Understanding actual meaning of dBa fans produce

[gustavo]

In order to choose a cpu heatsink-fan combo I give priority number1 to the noise issue.

I have found the unit of measure they give at the datasheets is dBa an then numbers in the range from 24 dBa to 47 dBa (The Volcano 7 at high speed).

Could you help me understand, without listening to the actual noise how to make myself an idea of the noise or the differences through the differences in numbers ?

Anything would be useful, what is a silent number on so on.

Thanks Gustavo.-

 

[BoomAM]

Hi,
3dBa is the equilivent of doubleing the noise level.
Not all fan sounds are the same, what i mean is, some make a "wirring" sound, where as others "humm".
Below 30dBa is a good figure, but anything below 20dBa is almost inaudible.

Dont forget that making your CPU HSF quieter, wont make you`re pc quieter overall by much you have to take into account other stuff in the PC such as PSU fans, case fans, mobo HSF(if you have one), video card HSF, HD noise, CD/DVD noise ect;

A good, quiet & cool option is the one that i chose, a Thermalright SLK-800 & a Silent YS-Tech 80mm (27CFM, 20dBa). This cools very well, still room for overclocking as well. Also, if you want it to cool a faster chip or just run your existing chip cooler, then just replace the fan, and not the heatsink itself.

Hope this helps

 

[Wolfsraider]

the lower the number the better

higher numbers are louder

there was a site that let you download clips of the sounds of their fans to listen to the differences but that was earlier this spring that i ran across it and can't remember the site sorry

hth

mike

 

[CaptnKirk]

A 'Decibel' (dBa) level of 32 is about where your fan puts out enough sound volume where it is noticed. The higher that it goes up from
there indicates how much more annoying it gets - that 47dBa rating is pretty high considering a jet plane engine is 100dBa,
and a Who concert is about 110. That would make it not quite half as loud as the Who, and half as annoying as a jet airplane.

Any level below about 38dBa is acceptable, but if you get an Adjustable Fan you get the ability
to turn up - or down - the airflow volume, the speed, and therefore the dBA noise level of the system, and if needed, turn it back up.

 

[ThurzNite]

I saw a site 3 years ago that listed dba of about 50 fans. does anybody have that site or a similar site comparing noise level vs air flow? thanx!
Jae
edit: just found this site: http://www.sidewindercomputers.com/tecar.html but i was hoping for more comparisons.

 

[gsiener]

I'm pretty sure that the steps in dB are not linear, I believe it's log scale. So From 20 to 40 is 10 times as loud, not twice. Or something like that.

 

[Necrolezbeast]

yeah, there's no way one 50dba fan is 1/2 as loud as a jet engine....I don't think my ears would ever stop ringing..

 

[PullMyFinger]

First, let me clarify that there is a dramatic difference between dB and dBa. Overall dB sound pressure level ("loudness") is the logrithmic sum of the sound pressure levels at a set number of discrete frequencies, usually 32Hz, 62.5Hz, 125Hz, 250Hz, 500Hz, 1KHz, 2KHz, 4Khz, 8KHz, and 16Khz.

Refering to dBa sound pressure level means that each of the measured discrete frequency sound pressure levels is adjusted up or down by a value in order to mimic the way the human ear responds to those frequencies. Human hearing is most "accurate" or sensitive around the 500Hz to 2KHz region because that is where the majority of speech and communication occurs. We are also more tolerant of very low frequencies, 32Hz and below. Therefore, the a-weighting scale adds several dB to each of the mid-frequency values, and deducts several dB from the lowest frequencies.

This applies to heat sinks and fans because when comparing equal cfm fans of different size, a larger, lower speed fan will produce an overall tone which is lower and less offensive to the human ear than a higher pitched, faster spinning fan, even if both fans have the same dBa reading.

And yes, BoomAM is correct, a 3 dB increase represents a doubling in sound pressure level because of the logrithmic scale.

As far as overall sound levels, humans can't really hear anything less than 20 dBa, a very quiet library might be around 24 dBa, a luxury car on the highway is around 60 dBa.

Hope this helps.

 

[Ketchup]

I beleive the site everyone is talking about is http://www.sidewindercomputers.com. They have a "listening room" when you can listen to most of the fans they sell. I have ordered things from their site, and they usually ship things out the same day. Very nice site with good products and decent prices. And they don't rip you off on shipping costs either.