression. This preliminary transformation enables subsequent efficient phase difference calculation and filtering operations, achieving 10 dB or more noise suppression gain while managing computational complexity through structured processing stages.
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 significantly reduces noise interference, improving the signal-to-noise ratio and maintaining sound quality, even with a small number of microphones, and achieves a noise suppression gain of approximately 10 dB or more.
Implementation Method 1
Microphone arrays including at least two microphones receive sound, convert the sound into sound signals
Implementation Method 2
generates a synchronized spectrum signal by synchronizing each frequency component of one of the spectrum signals to each frequency component of the other of the spectrum signals
Implementation Method 3
generating a filtered spectrum signal by subtracting the synchronized spectrum signal from the other of the spectrum signals or adding the synchronized spectrum signal to the other of the spectrum signals
Data Source
AI summary
There is provided a signal processing apparatus, for suppressing a noise, which includes a first calculator to obtain a phase difference between two spectrum signals in a frequency domain transformed from sound signals received by at least two microphones to estimate a sound source by the phase difference, a second calculator to obtain a value representing a target signal likelihood and to determine a sound suppressing phase difference range at each frequency, in which a sound signal is suppressed, on the basis of the target signal likelihood, and a filter. The filter generate a synchronized spectrum signal by synchronizing each frequency component of one of the two spectrum signals to each frequency component of the other of the two spectrum signals for each frequency when the phase difference is within the sound suppressing phase difference range and to generate a filtered spectrum signal.