Reference: Sharh ‘Umdatil-Fiqh – Tape No.8, Question No.31
Question: When it comes to selecting a mu.adhdhin [to call the adhaan], should we look at how loud his call [to prayer] is, or how beautiful it is?
Response: [It is better to look for] both how loud his call [to prayer] is and how beautiful it is. If, however, his call [to prayer] is beautiful, but the people cannot hear it, then what benefit is there in that?! [In which case] looking for someone whose call [to prayer] is loud will take precedence over the beauty of his call [to prayer].