Signal-to-noise ratio Signal-to-noise ratio (often abbreviated SNR or S/N) is defined as the ratio of a signal power to the noise power corrupting the signal. The higher the ratio, the less obtrusive the background noise is. Originally from the CUAHSI HIS VariableNameCV. See: http://his.cuahsi.org/mastercvreg/edit_cv11.aspx?tbl=VariableNameCV. ODM2 Variable Name Controlled Vocabulary ODM2 Working Group A vocabulary for describing the name of Variables.