There are two separate systems that can produce voices overlaying the audio.
Voice announcement of Roku menus, button presses, etc.
A feature called Screen Reader (renamed from Audio Guide in Roku 10.5) announces where you are in the Roku menus for the benefit of the visually impaired. At some point you may have hit the * key on your Roku remote four times in a short period of time. This is a shortcut that toggles the Screen Reader feature on and off, so four quick presses of the * key should toggle the feature back off.
To deactivate the four-* trigger shortcut altogether use menu path Settings > Accessibility > Shortcut (in the Screen Reader section) > Disabled
Wrong language or verbal description of action on screen when watching program
Some programs contain multiple audio tracks that can be selected, such as different languages or verbal action descriptions for the visually impaired.
The Roku default method of accessing your choice of audio track is to press the * key on your Roku remote while viewing the program and examining the options presented.
But more and more channels are not using the Roku default but instead substituting their own method of access -- I'm guessing this is so they will have consistent controls with versions of their app running on platforms other than Roku. Often these options are accessed by pressing the up and/or down cursor control keys while viewing the program to pop the channel's own control options on the screen.
