An audio signal is a representation of

sound In physics, sound is a vibration that propagates as an acoustic wave through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the br ...

, typically using either a changing level of electrical

voltage Voltage, also known as (electrical) potential difference, electric pressure, or electric tension, is the difference in electric potential between two points. In a Electrostatics, static electric field, it corresponds to the Work (electrical), ...

for

analog signal An analog signal (American English) or analogue signal (British and Commonwealth English) is any continuous-time signal representing some other quantity, i.e., ''analogous'' to another quantity. For example, in an analog audio signal, the ins ...

s or a series of binary numbers for

digital signal A digital signal is a signal that represents data as a sequence of discrete values; at any given time it can only take on, at most, one of a finite number of values. This contrasts with an analog signal, which represents continuous values; ...

s. Audio signals have frequencies in the

audio frequency An audio frequency or audible frequency (AF) is a periodic vibration whose frequency is audible to the average human. The SI unit of frequency is the hertz (Hz). It is the property of sound that most determines pitch. The generally accepted ...

range of roughly 20 to 20,000 Hz, which corresponds to the lower and upper limits of human hearing. Audio signals may be synthesized directly, or may originate at a

transducer A transducer is a device that Energy transformation, converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation, M ...

such as a

microphone A microphone, colloquially called a mic (), or mike, is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and publi ...

, musical instrument pickup, phonograph cartridge, or

tape head ''Tape Head'' is the seventh studio album by American rock band King's X, released in 1998 via Metal Blade Records. A music video was made for the song "Fade". "World" is a reworked song from the band's ''Sneak Preview'' demos. The controv ...

Loudspeaker A loudspeaker (commonly referred to as a speaker or, more fully, a speaker system) is a combination of one or more speaker drivers, an enclosure, and electrical connections (possibly including a crossover network). The speaker driver is an ...

s or

headphones Headphones are a pair of small loudspeaker drivers worn on or around the head over a user's ears. They are electroacoustic transducers, which convert an electrical signal to a corresponding sound. Headphones let a single user listen to an ...

convert an electrical audio signal back into sound.

Digital audio Digital audio is a representation of sound recorded in, or converted into, digital signal (signal processing), digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical sampling (signal processing), ...

systems represent audio signals in a variety of digital formats.Hodgson, Jay (2010). ''Understanding Records'', p.1. . An audio channel or audio track is an audio signal

communications channel A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for inform ...

in a storage device or

mixing console A mixing console or mixing desk is an electronic device for Audio mixing (recorded music), mixing audio signals, used in sound recording and reproduction and sound reinforcement systems. Inputs to the console include microphones, signals fro ...

. It is used in operations such as

multi-track recording Multitrack recording (MTR), also known as multitracking, is a method of sound recording developed in 1955 that allows for the separate recording of multiple sound sources or of sound sources recorded at different times to create a cohesive who ...

and

sound reinforcement A sound reinforcement system is the combination of microphones, signal processors, amplifiers, and loudspeakers in enclosures all controlled by a mixing console that makes live or pre-recorded sounds louder and may also distribute those sou ...

Signal flow

Signal flow Audio signal flow is the path an audio signal takes from source to output. The concept of audio signal flow is closely related to the concept of audio gain staging; each component in the signal flow can be thought of as a gain stage. In typical ...

is the path an audio signal will take from source to the speaker or recording device. Signal flow may be short and simple as in a

home audio Home audio refer to audio consumer electronics designed for home entertainment, such as integrated systems like shelf stereos, as well as individual components like loudspeakers and surround sound receivers. The evolution of home audio began ...

system or long and convoluted in a

recording studio A recording studio is a specialized facility for Sound recording and reproduction, recording and Audio mixing, mixing of instrumental or vocal musical performances, spoken words, and other sounds. They range in size from a small in-home proje ...

and larger sound reinforcement system as the signal may pass through many sections of a large mixing console, external

audio equipment Audio equipment refers to devices that reproduce, record, or process sound. This includes microphones, radio receivers, AV receivers, CD players, tape recorders, amplifiers, mixing consoles, effects units, headphones, and speakers. Audio equip ...

, and even different rooms.

Parameters

Audio signals may be characterized by parameters such as their bandwidth,

nominal level Nominal level is the operating level at which an electronic signal processing device is designed to operate. The electronic circuits that make up such equipment are limited in the maximum signal they can handle and the low-level internally genera ...

, power level in

decibel The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a Power, root-power, and field quantities, power or root-power quantity on a logarithmic scale. Two signals whos ...

s (dB), and voltage level. The relationship between power and voltage is determined by the impedance of the signal path. Signal paths may be single-ended or balanced. Audio signals have somewhat standardized levels depending on the application. Outputs of professional mixing consoles are most commonly at

line level Line level is the specified Audio power, strength of an audio signal used to transmit analog (signal), analog sound between audio components such as compact disc, CD and Digital Versatile Disc, DVD players, television sets, audio amplifiers, and ...

. Consumer audio equipment will also output at a lower line level. Microphones generally output at an even lower level, known as ''mic level''.

Digital equivalent

The digital form of an audio signal is used in

audio plug-in An audio plug-in, in computer software, is a Plug-in (computing), plug-in that can add or enhance audio-related functions in a computer program, typically a digital audio workstation. Such functions may include digital signal processing or soun ...

s and

digital audio workstation A digital audio workstation (DAW ) is an electronic device or application software used for Sound recording and reproduction, recording, editing and producing audio files. DAWs come in a wide variety of configurations from a single software pr ...

(DAW) software. The digital information passing through the DAW (i.e. from an audio track through a plug-in and out a hardware output) is an audio signal. A digital audio signal can be sent over

optical fiber An optical fiber, or optical fibre, is a flexible glass or plastic fiber that can transmit light from one end to the other. Such fibers find wide usage in fiber-optic communications, where they permit transmission over longer distances and at ...

coaxial In geometry, coaxial means that several three-dimensional linear or planar forms share a common axis. The two-dimensional analog is ''concentric''. Common examples: A coaxial cable has a wire conductor in the centre (D), a circumferential ou ...

and

twisted pair Twisted pair cabling is a type of communications cable in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted balanced ...

cable. A

line code In telecommunications, a line code is a pattern of voltage, current, or photons used to represent digital data transmission (telecommunications), transmitted down a communication channel or written to a storage medium. This repertoire of signal ...

and potentially a

communication protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any variation of a physical quantity. The protocol defines the rules, syntax, semantics (computer science), sem ...

are applied to render a digital signal for a transmission medium. Digital audio transports include

ADAT Alesis Digital Audio Tape, commonly referred to as ADAT, is a magnetic tape format used for the Sound recording and reproduction, recording of eight digital audio tracks onto the same S-VHS tape used by consumer VCRs, and the basis of a serie ...

, TDIF, TOSLINK,

S/PDIF S/PDIF (Sony/Philips Digital Interface) is a type of digital audio interface used in consumer audio equipment to output audio over relatively short distances. The signal is transmitted over either a coaxial cable using RCA connector, RCA or BN ...

AES3 AES3 is a technical standard, standard for the exchange of digital audio signals between professional audio devices. An AES3 signal can carry two channels of pulse-code modulation, pulse-code-modulated digital audio over several transmission medi ...

, MADI,

audio over Ethernet In audio engineering, audio and broadcast engineering, broadcast engineering, Audio networking is the use of a Computer networking, network to distribute real-time digital audio. Audio Networking replaces bulky snake cables or audio-specific insta ...

and

audio over IP Audio over IP (AoIP) is the distribution of digital audio across an IP network such as the Internet. It is used increasingly to provide high-quality audio feeds over long distances. The application is also known as audio contribution over IP (ACI ...

References

External links

*{{Commons category-inline, Audio signal Musical terminology Sound production technology Audio engineering

Signal flow

Parameters

Digital equivalent

See also

References

External links