You might want to take a look at The Levelator, from The Conversations Network.
This is a free software program for Windows, Macintosh and Linux operating systems.
It does what its name implies. It smooths out the high and the low points of your audio source without distortion. For example, The Levelator can take two voices and even out the differences between the two.
The program can't work miracles, bad audio is still bad audio. This is one software program can help you to make sound leveling corrections fast and easy. I would suggest that you download the product directly from the website to make sure that you are getting the most recent version.
For more information about The Levelator:
- From PixelHead Network - How To Use The Levelator to Normalize Audio
- From Joe Dale - a text/screenshot version of how to use The Levelator
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