What is Audacity Noise Gate?
A Noise Gate is an audio processor that controls the intensity of some sound signals in your recording. It does this based on a threshold set. Just like a literal gate, it acts as a barrier that lets in some sounds. These sounds usually are louder than the signal threshold set. Concurrently, it also lessens the sound signal that is below the level of the threshold set. A noise gate can be an electronic device that you connect to your recording equipment, a standalone software or even a software add-on/plugin. In Audacity, it is a software add-on.
Installing Noise Gate Plugin on Audacity
Launch Audacity. Once the software is running, import the audio file that you want to edit.
Click on Effects from the menu tab. Under the options in the dropdown that pops up, you should see a Noise Gate option.
If this option is not available, head over to Audacity Plug-in Download Site and download the plugin. This will be a NY file.
After downloading it, copy the file to the Audacity folder which is under the program files folder on your computer. The specific folder to paste in is the Plug-Ins folder.
C:\Program Files\Audacity\Plug-Ins
After pasting the file head over back to Audacity and click on the effects option on the menu tab. From the dropdown click on Add/ Remove plug-ins option.
Clicking on this option will open a new dialogue box.
The names of the plug-ins are in alphabetical order therefore getting them should be easier. As seen in my screenshot the state of my Noisegate is new as I have just added it in my plugin folder just a few seconds ago.
If you want quick access to recently downloaded plugins you can filter the plugins using the options on the upper part of the dialogue box. In this case, I will select the New option then the drop box will just show the recently downloaded plugins.
Next click on the Enable button which will now make the Noisegate option available under the dropdown option.
Lastly, click OK to apply these changes.
How to use Audacity Noise Gate
Import the audio file. The first thing that you need to get is the noise floor level. This is the loudness of the noise and unwanted signals in your recording. Identify a section of your file with no speech going on and zoom in to that part.
The noise gate feature works by eliminating sound signals like the hissing sounds in the background. It does this by working with a threshold set. The sounds that aren’t louder than this threshold are muted and sounds louder are not affected.
Here is a snapshot of my file.
Following my file as a guide play a part of your waveform that has no speech. The parts with faded orange highlights are the sections that I intend to clean using the Noise Gate Plugin. These parts might consist of various noises. Might be heavy breathing, fan noises, or traffic noises. Ideally, just find one gap and use this for the steps that I have addressed next. Press play on that part.
As the audio is playing pay attention to the playback level meter bar at the top as highlighted in the previous image.
In this instance, you are trying to establish how high the background noise or noise floor is. So note down the extreme right level that the sound bars get to. This is the level that the loudest section of the selected gap got to.
Whenever you pause there is a blue line that appears rather than the green bars that appear once the audio starts playing. This blue line is the highest level of the loudness of your audio signal based on the recent seconds that you have just played. Remember to only play a part that does not have any speech to get the loudest level of your noise, not speech.
With that figure, your threshold should be set at a level higher than the number obtained. In my case, I will set it at around -42 which is slightly higher than my noise floor level which is at around -45. Setting it at -42 lessens or eliminates any sound signals that are below that level. Note that the further we move to the right of the bar level the louder the sound is and as we move further left the lower our signal level gets. Therefore, your noise level should always be falling towards the left side of the playback sound back.
The next step is applying the noise gate effect. I prefer having a look at the spectral view of my waveform first. This view helps give a visual view of how much noise is present in the unedited audio file. To access this view click on the arrow on the file information panel on the left of the waveform. Under the dropdown option list that pops up click on Spectrogram.
My spectrogram view looks like this.
Once I am done with applying the Noise Gate effect and recheck the file under a spectral view the highlighted parts should have fewer bristles/strands or none. The darker regions should not have bits of the other colors. Revert back to the waveform view. Click on the arrow on the file information panel on the left of the audio wave. Under the dropdown option list that pops up click on the Waveform option.
Since you now have a figure which you can reference in setting the threshold you can now commence with removing the noise.
Double click on the waveform to select all, or use keyboard shortcuts Ctrl + A. After you select your file click on the Effects option followed by a click on the Noise Gate option. If you do not select your file the Noise Gate option will be greyed out and you will not be able to select it.
After you click on this a new dialogue box will open. This is the Noise Gate dialogue box.
Remember the noise floor level figure that you recorded off of the sound bar level. In the gate threshold slot under this dialogue box, key in a slightly higher value than what you had gotten. Under this, I will key in -45 dB following my example above. This option is for setting a limit.
Next, you will look at to what level you want to reduce this noise level. This is the level reduction option. This option is for setting a quantity. This quantity is the level of the signal being removed. So far you have established that you want to remove sounds below -45 and now you will key in how much in dB you want to remove the unwanted signals. The further you drag your slider to the left the clearer audio you will get.
I did press OK with my slider set at 100. Here is a spectral image of my audio wave with this change applied.
Notice the gaps have this plain black color unlike the previous spectral image of the file without this noise reduction effect applied to it. The noise that was present has completely been removed.
A point to note is that this plugin is not present to kill off the noise completely at all times. Sometimes trying to completely remove the existing background noise might affect the file negatively. You have to always drag the slider and preview the file repeatedly to gauge whether the effect is not having a negative effect on how your file will sound.
If you are content with how the file sounds click on OK to apply these changes. This might take a bit longer depending on your file size.
Change your view as well to check how your file looks in comparison to it prior to having the noise reduced or removed.
Conclusion
This plugin is beneficial in terms of removing noises in between words especially during long pauses when speaking. Noises can be electrical humming in the background, a hissing sound, or noises from people within the studio space. For a podcast recording whose duration passed the one-hour mark, it would be tiresome & inconvenient trying to remove the noise from the pauses manually. The Noise Gate plugin is an efficient and quicker route.
