Different noise character in identical fans (Gentle Typhoon)

[fwiffo]

I just picked up and installed a couple 1450 RPM Gentle Typhoons (turned down with a controller) to replace the stock 120mm fans in my case and on my CPU cooler. It seems like one of them is considerably noisier than the other.

The one mounted to my case becomes really damn hard to hear below 1100 RPM. It just disappears. The one mounted on my CPU heat-sink has a drone that is audible at much lower RPMs. I'd say it has the tonal character of a tornado siren, though very very quiet. Is that the "unique" sound that people say these fans have? The case one also makes that noise, but only at higher RPM or when it's changing speed.

Is it just that fan is not quite as good as the other? Is it because of the impedance of the heat sink? Is the heat-sink acting like a tuning fork? Is its position in the middle of the case allowing for more resonance with the air in the case?

If it's the fan, I might swap the position of the two because I think I can get away with lower RPMs on the case fan temperature-wise.

Granted, it's by no means loud. I mean, I only actually hear when I'm sitting at my desk it if my AC and fridge and water cooler all manage to shut up at the same time, and there's no traffic, and I'm not typing or mousing and I'm trying to listen for it... Even then it's competing with the sound of blood rushing through my ears... So I might be being obsessive.

And holy crap, no matter how quiet I get my other fans, I still can't pick out the fan in my Nexus Value 430 - what is in that thing?

[b_rubenstein]

You can't tell much about the fans once they are mounted.

Take them both out, sit them on edge, on a table and power them up with 12v. If one is louder than the other, it's probably vibration; look run out around the hub.

[flemeister]

Aww, where's your experimenting spirit?

Remove both fans from case, fire them up and listen carefully for any noise difference.

Perhaps the fan that's on the CPU heatsink is vibrating a little more than the other, since it's hard mounted on the heatsink?

[fwiffo]

Oh, yeah, I guess I should probably do that. I just don't have the energy for repeatedly cracking my case open that I did when I was a young man.

My processor is running reasonably cool, maybe I can just turn them really really low. How far below TJ (or whatever) do people like to stay?

[KayDat]

I'd say its the HS causing turbulence or something. For example, I've heard two identical fans placed in front and behind a tower HS have very different noise profiles when run independently of each other.

[themaster1]

It seems like one of them is considerably noisier than the other.

The one mounted to my case becomes really damn hard to hear below 1100 RPM. It just disappears. The one mounted on my CPU heat-sink has a drone that is audible at much lower RPMs. I'd say it has the tonal character of a tornado siren

I have experimented with fans the previous weeks and i'd say your fan is defective a good fan should work ok (=less noise) when it's undervolted.

But to make the comparison you must be sure all the fans use the same technology: ball-bearing, sleeve bearing, sso bearing or hydraulic bearing.
Hydraulic bearing is supposedly the best type of bearing but guess what i tried my old cpu fan which turns out to be a hydraulic bearing and it make more noise even with a LNA cable + undervolted .

[fwiffo]

The noise does decrease at lower voltages, it just remains audible at lower RPMs than the other fan. It's by no means loud. I was just asking if it was likely that the two fans sounded significantly different because of their respective locations.

When I get time I am going to try to see if they sound different when removed from the case.

But to make the comparison you must be sure all the fans use the same technology: ball-bearing, sleeve bearing, sso bearing or hydraulic bearing.

The fans are identical models and were purchased at the same time.

[ascl]

Its definitely possible. Once you have determined if they sound the same outside of any mounting (ie outside the case), you can determine if one or both need to be de-coupled from the case. Its possible they are causing vibrations which make them sound louder. Its also possible that the sound of the air rushing through the heatsink fins makes it louder as well.


You may find that soft mounting the fan makes a big difference. But really, first thing you need to do is work out if you have a faulty fan or not.

[fwiffo]

I took the fans out of the case, and they were indistinguishable from one another. They even spun down exactly the same when I turned off the power. It was like two synchronized swimmers. Almost like creepy twins. And they took forever to spin down - the bearings must be very well balanced. Near as I can tell, it's the air blowing through the heat-sink that's causing the noise; maybe it's acting a bit like a harmonica or something. The fans by themselves do have a similar kind of hum, but I have to have my ears like two inches away at that speed to hear it over the normal fan/turbulence noise.

Anyhow, it's not loud enough to bother me at this point. I might be able to minimize it by playing with the fan controller a little more.

[ascl]

Try mounting the fan with some rubber separating it from the heat sink. It might reduce the amount the heat sink is vibrating (assuming its not just air noise).

Also, its entirely possible you will be able to run the fan at a slower speed than previously, as the GTs are good at pushing air through restrictions. So monitor temps rather than fan speed.

Hope this helps!

EDIT: I noticed you asked about how far below TJmax should you stay... its a good question, and there isn't really a "right" answer. Some people say as long as you don't throttle, and others opt for 20-30c at full load. Personally, I'd aim for 15-20c distance to TJ on the hottest day of the year.... thats probably overly cautious, especially as nothing really heats up a CPU like prime95. So on a normal day, my CPU max out at about 40c to TJ. YMMV of course.

[fwiffo]

Actually, the heat-sink's bracket (CM Hyper 212+) has little rubber pads already.

I'm like 30-40 under TJ max under load right now, so I guess I can turn these babies down a bit further still. The room is air-conditioned (more or less a necessity in Florida just to keep the mold at bay), so I guess that makes it easier.

[ascl]

Is the clip tight? Can you wriggle the fan when its attached? If so, it could still be vibrating.

Read my previous post about temps

[fwiffo]

Yeah, it's on there good and tight. It's sounds like a siren or a whistle, so I'm guessing it is some kind of resonance or harmonica effect.

Trust me when I say I'm being picky. The fans are really very quiet.

[ascl]

Nothing wrong with being picky But yeah, in my experience these fans are great quality, am very impressed with them.