Problem: Low frequency rumble

[mgpaulus]

I have a Generic ATX Midtower case that has 1 intake fan, the PSU fan, and a CPU fan. In the interests of quieting that thing down, I replace the PSU fan with a Panaflo L1A, I put a PC Power & Cooling Silencer fan on the intake, and replaced the stock Intel HS/F with a Taisol CGK760092 and a Panaflo L1A on the Heatsink via 60->80mm adapter. It sure quieted everything down, except for one small problem. I now have a low frequency "rumble", that can be heard in other parts of the house. Kind of annoying for a "quiet" machine.

Any thoughts?

Jetway Socket 370 Board (generic)
Intel Celeron 850@935 / Taisol CGK760092 / Panaflo L1A
20GB IBM EIDE ATA/66
Jaton GF2/MX / Tennmax Lasagna B
3COM 3C905
Sound Blaster 128/PCI

Thanks.

 

[Underclocked]

Sound coming from the psu? What kind/wattage is it? Did you do any 7v rewires on the fans? Is the case sitting on a solid surface or something like carpet? Maybe one of these questions will lead to the answer. ???

 

[mgpaulus]

The PSU is a LK 400 Watt ATX PSU, which I swapped out the original fan for a Panaflo L1A.
No 7V wiring on any of the Fans, that I know of. The PSU rewire was a straight snip & tape job.
The HS/F Panaflo is plugged into the MoBo Header, and the Silencer is connected via 4 pin molex.

The Computer is sitting on carpet under a desk. If you hit my sig, and check out the Rig Pics, you
can see a picture of where it is located. The system I am referring to is the Kids Computer.

I am planning on doing some similar work to my main system, but I would like to figure this one out
first.

 

[Underclocked]

You could certainly rule out the fans by leaving them unpowered BRIEFLY. What do you mean by snip and tape? My guess is your noise is coming from that psu and not a fan. Got a spare PSU? That one seems like overkill for that system.

 

[SWScorch]

One of your fans might be a little loose, causing it to vibrate against the case. Recheck all the screws and make sure they are tight. Like Underclocked said, deactivate the fans for a brief amount of time to see if the noise is abated.

 

[mgpaulus]

Thanks all, will give those suggestions a try. snip & tape means, I cut the fan leads from the original PSU fan, stripped and twisted on the wires from the panaflo, and then electrical taped them for insulation & strength. I have soldered them in the past, but didn't really feel it was necessary.

 

[Jhhnn]

If the level rises and falls rhythmically over an interval of a few seconds, it's a harmonic vibration. All the different vibrational peaks come together on a regular basis, at a much lower frequency than any of the separate sources. Then the case starts singing in harmony....

Might try switching the silencer and one panaflo around, mounting the case fans on grommets, or applying some vibration damping material to the case. Sometimes something as simple as wedging some cardboard between the motherboard plate and the case panel will kill the noise, sometimes it's hell to get rid of....

 

[fast_eddie]

mgpaulus;
Is there any chance that the speaker system might be the cause of the rumble? (i.e. is the rumble present with the sound system off)

 

[mgpaulus]

fast_eddie: I'm pretty sure it's a case vibration somewhere. I was looking into the case last night with a flashlight, and I happened to touch the flashlight to the case (Was "peering" through the holes in the back). When I touched the case with the flashlight, the noise seemed to dampen slightly. So, I guess it's back to pulling the case off & making sure everything is tight.... I might look into some rubber grommets too. Taking off the power for the CPU fan is a bear because the fan header is sandwiched between the Socket & PSU, and with that oversized Taisol on there, it's a real tight squeeze. Last time I used 6" needle nose pliers, and still could barely reach (The handles got in the way. What I need are some doctors tools, I guess).

I'm using this case as a playground to figure out how to quiet my other case. It's the noisy one, but this one was pretty bad also. Now it's better, except for this low bass noise.

 

[MoFunk]

Here is something I plan on trying soon! Linky