Audio Gain Smoothing to Reduce Musical Noise Artifacts
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Solution Overview
Problem
Existing noise reduction methods in audio signal processing often produce artifacts such as speech distortion and musical noise due to estimation errors and non-stationarity of noise, leading to spurious peaks in the spectral representation of the signal.
Innovation Solution
The method involves post-processing raw gains determined by input processing using delta gain smoothing and decision-directed gain smoothing techniques to stabilize the gain variations, thereby reducing musical noise artifacts and improving the quality of the output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If noise reduction gains are applied to remove undesired signals, then noise suppression is improved, but speech distortion and musical noise artifacts are introduced
Solution Approach 1:
The patent applies preliminary smoothing action to the gain function before it is applied to the signal. By pre-smoothing the gain in the frequency and time domains, the patent prevents the formation of spurious peaks that would otherwise create musical noise artifacts, while still maintaining effective noise suppression.
Solution Approach 2:
The patent implements beforehand cushioning by applying smoothing filters to the gain function prior to signal processing. This cushioning effect reduces the impact of estimation errors and prevents abrupt gain variations that would cause musical noise, thereby protecting the output signal from artifacts while preserving noise reduction effectiveness.
2Object-affected harmful factors
If aggressive noise reduction is applied, then noise removal is improved, but speech distortion increases
Solution Approach 1:
The patent implements dynamic smoothing where the smoothing factor is adapted based on the local characteristics of the gain function and signal conditions. This dynamic approach allows aggressive noise reduction where appropriate while maintaining speech quality in regions where distortion would otherwise occur, making the noise reduction process adaptive rather than static.
Solution Approach 2:
The patent applies local quality by performing smoothing operations with different characteristics in different frequency regions and time frames. By adapting the smoothing parameters locally based on signal conditions, the patent achieves effective noise removal in some regions while preserving speech quality in others, avoiding uniform aggressive processing that would cause widespread distortion.
Data Source
AI summary
A method, an apparatus, and logic to post-process raw gains determined by input processing to generate post-processed gains, comprising using one or both of delta gain smoothing and decision-directed gain smoothing. The delta gain smoothing comprises applying a smoothing filter to the raw gain with a smoothing factor that depends on the gain delta: the absolute value of the difference between the raw gain for the current frame and the post-processed gain for a previous frame. The decision-directed gain smoothing comprises converting the raw gain to a signal-to-noise ratio, applying a smoothing filter with a smoothing factor to the signal-to-noise ratio to calculate a smoothed signal-to-noise ratio, and converting the smoothed signal-to-noise ratio to determine the second smoothed gain, with smoothing factor possibly dependent on the gain delta.