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 ...

, typically using either a changing level of electrical

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...

for analog signals, or a series of

binary numbers A binary number is a number expressed in the base-2 numeral system or binary numeral system, a method of mathematical expression which uses only two symbols: typically "0" (zero) and "1" (one). The base-2 numeral system is a positional notation ...

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; a ...

s. Audio signals have frequencies in the audio frequency 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 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, measurement, and con ...

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 publ ...

, musical instrument pickup,

phonograph cartridge A phonograph, in its later forms also called a gramophone (as a trademark since 1887, as a generic name in the UK since 1910) or since the 1940s called a record player, or more recently a turntable, is a device for the mechanical and analogu ...

, or tape head.

Loudspeaker A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or ...

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 a ...

convert an electrical audio signal back into sound.

Digital audio Digital audio is a representation of sound recorded in, or converted into, digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical samples in a continuous sequence. For example, in CD audio, samp ...

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 in a storage device or mixing console, used in operations such as multi-track recording 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 sounds ...

Signal flow

Signal flow 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 system or long and convoluted in a

recording studio A recording studio is a specialized facility for sound recording, mixing, and audio production of instrumental or vocal musical performances, spoken words, and other sounds. They range in size from a small in-home project studio large enou ...

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 ...

, and even different rooms.

Parameters

Audio signals may be characterized by parameters such as their bandwidth, nominal level, 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 or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a ...

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. Consumer audio equipment will also output at a lower line level. Microphones generally output at an even lower level, commonly referred to 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 that can add or enhance audio-related functionality in a computer program. Such functionality may include digital signal processing or sound synthesis. Audio plug-ins usually provide their ...

s and

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

(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 in Commonwealth English, is a flexible, transparent fiber made by drawing glass ( silica) or plastic to a diameter slightly thicker than that of a human hair Hair is a protein filament that grows ...

, coaxial and

twisted pair Twisted pair cabling is a type of wiring used for communications 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 b ...

cable. A

line code In telecommunication, a line code is a pattern of voltage, current, or photons used to represent digital data transmitted down a communication channel or written to a storage medium. This repertoire of signals is usually called a constrained ...

and potentially a communication protocol are applied to render a digital signal for a transmission medium. Digital audio transports include

ADAT Alesis Digital Audio Tape (ADAT) is a magnetic tape format used for the recording of eight digital audio tracks onto the same S-VHS tape used by consumer VCRs. Although it is a tape-based format, the term ''ADAT'' now refers to its succ ...

, TDIF, TOSLINK, S/PDIF, AES3,

MADI Madi may refer to: Places * Madi, Chitwan, a municipality in Chitwan District in Nepal * Madi Municipality, Sankhuwasabha, a municipality in Sankhuwasabha District in Nepal * Madi Rural Municipality, Rolpa, a rural municipality in Rolpa Distric ...

audio over Ethernet In audio and broadcast engineering, Audio over Ethernet (sometimes AoE—not to be confused with ATA over Ethernet) is the use of an Ethernet-based network to distribute real-time digital audio. AoE replaces bulky snake cables or audio-specific ...

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