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Definition: ultrasound from The Penguin Dictionary of Science

Sound pressure waves of higher frequency than the upper limit of human hearing (i.e. greater than about 20 kHz). Ultrasound is often used where light is unable to penetrate but X-rays would be harmful, for example in the imaging of foetuses.


ultrasound

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
Pressure waves, known as ultrasonic waves, similar in nature to sound waves but occurring at frequencies above 20,000 Hz (cycles per second), the approximate upper limit of human hearing (15–16 Hz is the lower limit). Ultrasonics is concerned with the study and practical application of these phenomena. Some animals, such as dogs and bats, and insects are able to detect ultrasonic waves. Bats, as well as detecting ultrasonic waves, also emit them. Sound waves reflected from objects allow the bat to estimate the distance of objects, from the time taken for the echo to return. Ultrasound can also be used for cleaning. A material is immersed in water through which ultrasonic waves are passed. The high-frequency vibrations cause dirt particles to be removed. Another use of ultrasound is in developing emulsion-based products in the cosmetics and healthcare industries. High-frequency sounds used in a mixture of oil and water form cavitations (formation of large bubbles). This helps the oil to…
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From The Conversation: An Independent Source of Analysis from Academic Researchers
Editor’s note: Government and academic investigators continue to probe reports from Cuba that, starting in 2016 and continuing through 2017, U.S. and Canadian diplomats and tourists may have been subjected to a “sonic weapon,” damaging their hearing, causing nausea, speech problems and potentially…
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Full text Article Ultrasound

From Encyclopedia of Women's Health
Ultrasound is a specialized diagnostic procedure which allows clinicians to visualize internal body parts or structures. What is the science behind this fascinating tool? Just as a violin string vibrates to produce sound, a solid ceramic “crystal” inside a protected casing (the probe) is set to…
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Full text Article Ultrasound

From Gale Encyclopedia of Medicine
Medical ultrasound is an imaging technology that uses high frequency sound waves to capture images of internal body structures and organ systems and display them on a monitor. The ultrasound procedure is painless, safe, and noninvasive. Ultrasound images allow physicians to see dynamic images in…
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Full text Article ultrasound

From Library of Health and Living: The Encyclopedia of Men's Health
A diagnostic imaging procedure that uses high-frequency sound waves to project images of internal organs and structures. Ultrasound is most effective for examining organs and structures that are hollow or soft. In combination with the Doppler effect, ultrasound is useful for determining the flow…
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Full text Article Ultrasound

From Harvard Medical School Health Topics A-Z
Ultrasound
What Is It? Ultrasound scanning, also called sonography, is a technique used to see tissues and organs inside the body. It uses high-frequency sound waves, which cannot be heard by humans, to produce images of structures inside the body. The process is very similar to the way sonar is used by…
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Full text Article Ultrasound

From New Harvard Guide to Women's Health, The
Ultrasound is a diagnostic procedure in which high-frequency sound waves are bounced off certain internal structures of the body. The reflections or echoes of these sound waves are then recorded on a video screen to form a picture, or sonogram, of the internal structure (see illustration). In…
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Full text Article ultrasound

From The American Heritage Student Science Dictionary
ultrasound
Sound waves that have frequencies higher than 20,000 hertz, which are too high for humans to hear. The medical use of ultrasound waves to produce images of the inside of the body or to provide deep heat or vibration to a specific region of the body. — Adjective ultrasonic (ŭl′trə-sŏn′ĭk). ultrasound…
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Full text Article Ultrasound

From Black's Medical Dictionary, 43rd Edition
A technique using very-high-frequency sound waves above 20,000 Hz that the human ear cannot hear. Ultrasound is widely used for diagnosis and also for some treatments. In OBSTETRICS , ultrasound can assess the stage of pregnancy and detect abnormalities in the FETUS (see below). It is a valuable…
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Full text Article ultrasound

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
Pressure waves, known as ultrasonic waves, similar in nature to sound waves but occurring at frequencies above 20,000 Hz (cycles per second), the approximate upper limit of human hearing (15–16 Hz is the lower limit). Ultrasonics is concerned with the study and practical application of these…
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Full text Article Ultrasound

From Black's Veterinary Dictionary
Sound at a frequency above 20,000 cycles per second. Propagated by applying an electric current to one side of a piezoelectric crystal, which deforms and produces a sound wave. Ultrasound is generally defined as an auditory frequency beyond that perceived by the human ear. Most humans hear and emit…
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