iZotope RX 2 Advanced review: pt. 2/3

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Putting it to the test!
I wanted to try and go through each kind of sonic artefact and see just how well RX stood up to the challenges using the different tools available.

In situations where you are presented with hum, (which has only a few harmonics), RX’s Hum Removal module is apparently the tool for the job. By allowing you to set the primary frequency of the hum and control suppression of up to 7 harmonics above the low frequency Hum Removal. RX’s Denoiser is also a logical choice to use for removing hum, you may want to try both to see which gives you the best results.

In situations like this example, where the hum’s harmonics extend into high frequencies, try using the Denoiser module in RX. Denoiser can work with this type of noise as well and features a Tonal Noise suppression control, which can often control high frequency buzz more effectively than Hum Removal.

Hiss and other Broadband Noise:
RX’s Denoiser module is stated as the go‐to tool for removing noises of this type. I have a recording taken off an old cassette tape that I have captured via my soundcard straight into my DAW. At the beginning of the piece you can hear the noise clearly and by looking at the Spectrogram you can also see it.

The Denoiser tool provides us with the ability to see the INPUT, OUTPUT (denoised), NOISE PROFILE (shows the noise threshold), and RESIDUAL NOISE (shows the desired noise floor after denoising, this can be controlled by Reduction and Residual whitening controls in advanced mode only) levels via a dynamic frequency/dB chart. This allows me to work straight away by crafting how and where the noise reduction will occur across the frequency chart. I can therefore be specific to certain frequencies or choose to apply the reduction to all frequencies. This is indeed very very useful.

Every single noise repair tool I have used before only offered me the ability to apply a blanket reduction across all frequencies at the same level. Make sure that the “A (realtime)” algorithm is selected if you want to preview the result in realtime—the other modes may yield higher quality but they take much longer to process. This is a tremendously useful feature in Denoiser because it allows you to hear instantly how effectively noises are being removed and how much, if any, program content is being impacted by your settings. Once I had worked with the settings to adjust the overall threshold and the amount of reduction I applied the tool to the audio file which took 9 minutes to render. Just make sure you are happy with the result before hitting ‘process’! Basically I found working with the threshold until you could hear the watery artefacts worked well and then easing it away and then reducing the amount so that it didn’t sound intrusive to the audio.

Have a look at the audio now it has been processed.

And the result:

Good huh? I think so – so good in fact that the audio is pretty much free of hiss!

RX has a dedicated Declipper tool which can in many cases rebuild the squared‐off peaks caused by clipping and restore the recording to a natural sounding state. They say that not every kind of distortion can be removed and personally I found this not to work too well at all. In fact I had better results using the Declick/Decrackle tool instead which is meant to focus on the removal of clicks and pops. I tested this on a vocal which had been recorded using a high end condenser mic and the vocalist had decided to sing a lot louder and not move away from the mic itself which made the preamp to become overloaded at times. OK so in this case I could have re-recorded the vocal but I was happy with the vibe. Unlike many of the other tools, it was a pity that the Declipper did not eater the output only of the sound which was being affected.

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iZotope RX 2 Advanced review: pt.3/3

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