Disable text to speech at the TTS engine level
Have a Samsung device? Can't get certain apps to stop speaking certain phrases, like "Loading started," even though you disabled text-to-speech, Talkback, and other speech related services? This is a simple text-to-speech engine that does not output any audio, that can be used as a workaround for these known problems with some Samsung phones.
The problem usually starts occurring after you install and enable an accessibility-related app (like a notification LED control app) and has no known, working fix that I was able to find, so I whipped up this as a work-around for myself.
Based on the "RobotSpeak" sample application, this simple app is free and ad-free as so many more minimal-effort Google Play apps should be.
Simply go into Settings -> My Device -> Accessibility -> Text-to-speech options to select it as your text to speech engine. Note that this will disable text-to-speech on your device for any applications that use the TTS service, and that this may include GPS apps or other TTS-related services that you use.