Sometimes it comes to me like the ringing of a bell, and that is the hardest for me. When it leaves me I remember what it has said. And sometimes the angel appears to me in the shape of a man, he talks to me, and I understand what he says

Al-Hārith ibn Hishām (may Allah be pleased with him) asked the Messenger of Allah (may Allah's peace and blessings be upon him) how the revelation came to him. The Messenger of Allah (may Allah's peace and blessings be upon him) told him that the angel, Jibrīl, would sometimes come to him and his voice communicating the revelation was as strong as the sound of a bell. This form was the hardest on the Prophet (may Allah's peace and blessings be upon him) and afterwards he would be overwhelmed and severely distressed and then it would lift. After this he fully understood and had memorized what the angel had said to him. The angel would make a loud sound when he came down with the revelation to distract the Prophet (may Allah's peace and blessings be upon him) from matters of the worldly life and to make him focus on the sound. The Prophet (may Allah's peace and blessings be upon him) would understand what the angel said to him, as he heard nothing but the angel's voice.
At other times, the angel would come to the Prophet (may Allah's peace and blessings be upon him) in the form of a man, such as Dihyah (may Allah be pleased with him) or another man, and communicate the revelation to him, and the Prophet would understand it.
‘Ā'ishah (may Allah be pleased with her) said that on very cold days, the Prophet's forehead would sweat due to the stress of receiving the revelation.