The 'video' element is inaudible when 'muted' is false or 'volume' is zero.
Test Assertion
Test fails if audio is heard or the text 'Your browser does not support media elements.' appears anywhere on this page.

http://www.w3.org/TR/html5/video.html#video

When a video element is potentially playing, it represents the frame of 
video at the continuously increasing "current" position. When the 
current playback position changes such that the last frame rendered is 
no longer the frame corresponding to the current playback position in 
the video, the new frame must be rendered. Similarly, any audio 
associated with the video must, if played, be played synchronized with 
the current playback position, at the specified volume with the 
specified mute state. 

Your browser does not support media elements.