Ultrasound (noun, “UHL-tra-sound”)
Sound travels from one place to the next in waves. The frequency of the wave determines what you hear. But once that frequency is too high for a person to hear, it’s a special type of sound: ultrasound.
It is more common, though, to see the term “ultrasound” in medicine. When a doctor wants to see what’s going on inside a patient, one option is ultrasound. She can use a device that will send these ultra-high frequency sound waves into the patient’s body. The sound waves bounce off whatever is inside. The machine reads the echoes of those waves as they come out of the body. Then it uses those echoes to create an image of anything inside, such as internal organs, a tumor or a baby.
In a sentence
Bats use ultrasound to echolocate when they are hunting.
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