Shiva Purana
तर्जन्या पिहितौ कर्णौ पीडयित्वा मुहूर्त्तकम्॥ तस्मात्संश्रूयते शब्दस्तुदन्वह्निसमुद्भवः ॥ २५ ॥
When the ears are closed with the index finger for a short while a kind of sound is heard as that of a blazing fire.
english translation
tarjanyA pihitau karNau pIDayitvA muhUrttakam॥ tasmAtsaMzrUyate zabdastudanvahnisamudbhavaH ॥ 25 ॥
hk transliteration by Sanscript