Thank you for your report.
If you are trying to turn ChromeVox off, you can do this by pressing ctrl+alt+z 
I noticed that you are running an old version of Chrome. Please try to update to the latest version if possible.
Instructions for updating can be found here: https://support.google.com/chromebook/answer/177889?hl=en

If ChromeVox still won't stop talking, please file another report and describe in detail the issue.