dBA and Bels

[John H.]

Thats nothing like indisputable. Its JUST a claim made by
that Silent PC site and those standards say nothing like that.

The Silent PC site (which I found just last night) is at least the 4th
site I've seen that says it. Look around for yourself.

If there was no computer industry standard or agreement or whatever you
want to call it, what would a noise rating of say 2.7 bels mean, 27 dBA
SPL (I'm still not sure if bel, as used in the PC industry, is really
belA or not. All the standards seem to use A-weighted power.)? Or what
would 34 dBA mean, power or pressure?

Give me a link to ONE computer product that uses bels for pressure or
decibels for power.

Bullshit. Your original question about a simple conversion
between bel and dBA, even if rephrased to make it clear that
you want a simple mathematical conversion between sound
power stated in bels and sound pressure stated in dBA is still
just plain impossible, as that site says quite unambiguously.

I think I put conditions on that: ASSUMING power was radiated equally in
all directions and it was at sea level.

The quote from Silent PC again: "Sound power levels are useful for
calculating the sound pressure level from a machine."

What I was asking for is how to do this calculation.

 

[Rod Speed]

The Silent PC site (which I found just last night)
is at least the 4th site I've seen that says it.

Sites like that tend to regurgitate the same mangling
of the real story. Thats the nature of the web.

Look around for yourself.

Dont need to thanks, I understand the basics on that.

If there was no computer industry standard

There certainly isnt that, otherwise those sites
would be able to name that standard and they cant.

or agreement
Ditto.

or whatever you want to call it, what would a noise
rating of say 2.7 bels mean, 27 dBA SPL (I'm still not
sure if bel, as used in the PC industry, is really belA or
not. All the standards seem to use A-weighted power.)?

Cant even understand the question. Try again.

Or what would 34 dBA mean, power or pressure?

Give me a link to ONE computer product that
uses bels for pressure or decibels for power.

You're the one claiming that its indisputable
when even that site says nothing like that.

I think I put conditions on that: ASSUMING power was
radiated equally in all directions and it was at sea level.

Sure, but that still isnt possible.

And no real world device like a hard drive or fan
ever does radiate equally in all directions anyway.

The quote from Silent PC again: "Sound power levels are
useful for calculating the sound pressure level from a machine."

Thats nothing like the same thing as a simple
mathematical ratio. If that was possible, they'd state it.

And as you should be able to see from the pairs you
quoted for a particular hard drive and a particular fan,
no such simple ratio actually exists.

What I was asking for is how to do this calculation.

And everyone who has chosen to comment
has pointed out that it isnt possible.

Including that site you take as gospel.

 

[Lil' Dave]

Lesson: alt.sci.physics or alt.sci.physics.acoustics

Illustrative analogy: fingernails pressed against chalkboard with downward
motion vs angelic voice singing a lullabye.

Other factors in real world that affect HD noise before reaching the user:
placement in PC case, PC case material, PC case construction techniques,
peripherals in the PC case, sound deadening techniques, fan noise and its
noise spectrum proximity to the HD noise, PC location in the room, noise
distractions in the room and their noise spectrum.
Dave

 

[John H.]

Nope, you can also use reviews.

Don't see many of those for fans.

I changed the cooler fan last night and what a difference. MUCH better,
except now I know I need to replace my older ball bearing HD too. I
guess I'll be getting a Samsung for Christmas since somebody around here
said they're supposed to be very quiet.

Turns out the PanaFlo label is on the back of the fan (actually the
normal side for a label). It says "Model FBL08A12M, 12V, 0.17A" which
is 2.04W. The specs I downloaded from Panasonic say it should be 1.49W
(the RPMs are the same - 2450 RPM).

The fan I replaced it with is a Papst "8412N/2GLE, 0.037A, 0.45W" that's
running at ~1500 RPM. The Papst specs say the 8412NGL (which I assume
is the same fan) is 0.6W and the same RPM. The Papst is quiet but I'm
not so sure it's 12 dBA. I *can* hear it - even more so, mounted on the
heat sink. It's well balanced though - I feel absolutely nothing when I
touch it

A Panaflo FBA08A12H1A I got a while back is 3W, the specs say 2.08W.

Three different fans, none of which match the specs, that "prove" you
can't believe everything they say - probably including noise ratings
too.

I used to think that el cheapo fans had sleeve bearings and the good
ones had ball bearings. I've changed my mind on that now, The el
cheapo fans often do have sleeve bearings (of low quality) but so do
some of the best fans. Quality sleeve bearing fans are not only quieter
brand new, they stay that way longer than a ball bearing fan will.

 

[Rod Speed]

Don't see many of those for fans.

Plenty for hard drives and enough for fans so you dont
have to rely completely on the manufacturer's claims.

And if you are silly enough to rely on what the
tiny little backyard 'cooler' manufacturers claim...

I changed the cooler fan last night and what a difference. MUCH better,

Some of us use cpus that have nice quiet boxed fans supplied
with them. And you can certainly trust the numbers Intel quotes.

except now I know I need to replace my older ball bearing HD too.

Yeah, my main system is now so quiet with a decent Samsung
drive that its an irritation to turn the previous main system thats
now the test system on. Wont be too long before the noises
pisses me off enough to get another samsung for that PC too.

And I did some work last week on a system with a WD400BB
thats got an irritating bearing whine. I wouldnt put up with it myself.

I guess I'll be getting a Samsung for Christmas since somebody
around here said they're supposed to be very quiet.

Yeah, love mine. I had to put my hand on it to be
sure it was actually spinning up when first installed.

Same with the cpu fan in that system, had to look closely
at the cpu fan to check it was actually spinning up.

Lovely quiet system.

Turns out the PanaFlo label is on the back of the fan (actually
the normal side for a label). It says "Model FBL08A12M, 12V,
0.17A" which is 2.04W. The specs I downloaded from Panasonic
say it should be 1.49W (the RPMs are the same - 2450 RPM).

The fan I replaced it with is a Papst "8412N/2GLE, 0.037A,
0.45W" that's running at ~1500 RPM. The Papst specs
say the 8412NGL (which I assume is the same fan)

I doubt it.

is 0.6W and the same RPM. The Papst is quiet
but I'm not so sure it's 12 dBA. I *can* hear it
- even more so, mounted on the heat sink.

Yeah, thats the other thing that few do, design the heatsink
to minimise the air noise with a matched fan and heatsink.

It's well balanced though - I feel
absolutely nothing when I touch it

A Panaflo FBA08A12H1A I got a while back is 3W, the specs say 2.08W.

Three different fans, none of which match the specs, that "prove" you
can't believe everything they say - probably including noise ratings too.

Like the Silent PC site says, noise ratings are VERY
imprecise, even if there is no intention to decieve.

And they dont even allow for the mind's perception of noise.

And noise specs of a fan in isolation are just about useless when
what matters is the combination of heatsink and fan and case.

I used to think that el cheapo fans had sleeve bearings and the good
ones had ball bearings. I've changed my mind on that now, The el
cheapo fans often do have sleeve bearings (of low quality) but so do
some of the best fans. Quality sleeve bearing fans are not only quieter
brand new, they stay that way longer than a ball bearing fan will.

And fluid bearings are a form of sleeve bearing.

 

[beenthere]

...

I changed the cooler fan last night and what a difference. MUCH better,
except now I know I need to replace my older ball bearing HD too. I
guess I'll be getting a Samsung for Christmas since somebody around here
said they're supposed to be very quiet.

Turns out the PanaFlo label is on the back of the fan (actually the
normal side for a label). It says "Model FBL08A12M, 12V, 0.17A" which
is 2.04W. The specs I downloaded from Panasonic say it should be 1.49W
(the RPMs are the same - 2450 RPM).

The fan I replaced it with is a Papst "8412N/2GLE, 0.037A, 0.45W" that's
running at ~1500 RPM. The Papst specs say the 8412NGL (which I assume
is the same fan) is 0.6W and the same RPM. The Papst is quiet but I'm
not so sure it's 12 dBA. I *can* hear it - even more so, mounted on the
heat sink. It's well balanced though - I feel absolutely nothing when I
touch it

A Panaflo FBA08A12H1A I got a while back is 3W, the specs say 2.08W.

Three different fans, none of which match the specs, that "prove" you
can't believe everything they say - probably including noise ratings
too.
...

Just wanted to jump in here as it is near and dear to my black heart.

That label rating on a fan or anything "approved" by the various
regulatory agencies really only applied to the model the manufacturer
sent to the agencies for approval testing. After that, the
manufacturer has wide opportunity to change things inside by the time
it arrives at your computer still bearing the original approval
sticker.

Of course they shouldn't..., but hey, you've all seen the typical
self selected band of scumbags management mentality at work.

Hey, how many of you guys STILL think the FDA approval means anything
on a new drug ???

If you do, you haven't been paying attention