This problem is caused by the expansion and contraction of the dielectric element in some MLCCs, which causes the PCB to vibrate at the amplitude of the voltage applied. When the frequency of the voltage applied approaches audio frequencies, a noise can be heard.
Murata’s GJ8 series has been specially designed to reduce this problem and is available with capacitance between 1 and 10µF. The acoustic noise generated by 4.7 to 10µF GJ8 series capacitors represents an improvement of at least 10dB over ordinary MLCCs; for 1µF models the improvement is up to 30dB. The series is available in low-profile models with thicknesses of just 1.25, 1.60 or 2.50 mm depending on capacitance. Rated voltage is up to 50V.
