This seems to be a problem occasionally with Vimeo videos (other websites have the same problem). Our videos are hosted on the Vimeo site. To find out what to do, in the google searchbar type: "I cannot hear the sound on vimeo videos". You will see several ways to fix the problem on your computer. It will depend on which browser you are using.
As a quick fix, you can also try another browser and you will probably hear the sound.
Keywords: no audio