In this project, ultrasound around 24kHz was used to detect movement near an
object. Waving a hand or other solid object near the source of the ultrasound
(speaker) causes a shift in the frequency of the sound, which is then detected
by a microphone. We detected characteristic shifts in frequency to determine
whether motion was towards (push) or away from (pull) the microphone. Two modes
of visual indication were used to display the results of the motion detection:
blinking LEDs and a computer display. With the blinking LEDs, a different color
LED would light up according to the direction of motion detected. In the
computer animation, the waveform would be displayed on screen along with
markings of which parts are pulls and pushes. Sections of the waveform that
represent different motions would be marked as push or pull.
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