JG McQuarrie
Aug 24th, 2022It can happen to the best of us. You can record something you think will sound pristine and clear, only to discover there’s the background noise you weren’t expecting.
Maybe there’s a fan in the room that was accidentally picked up. Or perhaps there are constant background sounds, such as equipment hum or hiss that you didn’t detect at the time but which you can now hear on your audio recording when you listen back.
Whatever the cause, it’s a problem.
Fortunately, Audacity can help with that. Audacity has a range of great tools for improving the quality of any audio. In this article, we are going to talk about how to remove background noise in Audacity with the Noise Reduction tool.
However, before we start with the noise reduction tool, there are a couple of good-practice suggestions it is worth covering to ensure you can get the very best results from Audacity.
One of the simplest but most important things to do is record audio with just a little “silence” before speaking. A few seconds is normally enough for this.
The reason will be covered in a bit more depth below. But basically, this will give a region that allows Audacity to analyze only the noise that you want to eliminate. You can do this either at the start or end of your track, it doesn’t matter which, as long as the noise is captured. This will help Audacity build a “noise profile”.
You should do this for every podcast host that is being recorded, especially if the other hosts are being recorded in different locations. Every location will have its own audio characteristics (its own “room tone”) and its own set of background noises to contend with.
By recording a few seconds for a noise sample with each host, Audacity can analyze each individually and remove the identified noise. That way you will get the best results from the noise removal.
It’s also worth mentioning that, when you want to remove background noise, prevention is better than the cure.
It’s worth taking a little time to check your equipment and connections to ensure there is as little stray hum as possible. Try to position anything which might be picked up as background noise as far away from the microphone as possible.
These may seem like simple points, but they can make a world of difference to the final recorded audio.
To remove background noise, launch Audacity and load your audio file. Go to the File menu, choose Open, and browse your computer for the audio file.
Once you have loaded your audio, select a few seconds of silence by left-clicking your mouse and dragging it. Ideally, you will have recorded some at the start or end of your recording.
These few moments will have captured the ambient sound in the room for the noise profile. Selecting in this way will allow Audacity to differentiate between the ambient sound and the recorded voice.
Go to the Effects menu, then choose Noise Reduction.
This will bring up the Noise Reduction dialogue box.
Click on the Get Noise Profile button in the Step 1 box.
The Noise Profile dialogue box will then close, and Audacity will create a noise profile from the part of the track you selected.
The noise profile it has generated will be used so it only removes the ambient noise from your recording.
You can now select either your entire recording or part of the track that you want to apply the noise reduction to.
Once you have selected this, re-open the Noise Reduction dialogue box by going to the Effects Menu, then choosing Noise Reduction.
In the Step 2 box, you will see three options with sliders and two Noise options.
Noise Reduction changes the amount of volume reduction which is applied to the recording. This will need to be adjusted for each recording. The default setting is six, which is often a good middle ground. Adjust and determine as required for the recording so it removes only the noise.
Sensitivity changes how much of the recording is seen as noise and how much is the original track. A value of zero means that it is off, and the maximum it can be set to be 24. The aim here is to have the value as low as possible to effectively remove noise but without removing any of the audio signals you want to be preserved (i.e. the recorded voice).
Too much sensitivity with the higher settings might reduce the amount of background noise but leave audio artifacts such as distortion on the original track. Too little might not have enough of an impact.
Frequency Smoothing (bands) will spread the noise reduction into neighboring bands as specified by the numerical value. This can help deal with any noise artifacts which may have been generated by the Sensitivity settings.
Sometimes no frequency smoothing is required at all — especially if you have a very strong original signal and only a very little background noise that needs to be eliminated — in which case the setting can be left at zero, which is off.
Noise: Reduce can be selected to remove the noise from the audio you have selected. This is usually the option that is required and is the default setting.
Noise: Residue can be selected to hear what will be filtered out, so you can ascertain what will be eliminated. If you choose this option and you can still hear parts of the audio you want to preserve along with the background noise that needs to be eliminated, you probably need to adjust the Noise Reduction or Sensitivity settings to get a better balance.
Once you have made your selections, click the Preview button to hear what the changes will do to your recording.
If you are happy with the results, click OK to apply the changes, then save your sound file.
As with all tools of this nature in Audacity, there are many variables that have the potential to affect results.
It will take a little playing around with settings to ensure you get the best results from Audacity. Different environments and recording sessions will require different levels of background noise removal.
However, if you are not getting the results you want from Audacity, there are a few points to keep in mind.
If you have a lot of noise in the foreground — a crowd making a lot of noise or loud vehicles driving past if you are outside — then when you apply noise reduction it will have limited or no effect.
The more you use the tool, the more adept you will become and judging the correct settings and getting the noise reduction effect to an acceptable level.
But it is worth remembering there is no “correct” setting. Every track is different and every track will require different adjustments to be made.
It’s a balancing act between how much background noise you lose and how much you want to keep without affecting the original recording.
Removing background noise in Audacity is not simply a case of pressing one button and having all the ambient sound on your audio files disappear. If you want to remove background noise, it takes practice.
However, although it takes a little bit of getting used to, the noise reduction tool is nevertheless both powerful and fairly easy to use. Just a few tries with it can result in noticeably improved audio, especially with the spoken word. Even the default settings will make a difference to your audio files.
It’s easy to assume that, because Audacity is free software, somehow its tools won’t measure up against commercial rivals, but with the Noise Reduction tool we can see (or rather hear) that this simply isn’t the case. The Noise Reduction tool makes a case for the software itself, and with just a little practice you can have quality, professional-sounding audio in no time at all.
