Questions about volume (dBA) vs. fan speed

[WhiteKnight]

For variable speed fans, does the noise vs. rotation speed usually follow a linear relationship?

I'm looking at the Thermaltake Smart Fan to replace my current Panaflo 32.1 CFM/28 dbA CPU fan. The Thermaltake specs are 21.6 CFM/17 dBA @ 1300 RPM and 72.5 CFM/48.5 dBA @ 4800 RPM. Assuming a linear relationship, this would be equivalent to 39.4 CFM/28 dBA, which is an improvement over my existing fan. However, if the relationship is not linear, this of course goes out the window.

 

[Zepper]

The dBA curve is non-Linear so anything concerning perceived sound level is non-linear.
.bh.

 

[WhiteKnight]

I know that dB is a logarithmic scale, but I'm asking if fan speed is usually linear with respect to dB.

 

[Zepper]

You can expect a fairly linear relationship between CFM and RPM but not RPM and dB. Not only the dB but the qualities of the noise change over the speed range.
. But you would have to run curves to get the actual ratios (some of the mfr's sites have dB curves over the operating ranges of the fans). But intuition tells me that the rate of change in dB decreases with rpm - IOW, the dB curve would be steeper toward the beginning than the end.
Anyway, here is an article from silentPCreview.com (which all PC geeks should bookmark) that may prove helpful: Fans .

.bh.

 

[0roo0roo]

measurement is nonstandard to boot. the ratings are next to worthless.

 

[Cerb]

Thermaltake's ratings are not the same as Panasonic's. The Panaflo's ratings can be compared to Delta, Adda, NMB, etc., as such manufacturers serve more important fields, and computer OEMs, that may get ticked off when they don't see the right ISO number in the fine print. One key thing that generally tells you the fan has gone through its proper rigor is when there's a static pressure rating .

And you're best off to hook the Panaflo up to a fan controller.

 

[Cerb]

Thermaltake's ratings are not the same as Panasonic's. The Panaflo's ratings can be compared to Delta, Adda, NMB, etc., as such manufacturers serve more important fields that get ticked off when they don't see the right ISO number in the fine print.
And you're best off to hook the Panaflo up to a fan controller.

 

[hifisoftware]

No they are not related.
I tried two fans.
TT SilentCat did not get affected by voltage much. It just was quet.
Panaflo 92mm high. Voltage had a great effect on noise. This fan would get destinct internal noise come from inside at 12v. This noise disappeared at 9v (around). This internal noise was ether on or off depending on voltage.
Noise just from air (turbulence) is probably proportional for a given fan.