(If instead you are getting distorted audio when recording your microphone on Windows 10 then please see this article: http://feedback.screencast-o-matic.com/knowledgebase/articles/693249)
Steps to fix slow and distorted sound when recording your computer's system audio:
1. Right clicking the speaker icon next to the clock in the lower right of your screen choose "Playback devices"
2. Right click on the currently selected speakers and choose the "Configure Speakers" option.
3. Make sure the "Audio channels" setting is set to "Stereo".