[bornfree]

How much noise will three 8dB(A) fans make?

Any idea?

[William Sommerwerck]

Assuming they're identical and near each other, three times the noise.
That's about 5dB more.

[Scott Dorsey]

bornfree wrote:
How much noise will three 8dB(A) fans make?

Any idea?

Depends where you put them. 8 dBA is so little that I would be suspicious
of that number. Put put any fan facing toward a surface that causes
turbulence, and you get a lot of noise.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Ty Ford]

On Sat, 5 Jan 2008 09:29:35 -0500, bornfree wrote
(in article
):

How much noise will three 8dB(A) fans make?

Any idea?

how close to what?

Ty Ford

--Audio Equipment Reviews Audio Production Services
Acting and Voiceover Demos http://www.tyford.com
Guitar player?:http://www.youtube.com/watch?v=4RZJ9MptZmU

[Mark]

How much noise will three 8dB(A) fans make?

Any idea?


8dBA is very low

3 of them will increase by:

10*log(3) = 4.8 dB
20*log(3) = 9.5 dB

The INCREASE will be between 4.8 dB and 9.5 dB depending upon a lot of
variables.

Mark

[Jens Rodrigo]

bornfree wrote:
How much noise will three 8dB(A) fans make?
Any idea?


This calculator can really help:
http://www.sengpielaudio.com/calculator-spl.htm

Cheers Jens Rodrigo

[Peter Larsen[_2_]]

bornfree wrote:

How much noise will three 8dB(A) fans make?

They are semi-coherent sources, and probably increase with some 4.5 dB pr.
doubling, at a guess without using a calculator you end up with a 7 dB
increase.


A lot of things that probably aren't equal assumed equal.


Kind regards

Peter Larsen

[Arny Krueger]

"William Sommerwerck" wrote in
message

Assuming they're identical and near each other, three
times the noise. That's about 5dB more.

True only if they are phase-locked. If they are AC powered, there's a
pretty good chance of that. If they are DC powered, then they will be
turning at similar but not identical speeds.

If the fans can be modelled as statistically independent acoustical sources,
then you add their power using the square root of the sum of the squares.

[William Sommerwerck]

"Arny Krueger" wrote in message
. ..
"William Sommerwerck" wrote in
message

Assuming they're identical and near each other, three
times the noise. That's about 5dB more.

True only if they are phase-locked. If they are AC powered,
there's a pretty good chance of that. If they are DC powered,
then they will be turning at similar but not identical speeds.

If the fans can be modelled as statistically independent acoustical
sources, then you add their power using the square root of the sum
of the squares.

I think you need to re-think this.

I was assuming random noise (primarily from air motion). In such cases, the
powers simply add.

[Randy Yates]

bornfree writes:

How much noise will three 8dB(A) fans make?

About as much as a gnat farting a hundred yards away.

These are REALLY quiet fans - three of them will, at a
maximum, have a noise level that is 12 dB LOWER than the
noise floor in a VERY quiet studio.
--
% Randy Yates % "Midnight, on the water...
%% Fuquay-Varina, NC % I saw... the ocean's daughter."
%%% 919-577-9882 % 'Can't Get It Out Of My Head'
%%%% % *El Dorado*, Electric Light Orchestra
http://www.digitalsignallabs.com

[Eeyore]

bornfree wrote:

How much noise will three 8dB(A) fans make?

About 12 dBA

Graham

[Eeyore]

William Sommerwerck wrote:

Assuming they're identical and near each other, three times the noise.
That's about 5dB more.

That's for coherent sources.

It'll be less.

Graham

[Eeyore]

Mark wrote:

How much noise will three 8dB(A) fans make?

Any idea?


8dBA is very low

3 of them will increase by:

10*log(3) = 4.8 dB
20*log(3) = 9.5 dB

The INCREASE will be between 4.8 dB and 9.5 dB depending upon a lot of
variables.

They're not pure tones.

They WILL NOT add like that.

Graham

[Randy Yates]

Eeyore writes:

Mark wrote:

How much noise will three 8dB(A) fans make?

Any idea?


8dBA is very low

3 of them will increase by:

10*log(3) = 4.8 dB
20*log(3) = 9.5 dB

The INCREASE will be between 4.8 dB and 9.5 dB depending upon a lot of
variables.

They're not pure tones.

They WILL NOT add like that.

Mark's answer is correct. Let me add that I also don't think anyone has
formulated all of the relevent statistical properties correctly.

If Z(t) is a wide-sense-stationary random process, then the
Wiener-Khinchine theorem states [garcia, p.380] that the power spectral
density of the process is the Fourier transform of its autocorrelation
function, where the autocorrelation function of a wide-sense-stationary
random process Z is defined as

R_Z(tau) = E[Z(t) * Z(t + tau)].

Thus by Wiener Khinchine,

R_Z(tau) = \int_{-inf}{+inf} S_Z(omega) * e^(j * omega * t) d omega,

from where we observe that the total power in the random process Z is

R_Z(0) = E[Z(t)^2].

Now let Z be the sum of three identically-distributed,
wide-sense-stationary random variables W, X, and Y. Thus Z is wide-sense
stationary and the power in their sum is

P_T = E[Z(t)^2]
= E[ (W(t) + X(t) + Y(t))^2 ]

At this point, we drive the independent variable t and consider these
three random variables W, X, and Y. Then

P_T = E[W^2] + E[X^2] + E[Y^2] + 2 * (E[W * X] + E[W * Y] + E[X * Y]).

If W, X, and Y are all pair-wise uncorrelated, then E[A * B] = E[A] *
E[b], where A, B = W, X, or Y. Since these random variables are
identically distributed, E[A] = m, and thus an uncorrelated pair is

E[A] * E[b] = m^2.

Thus the total power if the signals are uncorrelated is

P_T = 3 * P + 6 * m^2.

Now if each random process is also zero-mean (which would be
true for an acoustic signal), then the uncorrelated total power is

P_T = 3 * P,

or about 4.77 dB above P.

However, if the signals are pair-wise perfectly correlated, then

E[A * B] = E[A^2]
= P

and

P_T = 3 * P + 6 * P
= 9 * P,

or about 9.5 dB about P.

--Randy

@book{garcia,
title = "Probability and Random Processes for Electrical Engineering",
author = "{Alberto~Leon-Garcia}",
publisher = "Addison-Wesley",
year = "1989"}

--
% Randy Yates % "Watching all the days go by...
%% Fuquay-Varina, NC % Who are you and who am I?"
%%% 919-577-9882 % 'Mission (A World Record)',
%%%% % *A New World Record*, ELO
http://www.digitalsignallabs.com

[Randy Yates]

Randy Yates writes:

At this point, we drive the independent variable t
^^^^^
drop!
--
% Randy Yates % "Watching all the days go by...
%% Fuquay-Varina, NC % Who are you and who am I?"
%%% 919-577-9882 % 'Mission (A World Record)',
%%%% % *A New World Record*, ELO
http://www.digitalsignallabs.com

[William Sommerwerck]

"Randy Yates" wrote in message
...

Now if each random process is also zero-mean (which would be
true for an acoustic signal), then the uncorrelated total power is

P_T = 3 * P,

or about 4.77 dB above P.

Thanks for the math, but I got the same answer simply by assuming they were
uncorrelated sounds and adding them. Three times the power is slightly less
than 5dB.

[Ty Ford]

On Sat, 5 Jan 2008 18:30:35 -0500, Eeyore wrote
(in article ):



bornfree wrote:

How much noise will three 8dB(A) fans make?

About 12 dBA

Graham


So if a TLM 103 (7db-A selfnoise mic) is being used, how far away do the fans
have to be to fall below its noise floor?

Regards,

Ty Ford



--Audio Equipment Reviews Audio Production Services
Acting and Voiceover Demos http://www.tyford.com
Guitar player?:http://www.youtube.com/watch?v=4RZJ9MptZmU

[Randy Yates]

"William Sommerwerck" writes:

Thanks for the math, but I got the same answer simply by assuming

Exactly. My point was to remove the assumptions, or at least show
what they were.
--
% Randy Yates % "Remember the good old 1980's, when
%% Fuquay-Varina, NC % things were so uncomplicated?"
%%% 919-577-9882 % 'Ticket To The Moon'
%%%% % *Time*, Electric Light Orchestra
http://www.digitalsignallabs.com

[Scott Dorsey]

Audix Unavailable wrote:

Don't forget that the 8dB(A) spec is probably utter marketing
bull****. If you can hear one operating 1 metre away it certainly
isn't 8dB(A).

And even if it isn't bull****, as soon as you put the fan in the cabinet
where there is turbulant airflow, the noise from that will be louder than
the noise of the fan itself.

I have personal experience of so called 8dB(A) computer fans that
(when suspended in free air) could be heard 6 metres away in a very
quiet domestic room. The room on its own measured 23dB(A) with a
calibrated class 1 precision sound level meter. Fans were of Chinese
origin and were 1500 rpm 60x60mm type.

That seems about typical. Certainly no more inaccurate than the 9dBA
noise floor that Feilo claims of their microphones.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[William Sommerwerck]

"Scott Dorsey" wrote in message
...

And even if it isn't bull****, as soon as you put the fan in the
cabinet where there is turbulant airflow, the noise from that
will be louder than the noise of the fan itself.

Isn't it "assumed" that the fan noise includes the sound of the turbulent
airflow? In a sense, the airflow _is_ the sound of the fan.

[Scott Dorsey]

William Sommerwerck wrote:
"Scott Dorsey" wrote in message
...

And even if it isn't bull****, as soon as you put the fan in the
cabinet where there is turbulant airflow, the noise from that
will be louder than the noise of the fan itself.

Isn't it "assumed" that the fan noise includes the sound of the turbulent
airflow? In a sense, the airflow _is_ the sound of the fan.

That measurement is almost certainly made in free space, with nothing
other than the fan to constrain the airflow. Put the fan in front of
a heatsink and you now have lots of noise from the air on the heatsink.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Arny Krueger]

"William Sommerwerck" wrote in
message
"Arny Krueger" wrote in message
. ..
"William Sommerwerck" wrote
in message


Assuming they're identical and near each other, three
times the noise. That's about 5dB more.

True only if they are phase-locked. If they are AC
powered, there's a pretty good chance of that. If they
are DC powered,
then they will be turning at similar but not identical
speeds.

If the fans can be modelled as statistically independent
acoustical sources, then you add their power using the
square root of the sum of the squares.

I think you need to re-think this.

Nope. I learned all about this, both theory and lab experiments, back in the
early 1970s.

I was assuming random noise (primarily from air motion).
In such cases, the powers simply add.

Nope. Please see:

http://www.rose-hulman.edu/~black/Noise/img011.gif

The general rule for adding signals is that they add algebraically only if
they have identically the same frequency.

Most noise signals have anything but the same identically same frequency.
Then they are best added using the square root of the sum of the squares.

[Randy Yates]

"Arny Krueger" writes:

"William Sommerwerck" wrote in
message
"Arny Krueger" wrote in message
. ..
"William Sommerwerck" wrote
in message


Assuming they're identical and near each other, three
times the noise. That's about 5dB more.

True only if they are phase-locked. If they are AC
powered, there's a pretty good chance of that. If they
are DC powered,
then they will be turning at similar but not identical
speeds.

If the fans can be modelled as statistically independent
acoustical sources, then you add their power using the
square root of the sum of the squares.

I think you need to re-think this.

Nope. I learned all about this, both theory and lab experiments, back in the
early 1970s.

I was assuming random noise (primarily from air motion).
In such cases, the powers simply add.

Nope. Please see:

http://www.rose-hulman.edu/~black/Noise/img011.gif

The general rule for adding signals is that they add algebraically only if
they have identically the same frequency.

Most noise signals have anything but the same identically same frequency.
Then they are best added using the square root of the sum of the
squares.

I think you're confusing adding voltages with adding powers. If two
signals are uncorrelated and zero-mean (and WSS), then their powers
add algebraically (P1 + P2) but their voltages add as the sum of
squares ((V1^2 + V2^2)^(1/2)).
--
% Randy Yates % "My Shangri-la has gone away, fading like
%% Fuquay-Varina, NC % the Beatles on 'Hey Jude'"
%%% 919-577-9882 %
%%%% % 'Shangri-La', *A New World Record*, ELO
http://www.digitalsignallabs.com

[William Sommerwerck]

"Arny Krueger" wrote in message
...
"William Sommerwerck" wrote in
message
"Arny Krueger" wrote in message
. ..
"William Sommerwerck" wrote
in message


Assuming they're identical and near each other, three
times the noise. That's about 5dB more.

True only if they are phase-locked. If they are AC
powered, there's a pretty good chance of that. If they
are DC powered,
then they will be turning at similar but not identical
speeds.

If the fans can be modelled as statistically independent
acoustical sources, then you add their power using the
square root of the sum of the squares.

I think you need to re-think this.

Nope. I learned all about this, both theory and lab experiments,
back in the early 1970s.

I was assuming random noise (primarily from air motion).
In such cases, the powers simply add.

Nope. Please see:

http://www.rose-hulman.edu/~black/Noise/img011.gif

The general rule for adding signals is that they add algebraically only if
they have identically the same frequency.

But that's the point. They aren't supposed to be added algebraically,
because they aren't identical.


Most noise signals have anything but the same identically same frequency.
Then they are best added using the square root of the sum of the squares.

This makes no sense. If I have multiple uncorrelated noise signals, their
powers simply add. 8dB + 8dB = 11dB, not 14dB.

[Peter Larsen[_2_]]

Arny Krueger wrote:


[quoting someone]

I was assuming random noise (primarily from air motion).
In such cases, the powers simply add.


Nope. Please see:

http://www.rose-hulman.edu/~black/Noise/img011.gif

The general rule for adding signals is that they add algebraically
only if they have identically the same frequency.

Most noise signals have anything but the same identically same
frequency. Then they are best added using the square root of the sum
of the squares.

This is not fully random, they are correlated enough to be likely to exhibit
beat tones.


Kind regards

Peter Larsen

[Arny Krueger]

"Peter Larsen" wrote in message

Arny Krueger wrote:


[quoting someone]

I was assuming random noise (primarily from air motion).
In such cases, the powers simply add.

Nope. Please see:

http://www.rose-hulman.edu/~black/Noise/img011.gif

The general rule for adding signals is that they add
algebraically only if they have identically the same
frequency.

Most noise signals have anything but the same
identically same frequency. Then they are best added
using the square root of the sum of the squares.

This is not fully random, they are correlated enough to
be likely to exhibit beat tones.

Definately true for AC synchronous motors. Questionable for DC motors. Fans
may use either kind of motor.

[Mark]

On Jan 7, 8:29*am, "Arny Krueger" wrote:
"Peter Larsen" wrote in message







Arny Krueger wrote:

[quoting someone]

I was assuming random noise (primarily from air motion).
In such cases, the powers simply add.
Nope. Please see:
http://www.rose-hulman.edu/~black/Noise/img011.gif
The general rule for adding signals is that they add
algebraically only if they have identically the same
frequency.

Most noise signals have anything but the same
identically same frequency. Then they are best added
using the square root of the sum of the squares.
This is not fully random, they are correlated enough to
be likely to exhibit beat tones.

Definately true for AC synchronous motors. Questionable for DC motors. Fans
may use either kind of motor.- Hide quoted text -

- Show quoted text -

Exactly why I said:
"The INCREASE will be between 4.8 dB and 9.5 dB depending upon a lot
of variables."

10*log(3)= 4.8 dB applies for the fully random case
20*log(3)= 9.5 dB applies for the fully correlated case
In practice the answer will fall between those 2 numbers.
Mark

[Randy Yates]

Mark writes:
[...]
10*log(3)= 4.8 dB applies for the fully random case

Right number, wrong or incomplete justification. 4.8 dB for the
uncorrelated, zero-mean, wide-sense stationary case.
--
% Randy Yates % "...the answer lies within your soul
%% Fuquay-Varina, NC % 'cause no one knows which side
%%% 919-577-9882 % the coin will fall."
%%%% % 'Big Wheels', *Out of the Blue*, ELO
http://www.digitalsignallabs.com

[Mark]

On Jan 8, 10:33*am, Randy Yates wrote:
Mark writes:
[...]
10*log(3)= 4.8 dB applies for the fully random case

Right number, wrong or incomplete justification. 4.8 dB for the
uncorrelated, zero-mean, wide-sense stationary case.
--
% *Randy Yates * * * * * * * * *% "...the answer lies within your soul
%% Fuquay-Varina, NC * * * * * *% * * * 'cause no one knows which side
%%% 919-577-9882 * * * * * * * *% * * * * * * * * * the coin will fall."
%%%% * * * * * % *'Big Wheels', *Out of the Blue*, ELOhttp://www.digitalsignallabs.com

Agreed... but we are talking about fans, could it be any other
way? :-)
Mark

[bornfree]

On 6 Jan, 13:06, Audix wrote:
On Sat, 05 Jan 2008 12:10:59 -0500, Randy Yates
wrote:

bornfree writes:

How much noise will three 8dB(A) fans make?

About as much as a gnat farting a hundred yards away.

These are REALLY quiet fans - three of them will, at a
maximum, have a noise level that is 12 dB LOWER than the
noise floor in a VERY quiet studio.

Very true!

Don't forget that the 8dB(A) spec is probably utter marketing
bull****. If you can hear one operating 1 metre away it certainly
isn't 8dB(A).

I have personal experience of so called 8dB(A) computer fans that
(when suspended in free air) could be heard 6 metres away in a very
quiet domestic room. The room on its own measured 23dB(A) with a
calibrated class 1 precision sound level meter. Fans were of Chinese
origin and were 1500 rpm 60x60mm type.

I have faith. I use one of the 8dbA fans on a daily basis. They are
made by noctua, an Austrian company with lots of boffins working for
them.

They are, without a doubt the best fans ever made. Nothing made by any
other company even comes close.

Check the fan out if you want.. http://www.quietpc.com/gb-en-gbp/pro...ans/nf-s12-800

[Arny Krueger]

"bornfree" wrote in message

On 6 Jan, 13:06, Audix wrote:
On Sat, 05 Jan 2008 12:10:59 -0500, Randy Yates
wrote:

bornfree writes:

How much noise will three 8dB(A) fans make?

About as much as a gnat farting a hundred yards away.

These are REALLY quiet fans - three of them will, at a
maximum, have a noise level that is 12 dB LOWER than the
noise floor in a VERY quiet studio.

Very true!

Don't forget that the 8dB(A) spec is probably utter
marketing bull****. If you can hear one operating 1
metre away it certainly isn't 8dB(A).

I have personal experience of so called 8dB(A) computer
fans that (when suspended in free air) could be heard 6
metres away in a very quiet domestic room. The room on
its own measured 23dB(A) with a calibrated class 1
precision sound level meter. Fans were of Chinese origin
and were 1500 rpm 60x60mm type.

I have faith. I use one of the 8dbA fans on a daily
basis. They are
made by noctua, an Austrian company with lots of boffins
working for them.

It doesn't take a boffin to know that if you turn a fan very slow, it won't
make much noise. Trouble is, it won't move much air, either.

They are, without a doubt the best fans ever made.

Compare and contrast with a similar-sized competitive fans turning at the
same very slow speed.

Nothing made by any other company even comes close.

A 120 mm fan that moves 35 CFM is not news. A normal 120 mm fan might move
80 cfm.

http://www.quietpc.com/gb-en-gbp/pro...ans/nf-s12-800

[William Sommerwerck]

"Arny Krueger" wrote in message
...

It doesn't take a boffin to know that if you turn a fan very slow, it
won't make much noise. Trouble is, it won't move much air, either.

Isn't the issue whether it moves _enough_?

It might be that the Noctua fans have a blade design that moves an adequate
amount of air with unusually low noise. I don't know. I do know that I wish
the fans on my computer were quieter. They're not noisy in an absolute
sense, but I'd rather they made no noise at all.

Years ago I read an engineering paper from an American fan manufacturer.
Their point was that the volume of air moved was not quite as important as
the way the air moved through the device. Their idea was that the air flow
should be broken up, so that air moved past every heat source in the device.
This was best achieved by asymmetrical fan mounting, and by pushing air into
the case rather than sucking it out.

The fans in my computer's cabinet work that way. Two at the back suck air
in, while one at the front -- NOT mounted in a line with either of the two
rear fans -- sucks it out.

Two or three small, quiet fans, will probably do a better job than one
large, "noisy" fan.

[Don Pearce]

On Sat, 12 Jan 2008 04:49:47 -0800, "William Sommerwerck"
wrote:

"Arny Krueger" wrote in message
...

It doesn't take a boffin to know that if you turn a fan very slow, it
won't make much noise. Trouble is, it won't move much air, either.

Isn't the issue whether it moves _enough_?

It might be that the Noctua fans have a blade design that moves an adequate
amount of air with unusually low noise. I don't know. I do know that I wish
the fans on my computer were quieter. They're not noisy in an absolute
sense, but I'd rather they made no noise at all.

Years ago I read an engineering paper from an American fan manufacturer.
Their point was that the volume of air moved was not quite as important as
the way the air moved through the device. Their idea was that the air flow
should be broken up, so that air moved past every heat source in the device.
This was best achieved by asymmetrical fan mounting, and by pushing air into
the case rather than sucking it out.

The fans in my computer's cabinet work that way. Two at the back suck air
in, while one at the front -- NOT mounted in a line with either of the two
rear fans -- sucks it out.

Two or three small, quiet fans, will probably do a better job than one
large, "noisy" fan.


You are right. For maximum cooling it is important that the air flow
is turbulent - laminar flow will always show a slow temperature
gradient away from the source which means it effectively provides
insulation. That is most certainly not what you need for cooling.

Unfortunately turbulence implies noise. The real quiet alternative is
the fanless heat sink, usually loads of heat pipes and an awful lot of
metal.

d

--
Pearce Consulting
http://www.pearce.uk.com

[bornfree]

On 12 Jan, 10:31, "Arny Krueger" wrote:
"bornfree" wrote in message





On 6 Jan, 13:06, Audix wrote:
On Sat, 05 Jan 2008 12:10:59 -0500, Randy Yates
wrote:

bornfree writes:

How much noise will three 8dB(A) fans make?

About as much as a gnat farting a hundred yards away.

These are REALLY quiet fans - three of them will, at a
maximum, have a noise level that is 12 dB LOWER than the
noise floor in a VERY quiet studio.

Very true!

Don't forget that the 8dB(A) spec is probably utter
marketing bull****. If you can hear one operating 1
metre away it certainly isn't 8dB(A).

I have personal experience of so called 8dB(A) computer
fans that (when suspended in free air) could be heard 6
metres away in a very quiet domestic room. The room on
its own measured 23dB(A) with a calibrated class 1
precision sound level meter. Fans were of Chinese origin
and were 1500 rpm 60x60mm type.

I have faith. I use one of the 8dbA fans on a daily
basis. They are
made by noctua, an Austrian company with lots of boffins
working for them.

It doesn't take a boffin to know that if you turn a fan very slow, it won't
make much noise. Trouble is, it won't move much air, either.

You IGNORANT cynic! The reason these fans are better than any other is
because they shift more air per dbA than any other.

They are, without a doubt the best fans ever made.

Compare and contrast with a similar-sized competitive fans turning at the
same very slow speed.

Noctua make 12cm fans that spin at 800rpm, 1200rpm and 1300rpm. Every
single fan they make pushes more air per db than anything else
currently on the market.

Nothing made by any other company even comes close.

A 120 mm fan that moves 35 CFM is not news. A normal 120 mm fan might move
80 cfm.


The point here is that the fan pushes 35 CFM while making just EIGHT
dbA. There are no other commercially available fans that move as much
air with as little noise. So do yourself a favour and research the
matter more thoroughly before you embarrass yourself.

[Mark]

On Jan 12, 10:18*am, bornfree wrote:
On 12 Jan, 10:31, "Arny Krueger" wrote:





"bornfree" wrote in message



On 6 Jan, 13:06, Audix wrote:
On Sat, 05 Jan 2008 12:10:59 -0500, Randy Yates
wrote:

bornfree writes:

How much noise will three 8dB(A) fans make?

About as much as a gnat farting a hundred yards away.

These are REALLY quiet fans - three of them will, at a
maximum, have a noise level that is 12 dB LOWER than the
noise floor in a VERY quiet studio.

Very true!

Don't forget that the 8dB(A) spec is probably utter
marketing bull****. If you can hear one operating 1
metre away it certainly isn't 8dB(A).

I have personal experience of *so called 8dB(A) computer
fans that (when suspended in free air) could be heard 6
metres away in a very quiet domestic room. The room on
its own measured 23dB(A) with a calibrated class 1
precision sound level meter. Fans were of Chinese origin
and were 1500 rpm 60x60mm type.

I have faith. I use one of the 8dbA fans on a daily
basis. They are
made by noctua, an Austrian company with lots of boffins
working for *them.

It doesn't take a boffin to know that if you turn a fan very slow, it won't
make much noise. *Trouble is, it won't move much air, either.

You IGNORANT cynic! The reason these fans are better than any other is
because they shift more air per dbA than any other.

They are, without a doubt the best fans ever made.

Compare and contrast with a similar-sized competitive fans turning at the
same very slow speed.

Noctua make 12cm fans that spin at 800rpm, 1200rpm and 1300rpm. Every
single fan they make pushes more air per db than anything else
currently on the market.

Nothing made by any *other company even comes close.

A 120 mm fan that moves 35 CFM is not news. A normal 120 mm fan might move
80 cfm.

The point here is that the fan pushes 35 CFM while making just EIGHT
dbA. There are no other commercially available fans that move as much
air with as little noise. So do yourself a favour and research the
matter more thoroughly before you embarrass yourself.- Hide quoted text -

- Show quoted text -

Arne is right. It is easy to make a fan that moves a lot of air per
dBa. All you have to do is make the fan BIG and turn it slowly.

If you want a quiet fan, use a big fan that is about twice the size
that you normally need and run it on a lower voltage. It will be very
quiet and will last a long time. Take a 12 Volt fan and put a 12V car
bulb in series with it. It will run slow and be quiet. Use a fan
that is big enough to push enough air even though it is running slow.

Now the trick would be to make a fan that moves a lot of air AND is
quiet AND is small.

Mark

[bornfree]

On 12 Jan, 12:49, "William Sommerwerck"
wrote:
"Arny Krueger" wrote in message

...

It doesn't take a boffin to know that if you turn a fan very slow, it
won't make much noise. Trouble is, it won't move much air, either.

Isn't the issue whether it moves _enough_?

It might be that the Noctua fans have a blade design that moves an adequate
amount of air with unusually low noise.

Absolutely correct.

Two or three small, quiet fans, will probably do a better job than one
large, "noisy" fan.

Nearly right. A bigger fan is better because it can spin slowly and
therefore be much quieter than the equivalent small fan. This is why
if you become interested in PC silencing as I am, you will quickly
find out that it is better to have a slow spinning 120mm fan than a
faster, noisier 80mm fan.

I do know that I wish
the fans on my computer were quieter. They're not noisy in an absolute
sense, but I'd rather they made no noise at all.

If it bothers you enough you will research the issue and replace the
loud fans on your computer with quieter ones. And if you spend long
enough and try out enough fans, you will eventually realise that
Noctua make the best silent fans available.

If you are using the stock cooler that came with your computers CPU, I
guarantee your computer can be much, much quieter. Likewise if you are
using a power supply (PSU) with an 80mm fan; your computer is making
more noise than it needs to be. PSUs with 120mm fans are always, in my
wide experience, quieter.

On most computers the PSU and the CPU cooler are the 2 biggest sources
of noise.
If you want to discuss this matter further, the knowledgeable folk at
http://www.silentpcreview.com/forums/ will help you out. And if you
want to replace components in your PC, http://www.quietpc.com/ is an
excellent place to start.

[Randy Yates]

bornfree writes:

On 12 Jan, 12:49, "William Sommerwerck"
wrote:
"Arny Krueger" wrote in message

...

It doesn't take a boffin to know that if you turn a fan very slow, it
won't make much noise. Trouble is, it won't move much air, either.

Isn't the issue whether it moves _enough_?

It might be that the Noctua fans have a blade design that moves an adequate
amount of air with unusually low noise.

Absolutely correct.

Two or three small, quiet fans, will probably do a better job than one
large, "noisy" fan.

Nearly right. A bigger fan is better because it can spin slowly and
therefore be much quieter than the equivalent small fan. This is why
if you become interested in PC silencing as I am, you will quickly
find out that it is better to have a slow spinning 120mm fan than a
faster, noisier 80mm fan.

I do know that I wish
the fans on my computer were quieter. They're not noisy in an absolute
sense, but I'd rather they made no noise at all.

If it bothers you enough you will research the issue and replace the
loud fans on your computer with quieter ones.

Aren't there alternate cooling systems? Water/cryonic, or even electric
(heat pumpish?).
--
% Randy Yates % "Watching all the days go by...
%% Fuquay-Varina, NC % Who are you and who am I?"
%%% 919-577-9882 % 'Mission (A World Record)',
%%%% % *A New World Record*, ELO
http://www.digitalsignallabs.com

[Arny Krueger]

"Randy Yates" wrote in message

bornfree writes:

On 12 Jan, 12:49, "William Sommerwerck"
wrote:
"Arny Krueger" wrote in message

...

It doesn't take a boffin to know that if you turn a
fan very slow, it won't make much noise. Trouble is,
it won't move much air, either.

Isn't the issue whether it moves _enough_?

It might be that the Noctua fans have a blade design
that moves an adequate amount of air with unusually low
noise.

Absolutely correct.

Two or three small, quiet fans, will probably do a
better job than one large, "noisy" fan.

Nearly right. A bigger fan is better because it can spin
slowly and therefore be much quieter than the equivalent
small fan. This is why if you become interested in PC
silencing as I am, you will quickly find out that it is
better to have a slow spinning 120mm fan than a faster,
noisier 80mm fan.

I do know that I wish
the fans on my computer were quieter. They're not noisy
in an absolute sense, but I'd rather they made no noise
at all.

If it bothers you enough you will research the issue and
replace the loud fans on your computer with quieter ones.

Aren't there alternate cooling systems? Water/cryonic, or
even electric (heat pumpish?).

All of the above, plus heat pipes.

Heat sink/heat pipe composites have been built that claim to dissipate a
high end gamester's PC's heat generation with no moving parts.

[bornfree]

On 12 Jan, 17:00, Randy Yates wrote:
bornfree writes:
On 12 Jan, 12:49, "William Sommerwerck"
I do know that I wish
the fans on my computer were quieter. They're not noisy in an absolute
sense, but I'd rather they made no noise at all.

If it bothers you enough you will research the issue and replace the
loud fans on your computer with quieter ones.

Aren't there alternate cooling systems? Water/cryonic, or even electric
(heat pumpish?).

Why make things more complicated when good quality fans will do. Water
cooling is expensive and not necessary unless you have very hot
components.

Modern CPUs and GPUs are designed with thermal efficiency in mind.