The copyright Act gives copyright owners certain rights:
right to reproduce the copyrighted work
right to prepare derivative works based upon the work
right to distribute copies of the work to the public
right to perform the copyrighted work publicly
right to display the copyrighted work publicly
The audiobook you create from a copyrighted work is a derivative work (perhaps it is a reproduction; for the analysis it does not matter). It works the other way also.
A derivative work is a work based on or derived from one or more already existing works. Common derivative works include translations, musical arrangements, motion picture versions of literary material or plays, art reproductions, abridgments, and condensations of preexisting works.
It is a violation of the copyright to create derivative works without permission. The commercial nature of the derivative work does not come into play in this situation. Commercial use might be an issue in a fair use defense, but fair use is not applicable based on these facts. Fair use might apply given facts such as: Ten students own copies of the printed work. These students are blind. A teacher reads the book and provides the recording to the students.