SHAFAQNA – The Grand Ayatollah Shahroodi answered a question about the allowed sound level of call to prayer (Adhan) from a Mosque.
Question: Please specify the allowed sound level of call to prayer from the minaret of the Mosque. Considering that by using the electronic devices the sound of call to prayer can be amplified many times, what is the allowed sound level which can be broadcasted? It is reminded that the sound level for those neighbours nearer to the Mosque is more than the usual level especially at the time of the dawn when the sound of the surrounding area is less and this has caused criticism.
The Grand Ayatollah Shahroodi: There are no religious obstacles in using the mentioned devices for broadcasting call to prayer; unless it causes annoyance to believers especially the neighbours of the Mosque which in this case it is necessary that the sound be adjusted to the normal level.
Source: PERSIAN SHAFAQNA