Due to poor recording and encoding, sometimes the audio volume on the two channels of a stereo audio file do not match. When such an audio file is played back on the computer or on a music player, one speaker plays louder than the other, and the stereo surround effect is lost. Depending on how bad the mismatch is, it may be impossible to hear the low playing channel over the high playing one. Trying to adjust the volume with the volume knob is futile since the volume control acts on both the channels at the same time.
A workaround to this problem is to adjust the left-right speaker balance on the music player.
But this is not a permanent solution and you have to set the balance back once you are done playing with the faulty file. In this article we will see how we can fix, what I believe, is a common problem.
You will need a free, open source program called Audacity. You will also need the LAME MP3 encoder plugin for Audacity. Download both from the links provided below:
Install Audacity and then install LAME MP3 encoder to a location which you can easily access. We will need that later.
Open Audacity and load the faulty MP3 file from the File > Open menu.
Directly to the left of the track appears the Track Control Panel, as indicated by the red marker.
Click on the small black arrow on the right of the Track Control Panel to reveal a menu. Select the option “Split Stereo Track” from the menu.
Once this option is selected, a second Track Control Panel will appear adjacent to the second audio channel of the stereo file. The track on the top is for the left channel while the one at the bottom is for the right channel.
By now you already know which channel has the low volume. If the volume on the left speaker is low we have to increase the volume of the left track (top). If the volume on the right speaker is low we have to increase the volume of the right track (bottom). BUT, what if your speakers are set up incorrectly? That is, the left speaker is placed on the right and the right speaker on the left. If so, then what you think is the left channel is actually the right and what you think is the right channel is actually the left.
To clear this confusion, click on the Solo button on the Track Control Panel of the top track and click on Play. This should play the music through the left speaker and right speaker should be silent.
Once you have correctly identified the channels, move the Gain slider of the channel that has a lower volume towards the right to increase the gain or the volume of the track. Listen to the result by clicking the play button and adjust accordingly. (Make sure the Solo button is unselected).
When you think the volume of both the channels are appreciably equal, click on the File menu and choose the option “Export to MP3”. Here you will get an alert box telling you that the LAME plugin is missing, and then ask you if you want to locate the lame_enc.dll file.
Click YES and locate the said file on the directory where you installed LAME MP3 encoder. Finally save the exported MP3 file.
A note of caution: Increasing the gain of one channel (or both) may lead to ‘clipping’ of the audio signal, producing distortion. Keep a close eye on the volume level indicator at the top as you adjust the gain. Try to keep both green bars at the same level and make sure it does not overshoot.