Azaan from multiple mosques in the same vicinity

I live in a Muslim-dominated locality. Some of my friends who are Hindu also live in the same area. There are close to 4 to 5 mosques in the vicinity not too far from each other and they call for prayer at the same time (plus minus a few minutes). My friend asked me a question if Azaan from the mosque is a call for prayer to the people, then won't a call from a single mosque will do the job? Why does every mosque in the same local vicinity need to make the call for the prayer?