The Nature of Noise

By: Bruce Edmonds
Date: 25th October 2005
CPM Report No.: CPM-05-156

Presented at EPOS  2006, Epistemological Perspectives on Simulation  -  II Edition, University of Brescia, Italy - 5th-6th October 2006.

Published as: Edmonds, B. (2009) The Nature of Noise. In Squazzoni, F. (Ed.) Epistemological Aspects of Computer Simulation in the Social Sciences. LNAI 5466:169-182.


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.

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