It is forbidden to raise one’s voice in such a way that it disturbs others’ prayers, even if it is done while reciting the Qur’an. Teaching or imparting knowledge (to others) is exempt from this prohibition.
Ibn ‘Umar relates that the Prophet sallallahu alehi wasallam entered upon some people while they were praying and they were raising their voices in the Qur’anic recital. The Prophet said: “One who is praying is in a private conversation with his Lord so he should be mindful of whom he is conversing with. And you should not raise your voices against each other in [the recital of] the Qur’an.” This is related by Ahmad with a sahih chain.
Abu Sa’ id al-Khurdi reports that the Prophet was making seclusion (i’tikaf) in the mosque and he heard the people reciting aloud. He removed the covering and said: “Verily, each of you is in a private conversation with his Lord so you should not disturb each other. And you are not to raise your voices against each other in the recitation.” This is related by Abu Dawud, an-Nasa’i, al-Baihaqi, and al-Hakim who grades it sahih according to the criteria of al-Bukhari and Muslim.