Nonlinear Gain Processing for Audio Signal Suppression
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Solution Overview
Problem
Adaptive filters used in audio signal processing for noise suppression and echo cancellation face inaccuracies and performance limitations due to the nonlinearity of acoustic systems, which are often caused by unwanted signals and changing environmental conditions.
Innovation Solution
A device and method that utilize a processor to estimate envelope values for audio signals, compute gains based on these estimates, and apply nonlinear processes to suppress unwanted components, allowing for effective noise reduction and echo cancellation by converting signals between time and time-frequency domains and applying gains across frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adaptive linear filters are used to suppress unwanted signals, then noise reduction and echo cancellation can be achieved, but performance limitations and inaccuracies occur due to system nonlinearity
Solution Approach 1:
The patent applies a nonlinear function to the gain values computed by the adaptive filter. Specifically, it raises the gain to a power greater than one (e.g., squaring the gain) to emphasize strong signal components while suppressing weak unwanted signals more effectively. This parameter transformation allows the system to adapt to nonlinear acoustic environments while maintaining the computational efficiency of linear filtering.
Solution Approach 2:
The patent combines linear adaptive filtering with nonlinear gain processing to create a composite signal processing system. The linear filter handles the basic adaptation and gain computation, while the nonlinear processing stage addresses the limitations of linear systems in handling nonlinear distortions. This composite approach leverages the strengths of both linear and nonlinear methods.
2Adaptability or versatility
If the acoustical environment changes, then the system must adapt to new conditions, but linear adaptive filters become nonlinear and less effective
Solution Approach 1:
The patent introduces a dynamic nonlinear processing stage that operates on the gain values produced by the adaptive filter. This nonlinear stage dynamically adjusts the suppression of unwanted signals based on the instantaneous gain values, allowing the system to adapt to environmental changes while maintaining effective suppression through nonlinear gain manipulation rather than relying solely on linear adaptation.
3Measurement precision
If nonlinear solutions are added to improve filter performance, then suppression accuracy improves, but system complexity increases
Solution Approach 1:
The patent implements a simple parameter transformation by raising gain values to a power greater than one. This nonlinear operation is computationally efficient and can be implemented with minimal additional processing complexity while significantly improving suppression accuracy for nonlinear distorted signals.
Data Source
AI summary
A method, and one or more non-transitory computer-readable media storing instructions, and a device for removal of unwanted components in an audio signal, the device comprising a processor, coupled to memory, configured to receive reference and processed inputs into memory where the processed input is a result of a reduction process of unwanted components of the audio signal, estimate envelope values for processed and reference inputs at a plurality of time and frequency instances, for each time and frequency instance: compute a first gain in relation to a ratio of the estimated envelope value of the processed input to the estimated envelope value of the reference input, apply a nonlinear process to said first gain to produce a second gain, compute an output gain as the ratio between second gain and first gain and, apply the output gain to processed input, thereby producing a filtered output with unwanted components suppressed.