San Francisco, Nov 14 : Newer Echo and Echo Dot speakers can now 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, reports The Verge. You can enable or disable this feature in the Alexa app, where you can also set up occupancy routines to use this new capability to do things like turn on lights when you enter a room and then off again when the room is empty. You could also have Alexa play music or a radio station when motion is detected near an Echo device during a set time and then shut down the tunes once you have left. The function is listed under Motion Detection in the Alexa app settings for each compatible Echo device, and here you can toggle the capability on or off. 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 do not 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. /IANS