I have an audio book that is over four hours long
You can’t submit that. You should be in chapters and each chapter no longer than 120 minutes, usually much less.
That’s from here.
- A way to skip to a particular time code of the audio book
Audacity doesn’t support SMPTE Time Code or Frame Code. All we have is running time. We do have labels.
Please note near the bottom of the instructions the ability to force synchronize the voice track and the labels. If you don’t, one will change without the other.
- A way to record voice directly into a selected part of the audiobook
We do have Punch and Roll.
But that doesn’t put new work in the middle of old work. That’s an electronic version of audiotape which destroys everything from the in-point to the end of the chapter.
Patching in the middle of a chapter is not for the easily frightened. It’s terrifically difficult to make everything match and ACX is watching for any distracting error.
One way is to record a correction is on a second timeline and then use the Time Shift Tool (two sideways black arrows) to push the correction into place. Then split the original track so the correction fits in the hole. Audacity will play both tracks at once unless you stop it. It exports work that way, too.
None of this is going to work if you don’t have convenient chapters. Reading corrections into a whole book all at once is a nightmare.
I can make this worse. Do you pass technical standards, loudness, noise, etc?
Read a 20 second test clip and post it here on the forum.
Please follow the instructions. Don’t help and don’t ad-lib.