I have an external hard drive box.
The enclosure has a fan.
The fan has got very noisy.
What make and model? Even if that doesn't help us help you,
it might help others avoid that product.
Did the fan start out it's life this noisey or get worse
over time? Is it a ball-bearing or sleeve bearing fan? If
unknown, the sticker may reveal this, or at least the fan
model # which may provide leads with a search engine, or you
could peel back the sticker to see if it has a ball bearing
or sleeve (bronze looking) visible. If a sleeve-bearing,
try lubing it with a thick oil, almost grease.
I was just wondering... do I need the fan at all?
It's likely, semi-modern drives do run fairly hot without
active airflow. It will likely run fine for awhile without
the fan, but shorter lifespan. IF you always run the drive
only long enough to make a backup or move data, it might
never have a chance to heat up much, but if it's running for
a 1/2 hour or more at a time (roughly speaking, depends on
several variables) then it has already heated up.
Am I right in saying that the external hard drives you can buy off the
shelf DON'T have a fan?
Not necessarily, but keep in mind that all they really need
to do is have it last longer than a warranty that might only
be 1 year.
Therefore I don't need a fan??
Not really a safe assumption to make, particularly when
passsive (fanless) cooling designs also allow for better
passive air movement while one incorporating a fan generally
does the opposite, contains the air across the drive so it
has maximum effect from the entry to exhaust points.
With that in mind, if you really, really want to run it
fanless you migth consider taking the casing apart and
drilling a lot of ventilation holes in it. Another
alternative would be to get a new fan, relube the present
fan, and "maybe" run it at lower RPM which will almost
certainly keep drive cooler than a fanless attempt and with
the fan spinning slower it would tend to product far less
noise, last longer, and assumulate less dust in the
enclosure.
You might also take the (screws?) out of the enclosure but
keep it assembled, run the drive for a 1/2 hour then power
it off and immediately open it and touch-test the drive to
see how hot it was getting. If it feels more than warm, it
would be best to find better cooling.