In science, and especially in physics and telecommunication, noise is random fluctuations and the addition of external factors to the stream of target information (signal) being received at a detector.

More specifically, in physics, the term noise has the following meanings:

1. An undesired disturbance within the frequency band of interest; the summation of unwanted or disturbing energy introduced into a communications system from man-made and natural sources.

2. A disturbance that affects a signal and that may distort the information carried by the signal.

3. Random variations of one or more characteristics of any entity such as voltage, current, or data.

4. A random signal of known statistical properties of amplitude, distribution, and spectral density.

5. Loosely, any disturbance tending to interfere with the normal operation of a device or system.

Some sections copied from Federal Standard 1037C and from MIL-STD-188

See also: