I get told that my answer is “a little bit off”. Okay, fair enough…but “Hearable” is not a verb, intransitive or otherwise. It is an adjective. That is all.
Nor is “audible”. Your answer was accepted because WaniKani thought it was a typo but it’s close enough either way; as long as you know what a certain word means generally it’s fine, you shouldn’t be translating word for word jp → eng very often either way.
Additionally, even if “hearable” is not a verb, “to be” is.
I assume you are commenting on WaniKani’s primary meaning for 聞こえる (a verb) being ”Hearable” (an adjective).
I agree that this is weird. Possibly it’s justified because Japanese grammar allows any verb in plain form to be used adjectivally, so a verb sometimes takes on the role that would be played by an adjective in English, e.g. 聞こえる音 (a hearable sound), or 害のない人間 (a harmless person). This is similar to how participle verbs in English can function adjectivally.
(Also, I think WaniKani sometimes just wants to offer a meaning that is bit snappier and easier to write.)
This is a valid defense. I just think it’s a little inconsistent given the propensity in 100% of other cases of verbs I’ve encountered in my 16.8 levels of WK. WK will mark a translation of a verb wrong 100% of the time if you forget to put it in the English infinitive form. Well, 100% except for this case.
However, don’t get me started on how adjectives/adjectival nouns are handled. I’d rather not stir up actual controversy.