Starting this week, newer Echo and Echo Dot speakers can use ultrasound to detect occupancy in your home and turn on and off other connected devices such as lights or your Fire TV. First mentioned at Amazon’s fall hardware event in September, the Echo and Echo Dot fourth-gen speakers can now emit an “inaudible ultrasound wave” to detect if there are people present in a room. This feature is similar to the motion-sensing newer Echo Show devices have, but those rely on their cameras to tell if there are people in the room. The Echo speakers don’t have cameras, so instead, the device detects movement by emitting an inaudible ultrasound wave that reflects off nearby objects before traveling back to the device’s microphones. Google also uses ultrasound in its Nest smart displays and Nest Mini speakers to detect how close a person is to the display or speaker and offer up different interfaces.

Source: The Nation November 13, 2021 00:51 UTC