fan mounting and noise pickup

evening all, hope all is well.

i have a, i hope, simple question regarding mounting fans to heat-sinks and in turn the vibration being picked up from a elec. mic

i am using a combo 5v/12v regulator setup with the 12v being boosted from a 2955 on one board. (not quite up to speed with smp's yet) lm386 mic pre-amp on a 2nd board with a mono tda2050 amp setup

boards mounted to 3/4 plywood with foam gasket underneath

the mic is picking up the vibration from the fan. i believe it is vibration noise anyway. i can disconnect the fan and all is well except unit get a little warm. i can hold onto fan tightly and it seems to diminish somewhat tried moving further away but still mounted to same board, same thing i added foam underneath boards thinking it would help deaden the vibration noise. i added some phish paper between fan and heat-sink to help minimize vibration also. should i try foam instead???

if anyone has more suggestions or corrections for me to try, i am open for ideas.

Whst is the mic for?

First of all, all fans are not created equal. The noise level or even more importande the noise/flow ratio varies from model to model. Do some research and fin a quite one. A good flow/noise ratio also lets you lower the voltage and thus the rpm. Thirdly good uality fans do often come with rubber mounts to absorb vibration. If all this does not help go for a larger fan with even lower rpm or get a alrger heatsink and get rid of the fan altogether

Whst is the mic for?

im using mic for ambient noise for vu meter. (i think it's a pretty kick A$$ for simple design from datasheet)

A good flow/noise ratio also lets you lower the voltage and thus the rpm.

so if i lower voltage, within reason, that may help correct??? it shouldn't screw with regulator??? the fan IS already pretty quiet cause i can't hear it running being next to it.

am i correct to think it is vibration or can it be something different???

oh, by the way, thank you :)