Here is a list of steps to troubleshoot and fix OneNote audio quality issues:

1. Check the default audio devices in the control panel settings to make sure the correct device is selected for playback and recording.
2. Check audio settings in OneNote.
3. If inputs are connected to external devices, check that devices are connected correctly and that the devices support audio quality needs.
4. Ensure that the microphone is working properly using a recording and playback test.
5. If all the above fail, consider restarting your PC and/or reinstalling OneNote.