Quiet fan for rack cooling installation?

Try http://www.activethermal.com/ for a variety of rack and equipment cooling systems. I have a 74" tall Mid Atlantic ERK 4025 rack in a closet and cool the whole space with a System 1. Have the fan unit 10 feet away in the basement and exhaust out to my garage. Only sound in the closet is the gentle whoosh of hot air being sucked away. With the doors closed, totally silent. They also make units that sit right on top of a hot piece of equipment. Nice folks, very helpful.

4" muffin fans & a Variac to reduce speed & noise works great. But SCR-based motor speed controllers produce tons of noise so definitely avoid them. Fixed power resistors are another way to reduce voltage / motor speed.

See www.tomshardware.com, www.anandtech.com, and www.directron.com for info. Directron has the actual db levels and cfm rates. Pabst fans are known to be very quiet.

Try Comair Rotron, Inc.'s "Whisper" fan product. I have a #027117 that runs on regular 115VAC. It is sealed ball bearing has 1600 RPM, 55 CFM of air movement, and an acoustic noise level of <30 dba. Several months ago I took it to radio shack and ran an A/B comparison of all their fans and the Rotron was the quietest by far. I checked out the quietpc.com web site and they do advertise for some quiet 12VDC fans, e.g. ~1700 RPM, for 20 -40 CFM with 20 dba. If that is enough air movement the price is right at quietpc. My rotron cost about $27.00.

Make sure to mount the fan on something that will isolate the vibration of the housing. I tried mounting the fan on a foam-rubber mouse pad and using rubber washers around the screws to mount it to my cabinet. The quietest, now don't laugh to loud, was to set the fan on top of a hockey puck and then place another on top of the unit. The isolation this provides results in a surprisingly quieter fan. Okay you can stop laughing now. Probably a baggie filled with sand or lead shot would do the same thing but the only thing I had laying around were the hockey pucks.

Try Comair Rotron, Inc.'s "Whisper" fan product. I have a #027117 that runs on regular 115VAC. It is sealed ball bearing has 1600 RPM, 55 CFM of air movement, and an acoustic noise level of <30 dba. Several months ago I took it to radio shack and ran an A/B comparison of all their fans and the Rotron was the quietest by far. I checked out the quietpc.com web site and they do advertise for some quiet 12VDC fans, e.g. ~1700 RPM, for 20 -40 CFM with 20 dba. If that is enough air movement the price is right at quietpc. My rotron cost about $27.00.

Make sure to mount the fan on something that will isolate the vibration of the housing. I tried mounting the fan on a foam-rubber mouse pad and using rubber washers around the screws to mount it to my cabinet. The quietest, now don't laugh to loud, was to set the fan on top of a hockey puck and then place another on top of the unit. The isolation this provides results in a surprisingly quieter fan. Okay you can stop laughing now. Probably a baggie filled with sand or lead shot would do the same thing but the only thing I had laying around were the hockey pucks.

Not sure if it would work but www.quietpc.com has some computer fans that are supposed to be quiet.

Try www.pcpowerandcooling.com that make some small fans that are about 20db and cost about 8 dollars each with free shipping. You will have to go to radioshack and buy an AC/DC convertor for about 29.00. The fan has a red wire and a black wire. The converter has matching connections. Run wire from the fan to the converter. If you need to cool other equipment, buy more fans as they only draw a little amount of current. I have 4 fans running off my convertor.

Try a small muffin fan from radio shack or some electronics supply house. They are pretty quiet, and made for cooling electronic equipment. They come is a variety of sizes, probably a 4" would be good for your application. You may have to run it off a wall-wart supply.