An emergency siren was a noise-making system that produced a penetrating warning sound. Such devices were installed on many facilities and could be activated to give the order to evacuate the premises. During the height of the Galactic Empire, an emergency siren was used at the Imperial Palace on Coruscant to draw attention to the presence of an intruder in the security perimeter.
Many starships were also equipped with such sirens, including the Hammerhead-class cruisers that served with the Galactic Republic Navy during the Jedi Civil War and the modern-day CR90 corvettes. In these cases, sirens were used to indicate damage and other dangerous situation such as entering combat.