There seems to be a mismatch between the spoken pronunciation of this word and the phonemic transcription, as given in the entry under susurration/susurrus, at: https://en.oxforddictionaries.com/definition/susurration . The recording of the spoken pronunciation seems to be (to my ear) /ˌsjuːsʌ'reɪʃən/ . The written transcription, however, is: /ˌsuːsʌˈreɪʃ(ə)n/. Maybe /sju:/ is right; or /su:/ is right, or maybe both. It is confusing having this mismatch.
The entry points out that this word is used in literary style. I wonder how the dictionary makers go about deciding the pronunciation of a word such as this. Used mostly in literary style, and therefore mostly written form, examples of its pronunciation must be rare, as the word is. Come to think of it, there are probably words in the language, rare and literary, which have never been spoken in recent times, at least not since the invention of mechanical means of recording. In a descriptive approach to dictionary making, how is their pronunciation to be ascertained? And how described in the dictionary entry?