If you want to hear exactly how much noise is being removed from an audio file when using BIAS SoundSoapPro, you can switch the program into what's called the "Noise Only" listening mode. By doing this, you will be able to hear just the noise that is being "scrubbed away" using the current noise reduction settings. If you hear audio that you know should be left in the file, you can go back and adjust the parameters until only the undesired noise is being removed.