I think in all these references, O Sensei is not referring to a physical sound, but rather something else. The first quote above is sometimes combined with another doka that talks about the mountain echo, which is a body posture - a posture trained in solo exercise. As a general interest, I'd like to know if that is a substantial relation or mere speculation.
To quote The Princess Bride, "I do not think it means what you think it means." I find most of the doka to be a combination of very clear instruction presented in a package that exceeds my functioning knowledge of my martial arts history, Japanese culture and Japanese language. I think most of the English translations I originally reviewed were intended to be "dummed down" and in many respects I think that work was not done well [enough]. Calculus is "clear as mud," for most of us, yet that truth makes calculus no less real or practical for those who understand it. It does create a distinction between the know/know-nots.
From what little I know, translation is very difficult between Japanese and English. That's one of the things I greatly admire about Chris Li, his blog posts are a lot of work. The two languages differ on the semantic and even pragmatic levels (there are fundamental differences in what there is to be said
and not just in how to say it). So if you want to accurately capture the meaning of the Japanese in English, it isn't going to make a lot of English sense. If you want it to sound good in English, you are going to have to add or subtract shades of meaning from the original. Furthermore, when you get into literature and poetry, there is an entire dimension of clever choices of kanji to express subtle or even multiple meanings. Note that [love-cross] comment in your first doka!
And I believe that Japanese poetry also expresses meaning using the caligraphy itself. So even if you were fluent in literary Japanese and reading it as typewritten characters, you'd still be missing thay layer of meaning.
So I don't think this type of writing is meant to be clear at all, or at least not explicit. Osensei is not trying to say something that is to be specifically interpreted. Not to take away from the importance of Chris Li's translations that he makes available to all of us.