Case fans - "beat" frequency

[Guest]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

Hi all,

Just put together my new system with 4 * 80mm case fans (its located
in a very warm room).

I am being irritated by what I have discovered is called the "beat"
frequency caused by the slight differences in fan speeds, resulting in
a "throbbing" sound...

The fans are marketed as quiet ones - its not the overall noise that
bothers me, its just the variation thats irritating.

Do I have any options other that ear plugs/loud music? Looking in the
BIOS I see that the fan speed vary in RPMs a little as I would expect
- what percentage variance is normal? I suspect the fans would all
have to run at "precisely" the same speed to avoid the noise in any
case....

Ultimately I am more concerned about having a cool system than a quiet
one so i can live with it but it seems to me that given the current
nature of PC cooling requirements many people must experience this
"beat" frequency annoyance.


thanks for any thoughts

 

[Guest]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

"Gav" <gavin@my-deja.com> wrote in message
news:7da6364d.0406040145.3661cd46@posting.google.com...
> Hi all,
>
> Just put together my new system with 4 * 80mm case fans (its located
> in a very warm room).
>
> I am being irritated by what I have discovered is called the "beat"
> frequency caused by the slight differences in fan speeds, resulting in
> a "throbbing" sound...
>
> The fans are marketed as quiet ones - its not the overall noise that
> bothers me, its just the variation thats irritating.
>
> Do I have any options other that ear plugs/loud music? Looking in the
> BIOS I see that the fan speed vary in RPMs a little as I would expect
> - what percentage variance is normal? I suspect the fans would all
> have to run at "precisely" the same speed to avoid the noise in any
> case....
>
> Ultimately I am more concerned about having a cool system than a quiet
> one so i can live with it but it seems to me that given the current
> nature of PC cooling requirements many people must experience this
> "beat" frequency annoyance.
>
>
> thanks for any thoughts

A single quiet 120mm fan might provide you just as much cooling without all
the noise if your case will accept one in the correct top rear location.
More is not always better when it comes to fans.
--
John McGaw
[Knoxville, TN, USA]
http://johnmcgaw.com

 

[Apollo]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

"Gav" <gavin@my-deja.com> wrote in message
news:7da6364d.0406040145.3661cd46@posting.google.com...
> Hi all,
>
> Just put together my new system with 4 * 80mm case fans (its located
> in a very warm room).
>
> I am being irritated by what I have discovered is called the "beat"
> frequency caused by the slight differences in fan speeds, resulting in
> a "throbbing" sound...

I had the same problem, but with 1 x 120mm, 2 x 80mm, 1 x 92mm + psu fans.
I don't think that the speeds have to be close even, the beats are iirc
certain harmonics resonating.
>
> The fans are marketed as quiet ones - its not the overall noise that
> bothers me, its just the variation thats irritating.
>
> Do I have any options other that ear plugs/loud music? Looking in the
> BIOS I see that the fan speed vary in RPMs a little as I would expect
> - what percentage variance is normal? I suspect the fans would all
> have to run at "precisely" the same speed to avoid the noise in any
> case....

Without expensive control equipment / fans, you can't run them at exactly
the same speed.

>
> Ultimately I am more concerned about having a cool system than a quiet
> one so i can live with it but it seems to me that given the current
> nature of PC cooling requirements many people must experience this
> "beat" frequency annoyance.
>
I got two Zalman Fanmates and played with the speeds of the 120 and the 92,
I probably only droppped them by 100rpm and it cured the beats. You may
have to play around for a while over a few days to get it cured. Mine come
back slightly now and again, it's probably related to air temp, pressure and
all sorts of complicated variables.

>
> thanks for any thoughts

HTH

--
Ian

 

[Dave]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

Get a fan bus.

"Gav" <gavin@my-deja.com> wrote in message
news:7da6364d.0406040145.3661cd46@posting.google.com...
> Hi all,
>
> Just put together my new system with 4 * 80mm case fans (its located
> in a very warm room).
>
> I am being irritated by what I have discovered is called the "beat"
> frequency caused by the slight differences in fan speeds, resulting in
> a "throbbing" sound...
>
> The fans are marketed as quiet ones - its not the overall noise that
> bothers me, its just the variation thats irritating.
>
> Do I have any options other that ear plugs/loud music? Looking in the
> BIOS I see that the fan speed vary in RPMs a little as I would expect
> - what percentage variance is normal? I suspect the fans would all
> have to run at "precisely" the same speed to avoid the noise in any
> case....
>
> Ultimately I am more concerned about having a cool system than a quiet
> one so i can live with it but it seems to me that given the current
> nature of PC cooling requirements many people must experience this
> "beat" frequency annoyance.
>
>
> thanks for any thoughts

 

[Guest]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

"Apollo" <REMOVEMEian_dunbar6@hotmail.com> wrote in message news:<2ib51kFlap41U1@uni-berlin.de>...
> "Gav" <gavin@my-deja.com> wrote in message
> news:7da6364d.0406040145.3661cd46@posting.google.com...
> > Hi all,
> >
> > Just put together my new system with 4 * 80mm case fans (its located
> > in a very warm room).
> >
> > I am being irritated by what I have discovered is called the "beat"
> > frequency caused by the slight differences in fan speeds, resulting in
> > a "throbbing" sound...
>
> I had the same problem, but with 1 x 120mm, 2 x 80mm, 1 x 92mm + psu fans.
> I don't think that the speeds have to be close even, the beats are iirc
> certain harmonics resonating.
> >
> > The fans are marketed as quiet ones - its not the overall noise that
> > bothers me, its just the variation thats irritating.
> >
> > Do I have any options other that ear plugs/loud music? Looking in the
> > BIOS I see that the fan speed vary in RPMs a little as I would expect
> > - what percentage variance is normal? I suspect the fans would all
> > have to run at "precisely" the same speed to avoid the noise in any
> > case....
>
> Without expensive control equipment / fans, you can't run them at exactly
> the same speed.
>
> >
> > Ultimately I am more concerned about having a cool system than a quiet
> > one so i can live with it but it seems to me that given the current
> > nature of PC cooling requirements many people must experience this
> > "beat" frequency annoyance.
> >
> I got two Zalman Fanmates and played with the speeds of the 120 and the 92,
> I probably only droppped them by 100rpm and it cured the beats. You may
> have to play around for a while over a few days to get it cured. Mine come
> back slightly now and again, it's probably related to air temp, pressure and
> all sorts of complicated variables.
>

hey thanks for your response.
Yeah I agree there has to be a whole bunch of variables involved - the
PC is located in a room that gets particularly hot, in fact getting a
new case with 4 fans has *drastically* reduced the system temp - the
increased noise is the the price I paid however. Still, its better
than an overheating system...

I try to adhere to the "if it aint broke dont fix it" philosophy so
rather than tinkering (and making things worse as seems to happen all
to often to me!) I might just play some music to cover the din!

A friend of mine has just opted for an expensive water cooling system
so if he has success with that I might look into it.



> >
> > thanks for any thoughts
>
> HTH

cheers

 

[Guest]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

To avoid the beat frequency problem you need to keep the fans from
running at speeds that are too close to one another. So, just use a
controller to stagger the speed of your fans. Fan controllers that
independently control the speed of up to 4 fans are fairly cheap. Some
good info on fan controllers can be found at:
http://www.silentpcreview.com/section13.html

"Gav" <gavin@my-deja.com> wrote in message
news:7da6364d.0406040145.3661cd46@posting.google.com...
> Hi all,
>
> Just put together my new system with 4 * 80mm case fans (its located
> in a very warm room).
>
> I am being irritated by what I have discovered is called the "beat"
> frequency caused by the slight differences in fan speeds, resulting in
> a "throbbing" sound...
>
> The fans are marketed as quiet ones - its not the overall noise that
> bothers me, its just the variation thats irritating.
>
> Do I have any options other that ear plugs/loud music? Looking in the
> BIOS I see that the fan speed vary in RPMs a little as I would expect
> - what percentage variance is normal? I suspect the fans would all
> have to run at "precisely" the same speed to avoid the noise in any
> case....
>
> Ultimately I am more concerned about having a cool system than a quiet
> one so i can live with it but it seems to me that given the current
> nature of PC cooling requirements many people must experience this
> "beat" frequency annoyance.
>
>
> thanks for any thoughts

 

[Guest]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

"Dave" wrote:
>
> Get a fan bus.

Is anyone thinking about Neil Cassidy at this point?

Jon

 

[Spajky]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

On 4 Jun 2004 02:45:16 -0700, gavin@my-deja.com (Gav) wrote:

>I am being irritated by what I have discovered is called the "beat"
>frequency caused by the slight differences in fan speeds, resulting in
>a "throbbing" sound...
>
>The fans are marketed as quiet ones - its not the overall noise that
>bothers me, its just the variation thats irritating.

on the "blowing out" fans serially connect a diode to reduce for
approx. 0,8V their voltage (10% less Rpm max) & silence them more like
I did 8see my site also under comp/mods section ...
--
Regards, SPAJKY ®
& visit my site @ http://www.spajky.vze.com
"Tualatin OC-ed / BX-Slot1 / inaudible setup!"
E-mail AntiSpam: remove ##

 

[Guest]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

Spajky <Spajky##@volja.net> wrote in message news:<c2e3c0tijbf2r2olf8cs36jqb339m817g7@4ax.com>...
> On 4 Jun 2004 02:45:16 -0700, gavin@my-deja.com (Gav) wrote:
>
> >I am being irritated by what I have discovered is called the "beat"
> >frequency caused by the slight differences in fan speeds, resulting in
> >a "throbbing" sound...
> >
> >The fans are marketed as quiet ones - its not the overall noise that
> >bothers me, its just the variation thats irritating.
>
> on the "blowing out" fans serially connect a diode to reduce for
> approx. 0,8V their voltage (10% less Rpm max) & silence them more like
> I did 8see my site also under comp/mods section ...

hey guys,

Yeah my case fans came with little diode attachments to do just that
if they were too noisy. I am not keen to reduce the fans
effectiveness however, its been an ongoing battle to keep my PC cool -
its located in a room that is part of a "Mezzanine" layout
(split-level room) and all the hot air ends up there so its a really
hot environment. Currently the case temp is 34 degrees C and the CPU
52 - this is a VAST improvement over what it was before! Noise is
preferable to overheating in the end of the day.

reducing the fan speed will help the noise but at the moment the
system temp is only just within acceptible boundaries I think...