alarm-bell
Emergency ringing signal
An alarm-bell is a bell rung to warn of danger—fire, invasion, or emergency.
The figurative use dominates: alarm bells are mental warnings that something is wrong.
Alarm bells went off when he asked for my password.
If something rings alarm bells or sets off alarm bells, it triggers suspicion or concern.
siren
Wailing alert device
threat · hazard · emergency · urgency · caution · distress · signal · indicator · foreboding · premonition
clanging
Resonant metallic sounding
chiming · resonant · piercing · shrill · loud · blaring · deafening · clangorous · reverberating · jangling
alarm-bellall-clear
Signal danger has passed
reassurance · green light · thumbs-up · stand-down · everything's fine
alarm, bell, alarmed, alarming, doorbell, alarms, unalarmed, bellman, alarum