Ultrasound consists of sound at frequencies

So we want to know from which frequencies does ultrasound consist of. Sound, which human ear can hear is in the frequency range from 20 to 20000 Hz. Frequencies under 20 Hz are called infrasound and frequencies above 20000 Hz or 20 kHz are called ultrasound. 

Electoral current force mechanical advantage if the wheel and axle is 2 n and the output force is 20 n