Michael said:
Fortunately it's a Dell laptop which comes with a thorough set of
diagnostics, if you press F12 at startup.
I just spent over an hour testing all the hardware.
Both dual-speed fans (CPU and video) tested OK.
By OK I mean they both passed the on/off test and they both show the RPM for
both speeds. Unless there's a fan failure the diagnostic missed, I am moving
the fans down my list of possible causes.
Judging from the other posts in this thread it sounds like it's more likely
to be hardware than software.
As I said previously, the dull sound (similar to the Critical Stop sound)
occurs just before the desktop icons begin to appear.
It's definitely not the sound of a hard drive bearing. It's clearly coming
from the speakers. It may be what Paul referred to as the BIOS beep. Since I
wasn't sure, that's why up thread I tried to describe is as a bit like the
WinXP Critical Stop sound.
I think the wide range of our suggestions, is intended to suggest there
are many sources for sounds in a PC. And you have to be careful not
to get fooled by the source of the sound.
The PC can have a "beeper" used by the BIOS post. In terms of drivers,
a device like that can have a dedicated "square wave" source, so the
BIOS can even make a "European Police car" sound, by reprogramming the
square wave generator once a second and setting a different frequency.
The "beeper" is less likely to make "nuanced" sounds, because the
thing driving it is not designed for normal audio.
The computer audio speakers would be separate devices, perhaps a pair
of stereo speakers, driven by HDaudio subsystem. The "Critical Stop" or
other system sounds would come from that. The BIOS doesn't tend to drive
the stereo speakers, so is less likely to be sending sounds through
those speakers. The BIOS likes the "beeper", if an alert is needed
at the BIOS level. (The beeper is likely at a known location in the address
map, and the code routine to run it is tiny.) Normal error beeps in the BIOS, would
be at a fixed frequency. And the pattern of beeps indicates an error. The
beep pattern is repeated at regular intervals (so if the machine was
unattended and you come back, you can tell its a BIOS beep pattern).
The hard drive makes a few different sounds, because the motor controller
has more than one option. The motor is multi-phase. If the processor
on the disk drive controller thinks the motor is "stuck", it is possible
to modulate the motor windings in a way intended to "shake the spindle loose".
The idea is, the motor isn't powerful enough to overcome even a slight
source of friction. And tearing the heads off the arm isn't considered
a good solution either. So modulating the motor, can cause the motor
to make a sound which you might mistake for the system speakers or beeper.
And that's why you have to be careful, when doing acoustic debugging,
not to jump to the wrong conclusion.
On a desktop, even the power supply can make noises, such as
"coil noise", but that kind of thing is merely irritating.
Some computer mechanical noises, are only present for the first
30 seconds, or until something warms up, or in the case of a fan,
it starts spinning on axis again. I've had fans here that would
"grumble" at startup, because the bearing is worn, and they don't
spin straight. Eventually, they speed up once they spin along
the correct axis, and there's no more "grumble" until the next
cold start.
Paul
