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Encyclopedia > Sound

Sound is the vibration of matter, as perceived by the sense of hearing.[1] Physically, sound is vibrational mechanical energy that propagates through matter as a wave. Image File history File links Question_book-3. ... Sound may mean: Sound, physical compressions through a medium Audible compression waves, as used in music A speech sound, or phone, in phonetics Sound (geography), a large ocean inlet, or a narrow ocean channel between two bodies of land Öresund, a specific strait nicknamed The Sound Soundness, a logical term... Soundwave is the name of three fictional characters from the Transformers universes. ... This article is about the senses of living organisms (vision, taste, etc. ... Hearing (or audition) is one of the traditional five senses, and refers to the ability to detect sound. ... In physics, mechanical energy describes the potential energy and kinetic energy present in the components of a mechanical system. ... This article is about matter in physics and chemistry. ... Surface waves in water This article is about waves in the most general scientific sense. ...

Contents

Perception of sound

For humans, hearing is limited to frequencies between about 20 Hz and 20000 Hz, with the upper limit generally decreasing with age. Other species have a different range of hearing. For example, dogs can perceive vibrations higher than 20 kHz. As a signal perceived by one of the major senses, sound is used by many species for detecting danger, navigation, predation, and communication. In Earth's atmosphere, water, and soil virtually any physical phenomenon, such as fire, rain, wind, surf, or earthquake, produces (and is characterized by) its unique sounds. Many species, such as frogs, birds, marine and terrestrial mammals, have also developed special organs to produce sound. In some species, these have evolved to produce song and (in humans) speech. Furthermore, humans have developed culture and technology (such as music, telephony and radio) that allows them to generate, record, transmit, and broadcast sound. For other uses, see Frequency (disambiguation). ... This article is about the SI unit of frequency. ... For other uses, see Species (disambiguation). ... A kilohertz (kHz) is a unit of frequency equal to 1,000 hertz (1,000 cycles per second). ... Look up signal, signaling in Wiktionary, the free dictionary. ... This article is about the senses of living organisms (vision, taste, etc. ... Many animals have developed physical Defence mechanisms (British spelling; Defense mechanisms in American English) which act, as evolutionary characteristics in a similar way to psychological defences. ... This article is about determination of position and direction on or above the surface of the earth. ... Predator and Prey redirect here. ... For the Bobby Womack album, see Communication (1972 album). ... This article is about Earth as a planet. ... For other uses, see Atmosphere (disambiguation). ... The movement of water around, over, and through the Earth is called the water cycle, a key process of the hydrosphere. ... Loess field in Germany Surface-water-gley developed in glacial till, Northern Ireland For the American hard rock band, see SOiL. For the System of a Down song, see Soil (song). ... Physical Phenomena are observable events which are explained by physics or raise some question about matter, light, or spacetime. ... For other uses, see Fire (disambiguation). ... This article is about precipitation. ... For other uses, see Wind (disambiguation). ... For the TV movie also known as The Ocean Waves, see I Can Hear the Sea. ... This article is about the natural seismic phenomenon. ... Distribution of frogs (in black) Suborders Archaeobatrachia Mesobatrachia Neobatrachia - List of Anuran families The frogness babe is an amphibian in the order Anura (meaning tail-less from Greek an-, without + oura, tail), formerly referred to as Salientia (Latin saltare, to jump). ... For other uses, see Bird (disambiguation). ... A marine mammal is a mammal that is primarily ocean-dwelling or depends on the ocean for its food. ... Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the presence of sweat glands, including milk producing sweat glands, and by the presence of: hair, three middle ear bones used in hearing, and a neocortex... This article is about the biological unit. ... Bold text This article does not cite any references or sources. ... This article is about modern humans. ... For other uses, see Music (disambiguation). ... In telecommunication, Telephony encompasses the general use of equipment to provide voice communication over distances. ...


Physics of sound

The mechanical vibrations that can be interpreted as sound can travel through all forms of matter: gases, liquids, solids, and plasmas. However, sound cannot propagate through vacuum. The matter that supports the sound is called the medium. In the physical sciences, a state of matter is one of the many ways that matter can interact with itself to form a macroscopic, homogenous phase. ... Gas phase particles (atoms, molecules, or ions) move around freely Gas is one of the four major states of matter, consisting of freely moving atoms or molecules without a definite shape and without a definite volume. ... For other uses, see Liquid (disambiguation). ... This box:      For other uses, see Solid (disambiguation). ... For other uses, see Plasma. ... Look up Vacuum in Wiktionary, the free dictionary. ... A transmission medium is any material substance, such as fiber-optic cable, twisted-wire pair, coaxial cable, dielectric-slab waveguide, water, or air, that can be used for the propagation of signals, usually in the form of modulated radio, light, or acoustic waves, from one point to another. ...


Longitudinal and transverse waves

Sound is transmitted through gases, plasma, and liquids as longitudinal waves, also called compression waves. Through solids, however, it can be transmitted as both longitudinal and transverse waves. Longitudinal sound waves are waves of alternating pressure deviations from the equilibrium pressure, causing local regions of compression and rarefaction, while transverse waves in solids, are waves of alternating shear stress. Longitudinal waves are waves that have vibrations along or parallel to their direction of travel. ... Bold text Wiktionary has related dictionary definitions, such as: compressor, compression inthe wkjhrlfidhb;g/df == Compressor may refer to: Gas compressor, a mechanical device that compresses a gas e. ... Longitudinal waves are waves that have vibrations along or parallel to their direction of travel. ... A light wave is an example of a transverse wave. ... This article is about pressure in the physical sciences. ... Look up equilibrium in Wiktionary, the free dictionary. ... Physical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. ... Rarefaction is the reduction of a mediums density, or the opposite of compression. ... A light wave is an example of a transverse wave. ... Shear stress is a stress state where the stress is parallel or tangential to a face of the material, as opposed to normal stress when the stress is perpendicular to the face. ...


Matter in the medium is periodically displaced by a sound wave, and thus oscillates. The energy carried by the sound wave is split equally between the potential energy of the extra compression (in case of longitudinal waves) or strain (in case of transverse waves) of the matter and the kinetic energy of the oscillations of the medium. Physical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. ... This article is about the deformation of materials. ...


Sound wave properties and characteristics

Sound waves are characterized by the generic properties of waves, which are frequency, wavelength, period, amplitude, intensity, speed, and direction (sometimes speed and direction are combined as a velocity vector, or wavelength and direction are combined as a wave vector). Surface waves in water This article is about waves in the most general scientific sense. ... For other uses, see Frequency (disambiguation). ... For other uses, see Wavelength (disambiguation). ... Periodicity is the quality of occurring at regular intervals (e. ... It has been suggested that pulse amplitude be merged into this article or section. ... In physics, intensity is a measure of the time-averaged energy flux. ... This page is about the physical speed of sound waves in a medium. ... This article is about positional information. ... This article is about velocity in physics. ... This article is about vectors that have a particular relation to the spatial coordinates. ... A wave vector is a vector that represents two properties of a wave: the magnitude of the vector represents wavenumber (inversely related to wavelength), and the vector points in the direction of wave propagation. ...


Transverse waves, also known as shear waves, have an additional property of polarization. A light wave is an example of a transverse wave. ... Shear stress is a stress state where the stress is parallel or tangential to a face of the material, as opposed to normal stress when the stress is perpendicular to the face. ... In electrodynamics, polarization (also spelled polarisation) is the property of electromagnetic waves, such as light, that describes the direction of their transverse electric field. ...


Sound characteristics can depend on the type of sound waves (longitudinal versus transverse) as well as on the physical properties of the transmission medium. 1) A physical property is an aspect of an object that can be experienced using one of the five human senses: touch, taste, smell, sight or sound, or, in an extended sense, detected through any measuring device. ...


Whenever the pitch of the soundwave is affected by some kind of change, the distance between the sound wave maxima also changes, resulting in a change of frequency. When the loudness of a soundwave changes, so does the amount of compression in airwave that is travelling through it, which in turn can be defined as amplitude. Pitch may refer to: Look up Pitch in Wiktionary, the free dictionary. ... For other uses, see Frequency (disambiguation). ... It has been suggested that pulse amplitude be merged into this article or section. ...


Acoustics and noise

The scientific study of the propagation, absorption, and reflection of sound waves is called acoustics. Acoustics is the branch of physics concerned with the study of sound (mechanical waves in gases, liquids, and solids). ...


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. This article is about noise as in sound. ...


Speed of sound

Main article: Speed of sound

The speed of sound depends on the medium through which the waves are passing, and is often quoted as a fundamental property of the material. In general, the speed of sound is proportional to the square root of the ratio of the elastic modulus (stiffness) of the medium to its density. Those physical properties and the speed of sound change with ambient conditions. For example, the speed of sound in gases depends on temperature. In air at sea level, the speed of sound is approximately 343 m/s, in fresh water 1482 m/s (both at 20 °C, or 68 °F), and in steel about 5960 m/s.[2] The speed of sound is also slightly sensitive (a second-order 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). This page is about the physical speed of sound waves in a medium. ... An elastic modulus, or modulus of elasticity, is the mathematical description of an object or substances tendency to be deformed when a force is applied to it. ... For other uses, see Density (disambiguation). ... For other uses, see Temperature (disambiguation). ... Metre per second (U.S. spelling: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector), defined by distance in metres divided by time in seconds. ... The parametric array is a nonlinear transduction mechanism that generates narrow, nearly sidelobe free beams of low frequency sound, through the mixing and interaction of high frequency sound waves, effectively overcoming the diffraction limit (a kind of spatial uncertainty principle) associated with linear acoustics [1]. Parametric arrays can be formed...


Sound pressure level

Main article: Sound pressure
Sound measurements
Sound pressure p
Particle velocity v
Particle velocity level (SVL)
   (Sound velocity level)
Particle displacement ξ
Sound intensity I
Sound intensity level (SIL)
Sound power Pac
Sound power level (SWL)
Sound energy density E
Sound energy flux q
Acoustic impedance Z
Speed of sound c
v  d  e

Sound pressure is defined as the difference between the actual pressure (at a given point and a given time) in the medium and the average, or equilibrium, pressure of the medium at that location. 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 such average is taken to obtain a root mean square (RMS) value. For example, 1 Pa RMS sound pressure in atmospheric air implies that the actual pressure in the sound wave oscillates between (1 atm -sqrt{2} Pa) and (1 atm +sqrt{2} Pa), that is between 101323.6 and 101326.4 Pa. Such a tiny (relative to atmospheric) variation in air pressure at an audio frequency will be perceived as quite a deafening sound, and can cause hearing damage, according to the table below. Sound pressure is the pressure deviation from the local ambient pressure caused by a sound wave. ... Sound pressure is the pressure deviation from the local ambient pressure caused by a sound wave. ... Particle velocity is the velocity v of a particle (real or imagined) in a medium as it transmits a wave. ... The particle velocity level or the sound velocity level tells the ratio of a sound incidence in comparison to a reference level of 0 dB. It shows the ratio of the particle velocity v1 and the particle velocity v0. ... Particle displacement or particle amplitude (represented in mathematics by the lower-case Greek letter ξ) is a measurement of distance (in metres) of the movement of a particle in a medium as it transmits a wave. ... The sound intensity, I, (acoustic intensity) is defined as the sound power Pac per unit area A. The usual context is the noise measurement of sound intensity in the air at a listeners location. ... Sound intensity level or acoustic intensity level is a logarithmic measure of the sound intensity in comparison to the reference level of 0 dB (decibels). ... Sound power or acoustic power Pac is a measure of sonic energy E per time t unit. ... Sound power level or acoustic power level is a logarithmic measure of the sound power in comparison to a specified reference level. ... The sound energy density or sound density (symbol E or w) is an adequate measure to describe the sound field at a given point as a sound energy value. ... The sound energy flux is the average rate of flow of sound energy for one period through any specified area. ... The acoustic impedance Z (or sound impedance) is a frequency f dependent parameter and is very useful, for example, for describing the behaviour of musical wind instruments. ... This page is about the physical speed of sound waves in a medium. ... In mathematics, the root mean square or rms is a statistical measure of the magnitude of a varying quantity. ... For other uses, see Pascal. ... An audio frequency (abbreviation: AF) is any frequency from about 20 hertz to about 20 kilohertz, which is the approximate range of sound frequencies that is audible to humans. ... The word deaf can have very different meanings depending on the background of the person speaking or the context in which the word is used. ...


As the human ear can detect sounds with a very wide range of amplitudes, sound pressure is often measured as a level on a logarithmic decibel scale. The sound pressure level (SPL) or Lp is defined as For other uses, see Decibel (disambiguation). ...

 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}
where p is the root-mean-square sound pressure and pref is a reference sound pressure. Commonly used reference sound pressures, defined in the standard ANSI S1.1-1994, are 20 µPa in air and 1 µPa in water. Without a specified reference sound pressure, a value expressed in decibels cannot represent a sound pressure level.

Since the human ear does not have a flat spectral response, sound pressures are often frequency weighted so that the measured level will match 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. In mathematics, root mean square (abbreviated RMS or rms), also known as the quadratic mean, is a statistical measure of the magnitude of a varying quantity. ... The American National Standards Institute or ANSI (pronounced an-see) is a nonprofit organization that oversees the development of standards for products, services, processes and systems in the United States. ... The pascal (symbol: Pa) is the SI unit of pressure. ... The pascal (symbol: Pa) is the SI unit of pressure. ... For other uses, see Ear (disambiguation). ... For other uses, see Frequency (disambiguation). ... The International Electrotechnical Commission (IEC) is an international standards organization dealing with electrical, electronic and related technologies. ... The A-weighting curve is one of a family of curves defined in IEC179 and various other standards for use in sound level meters. ...


Examples of sound pressure and sound pressure levels

Source of sound RMS sound pressure sound pressure level
  Pa dB re 20 µPa
Nuclear Weapon explosion approx 248
1883 Krakatoa eruption approx 180
rocket launch equipment acoustic tests approx. 165
threshold of pain 100 134
hearing damage during short-term effect 20 approx. 120
jet engine, 100 m distant 6–200 110–140
jackhammer, 1 m distant / discotheque 2 approx. 100
hearing damage from long-term exposure 0.6 approx. 85
traffic noise on major road, 10 m distant 0.2–0.6 80–90
moving automobile, 10 m distant 0.02–0.2 60–80
TV set – typical home level, 1 m distant 0.02 approx. 60
normal talking, 1 m distant 0.002–0.02 40–60
very calm room 0.0002–0.0006 20–30
quiet rustling leaves, calm human breathing 0.00006 10
auditory threshold at 2 kHz – undamaged human ears 0.00002 0

In mathematics, the root mean square or rms is a statistical measure of the magnitude of a varying quantity. ... For other uses, see Pascal. ... For other uses, see Decibel (disambiguation). ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ... For the 1969 film about the Krakatoa eruption, see Krakatoa, East of Java. ... Fig. ... A Pratt and Whitney turbofan engine for the F-15 Eagle is tested at Robins Air Force Base, Georgia, USA. The tunnel behind the engine muffles noise and allows exhaust to escape. ... This article is about the construction tool. ... Discothèque redirects here. ... Please wikify (format) this article or section as suggested in the Guide to layout and the Manual of Style. ... Car redirects here. ... Threshold of hearing is the sound pressure level SPL of 20 µPa (micropascal) = 2 × 10-5 Pascal (Pa). ...

Equipment for dealing with sound

Equipment for generating or using sound includes musical instruments, hearing aids, sonar systems and sound reproduction and broadcasting equipment. Many of these use electro-acoustic transducers such as microphones and loudspeakers. A musical instrument is a device constructed or modified with the purpose of making music. ... Behind the ear aid For the song, see Flood (album). ... This article is about underwater sound propagation. ... Sound reproduction is the electrical or mechanical re-creation and/or amplification of sound, often as music. ... Microphones redirects here. ... For the Marty Friedman album, see Loudspeaker (album) An inexpensive low fidelity 3. ...


References

  1. ^ Strutt (Rayleigh), J W; Lindsay, R B (1877). The Theory of Sound. Dover Publications. ISBN 0-4866-0292-3. 
  2. ^ The Soundry: The Physics of Sound

See also Rayleigh fading Rayleigh scattering Rayleigh number Rayleigh waves Rayleigh-Jeans law External links Nobel website bio of Rayleigh About John William Strutt MacTutor biography of Lord Rayleigh Categories: People stubs | 1842 births | 1919 deaths | Nobel Prize in Physics winners | Peers | British physicists | Discoverer of a chemical element ...

Sound measurement

For other uses, see Decibel (disambiguation). ... The sone is a unit of perceived loudness N after a proposal of S. Smith Stevens in 1936. ... The mel scale, proposed by Stevens, Volkman and Newman in 1937 (J. Acoust. ... Fig. ... This article is about the SI unit of frequency. ... It has been suggested that this article or section be merged into Sound pressure. ... Particle velocity is the velocity v of a particle (real or imagined) in a medium as it transmits a wave. ... Particle velocity or sound particle velocity is the velocity v of air particles in m/s. ... Particle displacement or particle amplitude (represented in mathematics by the lower-case Greek letter ξ) is a measurement of distance (in metres) of the movement of a particle in a medium as it transmits a wave. ... Particle displacement or particle amplitude ξ is a distance measurement in m (metre) of the movement of a particle(real or imagined) in a medium as it transmits a wave. ... In a compressible sound transmission medium - mainly air - air particles get an accelerated motion: the particle acceleration or sound acceleration with the symbol a in metre/second². In acoustics or physics, acceleration (symbol: a) is defined as the rate of change (or time derivative) of velocity. ... Sound power or acoustic power Pac is a measure of sonic energy E per time t unit. ... Sound power or acoustic power is a measure of sonic energy E per time t unit. ... Sound power level or acoustic power level is a logarithmic measure of the sound power in comparison to a specified reference level. ... The sound energy flux is the average rate of flow of sound energy for one period through any specified area. ... The sound intensity, I, (acoustic intensity) is defined as the sound power Pac per unit area A. The usual context is the noise measurement of sound intensity in the air at a listeners location. ... The sound intensity, J, (acoustic intensity) is defined as the sound power Pac per unit area A. The usual context is the measurement of sound intensity in the air at a listeners location. ... Sound intensity level or acoustic intensity level is a logarithmic measure of the sound intensity in comparison to the reference level of 0 dB (decibels). ... The acoustic impedance Z (or sound impedance) is a frequency f dependent parameter and is very useful, for example, for describing the behaviour of musical wind instruments. ... Acoustic impedance Z (characteristic impedance or sound impedance) is the ratio of sound pressure p to particle velocity v. ... The characteristic impedance of a uniform transmission line is the ratio of the amplitudes of a single pair of voltage and current waves propagating along the line in the absence of reflections. ... This page is about the physical speed of sound waves in a medium. ... It has been suggested that pulse amplitude be merged into this article or section. ...

See also

Pitch Acoustics | Auditory imagery | Audio bit depth | Audio signal processing | Beats | Cycles | Diffraction | Doppler effect | Echo | Music | Note | Phonons | Physics of music | Pitch | Psychoacoustics | Radiation of sound | Resonance | Rijke tube | Reflection | Reverberation | Sonic weaponry | Sound localization | Soundproofing | Timbre | Pitch may refer to: Look up Pitch in Wiktionary, the free dictionary. ... Acoustics is the branch of physics concerned with the study of sound (mechanical waves in gases, liquids, and solids). ... In psychology and neuropsychology, auditory imagery is the subjective experience of hearing in the absence of auditory stimulation. ... This article does not cite its references or sources. ... This article or section does not cite its references or sources. ... In acoustics, a beat is an interference between two sounds of slightly different frequencies, perceived as periodic variations in volume whose rate is the difference between the two frequencies. ... Cycle (music) - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ... The intensity pattern formed on a screen by diffraction from a square aperture Diffraction refers to various phenomena associated with wave propagation, such as the bending, spreading and interference of waves passing by an object or aperture that disrupts the wave. ... A source of waves moving to the left. ... In audio signal processing and acoustics, an echo (plural echoes) is a reflection of sound, arriving at the listener some time after the direct sound. ... For other uses, see Music (disambiguation). ... A phonon is a quantized mode of vibration occurring in a rigid crystal lattice, such as the atomic lattice of a solid. ... Sound waves Variations in air pressure against the ear drum, and the subsequent physical and neurological processing and interpretation, give rise to the experience called sound. Most sound that people recognize as musical is dominated by periodic or regular vibrations rather than non-periodic ones (called a definite pitch), and... Pitch is the perceived fundamental frequency of a sound. ... Psychoacoustics is the study of subjective human perception of sounds. ... Radiation of sound Radiation of sound from structures occurs most efficiently when there is a net volume velocity of the structure surface into the fluid. ... This article is about resonance in physics. ... Rijkes tube turns heat into sound, by creating a self-amplifying standing wave. ... The reflection of a bridge in Indianapolis, Indianas Central Canal. ... This article is about audio effect. ... Sonic and ultrasonic weapons (USW) are weapons of various types that use sound to injure, incapacitate, or kill an opponent. ... Sound localization is a listeners ability to identify the location of origin of a detected sound or the methods in acoustical engineering to simulate the placement of an auditory cue in a virtual 3D space (see binaural recording). ... Soundproofing is any means of to reducing the intensity of sound with respect to a specified source and receptor. ... In music, timbre, or sometimes timber, (from Fr. ...


External links

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Image File history File links This is a lossless scalable vector image. ... Wikiquote is one of a family of wiki-based projects run by the Wikimedia Foundation, running on MediaWiki software. ... Image File history File links Wikibooks-logo-en. ... Wikibooks logo Wikibooks, previously called Wikimedia Free Textbook Project and Wikimedia-Textbooks, is a wiki for the creation of books. ...

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