How to Remove Background Noise from Voice Recordings Pt.4

In the preceding post, we learned important concepts about the best way to train iZotope RX's spectral de-noise module before it can remove background noise.

Along with those concepts in part 3, we learned what makes the spectral de-noise module so powerful and when to use it in part 2.

Now we'll focus on creating the best possible noise profile in the de-noiser to effectively clear out background noise in your dialogue.

In addition, I'll show you a vital technique to make sure you only remove background noise while leaving your dialogue sounding clear and intelligible.

How to Create a Bad Noise Profile (What Not to Do)

In part 3, we learned that we have to teach or train RX's spectral de-noiser so it will know what to remove (background noise being our main concern).

Once you've made your selection of background noise in RX's standalone audio editor, the de-noiser will create a noise profile.

The noise profile shows the range of frequencies of the background noise using a graphical display.

Below you'll see a noise profile represented by an orange line (in the red box):

Most people wouldn't know just by looking, but this noise profile has a problem... It includes some frequencies that are not strictly background noise.

When I was training the de-noiser, I tried to include a breath between spoken phrases with the background noise (thinking it might reduce some breathing sounds along with the noise).

I was quite wrong! Instead it tried to remove frequencies from my spoken words in the recording. So this noise profile is an example of what not to do.

However, once I excluded the breath, the noise profile, of course, changed and ended up working just fine to reduce the background noise.

Take a look below:

• see my bad noise profile (with breath included)...
  
  
• versus my good one that is only made of consistent background noise...
  
  
• the red arrow on the bad noise profile points to the frequencies of my breath (these should NOT have been included): 

[ Bad Noise Profile ]

[ Good Noise Profile ]

How to Create a Good Noise Profile

Since we can't easily tell if our noise profile has a problem just by looking at the orange line of frequencies, what can we do?

How can you know for sure if your noise profile is good or bad?

This is important since it's the difference between removing just background noise or removing things that shouldn't be removed (like frequencies of your spoken words)!

Not surprisingly it involves careful listening since we're talking about audio here.

What to do is listen with familiar headphones or speakers through the incredibly useful "Output noise only" feature on the spectral de-noise module.

This feature is so vital because listening through it is how you find out if the noise you've selected is the right thing or the wrong thing.

When you listen through the "Output noise only" feature, you'll hear exactly what the de-noiser is going to remove from your dialogue recording (using "Preview").

If your hear just background noise - you're golden! That's what you want.

But if you hear something other than background noise as you're listening through it, you know there's a problem...

For instance, this is how I found out that the noise profile from above (the bad one) and below - actually had a problem.

Not from looking at the frequencies, but from LISTENING to them through the "Output noise only" super feature:

• I selected the "Output noise only" box and hit "Preview"...
  
  
• I listened through my entire dialogue recording using the flawed noise profile above...
  
  
• I could hear background noise coming in and going out - GOOD...
  
  
• but during the spoken phrases, I heard frequencies of my spoken words - BAD...
  
  
• I knew there was a problem!

How to Fix a Noise Profile With Problems

So what do you do in this situation? How do you go about getting a good noise profile?

Unfortunately you need to start over, but it won't take long:

• just go back to an area with background noise in your voice recording...
  
  
• and redo your selection for the noise profile...
  
  
• try to exclude any sound that isn't ongoing, consistent background noise...
  
  
• now, listen and look at your selection in the RX audio display...
  
  
• make sure you can hear that it's JUST background noise...
  
  
• then select "Learn" and your new and improved noise profile will appear in the spectral de-noiser!

In this way, you've created the best noise profile using your ears as the guide and your eyes helped along the way.

You may find out that you need to use a shorter selection to get just background noise (and exclude the other sounds).

Or, you may have to find a different area entirely to get at least 0.5 seconds of just background noise - no breaths, mouth sounds, random clicks etc.

See below where I had to go back and select JUST background noise, while excluding a mouth noise and my breath (red boxes):

Summary

The noise profile in RX's spectral de-noise module is created from your selection of noise in your dialogue recording.

However, you can't easily tell by looking if it will work correctly to remove just background noise.

Remember, you need to listen to what the noise profile is going to remove using the "Output noise only" feature.

This is a fail-safe method to make sure your noise profile is set up correctly. 

Finally, to create the best noise profile possible, listen and look at your selection of noise in RX to make sure you can hear and see that it's only background noise.

What other suggestions do you have for getting a good noise profile in your dialogue recordings?

Would love to hear your thoughts in a comment below!

Cheers, Bryan
Your Dialogue Editing Mentor