....snip...
Room temperature is between 17 C (winter) and 28 C (max. in summer). The
temperature of the case is about 34 C.
According to a monitor utility, CPU temp. is always 38-44 C. The room
temperature is always a lot lower, so I should always able to cool it with
air, shouldn't I?
You might find that adding a case fan or two will help things. The case
temperature is not particularly high, but given the room temperature, it
could probably be reduced 2-5 degrees. CPU temperature is fine, so your
cooler is working well, but if the noise is bothering you, I would recommend
adding a case fan to exhaust air from the case. If you already have a case
fan and have space, then add another exhaust fan and consider a fan to suck
air in at the front of the case. You can get pretty quiet case fans. At the
same time, you could consider replacing the heatsink and fan with a quiet
operating device, such as a Zalman
BTW, the fan's spinning seem to depend on the CPU (usage). As soon as CPU
usage increases from 2 to 20% (or more), the fans almost immediately start
to spin faster . This method keeps my CPU cool, but programs requiring
lots
of CPU power will cause the system to produce a hell lot of noise.
This is quite normal. The fan will be activated, or turned up according to
temperature, which rises with workload, but if the surrounding air is
cooler, the heatsink will work more efficiently and cool the CPU more
quickly and the fan might not need to kick into high gear so fast, or for as
long.
Try running the PC with the side off for a day and see if the CPU fan jumps
into high as often. If it does, then you could change it. If it stays quiet,
then you could fix the noise with more case cooling. By the way, everything
will sound louder with the case open (obviously).