De-noise via spectral subtraction with learning
An introduction to the technique is described in this blog article. But rather than simply assuming a constant value for the noise spectrum (as presented in that article), this plugin allows for the noise spectrum to be “learned” from a noisy segment of the audio input.
How to use the plugin
Load the plugin into your preferred Digital Audio Workstation (I use Ableton Live 9). First, select an (ideally) noise-only section (played in a loop, preferably) of the audio track to be cleaned, set the toggle to “Learning” and adjust the Analysis Frame parameters (or just keep the default settings). Let the “Learning” proceed for a few seconds. Notes: (i) the “De-Noise” knob has no effect during learning. Leave it be. (ii) The noise spectrum is learned independently for the left and right channels of the audio input. See the screenshot below illustrating the Learning Mode controls. Included is the display of the Ableton Live clip “JUST NOISE INTRO” to exemplify that learning should be performed on a noise-only segment of audio.
Then apply the now-trained de-noiser to the noisy signal by setting the toggle to “Processing” and adjusting the “De-Noise” knob clockwise until the noise is removed but without causing audible artifacts (in which case, turn it down a bit). Note: the de-noising is applied independently to the left and right channels using the separately-learned noise spectra. However, the same suppression factor (set via the”De-Noise” knob) is applied to both processing channels. See the screenshot below illustrating the Processing Mode controls. Included is the display of the Ableton Live clip being cleaned.
DO NOT adjust the Analysis Frame controls after learning. Leave them alone during processing. Otherwise you may disrupt the de-noiser and you may have to redo the learning (unless you can set the controls back to where they were for learning).
DO NOT disable then reenable the plugin after learning. Keep the plugin enabled during processing. Otherwise the learned noise spectrum will be lost and you will have to redo the learning.
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