Abstract: Electrical noise is suppressed on an input signal by squaring the input signal and any noise thereon, removing the sinusoidal terms in the squared output (as by averaging), subtracting the d.c. noise component, and taking the square root of the remainder, so as to produce an r.m.s. dependent, substantially noise free output. If desired, the noise suppression circuitry may be combined in a low signal measuring instrument in which the input signal is repetitively sampled and freed of noise in the manner described, the output then being measured on a d.c. meter.