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Making fans quiet (was: DC power supplies)

Hi all,

With all this discussion about installing fans 
to cool down lighting hoods, and complaints 
about the high level of noise from these fans, 
I thought I'd tell about my recent experiences.

I've had a small 12 V DC, 1.5" diameter fan in my 
hood for some time. I chose it originally because
it was the quietest fan I could find. Unfortunately 
it has started to make quite a bit of noise recently. 
The bearings have probably become looser and 
this causes more vibration -> noise.

I removed the fan and ran it while holding it in my hand.
Lo and behold, the noise level was much lower! It is 
apparent that the big wooden box - my lighting 
hood - acts as a resonator, greatly amplifying the 
annoying noise. The fan was tightly screwed to the box, 
and this coupled the vibrational energy very efficiently 
to the hood.

I decided to try and use a method of attachment that 
would dampen the vibration. I found an old wristpad (the
kind used with computer keyboards to reduce wrist strain).
I cut a nice round piece from one end and drilled a 1.5" hole 
in it (the same diameter as the fan). I then attached the fan 
to this neoprene/foam "ring" using some tough sewing thread.
Then I just drove a couple of screws through the "ring"
to attach it to the hood (carefully aligning the fan with 
the hole in the wood). Voila! The difference is 
unbelieveable. Blissful silence!


ps. I got my fan from Radio Shack. I supply the power
to it with a 9 V DC/300 mA wallwart, also from Radio Shack.
The hood contains 2 x 40 W + 2 x 13 W compact fluorescents
(retrofit kits from AH supply). Ballasts mounted on the outside 
of the hood. Without a fan the heat buildup inside the hood
was unacceptable. The small fan keeps the inside of the hood
quite cool.

Mr.  I L K K A   K A L L I O
San Jose, CA