Virtual Microphones: Using Ultrasonic Sound to Receive Audio Waves
A highly focussed ultrasound beam was sent through the room. At a distance of several meters the ultrasonic wave was received again with an ultrasonic microphone. The wave field of a common audio source was overlaid with the ultrasonic beam. It was found, that the phase shift of the received ultrasonic signal obtains the audio information of the overlaid field. So the ultrasonic beam itself acts as sound receiver, there is no technical device like membranes necessary at direct vicinity of sound reception. Because this kind of sound receiver is not visible or touchable we call it "Virtual Microphone".
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