Any kind of noisy disturbance can be called an uproar. A large group of political protesters outside City Hall is likely to create an uproar.
There's often an uproar in the audience of a rock concert when the band first appears on stage — people cheer and applaud and whistle. An announcement that the neighborhood donut shop is out of donuts could create another kind of uproar, especially if people have been standing in a long line dreaming of crullers and chocolate glazed donuts. Uproar comes from the German Aufruhr, "a stirring up."