2m is what they demoed if I'm right. The power attenuation actually varies a lot and is dependent on ultrasound frequency, temperature, humidity, air pressure..

2m is what they demoed if I'm right. The power attenuation actually varies a lot and is dependent on ultrasound frequency, temperature, humidity, air pressure... You get better transmission at low frequencies, but below 100kHz you risk affecting pets. Some details and a link to an interesting paper: http://physics.stackexchange.com/questions/52195/ultrasonic-wave-through-air http://physics.stackexchange.com/questions/52195/ultrasonic-...