The Nature of Noise
The idea of noise plays a prominent (if subsiduary) part in many fields of study; it is casually mentioned in numerous papers as if its nature was well established. However to a large extent the term is not examined, but simply used. In other words, it has become part of the practice of science without entering to a significant extent as part of its explicit theory .
The Oxford English Dictionary presents the following account (after a list of descriptions of more mundane uses referring to the older, non-technical uses of the word noise):
“11. a. In scientific and technical use: random or irregular fluctuations or disturbances which are not part of a signal (whether the result is audible or not), or which interfere with or obscure a signal; oscillations with a randomly fluctuating amplitude over a usually continuous range of frequencies. Also in extended use: distortions or additions which interfere with the transfer of information.…
b. In non-technical contexts: irrelevant or superfluous information or activity, esp. that which distracts from what is important.”
Thus we have a veritable “hairball” of related ideas, including: randomness; irregularity; disturbance; interference; obscuration; non part of a signal; distortion; addition; irrelevance; superfluity; and distraction applying to either a signal or to “what is important”. I think this accurately represents the term as it is used in technical papers (both in terms of content and in its vagueness). I this paper I try to produce a clearer and more coherent account of the term – an account that moves towards a more general theory of noise.<>I start with a picture of noise from electrical engineering, since this seems to be where the concept arose first in academic papers and so frames much of the scientific thinking on the subject. I then generalise this picture to the widest conception: that of noise as what is unwanted, which relates to our aural experience. A closely related conception that has developed in the scientific literitature is noise as what is unexplained – the residual after what can be explained (or modelled) is factored out. A particular case of this later usage is where a source of randomness can be used to stand-in for this residual. This strategy has lead some to almost identify hoise and randomness. However I argue that noise and randomness are not the same and thoughtlessly conflating them can result in misleading assumptions. I explore the possible relation between noise and context, and propose a new conception of noise, namely that noise is what can result from an extra-contextual signal. I claim that this is not only a pschologically plausible account of its origin (an hence relates well to common usage) but is also a useful way of conceputalising it. I finish with an application of the analysis of noise to the relation of determinism and randomness.