What Is Presence Detection?
Some Echo devices can detect presence in a room with ultrasound technology.
Occupancy Routines, and some Alexa features, rely on Presence Detection to determine whether a room is occupied. When you turn on an Occupancy Routine or a feature that uses Presence Detection is enabled, whether by default or your action, some Echo devices emit ultrasound and use the device microphones to detect presence near the device. Alexa interprets such motion to mean that someone might be in the room.
Presence Detection is designed to detect major motion such as walking around the room. Some devices detect minor motion, such as waving your hand, or sitting still and reading. A routine can also start when no occupancy is detected, for example, to turn off lights when the room is empty.
The devices don't emit ultrasound unless a feature that uses Presence Detection is turned on, whether by default or your action, such as Occupancy Routines. Humans can't hear or perceive ultrasound.
