Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ex-sŏno, ŭi, 1, v. n., to resound (postAug. and very rare): ceteri convivae ingenti clamore exsonabant, Petr. 73: navigium exsonat cantibus, id. 109: omnia risu, id. 19.