I would like to mute the sound that plays when I get a correct answer. It gets annoying after a while, especially when I'm doing the mastery exercises. Also, I would like to do this in a room where someone else is asleep, on trains, and in hotel lobbies, where I don't want to disturb others. I can update this (and have updated it) in my profile on the web site, but it does not carry over to the iPad app, nor is there a way to set it there. It gets annoying after a while, at least for an extremely motivated 65-year-old adult learner who is not into video games and thus doesn't need a game-like atmosphere as a "reward" for getting a correct answer. (But I must admit that I do like the confetti that falls across the screen when I get a perfect score and the hopping animals in the mastery section after I've reached 100% mastery.)
Yes, I know the workaround is to mute the device (turn the volume all the way down), but that mutes everything else on the device, and sometimes I need this for another app (such as playing soft classical music in YouTube or Google Play Music while studying).