Sydney emergency system to be tested

Sydney residents are being warned not to be alarmed as authorities carry out the CBD's monthly emergency warning system test.

Officers will test some of the 98 speakers throughout the city, which display 13 variable messages, about 12.15pm on Thursday.

"Members of the public should not be concerned. This is a test only," police said.

"Those who reside, work or travel through the Sydney CBD need to be aware of the warning system, what it sounds like and what it is used for."