By | April 27, 2007
Welcome to the Podcasting Blog, this week weâ€™re gonna talk about some how to topics, Iâ€™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 wasnâ€™t anything particularly interesting in podcast news, so I decided to just do a how to post.
If youâ€™ve listened to many of my podcasts, you know that Iâ€™m a quality minded individual and that I like lotâ€™s of audio tools, mostly hardware. I still think hardware is the best way to do just about anything, but, sometimes youâ€™re in a bind and you need to use some software to get you out of that bind.
Letâ€™s say you show up onsite to do a podcast and youâ€™ve got your laptop and your USB recorder, or maybe even just your portable USB recorder, and youâ€™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 itâ€™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.
Iâ€™m gonna give you some tips and tricks to removing noise in both Adobe Audition and Audacity. Iâ€™ll be using Audition on a PC running XP, and Audacity on a Mac G5 running Tiger.
If youâ€™d like to see a screencast of something like this, leave me a comment and if I get enough interest in it, Iâ€™ll see what I can do.
First of all, Iâ€™ve got a file here that I want you to hear, and the fileâ€™s got some constant noise in the background, like a fan or something. Iâ€™m gonna use this same file for Audition and Audacity and weâ€™ll see which one, if any, sounds better once weâ€™re done.
Now, without doing a screencast, this is tough to. I canâ€™t really show you what Iâ€™m doing, so again, if I get enough people interested in it, Iâ€™ll definitely get one setup. There are a couple of different tools you could use, depending on the nature of the noise that youâ€™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 thatâ€™s the approach Iâ€™m gonna use today.
First, letâ€™s hear a sample of the file, with the noise.
Ok, now, if youâ€™ve got some junky little PC speakers, I donâ€™t know how much difference youâ€™ll hear because those kinds of speakers are pretty noisy anyway, so hopefully youâ€™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 theyâ€™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. Itâ€™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 thatâ€™s nice about this, is, it gets removed even in segments of your audio where you have legitimate audio. Like, if youâ€™re talking, the fan noise is still there right? But both of the noise removal tools Iâ€™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, itâ€™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 itâ€™ll make your voice sound kinda robotic.
Letâ€™s do Audition first. Iâ€™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 youâ€™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 Iâ€™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 youâ€™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. Thisâ€™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, weâ€™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, thatâ€™s not too bad, so weâ€™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 whatâ€™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 youâ€™ve really gotta do some tweaking to get it sounding decent.
Once Audition is done, itâ€™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 itâ€™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 letâ€™s hop over to the Mac and weâ€™ll do the same thing in Audacity. By the way, Audacity is available for both the PC and the Mac, Iâ€™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 Iâ€™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. Audacityâ€™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 donâ€™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, thatâ€™s not the effect weâ€™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, youâ€™ll hear the voice sounding kinda robotic, so Iâ€™ll undo the noise removal and go back in, this time, Iâ€™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 nobodyâ€™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 youâ€™re podcasting on a budget though, this is the way to get that â€˜studioâ€™ sound without forking over a lot of cash.
Speaking of cash, Audacity is free and Iâ€™ll put a link in the show notes, to where you can download the latest version. Audition, on the other hand, isnâ€™t free, but you can download a trial at Adobeâ€™s website, and Iâ€™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 thatâ€™s what we get with the default noise reduction settings for both, and I think both of them sound fine. Thatâ€™s it for this week, youâ€™ve been listening to the Podcasting Blog, Iâ€™m Ken Walker. You can contact me at firstname.lastname@example.org or just leave a comment on the blog. Thanks for listening, and I really mean this, youâ€¦areâ€¦theâ€¦best listener I have, and next week, Iâ€™m gonna do this all over again and make another podcast especially for you. Bye.