With the right guidance, iZotope's RX can remove problem sounds that would otherwise ruin a mix.
Last time in Part 1, we introduced some of the features of iZotope’s RX Audio Editor and considered how to use it to perform fairly simple noise‑reduction tasks such as removing buzz, hum or hiss from a recording. This sort of ‘system noise’ is usually fairly constant, and especially if you have a section of recording that contains only noise, can be targeted pretty effectively using the presets in RX modules such as De‑hiss. In Part 2, we’re going to look at a different and more challenging application for RX‑type spectral processing: removing unwanted sounds that have been captured along with the wanted audio at source.
My first example comes from a recording where the double bassist had played a lovely part. It had been recorded nicely, in a nice room using nice microphones. Sadly, the bassist had a habit of tapping the edge of the neck, and his timing was so good it completely covered the snare! In this case I was working on the track as a mix engineer and the client hadn’t noticed it because they were listening with what I call ‘attached ears’. It’s always hard to be objective on your own music.
Screen 1 (above) shows the bass part loaded into RX. As usual, you can see the horizontal lines which represent the notes. There’s some ambient noise that we don’t want — in this case, a little room noise and some spill from the headphones, plus some other incidental noises from the performer — but it’s nothing too severe. The problem noises are easily identified as the tall vertical spikes. When the player slaps the neck, it generates a sharp transient which contains energy throughout the frequency range, from 50Hz right up to 20kHz. The only real option here is to manually select these noises and try to remove or subdue them, being careful to not affect the tail on the notes. There are a few ways of approaching this, and my eventual solution was arrived at only after working through a few...