Sound is vibration transmitted through a solid, liquid, or gas; particularly, sound means those vibrations composed of frequencies capable of being detected by ears. [1]
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Perception of sound
For humans, hearing is limited to frequencies between about 20 Hz and 20,000 Hz (20 kHz), with the upper limit generally decreasing with age. Frequency is a measure of the number of occurrences of a repeating event per unit Time. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. Other species have a different range of hearing. In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. 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. Senses are the physiological methods of Perception. The senses and their operation classification and theory are overlapping topics studied by a variety of fields Many Plants and Animals have developed physical defence mechanisms ( American English) Navigation is the process of reading and controlling the movement of a craft or vehicle from one place to another Communication is the process of conveying information from a sender to a receiver with the use of a medium in which the communicated information is understood the same way Earth's atmosphere, water, and virtually any physical phenomenon, such as fire, rain, wind, surf, or earthquake, produces (and is characterized by) its unique sounds. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 An atmosphere (from Greek ατμός - atmos, " Vapor " + σφαίρα - sphaira, " Sphere " A hydrosphere (from Greek ύδωρ - hydor, " Water " + σφαίρα - sphaira, " Sphere " A phenomenon (from Greek φαινόμενoν, pl φαινόμενα - phenomena) is any observable occurrence Fire is the heat and light energy released during a Chemical reaction, in particular a combustion reaction. Rain is Liquid precipitation. On Earth it is the condensation of atmospheric Water vapor into drops heavy enough to fall often making it to Wind is the flow of Air or other Gases that compose an Atmosphere (including but not limited to the Earth's) Ocean surface waves are Surface waves that occur on the Free surface of the Ocean. An earthquake is the result of a sudden release of energy in the Earth 's crust that creates Seismic waves Earthquakes are recorded with a Seismometer Many species, such as frogs, birds, marine and terrestrial mammals, have also developed special organs to produce sound. This article is about the block cipher algorithm For the ultrafast laser pulse measurement technique see Frequency-resolved optical gating. Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Marine mammals are a diverse group of roughly 120 species of Mammal that are primarily Ocean -dwelling or depend on the ocean for food Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands In Biology, an organ ( Latin: organum, "instrument tool" from Greek όργανον - organon "organ instrument In some species, these have evolved to produce song and (in humans) speech. Bird vocalization includes both Bird calls and bird songs In non-technical use bird songs are the bird sounds that are melodious to the human ear Speech refers to the processes associated with the production and perception of Sounds used in Spoken language. Furthermore, humans have developed culture and technology (such as music, telephony and radio) that allows them to generate, record, transmit, and broadcast sound. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Music is an Art form in which the medium is Sound organized in Time. In Telecommunication, telephony (təˈlɛfəni or teh-LEH-fuh-nee encompasses the general use of equipment to provide voice communication over distances specifically Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light.
Physics of sound
The mechanical vibrations that can be interpreted as sound can travel through all forms of matter: gases, liquids, solids, and plasmas. A state of matter (or physical state, or form of matter) has physical properties which are qualitatively different from other states of matter This page is about the physical properties of gas as a state of matter Liquid is one of the principal States of matter. A liquid is a Fluid that has the particles loose and can freely form a distinct surface at the boundaries of A solid' object is in the States of matter characterized by resistance to Deformation and changes of Volume. In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound However, sound cannot propagate through vacuum. This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. The matter that supports the sound is called the medium. A transmission medium' (plural transmission media) is a material substance ( Solid, Liquid or Gas) which can propagate
Longitudinal and transverse waves
Sound is transmitted through gases, plasma, and liquids as longitudinal waves, also called compression waves. Longitudinal waves are waves that have vibrations along or parallel to their direction of travel that is waves in which the motion of the medium is in the same direction as the motion Through solids, however, it can be transmitted as both longitudinal and transverse waves. Longitudinal waves are waves that have vibrations along or parallel to their direction of travel that is waves in which the motion of the medium is in the same direction as the motion A transverse wave is a moving Wave that consists of oscillations occurring perpendicular to the direction of energy transfer 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. Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface 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 medium's density or the opposite of compression. A transverse wave is a moving Wave that consists of oscillations occurring perpendicular to the direction of energy transfer A shear stress, denoted \tau\ ( Tau) is defined as a stress which is applied Parallel or tangential to a face of a material
Matter in the medium is periodically displaced by a sound wave, and thus oscillates. The energy carried by the sound wave converts back and forth between the potential energy of the extra compression (in case of longitudinal waves) or lateral displacement 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.
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). A wave is a disturbance that propagates through Space and Time, usually with transference of Energy. Frequency is a measure of the number of occurrences of a repeating event per unit Time. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. Periodicity is the quality of occurring at regular intervals or periods (in Time or Space) and can occur in different contexts A Clock marks Amplitude is the magnitude of change in the oscillating variable with each Oscillation, within an oscillating system In Physics, intensity is a measure of the time-averaged Energy Flux. Sound is a vibration that travels through an elastic medium as a Wave. Direction is the information contained in the relative position of one point with respect to another point without the Distance information In Physics, velocity is defined as the rate of change of Position. A wave vector is a vector representation of a Wave. The wave vector has magnitude indicating Wavenumber (reciprocal of Wavelength) and the
Transverse waves, also known as shear waves, have an additional property of polarization. A transverse wave is a moving Wave that consists of oscillations occurring perpendicular to the direction of energy transfer A shear stress, denoted \tau\ ( Tau) is defined as a stress which is applied Parallel or tangential to a face of a material Polarization ( ''Brit'' polarisation) is a property of Waves that describes the orientation of their oscillations
Sound characteristics can depend on the type of sound waves (longitudinal versus transverse) as well as on the physical properties of the transmission medium. A physical property is any aspect of an object or substance that can be measured or perceived without changing its identity.
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. Frequency is a measure of the number of occurrences of a repeating event per unit Time. 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. Amplitude is the magnitude of change in the oscillating variable with each Oscillation, within an oscillating system
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. Sound is a vibration that travels through an elastic medium as a Wave. 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. An elastic modulus, or modulus of elasticity, is the mathematical description of an object or substance's tendency to be deformed elastically (i The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different Those physical properties and the speed of sound change with ambient conditions. For example, the speed of sound in gases depends on temperature. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature In air at sea level, the speed of sound is approximately 767. 3 mph, in fresh water 3,315. 1 mph (both at 20 °C, or 68 °F), and in steel about 13,332. 1 mph. [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). 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
Acoustics and noise
The scientific study of the propagation, absorption, and reflection of sound waves is called acoustics. Acoustics is the interdisciplinary science that deals with the study of Sound, Ultrasound and Infrasound (all mechanical waves in gases liquids and solids Noise is a term often used to refer to an unwanted sound. is a one volume manga created by Tsutomu Nihei as a prequel to his ten-volume work Blame!. In science and engineering, noise is an undesirable component that obscures a wanted signal.
Sound pressure level
| 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 |
| Surface S |
| Acoustic impedance Z |
| Speed of sound c
|
Sound pressure is defined as the difference between the average local pressure of the medium outside of the sound wave in which it is traveling through (at a given point and a given time) and the pressure found within the sound wave itself within that same medium. Sound pressure is the local Pressure deviation from the ambient (average or equilibrium pressure caused by a Sound Wave. Sound pressure is the local Pressure deviation from the ambient (average or equilibrium 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 in a medium mostly air Particle displacement or particle amplitude (represented in Mathematics by the lower-case Greek letter &xi) is a Measurement The sound intensity, I, (acoustic intensity is defined as the Sound power Pac per unit area A. 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 P ac 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 q results from the integral Particle velocity v of the surface A, whereby only the portions perpendicularly to the surface In Mathematics, specifically in Topology, a surface is a Two-dimensional Manifold. 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 Sound is a vibration that travels through an elastic medium as a 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 such average is taken to obtain a root mean square (RMS) value. In Mathematics, the root mean square (abbreviated RMS or rms) also known as the quadratic mean, is a statistical measure of the For example, 1 Pa RMS sound pressure in atmospheric air implies that the actual pressure in the sound wave oscillates between (1 atm 
Pa) and (1 atm 
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. An audio frequency (abbreviation AF) or audible frequency is characterized as a periodic vibration whose Frequency is audible to the average human
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 decibel ( dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity relative to The sound pressure level (SPL) or Lp is defined as
- where p is the root-mean-square sound pressure and pref is a reference sound pressure. In Mathematics, the root mean square (abbreviated RMS or rms) also known as the quadratic mean, is a statistical measure of the 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 ear is the sense organ that detects Sounds The Vertebrate ear shows a common biology from Fish to Humans with variations Frequency is a measure of the number of occurrences of a repeating event per unit Time. The International Electrotechnical Commission (IEC) has defined several weighting schemes. The International Electrotechnical Commission ( IEC) is a not-for-profit, non-governmental international Standards organization that prepares and publishes A-weighting attempts to match the response of the human ear to noise and A-weighted sound pressure levels are labeled dBA. A-weighting is the most commonly used of a family of curves defined in the International standard IEC616722003 and various national standards relating to the measurement of sound C-weighting is used to measure peak levels.
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 at 100 miles | |
| Stun grenades | 170-180 | |
| rocket launch equipment acoustic tests | approx. In Mathematics, the root mean square (abbreviated RMS or rms) also known as the quadratic mean, is a statistical measure of the The decibel ( dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity relative to A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. Krakatoa ( Indonesian: Krakatau) also spelled Krakatao or Krakatowa, is a volcanic island in the Sunda Strait 165 | |
| threshold of pain | 100 | 134 |
| hearing damage during short-term effect | 20 | approx. In hearing the Threshold of Pain is the Sound pressure or Sound pressure level beyond which sound becomes unbearable for a human listener 120 |
| jet engine, 100 m distant | 6–200 | 110–140 |
| jackhammer, 1 m distant / discotheque | 2 | approx. specific --->A jet engine is a Reaction engine that discharges a fast moving jet of Fluid to A pneumatic drill or jackhammer is a portable percussive Drill powered by Compressed air. A discothèque, diskoˈtɛk̚ compare the Spanish "discoteca" is an Entertainment venue or Club with recorded music played by "Discaires" 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. The absolute threshold of hearing (ATH is the minimum Sound level of a Pure tone that an average ear with normal hearing can hear in a noiseless environment 00002 | 0 |
Equipment for dealing with sound
Equipment for generating or using sound includes musical instruments, hearing aids, sonar systems and sound reproduction and broadcasting equipment. A musical instrument is a device constructed or modified for the purpose of making Music. A hearing aid is an electroacoustic body-worn apparatus which typically fits in or behind the wearer's Ear, and is designed to amplify and modulate sounds Sonar (which started as an Acronym for sound navigation and ranging) is a technique that uses Sound propagation (usually underwater to navigate Many of these use electro-acoustic transducers such as microphones and loudspeakers. For the Marty Friedman album see Loudspeaker (album A loudspeaker, speaker, or speaker system is an electroacoustical
References
- ^ (2006) The American Heritage Dictionary of the English Language, Fourth Edition. Houghton Mifflin Company.
- ^ The Soundry: The Physics of Sound
Sound measurement
- Decibel, sone, mel, phon, hertz
- Sound pressure level
- Particle velocity, acoustic velocity
- Particle displacement, particle amplitude, particle acceleration
- Sound power, acoustic power, sound power level
- Sound energy flux
- Sound intensity, acoustic intensity, sound intensity level
- Acoustic impedance, sound impedance, characteristic impedance
- Speed of sound, amplitude
- See also Template:Sound measurements
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 | Resonance | Rijke tube | Reflection | Reverberation | Sonic weaponry | Sound localization | Soundproofing | Timbre |
External links
- HyperPhysics: Sound and Hearing
- Introduction to the Physics of Sound
- Hearing curves and on-line hearing test
- Audio for the 21st Century
- Conversion of sound units and levels
- Sounds Amazing a learning resource for sound and waves
- Sound calculations
- Audio Check: a free collection of audio tests and test tones playable on-lineItalic text
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