Editing Ultrasound (section)

==Processing and power==
High-power applications of ultrasound often use frequencies between 20&nbsp;kHz and a few hundred kHz. Intensities can be very high; above 10 watts per square centimeter, cavitation can be inducted in liquid media, and some applications use up to 1000 watts per square centimeter.  Such high intensities can induce chemical changes or produce significant effects by direct mechanical action, and can inactivate harmful microorganisms.<ref name=Betts00>{{cite book | vauthors = Betts GD, Williams A, Oakley RM | chapter = Inactivation of Food-borne Microorganisms using Power Ultrasound | veditors = Robinson RK, Batt CA, Patel PD | title = Encyclopedia of Food Microbiology | publisher = Academic Press | date = 2000 | isbn = 978-0-12-227070-3 | page = 2202 }}</ref>

===Physical therapy===
{{main|Therapeutic ultrasound}}
Ultrasound has been used since the 1940s by physical and occupational therapists for treating [[connective tissue]]: [[ligament]]s, [[tendon]]s, and [[fascia]] (and also [[Granulation tissue|scar tissue]]).<ref>{{cite web | url = http://www.electrotherapy.org/electro/downloads/Therapeutic%20Ultrasound.pdf | vauthors = Watson T | date = 2006 | title = Therapeutic Ultrasound | archive-url = https://web.archive.org/web/20070412093629/http://www.electrotherapy.org/electro/downloads/Therapeutic%20Ultrasound.pdf | archive-date = 2007-04-12 }} for a pdf version with the author and date information)</ref> Conditions for which ultrasound may be used for treatment include the follow examples: ligament [[sprain]]s, muscle [[strain (injury)|strains]], [[tendonitis]], joint inflammation, [[plantar fasciitis]], [[metatarsalgia]], facet irritation, [[impingement syndrome]], [[bursitis]], [[rheumatoid arthritis]], [[osteoarthritis]], and scar tissue adhesion.

Relatively high power ultrasound can break up stony deposits or tissue, increase [[skin permeability]], accelerate the effect of drugs in a targeted area, assist in the measurement of the elastic properties of tissue, and can be used to sort cells or small particles for research.<ref>{{cite book |last1=Repacholi |first1=Michael H. |last2=Benwell |first2=Deirdre A. |title=Essentials of Medical Ultrasound |date=1982 |publisher=3Island Press |isbn=978-1-4612-5806-3 }}{{pn|date=July 2024}}</ref>

===Ultrasonic impact treatment===
[[Ultrasonic impact treatment]] (UIT) uses ultrasound to enhance the mechanical and physical properties of metals.<ref>{{cite journal |last1=Statnikov |first1=Efim Sh. |last2=Korolkov |first2=Oleg V. |last3=Vityazev |first3=Vladimir N. |title=Physics and mechanism of ultrasonic impact |journal=Ultrasonics |date=December 2006 |volume=44 |pages=e533–e538 |doi=10.1016/j.ultras.2006.05.119 |pmid=16808946 }}</ref> It is a metallurgical processing technique in which ultrasonic energy is applied to a metal object. Ultrasonic treatment can result in controlled residual compressive stress, grain refinement and grain size reduction. Low and high cycle fatigue are enhanced and have been documented to provide increases up to ten times greater than non-UIT specimens. Additionally, UIT has proven effective in addressing [[stress corrosion cracking]], [[corrosion fatigue]] and related issues.

When the UIT tool, made up of the ultrasonic transducer, pins and other components, comes into contact with the work piece it acoustically couples with the work piece, creating harmonic resonance.<ref>{{cite web|title=UIT Solutions Video|url=http://www.appliedultrasonics.com/solutions_video.html|work=appliedultrasonics.com|access-date=28 September 2012|archive-url=https://web.archive.org/web/20120510085911/http://www.appliedultrasonics.com/solutions_video.html|archive-date=2012-05-10|url-status=live}}</ref> This harmonic resonance is performed at a carefully calibrated frequency, to which metals respond very favorably.

Depending on the desired effects of treatment a combination of different frequencies and displacement amplitude is applied. These frequencies range between 25 and 55&nbsp;kHz,<ref>{{cite web |title=Tools of the Trade |url=http://appliedultrasonics.com/solutions.html|work=appliedultrasonics.com|access-date=28 September 2012|archive-url=https://web.archive.org/web/20080531004615/http://www.appliedultrasonics.com/solutions.html|archive-date=2008-05-31|url-status=live}}</ref> with the displacement amplitude of the resonant body of between 22 and 50&nbsp;μm (0.00087 and 0.0020 in).

UIT devices rely on [[magnetostrictive]] transducers.

===Processing===
{{main|Sonication}}
Ultrasonication offers great potential in the processing of liquids and slurries, by improving the mixing and chemical reactions in various applications and industries. Ultrasonication generates alternating low-pressure and high-pressure waves in liquids, leading to the formation and violent collapse of small [[vacuum]] bubbles. This phenomenon is termed [[cavitation]] and causes high speed impinging liquid jets and strong hydrodynamic shear-forces. These effects are used for the deagglomeration and milling of micrometre and nanometre-size materials as well as for the disintegration of cells or the mixing of reactants. In this aspect, ultrasonication is an alternative to high-speed mixers and agitator bead mills. Ultrasonic foils under the moving wire in a paper machine will use the shock waves from the imploding bubbles to distribute the cellulose fibres more uniformly in the produced paper web, which will make a stronger paper with more even surfaces. Furthermore, chemical reactions benefit from the free radicals created by the cavitation as well as from the energy input and the material transfer through boundary layers. For many processes, this sonochemical (see [[sonochemistry]]) effect leads to a substantial reduction in the reaction time, like in the [[transesterification]] of oil into [[biodiesel]].{{Citation needed|date=July 2020}}
[[File:Schematic of bench and industrial-scale ultrasonic liquid processors produced by Industrial Sonomechanics, LLC.jpg|thumbnail|Schematic of bench and industrial-scale ultrasonic liquid processors]]

Substantial ultrasonic intensity and high ultrasonic vibration amplitudes are required for many processing applications, such as nano-crystallization, nano-emulsification,<ref name = "nanoemulsion paper">{{cite journal | vauthors = Peshkovsky AS, Peshkovsky SL, Bystryak S | title = Scalable high-power ultrasonic technology for the production of translucent nanoemulsions. | journal = Chemical Engineering and Processing: Process Intensification | date = July 2013 | volume = 69 | pages = 77–82 | doi = 10.1016/j.cep.2013.02.010 | bibcode = 2013CEPPI..69...77P }}</ref> deagglomeration, extraction, cell disruption, as well as many others. Commonly, a process is first tested on a laboratory scale to prove feasibility and establish some of the required ultrasonic exposure parameters. After this phase is complete, the process is transferred to a pilot (bench) scale for flow-through pre-production optimization and then to an industrial scale for continuous production. During these scale-up steps, it is essential to make sure that all local exposure conditions (ultrasonic amplitude, [[cavitation]] intensity, time spent in the active cavitation zone, etc.) stay the same. If this condition is met, the quality of the final product remains at the optimized level, while the productivity is increased by a predictable "scale-up factor". The productivity increase results from the fact that laboratory, bench and industrial-scale ultrasonic processor systems incorporate progressively larger [[ultrasonic horn]]s, able to generate progressively larger high-intensity cavitation zones and, therefore, to process more material per unit of time. This is called "direct scalability". It is important to point out that increasing the power of the ultrasonic processor alone does ''not'' result in direct scalability, since it may be (and frequently is) accompanied by a reduction in the ultrasonic amplitude and cavitation intensity. During direct scale-up, all processing conditions must be maintained, while the power rating of the equipment is increased in order to enable the operation of a larger ultrasonic horn.<ref name = "horn paper">{{cite journal | vauthors = Peshkovsky SL, Peshkovsky AS | title = Matching a transducer to water at cavitation: acoustic horn design principles | journal = Ultrasonics Sonochemistry | volume = 14 | issue = 3 | pages = 314–22 | date = March 2007 | pmid = 16905351 | doi = 10.1016/j.ultsonch.2006.07.003 | doi-access = free | bibcode = 2007UltS...14..314P }}</ref><ref name = "book section">{{cite book | vauthors = Peshkovsky AS, Peshkovsky SL | chapter = Industrial-scale processing of liquids by high-intensity acoustic cavitation-the underlying theory and ultrasonic equipment design principles | veditors = Nowak FM | title = Sonochemistry: Theory, Reactions and Syntheses, and Applications | location = Hauppauge, NY | publisher = Nova Science Publishers | date = 2010 }}</ref><ref name = "book">{{cite book | vauthors = Peshkovsky AS, Peshkovsky SL | title = Acoustic cavitation theory and equipment design principles for industrial applications of high-intensity ultrasound | location = Hauppauge, NY | publisher = Nova Science Publishers | date = 2010 | series = Physics Research and Technology }}</ref>

===Ultrasonic manipulation and characterization of particles===
A researcher at the Industrial Materials Research Institute, Alessandro Malutta, devised an experiment that demonstrated the trapping action of ultrasonic standing waves on wood pulp fibers diluted in water and their parallel orienting into the equidistant pressure planes.<ref>{{cite journal | vauthors = Dion JL, Malutta A, Cielo P |title=Ultrasonic inspection of fiber suspensions |journal=Journal of the Acoustical Society of America |volume=72 |issue=5 |date = November 1982 |pages=1524–1526 |doi=10.1121/1.388688 |bibcode = 1982ASAJ...72.1524D }}</ref> The time to orient the fibers in equidistant planes is measured with a laser and an electro-optical sensor. This could provide the paper industry a quick on-line fiber size measurement system. A somewhat different implementation was demonstrated at Pennsylvania State University using a microchip which generated a pair of perpendicular standing surface acoustic waves allowing to position particles equidistant to each other on a grid. This experiment, called [[acoustic tweezers]], can be used for applications in material sciences, biology, physics, chemistry and nanotechnology.

===Ultrasonic cleaning===
{{Main|Ultrasonic cleaning}}

[[Ultrasonic cleaner]]s, sometimes mistakenly called ''[[supersonic]] cleaners'', are used at frequencies from 20 to 40 [[Hertz|kHz]] for jewellery, lenses and other optical parts, watches, [[dentistry|dental instrument]]s, [[surgical instrument]]s, [[diving regulator]]s and industrial parts. An ultrasonic cleaner works mostly by energy released from the collapse of millions of microscopic [[cavitation]] bubbles near the dirty surface. The collapsing bubbles form tiny shockwaves that break up and disperse contaminants on the object's surface.

===Ultrasonic disintegration===
Similar to ultrasonic cleaning, [[Cell (biology)|biological cell]]s including [[bacteria]] can be disintegrated. High power ultrasound produces [[cavitation]] that facilitates particle disintegration or reactions. This has uses in [[Biology|biological science]] for analytical or chemical purposes ([[sonication]] and [[sonoporation]]) and in killing bacteria in sewage. High power ultrasound can disintegrate corn slurry and enhance liquefaction and saccharification for higher ethanol yield in dry corn milling plants.<ref>{{cite journal | vauthors = Akin B, Khanal SK, Sung S, Grewell D  |title=Ultrasound pre-treatment of waste activated sludge |doi= 10.2166/ws.2006.962 |year=2006 |journal=Water Science and Technology: Water Supply|volume=6|page=35 |issue=6 }}</ref><ref>{{cite journal | vauthors = Neis U, Nickel K, Tiehm A |title=Enhancement of anaerobic sludge digestion by ultrasonic disintegration |journal=Water Science and Technology|volume=42|issue=9|page=73|date= November 2000 |doi=10.2166/wst.2000.0174|bibcode=2000WSTec..42...73N }}</ref>

===Ultrasonic humidifier===
The ultrasonic humidifier, one type of [[nebulizer]] (a device that creates a very fine spray), is a popular type of humidifier. It works by vibrating a metal plate at ultrasonic frequencies to nebulize (sometimes incorrectly called "atomize") the water. Because the water is not heated for evaporation, it produces a cool mist. The ultrasonic pressure waves nebulize not only the water but also materials in the water including calcium, other minerals, viruses, fungi, bacteria,<ref>{{cite journal | vauthors = Oie S, Masumoto N, Hironaga K, Koshiro A, Kamiya A | title = Microbial contamination of ambient air by ultrasonic humidifier and preventive measures | journal = Microbios | volume = 72 | issue = 292–293 | pages = 161–6 | year = 1992 | pmid = 1488018 }}</ref> and other impurities. Illness caused by impurities that reside in a humidifier's reservoir fall under the heading of "Humidifier Fever".

Ultrasonic humidifiers are frequently used in [[aeroponics]], where they are generally referred to as [[fogger]]s.

===Ultrasonic welding===
In [[ultrasonic welding]] of plastics, high frequency (15&nbsp;kHz to 40&nbsp;kHz) low amplitude vibration is used to create heat by way of friction between the materials to be joined. The interface of the two parts is specially designed to concentrate the energy for maximum weld strength.

===Sonochemistry===
{{Main|Sonochemistry}}
Power ultrasound in the 20–100&nbsp;kHz range is used in chemistry. The ultrasound does not interact directly with [[molecule]]s to induce the chemical change, as its typical wavelength (in the millimeter range) is too long compared to the molecules. Instead, the energy causes [[cavitation]] which generates extremes of temperature and pressure in the liquid where the reaction happens. Ultrasound also breaks up solids and removes [[Passivation (chemistry)|passivating]] layers of [[Chemically inert|inert]] material to give a larger [[surface area]] for the reaction to occur over. Both of these effects make the reaction faster. In 2008, [[Atul Kumar (chemist)|Atul Kumar]] reported synthesis of Hantzsch esters and polyhydroquinoline derivatives via multi-component reaction protocol in aqueous [[micelles]] using ultrasound.<ref>{{cite journal |last1=Kumar |first1=Atul |last2=Maurya |first2=Ram |title=Efficient Synthesis of Hantzsch Esters and Polyhydroquinoline Derivatives in Aqueous Micelles |journal=Synlett |date=April 2008 |volume=2008 |issue=6 |pages=883–885 |doi=10.1055/s-2008-1042908 }}</ref>

Ultrasound is used in [[Liquid-liquid extraction|extraction]], using different frequencies.