Hawzah News Agency – The merciful prophet of Islam (pbuh) says:

يُغْفَرُ للمؤذّنِ مَدُّ صَوتِهِ وبَصَرِهِ، ويُصدِّقُهُ كلُّ رطْبٍ ويابِسٍ، وله مِن كُلِّ مَن يُصلّي بأذانِه حَسَنةٌ.

'The caller to prayer is forgiven according to the distance of his voice and his eyes; every wet and dry thing testifies to his credibility; and he receives a reward for everyone that prays in response to his call.'

Source: Bihar al-Anwar, v. 84, p. 104, no. 2