Audacity Forum

In case there is a similar post on this forum which I missed in my research, first I would like to apologize and second I would appreciate if anyone could point me to it.
I have a collection of mp3 files gathered from different sources (Internet, CDs) and whenever I'm listening them, the amplitude level varies from one file to another. Especially when I'm listening them in my car, it is extremely annoying to reach the volume button and adjust the sound level for (almost) each song. What I'm looking for is a suggestion on how to bring all files to about the same intensity level.
I've read the documentation and I experimented a little bit with Amplify effect but still didn't find a way to attain my goal. When using Amplify, all I have is a visually representation of the sound wave and I have to tell the application the amount by which the whole track will be amplified. How much does this amount has to be, 2dB, 5dB etc.? Let's say I manage to get a reasonable value for the present file, but what about the next one and how about the twentieth one ? I know I could use trial and error (like listening all my files, making adjustments and repeating over an over until I'm satisfied with the result) but is there a more rigorous approach ?
One similar but commercial sound editing program I was using in the past had an option to analyze the whole file and compute some sort of an average value in dB. All I had to do is to take one file as a reference and compute its average after that, take every other file, compute its average and compare it with the reference value. The difference in dB was the exact amount I had to input into the Amplify plug-in. Is there an add-on for Audacity that can do this ?

<<<Is there an add-on for Audacity that can do this ?>>>

Oh yes. Chris's Compressor.

http://pdf23ds.net/software/dynamic-compressor/

Compression processing very much like this are the reason you never have to adjust the volume when you're listening to the radio in the car. I change the compression from 0.5 to 0.77 and the effect is very like KPCC-FM in Los Angeles.

Koz

Thank you for your answer.
I knew a little bit about Chris's Compressor and following your suggestion, I went again to the website in order to read the documentation. However, my problem is not that some parts of a file are louder that other parts, it is from one file to the next one that I have to adjust the volume. Sorry I did make this more explicit, what I need to do is to amplify or attenuate one whole file with a certain amount in order to bring the whole collection to about the same level. As far as I could see from the documentation, with Chris's Compressor compression can not be applied over multiple files simultaneously, am I missing something here ?

So you have a basket of sound files over by the credenza and you want to open them up one at a time, set them to the same level and then export as new files?

I have a horror of exporting the work as the same filename. One mistake anywhere and you have no show.

The problem will be forcing Audacity to batch process in that manner, not which tools to use. Audacity 1.2 is useless for this as it doesn't have batch tools at all. Audacity 1.3 batch tools are called Chains and are pretty limited.

http://manual.audacityteam.org/index.ph ... Processing

Koz