To the archaeo-geophysicist the signal is the object of the survey while noise is everything else that is measured, and considered to offer no useful information.

One project's signal may be another's noise, however.

• Iron debris and litter that frequently inhabits the ground may be a nuisance to the measurement of subtle soil changes in a prehistoric site through magnetic or EM surveys.
• That very iron litter may represent important targets on an historic period site, pointing to significant artifacts, dumping areas, or the locus of former wooden structures that employed nails in their construction.

One goal of geophysical practice is to improve the signal-to-noise ratio.

In some types of geophysical surveys variations in background noise are important, as in total field magnetic surveys where daily field variations must be monitored.

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