[sdiy] Microphonics

[rburnett at richieburnett.co.uk]

>> The author meant “bucks” which is what dollars are often called.

I was more concerned about this comment!!!...

>> ...other weirdness ensued but we got the customer taken care of.  :-O

If the integrator capacitor in the VCO is piezoelectric then it will 
generate a force that is exerted on the PCB when it charges and 
discharges.  This alternating force will then excite various mechanical 
resonances in the surrounding PCB.  (The PCB will move more air than the 
tiny capacitor alone so it will probably just sound like the PCB is 
making the whining noise.)  Also, a mechanically flexing PCB will exert 
a force on the capacitor resulting in electricity being generated in the 
capacitor due to the piezoelectric effect.  So this has the potential to 
mess up the electrical operation of your precision VCO.  I would expect 
that the operation of the circuit will begin to be influenced to some 
extent by the mechanical resonant modes of the PCB!

-Richie,