How to Convert Mono to Stereo in Audacity

The Difference Between Stereo and Mono Formats

Looking at the waveform on any of your editing software you will notice that the audio either has a single waveform or two waveforms. The single one is a mono track while the two channeled one is a stereo.

Here is what these two files will look like when imported into Audacity. A is a mono audio file and B is a stereo audio file. When played back, experienced audio engineers, as well as some regular listeners, will be able to notice the difference between the two right away. The average listener may not be able to put their finger on it, but the difference is usually audible.

In this article, we will look at the process of converting a mono audio file to stereo. You can also check out our article on stereo to mono conversion in Audacity which details the process the other way around.

Converting Mono To Stereo in Audacity

Go ahead and launch Audacity, then import the audio file using Ctrl + Shift + I keyboard shortcut or click File. Next, click on import and then click on Audio.

Your opened file should have one channel just like the one shown in the screenshot below. Remember, you don’t always have to open a file in audacity and see the waveform to know that it is either a mono or stereo, you can often just listen to it and tell right away.

Check the panel on the left for the file information.

Next, select your file. You can double-click on the audio wave or click on the file information panel on the left of your screen as highlighted below.

Another way is the use of the keyboard shortcut Ctrl + A or clicking on the select button on the track information panel to the left.

Once the file is selected, go over to edit on the menu tab. On the dropdown, select Duplicate. Alternatively, you can use the shortcut keys Ctrl + D.

You will then have two audio waves.  Duplicating the audio means creating a second identical waveform.

Note that these are two mono audio files hence they need to be merged into one stereo format file. Check the information panel and you will notice two pieces of information for each file.

To combine the two press Ctrl + A to select all the files. Next click on the arrow in the file information panel as highlighted below. (Do this for the audio waveform on top as this option will be greyed out in the option below.) In the dropdown options click on Make Stereo Track to merge the two.

Once you select that option, both files will be combined into a single audio file with two channels. Compare the information and appearance in the information panel before and after the merger. You will now notice that the audio file has changed to stereo.

You can also check if the audio is stereo by trying to do any edits on the file. Since Audacity recognizes the file as stereo, all functions will be applied to both channels. Whether you select the file or trim a part of it, whatever you do applies to both channels as it is a singular merged file now.

To put this to the test, here is an instance where I will try and delete a part of the audio file. First I select the part of the audio which I want to remove. The selected bit has bits of silence and also some unnecessary parts.

Notice that both channels are selected, meaning it is now a single stereo audio file. If I press delete or backspace to remove it this will affect both channels.

When you are done remember to either save the project or save the file by exporting.

Click on File in the menu tab to open a drop-down. Hover your mouse over Export to open another dropdown option. Click on the Export as Mp3 or Export as wav depending on your preference

Why would you Convert Mono to Stereo in Audacity?

I recently had this audio file that was recorded by an online screen recorder and video editor site. The right channel did not pick any audio. When playing the file on the computer, only one side of my headphones was getting the playback. Here is the file that I worked on.

In A the information panel area, the audio file details show it as being a stereo file. The B section, which is the right side of the audio has no sound. The audio is currently playing and by looking at C which shows the playback level of the audio it only shows that the Left side is the only channel playing audio. 

To fix this file we need to go through the process of first merging the two channels which is a conversion of a stereo file to a mono file. For a more comprehensive guide on converting stereo to mono check out the article on stereo to mono conversion.

But here is a quick rundown. Click on the arrow pointing down on the

 information panel area. On the drop-down click on the split stereo option so that the right and left channels exist separately.

Next, you will have two separate files. I am removing the one on the bottom by clicking on the X button as that is the faulty channel.

Now you have a mono audio file with the left and right channels having a playback sound.

Follow the steps highlighted in this article to now convert the audio file to stereo starting with

1. Selecting your file.
2. Duplicating the file.
3. Then lastly merge the files by using the Make Stereo Track option

In Conclusion

There are other instances where you would want to convert a mono file to stereo. But first, you will have to assess whether the stereo file will fit better than the mono format in that instance. Picture this, you are setting up a stereo sound system for a party. You have two speakers for audio playback. It will be extra thoughtful of you if you convert your stereo files to mono. The invited audience might not notice it as the difference is negligible at times. If you play stereo or mono audio on your phone on loudspeaker right now you would not notice this. Why? The left and right speakers are close for you to get the variation. Similarly how you place your speakers at the party will help with how your guests listen to the sound.

Here is my quick summary. If you have a faulty recording where one channel had an issue like the case that I described in this article, you can fix one channel by having the audio file converted into mono. Then use the process described in this article to convert it to a stereo file with two channels with similar playback quality.