I see that you're hearing distorted sound when using the YouTube application and Safari when you play videos through either. I'm happy to help.
How to force an app to close on your iPhone, iPad, or iPod touch -- First, force close the YouTube application and Safari if they're open, then -- Restart your iPhone, iPad, or iPod touch -- Once it's returned to the Home screen, test the issue.
If an app you installed unexpectedly quits, stops responding, or won’t open -- If restarting your phone didn't resolve the issue, follow the steps in this article for the YouTube application Even though the title of this article isn't quite what you're experiencing, the steps provided can help.
How to back up your iPhone, iPad, and iPod touch -- Since Safari is a native application which can't be removed, please be sure to have a fresh backup to keep your personal information safe. In order to back up your Health data, the backup needs to be encrypted. iCloud does this automatically, but iTunes doesn't. If you'd like to use iTunes to back up your phone, refer to this article: About encrypted backups in iTunes
If you can't update or restore your iPhone, iPad, or iPod touch -- Even though the title of the article isn't specific to your issue, the section titled "Put your device in recovery mode and set it up again" will walk you through all the steps to reinstall the iOS software on your device. Test the issue once your phone has returned to the Home screen.
Let me know how that goes.