Ultrasonic (adjective, “Uhl-truh-SAHN-ick”)
Ultrasonic sounds are those that are too high-pitched for humans to hear. This includes all sound waves with frequencies above about 20,000 hertz. That is, sound waves that wiggle back and forth more than 20,000 times per second.
Humans may not be able to hear ultrasonic sounds, or ultrasound. But other animals can. Dogs can hear sounds up to about 45,000 hertz. Some bats and whales have been reported to hear sounds up to about 200,000 hertz.
Both bats and whales can use such ultrasonic sounds for echolocation. The animals produce sound waves that bounce off surrounding objects. By listening to the sound waves that come back, bats and whales can navigate and find prey in the dark.
Doctors use ultrasonic waves in a similar way to image the insides of people’s bodies. Ultrasound probes send harmless ultrasonic waves into the body. Different tissues then reflect those sound waves differently. By capturing the echoes, an ultrasound machine can help a doctor spot heart defects or tumors. Ultrasound machines can even take images of fetuses during pregnancy.
Sonar technology likewise uses ultrasonic waves to map the seafloor.
In a sentence
When dehydrated or snipped, some plants make ultrasonic clicks.
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