@candyquilt-- That's an interesting question. I'm sure you're not the only one wondering that. I'm actually not sure. I've never tried it although I'm sure there are people out there who have.
I have a friend who uses ultrasonic transmitter and other electronic devices to identify ultrasonic signals. He has done a lot of research on ultrasonic and electromagnetic signals. He believes that these signals are used for intelligence as well as mind control. He is normally a very logical person. So although all of this sounds a little crazy to me, I don't want to reject his ideas completely. Most people do not use ultrasonic transmitters for these types of things however.