iZotope RX 3 Advanced: The Cadillac of Noise-Reduction Software

I’ve been a huge fan of iZotope RX 2 Advanced since its introduction more than three years ago, consistently using the comprehensive suite of noise-reduction software on all my post-production sess

Fig. 1: The new Dereverb plug-in reduces reverb and room tone in four frequency bands.

I’ve been a huge fan of iZotope RX 2 Advanced since its introduction more than three years ago, consistently using the comprehensive suite of noise-reduction software on all my post-production sessions. Now a major update brings new modules, comprehensive metering, and augmented and optimized algorithms to the mix.

RX 3 Advanced includes a stand-alone application and a bundle of plug-ins in AU and VST formats, operable in 32- or 64-bit mode. I reviewed the AU plug-ins for RX 3 Advanced Version 3.02 in Digital Performer V. 8.06, and the stand-alone application, using an 8-core Mac Pro running OS X 10.8.5.

As in its preceding release, six of RX 3 Advanced’s processing blocks—Declicker, Declipper, Decrackler, Denoiser, Hum Removal and Spectral Repair—are available both as discrete plug-ins and in the stand-alone application. Together, they attenuate or eliminate clicks, clipping distortion, crackling noises, broadband hiss, electrical hum and complex sounds such as chair squeaks in program material. The stand-alone application includes other welcome holdovers from RX 2 Advanced: the Deconstruct module (which adjusts the relative balance of a sound’s noisy and pitched components), phase rotation, cross-mixing of stereo channels, automatic azimuth realignment (useful for tape restoration), time-stretching, pitch-shifting, dither, sampling-rate conversion, parametric equalization, a spectrum analyzer, gain normalization and fades, third-party (AU and VST) plug-in hosting for Spectral Repair, and a time-stamped log.

What’s New?

Dereverb and Dialogue Denoiser plug-ins, which are configured as modules in the stand-alone application, and iZotope’s previously released Insight metering suite are now included in the bundle. When you click its Learn button during playback, Dereverb creates a reverb profile—an analysis of the wet/dry ratio in your signal across the frequency spectrum—and automatically attenuates the reverb (see Figure 1). You can subsequently edit the amount of reverb reduction independently in four frequency bands; attendant meters show the reduction amount in each band. Use the global Reduction slider to adjust the amount of reverb overall. The Tail Length control modifies the decay time for the processing. Checking the Enhance dry signal box boosts the level of direct signal.

Fig. 2: Dialogue Denoiser uses an all-new adaptive algorithm and spartan control set to rid VO tracks of noise posthaste.

Fig. 2: Dialogue Denoiser uses an all-new adaptive algorithm and spartan control set to rid VO tracks of noise posthaste.

Dialogue Denoiser has very few controls: threshold and reduction sliders and, in manual mode (which is more suited to treating music tracks), six nodes that can be dragged to independently edit the threshold in different frequency bands (see Figure 2). Dialogue Denoiser is not simply a stripped-down version of the control-laden Denoiser; the processor incorporates a completely new adaptive algorithm that automatically analyzes noise embedded in a track and sets hidden multiband thresholds.

All the plug-ins and modules sport new GUIs, and many of RX 3 Advanced’s preexisting processing blocks have been updated with improved or totally new algorithms. For example, the overhauled Declipper offers independent declipping thresholds for repairing asymmetric waveforms (that is, where clipping occurs only in the positive or negative phase of the waveform, but not in both phases). Declipper also includes a switchable peak limiter you can use to prevent digital overs after a waveform has been reconstructed. The revamped Declicker adds two new parameters to its control set: Frequency Skew pre-conditions the click detector to better recognize either low-frequency thumps or high-frequency clicks, while Click Widening adjusts the width of the region around each click that’s processed.

The stand-alone application’s Time & Pitch module can implement variable playback speed to correct pitch drift caused by wow on tape masters: In a display with pitch and time axes, you drag nodes around on a curve to raise the program’s pitch (simultaneously speeding up playback) and lower it (slowing playback) over time. The Time & Pitch module also includes a new beats per minute calculator that makes time-stretching a snap: Simply enter the current tempo and the desired tempo in bpm, and click on the Process button. The Channel Operations module can now extract the center or side-panned content from a stereo file. Spectral Repair’s spectrogram includes a new selection tool—Select Harmonics—that lets you limit which harmonics will be processed in the current selection.

RX 3 is also available in a standard version that costs less but offers a lot fewer features. Both versions of RX 3 have been optimized to use every core available in a multi-core computer, letting you work faster and get higher-quality results. Both editions can also save your work in the new RX Documents format, which archives your original audio data along with markers, all your edits, an unlimited undo history and your most recent selection and view states.

Prescriptions for Noise

I got terrific results using Dereverb to dry up a male voice-over track that had been miked from a distance in a reverberant room. I clicked the plug-in’s Learn button, and the reverb and room tone all but vanished! The processed voice-over sounded slightly choked and phase-y at first. Lowering the tail length from 3.2 seconds to 0.8 second totally nipped the artifacts in the bud. Clicking the Enhance dry signal checkbox made the track sound a tad more present and articulate, at the expense of boosting the plug-in’s output a bit. Even with the box unchecked, however, I felt like I was missing a little of the chesty timbre that had made the unprocessed voice-over sound warm and full, if a bit too resonant. The solution was to lower the reverb profile’s low-frequency control just a tad, restoring a little bottom-end room tone. I own other plug-ins that attenuate reverb. But using Dereverb, I could achieve greater reduction of short-lived resonances (as in boomy room tone) without degrading the release portion of the track’s natural envelope. I’m sold!

Treating voice-over tracks alternately with Dialogue Denoiser and Denoiser for comparison purposes, I got excellent results using each. Dialogue Denoiser got great results faster, while Denoiser was more effective at reducing noise in the upper-bass and lower-midrange bands. Dialogue Denoiser also tended to thin the voice-over’s timbre in the upper-bass band just a little—not always a bad thing when processing a track recorded with a shotgun or lapel mic.

Another voice-over track was sullied with random, midrange-y popping noises. Adjusting the Frequency Skew and Click Widening controls in the revamped Declicker, I was able to attenuate these sounds to roughly one-quarter the level I could when using RX 2 Advanced’s Declicker. Sometimes both versions of Declicker worked equally well when treating other types of clicks and pops. But for really problematic noises, the new Declicker definitely had the edge.

Using the Channel Operations module in the stand-alone RX 3 Advanced application, I could extract center-panned content from a stereo music mix. Unlike with mid-side processing, this preserved the stereo image of everything that was hard-panned—a plus for servicing karaoke singers. Adjusting the strength of the processing, I could remove almost all of the dry lead vocal, kick drum and bass without introducing phase-y artifacts.

The new GUIs are prettier to look at than the old. My only objection is with the Denoiser plug-in’s interface for its advanced settings, in which the curves for noise profile, whitening thresholds and so on are hazily displayed behind and greatly obscured by overlaid controls. (The stand-alone application’s Denoise module doesn’t suffer this hindrance.) Because of this, I found it much harder to visually gauge the effect of my whitening adjustments with respect to the noise profile.

The plug-ins all caused brief CPU spikes in DP—roughly four-fold increases over baseline levels—when playback was initiated. I’ve seen this issue with plug-ins from a couple other manufacturers.

Good Medicine

Of all the great updates included with RX 3 Advanced, the standout is Dereverb; there’s nothing else quite so effective and transparent for taming boomy room tone. Time-pressured audio-post engineers racing to accommodate ridiculous budgets will also greatly appreciate how quick and easy it is to use Dialogue Denoiser, with great results. Declicker and Declipper are more versatile and powerful than ever, and there are a lot of other beneficial refinements throughout the software suite. Simply put, anyone working in post-production, restoration or audio forensics should own RX 3 Advanced.

Mix contributing editor Michael Cooper is a recording, mix, mastering and post-production engineer and the owner of Michael Cooper Recording in Sisters, Oregon.

Product Summary

COMPANY: iZotope

PRODUCT: RX 3 Advanced


PRICE: RX 3 Advanced: $1,199; RX 3: $349; upgrades available ($TBD)

PROS: Unmatched power, versatility and ease of use in cleaning up audio. New processors and updated algorithms. Includes Insight metering suite.

CONS: Denoiser plug-in’s GUI (advanced settings) is partially obscure. Plug-ins cause large CPU spikes in DP 8.

Try This

If Dialogue Denoiser’s Auto mode isn’t reducing noise enough in a specific frequency band, switch to Manual mode. Use the Learn button to capture a noise profile. Adjust the reduction and global threshold sliders for the best tradeoff between signal-to-noise and fidelity. If noise still sounds relatively prominent in one area of the spectrum, drag a threshold node in the offending frequency band higher until the noise is attenuated to an acceptable level.

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