Ultrasound is used in many different fields. Ultrasonic devices are used to detect objects and arthritis ultrasound imaging distances.
Industrially, ultrasound is used for cleaning, mixing, and to accelerate chemical processes. 1794, when he demonstrated that bats hunted and navigated by inaudible sound and not vision. 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.
The wild ancestors of cats and dogs evolved this higher hearing range to hear high-frequency sounds made by their preferred prey, small rodents. Several types of fish can detect ultrasound. 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. 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. 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. 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 inspection has progressed from manual methods to computerized systems that automate much of the process. An ultrasonic test of a joint can identify the existence of flaws, measure their size, and identify their location. An ultrasonic pulse is generated in a particular direction. By measuring the difference in time between the pulse being transmitted and the echo being received, it is possible to determine the distance. 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. Ultrasonic measurements may be limited through barrier layers with large salinity, temperature or vortex differentials. The potential for ultrasonic imaging of objects, with a 3 GHZ sound wave producing resolution comparable to an optical image, was recognized by Sokolov in 1939 but techniques of the time produced relatively low-contrast images with poor sensitivity. The power density is generally less than 1 watt per square centimetre, to avoid heating and cavitation effects in the object under examination.