BY DOUG YOUNG

Being able to record at home has great advantages for musicians, but getting professional results can be challenging. Noise is often one of the key differences between a homemade product and recordings made in professional studios. Whether it’s the sound of air conditioning, traffic outside, or the neighbor’s dog barking, noises have a way of creeping into recordings of even the best studios, but home studio settings are especially susceptible. In addition, recording an acoustic guitar presents some unique issues, from string squeaks and pick clicks to a noisy chair, or even your foot tapping. In person, these sounds are part of the musical experience and are easily ignored, but they often get magnified to the point of distraction by sensitive microphones during recording. One option for dealing with noise is noise reduction software.

iZotope RX has been a highly regarded noise-reduction tool for both home and professional studios since it appeared over a decade ago. With the release of version 8, iZotope has added some new features for guitarists to their already deep and comprehensive tool set. In this review, I’ll focus on the features, both new and old, that are likely to be of most interest to acoustic guitarists.

RX comes in three versions, Elements ($99), Standard ($299), and Advanced ($999), and consists of both standalone software and a set of VST, AU, and AAX plug-ins. The basic program is similar across all three versions, but the higher-priced versions contain more individual tools and plug-ins. You can perform some basic operations with the Elements version, while most of the features guitarists should find useful appear in the Standard version.

Noise-Reduction Plug-ins

If your needs are fairly simple, most of RX’s noise-removal tools are available as plug-ins that can be applied non-destructively to a track right in your recording software, or DAW. Most offer a few basic controls that allow you to fine-tune the noise reduction.

Of particular interest to guitarists, RX 8 contains a new plug-in named Guitar De-noise that combines tools for removing squeaks, pick sounds, and hum from amplifiers or guitar pickups into a single convenient interface.  The plug-in offers a “solo” feature that lets you audition only the sounds you’ll be removing, which is useful for fine tuning the controls and making sure that you aren’t over-processing and removing musical sounds as well. The controls for squeaks and clicks are easy to operate—just adjust the sensitivity control to determine when the process kicks in, and then choose how much to reduce the objectionable sounds.

Fig. 1. The Guitar De-noise plug-in running inside Logic

The hum reduction works a bit differently, as it needs to “learn” what the hum sounds like, so you need a sample of the sound you want to remove, usually a few seconds of audio from before you start playing.

There are other plug-ins that can be effective on acoustic guitar, including the De-click and De-crackle plug-ins. There is some overlap between these plug-ins and the newer guitar plug-in, but each seem to detect noises a bit differently and offer somewhat different controls, so it’s worth trying them if you are trying to eliminate troublesome noises. For vocalists, there are also Breath Control, Mouth De-click, De-ess, and De-plosive plug-ins that can help clean up noises that often occur in vocal tracks.

Fig. 2. De-click plug-in

In addition, there are plug-ins for removing broadband noise, the type of noise you might get from air-conditioning or the rumble of traffic, or even the self-noise of some mics and preamps. These plug-ins work similarly to the Guitar De-noise amp process—you start by sampling a bit of the noise you want to remove before applying the process to the entire track.


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Fig. 3. The Spectral De-noise plug-in.

All of these plug-ins work non-destructively and in real time, so you can apply them without fear of permanently altering your tracks. Of course, you can tweak the effect to get the best results, as well as turn them on and off to compare with and without the noise reduction.

One thing to be aware of when using the plug-ins is that some introduce latency as they buffer the audio for processing. The Guitar De-noise plug-in appears to work with no noticeable latency, but the delay in some of the other plug-ins can be significant. Most DAWs handle this latency automatically to keep multiple tracks in sync, but you may notice that the playback cursor and the sound are no longer synchronized.

RX Standalone Program

While the plug-ins offer easy processing for many situations, the standalone program goes much deeper and allows finer control, aided by impressive visualizations, allowing you to clean up your audio in great detail. The workflow is different, since the standalone program works destructively. I typically configure RX as an external editor within my recording software (Logic). This allows me to launch RX from Logic to edit a track, make destructive changes, and save, which reloads the track into Logic. Because the changes are destructive, it’s a good idea to work on a copy—I usually create a “bounce” of a track in Logic and work on the copy, leaving the original intact, so I can always return to the original file if I decide I’ve gone too far.

One major benefit of using the standalone program is the availability of a spectral view. This window overlays your audio waveform with a graphic that shows time on the X axis, frequency on the Y axis, and intensity as a color.

Fig. 4. RX 8 standalone program, spectral view of a stereo track.

The spectral view allows you to literally see various events, such as squeaks or even background noise. There are several different color schemes, which may help bring out different aspects of noise. I prefer the “multi-color” view most of the time, since it seems to make squeaks and clicks most obvious. You can also adjust between all waveform and all spectrum, or anywhere in between.

While it takes a bit of practice to learn to correlate the spectral information with what you hear, the spectral view makes many problems easy to see visually. For example, Fig. 5 shows a track similar to the one in Fig. 4, but in this case, I had a loud fan running while I was recording. It’s easy to see the dramatic increase in background noise on the recording.

Fig. 5. The Spectral view makes broadband noise obvious.

Another important benefit of the standalone program is that you can select any part of the spectrum—both a time range and a frequency range­—and apply operations to only that part of the recording. So, for example, rather than just letting the Guitar De-noise plug-in operate over the entire track, you can select specific trouble spots to process while leaving the rest of the track untouched.

The standalone program also provides some more advanced tools that are not available as plug-ins. While the Guitar De-noise plug-in works well on many typical guitar noises, some sounds are more challenging. The Spectral Repair tool offers far more options, including multiple algorithms for removing noises to help deal with problem cases, and allows you to select an individual squeak or other noise to process. For those familiar with Photoshop or other graphics editors, Spectral Repair operates much like the “Healing Brush,” analyzing the surrounding material and nearly magically replacing the selected area. You can save and compare multiple settings while working on a particular spot so you can choose which options sound best. RX supports keyboard shortcuts, so you can perform common operations like squeak repair without bringing up a dialog box. For even faster workflow, some operations can be used in “instant process” mode. If activated, the processing happens automatically to anything you select on the screen.


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Fig. 6. Using Spectral Repair along with spot selection to remove a single squeak.

While RX is heavily focused on noise reduction, it also offers a useful collection of more general audio operations such as volume adjustments, normalization, EQ, phase correction, sample rate conversion, and more. RX can also repair clipped audio, by detecting and reconstructing peaks that have exceeded the limits of digital audio. The EQ Match function (Advanced version only) allows you to match your frequency response to that of a reference track. A De-bleed operation allows you to remove bleed between tracks—which might occur when miking multiple sources in the same room. It could also be used to remove bleed from a click track picked up from headphones.

A Great Solution for Home Recording

RX has become a nearly indispensable tool for any recording studio, and it is arguably even more valuable to those of us who record at home in less than perfect environments. While noises are always best avoided if possible, things happen, and RX can help rescue a perfect take that was marred by a car horn or a door slamming in another room. RX’s ability to remove most noises with virtually no trace often seems like magic.

Even if you are lucky enough to be able to record in quiet environments where outside noises don’t creep in, RX works remarkably well for smoothing the rough edges from an acoustic guitar recording, cleaning up those inevitable extraneous squeaks, clicks and buzzes. The new Guitar De-noise feature is a welcome addition to the program, as it simplifies the most common tasks. But as you spend more time with the program, you may find yourself reaching for some of the more sophisticated tools as well.

With any noise-reduction process, it is possible to overdo it and affect the quality of the recording. But RX is surprisingly transparent and when its tools are used judiciously, it can turn an otherwise good recording with a few noise issues into a polished, professional-sounding product.

From $99

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