Clean Up Audio Files for Transcription [Quick Tutorial]

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Sometimes, when you get an audio file to transcribe, you get one with a lot of background noise that makes it difficult to hear what speakers are saying—especially when they speak softly or just not close enough to the recorder. These tips will help you clean up audio files to make your job easier. If there’s a lot of background noise, or the noise isn’t constant, then this might not help very much, but for the most part, these tips can help filter out rustling, breathing, and other regular background sounds.

Using Express Scribe: The Quick Method

This is a quick option that may not always provide you with the solution you need, but it’s an easy first step that only takes a click of a button. With your file open and selected, go to the “File” menu, go down to “Special Audio Processes”, and select “Background Noise Reduction”.

Image of Express Scribe showing the right menu

Express Scribe automatically runs a process that can clean up the audio file. This could take a few minutes—the 71 minute long file I used in this example took almost three minutes to complete the process.

Using Audacity: The In-Depth Method

Audacity is free software that you can download from It’s a small program, so it downloads and installs easily. Once you’ve loaded your file into Audacity, you get something that looks like this:

Image of an audio file as it appears in Audacity software

The relatively flat sections are background noise, while the spikes represent speech. The first step in reducing background noise in the file is to get a sample of what that basic background noise is, like the constant noise of traffic from outside the room. You can do that by selecting a section of the file where the line flattens out, like this.

Shows selecting a section of audio in Audacity 

From here, go to “Effects” in the menus and scroll down to “Noise Reduction”.

Shows the correct Audacity menu

A menu will appear with two steps. The first thing you need to do is get the noise profile of the short section you selected by clicking “get noise profile”.

Image showing Noise Reduction window

Once you’ve done that, you need to go back into that menu, and this time click "OK". In most cases, the default settings will work well. If you find that isn’t the case, you can go to “Edit” and click “Undo”, and then try again with slightly different settings.

If you get to a part where there are loud noises intruding in the audio (like a siren going past), then you can use Audacity to even out the sound on that part of the file. Highlight it as before, and then go into the “Effect” menu again. This time, select “Leveller”.

Image of Audacity software showing location of "Leveller" function

This will level out sounds over a certain threshold without affecting softer sounds in the audio file. If you don’t have a clear idea of the decibel range, stick with the default, click “Preview”, and then adjust it until you get the result you need.

Leveller progress screenshot

Audacity has a lot of other tools for editing audio files, and it may be worth experimenting with other “Effects” to see if they contribute to a cleaner file. This tutorial only scratches the surface of the options available in this program, so feel free to experiment with the different features and options.

Posted 17 October, 2015

Nicole Walters

Transcriptionist - Proofreader - Writer

I carefully choose projects I know I have the time, expertise and interest in completing. When I make a bid, I have already scheduled the work I could do for you. I currently work for the transcription company, Global Lingo, on a freelance basis, and I have previously worked for Dr Crockett of Dewsbury Hospital. I have a wide range of experience in transcription, research, writing and data entry ...

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