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| {{About|audible acoustic waves}}
| | They are typically a free website that are pre-designed for enabling businesses of every size in marking the presence on the internet and allows them in showcasing the product services and range through images, contents and various other elements. Online available for hiring are most qualified, well knowledgeable and talented Wordpress developer India from offshore Wordpress development services company. PSD files are incompatible to browsers and are suppose to be converted into wordpress compatible files so that it opens up in browser. After confirming the account, login with your username and password at Ad - Mob. It is found that most of the visitors only look for the results that are displayed on the first page of the search engines and so if you get the service from professional service providers then they strive for the first page ranking of your site and improve the online visibility. <br><br>Right starting from social media support to search engine optimization, such plugins are easily available within the Word - Press open source platform. You may either choose to link only to the top-level category pages or the ones that contain information about your products and services. You are able to set them within your theme options and so they aid the search engine to get a suitable title and description for the pages that get indexed by Google. It primarily lays emphasis on improving the search engine results of your website whenever a related query is typed in the search box. Many times the camera is following Mia, taking in her point of view in almost every frame. <br><br>ve labored so hard to publish and put up on their website. The nominee in each category with the most votes was crowned the 2010 Parents Picks Awards WINNER and has been established as the best product, tip or place in that category. Whether or not it's an viewers on your web page, your social media pages, or your web page, those who have a present and effective viewers of "fans" are best best for provide provides, reductions, and deals to help re-invigorate their viewers and add to their main point here. Nonetheless, with stylish Facebook themes obtainable on the Globe Broad Internet, half of your enterprise is done previously. Purchase these from our site, or bring your own, it doesn't matter, we will still give you free installation and configuration. <br><br>Word - Press installation is very easy and hassle free. Find more information about Design To Wordpress here. Websites that do rank highly, do so becaue they use keyword-heavy post titles. If you just want to share some picture and want to use it as a dairy, that you want to share with your friends and family members, then blogger would be an excellent choice. Word - Press offers constant updated services and products, that too, absolutely free of cost. <br><br>Website security has become a major concern among individuals all over the world. An ease of use which pertains to both internet site back-end and front-end users alike. If you have any issues concerning in which and how to use [http://8128.co/v2u backup plugin], you can make contact with us at the webpage. By the time you get the Gallery Word - Press Themes, the first thing that you should know is on how to install it. Thus, Word - Press is a good alternative if you are looking for free blogging software. Get started today so that people searching for your type of business will be directed to you. |
| {{pp-move-indef|small=yes}}
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| [[File:Thoth08BigasDrumEvansChalmette.jpg|thumb|right|upright|A [[drum]] produces sound via a vibrating membrane.]]
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| '''Sound''' is a [[vibration]] that propagates as a [[mechanical wave]] of [[pressure]] and [[Particle displacement|displacement]], through some [[transmission medium|medium]] (such as [[air]] or [[water]]). Sometimes ''sound'' refers to only those vibrations with [[frequencies]] that are within the [[Hearing range|range of hearing]] for humans<ref>{{cite journal|title=The American Heritage Dictionary of the English Language, Fourth Edition|publisher=Houghton Mifflin Company|year=2000|url=http://www.bartleby.com/61/65/S0576500.html|archiveurl=http://web.archive.org/web/20080625012016/http://www.bartleby.com/61/65/S0576500.html|archivedate=June 25, 2008|accessdate=May 20, 2010}}</ref> or for a particular animal.
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| ==Acoustics==
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| {{main|Acoustics|Acoustical engineering}}
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| [[File:SennMicrophone.jpg|thumb|right|[[Audio engineers#Research and development|Audio engineers in R&D]] design audio equipment]]
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| [[Acoustics]] is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of [[acoustics]] is an acoustician while someone working in the field of [[acoustical engineering]] may be called an acoustic engineer. (Not to be confused with an [[audio engineer]].) The application of acoustics can be seen in almost all aspects of modern society, subdisciplines include: [[aeroacoustics]], [[audio signal processing]], [[architectural acoustics]], [[bioacoustics]], electroacoustics, [[environmental noise]], [[musical acoustics]], [[noise control]], [[psychoacoustics]], [[speech]], [[ultrasound]], [[underwater acoustics]] and [[vibration]].<ref>{{cite web|last=Acoustical Society of America|title=PACS 2010 Regular Edition—Acoustics Appendix|url=http://www.aip.org/pacs/pacs2010/individuals/pacs2010_regular_edition/reg_acoustics_appendix.htm|accessdate=22 May 2013}}</ref>
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| ==Physics of sound==
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| ===Propagation of sound===
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| Sound propagates through compressible media such as air, water and solids as longitudinal waves and also as a transverse waves in solids (see [[#Longitudinal and transverse waves|Longitudinal and transverse waves]], below). The sound waves are generated by a sound source, such as the vibrating diaphragm of a stereo speaker. The sound source creates vibrations in the surrounding medium. As the source continues to vibrate the medium, the vibrations propagate away from the source at the speed of sound, thus forming the sound wave. At a fixed distance from the source, the pressure, velocity, and displacement of the medium vary in time. At an instant in time, the pressure, velocity, and displacement vary in space. Note that the particles of the medium do not travel with the sound wave. This is intuitively obvious for a solid, and ''the same'' is true for liquids and gases (that is, the vibrations of particles in the gas or liquid transport the vibrations, while the ''average'' position of the particles over time does not change). During propagation, waves can be [[Reflection (physics)|reflected]], [[Refraction|refracted]], or [[Attenuation|attenuated]] by the medium.<ref name="JHU">http://www.jhu.edu/virtlab/ray/acoustic.htm</ref>
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| The behavior of sound propagation is generally affected by three things:
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| * A relationship between [[density]] and pressure. This relationship, affected by temperature, determines the speed of sound within the medium.
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| * The propagation is also affected by the motion of the medium itself. For example, sound moving through wind. Independent of the motion of sound through the medium, if the medium is moving, the sound is further transported.
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| * The viscosity of the medium also affects the motion of sound waves. It determines the rate at which sound is attenuated. For many media, such as air or water, attenuation due to viscosity is negligible.
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| When sound is moving through a medium that does not have constant physical properties, it may be refracted (either dispersed or focused).<ref name="JHU" />
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| [[File:Spherical pressure waves.gif|thumb|right|260px|Spherical compression (longitudinal) waves]]
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| The mechanical vibrations that can be interpreted as sound are able to travel through all [[State of matter|forms of matter]]: [[gas]]es, [[liquid]]s, [[solid]]s, and [[plasma (physics)|plasmas]]. The matter that supports the sound is called the [[Transmission medium|medium]]. Sound cannot travel through a [[vacuum]].
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| ===Longitudinal and transverse waves===
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| Sound is transmitted through gases, plasma, and liquids as [[longitudinal wave]]s, also called [[compression (physical)|compression]] waves. Through solids, however, it can be transmitted as both longitudinal waves and [[transverse wave]]s. Longitudinal sound waves are waves of alternating [[pressure]] deviations from the [[Mechanical equilibrium|equilibrium]] pressure, causing local regions of [[compression (physical)|compression]] and [[rarefaction]], while [[transverse wave]]s (in solids) are waves of alternating [[shear stress]] at right angle to the direction of propagation.
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| The energy carried by an oscillating sound wave converts back and forth between the potential energy of the extra [[compression (physical)|compression]] (in case of longitudinal waves) or lateral displacement [[Strain (materials science)|strain]] (in case of transverse waves) of the matter, and the kinetic energy of the displacement velocity of particles of the medium.
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| ===Sound wave properties and characteristics===
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| [[File:Sine waves different frequencies.svg|thumb|right|260px|[[Sine wave|Sinusoidal waves]] of various frequencies; the bottom waves have higher frequencies than those above. The horizontal axis represents time.]]
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| Sound [[wave]]s are often simplified to a description in terms of [[Sine wave|sinusoidal]] [[plane wave]]s, which are characterized by these generic properties:
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| * [[Frequency]], or its inverse, the period
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| * [[Wavelength]]
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| * [[Wavenumber]]
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| * [[Amplitude]]
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| * [[Sound pressure]]
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| * [[Sound intensity]]
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| * [[Speed of sound]]
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| * [[Direction (geometry, geography)|Direction]]
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| Sound that is perceptible by humans has frequencies from about 20 Hz to 20,000 Hz. In air at [[standard temperature and pressure]], the corresponding wavelengths of sound waves range from 17 m to 17 mm.
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| Sometimes speed and direction are combined as a [[velocity]] [[Vector (geometric)|vector]]; wavenumber and direction are combined as a [[wave vector]].
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| [[Transverse wave]]s, also known as [[Shear stress|shear]] waves, have the additional property, ''[[Polarization (waves)|polarization]]'', and are not a characteristic of sound waves.
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| ===Speed of sound===
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| [[File:FA-18 Hornet breaking sound barrier (7 July 1999) - filtered.jpg|right|thumb|U.S. Navy [[F/A-18 Hornet|F/A-18]] approaching the sound barrier. The white halo is formed by condensed water droplets thought to result from a drop in air pressure around the aircraft (see [[Prandtl-Glauert Singularity]]).<ref>[http://antwrp.gsfc.nasa.gov/apod/ap070819.html APOD: 19 August 2007 – A Sonic Boom<!-- Bot generated title -->]</ref><ref>http://www.eng.vt.edu/fluids/msc/gallery/conden/mpegf14.htm</ref>]]
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| <math></math>
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| {{main|Speed of sound}}
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| The speed of sound depends on the medium the waves pass through, and is a fundamental property of the material.The first significant effort towards developing a formula to measure the speed of sound was made by Newton. he said that the speed of sound in a particular substance was equal to the square root of the pressure acting on it ([[Standard conditions for temperature and pressure|STP]]) divided by its density.
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| <math>
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| c = \sqrt{ {p \over \rho}}\,
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| </math>
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| However it was later proved wrong and was giving wrong answers.So another scientist Laplace corrected the formula by deducting that the phenomenon of sound travelling is not isothermal, as believed by Newton, but adiabatic.He added another factor to the equation-''gamm''a and multiplied <math>
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| \sqrt{\gamma}\,
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| </math> to <math>\sqrt{ {p \over \rho}}\,</math> .Thus coming up with the equation <math>
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| c = \sqrt{\gamma \cdot {p \over \rho}}\,
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| </math> . Since <math>
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| K = \gamma \cdot p\,
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| </math> therefore the final equation came up to be <math>
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| c = \sqrt{\frac{K}{\rho}}\,
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| </math> which is also known as the Newton-Laplace equation.in the equation K = elastic modulus and c = velocity of sound <math> {\rho}\,</math> = density.Thus, the speed of sound is proportional to the [[square root]] of the [[ratio]] of the [[elastic modulus]] (stiffness) of the medium to its [[density]].
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| Those physical properties and the speed of sound change with ambient conditions. For example, the speed of sound in gases depends on [[temperature]]. In {{convert|20|C|F|lk=on}} air at [[sea level]], the speed of sound is approximately {{convert|343|m/s|km/h mph|abbr=on|sigfig=3}} using the formula "v = (331 + 0.6 T) m/s". In fresh water, also at 20 °C, the speed of sound is approximately {{convert|1482|m/s|km/h mph|abbr=on|sigfig=4}}. In [[steel]], the speed of sound is about {{convert|5960|m/s|km/h mph|abbr=on|sigfig=4}}.<ref>[http://library.thinkquest.org/19537/Physics4.html The Soundry: The Physics of Sound]</ref> The speed of sound is also slightly sensitive (a second-order [[Anharmonicity|anharmonic]] effect) to the sound amplitude, which means that there are nonlinear propagation effects, such as the production of harmonics and mixed tones not present in the original sound (see [[parametric array]]).
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| ==Perception of sound==
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| [[File:Ear.jpg|thumb|right|150px|Human ear]]
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| The perception of sound in any organism is limited to a certain range of frequencies. For humans, hearing is normally limited to frequencies between about 20 [[Hertz|Hz]] and 20,000 Hz (20 [[kHz]]),<ref>{{cite journal|url=http://books.google.com/books?id=RUDTFBbb7jAC&pg=PA248|title=Music, Physics and Engineering|isbn=9780486217697|author1=Olson|first1=Harry F. Autor|year=1967}}</ref> although these limits are not definite. The upper limit generally decreases with age. Other [[species]] have a different range of hearing. For example, dogs can perceive vibrations higher than 20 kHz, but are deaf to anything below 40 Hz. As a signal perceived by one of the major [[sense]]s, sound is used by many species for [[defence mechanism (biology)|detecting danger]], [[navigation]], [[predation]], and [[communication]]. [[Earth]]'s [[atmosphere]], [[hydrosphere|water]], and virtually any [[physical phenomenon]], such as [[fire]], [[rain]], [[wind]], [[ocean surface wave|surf]], or [[earthquake]], produces (and is characterized by) its unique sounds. Many species, such as [[frog]]s, [[bird]]s, [[marine mammals|marine]] and terrestrial [[mammal]]s, have also developed special [[organ (anatomy)|organs]] to produce sound. In some species, these produce [[bird vocalization|song]] and [[speech communication|speech]]. Furthermore, [[human]]s have developed culture and technology (such as [[music]], [[telephone]] and [[radio]]) that allows them to generate, record, transmit, and broadcast sound. The scientific study of human sound perception is known as [[psychoacoustics]].
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| ===Noise===
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| {{main|Noise}}
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| Noise is a term often used to refer to an unwanted sound. In science and engineering, noise is an undesirable component that obscures a wanted signal.
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| ==Sound pressure level==
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| {{main|Sound pressure}}
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| {{Sound measurements}}
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| Sound pressure is the difference, in a given medium, between average local pressure and the pressure in the sound wave. A square of this difference (i.e., a square of the deviation from the equilibrium pressure) is usually averaged over time and/or space, and a square root of this average provides a [[root mean square]] (RMS) value. For example, 1 [[Pascal (unit)|Pa]] RMS sound pressure (94 dBSPL) in atmospheric air implies that the actual pressure in the sound wave oscillates between (1 atm <math>-\sqrt{2}</math> Pa) and (1 atm <math>+\sqrt{2}</math> Pa), that is between 101323.6 and 101326.4 Pa.
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| As the human ear can detect sounds with a wide range of amplitudes, sound pressure is often measured as a level on a logarithmic [[decibel]] scale. The '''sound pressure level''' (SPL) or ''L''<sub>p</sub> is defined as
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| :<math>
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| L_\mathrm{p}=10\, \log_{10}\left(\frac{{p}^2}{{p_\mathrm{ref}}^2}\right) =20\, \log_{10}\left(\frac{p}{p_\mathrm{ref}}\right)\mbox{ dB}\,
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| </math>
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| :where ''p'' is the [[root-mean-square]] sound pressure and <math>p_\mathrm{ref}</math> is a reference sound pressure. Commonly used reference sound pressures, defined in the standard [[American National Standards Institute|ANSI]] S1.1-1994, are 20 [[micropascal|µPa]] in air and 1 [[micropascal|µPa]] in water. Without a specified reference sound pressure, a value expressed in decibels cannot represent a sound pressure level.
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| Since the human [[ear]] does not have a flat [[Responsivity|spectral response]], sound pressures are often [[frequency]] weighted so that the measured level matches perceived levels more closely. The [[International Electrotechnical Commission]] (IEC) has defined several weighting schemes. [[A-weighting]] attempts to match the response of the human ear to noise and A-weighted sound pressure levels are labeled dBA. C-weighting is used to measure peak levels.
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| ==Equipment for dealing with sound==
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| Equipment for outputing or generating : [[musical instrument]], [[sound box]], [[Headphones|hearing phones]], [[sonar]] systems, [[sound reproduction]], and broadcasting equipment. Many of these use electro-acoustic transducers for input : [[microphone]]s .
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| ==Sound measurement==
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| * [[Decibel]], [[Sone]], [[Mel scale|mel]], [[Phon]], [[Hertz]]
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| * [[Sound pressure level]], [[Sound pressure]]
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| * [[Particle velocity]], [[Acoustic velocity]]
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| * [[Particle displacement]], [[Particle amplitude]], [[Particle acceleration]]
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| * [[Sound power]], [[Acoustic power]], [[Sound power level]]
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| * [[Sound energy flux]]
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| * [[Sound intensity]], [[Acoustic intensity]], [[Sound intensity level]]
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| * [[Acoustic impedance]], [[Sound impedance]], [[Characteristic impedance]]
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| * [[Speed of sound]], [[Amplitude]]
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| ==See also==
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| {{div col|cols=2}}
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| * [[Acoustic theory]]
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| * [[Beat (acoustics)|Beat]]
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| * [[Doppler effect]]
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| * [[Echo (phenomenon)|Echo]]
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| * [[Musical tone]]
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| * [[Pitch (music)|Pitch]]
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| * [[Resonance]]
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| * [[Reverberation]]
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| * [[Sonic weaponry]]
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| * [[Sound localization]]
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| * [[Soundproofing]]
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| * [[Structural acoustics]]
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| * [[Timbre]]
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| * [[Ultrasound]]
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| * [[List of unexplained sounds]]
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| {{div col end}}
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| ==References==
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| {{Reflist|2}}
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| ==External links==
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| {{wikiquote}}
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| {{wikibooks}}
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| {{commons category}}
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| {{Wikisource}}
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| {{Library resources box
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| |by=no
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| |onlinebooks=no
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| |others=no
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| |about=yes
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| |label=Sound }}
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| * [http://www.acoustics.salford.ac.uk/schools/index1.htm Sounds Amazing; a KS3/4 learning resource for sound and waves]
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| * [http://hyperphysics.phy-astr.gsu.edu/hbase/sound/soucon.html HyperPhysics: Sound and Hearing]
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| * [http://podcomplex.com/guide/physics.html Introduction to the Physics of Sound]
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| * [http://www.phys.unsw.edu.au/~jw/hearing.html Hearing curves and on-line hearing test]
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| * [http://www.audiodesignline.com/howto/audioprocessing/193303241 Audio for the 21st Century]
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| * [http://www.sengpielaudio.com/calculator-soundlevel.htm Conversion of sound units and levels]
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| * [http://www.sengpielaudio.com/Calculations03.htm Sound calculations]
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| * [http://www.audiocheck.net Audio Check: a free collection of audio tests and test tones playable on-line]
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| * [http://www.acoustics.salford.ac.uk/feschools/ More Sounds Amazing; a sixth-form learning resource about sound waves]
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| {{Acoustics}}
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| [[Category:Acoustics]]
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| [[Category:Hearing]]
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| [[Category:Waves]]
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| [[Category:Qualia]]
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| [[Category:Sound| ]]
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