Valmiki Ramayana Yuddha Kanda Sarga 89 Shloka 31

तथा that way, समरयत्तयोः both of them fighting, तयोः both, सःशब्दः that sound, सगगने sky, निष्टनतोः murmur, सुघोरयोः exceedingly frightening, मेघयोरिव like the clouds, भ्राजते was heard

When both of them were thus fighting, the exceedingly frightening sound that was heard was like the murmur of clouds.