silence?

I have a constant loud hum from my PC. I had to try out my PSU on a mates
computer and with his O/B graphics there little or no sound. I thought it
must be graphics card as the Mobo is passively cooled and the CPU has an
Arctic Cooler Freezer 64 Pro.
i duly went and bought an S2 Accellero passive cooler and fitted it but the
sound is just as loud as before.
Why is this so? My vga card is an ATI x850XT PE (now passively cooled) and
is this drawing enough power from the PSU to create this loud hum.
TIA
Robin

Robin Gordon wrote:
> I have a constant loud hum from my PC. I had to try out my PSU on a
> mates computer and with his O/B graphics there little or no sound. I
> thought it must be graphics card as the Mobo is passively cooled and the
> CPU has an Arctic Cooler Freezer 64 Pro.
> i duly went and bought an S2 Accellero passive cooler and fitted it but
> the sound is just as loud as before.
> Why is this so? My vga card is an ATI x850XT PE (now passively cooled)
> and is this drawing enough power from the PSU to create this loud hum.
> TIA
> Robin

A loud hum can be resonance. For example, if the side panel on my computer
is not completely seated, the side starts to rattle a bit.

If you take the side off the computer case, you can try listening to the
fans while the computer is running. Carefully sticking a finger on the hub
of each fan, and applying just a little friction, should cause that fan
to change speed a bit. See if the irritating sound stops or changes pitch
when you press on a fan hub.

Hard drives can hum. For example, a 3600 RPM hard drive, rotates 60 times
per second, so could make a dandy 60Hz humming sound. A 7200RPM drive
turns 120 times per second, which could also give you a low hum. And if there
is a 60Hz hum from an AC powered device somewhere else in the room, you
can get a beat note, between a disk drive hum and the electrical hum.

My personal preference, is for a heavy computer case, like one with a steel
frame. If there is good weight, and rubber feet on the bottom of the computer,
that may help damp some of the resonances. The frame construction technique
used also makes a difference. Some computer cases are stiffer than others.

Your power supply can make a noise as well. There is a thing called "coil noise",
and if the electrical load on the power supply makes abrupt changes, that
causes the coil to expand and contract. The coil works almost like a small
speaker. Some power supplies have material applied to the coils, to try to
damp that effect, but it isn't always successful.

So even stuff that doesn't rotate inside the computer, can still make a
sound.

Paul