Download the version that matches your operating system. Follow their instructions to install the program.
Step 1: Install FFMPEG Library To Edit MP4 Files
If you want to be able to quickly drag and drop video files into Audacity you will need to download and install this library first.
You can install the library here. Follow all the steps there to install it.
Note: Make a note of where this file is installed and saved to. You will need the location in the next steps.
Then restart audacity. There is a chance it has automatically located that file. If not, you can add this manually. To do this:
Go to edit > preferences
Click on libraries.
Then click 'Locate' to browse for the file you just installed.
Click open and press okay.
If you have any troubles with these steps you can find more information on the audacity manual.
Step 2: Clean Audio And Remove Noise On Audacity
Open Audacity
Drag and drop the file you would like to edit.
If you installed the FFMPEG library (listed above) you can drag videos directly into Audacity to edit the sound.
Look for an area where there is no important sound, only the noise you want to remove. You can use the zoom tool to help you identify the blank section.
Use the selection tool to highlight that part only.
Click on effect > noise reduction
Select 'Get Noise Profile'
Click Ok
Double click anywhere on the track to select the entire length of audio
Then click on effect > noise reduction again
Play around with the settings. Press preview to hear a sample of the audio and if you're happy with the settings. Noise Reduction (dB): controls the volume of reduction applied to that noise. Pick the smallest number that will get rid of the noise. Numbers that are too high may affect quality of the rest of the audio.
Sensitivity: controls how much of the audio will be considered as noise. Goes from 0 to 24. Greater sensitivity means more noise is removed but it might also delete some wanted audio.
Frequency Smoothing (bands): This is artifacts remain in the noise-reduced audio. Smoothing may make artifacts more acceptable. But remaining audio may becomes less clear.
Select 'Reduce'
Press 'Ok'
Audacity will then render the changes. And you can export as usual. Go to file>export. Saves WAV, MP3 or your preferred format.
You can now use the audio however you want. Including adding back into your video editing software!
If the sound still contains some noise you can repeat Step 2 with another section of the track. However, modifying the track too much can leave artifacts and affect audio quality.
