Ever have your Chromebook reading a page for you? It is possible that you (or someone) has enabled ChromeVox. ChromeVox is Google's screen reader.
There are a few ways to enable or disable this feature.
You can turn ChromeVox on or off from any page by pressing Ctrl + Alt + z. On tablets: Press and hold the Volume down + Volume up buttons for 5 seconds. While holding the buttons, you’ll hear a sound to indicate it’s working. Keep holding the buttons, then ChromeVox will start speaking.
It is possible that it was turned on by selecting the system menu (bottom right corner where you see volume) and then choosing accessibility and turn off ChromeVox.
Embedded below is a 1 minute and 39 second YouTube tutorial.