Audio signal
Encyclopedia
An audio signal is an analog
representation of sound
, typically as an electrical voltage
. Audio signals may be synthesized
directly, or may originate at a transducer
such as a microphone
, musical instrument
pickup
, phonograph
cartridge, or tape head
. Loudspeaker
s or headphones
convert an electrical audio signal into sound. Digital representations of audio signals exist in a variety of formats.
setting, where the signal flow is often very long and convoluted as the electric signal may pass through many sections of a large analog
console
, external audio equipment
, and even different rooms.
level in decibel
s (dB), and voltage level. The relation between power and voltage is determined by the impedance
of the signal path, which may be single-ended
or balanced
.
form, usually through the development of audio plug-ins for Digital Audio Workstation
(DAW) software such as Pro Tools
or Apple Logic, the terms audio signal and signal flow are also used to describe the path of digital information through the DAW (ie. from an audio track through a plug-in, sent a bus and an aux, and out a hardware output).
Digital audio signal being sent through wire can use several formats including optical (ADAT
, TDIF), coaxial
(S/PDIF
), XLR
(AES/EBU
), and ethernet
, especially for large digital mixing console
s.
Analog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
representation of sound
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, 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.-Propagation of...
, typically as an electrical voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
. Audio signals may be synthesized
Synthesizer
A synthesizer is an electronic instrument capable of producing sounds by generating electrical signals of different frequencies. These electrical signals are played through a loudspeaker or set of headphones...
directly, or may originate at a transducer
Transducer
A transducer is a device that converts one type of energy to another. Energy types include electrical, mechanical, electromagnetic , chemical, acoustic or thermal energy. While the term transducer commonly implies the use of a sensor/detector, any device which converts energy can be considered a...
such as a microphone
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
, musical instrument
Musical instrument
A musical instrument is a device created or adapted for the purpose of making musical sounds. In principle, any object that produces sound can serve as a musical instrument—it is through purpose that the object becomes a musical instrument. The history of musical instruments dates back to the...
pickup
Pickup (music technology)
A pickup device is a transducer that captures mechanical vibrations, usually from suitably equipped stringed instruments such as the electric guitar, electric bass guitar, Chapman Stick, or electric violin, and converts them to an electrical signal that is amplified, recorded, or broadcast.-...
, phonograph
Phonograph
The phonograph record player, or gramophone is a device introduced in 1877 that has had continued common use for reproducing sound recordings, although when first developed, the phonograph was used to both record and reproduce sounds...
cartridge, or tape head
Tape head
A tape head is a type of transducer used in tape recorders to convert electrical signals to magnetic fluctuations and vice versa.-Principles of operation:...
. Loudspeaker
Loudspeaker
A loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...
s or headphones
Headphones
Headphones are a pair of small loudspeakers, or less commonly a single speaker, held close to a user's ears and connected to a signal source such as an audio amplifier, radio, CD player or portable Media Player. They are also known as stereophones, headsets or, colloquially, cans. The in-ear...
convert an electrical audio signal into sound. Digital representations of audio signals exist in a variety of formats.
Signal flow
Signal flow is the term used to describe the path an audio signal will take from source (microphone) to the speaker or recording device. It is most frequently in a recording studioRecording studio
A recording studio is a facility for sound recording and mixing. Ideally both the recording and monitoring spaces are specially designed by an acoustician to achieve optimum acoustic properties...
setting, where the signal flow is often very long and convoluted as the electric signal may pass through many sections of a large analog
Analogue electronics
Analogue electronics are electronic systems with a continuously variable signal, in contrast to digital electronics where signals usually take only two different levels. The term "analogue" describes the proportional relationship between a signal and a voltage or current that represents the signal...
console
Mixing console
In professional audio, a mixing console, or audio mixer, also called a sound board, mixing desk, or mixer is an electronic device for combining , routing, and changing the level, timbre and/or dynamics of audio signals. A mixer can mix analog or digital signals, depending on the type of mixer...
, external audio equipment
Audio equipment
A piece of audio equipment is any device designed principally to reproduce, record or process sound. This includes microphones, radio receivers, AV receivers, CD players, tape recorders, amplifiers, mixing consoles, effects units and loudspeakers....
, and even different rooms.
Parameters
Audio signals may be characterized by parameters such as their bandwidth, powerElectric power
Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt.-Circuits:Electric power, like mechanical power, is represented by the letter P in electrical equations...
level in decibel
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
s (dB), and voltage level. The relation between power and voltage is determined by the impedance
Electrical impedance
Electrical impedance, or simply impedance, is the measure of the opposition that an electrical circuit presents to the passage of a current when a voltage is applied. In quantitative terms, it is the complex ratio of the voltage to the current in an alternating current circuit...
of the signal path, which may be single-ended
Single-ended signalling
Single-ended signaling is the simplest and most commonly used method of transmitting electrical signals over wires. One wire carries a varying voltage that represents the signal, while the other wire is connected to a reference voltage, usually ground....
or balanced
Balanced line
In telecommunications and professional audio, a balanced line or balanced signal pair is a transmission line consisting of two conductors of the same type, each of which have equal impedances along their lengths and equal impedances to ground and to other circuits. The chief advantage of the...
.
Digital equivalent
As much of the older analog audio equipment has been emulated in digitalDigital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
form, usually through the development of audio plug-ins for Digital Audio Workstation
Digital audio workstation
A digital audio workstation is an electronic system designed solely or primarily for recording, editing and playing back digital audio. DAWs were originally tape-less, microprocessor-based systems such as the Synclavier and Fairlight CMI...
(DAW) software such as Pro Tools
Pro Tools
Pro Tools is a digital audio workstation platform for Microsoft Windows and Mac OS X operating systems, developed and manufactured by Avid Technology. It is widely used by professionals throughout the audio industries for recording and editing in music production, film scoring, film, and television...
or Apple Logic, the terms audio signal and signal flow are also used to describe the path of digital information through the DAW (ie. from an audio track through a plug-in, sent a bus and an aux, and out a hardware output).
Digital audio signal being sent through wire can use several formats including optical (ADAT
ADAT
Alesis Digital Audio Tape or ADAT is a magnetic tape format used for the simultaneous digital recording of eight analog audio or digital audio tracks at once, onto a Super VHS tape that is used by consumer VCRs.- History :...
, TDIF), coaxial
Coaxial
In geometry, coaxial means that two or more forms share a common axis; it is the three-dimensional linear analogue of concentric.Coaxial cable, as a common example, has a wire conductor in the centre a circumferential outer conductor and an insulating medium called the dielectric separating...
(S/PDIF
S/PDIF
S/PDIF is a digital audio interconnect used in consumer audio equipment over relatively short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fiber optic cable with TOSLINK connectors. S/PDIF interconnects components in home theaters and other digital high...
), XLR
XLR connector
The XLR connector is a style of electrical connector, primarily found on professional audio, video, and stage lighting equipment. The connectors are circular in design and have between 3 and 7 pins...
(AES/EBU
AES/EBU
AES3 is the standard used for the transport of digital audio signals between professional audio devices. It is also known as AES/EBU and is published by the Audio Engineering Society and as part of IEC 60958. It was developed by the AES and the European Broadcasting Union and first published in...
), and ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
, especially for large digital mixing console
Digital mixing console
In professional audio, a Digital Mixing Console , is an electronic device for combining, routing, and changing the dynamics of digital audio samples. The digital audio samples are summed to produce a combined output. A professional digital mixing console is a dedicated desk or control surface...
s.
See also
- Analog audio
- Analog recordingAnalog recordingAnalog recording is a technique used for the recording of analog signals which among many possibilities include audio frequency, analog audio and analog video information for later playback.Analog recording methods store signals as a continual wave in or on the media...
- Audio signal processingAudio signal processingAudio signal processing, sometimes referred to as audio processing, is the intentional alteration of auditory signals, or sound. As audio signals may be electronically represented in either digital or analog format, signal processing may occur in either domain...
- Balanced audioBalanced audioBalanced audio is a method of interconnecting audio equipment using impedance-balanced lines. This type of connection is very important in sound recording and production because it allows for the use of long cables while reducing susceptibility to external noise.Balanced connections use...
- Communications
- Digital recordingDigital recordingIn digital recording, digital audio and digital video is directly recorded to a storage device as a stream of discrete numbers, representing the changes in air pressure for audio and chroma and luminance values for video through time, thus making an abstract template for the original sound or...
- Professional audioProfessional audioProfessional audio, also 'pro audio', refers to both an activity and a type of audio equipment. Typically it encompasses the production or reproduction of sound for an audience, by individuals who do such work as an occupation like live event support, using sound reinforcement systems designed for...