Proof? Don't need proof. You just spent about 400 USD on an LED. Do you really want to save an extra ten dollars on cheaper fans that are less effective? Risk v. Reward....
Wow, I was not expecting that. On the contrary flat9, we do need "proof" once you come in and drop a "bomb" like that. We're all working together here to try to figure out solid solutions for our problems. That comment right there is 100% counterproductive if not backed up.
First, we're looking at more expensive fans, certainly not cheaper
The laws of thermodynamics and mass production do not lie. Those fans were put in there because they are standard PC fans for the PC market for temps hitting to 100C. They are infinitesimally cheaper than any other. So you may only "need" as little as 1CFM, but the cost to fit custom ordered 1CFM fans is 100000x higher than cheapo standard off the shelf 50+ CFM fans. They are mass produced so cost effective, and that is what the sales folk want.
There are dozens of fanless LEDS out there, from costlier USA built outfits to chinese makes. The leds themselves are the "same" in general. The heat sinks are be much bigger (1 non standard heat sink cost lots more than a standard PC heatsink + standard fan)
We are not cooling CPU's. LED operating values are below 50C, so in essence, using standard heat sinks (which we are) we need a
maximum of 50% of "standards CFM rates" -
this is not science, its my own conjecture - I dont claim, I hypothesize.
Heat sinks transfer heat onto the air through
conduction, that just needs to get the heck out of there for full heat transfer to prevent thermal build-up through
convection.
Conduction depends on diferencial of temperature. Hot mas transfers to cold mass until equilibrium.(heat sink)
Convection on the other hand depends not on solids, but on density - and therefore subject to gravity. Cold air is more dense than hot air. So if you blow colder air into hotter air, the density will increase around the heat sink, thus increasing the heat transfer - but also until thermal equilibrium.
Once thing is to blow -20C into the LED light. certainly withing seconds any heat is dispersed. The efficiency of such transfer is right there! But if your tent is 50C+ ambient temp, you can have 100000 fans rated at 1000000 CFM blowing into your light and it will do zero for temp control.
Now obviously, the inverse is also valid. No fans, less continuous variable density potential, higher heat build up.
Take for example a tent with a HID light. You need a constant air flux OUT of tent to control the temperature. If you have a fan pointing at it there will be zero heat exchange once the tent hit its max ambient temperature, which will increase until the HID's actual operating temperature (burning hot!).
So
in theory as long as your tent is below 50C and there are fans exchanging heat from the unit at a speed of negative heat buildup, there should be no problem whatsoever.
So to answer your question on proof, if I had no serious problems with noise, I wouldn't even be here rambling. But since my grow op is indoors and the fan noise is really disrupting my girl's sleep (and who knows, neighbours?), I think the rewards of a properly thought out fan upgrade completely out-shadows any risks to my personal life.
This fanny talk is boring me now 
