You’ve pressed stop and saved your project. Perhaps you’ve got some more tracks to add, or you’re ready to start editing. Either way, there’s something you need to do first.
It happens every time, regardless of the microphone quality. There, in the background, as you review the audio, you hear it: a hiss. Perhaps it’s a regular tapping, a bird squawking, or just a general ambient noise.
You really need to get rid of it, otherwise your audio project will lack the professionalism you’re striving for. Now, it’s really simple to remove that ambient noise in Audacity; read on to find out how.
You’re Using Audacity, Right?
If you’re not already using Audacity — it’s available from http://audacity.sourceforge.net/ — then you can still use it to remove ambient noise whether the audio was recorded with the software or not.
Never heard of Audacity? Where have you been?! While there are several strong alternatives, Audacity pretty much covers all of the features and options that you’ll need to use. This software is capable of helping you make great sound effects, just as easily as it can record a podcast.
Audacity newbies should check our guide to recording with the open source audio editor. In the meantime, you can open your audio in Audacity by opening the File > Import menu and browsing for the file in question.
Why Get Rid of the Ambient Background Audio?
In some cases, you might be happy to keep the background audio. You might not even have realized that the ambient noise was a problem. So: when should you get rid of it?
There’s a simple rule of thumb here. If the ambient noise detracts from the music or talking that is the main feature of the recording, then it needs to go. At the very least, it needs to be reduced.
So, podcasts, songs, video game effects and dramatic recordings — anything that needs to have a polished production — should have the ambient noise removed. Everything else, such as personal notes, or a recorded interview, should be fine with the ambient background audio left intact.
Find Some Background Noise
To filter out the ambient background noise, you’ll need to find a section of audio where it can be heard alone, isolated. This might involve splitting a stereo track to two mono tracks (via the down-arrow on the Track Control Panel, and selecting Split Stereo Track).
Once you’ve found the audio — which Audacity will use as an example — you should select it with the mouse. Make sure the Selection tool is selected, then left-click and drag the section of background, ambient audio.
This audio selection will be used by the Noise Reduction feature in Audacity to find similar background ambient, and remove it from the track(s). Not only is it pretty clever, the end results are almost always superb.
Use Noise Reduction in Audacity
With the audio selected (it will be highlighted in blue), open the Effects > Noise Reduction feature. You’ll see a dialogue box with a two-step tool. First, head to Step 1 and click the Get Noise Profile button. You have your profile selected already, so proceed to click this.
At this point, the Noise Reduction box will close. Don’t let this confuse you. Instead, select the portion of audio that you wish to remove the ambient sound from. If this is an entire track, simply left-click the track header to select it all.
With this selected, return to Effects > Noise Reduction, and look at Step 2. In most cases, the default Noise Reduction, Sensitivity and Frequency Smoothing settings will work, so you can go ahead and click OK to accept these. It may take a while for the noise reduction to be applied; this will depend on the track duration.
Of course, you’re free to alter the Noise Reduction, Sensitivity and Frequency Smoothing settings, and if you have the time to play with them (this can be tricky with longer tracks, due to the processing time), it can be worth your while to achieve a superior result.
Once this is done, preview the results. If you’re happy with them, hit File > Save to retain the change. You might then use these five tips to make your audio sound even better, before you export your project as an MP3 file.
How Did It Work for You?
In the majority of cases, you should be able to dispose of any background hiss or other ambient noise. I’ve successfully removed noises as irritating as typing and even a pair tweeting birds. Audacity is superb for this sort of audio fixing; indeed, this is just one of many abilities the software has. You might even use it to create sound effects — it’s just so versatile.
Have you removed ambient noise from your audio with Audacity? Run into any problems? Perhaps you found a superior tool? Tell us in the comments.
Originally written by Angela Randall on 5th May 2011