MusicRadar

Restore features DeBuzzer, DeClicker and DeNoiser.

View in gallery

• Review

Prior to the digital revolution, noise was a by-product of the physical media used to store music - remember the crackle of records and the background hiss of cassette? The transition to digital consumer formats banished such physicality-related artifacts, but noise is still very much a concern when recording.

Background hum and noise can contaminate recorded parts, and can be caused by dodgy cables or grounding issues, or electrical clicking from devices on the same mains circuit (kettles, fridges, etc). Video can suffer to the point where dialogue is masked by wind or motor noise from the camera and, of course, material transferred from tape or vinyl may very well still suffer from the artifacts mentioned earlier.

To combat noise problems post-recording, or to restore audio sourced from elderly formats, we can turn to noise reduction software such as Sonnox's Restore suite. It features three plug-ins - Oxford DeClicker, DeBuzzer and DeNoiser - which are designed to suppress clicks, pops, crackles, scratches, hums, buzzes and noise. Restore can work at up to 96kHz, and if you need to use more than one plug-in, Sonnox advises placing the DeClicker first, then the DeBuzzer and/or DeNoiser, depending on which nuisance elements are most prevalent.

DeClicker

DeClicker offers three sections, De-Pop, De-Click and De-Crackle, dealing with noise events of durations up to 10ms, 3ms and 0.4ms respectively. Each section has its own threshold and sensitivity controls, for dialling in optimal detection. Once this is done, DeClicker's algorithms distinguish between noise events and audio content, the former showing up as colour-coded dots on the graphical display.

With some types of material (eg, distorted guitars), the DeClicker can falsely flag up wanted audio events as clicks or crackles, but this problem is easily solved by utilising the Exclude Box function - a scalable box that you draw on the main graphical display to exclude events within a certain duration/level range from processing.

Activate the DeClicker's Dialogue Mode and a bunch of extra controls pop up. This mode is designed specifically for dialogue restoration work, and works by separately categorising events as dialogue and non-dialogue, then enabling you to process them separately with two full sets of DeClicker controls. Thus you can use more aggressive settings on the non-vocal sections without adversely affecting the audibility of the vocal sections - very clever.

In practice, it's pretty easy to do. You set the voice threshold control much as you'd set that of a noise gate, so any audio events breaching it are processed with the Above Set parameters, and the others with the Below Set. To fine-tune the way the DeClicker categorises events, there are sidechained low- and high-frequency filters and a real-time spectrum analyser, not to mention a level profile chart, both of which appear at the bottom of the main window.

This mode can work magic on video footage, and despite being dubbed Dialogue Mode, it's suitable for other restoration situations where you need different settings for loud and quiet events.