background noise

English Thesaurus

1. extraneous noise contaminating sound measurements that cannot be separated from the desired signal (noun.event)

hypernym	:	background, background signal,
definition	:	extraneous signals that can be confused with the phenomenon to be observed or measured (noun.event)

hyponym	:	surface noise,
definition	:	noise produced by the friction of the stylus of a record player moving over the rotating record (noun.event)