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What is Ultrasound?
Ultrasound is the term used to refer to sound which the human ear cannot detect. The actual limit varies between individuals (and there is evidence to suggest it varies according to age, too), but in general the frequency at which ultrasound begins is generally regarded as 20 KHz. Below this frequency, sound can be heard by the human ear and is referred to as infrasound.
Ultrasound technology uses a piece of equipment called a transducer to view a target organ or life form (such as a human fetus). The transducer emits sound, and detects echoes which are then used by a computer to build up a picture of the target under examination. There are no known harmful effects of ultrasound technology, making it ideal for use during pregnancy as it cannot harm the health of a fetus.
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Medical Uses of Ultrasound
Ultrasound technology can be used in many other ways in addition to its most widely known use to collect information about a fetus during pregnancy. Depending on the dosage and frequency used, ultrasound can be used in a variety of ways to treat diseases and improve health.
- Detect abnormalities in other parts of the body, such as tissues and organs.
- Treat tumors using a process called focused ultrasound surgery, which uses high intensity ultrasound at a specific frequency.
- Penetrate the blood-brain barrier and deliver chemotherapy drugs to brain cells for the treatment of cancer.
- Treating cataracts, administering physiotherapy, and cleaning teeth.
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Industrial and Commercial Uses
In industry, ultrasonic testing is routinely employed as a type of nondestructive testing to find flaws in objects and materials, or to measure their thickness. Generally these use a frequency of between two and ten MHz. Automated ultrasound examination is a technology used in most modern manufacturing processes, as a wide variety of materials can be examined, including plastics, metals, composites, wood, and concrete.
For the consumer, two pieces of equipment employ ultrasound technology: ultrasonic cleaners (typically used for jewelry, watches, and similar items), and ultrasonic humidifiers. Both of these items have industrial and commercial uses in addition to being available to consumers.
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Ultrasound in Animals
Many types of animals—including bats, dogs, moths, dolphins, whales, and some species of fish—can hear sound at much higher frequencies than humans can detect, and thus we refer to them as being able to detect ultrasound. Many animals which can detect ultrasound use these higher frequency sounds as hunting tools. Whales, for example, use ultrasound as a navigation aid (they are, in fact, thought to have their own natural sonar system), and as a tool when hunting.
Bats also use ultrasonic techniques to detect prey, by emitting high-frequency sounds and using echoes to detect the location of the prey animal. Interestingly enough, there is evidence that the ultrasonic frequencies emitted by bats trigger evasive maneuvers in moths, many species of which are preyed upon by bats.