This technique may work with a very high known word ratio, because then you really pay attention to the unknown word. And if you are at a high level, you can follow the story in the background, as your main focus is trying to quickly work out the meaning of the new word. But, yeah, I think the ability to control your pace would also solve this issue, which is only possible without the audiobook (or pausing it all the time). Alternatively, slowing down the audio to allow for more time with unknown words. Fast audio is definitely great for drilling words you are somewhat familiar with though.
@davideroccato There are indeed many variables. The comparison for me would more be like reading while listening on LingQ at ~55 wpm, reading while listening on YouTube with Language Reactor at ~150 wpm (I just tested it with the Harry Potter audiobook on YouTube with auto-subs at 1.3x, but having to repeat sentences every now and again) or true extensive reading while listening at 1.65x/~240 wpm. In this case, using my reading while listening speeds, we would be talking about 10M words read as extensive reading while listening, ~6M with Language Reactor and ~2.5M with LingQ. As mentioned, the LingQ reading speed is so slow because of the amount of time it requires to get a decent definition (which often includes pausing the audio to open up a dictionary and write a definition). With the translation under the subtitle on Language Reactor (aka bilingual text), you can merely glance down often to get a good definition, without ever having to click anything, hence the increased reading speed. Which of these three options would you back?
One thing I would like to mention with my above experience of the Harry Potter series is that perhaps my analysis was flawed, as I may not have been able to recognise many of the words in list format, but I could recognise/guess more unknown words in context. So perhaps this means they are partially in the process of being learnt, but just not well enough yet to be recognised in list format, devoid of any context, which generally requires a high familiarity of a word.
@PeterBormann What kind of wpm/wph speed are you looking at for your extensive reading while listening?