I am trying to raise the volume of the recording I am working with. When I use the sliding scale on the Amplify feature, the “ok” button to save changes becomes grey and is not an option when I raise the amplification. However, when I lower the volume, it reappears.
In digital audio, the absolute maximum valid level is 0 dB. Amplifying audio to greater than 0 dB is possible in Audacity because Audacity uses 32 bit float format, but sound cards do not use float format for audio, so they “clip” the tops and bottoms of the peaks - a nasty type of distortion.
By default, the Amplify effect will amplify so that the highest peaks in the selected audio will exactly reach 0 dB, but no higher. This is the most that the audio can be amplified without clipping. By default the Amplify effect will not allow you to amplify higher than 0 dB and will grey out the “OK” button if you attempt to do so.
More about the Amplify effect here: http://manual.audacityteam.org/o/man/amplify.html