Is it recommended that the muezzin have a loud voice?
Chapter on Adhan
Al-Mughni
Book of Prayer
Primary text
It is recommended that the muezzin possess a loud voice ('sayyit') so that people can hear the call. The Prophet, peace be upon him, chose Abu Mahzurah for the Adhan due to his loud voice. Furthermore, in the hadith of Abdullah ibn Zayd, the Prophet told him to teach the Adhan to Bilal because Bilal had a more melodious voice ('andā ṣawtan') than him.
Supporting text
It is also recommended that the muezzin have a beautiful voice because it is more tender upon the listener.