If you are talking about the sound that starting at ~00:00:06 then it sounds for me like CPU was overloaded. Maybe you applied too much filters to your mic or the OBS scenes were overloaded in some other way?
There is log-file analyzer for OBS, try it, it may give you some tips what to do next:
OBS (Open Broadcaster Software) is free and open source software for video recording and live streaming. Stream to Twitch, YouTube and many other providers or record your own videos with high quality H264 / AAC encoding.
obsproject.com
Also, by default the "Desktop Audio" device Properties have the "Use Device Timestamps" checkbox checked (you set it differently, why?).
99.gigafile.nu
