Sandra, I'm no expert, but this is how I'd do it:
Open up each reader's file in your audio software. Use a TOUCH of compression on everyone's file, so that you have an easily visible "peak".
These compression settings, approved by my sound engineer brother-in-law, work well, evening things out without making anything sound robotic:
http://flickr.com/photos/kayray/200466043/in/set-72157594219410887/
(Too much compression is very very bad, so be careful if you tweak the numbers)
Obviously, your software will look different, but the options should be about the same. You can alter the "post gain" number to boost the volume more or less after compression, as appropriate.
Then, when all the files are compressed you can squish the view magnification down and see how the waves compare. Then raise up the volume on the softer ones (but beware of ugly background noise) until they match, more or less. Do some tests with your own ears, 'cause sometimes wave forms that LOOK mostly the same will SOUND a little different.
Then you should be able to cut and paste everything together.
If there's not too much variation in volume, it might work to do the cutting and pasting first, then run compression a couple of times on the finished thing to even everything out.
I'm no expert, though! I'm sure there's a better way and someone here will know it :)
(I can provide example screenshots if you want...)
