refers not simply to audible sound but rather to any undesired information in a communication channel which is not part of the intended message. Thus, smudges on a printed page, static on a radio, "ghosts" on a television can be interpreted as noise according to this definition. Because noise is an evaluative term, it occurs only in the receiver. The channel does not know the difference. (
Umpleby )
Unexplained
variation in a communication
channel, random error in the transmission of
information. Noise is not merely auditory as in the static on radio but may also be visual as in a blurred picture. It may occur in any
measurement process where one differentiates between related and unrelated variance , the latter being noise. The analogy between noise and
thermodynamic entropy is suggested by the
fact that in any
communication process, noise can only increase and it does so at the expense of the amount of information transmitted from a sender to one or more receivers.
information theory quantitatively decomposes the receivers'
statistical entropy into a quantity of transmitted information and the quantity of noise. Noise is the logical complement of
equivocation and undesirable from the receiver's perspective. (
Krippendorff )
