Minimum-Phase FIR Noise Reduction for Low-Latency Audio
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Solution Overview
Problem
Existing noise reduction systems using linear phase filters introduce significant latency, leading to audible comb filtering effects that degrade audio quality, particularly in applications requiring natural listening experiences.
Innovation Solution
A noise reduction system utilizing a finite impulse response filter configured as a minimum phase filter, which reduces latency by employing a filter manager circuit to determine and update filter coefficients based on input signals, leveraging the inherent low-latency feature of minimum phase filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a linear phase filter is used for noise reduction, then noise suppression performance is improved, but latency increases significantly causing audible comb filtering effects
Solution Approach 1:
The patent changes the phase parameter of the filter from linear phase to minimum phase configuration. This parameter change fundamentally alters the filter's impulse response characteristics, concentrating the energy at the beginning of the impulse response and minimizing the tail, thereby reducing latency while maintaining noise suppression performance through adaptive coefficient adjustment.
Solution Approach 2:
The patent employs dynamic adaptation by continuously updating the filter coefficients based on changing signal conditions. The filter manager circuit adapts the minimum phase filter coefficients in real-time to track varying noise and speech characteristics, ensuring optimal performance despite the reduced latency constraints.
2Object-affected harmful factors
If the filter length N is increased to improve noise suppression, then noise reduction performance is enhanced, but delay increases to N/2 degrading audio quality
Solution Approach 1:
The patent transforms the filter from linear phase to minimum phase configuration, which fundamentally changes the distribution of impulse response energy. This allows the system to achieve equivalent or superior noise reduction performance with significantly reduced effective delay, as minimum phase filters concentrate their impulse response energy at the beginning rather than spreading it uniformly across the filter length.
Solution Approach 2:
The patent replaces the traditional linear phase filter mechanism with a minimum phase filter mechanism. This substitution fundamentally changes how the filter processes signals, allowing for shorter effective processing lengths while maintaining noise reduction efficacy through the different temporal energy distribution characteristics of minimum phase responses.
Data Source
AI summary
A noise reduction (NR) system includes a finite impulse response (FIR) filter and a filter manager circuit. The FIR filter is used to perform NR upon a filter input derived from an input signal. The filter manager circuit is used to determine a configuration of a minimum phase filter according to the input signal, and update the FIR filter by the configuration of the minimum phase filter.