Editing Tuning fork (section)

==Uses==
Tuning forks have traditionally been used to [[Musical tuning|tune]] [[musical instrument]]s, though [[electronic tuner]]s have largely replaced them. Forks can be driven electrically by placing [[electronic oscillator]]-driven [[electromagnet]]s close to the prongs.

===In musical instruments===
A number of [[keyboard instrument|keyboard]] musical instruments use principles similar to tuning forks. The most popular of these is the [[Rhodes piano]], in which hammers hit metal tines that vibrate in the magnetic field of a [[Pickup (music technology)#Magnetic pickups|pickup]], creating a signal that drives electric amplification. The earlier, un-amplified [[dulcitone]], which used tuning forks directly, suffered from low volume.

===In clocks and watches===
[[File:Inside QuartzCrystal-Tuningfork.jpg|thumb|upright|Quartz crystal resonator from a modern [[quartz watch]], formed in the shape of a tuning fork. It vibrates at 32,768 Hz, in the [[ultrasound|ultrasonic]] range.]]
[[Image:Accutron.jpg|thumb|upright|A [[Bulova]] Accutron watch from the 1960s, which uses a steel tuning fork ''(visible in center)'' vibrating at 360&nbsp;Hz.]]
The [[crystal oscillator|quartz crystal]] that serves as the timekeeping element in modern [[quartz clock]]s and [[watch]]es is in the form of a tiny tuning fork. It usually vibrates at a frequency of 32,768&nbsp;Hz in the [[ultrasound|ultrasonic]] range (above the range of human hearing). It is made to vibrate by small oscillating voltages applied by an [[electronic oscillator]] circuit to metal electrodes plated on the surface of the crystal. Quartz is [[piezoelectric]], so the voltage causes the tines to bend rapidly back and forth.

The [[Accutron]], an [[Electromechanical watches|electromechanical watch]] developed by Max Hetzel<ref>{{Patent|ch|312290}}</ref> and manufactured by [[Bulova]] beginning in 1960, used a 360-[[hertz]] steel tuning fork as its timekeeper, powered by electromagnets attached to a battery-powered transistor oscillator circuit. The fork provided greater accuracy than conventional balance wheel watches. The humming sound of the tuning fork was audible when the watch was held to the ear.

===Medical and scientific uses===
[[Image:Tuning fork oscillator frequency standard.jpg|thumb|upright|1&nbsp;kHz tuning fork [[vacuum tube]] [[electronic oscillator|oscillator]] used by the U.S. National Bureau of Standards (now [[National Institute of Standards and Technology|NIST]]) in 1927 as a frequency standard.]]

Alternatives to the common A=440 standard include [[Scientific pitch|philosophical or scientific pitch]] with standard pitch of C=512. According to [[John William Strutt, 3rd Baron Rayleigh|Rayleigh]], physicists and acoustic instrument makers used this pitch.<ref>{{cite book|last=Rayleigh|first=J. W. S.|title=The Theory of Sound|url=https://archive.org/details/theoryofsoundvol000709mbp|url-access=limited|year=1945|publisher=Dover|location=New York|isbn=0-486-60292-3|page=[https://archive.org/details/theoryofsoundvol000709mbp/page/n54 9]}}</ref> The tuning fork [[John Shore (trumpeter)|John Shore]] gave to [[George Frideric Handel]] produces C=512.<ref>{{cite journal |pmc=1291142 |title=The origin of the tuning fork |first1=RC |last1=Bickerton |first2=GS |last2=Barr |journal=[[Journal of the Royal Society of Medicine]] |volume=80 |issue=12 |pages=771–773 |date=December 1987 |pmid=3323515|doi = 10.1177/014107688708001215}}</ref>

Tuning forks, usually C512, are used by medical practitioners to assess a patient's hearing. This is most commonly done with two exams called the [[Weber test]] and [[Rinne test]], respectively. Lower-pitched ones, usually at C128, are also used to check vibration sense as part of the examination of the peripheral nervous system.<ref>{{cite book |last1=Bickley |first1=Lynn |last2=Szilagyi |first2=Peter |date=2009 |title=Bates' guide to the physical examination and history taking |edition=10th |location=Philadelphia, PA |publisher=Lippincott Williams & Wilkins |isbn=978-0-7817-8058-2}}</ref>

[[orthopedic surgery|Orthopedic surgeons]] have explored using a tuning fork (lowest frequency C=128) to assess injuries where bone fracture is suspected. They hold the end of the vibrating fork on the skin above the suspected fracture, progressively closer to the suspected fracture. If there is a fracture, the [[periosteum]] of the bone vibrates and fires [[nociceptor]]s (pain receptors), causing a local sharp pain.{{citation needed|date=April 2016}} This can indicate a fracture, which the practitioner refers for medical X-ray. The sharp pain of a local sprain can give a false positive.{{citation needed|date=April 2016}} Established practice, however, requires an X-ray regardless, because it's better than missing a real fracture while wondering if a response means a sprain. A systematic review published in 2014 in [[BMJ Open]] suggests that this technique is not reliable or accurate enough for clinical use.<ref>{{cite journal |url= |title=Is there sufficient evidence for tuning fork tests in diagnosing fractures? A systematic review |first1=Kayalvili |last1=Mugunthan |first2=Jenny |last2=Doust |first3=Bodo |last3=Kurz |first4=Paul |last4=Glasziou |date=4 August 2014 |journal=[[BMJ Open]] |volume=4 |issue=8 |pages=e005238 |doi=10.1136/bmjopen-2014-005238|pmid=25091014 |pmc=4127942 }} {{open access}}</ref>

=== Non-medical and non-scientific uses ===
Tuning forks also play a role in several [[alternative medicine|alternative therapy]] practices, such as [[sonopuncture]] and [[polarity therapy]].<ref>{{Cite news|title=SONOPUNCTURE: Acupuncture Without Needles|last=Hawkins|first=Heidi|date=Aug 1995|work=Holistic Health News}}</ref>

=== Radar gun calibration ===
A [[radar gun]] that measures the speed of cars or a ball in sports is usually calibrated with a tuning fork.<ref>{{cite web|url=http://tf.nist.gov/timefreq/general/pdf/87.pdf|title=Calibration of Police Radar Instruments|publisher=National Bureau of Standards|date=1976|access-date=29 October 2008|archive-date=22 February 2012|archive-url=https://web.archive.org/web/20120222143735/http://tf.nist.gov/timefreq/general/pdf/87.pdf|url-status=dead}}</ref><ref>{{cite web| title = A detailed explanation of how police radars work | work = Radars.com.au | publisher = TCG Industrial|location= Perth, Australia | year = 2009 | url = http://radars.com.au/police-radar.php | access-date = 2010-04-08}}</ref> Instead of the frequency, these forks are labeled with the calibration speed and radar band (e.g., X-band or K-band) they are calibrated for.

===In gyroscopes===
Doubled and H-type tuning forks are used for tactical-grade [[Vibrating structure gyroscope#Tuning fork gyroscope|Vibrating Structure Gyroscopes]] and various types of [[microelectromechanical systems]].<ref>{{cite book|title=Proceedings of Anniversary Workshop on Solid-State Gyroscopy (19–21 May 2008. Yalta, Ukraine) |location=Kyiv/Kharkiv |publisher=ATS of Ukraine |date=2009 |isbn=978-976-0-25248-5}}</ref>

===Level sensors===
Tuning fork forms the sensing part of vibrating [[Level sensor#Point level detection of liquids|point level sensors]]. The tuning fork is kept vibrating at its resonant frequency by a piezoelectric device. Upon coming in contact with solids, amplitude of oscillation goes down, the same is used as a switching parameter for detecting point level for solids.<ref>{{Cite web|title=Vital- Vibrating Fork Level Switch for Solids|url=https://www.sapconinstruments.com/products/vital-vibrating-fork-level-switch|access-date=2023-05-28|website=Sapcon Instruments}}</ref> For liquids, the resonant frequency of tuning fork changes upon coming in contact with the liquids, change in frequency is used to detect level.