Spectral repair is a tool for interpolating selected areas on a time-frequency spectrogram. It is able to provide higher quality than the Declicker tool for long corrupted segments of audio (above 10 ms).
Spectral repair can be used to remove (or attenuate) certain unwanted sounds from recordings, such as squeaky chairs, coughs, dropped objects, mobile phones ringing, etc. It can also close up gaps in audio by using advanced resynthesis techniques.
Understanding Spectral Repair Modes
Spectral Repair has several tabs representing different modes of interpolation.
Attenuate mode is suitable for recordings with background noise or where noise is the essential part of music (drums, percussion) and should be accurately preserved. It's also good when unwanted events are not obscuring the desired signal completely. For example, this mode can be used to bring noises like door slams or chair squeaks down to a level where they are inaudible and blend into background noise.
Replace mode can be used to replace badly damaged sections (such as gaps) in tonal audio.
Pattern mode is suitable for badly damaged audio with background noise or for audio with repeating parts. It searches surrounding areas for a similar piece of audio and blends it into the selection.
Partials+Noise mode is the advanced version of Replace mode. It restores harmonics of the audio more accurately with control over the Harmonic sensitivity parameter. This mode links detected harmonics by synthesizing them through the selection, and interpolates the rest of the signal using the Replace method.
Depending on the mode and settings, Spectral Repair will have varying limits to the amount of audio that can be processed in your selection.
Unlimited - Attenuate when in Vertical mode
10 seconds - Attenuate Horizontal or 2D, Replace modes;
4 seconds - Pattern, Partials+Noise modes.
Applying Spectral Repair
To start working with Spectral Repair, switch to the spectrogram view by dragging the waveform/spectrogram opacity slider to the right. Next, identify the unwanted event on a spectrogram and select it using a time-frequency selection tool (it is not necessary to select a surrounding region, select only the event you want to repair). You can audition this selected time-frequency tile by pressing the "Play selection" button in the RX transport.
Note: Depending on the mode chosen, Spectral Repair
Note: Some unwanted events consist of several separate regions on a spectrogram. In some cases, it's possible to achieve more accurate results by repairing several smaller selections one by one, instead of one large selection. Also, you can use the Find Similar Event tool to save time when searching for and fixing many similar events in large files.
Once you've found the event(s) to repair, select the appropriate interpolation mode (tab). Sometimes it's worth trying several different methods or number of bands to achieve the desired result. Higher number of bands doesn't necessarily mean higher quality! We encourage you to use the Compare Settings window to experiment and find the best settings for the project at hand.
Common parameters for many methods include "Surrounding region length" that determines how far around the selection will Spectral Repair look for a good signal. "Before/after weighting" allows to use more information from either before or after the audio for interpolation. For example, if your unwanted event is just before a transient (such as a drum hit) in the audio, you may want to set this parameter to use more of the audio before the selection to prevent smearing of the transient.
See the Reference Guide for descriptions of Spectral Repair controls.