Thanks for the nice series on quiet builds with more aggresive performance configurations (HDD and graphics).
I want to use the info to design my own system with different components to suit my particular needs, but estimating noise levels is giving me problems since some of the data seems to be far away from classical calculations for adding noises.
EG the 9 HDD server without gaming video card in mid-tower case has <19dBA with 9 HDD and <17dB with 3 of them removed. This is implies each HDD has <10dBA.
Either my math is wrong or something non-classical is happening when you take the HDD out.
Can someone give me some insight here pls?
OK, I found a quote on another build within the 70plus pages of build options that says what I said, more or less.
Effect of the Number of HDDs - Much of the impressively quiet performance can be attributed directly to the sterling acoustic properties of the Western Digital Green Power hard drives. It's hard to imagine any other stack of six HDDs measuring just 18 [email protected]
To explore the acoustic summing effect, we tried listening and measuring SPL with different numbers of WD GP drives. Removing a single drive, so that the total number of active drives was five, resulted in virtually no difference in perceived or measured noise. With two drives removed, the [email protected]
dropped by only 1 dBA, a barely noticeable difference. When just three drives were running, the difference was a total drop of 2 dBA, which is a surprisingly small improvement and less than the theoretical 3 dB difference expected. (Editor's Note: The A-weighting probably had an impact due to the relatively high proportion of lower frequencies in the total SPL of the HDD. In effect, our system with three hard drives on a wooden table was acoustically indistinguishable from the same system with six hard drives, but sitting on foam. The latter, in some subtle way, may actually be more benign to hear, perhaps because it is slightly less tonal in the lower frequency range.
Interesting that dropping out 3 HDD on two different systems gave the same 2dBA noise drop even though the noise levels of the two systems were different enough not to expect the same level of drop.
So I guess you cannot really predict noise levels of your system build, just select components and use good technique to minimize noise, and you get what you get. Only exception may be minor deviations from one of these builds eg adding an 11dBA fan should make no meaningful noise increase.
Is this a fair statement?