Information AboutUltrasound |
| CATEGORIES ABOUT ULTRASOUND | |
| hearing | |
| acoustics | |
| ultrasound | |
| medical physics | |
| medical ultrasoundhearing | |
| acoustics | |
| ultrasound | |
| medical physics | |
| medical ultrasound | |
| acoustics | |
| sound | |
| medical physics | |
For information on the dance band The Ultrasonics, see The Ultrasonics Ultrasound is Sound with a Frequency greater than the upper limit of human hearing, this limit being approximately 20 Kilohertz (20,000 hertz). Some animals, such as Dog s, Dolphins , Bat s, and Mice have an upper limit that is greater than that of the human Ear and thus can hear ultrasound. Children can hear some high-pitched sounds that older adults cannot hear, as in humans the upper limit pitch of hearing gets lower with age. This frequency limit is caused by the Middle Ear that acts as a Low-pass Filter . If ultrasound is coupled directly into the skull bone and reaches the Cochlea without passing through the middle-ear, much higher frequencies (up to about 200 kHz) will be audible. This effect (sometimes called ultrasonic hearing) was first discovered by divers exposed to a high-frequency (ca. 50 kHz) Sonar signal. MEDICAL SONOGRAPHY See Also: Medical ultrasonography Medical ultrasonography ('''sonography''') is an ultrasound-based diagnostic Imaging technique used to visualize muscles and internal organs, their size, structure and any pathological Lesion s, making them useful for scanning the organs. Obstetric Sonography is commonly used during Pregnancy . OTHER MEDICAL USES Ultrasound also has therapeutic applications:-
INDUSTRIAL ULTRASOUND Ultrasound is also used in industry for locating flaws in materials. Frequencies of 2 to 10 MHz are common but for special purposes other frequencies are used. Inspection may be manual or automated and is an essential part of modern manufacturing processes. Most metals can be inspected as well as plastics and aerospace composites. See Also: Ultrasound flow meter ULTRASONIC CLEANING Ultrasonic Cleaner s, sometimes mistakenly called '' Supersonic cleaners'', are used at frequencies from 20-40 KHz for Jewellery , Lenses and other optical parts, Watch es, Dental Instrument s, Surgical Instrument s and Industrial parts. The main mechanism for cleaning action in an ultrasonic cleaner is the energy released from the collapse of millions of microscopic Cavitation events occurring near the dirty surface. The bubbles formed by Cavitation colapse through themselves forming tiny jets directed at the surface. Home cleaners are available and costs range from approximately US $60. SCARING RODENTS AWAY Ultrasound generator/speaker systems are sold with claims that they frighten away rodents and insects, but there is no scientific evidence that the devices work; controlled tests have shown that rodents quickly learn that the speakers are harmless. However, the pitch used is well within the audible range of most children, and can cause headaches. There is sufficient evidence however, to show that ultrasound in the range that is emitted by Bat s has a definite effect on the direction chosen by Moth s to fly, as bats eat moths. SONOCHEMISTRY See Also: Sonochemistry Power ultrasound in the 20-100 kHz range is used in Chemistry . The ultrasound does not interact directly with Molecules to induce the chemical change as its typical wavelength is too long compared to the size of molecules. Instead, Cavitation causes local extremes of temperature and pressure in the liquid in which the reaction is performed. In addition, it also breaks up solids and removes passivating layers of Inert material to give a larger Surface Area for the reaction to occur over. Both these factors lead to a general increase in the Rate Of Reaction when ultrasound is used compared to when it is not. ULTRASONIC DISINTEGRATION Some sorts of ultrasound can disintegrate biological cells including Bacteria . This has uses in Biological science and in killing bacteria in Sewage . See for example:-
ULTRASOUND AS A WEAPON See Also: Ultrasound weapons OTHER USES Ultrasound when applied in specific configurations can produce exotic phenomena such as Sonoluminescence . These phenomena are being investigated partly because of the possibility of Bubble Fusion (a nuclear fusion reaction hypothesized to occur during sonoluminescence). A common use of Ultrasound is in range finding. The basic principle is that an ultrasonic pulse is generated in a particular direction. If there is an object in the path of this pulse, part or all of the pulse will be reflected back to the sender as an Echo and can be detected. By measuring the difference in time between the pulse being transmitted and the echo being received, it is possible to determine how far away the object is. Bats use a variety of ultrasonic ranging (echolocation) to detect their prey. Sonar is another form. SEE ALSO
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