Galileo, an Italian astronomer and physicist, was the greatest contributor to our understanding of sound. He demonstrated that the frequency of sound waves determined the pitch. This was done by scraping a chisel across a brass plate producing a screech. Galileo then related the spacing of the grooves induced by the chisel to the pitch of the screech.
Many transducers can convert ultrasonic waves into electric waves.
They give off strong echoes that create stronger electric pulses than weak ones do. A special computer registers the data that the pulses and echoes give off. Then the computer can give information on the substances that reflected the ultrasonic waves. Air that is passed through the vocal cords causes them to vibrate. Longitudinal vibration of the vocal chords makes surrounding air vibrate.