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#23: Removing Noise with a Noise Filter in Audition and Audacity

By | April 27, 2007

No Noise!Welcome to the Podcasting Blog, this week we’re gonna talk about some how to topics, I’m gonna tell you how you can remove unwanted noise from a recording in two different applications and on two different platforms. This week, there wasn’t anything particularly interesting in podcast news, so I decided to just do a how to post.


If you’ve listened to many of my podcasts, you know that I’m a quality minded individual and that I like lot’s of audio tools, mostly hardware. I still think hardware is the best way to do just about anything, but, sometimes you’re in a bind and you need to use some software to get you out of that bind.

Let’s say you show up onsite to do a podcast and you’ve got your laptop and your USB recorder, or maybe even just your portable USB recorder, and you’ve got your mic and you record your podcast, and then when you get back home and start editing, you hear this fuzzy noise and you remember that when you were recording there was a fan going, and you forgot to turn it off. Or maybe your laptop fan kicked on and it’s pretty loud, so it ended up getting recorded. These types of noise problems can usually be dealt with and you can get pretty decent results.

I’m gonna give you some tips and tricks to removing noise in both Adobe Audition and Audacity. I’ll be using Audition on a PC running XP, and Audacity on a Mac G5 running Tiger.

If you’d like to see a screencast of something like this, leave me a comment and if I get enough interest in it, I’ll see what I can do.

First of all, I’ve got a file here that I want you to hear, and the file’s got some constant noise in the background, like a fan or something. I’m gonna use this same file for Audition and Audacity and we’ll see which one, if any, sounds better once we’re done.

Now, without doing a screencast, this is tough to. I can’t really show you what I’m doing, so again, if I get enough people interested in it, I’ll definitely get one setup. There are a couple of different tools you could use, depending on the nature of the noise that you’re dealing with. Some noises can be filtered out with equalizer settings, some have to be filtered out based on a pattern that they create, and that’s the approach I’m gonna use today.

First, let’s hear a sample of the file, with the noise.

Ok, now, if you’ve got some junky little PC speakers, I don’t know how much difference you’ll hear because those kinds of speakers are pretty noisy anyway, so hopefully you’re listening with some decent quality speakers. That noise was made by a fan that was on during the recording.

Fortunately, these kinds of noises are the ones that are easiest to remove because they’re doing the same thing over and over, and constantly. That creates a sound pattern, and both Audition and Audacity deal with those kinds of noises in basically the same way. You first sample the noise, so you find a section in your clip that is ONLY the noise you want to remove, then you go through and remove that sample, or anything closely matching it, from the entire file. It’s like taking a snapshot of the noise, and then going through and matching up frequencies and patterns, and anything that matches that noise, gets removed, or at least the volume of the noise gets reduced.

The thing that’s nice about this, is, it gets removed even in segments of your audio where you have legitimate audio. Like, if you’re talking, the fan noise is still there right? But both of the noise removal tools I’m gonna use will go through and match that noise pattern, and essentially remove it, even in places where there was other audio, like you talking or whatever other audio might be there.

Now, in both cases, you have to be careful, it’s not like a magic wand, you have to be careful not to use it too much, because you can take away from the audio that you do want and it’ll make your voice sound kinda robotic.

Let’s do Audition first. I’ve got my file open in Audition. Like I said, we first find a segment that contains ONLY the background noise. So look for a pause, or silence at the beginning or end of the clip, and when you’re looking at your audio, notice the fluctuation in the wave form. Play the file and follow the playhead. Listen for silence and background noise, and you should be able to see a very low signal at that point, and I’ll try to post a picture on the blog that matches up to that.

You wanna try to get a second or two of strictly background noise. Highlight that section and then right click. Select Capture Noise Reduction Profile. This uses that segment that you selected, as your pattern for removing noise from the file. So, in other words, it looks like nothing really happens cause at this point, nothing in the file was changed, it just captured the profile.

Now select your entire file, or the segment that you want to remove noise from. Sometimes you might have your whole podcast mixed down into one file and maybe just a segment in the middle is noisy, where you did an interview some place and there was some kind of background noise.

So you’ve selected the segment that you wanna remove the noise from, then go to the Effects menu, go to Noise Reduction, and then Noise Reduction again. This’ll load a dialog box that has a lot of parameters and shows you visually what the noise reduction profile looks like, from a spectral point of view. You can look at all that stuff later, for now, we’re just gonna take the default setting for everything and go ahead and preview to see what it sounds like. So with my file selected, I hit Preview and I get this:

Now, that’s not too bad, so we’ll go ahead and click OK, and then Audition will go through our file and try to match the noise reduction profile and remove it. A lot of those parameters that you saw on the screen there, can help you fine tune what’s going on, and I have had to use them on occasion, but generally, the default values work fine. Where it really helps is if the frequencies of your noise and the signal that you want to keep, are pretty similar or close to each other. Then you’ve really gotta do some tweaking to get it sounding decent.

Once Audition is done, it’s a good idea to take a look at your file and see if there are any gaps that still have a little noise, especially if it’s still audible, and what you can do is select just that segment and repeat the noise removal on just that segment and that effectively just keeps lowering the level of noise there, so do it as many times as you need to, but a lot of times, once is enough.

So now if you listen to the file, it should sound a lot cleaner:

OK, so that was Audition, now let’s hop over to the Mac and we’ll do the same thing in Audacity. By the way, Audacity is available for both the PC and the Mac, I’m just using the Mac today so that everyone knows that this show is not prejudice.

Basically, the same principal applies here. Get a profile, then apply the reduction, so our first step is, locate a gap in the audio where you can visually see ambient noise. And I’ll go ahead and play the original file again:

OK, now we select a second or two of ambient noise, then go up to Effect and then Noise removal. You have to complete step 1 first and get the noise profile. Then we go back and select the entire file and click Effect, and Noise Removal again. Audacity’s interface here is a lot simpler than with Audition, which is good on one hand, and on the other hand, it might mean our control over how the noise is removed, would be kinda limited cause we don’t have a lot of the options in Audition.

Regardless, we do have a slider for how much of the noise we want to filter out, and you might think at first, well, all of it right? But again, if we try to do too much, we can make our voice sound like a robot and generally, that’s not the effect we’re looking for, so leave it in the middle your first time around, click the Remove Noise button, and then if you have to, you can undo and go back and make some adjustments.

So after removing the noise in Audacity we get this:

If you listen hard there, you’ll hear the voice sounding kinda robotic, so I’ll undo the noise removal and go back in, this time, I’ll lower the amount of noise removal that Audacity does. That gives us this version:

That sounds a lot better. Again, you can go in there, just like with Audition and select specific segments and just keep repeating the noise removal to get it just as quiet as you please. Ideally, you want that waveform to be flat whenever nobody’s talking. Gaps between words should just be totally flat with no little squiggly lines or dots. This is one of the reasons I recommend a noise gate or downward expander, cause it eliminates the need to do this processing and saves you tons of time in the long run. If you’re podcasting on a budget though, this is the way to get that ‘studio’ sound without forking over a lot of cash.

Speaking of cash, Audacity is free and I’ll put a link in the show notes, to where you can download the latest version. Audition, on the other hand, isn’t free, but you can download a trial at Adobe’s website, and I’ll put up a link to that as well.

As you can tell, the process is very similar for both apps, and as far as quality, here is the finished Audition file:

And here is the finished Audacity file:

With both of those, I could do a lot more playing with it, and of course we could add some EQ and kinda enhance it a bit, but that’s what we get with the default noise reduction settings for both, and I think both of them sound fine. That’s it for this week, you’ve been listening to the Podcasting Blog, I’m Ken Walker. You can contact me at podcasting@seocompany.ca or just leave a comment on the blog. Thanks for listening, and I really mean this, you…are…the…best listener I have, and next week, I’m gonna do this all over again and make another podcast especially for you. Bye.

 
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Topics: Audacity, Audition, How to Podcast, Podcasting Software, Tutorial | 5 Comments »

5 Responses to “#23: Removing Noise with a Noise Filter in Audition and Audacity”

  1. Larry Says:
    January 17th, 2008 at 8:56 pm

    Noise reduction from LP vinyl records is difficult to accomplish completely with Audacity no matter how many layers of noise profiles are attempted. Is that as good as it gets?

  2. Ken Walker Says:
    March 14th, 2008 at 12:37 pm

    Sorry for the delay here, I didn’t even see this comment in the dashboard. I’ve been getting so much spam here, you wouldn’t believe it!

    I don’t use Audacity that much, and I’ve NEVER tried to use it to archive an LP. But I do know that Audition 3.0 has some great tools for LP archival. At least download the demo and give it a try. If it works, you can use it for 30 days for free.

  3. Juliet Sallette Says:
    July 4th, 2008 at 2:29 pm

    Awesome “how to blog post”. I own Audition and Audacity. Your steps really made Audition seem easy. I agree with all of your points outlined in this post. Thanks for writing a comprehensive post. I look forward to trying this next week, when I am back in the office. If you could recommend any tutorial books on Audition, I would sincerely appreciate it.

    Thanks again for such an excellent lesson.

    Juliet

  4. Ken Walker Says:
    July 24th, 2008 at 4:38 pm

    Juliet,

    Thanks for the compliments.

    I don’t know of a good Audition book, but I can definately suggest my online tutorial! I’m reworking my website right now http://www.walkerstudiopro.com so the sales page isn’t up, but you can pick it up on eBay http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120287237019

  5. nalaka Says:
    November 25th, 2009 at 10:09 pm

    I HAVE SOME AUDIOFILS TO REMOVE BACKGROUND NOICE

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