Ultrasound facts for kids
Ultrasound is a special kind of sound. It has a very high frequency, so high that human ears cannot hear it. The highest sound frequency most people can hear is about 20,000 hertz (or 20 kilohertz). Ultrasound sounds are even higher than that.
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How Animals Hear Ultrasound
Some animals can hear sounds that humans cannot. These animals include dogs, dolphins, bats, and mice. They can hear ultrasound because their ears are made to pick up these very high frequencies.
As people get older, their ability to hear high-pitched sounds usually decreases. This means children can often hear some high sounds that older adults cannot. Our middle ear helps us hear sounds. It acts like a filter, stopping very high frequencies from reaching the inner ear. However, if ultrasound goes directly to the inner ear (called the cochlea) without passing through the middle ear, people can sometimes hear much higher frequencies, up to 200,000 hertz! This is sometimes called "ultrasonic hearing." Divers first noticed this effect when they were near a high-frequency sonar signal.
Medical Uses of Ultrasound
One common use for ultrasound is in medical ultrasonography, especially during pregnancy. Doctors use it to see inside the body without needing to cut it open. It is considered a very safe test. This is because it does not use harmful ionizing radiation, unlike x-rays or CAT scanning. Ultrasound helps doctors check on babies growing in the womb and look at other parts of the body.
How Ultrasonic Cleaners Work
Ultrasonic cleaners are machines that use ultrasound to clean things. They are sometimes called "supersonic cleaners" by mistake. These cleaners use ultrasound frequencies between 20,000 and 40,000 hertz. They are used to clean many items like jewellery, lenses, watches, and dental instruments.
An ultrasonic cleaner works by creating millions of tiny bubbles in a liquid. These bubbles are so small they are microscopic. When these bubbles collapse near a dirty surface, they release energy. This energy creates small jets of liquid that blast away dirt and grime. It's a very effective way to clean delicate or hard-to-reach areas.
Images for kids
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An ultrasonic examination
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The Galton whistle, one of the first devices to produce ultrasound
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Bats use ultrasounds to navigate in the darkness.
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A dog whistle, which makes sounds in the ultrasonic range, used to train dogs and other animals
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Non-destructive testing of a swing shaft showing spline cracking
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A diagram of ultrasonic liquid processors used in industry
See also
In Spanish: Ultrasonido para niños
