[Amps] Subject: Re: Holes vs. screen for chassis ventilation?

[James Irving]

American Science and Surplus sells stainless steel screening that is used for holding flasks over Bunsen burners.  Cost is 2$US for a 6x6inch piece, but this should be available from any chemistry supply house.  It looks very good when used to cover a "passive" vent that is visible.  

However, if used to covering fan driven intake or exhaust ports, it will whistle or have a loud "rushing" sound.  This would probably happen with any screen whose holes were less than 1/8 inch. I've used it to cover "passive" vents in a number of computers; it's tough stuff that looks good and really helps to tame computer RFI.  If your going to use a screen type material with a fan, test it first.  Blower noise is bad enough, but fan noise with a whistle will drive you up the wall!

Hardware cloth or thicker aluminum venting material shouldn't have the "noise" problem.

Jim K9JFK