[SOLVED] How to decrease the buzz noise of the circuit board?

[D.A.(Tony)Stewart]

If you are only using "big" ceramic caps to suppress RF current, that ARE YOUR problem.. When we made 1GHz transceivers, the optimum lowest ESR cap 15 yrs ago was < 100pF. Your 22uF caps are behaving big resonant inductors> 1GHz, unless technology has changed significantly. Please verify the SRF of all parts in question.

 

[kayaoo]

It looks quite interesting. I guess you have tried to bypass the DC/DC or even the big capacitors and power the board externally but the sound remains unchanged.Is the board soldered or connected to some mother board? The small board should be resonating. I noticed that the board is quite hot. Is it possible that there are some conversion from heat to sound rather than from current to force to sound?

 

[tony_lth]

Hi, thanks all of you for your great help.
I have found the source of the problem. GE and SunnySkyguy are really right. That's the inductor problem, and that's also the big current sink.
Hi, I am very grateful for your help.

 

[D.A.(Tony)Stewart]

Saturation losses are too high.. Choose lower ET prouct. or get an inductor with lower losses, pref torroidal.