My Android app sound effects stop working when I turn off Audio

I have already tried reinstalling the app but nothing helps. I want to have the sound effects turned on while NOT hearing the audio. It makes my learning process more fun.
It should be possible to do in the settings but the moment I turn off the Audio, the sound effects stop working, too - even though I purposely left them ON.

If you turn off audio then you will hear … nothing! That’s quite the way it’s intended to work, not just for Memrise!