Noise
From Freepedia
In general usage, noise can be considered data without meaning; that is, data that is not being used to transmit a signal, but is simply produced as an unwanted by-product of other activities. In Information Theory, however, noise is still considered to be information.
When speaking of noise in relation to sound, what is commonly meant is meaningless sound of greater than usual volume. Thus, a loud activity may be referred to as noisy. However, conversations of other people may be called noise for people not involved in any of them, and noise can be any unwanted sound such as the noise of aircraft or road noise spoiling the quiet of the countryside.
Environmental noise is often measured using a weighting filter, most often A-weighting.
Industrial noise is often considered mainly from the point of view of environmental health as sustained exposure can cause permanent hearing damage. A-weighted measurements are commonly use for this to, and special exposure meters are available that integrate noise over a period of time to give an Leq value, defined by standards.
In audio, recording, and broadcast sytems noise refers to the residual low level sound (usually hiss and hum)that is heard in quiet periods of programme.
In video and television, noise refers to the random dot pattern that is superimposed on the picture as a result of electronic noise, the 'snow' that is seen with poor (analog) television reception or on VHS tapes.
See:
- Noise (environmental)
- Noise music
- Signal noise
- Noise (economic)
- ITU-R 468 noise weighting
- A-weighting
- Weighting filter
- Equal-loudness contour
See also: list of noise topics.
Unrelated to the preceding is Noise (Goidelic mythology)
