Many of those who have lived in Azerbaijan and other Muslim countries know this sound - in the morning and the evening most notably. I remember being awoken by the electronic muezzin in Lenkoran at what seemed to be an ungodly hour. I was staying near the Iranian-supported mosque, which may have explained its volume.
In Baku, I rarely noticed the muezzin, although I lived right next to the Old City.
I find it very hard to believe that the authorities are responding to any complaints for residents. The idea that authorities would respond to citizen complaints in general is just laughable. They are asking for the mosques to turn down the muezzins in a direct expression of power. They are asserting their dominance over the religious establishment. Religion should serve the state. Those who are involved with religious matters should not forget this fact.