I'm getting a sort of 'beat' effect from my PC. It seems to have been
triggered (or maybe just increased to a level at which I've become
aware of it) by adding a new (third) HD.

I'm at my desk, and the PC is on the carpet 3 feet away, at the side
of the desk. I can just hear this beat from here, behind the familiar
high frequency fan and HD spinning sound. Kneeling on the floor with
my ear by the PC case, I can hear the beat distinctly, at about 1
cycle per second. But my real gripe is that directly below, downstairs
in the lounge, it's surprisingly distinct. By no means deafening, but
it is intrusive. I'm aware of it even while watching TV. This is
through carpet, underlay and 2 layers of plasterboard.

I did also have mechanical noise from the fan (which itself may have
been due to multiple causes, such as bearings, dust and one loose
screw). But I've fixed that, and am left with this pesky beat. It
doesn't appear to be anything I can stop by touching any PC panels, or
even holding the fan itself. So I assume it's some sort of beat in the
air itself, caused by the rpm speeds of various components being very
close together? Rather like 'heterodyning' in radio terms?

I'm not sure what the best approach is. Presumably I can take the beat
frequency out of this apparently sensitive LF region by lowering the
CPU fan speed rpm a bit? I could wire a couple of series diodes in the
supply. Maybe as an initial step I should buy a new 60mm CPU fan,
which is surely unlikely to be similar in rpm speed to the present
one.

Any advice would be appreciated please. Anyone else had similar
behaviour?

--
Terry Pinnell
Hobbyist, West Sussex, UK

On Mon, 03 Oct 2005 08:50:32 +0100, Terry Pinnell
wrote:

I'm getting a sort of 'beat' effect from my PC. It seems to have been
triggered (or maybe just increased to a level at which I've become
aware of it) by adding a new (third) HD.

I'm at my desk, and the PC is on the carpet 3 feet away, at the side
of the desk. I can just hear this beat from here, behind the familiar
high frequency fan and HD spinning sound. Kneeling on the floor with
my ear by the PC case, I can hear the beat distinctly, at about 1
cycle per second. But my real gripe is that directly below, downstairs
in the lounge, it's surprisingly distinct. By no means deafening, but
it is intrusive. I'm aware of it even while watching TV. This is
through carpet, underlay and 2 layers of plasterboard.

I did also have mechanical noise from the fan (which itself may have
been due to multiple causes, such as bearings, dust and one loose
screw). But I've fixed that, and am left with this pesky beat. It
doesn't appear to be anything I can stop by touching any PC panels, or
even holding the fan itself. So I assume it's some sort of beat in the
air itself, caused by the rpm speeds of various components being very
close together? Rather like 'heterodyning' in radio terms?

I'm not sure what the best approach is. Presumably I can take the beat
frequency out of this apparently sensitive LF region by lowering the
CPU fan speed rpm a bit? I could wire a couple of series diodes in the
supply. Maybe as an initial step I should buy a new 60mm CPU fan,
which is surely unlikely to be similar in rpm speed to the present
one.

Any advice would be appreciated please. Anyone else had similar
behaviour?

It is usually the sides of the case behaving like a drum.
Try damping both sides with your hands, and see what happens.

Michael Gray wrote:

It is usually the sides of the case behaving like a drum.
Try damping both sides with your hands, and see what happens.

That makes sense, but holding both sides doesn't diminish the beat. I
can now *feel* it as well as hear it (~ 1 Hz). Any other ideas on
stopping it? How about that rpm reduction I mentioned?

--
Terry Pinnell
Hobbyist, West Sussex, UK

"Terry Pinnell" wrote in message
...
I'm getting a sort of 'beat' effect from my PC. It seems to have been
triggered (or maybe just increased to a level at which I've become
aware of it) by adding a new (third) HD.

I'm at my desk, and the PC is on the carpet 3 feet away, at the side
of the desk. I can just hear this beat from here, behind the familiar
high frequency fan and HD spinning sound. Kneeling on the floor with
my ear by the PC case, I can hear the beat distinctly, at about 1
cycle per second. But my real gripe is that directly below, downstairs
in the lounge, it's surprisingly distinct. By no means deafening, but
it is intrusive. I'm aware of it even while watching TV. This is
through carpet, underlay and 2 layers of plasterboard.

I did also have mechanical noise from the fan (which itself may have
been due to multiple causes, such as bearings, dust and one loose
screw). But I've fixed that, and am left with this pesky beat. It
doesn't appear to be anything I can stop by touching any PC panels, or
even holding the fan itself. So I assume it's some sort of beat in the
air itself, caused by the rpm speeds of various components being very
close together? Rather like 'heterodyning' in radio terms?

I'm not sure what the best approach is. Presumably I can take the beat
frequency out of this apparently sensitive LF region by lowering the
CPU fan speed rpm a bit? I could wire a couple of series diodes in the
supply. Maybe as an initial step I should buy a new 60mm CPU fan,
which is surely unlikely to be similar in rpm speed to the present
one.

Any advice would be appreciated please. Anyone else had similar
behaviour?


You'll need to isolate the cause of the sound. Try stopping the CPU fan
briefly either by putting your finger on the centre hub of the fan or
unplugging it. Don't worry about overheating, an idle CPU will be OK for
several minutes without a fan before it gets uncomfortably warm. If the
noise is still there, go through all the other spinning devices one by one.
Disconnect hard drives and case fans and see if you can isolate the
offending item. Still no luck? Disconnect the cpu fan, case fans and all the
hard drives and power up. The only rotating item should be the power supply
fan. If the noise is still there, that's the problem.

I've seen quite a few noisy PSU fans, and the way they are mounted means
they can transfer a lot of noise and vibration to the case so it acts like a
resonating chamber. To confirm a noisy PSU fan, you can temporarily disable
it safely by powering off, inserting a plastic rod carefully into the blades
and powering back on. I've even stopped moving blades with a plastic
implement without any damage, but it's unnecessary for your purposes. Never
insert anything metallic or conductive. Don't run the PC for longer than
absolutely necessary with a disabled PSU fan, they get very hot rather
quickly!

Dave

"Dave D" wrote:


You'll need to isolate the cause of the sound. Try stopping the CPU fan
briefly either by putting your finger on the centre hub of the fan or
unplugging it. Don't worry about overheating, an idle CPU will be OK for
several minutes without a fan before it gets uncomfortably warm. If the
noise is still there, go through all the other spinning devices one by one.
Disconnect hard drives and case fans and see if you can isolate the
offending item. Still no luck? Disconnect the cpu fan, case fans and all the
hard drives and power up. The only rotating item should be the power supply
fan. If the noise is still there, that's the problem.

I've seen quite a few noisy PSU fans, and the way they are mounted means
they can transfer a lot of noise and vibration to the case so it acts like a
resonating chamber. To confirm a noisy PSU fan, you can temporarily disable
it safely by powering off, inserting a plastic rod carefully into the blades
and powering back on. I've even stopped moving blades with a plastic
implement without any damage, but it's unnecessary for your purposes. Never
insert anything metallic or conductive. Don't run the PC for longer than
absolutely necessary with a disabled PSU fan, they get very hot rather
quickly!

Thanks, I'll schedule that for when I don't need the PC for a while!

But if this is a *beat*, presumably there are two components, not one?

It may be coincidence, but I've only become aware of this since
installing a third HD - a 200GB Maxtor Diamond, 7200 rpm, in addition
to my two 60GB Maxtors.

BTW, when it comes to disconnecting a HD to test its impact on the
noise, can I just close WinXP, remove the power plug from it and
reboot? On later reconnecting it, will WinXP have to go through any
hardware wizardry? My experience of that is mixed, so I like to avoid
it whenever possible!

--
Terry Pinnell
Hobbyist, West Sussex, UK

"Terry Pinnell" wrote in message
...
Michael Gray wrote:

It is usually the sides of the case behaving like a drum.
Try damping both sides with your hands, and see what happens.

That makes sense, but holding both sides doesn't diminish the beat. I
can now *feel* it as well as hear it (~ 1 Hz). Any other ideas on
stopping it? How about that rpm reduction I mentioned?

--
Terry Pinnell
Hobbyist, West Sussex, UK



You are an exceptional person to be able to hear 1 Hz!

John

"Terry Pinnell" wrote in message
...

snip

Thanks, I'll schedule that for when I don't need the PC for a while!

But if this is a *beat*, presumably there are two components, not one?


Not necessarily, it could be the natural resonance of the component/PC
casing.

It may be coincidence, but I've only become aware of this since
installing a third HD - a 200GB Maxtor Diamond, 7200 rpm, in addition
to my two 60GB Maxtors.


Could be the new hard drive isn't fantastically well balanced. For example,
I've had UW SCSI drives create quite a racket as they can vibrate a bit more
than slower devices.

BTW, when it comes to disconnecting a HD to test its impact on the
noise, can I just close WinXP, remove the power plug from it and
reboot?

Yes, but you don't have to let Windows boot to test for noise, just hit
pause at the POST screen, or hit F8 to stop Windows starting.

On later reconnecting it, will WinXP have to go through any
hardware wizardry?

No.

My experience of that is mixed, so I like to avoid
it whenever possible!

--

Best to not let Windows boot then. I've seen windows change drive letters
under these circumstances, which may or may not be a problem for you.

Dave

"Dave D" wrote:


"Terry Pinnell" wrote in message
.. .

snip

Thanks, I'll schedule that for when I don't need the PC for a while!

But if this is a *beat*, presumably there are two components, not one?


Not necessarily, it could be the natural resonance of the component/PC
casing.

It may be coincidence, but I've only become aware of this since
installing a third HD - a 200GB Maxtor Diamond, 7200 rpm, in addition
to my two 60GB Maxtors.


Could be the new hard drive isn't fantastically well balanced. For example,
I've had UW SCSI drives create quite a racket as they can vibrate a bit more
than slower devices.

BTW, when it comes to disconnecting a HD to test its impact on the
noise, can I just close WinXP, remove the power plug from it and
reboot?

Yes, but you don't have to let Windows boot to test for noise, just hit
pause at the POST screen, or hit F8 to stop Windows starting.

On later reconnecting it, will WinXP have to go through any
hardware wizardry?

No.

My experience of that is mixed, so I like to avoid
it whenever possible!

--

Best to not let Windows boot then. I've seen windows change drive letters
under these circumstances, which may or may not be a problem for you.

Dave

Thanks a lot for the follow-up.

--
Terry, West Sussex, UK

In article , says...

"Terry Pinnell" wrote in message
...

snip

Thanks, I'll schedule that for when I don't need the PC for a while!

But if this is a *beat*, presumably there are two components, not one?


Not necessarily, it could be the natural resonance of the component/PC
casing.

It may be coincidence, but I've only become aware of this since
installing a third HD - a 200GB Maxtor Diamond, 7200 rpm, in addition
to my two 60GB Maxtors.


Could be the new hard drive isn't fantastically well balanced. For example,
I've had UW SCSI drives create quite a racket as they can vibrate a bit more
than slower devices.

At 1Hz? I doubt it, unless it is beating against something else (like another
drive . I'd suspect the fans before the drive(s). Disconnect one at a time
and listen for any change.

BTW, when it comes to disconnecting a HD to test its impact on the
noise, can I just close WinXP, remove the power plug from it and
reboot?

snip

Best to not let Windows boot then. I've seen windows change drive letters
under these circumstances, which may or may not be a problem for you.

I've had Windows change drive letters for no apparent reason too. It's easy to
change 'em back though.

--
Keith

"Terry Pinnell" wrote in message
...
I'm getting a sort of 'beat' effect from my PC. It seems to have been
triggered (or maybe just increased to a level at which I've become
aware of it) by adding a new (third) HD.

I'm at my desk, and the PC is on the carpet 3 feet away, at the side
of the desk. I can just hear this beat from here, behind the familiar
high frequency fan and HD spinning sound. Kneeling on the floor with
my ear by the PC case, I can hear the beat distinctly, at about 1
cycle per second. But my real gripe is that directly below, downstairs
in the lounge, it's surprisingly distinct. By no means deafening, but
it is intrusive. I'm aware of it even while watching TV. This is
through carpet, underlay and 2 layers of plasterboard.

I did also have mechanical noise from the fan (which itself may have
been due to multiple causes, such as bearings, dust and one loose
screw). But I've fixed that, and am left with this pesky beat. It
doesn't appear to be anything I can stop by touching any PC panels, or
even holding the fan itself. So I assume it's some sort of beat in the
air itself, caused by the rpm speeds of various components being very
close together? Rather like 'heterodyning' in radio terms?

I'm not sure what the best approach is. Presumably I can take the beat
frequency out of this apparently sensitive LF region by lowering the
CPU fan speed rpm a bit? I could wire a couple of series diodes in the
supply. Maybe as an initial step I should buy a new 60mm CPU fan,
which is surely unlikely to be similar in rpm speed to the present
one.

Any advice would be appreciated please. Anyone else had similar
behaviour?

How many HDD's have you? I had a similar problem when I added a second 7200
HDD to my system. It was a complete ba£T@rd to solve the problem, eventually
cured by moving the second drive into an external USB2 enclosure.

"Terry Pinnell" bravely wrote to "All" (03 Oct 05 08:50:32)
--- on the heady topic of "PC CPU fan"

Terry,

I had a similar annoying problem with a freezer fan. It would knock
like your computer at about 1 beat per second. What was happening was
that the fridge was slightly tilted backwards and fan rotor was
travelling up the bearing and then sliding back in one shot sharply
against the backstop. Who would have thought!?

Your solution may be as simple as leveling your computer's case the
other way. As for the freezer fan I added a small spring on the shaft.

A*s*i*m*o*v


TP From: Terry Pinnell
TP sci.electronics.design:511555

TP I'm getting a sort of 'beat' effect from my PC. It seems to have been
TP triggered (or maybe just increased to a level at which I've become
TP aware of it) by adding a new (third) HD.

TP I'm at my desk, and the PC is on the carpet 3 feet away, at the side
TP of the desk. I can just hear this beat from here, behind the familiar
TP high frequency fan and HD spinning sound. Kneeling on the floor with
TP my ear by the PC case, I can hear the beat distinctly, at about 1
TP cycle per second. But my real gripe is that directly below, downstairs
TP in the lounge, it's surprisingly distinct. By no means deafening, but
TP it is intrusive. I'm aware of it even while watching TV. This is
TP through carpet, underlay and 2 layers of plasterboard.

TP I did also have mechanical noise from the fan (which itself may have
TP been due to multiple causes, such as bearings, dust and one loose
TP screw). But I've fixed that, and am left with this pesky beat. It
TP doesn't appear to be anything I can stop by touching any PC panels, or
TP even holding the fan itself. So I assume it's some sort of beat in the
TP air itself, caused by the rpm speeds of various components being very
TP close together? Rather like 'heterodyning' in radio terms?

TP I'm not sure what the best approach is. Presumably I can take the beat
TP frequency out of this apparently sensitive LF region by lowering the
TP CPU fan speed rpm a bit? I could wire a couple of series diodes in the
TP supply. Maybe as an initial step I should buy a new 60mm CPU fan,
TP which is surely unlikely to be similar in rpm speed to the present
TP one.

TP Any advice would be appreciated please. Anyone else had similar
TP behaviour?

TP --
TP Terry Pinnell
TP Hobbyist, West Sussex, UK

.... Modulation in all things...

John - kd5yi wrote:
"Terry Pinnell" wrote in message
...
Michael Gray wrote:

It is usually the sides of the case behaving like a drum.
Try damping both sides with your hands, and see what happens.

That makes sense, but holding both sides doesn't diminish the beat. I
can now *feel* it as well as hear it (~ 1 Hz). Any other ideas on
stopping it? How about that rpm reduction I mentioned?

--
Terry Pinnell
Hobbyist, West Sussex, UK



You are an exceptional person to be able to hear 1 Hz!

John

Not at all, you can do it too. The beat he's hearing is the same as
tuning a musical instrument. My question is: how accurate is the '7200'
RPM? Would different models be phase locked or are they just 'close'?
AND, is it a balance issue with the drives (or fans)?
GG

"Anna Daptor" wrote:


How many HDD's have you? I had a similar problem when I added a second 7200
HDD to my system. It was a complete ba£T@rd to solve the problem, eventually
cured by moving the second drive into an external USB2 enclosure.

This new one is the third. I had to buy a 5.25" tray for it, to
install it below my DVD & CD drives. All 3 are 7200 rpm.

--
Terry Pinnell
Hobbyist, West Sussex, UK

"Glenn Gundlach" wrote:


John - kd5yi wrote:

You are an exceptional person to be able to hear 1 Hz!

John

Not at all, you can do it too. The beat he's hearing is the same as
tuning a musical instrument. My question is: how accurate is the '7200'
RPM? Would different models be phase locked or are they just 'close'?
AND, is it a balance issue with the drives (or fans)?
GG

Thanks Glenn. All 3 of my HDs are Maxtors (2 x 60GB, and this latest
200GB), and all are 7200 rpm. Are you speculating that one might be
spinning at 432.000 kHz, and the other at 432.001 kHz?!

--
Terry Pinnell
Hobbyist, West Sussex, UK

I read in sci.electronics.design that Terry Pinnell
wrote (in
) about 'PC CPU fan', on
Mon, 3 Oct 2005:

I'm not sure what the best approach is. Presumably I can take the beat
frequency out of this apparently sensitive LF region by lowering the
CPU fan speed rpm a bit? I could wire a couple of series diodes in the
supply. Maybe as an initial step I should buy a new 60mm CPU fan, which
is surely unlikely to be similar in rpm speed to the present one.

Any advice would be appreciated please. Anyone else had similar
behaviour?

Yes, with my old DIY computer with two hard drives.

What is your computer standing on? If it's rigidly connected to the
building structure, the beating frequencies will get into the structure
and appear, amplified, in all sorts of strange places, as you found.

Try standing the computer on a THICK (think 75 mm) of none-too-soft PU
foam, that doesn't collapse under the weight.
--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I read in sci.electronics.design that Terry Pinnell
wrote (in
) about 'PC CPU fan', on
Mon, 3 Oct 2005:

Thanks Glenn. All 3 of my HDs are Maxtors (2 x 60GB, and this latest
200GB), and all are 7200 rpm. Are you speculating that one might be
spinning at 432.000 kHz, and the other at 432.001 kHz?!

I think you multiplied by 60. 7200 RPM is 120 Hz.
--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I read in sci.electronics.design that Terry Pinnell
wrote (in
) about 'PC CPU fan', on
Mon, 3 Oct 2005:

It may be coincidence, but I've only become aware of this since
installing a third HD - a 200GB Maxtor Diamond, 7200 rpm, in addition
to my two 60GB Maxtors.

Try loosening its fixing screws. If that stops the beat, tighten
slightly at random until the beat comes back. Reverse last step. Relax.
--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

John Woodgate wrote:

I read in sci.electronics.design that Terry Pinnell
wrote (in
) about 'PC CPU fan', on
Mon, 3 Oct 2005:

Thanks Glenn. All 3 of my HDs are Maxtors (2 x 60GB, and this latest
200GB), and all are 7200 rpm. Are you speculating that one might be
spinning at 432.000 kHz, and the other at 432.001 kHz?!

I think you multiplied by 60. 7200 RPM is 120 Hz.

Oops! That makes a lot more sense, thanks g.

So is it plausible that a HD1 could be spinning at 120 Hz and HD2 at
121 Hz (7260 rpm) to cause such a 'beat'?

--
Terry Pinnell
Hobbyist, West Sussex, UK

John Woodgate wrote:

I read in sci.electronics.design that Terry Pinnell
wrote (in
) about 'PC CPU fan', on
Mon, 3 Oct 2005:

It may be coincidence, but I've only become aware of this since
installing a third HD - a 200GB Maxtor Diamond, 7200 rpm, in addition
to my two 60GB Maxtors.

Try loosening its fixing screws. If that stops the beat, tighten
slightly at random until the beat comes back. Reverse last step. Relax.

OK, will try that, thanks. As the tray has to be removed to get at the
screws, that potentially implies means a lot of rebooting though.

It's too soon to be sure, but I think I've made an improvement by not
using the 'locking knob' after attaching the side panel of this MESH
UK Athlon 1800 PC. The LF hum is still there, but it sounds almost
steady now, rather than beating.

I may also try some self-adhesive insulation of some sort on that side
panel.

--
Terry Pinnell
Hobbyist, West Sussex, UK

John Woodgate wrote:

I read in sci.electronics.design that Terry Pinnell
wrote (in
) about 'PC CPU fan', on
Mon, 3 Oct 2005:

I'm not sure what the best approach is. Presumably I can take the beat
frequency out of this apparently sensitive LF region by lowering the
CPU fan speed rpm a bit? I could wire a couple of series diodes in the
supply. Maybe as an initial step I should buy a new 60mm CPU fan, which
is surely unlikely to be similar in rpm speed to the present one.

Any advice would be appreciated please. Anyone else had similar
behaviour?

Yes, with my old DIY computer with two hard drives.

What is your computer standing on? If it's rigidly connected to the
building structure, the beating frequencies will get into the structure
and appear, amplified, in all sorts of strange places, as you found.

Try standing the computer on a THICK (think 75 mm) of none-too-soft PU
foam, that doesn't collapse under the weight.

It's just resting on the carpet and underlay at the side of my desk.
Then wood flooring and plasterboard lounge ceiling below.

--
Terry Pinnell
Hobbyist, West Sussex, UK

I read in sci.electronics.design that Terry Pinnell
wrote (in
) about 'PC CPU fan', on
Mon, 3 Oct 2005:

So is it plausible that a HD1 could be spinning at 120 Hz and HD2 at
121 Hz (7260 rpm) to cause such a 'beat'?

Maybe, but you don't need to know. I've given you two ways to tackle it.
Try them.
--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I read in sci.electronics.design that Terry Pinnell
wrote (in
) about 'PC CPU fan', on
Mon, 3 Oct 2005:

It's just resting on the carpet and underlay at the side of my desk.
Then wood flooring and plasterboard lounge ceiling below.

That's not effective sound insulation. Your wood floor will love to
vibrate at 1 Hz, even if it's not tuned to that frequency. You need a
THICK pad -- no, thicker than that!
--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

On Mon, 03 Oct 2005 08:50:32 +0100, Terry Pinnell wrote:

I'm getting a sort of 'beat' effect from my PC. It seems to have been
triggered (or maybe just increased to a level at which I've become
aware of it) by adding a new (third) HD.

I'm at my desk, and the PC is on the carpet 3 feet away, at the side
of the desk. I can just hear this beat from here, behind the familiar
high frequency fan and HD spinning sound. Kneeling on the floor with
my ear by the PC case, I can hear the beat distinctly, at about 1
cycle per second. But my real gripe is that directly below, downstairs
in the lounge, it's surprisingly distinct. By no means deafening, but
it is intrusive. I'm aware of it even while watching TV. This is
through carpet, underlay and 2 layers of plasterboard.

It's the resonant frequency of the floor itself. I'm ass-u-me-ing that
you're talking about the beat frequency, which sounds like, wOwwwOwwwOwww...,
is that accurate? If it's just going thumpa-thumpa-thumpa, then you need
to fire your yard boy. ;-P

Go either to a scrap yard or a construction site, and get something
very massive, like a paving tile or slab of metal, put it on the floor
where the computer is now. Put some kind of acoustic insulation on top
of it, like get a discarded wet suit or some old inner tubes, and put
the computer on top of that pile. Don't use "acoustical tile", because
you want the opposite of rigidity here.

Good Luck!
Rich

(of course, you could overwhelm it by playing that tape of the barking
dog that seems to come up here periodically. ;-) )

On Mon, 03 Oct 2005 20:09:28 +0100, John Woodgate wrote:

I read in sci.electronics.design that Terry Pinnell
wrote (in
) about 'PC CPU fan', on
Mon, 3 Oct 2005:

It's just resting on the carpet and underlay at the side of my desk.
Then wood flooring and plasterboard lounge ceiling below.

That's not effective sound insulation. Your wood floor will love to
vibrate at 1 Hz, even if it's not tuned to that frequency. You need a
THICK pad -- no, thicker than that!

Apropos nothing, I once was renting a guy's basement. It was always
uncomfortably cold, but there was a gas space heater, but all of the
warm air, of course, floated up to the ceiling (which was the underside
of the floor of the upstairs), so my feet would freeze, while my head
would sweat. In lieu of walking around the apartment on my hands, I
took one of those little fans - you know, the shaded-pole motor, with
about a 3" (8 cm?) aluminum fan blade - and hung it from a joist to
blow warm air downwards toward my bed and stuff. It went "THRUMMMMM!!!!"
and my roommate/landlord didn't like the noise. Well, it turns out
that he also had an old turntable (remember record players?) that he
was going to toss, so he let me salvage it, and I took a couple of
the suspension springs from the turntable, and hung my little fan
from them. The silence was golden. :-) :-)

Floors make surprisingly good sounding boards. :-)

Good Luck!
Rich

On Mon, 03 Oct 2005 08:50:32 +0100, Terry Pinnell wrote:

I'm getting a sort of 'beat' effect from my PC. It seems to have been
triggered (or maybe just increased to a level at which I've become
aware of it) by adding a new (third) HD.

I'm at my desk, and the PC is on the carpet 3 feet away, at the side
of the desk. I can just hear this beat from here, behind the familiar
high frequency fan and HD spinning sound. Kneeling on the floor with
my ear by the PC case, I can hear the beat distinctly, at about 1
cycle per second. But my real gripe is that directly below, downstairs
in the lounge, it's surprisingly distinct. By no means deafening, but
it is intrusive. I'm aware of it even while watching TV. This is
through carpet, underlay and 2 layers of plasterboard.

Get an office that adjoins a machine shop/fab shop. I guarantee, you
won't notice the noise from the computer! ;-P

Cheers!
Rich

On Mon, 03 Oct 2005 20:20:01 +0000, The Cheese Machine wrote:

FWIW - Maplin's sound dampening kit (A48AK) works quite well, though not
exactly cheap at 18ukp, especially against HD chassis-borne noise.

Yup! Can't let them sounds dry out!
--
Flap!
The Pig Bladder from Uranus, still waiting for that
hot babe to ask what my favorite planet is. ;-j

On Mon, 03 Oct 2005 09:20:08 -0700, Glenn Gundlach wrote:


John - kd5yi wrote:
"Terry Pinnell" wrote in message
...
Michael Gray wrote:

It is usually the sides of the case behaving like a drum.
Try damping both sides with your hands, and see what happens.

That makes sense, but holding both sides doesn't diminish the beat. I
can now *feel* it as well as hear it (~ 1 Hz). Any other ideas on
stopping it? How about that rpm reduction I mentioned?

--
Terry Pinnell
Hobbyist, West Sussex, UK



You are an exceptional person to be able to hear 1 Hz!

John

Not at all, you can do it too. The beat he's hearing is the same as
tuning a musical instrument. My question is: how accurate is the '7200'
RPM? Would different models be phase locked or are they just 'close'?
AND, is it a balance issue with the drives (or fans)?

Well, drives shouldn't whine so much that they beat against each other's
whine (there's gotta be a joke in that sentence somewhere - anyone?) -
take the noisy drive back to the store, and get one that isn't eating
its own bearings.

Good Luck!
Rich

"Terry Pinnell" wrote in message
...
I'm getting a sort of 'beat' effect from my PC. It seems to have been
triggered (or maybe just increased to a level at which I've become
aware of it) by adding a new (third) HD.

I'm at my desk, and the PC is on the carpet 3 feet away, at the side
of the desk. I can just hear this beat from here, behind the familiar
high frequency fan and HD spinning sound. Kneeling on the floor with
my ear by the PC case, I can hear the beat distinctly, at about 1
cycle per second. But my real gripe is that directly below, downstairs
in the lounge, it's surprisingly distinct. By no means deafening, but
it is intrusive. I'm aware of it even while watching TV. This is
through carpet, underlay and 2 layers of plasterboard.

I did also have mechanical noise from the fan (which itself may have
been due to multiple causes, such as bearings, dust and one loose
screw). But I've fixed that, and am left with this pesky beat. It
doesn't appear to be anything I can stop by touching any PC panels, or
even holding the fan itself. So I assume it's some sort of beat in the
air itself, caused by the rpm speeds of various components being very
close together? Rather like 'heterodyning' in radio terms?

I'm not sure what the best approach is. Presumably I can take the beat
frequency out of this apparently sensitive LF region by lowering the
CPU fan speed rpm a bit? I could wire a couple of series diodes in the
supply. Maybe as an initial step I should buy a new 60mm CPU fan,
which is surely unlikely to be similar in rpm speed to the present
one.

Any advice would be appreciated please. Anyone else had similar
behaviour?

--
Terry Pinnell
Hobbyist, West Sussex, UK

I've had things like this happen when the hard drive bracket wasn't screwed
down tightly, or the case just poorly designed so it's not as rigid as it
should be. Sometimes if the floor is a little uneven and you set it a
certain way, some metal part of the case will resonate, sometimes moving it,
tightening screws, or sticking a piece of tape between whatever's vibrating
and whatever it's attached to will help.

On Mon, 03 Oct 2005 14:05:55 +0100, Terry Pinnell
put finger to keyboard and
composed:

It may be coincidence, but I've only become aware of this since
installing a third HD - a 200GB Maxtor Diamond, 7200 rpm, in addition
to my two 60GB Maxtors.

I would think it unlikely that your two identical drives would spin at
a speed that is different enough to produce a 1Hz beat. That's a
difference of 1:120, or 1:360 if you consider a possible harmonic
effect of the motor's three windings. AFAIK, the speed is crystal
locked. Your observation in respect of the 200GB drive sounds more
plausible since it could involve different crystal frequencies.

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.

On Mon, 3 Oct 2005 08:26:38 -0500, "John - kd5yi"
put finger to keyboard and composed:


"Terry Pinnell" wrote in message
.. .
Michael Gray wrote:

It is usually the sides of the case behaving like a drum.
Try damping both sides with your hands, and see what happens.

That makes sense, but holding both sides doesn't diminish the beat. I
can now *feel* it as well as hear it (~ 1 Hz). Any other ideas on
stopping it? How about that rpm reduction I mentioned?

--
Terry Pinnell
Hobbyist, West Sussex, UK



You are an exceptional person to be able to hear 1 Hz!

John

The 1Hz is the amplitude modulated envelope (cos b) of a higher
audible frequency (sin a). In other words, you are hearing a higher
frequency signal whose volume fluctuates at 1Hz.

sin (a + b) + sin (a - b) = 2 . sin a . cos b

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.

On Tue, 04 Oct 2005 15:20:02 +1000, Franc Zabkar
wrote:

On Mon, 03 Oct 2005 14:05:55 +0100, Terry Pinnell
put finger to keyboard and
composed:

It may be coincidence, but I've only become aware of this since
installing a third HD - a 200GB Maxtor Diamond, 7200 rpm, in addition
to my two 60GB Maxtors.

I would think it unlikely that your two identical drives would spin at
a speed that is different enough to produce a 1Hz beat. That's a
difference of 1:120, or 1:360 if you consider a possible harmonic
effect of the motor's three windings. AFAIK, the speed is crystal
locked. Your observation in respect of the 200GB drive sounds more
plausible since it could involve different crystal frequencies.

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.

Obviously, the near empty new drive is filled with a minimal amount of
data, located on one side of the platter. This causes a considerable
unbalance, causing vibration.
Just put more stuff on that drive.

And now I will go on with my design of a battery charger that cuts off
the charging process based on weight increase of a charged pack.


--
- René

René wrote:

And now I will go on with my design of a battery charger that cuts off
the charging process based on weight increase of a charged pack.

Take a 12V, 100AH battery. That's 12*100*3600J = 4.32MJ. e=mc^2, so the
mass gain from flat to full is e/c^2 = 5e-11N, or about 5e-12Kg. Piece
of ****, but works better with bigger batteries.

Paul Burke

"The Cheese Machine" wrote:

FWIW - Maplin's sound dampening kit (A48AK) works quite well, though not
exactly cheap at 18ukp, especially against HD chassis-borne noise.

Thanks, I'll take a look at it.

But I must say that I'm now into the 2nd day of *relative quiet* ! As
described earlier, this significant change has come about simply by
not using the 'locking lever' on the back corner of the PC case. In
fact, I have to conclude that I must have had it in that unlocked
state before installing my new HD.

I can still hear *some* LF noise, but only downstairs in the lounge,
not sitting here at the PC!

--
Terry, West Sussex, UK

Franc Zabkar wrote:

On Mon, 03 Oct 2005 14:05:55 +0100, Terry Pinnell
put finger to keyboard and
composed:

It may be coincidence, but I've only become aware of this since
installing a third HD - a 200GB Maxtor Diamond, 7200 rpm, in addition
to my two 60GB Maxtors.

I would think it unlikely that your two identical drives would spin at
a speed that is different enough to produce a 1Hz beat. That's a
difference of 1:120, or 1:360 if you consider a possible harmonic
effect of the motor's three windings. AFAIK, the speed is crystal
locked. Your observation in respect of the 200GB drive sounds more
plausible since it could involve different crystal frequencies.


Thanks, makes sense. Just under 1% is probably acceptable tolerance
for an advertised speed of '7200 rpm'. Mind you, given that this new
one is Maxtor too, and broadly same 'Diamond' range, I'd have expected
the same crystal to be used.

--
Terry Pinnell
Hobbyist, West Sussex, UK

"James Sweet" wrote:


"Terry Pinnell" wrote in message
.. .
I'm getting a sort of 'beat' effect from my PC. It seems to have been
triggered (or maybe just increased to a level at which I've become
aware of it) by adding a new (third) HD.

I'm at my desk, and the PC is on the carpet 3 feet away, at the side
of the desk. I can just hear this beat from here, behind the familiar
high frequency fan and HD spinning sound. Kneeling on the floor with
my ear by the PC case, I can hear the beat distinctly, at about 1
cycle per second. But my real gripe is that directly below, downstairs
in the lounge, it's surprisingly distinct. By no means deafening, but
it is intrusive. I'm aware of it even while watching TV. This is
through carpet, underlay and 2 layers of plasterboard.

I did also have mechanical noise from the fan (which itself may have
been due to multiple causes, such as bearings, dust and one loose
screw). But I've fixed that, and am left with this pesky beat. It
doesn't appear to be anything I can stop by touching any PC panels, or
even holding the fan itself. So I assume it's some sort of beat in the
air itself, caused by the rpm speeds of various components being very
close together? Rather like 'heterodyning' in radio terms?

I'm not sure what the best approach is. Presumably I can take the beat
frequency out of this apparently sensitive LF region by lowering the
CPU fan speed rpm a bit? I could wire a couple of series diodes in the
supply. Maybe as an initial step I should buy a new 60mm CPU fan,
which is surely unlikely to be similar in rpm speed to the present
one.

Any advice would be appreciated please. Anyone else had similar
behaviour?

--
Terry Pinnell
Hobbyist, West Sussex, UK

I've had things like this happen when the hard drive bracket wasn't screwed
down tightly, or the case just poorly designed so it's not as rigid as it
should be. Sometimes if the floor is a little uneven and you set it a
certain way, some metal part of the case will resonate, sometimes moving it,
tightening screws, or sticking a piece of tape between whatever's vibrating
and whatever it's attached to will help.

Thanks for all the follow-ups. As per my earlier post, situation is
now much improved.

--
Terry Pinnell
Hobbyist, West Sussex, UK

I read in sci.electronics.design that René wrote
(in ) about 'PC CPU fan', on
Tue, 4 Oct 2005:

And now I will go on with my design of a battery charger that cuts off
the charging process based on weight increase of a charged pack.

Don't forget to correct for the buoyancy of the evolved hydrogen.
--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I read in sci.electronics.design that Paul Burke wrote
(in ) about 'PC CPU fan', on Tue, 4 Oct
2005:
René wrote:

And now I will go on with my design of a battery charger that cuts off
the charging process based on weight increase of a charged pack.

Take a 12V, 100AH battery. That's 12*100*3600J = 4.32MJ. e=mc^2, so the
mass gain from flat to full is e/c^2 = 5e-11N, or about 5e-12Kg. Piece
of ****, but works better with bigger batteries.

5 nanograms? I'm sure Win could measure that in a force 8 gale.
--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

On Tue, 04 Oct 2005 15:20:02 +1000, Franc Zabkar
wrote:

On Mon, 3 Oct 2005 08:26:38 -0500, "John - kd5yi"
put finger to keyboard and composed:


"Terry Pinnell" wrote in message
. ..
Michael Gray wrote:

It is usually the sides of the case behaving like a drum.
Try damping both sides with your hands, and see what happens.

That makes sense, but holding both sides doesn't diminish the beat. I
can now *feel* it as well as hear it (~ 1 Hz). Any other ideas on
stopping it? How about that rpm reduction I mentioned?

--
Terry Pinnell
Hobbyist, West Sussex, UK



You are an exceptional person to be able to hear 1 Hz!

John

The 1Hz is the amplitude modulated envelope (cos b) of a higher
audible frequency (sin a). In other words, you are hearing a higher
frequency signal whose volume fluctuates at 1Hz.

sin (a + b) + sin (a - b) = 2 . sin a . cos b

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.

In audio(+) sometimes referred to as a difference frequency, and there
are also sum frequencies...heterodyning, I think? It's been awhile...

Tom

"John Woodgate" wrote in message
...
I read in sci.electronics.design that René wrote
(in ) about 'PC CPU fan', on
Tue, 4 Oct 2005:

And now I will go on with my design of a battery charger that cuts off the
charging process based on weight increase of a charged pack.

Don't forget to correct for the buoyancy of the evolved hydrogen.

Once it has evolved, does it turn into Helium? Have to be careful about
fusing.

Regards
Ian