From Official Kodi Wiki
1 General audio help
This page is a listing of all of Kodi's audio output settings with descriptions. For example setting configs for a few typical scenarios see Audio quickstart guide and for help with problems see Audio troubleshooting Depending on how your equipment is connected together you'll need to adjust the audio settings. The following is meant to act as a guide to get you started, thus you may want to do further adjustments for your own particular set of equipment. This page describes some of the steps you can take to troubleshoot audio problem and gives background information on audio concepts as a foundation for understand why some things work as they do.
2 OS specific help
This page describes how to set up audio for the Windows OS. It covers how to set up Kodi when using either Directsound or WASAPI, and when to use one vs the other. This page describes how to set up audio for Linux-based systems. Primarily, it covers how to setup Kodi when using either ALSA or PulseAudio. This page goes into detail on using PulseAudio on Linux systems. PulseAudio is used when Kodi is installed in a desktop-environment rather than a dedicated/direct boot setup. PulseAudio allows normal video & audio playback in XBMC while at the same time allowing the user to get audio in their browser or other applications. It also allows Kodi playback of video or audio to be paused in order to run a game, Skype or similar. Kodi is set to only use PulseAudio if you have installed it and running.