Wherever you are this afternoon, you’re probably going to hear a familiar high-pitched buzz. Don’t worry, it’s just a test.

The Federal Emergency Management Agency (FEMA) is coordinating with the Federal Communications Commission (FCC) to conduct a test of two emergency alert systems. The test will occur nationwide beginning at 2:20 p.m. ET (11:20 a.m. PT). In the event the test is canceled, it will be rescheduled for August 25.

The emergency alerts played on television and radios will be issued by the Emergency Alert System (EAS). The EAS is tested monthly by states, so you’ll probably recognize the high-pitched buzzing tone. FEMA is required to conduct a nationwide test of the EAS every three years.

The EAS test will briefly interrupt the scheduled programming on television and radios. The alert tone will be followed by the EAS test message. The message will be delivered in English or Spanish depending on device settings.

The second system being tested is Wireless Emergency Alerts (WEA). WEA issues four types of alerts: Those issued by the President of the United States, alerts about imminent threats to safety or life, AMBER Alerts involving missing children, and alerts with recommendations for saving lives and property in emergency situations.

WEA will send an alert to phones on which the subscriber has opted to receive test messages. Most devices won’t receive a test message, but there’s no need to worry — compatible devices will receive real emergency alerts. If you don’t want to receive WEA alerts, you can opt out on most devices by following our guide, though that may not be the wisest choice in these troubled times.