Woody's SOUND ADVICE

Ho hum – audio restoration …another audio tool to spend money on that isn’t a bright, shiny, fun toy.  But if you have some severely compromised audio tracks you will be looking for a solution.  iZotope’s RX is an excellent one.

I was recently mixing a broadcast project with some serious audio issues.  These production issues are always a head scratcher.  There was an interview of two subjects sitting side by side.  One was distorted and sounded like they were in a wind tunnel, the other sounded clean.  The scene cut between a two-shot and individual close-up shots of the talent.  None of the audio cuts even remotely matched even though they were sitting next to each other!  Blasts of clean audio cut to distorted audio cut to the wind tunnel.  I was asked to “clean it up a bit.”  Easier said than done!

I started checking through my box of tools to tackle the problem and several fit the bill.  I won’t name the other programs but one of them wouldn’t authorize although I’ve owned it for over a year.  Their website was useless for this and they wanted me to pay for support.  I can’t quite figure out how these companies have the gall to charge me to figure out why the program I bought and paid for won’t load.  But … that is a rant for another day!  Let’s just say that I have had these problems with this company before and now I’ve finally “washed” my hands of their noise reduction product and them.

RX has five separate modes for tackling tough audio problems.  These are not unique to iZotope since these are the types of tools generally found in similar sorts of programs.  However the iZotope implementation has a wide variety of parameters to adjust how the source file is being effected.  These are very powerful tools with a real range of abilities.  A brief description of each is –

Declipper – a repair algorithm that finds and repairs analog or digital clipping or overmodulation.

Declicker – a repair algorithm that finds and repairs clicks and crackles from recordings.

Hum removal – a repair algorithm that finds and repairs hum and buzz.

Denoiser – a repair algorithm that finds and repairs pesky broadband noise problems.

Spectral Repair – a repair algorithm that finds and repairs random noise within an audio file.  Pretty cool feature.

Unfortunately for me I had to use each of these tools on this interview.  And they rocked it.  The hum removal is an adjustable comb filter that takes out the main frequency hum and it’s associated harmonics.  (Comb filters are filters of many small bands that graphically look like a – comb.)  This has many parameters to adjust and worked like a charm right off the bat.  Next I had several bits of horribly distorted audio.  Using the declipper tool I was able to make things sound less awful.  Not great but definitely better.  I can’t blame RX on this one, fingers pointed squarely at the sound recordist.  Each of these tools have a box where you can audition only the portion of the audio which is being filtered, adjusted, manipulated or repaired.  I wanted to check that the decipper was actually addressing the issue and when I listed to only the audio to be repaired lo and behold all I heard was distortion.  So although it didn’t “fix” the file it took some of the edge off.

Next up was the A/C – wind tunnel problem.  This was a real treat.  I used the denoiser tool to clean these audio bites up.  As is the case with other similar tools on the market you find a “clean” portion of the noise (huh??) and “train” the filter what to remove.  Once it’s trained you process the file.  There are a couple of denoiser algorithms and I found in this case the “offline” ones worked best.  I am working in ProTools and you can run the RX tools as inserts to process the track in real time.  Since these had so many different noise problems I hard-processed the files and rewrote them.  These higher powered algorithms are not available as a real time insert and instead process offline – or in other words rewrite the file with the processing.  The difference was stunning.  All of a sudden I was able to match the audio files to sound like they were actually – recorded well!

This is a highly effective tool for audio post.  I have not used it specifically on music sources but if you check their website out you’ll see several powerful demonstrations specific to music.  I have used all of the major software vendors for noise reduction as well as the high-end hardware units.  Now this can’t compete with the dedicated hardware solutions but it’s not thousands of dollars either.  If you find yourself up against difficult audio restoration in your projects I would highly recommend RX as a solution.  These tools can make you a hero to the producers who want a “little clean up” on their horrible audio recordings!