Du'a upon hearing a dog bark

أَعُوذُ بِاللهِ مِنَ الشَّيْطَانِ الرَّجِيمِ

A'udhu billahi minash-shaytanir-rajim

I seek protection in Allah from shaytan, the accursed one.

Sunan Abī Dāwūd 5103