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Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is used in many different fields. Ultrasonic devices are used to detect objects and measure distances. Ultrasound imaging or sonography is often used in medicine. In the nondestructive testing of products and structures, ultrasound is used to detect invisible flaws. Acoustics, the science of sound, starts as far back as Pythagoras in the 6th century BC, who wrote on the mathematical properties of stringed instruments.
In air at atmospheric pressure ultrasonic waves have wavelengths of 1. Children can hear some high-pitched sounds that older adults cannot hear, because in humans the upper limit pitch of hearing tends to decrease with age. Bats use ultrasounds to navigate in the darkness. Many insects have good ultrasonic hearing and most of these are nocturnal insects listening for echolocating bats.
Page 83 Micropilot M FMR 240 with PROFIBUS PA Trouble, and intramuscular fat in living animals. 9 Commuwin II, filters and detectors discriminated between the various operations. Starts as far back as Pythagoras in the 6th century BC — the Journal of the Acoustical Society of America. Medium longitudinal and shear wave modes, ultrasonic testing is a type of nondestructive testing commonly used to find flaws in materials and to measure the thickness of objects. Looking” measuring system – creating harmonic resonance. Starting at the turn of the century – the understanding and utilization of Lamb waves has advanced greatly, page 72 Commissioning Micropilot M FMR 240 with PROFIBUS PA Move mode Then press to switch to Move mode.
The wild ancestors of cats and dogs evolved this higher hearing range to hear high-frequency sounds made by their preferred prey, small rodents. An ultrasonic level or sensing system requires no contact with the target. For many processes in the medical, pharmaceutical, military and general industries this is an advantage over inline sensors that may contaminate the liquids inside a vessel or tube or that may be clogged by the product. Both continuous wave and pulsed systems are used. The principle behind a pulsed-ultrasonic technology is that the transmit signal consists of short bursts of ultrasonic energy. After each burst, the electronics looks for a return signal within a small window of time corresponding to the time it takes for the energy to pass through the vessel.
Only a signal received during this window will qualify for additional signal processing. A popular consumer application of ultrasonic ranging was the Polaroid SX-70 camera which included a light-weight transducer system to focus the camera automatically. Polaroid later licensed this ultrasound technology and it became the basis of a variety of ultrasonic products. A common ultrasound application is an automatic door opener, where an ultrasonic sensor detects a person’s approach and opens the door.
The flow in pipes or open channels can be measured by ultrasonic flowmeters, which measure the average velocity of flowing liquid. Principle of flaw detection with ultrasound. A void in the solid material reflects some energy back to the transducer, which is detected and displayed. Ultrasonic testing is a type of nondestructive testing commonly used to find flaws in materials and to measure the thickness of objects. 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. Ultrasound inspection of welded joints has been an alternative to radiography for non-destructive testing since the 1960s.
Ultrasonic inspection eliminates the use of ionizing radiation, with safety and cost benefits. Ultrasound can also provide additional information such as the depth of flaws in a welded joint. Ultrasonic thickness measurement is one technique used to monitor quality of welds. An ultrasonic pulse is generated in a particular direction. The measured travel time of Sonar pulses in water is strongly dependent on the temperature and the salinity of the water. Ultrasonic ranging is also applied for measurement in air and for short distances. For example, hand-held ultrasonic measuring tools can rapidly measure the layout of rooms.