People in San Luis Obispo County may hear emergency warning sirens this week.
Tuesday and Wednesday's low-volume growl tests are part of a test of the Early Warning System (EWS).
There are 131 EWS sirens located throughout San Luis Obispo County.
They were installed as one of the requirements related to the operation of the Diablo Canyon Power Plant, but they can be used for any type of emergency.
If you hear the sirens sound outside of a scheduled test, you're advised to tune to a local television or radio station for information about the Emergency Alert System activation.