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This page is about audible acoustic waves. For other uses see Sound (disambiguation)
Sound (disambiguation)

Sound may mean*Sound, Audible sense perceived by the brain,**in the form of music, speech sound, or general noise*Sound , verb meaning to take depth readings of fluids in a tank or around a ship...
 or Soundwave
Soundwave

Soundwaves are audible acoustic waves that carry sound.Soundwave may also refer to*Soundwave , an annual music festival held in Australia...


Sound is vibration
Vibration

Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic function such as the motion of a pendulum or random such as the movement of a tire on a gravel road....
 transmitted through a solid
Solid

A solid object is in the states of matter characterized by resistance to deformation and changes of volume. In other words, it has high values both of Young's modulus and of shear modulus; this contrasts e.g....
, liquid
Liquid

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 its bulk material....
, or gas
Gas

In physics, a gas is a state of matter, consisting of a collection of particles without a definite shape or volume that are in more or less random motion....
, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.

humans, hearing is limited to frequencies between about 20 Hz
Hertz

The hertz is a measure of frequency per unit of time, or the number of list of cycles per second. It is the SI base unit of frequency in the International System of Units , and is used worldwide in both general-purpose and scientific contexts....
  and 20,000 Hz (20 kHz), with the upper limit generally decreasing with age.






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This page is about audible acoustic waves. For other uses see Sound (disambiguation)
Sound (disambiguation)

Sound may mean*Sound, Audible sense perceived by the brain,**in the form of music, speech sound, or general noise*Sound , verb meaning to take depth readings of fluids in a tank or around a ship...
 or Soundwave
Soundwave

Soundwaves are audible acoustic waves that carry sound.Soundwave may also refer to*Soundwave , an annual music festival held in Australia...


Sound is vibration
Vibration

Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic function such as the motion of a pendulum or random such as the movement of a tire on a gravel road....
 transmitted through a solid
Solid

A solid object is in the states of matter characterized by resistance to deformation and changes of volume. In other words, it has high values both of Young's modulus and of shear modulus; this contrasts e.g....
, liquid
Liquid

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 its bulk material....
, or gas
Gas

In physics, a gas is a state of matter, consisting of a collection of particles without a definite shape or volume that are in more or less random motion....
, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.

Perception of sound


Ear
For humans, hearing is limited to frequencies between about 20 Hz
Hertz

The hertz is a measure of frequency per unit of time, or the number of list of cycles per second. It is the SI base unit of frequency in the International System of Units , and is used worldwide in both general-purpose and scientific contexts....
  and 20,000 Hz (20 kHz), with the upper limit generally decreasing with age. Other species
Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring....
 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 sense
Sense

Senses are the physiological methods of perception. The senses and their operation, classification, and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology , and philosophy of perception....
s, sound is used by many species for detecting danger, navigation
Navigation

Navigation is the process of reading, and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks....
, predation
Predation

In ecology, predation describes a biological interaction where a predator feeds on its prey, the organism that is attacked. Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of the prey....
, and communication
Communication

Communication is commonly defined as "the imparting or interchange of thoughts, opinions, or information by speech, writing, or signs...",, 1: an act or instance of transmitting and 3 a: "a process by which information is exchanged between individuals through a common system of symbols, signs, or beha...
. Earth
Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
's atmosphere
Atmosphere

An atmosphere is a layer of gases that may surround a material body of sufficient mass, by the gravity of the body, and are retained for a longer duration if gravity is high and the atmosphere's temperature is low....
, water
Hydrosphere

A hydrosphere in physical geography describes the combined mass of water found on, under, and over the surface of a planet....
, and virtually any physical phenomenon, such as fire
Fire

Fire is the oxidation of a combustion material releasing heat, light, and various Chemical reaction products such as carbon dioxide and water....
, rain
Rain

Rain is liquid precipitation . On Earth, it is the condensation of atmospheric water vapor into droplet heavy enough to fall, often making it to the surface....
, wind
WIND

The Global Geospace Science WIND satellite is a NASA science spacecraft launched at 04:31:00 EST on November 1, 1994 from launch pad 17B at Cape Canaveral Air Force Station in Merritt_Island%2C_Florida, Florida aboard a McDonnell Douglas Delta II 7925-10 rocket....
, surf
Ocean surface wave

In fluid dynamics wind waves, or more precisely wind generated waves, are surface waves that occur on the free surface of oceans, seas, lakes, rivers and canals ? or even on small puddles and ponds....
, or earthquake
Earthquake

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, also known as a seismograph....
, produces (and is characterized by) its unique sounds. Many species, such as frog
Frog

Frogs are amphibians in the order Anura , formerly referred to as Salientia . The name frog derives from Old English language frogga, , cognate with Sanskrit plava , probably deriving from Proto-Indo-European language praw = "to jump"....
s, bird
Bird

Birds are wing, Bipedalismal, endothermic , vertebrate animals that lay egg . There are around 10,000 living species, making them the most numerous tetrapod vertebrates....
s, marine and terrestrial mammal
Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
s, have also developed special organ
Organ (anatomy)

In biology, an organ is a biological tissue that performs a specific function or group of functions. Usually there is a main tissue and sporadic tissues....
s to produce sound. In some species, these have evolved to produce song and speech. Furthermore, human
Human

A human being, also human or man, is a member of a species of bipedalism primates in the family Hominidae . Mitochondrial DNA evidence indicates that modern humans originated in east Africa about 200,000 years ago....
s have developed culture and technology (such as music
Music

Music is an art form whose media is sound organized in time. Common elements of music are pitch , rhythm , dynamics , and the sonic qualities of timbre and texture ....
, telephone
Telephone

The telephone is a telecommunications device that is used to transmitter and receive electronically or digitally encoded sound between two or more people conversing....
 and radio
Radio

Radio is the transmission of signals, by modulation of electromagnetic radiation with frequency below those of visible light.Electromagnetic radiation radio propagation by means of oscillating electromagnetic fields that pass through the air and the vacuum of space....
) that allows them to generate, record, transmit, and broadcast sound.

Physics of sound


The mechanical vibrations that can be interpreted as sound are able to travel through all forms of matter
State of matter

States of matter are the distinct forms that different phase take on. Historically, the distinction is made based on qualitative differences in bulk properties....
: gas
Gas

In physics, a gas is a state of matter, consisting of a collection of particles without a definite shape or volume that are in more or less random motion....
es, liquid
Liquid

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 its bulk material....
s, solid
Solid

A solid object is in the states of matter characterized by resistance to deformation and changes of volume. In other words, it has high values both of Young's modulus and of shear modulus; this contrasts e.g....
s, and plasma
Plasma (physics)

In physics and chemistry, plasma is a partially ionized gas, in which a certain proportion of electrons are free rather than being bound to an atom or molecule....
s. The matter that supports the sound is called the medium
Transmission medium

A transmission medium is a material substance which can wave propagation energy waves. For example, the transmission medium for sound received by the ears is usually air, but solids and liquids may also act as transmission media for sound....
. Sound cannot travel through vacuum
Vacuum

A vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty," but in reality, no volume of space can ever be perfectly empty....
.

Longitudinal and transverse waves

Sound is transmitted through gases, plasma, and liquids as longitudinal wave
Longitudinal wave

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 of the wave....
s, also called compression
Compression

Compression may refer to:In physical science:*Physical compression, the result of the subjection of a material to compressive stress**Compression member, a class of structural elements, of which a column is the most common specific example...
 waves. Through solids, however, it can be transmitted as both longitudinal
Longitudinal wave

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 of the wave....
 and transverse wave
Transverse wave

A transverse wave is a moving wave that consists of oscillations occurring perpendicular to the direction of energy transfer. If a transverse wave is moving in the positive x-direction, its oscillations are in up and down directions that lie in the y-z plane....
s. Longitudinal sound waves are waves of alternating pressure
Pressure

Pressure is the force per unit area applied to an object in a direction surface normal to the surface. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure....
 deviations from the equilibrium
Equilibrium

For the opposite, see disequilibrium.Equilibrium is the condition of a system in which competing influences are balanced and it may refer to:...
 pressure, causing local regions of compression
Physical compression

Physical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. The opposite of compression is tension ....
 and rarefaction
Rarefaction

Rarefaction is the reduction of a medium's density, or the opposite of Physical compression.A natural example of this is as a Phase in a sound wave or phonon....
, while transverse wave
Transverse wave

A transverse wave is a moving wave that consists of oscillations occurring perpendicular to the direction of energy transfer. If a transverse wave is moving in the positive x-direction, its oscillations are in up and down directions that lie in the y-z plane....
s in solids, are waves of alternating shear stress
Shear stress

File:Shear stress.JPGA shear stress, denoted , is defined as a stress which is applied parallel or tangent to a face of a material, as opposed to a normal stress which is applied perpendicularly....
.

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
Physical compression

Physical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. The opposite of compression is tension ....
 (in case of longitudinal waves) or lateral displacement strain
Strain (materials science)

In continuum mechanics, the infinitesimal strain theory, sometimes called small deformation theory, small displacement theory, or small displacement-gradient theory, deals with infinitesimal Deformation s of a Continuum mechanics....
 (in case of transverse waves) of the matter and the kinetic energy of the oscillations of the medium.

Sound wave properties and characteristics

Sound waves are characterized by the generic properties of waves
Wave

A wave is a disturbance that propagates through space and time, usually with transference of energy. While a mechanical wave exists in a medium , waves of electromagnetic radiation can travel through vacuum, that is, without a medium....
, which are frequency
Frequency

Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency....
, wavelength
Wavelength

In physics, wavelength is the distance between repeating units of a propagating wave of a given frequency. It is commonly designated by the Greek language letter lambda ....
, period
Periodicity

Periodicity is the quality of occurring at regular intervals or periods and can occur in different contexts:In timing devices:* A clock marks time at periodic intervals....
, amplitude
Amplitude

Amplitude is the magnitude of change in the oscillating variable, with each oscillation, within an oscillating system. For instance, sound waves are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation....
, intensity
Intensity (physics)

In physics, intensity is a Measurement of the time averaging energy flux. The word "intensity" here is not synonymous with "wikt:strength", "wikt:amplitude", or "wikt:level", as it sometimes is in colloquial speech....
, speed
Speed of sound

Sound is a vibration that travels through an elasticity medium as a wave. The speed of sound describes how much distance such a wave travels in a certain amount of time....
, and direction
Direction (geometry, geography)

Direction is the information contained in the relative position of one point with respect to another point without the distance information. Directions may be either Relative direction to some indicated reference , or absolute according to some previously agreed upon frame of reference ....
 (sometimes speed and direction are combined as a velocity
Velocity

In physics, velocity is defined as the Derivative of Position vector. It is a vector physical quantity; both speed and direction are required to define it....
 vector, or wavelength and direction are combined as a wave vector
Wave vector

A wave vector is a vector representation of a wave. The wave vector has magnitude indicating wavenumber , and the direction of the vector indicates the direction of wave propagation....
).

Transverse wave
Transverse wave

A transverse wave is a moving wave that consists of oscillations occurring perpendicular to the direction of energy transfer. If a transverse wave is moving in the positive x-direction, its oscillations are in up and down directions that lie in the y-z plane....
s, also known as shear
Shear stress

File:Shear stress.JPGA shear stress, denoted , is defined as a stress which is applied parallel or tangent to a face of a material, as opposed to a normal stress which is applied perpendicularly....
 waves, have an additional property of polarization
Polarization

Polarization is a property of waves that describes the orientation of their oscillations. For transverse waves such as many electromagnetic waves, it describes the orientation of the oscillations in the plane perpendicular to the wave's direction of travel....
.

Sound characteristics can depend on the type of sound waves (longitudinal versus transverse) as well as on the physical properties of the transmission medium.

Whenever the pitch
Pitch (music)

Pitch represents the perceived fundamental frequency of a sound. It is one of the three major auditory system attributes of sounds along with loudness and timbre....
 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

Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the 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
Amplitude

Amplitude is the magnitude of change in the oscillating variable, with each oscillation, within an oscillating system. For instance, sound waves are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation....
.

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
Square root

In mathematics, a square root of a number x is a number r such that r2 = x, or, in other words, a number r whose square is x....
 of the ratio
Ratio

A ratio is an expression which compares quantities relative to each other. The most common examples involve two quantities, but in theory any number of quantities can be compared....
 of the elastic modulus
Elastic modulus

An elastic modulus, or modulus of elasticity, is the mathematical description of an object or substance's tendency to be deformed elastically when a force is applied to it....
 (stiffness) of the medium to its density
Density

The density of a material is defined as its mass per unit volume. The symbol of density is ....
. Those physical properties and the speed of sound change with ambient conditions. For example, the speed of sound in gases depends on temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
. In air at the sea level
Sea level

Mean sea level is the average height of the sea, with reference to a suitable reference surface. Defining the reference level , however, involves complex measurement, and accurately determining MSL can prove difficult....
, the speed of sound is approximately . In fresh water, also at 20 °C, the speed of sound is approximately . In steel
Steel

Steel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.14% by weight , depending on grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese, chromium, vanadium, and tungsten....
, the speed of sound is about . The speed of sound is also slightly sensitive (a second-order anharmonic
Anharmonicity

Anharmonicity is the deviation of a system from being a harmonic oscillator. An oscillator that is not oscillating in simple harmonic motion is known as an anharmonic oscillator where the system can be approximated to a harmonic oscillator and the anharmonicity can be calculated using perturbation theory....
 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
Parametric array

The parametric array is a nonlinear transducer 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 associated with linear acoustics....
).

Acoustics and noise

The scientific study of the propagation, absorption, and reflection of sound waves is called acoustics
Acoustics

Acoustics is the interdisciplinary science that deals with the study of sound, ultrasound and infrasound . A scientist who works in the field of acoustics is an acoustician....
. Noise
Noise

In common use, the word noise means unwanted sound or noise pollution. In electronics noise can refer to the electronic signal corresponding to acoustic noise or the electronic signal corresponding to the noise commonly seen as 'Noise ' on a degraded television or video image....
 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.

Sound pressure level

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. 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
Root mean square

In mathematics, the root mean square , also known as the quadratic mean, is a statistics measure of the magnitude of a varying quantity. It is especially useful when variates are positive and negative, e.g., sinusoids....
 (RMS) value. For example, 1 Pa
Pascal (unit)

The pascal is the SI derived unit of pressure, stress , Young's modulus and tensile strength. It is a measure of force per unit area i.e. equivalent to one newton per square meter or one joule per cubic meter....
 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
Audio frequency

An audio frequency , or audible frequency is characterized as a periodic vibration whose frequency is audible to the average human. While the range of frequencies that any individual can hear is largely related to environmental factors, the generally accepted standard range of audible frequencies is 20 to 20,000 hertz....
 will be perceived as quite a deafening sound, and can cause hearing damage, according to the table below.

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
Decibel

The decibel is a logarithmic units of measurement that expresses the magnitude of a physical quantity relative to a specified or implied reference level....
 scale. The sound pressure level (SPL) or Lp is defined as

where p is the root-mean-square sound pressure and is a reference sound pressure. Commonly used reference sound pressures, defined in the standard ANSI
American National Standards Institute

The American National Standards Institute or ANSI is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States....
 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
Ear

The ear is the sense organ that detects sounds. The vertebrate ear shows a common biology from fish to humans, with variations in structure according to order and species....
 does not have a flat spectral response
Responsivity

Responsivity measures the input?output gain of a detector system. For a system that responds linearly to its input, there is a unique responsivity....
, sound pressures are often frequency
Frequency

Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency....
 weighted so that the measured level will match perceived levels more closely. The International Electrotechnical Commission
International Electrotechnical Commission

The International Electrotechnical Commission is a Non-profit organization, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies ? collectively known as "electrotechnology"....
 (IEC) has defined several weighting schemes. A-weighting
A-weighting

A Weighting curve is a graph that is used to 'weight' measured values of a variable according to their importance in relation to some outcome. The most commonly know example is in sound level measurement where a specific set of weighting curves known as A, B, C and D weighting are often used....
 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.

Examples of sound pressure and sound pressure levels


Source of sound RMS
Root mean square

In mathematics, the root mean square , also known as the quadratic mean, is a statistics measure of the magnitude of a varying quantity. It is especially useful when variates are positive and negative, e.g., sinusoids....
 sound pressure 		sound pressure level
  Pa
Pascal (unit)

The pascal is the SI derived unit of pressure, stress , Young's modulus and tensile strength. It is a measure of force per unit area i.e. equivalent to one newton per square meter or one joule per cubic meter....
 		 dB
Decibel

The decibel is a logarithmic units of measurement that expresses the magnitude of a physical quantity relative to a specified or implied reference level....
 re 20 µPa
Theoretical limit for undistorted sound at
1 atmosphere
Atmosphere (unit)

The standard atmosphere is an international reference pressure defined as 101,325 Pascal and formerly used as unit of pressure . For practical purposes it has been replaced by the Bar which is 100,000 Pa....
 environmental pressure
Pressure

Pressure is the force per unit area applied to an object in a direction surface normal to the surface. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure....
 		 101,325 191
1883 Krakatoa
Krakatoa

Krakatoa , also spelled Krakatao, is a Island#Oceanic islands in the Sunda Strait between the islands of Java and Sumatra in Indonesia. The name is used for the island group, the main island , and the volcano as a whole....
 eruption		 approx 180 at 100 miles
Stun grenades 170-180
rocket launch equipment acoustic tests approx. 165
threshold of pain
Threshold of pain

In hearing, the threshold of pain is the sound pressure or sound pressure level beyond which sound becomes unbearable for a human listener. This threshold varies only slightly with frequency....
 		 100 134
hearing damage during short-term effect 20 approx. 120
jet engine
Jet engine

A jet engine is a reaction engine that discharges a fast moving jet of fluid to generate thrust in accordance with Isaac Newton Newton's laws of motion....
, 100 m distant 		6–200 110–140
jackhammer
Jackhammer

A pneumatic drill or jackhammer is a portable percussive drill powered by compressed air . It is used to drill rock and break up pavement , among other applications....
, 1 m distant / discotheque
Discothčque

A discoth?que, , is an entertainment venue or club with music record played by "Discaires" through a PA system, rather than an Live band dance....
 		 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
Automobile

An automobile or motor car is a wheeled motor vehicle for transportation passengers, which also carries its own car engine or motor. Most definitions of the term specify that automobiles are designed to run primarily on roads, to have seating for one to eight people, to typically have four wheels, and to be constructed principally f...
, 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


Equipment for dealing with sound

Equipment for generating or using sound includes musical instrument
Musical instrument

A musical instrument is an object constructed or used for the purpose of making music. In principle, anything that produces sound can serve as a musical instrument....
s, hearing aid
Hearing aid

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 Modulation sounds for the wearer....
s, sonar
Sonar

Sonar is a technique that uses sound propagation to navigation, communicate with or detect other vessels. There are two kinds of sonar: active and passive....
 systems and sound reproduction and broadcasting equipment. Many of these use electro-acoustic transducers such as microphone
Microphone

A microphone, sometimes referred to as a mike or?more recently?mic, is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal....
s and loudspeaker
Loudspeaker

A loudspeaker, speaker, or speaker system is an electroacoustical transducer that converts an electricity signal processing to sound....
s.

Sound measurement


See also

Pitch
Pitch (music)

Pitch represents the perceived fundamental frequency of a sound. It is one of the three major auditory system attributes of sounds along with loudness and timbre....
 Acoustics
Acoustics

Acoustics is the interdisciplinary science that deals with the study of sound, ultrasound and infrasound . A scientist who works in the field of acoustics is an acoustician....
 | Auditory imagery
Auditory imagery

In psychology and neuropsychology, auditory imagery is the subjective experience of hearing in the absence of auditory system stimulation. It occurs when one mentally rehearses telephone numbers, or has a song "on the brain": the phenomenon is usually defined to be spontaneous ; it can be distressing....
 | Audio bit depth
Audio bit depth

In digital audio, bit depth describes the number of bits of information recorded for each Sample_. Bit depth directly corresponds to the resolution of each sample in a set of digital audio data....
 | Audio signal processing
Audio signal processing

Audio signal processing, sometimes referred to as audio processing, is the intentional alteration of sound Signal , or sound. As audio signals may be electronically represented in either digital or analog signal format, signal processing may occur in either domain....
 | Beat
Beat (acoustics)

In acoustics, a beat is an interference between two sounds of slightly different frequency, perceived as periodic variations in volume whose rate is the difference between the two frequencies....
s | Cycles
Cycle (music)

In music a cycle is a section_ which is Repetition or repeatable indefinitely, with the end of a preceding repetition leading to the beginning of a succeeding repetition....
 | Diffraction
Diffraction

Diffraction is normally taken to refer to various phenomena which occur when a wave encounters an obstacle. It is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings....
 | Doppler effect
Doppler effect

The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842, is the change in frequency and wavelength of a wave for an observer moving relative to the source of the waves....
 | Echo
Echo (phenomenon)

In audio signal processing and acoustics, an echo is a Reflection of sound, arriving at the listener some time after the direct sound. Typical examples are the echo produced by the bottom of a well, by a building, or by the walls of an enclosed room....
 | Music
Music

Music is an art form whose media is sound organized in time. Common elements of music are pitch , rhythm , dynamics , and the sonic qualities of timbre and texture ....
 | Note
Note

In music, the term note has two primary meanings: 1) a sign used in musical notation to represent the relative duration and pitch of a sound; and 2) a pitched sound itself....
 | Phonons | Physics of music | Pitch
Pitch (music)

Pitch represents the perceived fundamental frequency of a sound. It is one of the three major auditory system attributes of sounds along with loudness and timbre....
 | Psychoacoustics
Psychoacoustics

Psychoacoustics is the study of subjective human perception of sounds. Alternatively it can be described as the study of the psychological correlates of the physical parameters of acoustics....
 | Resonance
Resonance

In physics, resonance is the tendency of a system to oscillate at maximum amplitude at certain Frequency, known as the system's resonance frequencies ....
 | Rijke tube
Rijke tube

Rijke's tube turns heat into sound, by creating a self-amplifying standing wave. It is an entertaining phenomenon in acoustics and is an excellent example of resonance....
 | Reflection
Reflection (physics)

Reflection is the change in direction of a wavefront at an wiktionary:interface between two differentmedium so that the wavefront returns into the medium from which it originated....
 | Reverberation
Reverberation

Reverberation is the persistence of sound in a particular space after the original sound is removed. A reverberation, or reverb, is created when a sound is produced in an enclosed space causing a large number of Echo to build up and then slowly decay as the sound is absorbed by the walls and air....
 | Sonic weaponry
Sonic weaponry

Sonic and ultrasonic weapons are weapons of various types that use sound to injure, incapacitate, or kill an opponent. Some sonic weapons are currently in limited use or in research and development by military and police forces....
 | Sound localization
Sound localization

Sound localization is a listener's ability to identify the location or origin of a detected sound in distance and direction or the methods in acoustical engineering to simulate the placement of an auditory cue in a virtual 3D space ....
 | Soundproofing
Soundproofing

Soundproofing is any means of reducing the sound pressure with respect to a specified sound source and receptor. There are several basic approaches to reducing sound: increasing the distance between source and receiver, using noise barriers to block or absorb the energy of the sound waves, using damping structures such as sound baffles, or...
 | Timbre
Timbre

In music, timbre is the quality of a musical note or sound or tone that distinguishes different types of sound production, such as voices or musical instruments....
  | Ultrasound
Ultrasound

Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing . Although this limit varies from person to person, it is approximately 20 Hertz in healthy, young adults and thus, 20 kHz serves as a useful lower limit in describing ultrasound....
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