SONNOX RESTORE UNLEASH THE POWER OF ADVANCED AUDIO RESTORATION
EXPERIENCE CUTTING-EDGE TECHNOLOGY Sonnox Restore is a remarkable collection of three innovative plug-ins crafted for precise audio restoration. With its state-of-the-art algorithms and unique functionalities, you can swiftly and effectively eliminate unwanted artifacts such as pops, clicks, crackles, and background noise from any audio source while preserving the integrity of your desired sound.

USER-FRIENDLY INTERFACES Designed with simplicity in mind, the Sonnox Restore plug-ins are incredibly intuitive, making them a breeze to navigate. The DeClicker features a distinctive dialogue mode and an ‘exclude box’ that ensures you keep the essential audio intact. The DeBuzzer offers three frequency ranges and real-time tracking to tackle shifting problem frequencies effortlessly. Meanwhile, the DeNoiser, equipped with an independent de-hisser, delivers powerful real-time reduction of broadband noise for pristine audio clarity.

THE TRIO OF RESTORATION POWER DeNoiser
DeBuzzer
DeClicker

Sonnox Restore is a suite of three specialized plugins designed to address specific noise artifacts in recorded material, and it is available exclusively as part of the Restoration Bundle. The suite includes Oxford DeClicker, Oxford DeBuzzer, and Oxford DeNoiser. This suite is built on a new algorithmic approach to noise removal, emphasizing minimal processing artifacts and featuring an innovative graphical user interface. Typical applications involve removing pops, clicks, crackles, scratches, hum, buzzes, hiss, and other types of unwanted background noise. The Restoration Bundle supports RTAS, Audio Units, and VST platforms on both Mac and Windows PC at sample rates up to 96kHz, with protection via iLok.

Clicks Away

The DeClicker plugin is divided into three distinct processing sections, each targeting different types of noises: pops, clicks, and crackles. Sonnox defines a pop as a noise lasting between three and 10 milliseconds, a click as anything from 0.4 to three milliseconds, and noises shorter than 0.4 milliseconds are managed by the crackle section. Each section calculates what Sonnox calls an Excitation Profile, displayed in its own window. This profile measures how much the harmonic makeup of the sound deviates from its expected harmonic content. A high excitation value indicates a large, harmonically rich event, such as a click, which shows up as a triangular peak in the excitation profile.

The Threshold control adjusts the sensitivity of excitation peak detection, while a separate Sensitivity control determines which peaks are repaired and which are ignored. For effective click management, you should set the Threshold just above the noise floor to detect the full width of each click and then adjust the Sensitivity slider to repair only the clicks above a desired level. Smaller residual clicks can be addressed using the de-crackle function. Detected noises are displayed as color-coded ‘bubbles’—green for pops, blue for clicks, and white for crackles—with their size and height indicating their loudness. Disabling a section turns its bubbles red, showing they are not being corrected.

Certain instruments may produce ‘false positives,’ such as raspy brass, so the Restoration Bundle interface includes an Exclude box option to define a frequency area and level threshold to exclude specific detected clicks from repair. Although only one Exclude box can be active at a time, you can process the same material twice with different settings if needed. The Exclude box can also be automated for different sections of an audio file to prevent unnecessary correction of small noises usually masked by the desired signal.

Dialogue Mode addresses issues specific to removing clicks from spoken-word material, differentiating between speech and the spaces between words. Sonnox has implemented two alternate parameter sets, one active below a level threshold and the other above it. This allows you to drag a threshold line in a dynamic display of the input signal, and a side-chain filter helps tailor the signal used to key the dialogue/silence gate.

Operation is simplified by the ability to bypass each section and audition the noise being removed. Dropping the threshold too far may reveal unwanted transients and other elements from the desired sound. The Restoration Bundle excels at reducing vinyl crackles and short-duration digital clicks, although it may struggle with digital corruption issues exceeding the 10-millisecond pop duration. Despite uncertainties about how the software computes the material to fill gaps, it generally performs well. The Exclude feature is a useful addition as well.

All three plugins in the Restoration Bundle use internal buffer sizes of 1024 samples for 44.1kHz and 48kHz operation, and 2048 samples for 88.2kHz and 96kHz operation. Sonnox advises setting driver buffer sizes to match these values to optimize audio data transfer efficiency. Since these plugins are typically used post-recording, the resulting latency times are generally not an issue.

Buzz Off

In Auto mode, the Restoration Bundle‘s Sonnox Oxford DeBuzzer will automatically track the fundamental frequency of mains interference.

DeBuzzer, as its name implies, is designed to eliminate hum and buzz—unwanted noise harmonically related to the fundamental pitch of the offending sound, typically caused by mains interference. This process is divided into separate detection and removal sections. An FFT display assists in identifying the strongest harmonics, and precise tuning to the fundamental frequency is possible by holding down Shift, allowing adjustments to a resolution of 0.0001Hz. Alternatively, Auto mode follows hum and buzz that vary in frequency over time, and the tool can also address fundamentals with fluctuating levels.

A large, adjustable dial sets the center frequency for the detector within a range that can be narrowed, set to ‘normal,’ or expanded to a wide 5Hz window on either side of the center frequency. The frequency display shows peaks within this detection window, and an FFT display correlates audio data over time, making consistent frequencies stand out. The three highest peaks are marked with red lines. Additionally, a tone generator helps tune into the fundamental hum frequency until beat frequencies indicate a close match.

In Auto Mode, the detector monitors around the nominal fundamental frequency to keep the process aligned with the actual frequency, rather than the initial measurement. If the hum or buzz is steady in pitch, selecting Freeze will lock the frequency once you hear a reduction in hum level. Sonnox notes that Auto Mode is ideal for tracking weak, slowly shifting fundamentals and operates across all three frequency bands, with a Fast mode for rapidly varying mid- and high-frequency pollution, such as lighting buzz.

After establishing the fundamental frequency of the hum or buzz, problems can be treated using comb filtering—effective on high-amplitude harmonics extending across the audio spectrum—or parametric EQ, which offers more controlled removal of harmonics that may decrease in volume with higher frequencies.

The comb filter attenuates harmonics equally across the spectrum. For more targeted treatment, the parametric EQ allows for precise adjustments higher up the spectrum but requires more CPU resources. The parametric EQ can be set to address even or odd harmonics specifically, while comb filters address both. Comb filters are less effective for fundamentals above 2kHz, as their notches cover less of an octave at higher frequencies, causing less subjective harm. Conversely, parametric filters widen at higher frequencies, affecting a broader frequency range.

A Range control sets the frequency above which no further notches are applied, balancing between removing audible harmonics and avoiding unnecessary processing of higher frequencies.

Noise removal often involves compromises. It is generally best to set sensitivity as low as possible while still effectively removing buzz. An Alt mode reverses the sequence, so harmonics appear first in the output, followed by the fundamental as sensitivity decreases. The optimal mode depends on the buzz’s sonic characteristics and must be determined through testing. For broadband buzz, the default mode is usually best, while Alt mode may be preferable for hum with only a few audible harmonics. Auditioning the removed signal ensures that more than necessary isn’t being removed.

In testing, the Restoration Bundle‘s DeBuzzer effectively reduced hum and buzz from an electric guitar with single-coil pickups. The Auto mode’s comb filtering managed to cut the hum without significantly altering the tone, whereas the parametric EQ required adjustment to maintain tone clarity. The DeBuzzer performed impressively even in challenging conditions.

Cutting Off Your Noise

Next, we examine the Oxford DeNoiser from the Restoration Bundle. This broadband denoiser is essential for targeting hiss and other continuous, unpitched noise. Most affordable systems analyze a noise-only section of the recording to set up a threshold curve on a multi-band filter bank, attenuating signals falling below the threshold in each band. While this method works for constant noise, band-linking can be necessary to avoid ‘tinkling’ artifacts.

The Restoration Bundle plug-in features separate detection and removal sections for de-hissing, with an FFT display showing noise frequency and amplitude. It allows for a separate pass for hiss versus general broadband noise like air conditioning or camera noise. The detector noise profile can be set to automatic, tracking a varying noise floor, and adjusted for optimal sound with a Warmth control.

The Oxford DeNoiser offers various means to generate a noise profile. The default Auto mode analyzes the signal’s frequency spectrum in real-time to detect non-varying frequency components, with a smoothing control for response time adjustments. The threshold follows the signal level to maintain noise removal fixed below the desired audio, generally providing the cleanest results. However, fine-tuning the overall threshold by ear is often necessary to avoid over-processing. Colour and Air controls adjust the noise-reduction profile, allowing for high and low-end preservation and adding high-end air to the sound.

A Freeze button fixes the noise profile after detection, useful when a noise-only section is available or if the noise is constant throughout. Manual mode allows users to set a noise profile and adjust it by ear, similar to Freeze mode once the profile is created.

For stereo tracks, the DeNoiser processes each channel separately but combines them into a single left and right noise profile in Auto mode to preserve stereo integrity. For material with different noise levels in each channel, Freeze or Manual modes may yield better results, though stereo integrity might be compromised.

In all modes, the noise threshold can be adjusted using a 17-segment curve, and a bias curve can vary noise reduction at critical frequencies to minimize artifacts. The display options—linear, logarithmic, HF, or LF views—enable targeted noise reduction across the spectrum.

The Restoration Bundle includes a de-hiss section for aggressive noise removal, effective for dialogue or other sources with minimal high-frequency content. Adjust the cutoff frequency and reduction fader to balance between removing hiss and avoiding dulling the audio. The Warmth control in the output section adds back some ‘life’ after heavy processing.

A Mid/Sides mode allows cleaning up only the sides (difference) signal, useful for FM stereo broadcasts where the receiver switches to mono in poor reception areas, maintaining consistent noise content.

Overall, the broadband noise reduction was straightforward to use after reading the manual. Caution is needed to avoid excessive processing, particularly with very dirty material. Using the Air control or adjusting the threshold curve above 8kHz can restore some high-end life to the sound. The DeNoiser’s maximum noise reduction is 24dB, with typical reductions being half that amount for substantial improvement. Though it can dull high-frequency content, it is effective on instruments with limited high-frequency extension, such as electric guitars.

The Summing Up

Sonnox has added flexibility and genuinely useful features to the three primary restoration plug-in types in the Restoration Bundle, without complicating the process. While restoration software works best with less noisy original material, the additional adjustments minimize processing artifacts for more serious issues. The intuitive graphical user interfaces allow for both simple use and deeper adjustments as needed. At nearly $2000, the Restore suite is a significant investment but is worth considering if you’re rescuing recordings and cannot afford high-end alternatives like CEDAR.

Alternatives

Other restoration products are available from Waves, TC Electronic, Algorithmix, Izotope, Wave Arts, and BIAS, with CEDAR setting the high-end standard.

Pros

• Usable at a basic level or with deeper adjustments.
• Effective against primary types of recorded noise.
• Fairly priced for the tools provided.

Cons

• No obvious cons if unrealistic expectations are avoided for extremely noisy sources.

Summary

Sonnox’s Restoration Bundle offers effective and versatile restoration tools capable of excellent results. While no restoration software provides a magic fix for all problems, this suite performs admirably in typical situations.