## Essential University Physics: Volume 1 (3rd Edition)

We know that the human ear's hearing range is 20 Hz -20 KHz. Ultra sound frequencies are $10^7$ Hz . The difference between these two frequencies is $10^7Hz-20KHz=0.998\times 10^3Hz$. Thus, these ultra sound frequencies are very high as compared to the human ear range. Ultra sound is a sound having all the physical properties of sound but the only difference is that the human ear cannot hear it.