Cleaning background hiss from video audio tracks


A quick tutorial on removing the background hiss or inherent noise from the audio track of a video recording. It takes only a minute or so once you're used to it, and can help clean up the sound in your video clips. All you need ahead of time is a pre-recorded clip in a quiet room for the baseline hiss/noise.

Note that inherent or microphone hiss is different from ambient background noise, as in, the sounds from the environment such as wind or traffic or ventilation systems. These are harder to deal with since they are usually quite variable.

As noted, this works well simply for audio tracks too – just record 4-8 seconds of silence before starting to speak, and use that portion as the baseline noise profile. Audacity 'subtracts' that from the entire audio track. Used properly, it can make the background noise nonexistent and seem like the recording isn't even playing until you speak.

If you end up using different microphones in different situations or with different video recorders, as I do, it's best to have silent noise samples for each combination. It doesn't hurt to actually record the silent noise sample just before or after you've captured the video that you need to clean up, so the sample is as closely matched as possible.

Very Important: Don't do any other edits that might affect the length of the audio clip or it won't match to the video, and you'll end up doing a lot of synchronizing hoohah. This means no clipping and no pitch or speed changes. Do these in the video editor after you've synced the audio back with the video.

Audacity sound editing software

Kdenlive video editing software (though you can use any non-linear editing suite that allows you to separate the audio tracks from the video.)

As with all projects, the best practice is to always maintain your original files, so you can easily start again if the edits turn out to be less-than-ideal – I have often found that everything sounds fine until I reach certain points in the recording, where crucial bits were dropped out. I could easily go back to the original to restore the sections I needed, or re-apply the noise reduction with better settings.

You should experiment with these settings, too – never assume that if you've had good results with one collection of settings, that these will be able to be applied wholesale and repeatedly. And again, err on the side of weaker results that might let a little hiss come through, rather than being too aggressive and producing weird distortions, warbling, or dropouts. Remember that audio recorded outdoors will always have a little background noise, from wind and traffic and so on, and this changes enough that no one sample will eradicate it all, but it will likely sound very weird if you try. Better to simply reduce the overall volume of the track rather than try to get rid of ambient background noise.

I hope this helps improve the sound of your video productions. Good luck!

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