History and Definition of Ultrasound
- Acoustics dates back to Pythagoras in the 6th century BC
- Lazzaro Spallanzani discovered echolocation in bats in 1794
- Francis Galton invented the Galton whistle in 1893
- Chilowski proposed submarine detection during World War I
- Paul Langevin built an ultrasound transducer using the piezoelectric effect
- Ultrasound is sound with frequencies greater than 20kHz
- Ultrasound can be generated at very high frequencies, up to multiple hundreds of kilohertz
- Medical imaging equipment uses frequencies in the MHz range
- UHF ultrasound waves have been generated in the gigahertz range
- Extremely high-frequency ultrasound poses challenges due to wave steepening and shock waves

Perception of Ultrasound
- Humans have an upper frequency limit of approximately 20kHz
- Children can hear higher-pitched sounds than older adults
- Some cell phone signals are designed to be audible only to younger humans
- Bats use ultrasounds for navigation and prey detection
- Dogs, cats, and toothed whales can hear ultrasound

Ultrasound in Animals
- Bats can detect frequencies beyond 100kHz, possibly up to 200kHz
- Nocturnal insects listen for echolocating bats
- Moths and tiger moths have defense mechanisms against bats
- Dogs and cats have a hearing range that extends into ultrasound
- Porpoises have the highest known upper hearing limit at around 160kHz

Applications of Ultrasound
- Ultrasonic sensors can be used for non-contact sensing
- Pulsed-ultrasonic technology is used for level or sensing systems
- Ultrasonic sensors are used in motion sensors and flow measurement
- Polaroid SX-70 camera used ultrasonic technology for focusing
- Ultrasonic sensors can be used for automatic door openers and intruder detection
- Ultrasonic testing is commonly used to find flaws in materials and measure object thickness
- Frequencies of 2 to 10MHz are common in ultrasonic testing
- Ultrasonic range finding is used for shorter distances and finer accuracy
- Ultrasonic imaging uses frequencies of 2 megahertz and higher
- Acoustic microscopy uses sound waves to visualize structures too small to be resolved by the human eye
- Medical ultrasound is a diagnostic imaging technique used to visualize muscles, tendons, and internal organs
- Diagnostic ultrasound is used externally and internally in veterinary medicine
- High-power ultrasound frequencies range from 20kHz to a few hundred kHz
- Ultrasonic impact treatment enhances the mechanical and physical properties of metals
- Ultrasonication improves mixing and chemical reactions in various applications and industries
- Ultrasonic standing waves can trap and orient particles in equidistant planes
- Ultrasonic cleaners are used for cleaning jewelry, lenses, watches, dental instruments, and industrial parts
- High-power ultrasound can disintegrate biological cells, including bacteria
- Ultrasonic humidifiers are a type of nebulizer that creates a fine spray

Processing and Power of Ultrasound
- Intensities above 10 watts per square centimeter can induce cavitation in liquid media
- Some applications use up to 1000 watts per square centimeter
- Ultrasonic treatment can break up stony deposits, increase skin permeability, and assist in drug effectiveness
- Ultrasonic impact treatment results in controlled residual compressive stress, grain refinement, and grain size reduction
- Ultrasonication generates alternating low-pressure and high-pressure waves in liquids, causing cavitation
- Ultrasonic manipulation and characterization of particles have applications in various fields
- Ultrasonic disintegration has uses in biological science, analytical chemistry, and ethanol production
- Ultrasonic disintegration can enhance liquefaction and saccharification in corn milling plants

Ultrasound (Wikipedia)

For the application to medicine, see Medical ultrasound. For other uses, see Ultrasound (disambiguation) and Ultrasonic (disambiguation).

Not to be confused with Supersonic.

Ultrasound is sound with frequencies greater than 20 kilohertz. This frequency is the approximate upper audible limit of human hearing in healthy young adults. The physical principles of acoustic waves apply to any frequency range, including ultrasound. Ultrasonic devices operate with frequencies from 20 kHz up to several gigahertz.

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. Industrially, ultrasound is used for cleaning, mixing, and accelerating chemical processes. Animals such as bats and porpoises use ultrasound for locating prey and obstacles.