I am not a physicist but I am extremely interested in this area.
The simple version of my question is:
"What is the maximum range of an ultrasonic wave traveling through air?" Now, I know it depends on the exact frequency, air temperature, humidity, ... I don't need to know exact number. I just need to know the order of magnitude. Is it ~1m? ~10m? ~1000m?
I also know that this range is finite due to wave's attenuation and attenuation is higher as frequency is higher. So this question could possibly be translated into these two: "What is the minimum ultrasonic wave amplitude detectable by a commercially available sensor?" + "What is the maximum ultrasonic wave amplitude that can be emitted by commercially available ultrasound emitter?"