Disclaimer: this post is it not directed at casual learners.
Most people who learn Japanese through immersion rely on stuff like anime, music, visual novels, tv shows, manga, books, light novels etc. But few have ever asked this simple question: what is the most efficient way to consistently learn new words at a fast pace and practice your listening skills to boot? After trying out all of the media above, my answer is: audiobooks, and it’s not even close.
Audiobooks have a huge advantage over most other media: they are nothing more nothing less than read aloud books. That means that you benefit on the vocabulary front, since books tend to make abundant use of vocabulary, and also on the listening front (listening as a skill is significantly more important than reading skills, unless your goal is to only read).
So why are audiobooks better than anime, tv shows or music, you might ask? Two reasons. The first is that you are bombarded with new words all the time, because that’s what books are made of, words and only words. The same cannot be said of anime, tv shows or music. In fact I’ve come to conclude that using songs to learn Japanese might be the most inefficient way out of all of them, not only because of copious chorus cycles, but also because most songs dedicate at least 20 or 30% of the track to instrumental only. It’s just not very time efficient. Not to mention the often archaic/unnatural choice of vocabulary. The second reason is that some people have auditory processing disorder. If you have that disorder, you basically process sound differently to most people. That means that sound effects, BGM and stuff like that become a big problem, so songs are out of the question. Same for anime and tv shows or movies, although to a lesser extent. This is why some people have an easy time talking to Japanese people in real life and understanding them, but fail miserably to have a comprehension rate above 80% when they watch anime or movies. So much for “audio in anime is super crisp bro, if you can’t understand anime, you’re screwed if you try to listen to real Japanese people, they slur a lot!”
Another reason I think practicing listening skills is more important than reading skills is because listening to words helps you memorize them faster than merely reading them. I’m sure some people are different, and they actually have photographic memory so they have an easier time remembering words they read, but I don’t think that’s the case for most people. I’ve seen studies over the decades advocating for one over the other, but from my personal experience learning multiple languages and being with other people who did the same, if you want to memorize words, output is always superior to input, and listening is superior to reading.
To make full use of audiobooks for learning Japanese however, I recommend having the source material at hand as well so you can check whether you misheard something, or to more easily look up words.
The only downside to audiobooks is that your level should be at least advanced, and the reason for that is that you’ll come across lots of unknown words, and if your vocabulary size is, say, 10k, you’ll get overwhelmed really fast. And when I say you should know lots of vocabulary words, I mean it. Remembering what a word means only seconds after you heard it is useless, because audiobooks are fast paced, unlike real life, where people don’t speak as fast and they usually intersperse their sentences with lots of filler words. The absurd amount of homophones in Japanese is also a problem if you’re not extremely comfortable with kanji. Which means that before you can cozily coast your way through your Japanese learning journey, you need to get dirty with kanji, so make sure to read books before focusing on audiobooks.