It's the call to prayer, this is the translation:

God is most great. God is most great.
God is most great. God is most great.
I testify that there is no God except God.
I testify that there is no God except God.
I testify that Muhammad is the messenger of God.
I testify that Muhammad is the messenger of God.
Come to prayer! Come to prayer!
Come to success! Come to success!
God is most great. God is most great.
There is none worthy of worship except God.

That's the Muslims call to prayer.