The apocalypse. An air raid siren. An alien invasion. A giant mosquito buzzing in the ear.

These were just some of the ways residents of inner Sydney described the noise that woke them about 2am on Monday.

The sustained droning sound that could be heard across a 10-kilometre radius for 16 long minutes was coming from a malfunctioning horn on a train at the Eveleigh rail yards next to Redfern station.

Angry and confused residents piled out onto the streets of Chippendale, Redfern, Ultimo, Surry Hills and Glebe when the horn started to sound.

"It sounded like a car alarm going off inside my ear," said Redfern resident Celia Finch. "There was no way anyone could sleep with that going off."