4. The frequency of ultrasound wave is typically A.Above 20 kHz B.Above 20,000 kHz C.Below 20 kHz D.Below 02 kHz
Option A Solution: Ultrasound refers to a sound wave with a frequency greater than the upper limit of human hearing, which is generally over 20 kHz. In general, humans can hear sounds with a frequency between 20 Hz and 20 kHz.
A). above 20Khz
