A method of operating an audio signal processing apparatus, comprising: post-processing raw gains determined by input processing one or more input audio signals, the post-processing to generate post-processed gains to apply to a signal, the post-processing comprising: determining a post-processed gain for each frequency bin of a set of frequency bins using one or both of delta gain smoothing to determine a first smoothed gain and decision-directed gain smoothing to determine a second smoothed gain, and determining the post-processed gain from one or both of the first smoothed gain and the second smoothed gain, wherein the delta gain smoothing comprises applying a smoothing filter to the raw gain with a smoothing factor that depends on an absolute value of a difference between the raw gain for a current frame and a post-processed gain for a previous frame to determine the first smoothed gain, and wherein the decision-directed gain smoothing comprises converting the raw gain to a signal-to-noise ratio, applying a smoothing filter whose smoothing level is controlled by 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. post-processing raw gains determined by input processing one or more input audio signals, the post-processing to generate post-processed gains to apply to a signal, the post-processing comprising: determining a post-processed gain for each frequency bin of a set of frequency bins using one or both of delta gain smoothing to determine a first smoothed gain and decision-directed gain smoothing to determine a second smoothed gain, and determining the post-processed gain from one or both of the first smoothed gain and the second smoothed gain, wherein the delta gain smoothing comprises applying a smoothing filter to the raw gain with a smoothing factor that depends on an absolute value of a difference between the raw gain for a current frame and a post-processed gain for a previous frame to determine the first smoothed gain, and wherein the decision-directed gain smoothing comprises converting the raw gain to a signal-to-noise ratio, applying a smoothing filter whose smoothing level is controlled by 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. determining a post-processed gain for each frequency bin of a set of frequency bins using one or both of delta gain smoothing to determine a first smoothed gain and decision-directed gain smoothing to determine a second smoothed gain, and determining the post-processed gain from one or both of the first smoothed gain and the second smoothed gain, wherein the delta gain smoothing comprises applying a smoothing filter to the raw gain with a smoothing factor that depends on an absolute value of a difference between the raw gain for a current frame and a post-processed gain for a previous frame to determine the first smoothed gain, and wherein the decision-directed gain smoothing comprises converting the raw gain to a signal-to-noise ratio, applying a smoothing filter whose smoothing level is controlled by 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.