Filter capacitor is one of the main noise sources at DC converter substation.To separate and identify noise magnitude and its frequency component from coherent acoustic field of complicated converter station at normal operation of filter capacitor is of great importance to the simulation and loading of noise testing of capacitor unit and noise prediction and control of filter field of converter station.It is shown by that the study that adoption of noise-vibration coherent separation method can eliminate the interference of other noise resources on the noise component of capacitor

thus separate site operation noise from capacitor.It is shown by the tested and separated result that the noise generated by capacitor from site of certain converter station has clear directivity and the noise level 1 meter away from the side of bush of capacitor unit is 55.6dB（A）.Operation noise of capacitor is distributed mainly within the frequency range from 100 Hz to 2 400 Hz

and is the high harmonic component with 100 Hz as the fundamental frequency and the high harmonic noise is bigger around 600 Hz.It is also found by the study that when current of multiple frequency is input into capacitor

the radiation noise increases suddenly

thus occurring so-called multifrequency noise jump phenomena.