If you are having trouble hearing sound from specific websites (for example, you cannot hear any sounds from any videos in Canvas but you are able to hear sound from videos playing on YouTube) you may have a feature enabled inside of Google Chrome called "Mute site." This helpful feature can sometimes get accidentally turned on, causing some confusion.
When "Mute site" is enabled, a speaker icon with a line through it will show up at the top of the screen for the tab. You can see in this example there is a tab/site that is muted (Canvas) and a tab/site that is not muted and playing sound. (You will only see either of these icons if there is sound/video being played in the tab itself. As soon as the video/audio is paused that icon will no longer show up) It may also show up in the right side of the URL bar with this icon.
To turn this off, right click on the tab and select "Unmute site."
That should restore the sound to that website/tab and remove the line from the speaker icon at the top.
(If the tab is not currently muted, the option will instead be "Mute Site.")
Be wary of turning this feature on as Google Chrome will remember that you muted the site and continue muting it in the future until you unmute the website.