Hi! I use several apps for learning at a time and a little independant study in addition. I have found remembering kanji readings and even general meanings hard to memorize on most fronts except for my app specifically for kanji studying (which ive fallen behind on using for several irl reasons just cutting my study time short), which allowed me to use my phones text to speech to read the readings aloud to me (though as tts instead of real voices, it was far from perfect often times). I think this helped me alot and audio feedback is whats really missing from renshuus kanji quizes. having auto audio play on vocab and sentences here has also greatly improved my ease of learning in those areas, so I think itd be very good to have the option for kanji quizzes to not be silent
Unlike Chinese, Japanese characters do not have pronunciations. Instead, they have readings, which are at best a crude guide to the way the characters are pronounced in words, words being the things that have pronunciations.
So you will find that renshuu has audio for words and sentences, but not kanji. This is not an oversight; it’s a considered choice.
There are many single character words, and if you like, you can study those with audio.