Srimad-Bhagavatam: Canto 7 - Chapter 1 - Verse 24
Sanskrit:
तेषामाविरभूद्वाणी अरूपा मेघनि:स्वना ।सन्नादयन्ती ककुभ: साधूनामभयङ्करी ॥ २४ ॥
ITRANS:
teṣām āvirabhūd vāṇīarūpā megha-niḥsvanāsannādayantī kakubhaḥsādhūnām abhayaṅkarī
Translation:
Then there appeared before them a transcendental sound vibration, emanating from a personality not visible to material eyes. The voice was as grave as the sound of a cloud, and it was very encouraging, driving away all fear.