In the second harmonic type magnetic modulators, the origin of noise is thought mainly to be from Barkhausen jumps. In this paper we describe one method of noise reduction. By using two frequency excitation, one (f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> ) at about 3 kHz, and the other (f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ) higher by several hundred kHz, we observed considerable decrease of noise, about 1/10 of that of ordinary magnetic modulators with one frequency excitation. The mechanism of noise reduction was explained by solving the equation of wall motion when passing through the potential barriers in magnetic cores. The results obtained from our experiments are as follows. 1) At optimum frequency, decrease of noise is maximum. 2) With application of second high frequency excitation f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , signal to noise ratio increases. 3) The larger the amplitude of second frequency excitation, the lower the noise. 4) The effect of second frequency excitation on long time drift is small. The excitation source of f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> may be a conventional one, and the distortion of its waveform is not a serious condition.