Noise (audio)
3339064
59487178
2006-06-19T19:21:01Z
CmdrObot
1079367
sp: sytems→systems
'''Noise''' in audio, recording, and broadcast systems refers to the residual low level sound (usually hiss and hum) that is heard in quiet periods of a programme.
In [[audio engineering]] it can refer either to the acoustic noise from loudspeakers, or to the unwanted residual electronic noise signal that gives rise to acoustic noise heard as 'hiss'. This signal noise is commonly measured using [[A-weighting]] or [[ITU-R 468 noise weighting|ITU-R 468 weighting]]
Noise is often generated deliberately and used as a [[test signal]]. Two types of deliberately generated noise in common use are referred to as '[[white noise]]', which has a uniform [[spectral power density]] at all frequencies, or '[[pink noise]]' which has a power [[spectral density]] that falls at 3dB/octave with rising frequency. The latter is often more useful in audio testing because it contains constant energy per octave (and hence per commonly used 1/3rd octave), rather than a prepondance of energy at high frequencies. In other words it contains energy that is destributed geometrically rather than linearly.
== See also ==
*[[Noise]]
*[[Noise measurement]]
*[[ITU-R 468 noise weighting]]
*[[A-weighting]]
*[[Weighting filter]]
*[[Equal-loudness contour]]
== External links==
*[http://www.sengpielaudio.com/calculator-noise.htm White noise calculator, thermal noise - Voltage in microvolts, conversion to noise level in dBu and dBV and vice versa]
[[Category:Noise|Audio]]
[[Category:Sound]]