What is signified by two-tone chimes indicating "ding dong, ding dong, ding dong"?

The two-tone chimes indicating "ding dong, ding dong, ding dong" specifically signify emergency communication from the flight deck. This sound pattern is a distinct and urgent signal that alerts crew members to a situation requiring immediate attention and action. It is designed to ensure that flight attendants are aware of the seriousness of the communication, allowing for swift and efficient response procedures.

This sound is differentiated from routine announcements, which typically use a single chime, and general passenger alerts, usually indicated by different tones or signals. The specific sequence of the two-tone chime serves to convey the urgency of the message being communicated from the flight deck to the cabin crew, underscoring the need for preparedness in case of an emergency.