"Tony" wrote in message
. uk

You will have to find out if the main problem is the
noise of the air turbulence from the fan or whether the
fan is making the case vibrate.

Easy enough to do, as the related noises sound vastly different.

Dedsheet and similar
damping sheets (there are a lot out there) will only work
on the case vibration and my guess is it is probably the
other.

IME the most profitable route is to look at the fan itself.

Vibration is usally caused by a fan that is out-of-balance or spinning too
fast or both.

Air turbulence noise is caused by a fan that has badly-designed blades, or
is spinning too fast or both.

It's easy enough to find fans that turn slow and have well-designed and
well-balanced rotating parts.


Test by pressing soft things on the outside of
the case to reduce the vibration - if that reduces the
noise then damping sheet will help.

After you get a good fan, any remaining vibration is usually best first
addressed by compliant mounting of the fan.

You can reduce noise
from the air movement by making the air pass through a
tunnel lined with sound absorbing material,

Good work if you have space for it.

of course
wide enough not to reduce the air flow. If you have to
bend the tunnel to fit it in, so much the better.

There's a lot to be said for simply parking the computer as far away as
possible and investing in longer cables for the display, keyboard and mouse.
USB-connected drives can address the problem of mounting removable media if
you do that a lot.