If you do not already have it you will need to download VLC Media Player from videoLAN.org. VLC is a completely free media player that can play almost any type of file, is great for converting files, and can even be used as a screen recorder. If you consume a lot of media online then chances are you already have VLC. You could also use is Free Video to MP3 Converter by DVDVideoSoft.

If you choose to use VLC, open it up and select Covert/Save under Media. Select your video in the Open Media window that pops up. After you click Covert/Save you will be able to choose your format, in this case MP3, under Save as type.

You can download Audacity for free at Audacityteam.org.

Once you have Audacity use it to open your MP3. Then, find a section of your audio that is silent aside from your background noise and highlight it by clicking and dragging. The idea is to point out to the program exactly what sound is a problem for you so it knows what to remove. If you have trouble finding a significant stretch of background noise that does not also include dialogue remember to record a pause before or after the content of your video next time you film.

With your section of background noise highlighted, go to Effect and then Noise Reduction. Then, click on Get Noise Profile. After that you will select your entire audio timeline before going back to Noise Reduction under Effect. This time click on OK (the default settings are the best in most situations so you do not need to worry about changing them).

Audacity will remove everything that sounds like the sound profile, eliminating your background noise. Sometimes this method will also dull your dialogue, which can be fixed by selecting your entire track and then going to Effect and Amplify. Increasing amplification will fix any muffling of your audio.

Export your corrected MP3 from Audacity and import it into Filmora. Then, drag it into your music track. Syncing your audio should not be difficult, but you can always use your original audio to help you line it up properly if you need to. Just look for a significant spike in your audio waves in both your MP3 and the original audio and make sure they are right on top of each other.

Then, since you no longer need your original audio, you can delete it. Right click on your clip and select Audio Detach. Once your audio is in its own track just select it and click delete.

Sometimes background noise is so minor that you do not want to bother going through the process of removing it. In these situations it may be easier to cover up your background noise than to remove it. This is as simple as dragging a song into the music track of your timeline and adjusting its volume so it is not loud enough to draw attention away from your dialogue. Chances are you want to add background music anyways and this is not even an extra step.