In most states, the Department of Motor Vehicle office provides audio manuals for commercial driver's license applicants. DMV.org offers a directory of each state's DMV website, as well as instructions on how to use the audio manuals to study for the license test.
To find the DMV website of each state, visit DMV.org and click DMV Office Finder from the top menu. Choose a state on the interactive map, or select a state on the drop-down menu. Locate that state's DMV website under DMV Office Locations. On the state's DMV site, audio manuals are often located under Forms or Publications.
On Minnesota's Driver and Vehicle Services page, for example, the audio manuals are located under Forms/Documents/Manuals. The commercial driver's license audio files include 12 sections of audio manuals. The files are available in English.