digital audio editor

If I understand you correctly...;)
To do such thing you should calculate the instant power. To do that you can take wave buffer and summerize the absolute values of the data. The buffer length you should choose according to the sampling frequency. For example, if the sampling frequency equal to 8000 Hz and you want to update progress bar every 1 second it is necessary to take 8000 points.

Code, using C# may look like that:

public static double getPowEst(short[] data)<br />
{<br />
double powEst = 0;<br />
			<br />
for(int t=0; t<code><

data.Length; t++)
{
powEst += Math.Abs(data[t]);
}

powEst = powEst/data.Length;

return powEst;
}