A sonogram, or an ultrasonography, is an ultrasound-based imaging method generally used in medical practices to visualize bodies that lie beneath a patient’s skin, including tendons, muscles, vessels, internal organs, and fetuses. When used to monitor a pregnancy, the technique is generally referred to as obstetric sonography.

“Ultrasound,” in physics, implies an acoustic energy with a frequency above the range of human hearing. In other words, humans can audibly hear anything within the range of 20 hertz to 20 kilohertz. Ultrasound frequency is higher than 20 kilohertz.