Valmiki Ramayana Yuddha Kanda Sarga 93 Shloka 24

दन्तान् teeth, विदशतः biting, तस्य his, दशनस्वनः sound from his teeth, दानवैः by Danavas, आवेष्ट्यमाणस्य revolved round, महतः huge, यन्त्रस्येव machine like, श्रूयते heard

When he was biting on his teeth (enraged), the sound from his teeth resembled the sound of a grinder revolved round by Danavas.