John H wrote in message
news
I need a physics lesson. Assuming sea level, how do you convert
between sound power (bels) and sound pressure (dBA)? I think
you'd have to assume that the acoustic power is being emitted
equally in all directions (which may not be true for HDs).

The other problem is that some noises hard drives make
can be MUCH more irritating than others, even when they
are identical as far as the measurement is concerned.

WD tells you only the pressure (34 dBA for the 250 GB
Caviar SE) while most other manufacturers tell you only the
power (2.5 bel for the DiamondMax Plus 9 and Barracuda V).

And that last is an illustration of the problem. Most
find that the Barra is significantly quieter than that
Maxtor drive. And the Samsung P80 is much quieter
than the Maxtor, even tho its listed at 2.7 bel.

How do you compare apples and oranges?

Obviously you cant.

Which is better to know, bels or dBA?

The only thing you can really say is that bels are
most commonly cited but clearly have a problem.

I'm thinking that (for HDs anyway) 2.5 bels is less than
25dBA SPL, which makes the WD very noisy by comparison.

And in practice thats bull****, particularly
when compared with the Maxtor.

(I have a cooling fan that's 3.5 bels and 12dBA)

http://www.silentmaxx.net/know_how/a...ccoustics.html
http://www.atra.mod.uk/atra/rsabst/p...5-Decibels.pdf