Is there any free tool capable of doing the job?
You didn't supply very much information, such as your OS and your desired output format, so I can not give you a detailed answer.
CAF is a container format that can support several audio formats, but Apple Lossless (ALAC) is probably the most common.
ffmpeg can decode ALAC in CAF:
This can be turned into a "batch" command with a Bash "for loop".
sox can be added to this example to normalize your audio:
As usual, using a recent ffmpeg is recommended since development is so active. See the FFmpeg download page for various methods to acquire it.