how do you make a ultrasonic radar to use on a computer????
You're going to hack into a computer using ultrasonic radar?
But seriously, you use google. Just google "ultrasonic radar", and you will get lots of how-to hits. If you have questions after reading through those, post a link here with your question.
You could just buy a kit. You may not want to use the word "radar" in the google, though, since it isn't technically radar. But googling "ultrasonic sensor kit buy" yields this inexpensive kit: http://www.hobbyengineering.com/CatSULTRA.html [Broken]
Googling "ultrasonic radar", I found a YouTube that is far too cool:
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