Lewis & Short

con-frĕmo, ŭi, 3, v. n., to sound aloud, resound, to murmur loudly, etc. (poet. and rare): confremuere omnes, Ov. M. 1, 199; Stat. S. 1, 6, 72: confremit et caelum etcircus, Sil. 16, 398: collis, Stat. S. 1, 4, 14.