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 signals 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 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 such as a
microphone,
musical instrument pickup,
phonograph cartridge, or
tape head.
Loudspeakers 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 in a
storage device or
mixing console. It is used in operations such as
multi-track recording and
sound reinforcement.
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 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, and even different rooms.
Parameters
Audio signals may be characterized by parameters such as their
bandwidth,
nominal level,
power level in
decibels (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, known as ''mic level''.
Digital equivalent
The digital form of an audio signal is used in
audio plug-ins and
digital audio workstation (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,
coaxial and
twisted pair cable. A
line code 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,
TDIF,
TOSLINK,
S/PDIF,
AES3,
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.
See also
*
Analog recording
*
Audio editing software
*
Audio engineer
*
Audio signal processing
*
Digital recording
In digital recording, an audio signal, audio or video signal is converted into a stream of discrete numbers representing the changes over time in air pressure for audio, or Color, chroma and luminance values for video. This number stream is s ...
*
Equalization (audio)
*
Professional audio
*
Psychoacoustics
*
Sound intensity
*
Sound recording and reproduction
Sound recording and reproduction is the electrical, Mechanical system, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of ...
*
Stereophonic sound
*
Surround sound
References
External links
*{{Commons category-inline, Audio signal
Musical terminology
Sound production technology
Audio engineering