Tuning fork
A tuning fork is an
The tuning fork was invented in 1711 by British musician John Shore, sergeant trumpeter and lutenist to the royal court.[1]
Description
A tuning fork is a fork-shaped
Another reason for using the fork shape is that it can then be held at the base without
Commercial tuning forks are tuned to the correct pitch at the factory, and the pitch and frequency in hertz is stamped on them. They can be retuned by filing material off the prongs. Filing the ends of the prongs raises the pitch, while filing the inside of the base of the prongs lowers it.
Currently, the most common tuning fork sounds the note of A = 440 Hz, the standard concert pitch that many orchestras use. That A is the pitch of the violin's second-highest string, the highest string of the viola, and an octave above the highest string of the cello. Orchestras between 1750 and 1820 mostly used A = 423.5 Hz, though there were many forks and many slightly different pitches.[5] Standard tuning forks are available that vibrate at all the pitches within the central octave of the piano, and also other pitches.
Tuning fork pitch varies slightly with temperature, due mainly to a slight decrease in the
Calculation of frequency
The frequency of a tuning fork depends on its dimensions and what it is made from: [7]
where
- f is the SI units: 1/s)
- N ≈ 3.516015 is the square of the smallest positive solution to cosh(x) = −1,[8]which arises from the boundary conditions of the prong’s cantilevered structure.
- L is the length of the prongs, (m)
- E is the Young's modulus (elastic modulus or stiffness) of the material the fork is made from, (Pa or N/m2 or kg/(ms2))
- I is the second moment of area of the cross-section, (m4)
- ρ is the density of the fork's material (kg/m3), and
- A is the cross-sectional area of the prongs (tines) (m2).
The ratio I/A in the equation above can be rewritten as r2/4 if the prongs are cylindrical with radius r, and a2/12 if the prongs have rectangular cross-section of width a along the direction of motion.
Uses
Tuning forks have traditionally been used to tune musical instruments, though electronic tuners have largely replaced them. Forks can be driven electrically by placing electronic oscillator-driven electromagnets close to the prongs.
In musical instruments
A number of 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, 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
The
The
Medical and scientific uses
Alternatives to the common A=440 standard include philosophical or scientific pitch with standard pitch of C=512. According to Rayleigh, physicists and acoustic instrument makers used this pitch.[10] The tuning fork John Shore gave to George Frideric Handel produces C=512.[11]
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.[12]
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 nociceptors (pain receptors), causing a local sharp pain.[citation needed] 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] 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.[13]
Non-medical and non-scientific uses
Tuning forks also play a role in several
Radar gun calibration
A
In gyroscopes
Doubled and H-type tuning forks are used for tactical-grade
Level sensors
Tuning fork forms the sensing part of vibrating 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.[18] For liquids, the resonant frequency of tuning fork changes upon coming in contact with the liquids, change in frequency is used to detect level.
See also
- Electronic tuner
- Pitch pipe
- Savart wheel
- Tonometer
References
- PMID 9172630.
- ^ Tyndall, John (1915). Sound. New York: D. Appleton & Co. p. 156.
- ISBN 978-0805385656.[page needed]
- ISBN 9780739002865. Retrieved 3 July 2015.
- ISBN 978-0387983745.[page needed]
- doi:10.1038/021550a0.
- S2CID 121014931.
- ^ Whitney, Scott (23 April 1999). "Vibrations of Cantilever Beams: Deflection, Frequency, and Research Uses". University of Nebraska–Lincoln. Retrieved 9 November 2011.
- ^ ch 312290
- ISBN 0-486-60292-3.
- PMID 3323515.
- ISBN 978-0-7817-8058-2.
- PMID 25091014.
- ^ Hawkins, Heidi (August 1995). "SONOPUNCTURE: Acupuncture Without Needles". Holistic Health News.
- ^ "Calibration of Police Radar Instruments" (PDF). National Bureau of Standards. 1976. Archived from the original (PDF) on 22 February 2012. Retrieved 29 October 2008.
- ^ "A detailed explanation of how police radars work". Radars.com.au. Perth, Australia: TCG Industrial. 2009. Retrieved 8 April 2010.
- ISBN 978-976-0-25248-5.
- ^ "Vital- Vibrating Fork Level Switch for Solids". Sapcon Instruments. Retrieved 28 May 2023.
External links
- Onlinetuningfork.com, an online tuning fork using Flash Player.
- Collier's New Encyclopedia. 1921. .
- Encyclopædia Britannica. Vol. 27 (11th ed.). 1911. p. 392. .