Adjusting levels of mp3 tracks

I am running Audacity on an Intel Mac running OSX

I have ~30 mp3 tracks that I am using for a research project. They were all downloaded through Amazon and I’ve broken them down into 10 second clips. I am playing them through an iPod for my research project and when I made output level measurements all of the clips were different levels. But I need to adjust them all to be the same level- is there a way of doing this?

Thanks in advance.

That depends on what you mean.

You can easily adjust the “peak level” using “Normalize”. Normalize will adjust the maximum level to a set amount, for example -3dB, or 0dB. However this does NOT mean that they will all sound as loud as each other. Loudness is a subjective measurement that depends on frequency, average power levels, and the individuals hearing. If you want the clips to sound the same loudness, then you will need to listen to each one and adjust the volume manually. There are various methods for adjusting the volume, but probably the most convenient for your purpose would be to use the volume slider on the left side of the audio track.

Note that MP3 is a “lossy” format - each time you decode an mp3 for editing and re-encode as an mp3 there will be a loss of sound quality.

Depending on your purposes, you may find it better to use a player that supports “ReplayGain”, rather than editing the files.