The Ruling on uttering the Intention aloud
What is the ruling on uttering the intention for prayer and Wudhu aloud?
The ruling for this is that it is an innovation. Because it has not been transmitted from the Prophet (sallallaahu alaihi wa sallam), nor from his Companions, may Allaah be pleased with them, therefore it should not be done. The place of the intention is in the heart and there is no requirement to pronounce it. And Allaah is the Granter of success.
Shaykh `Abdul-`Azeez Bin Baz
Fatawa Islamiyah Vol. 2 Page 252