Fein Turbo II is rated at 58 decibles. The Shop Vac "Quiet Deluxe 6.5
HP" is rated at 82 decibels.
The rule of thumb I know is that 3 decibles corresponds to a doubling.
Thus the Shop Vac Quiet Deluxe 6.5 HP is 24 decibels louder, or 3 db +
3 db + ... + 3 db (8 times), or 2x2x2x2x2x2x2x2 = 2 to the 8'th power 256 times louder.
Is that correct? If so, holy moly!
Probably. I've got a Fein. It's reasonably quiet for a shop vac. I've
owned Shop Vac's in the past and ended up mothballing them due to the
ear shattering noise. On a subjective basis I'd say the old Shop Vac
was about 25 times louder than the Fein.
Sort of. It is a logorithmic scale and you you would be correct to say that
the amplitue of the sound wave is about 256 (actually 240) times greater.
Does that mean that percieved loudness is that much greater?.... no probably
not as that's not really how human hearing (both the ear and brain) works.
It's king of hard to objectively quantify peception.
As you may know, decibels correspond to a logarithmic scale, and a +3dB
increase requires a doubling of the power to produce the sound. After a bit
of looking, it seems that the perceived loudness is closer to being
proportional to the the dB rating. So, the Shop Vac would be perceived to
be about 40% louder than the Fein. All of this is, of course, very
subjective as it depends on the person listening, the sound frequencies
While it may be the design of the biscuit cutter, it very well may be caused
by the vaccuum. When you start pumping ~100cfm (my ShopVac claims 185 on
it, IIRC) through whatever ducts and ports are on the biscuit cutter, it may
whistle or howl a bit.
On 1 Sep 2005 12:03:45 -0700, "Never Enough Money"
As someone else pointed out, it's logarithmic, so your calculation
isn't quite. An easier way to understand it is that 10 dB is actually
10x, and the next 10 is a power of 10 (10^20). So what you have is
20dB is x100, the next 3dB doubles that to 200, and the 1dB left over
is a fraction of x2, so around 220 or so is the decimal equivalent of
It's those stray dB between 9 and 10 that messes your calculation up.
9 dB is 8x, but 10 dB is 10x.
Now you had to go and analyze it and make me go check the math. Darn I hate
it when that happens. You had it right until that very last 1 db. A 1db
increase is a 1.26x increase. (200 * 1.26) = 251+
The formula for db is 10 * log (p1/p2). Its not a pure log function.
There's a 10x factor in there. There's a very cool webpage on this with
actual sound files at http://www.phys.unsw.edu.au/~jw/dB.html .
24dB is a factor of 251.2+ according to my engineering calculator. :)
His calculation was closer than yours. <grin>
when you've got a number that is a multiple of 3dB, "doubling by 3s"
will get you very close to a 'correct' answer.
consider a factor of 30dB. 'doubling', 10 times gives you a factor of
1024x, where the 'accurate' value is 100x. 'error' is less than 2.5%.
At 60dB, the 'doubling' error is less thant 5%. on a factor of 'one million'.
"Good enough for -most- practical purposes." <grin>
Going from 58 db to 82 db in musical notation is equivalent to "ppp to fff",
or an orchestra playing about as soft as it can (ppp) to as loud as it can
(fff). A big difference. Some reference levels are given at
http://www.coolmath.com/decibels1.htm . 58 db is awfully quiet.
"yeah, *BUT*" applies.
first, "spelling counts" it is 'decibels', not decibles. regular
metric units -- a deci-bel ==> 1/10 of a 'bel' (which is a log10 scale)
3 decibels -- or "0.3 bel" roughly corresponds (actually 0.3020+ bel) to
a doubling of the actual power in the acoustic signal.
So, yes, the _energy_, or "power" in the noise from the shop vac is 256 times
higher than the Fein.
HOWEVER, the sensitivity of the human ear is _also_ more-or-less logarithmic,
with regard to the power of the audio signal it receives.
Thus the Shop Vac will "apparently sound" only about 8-10 times louder than
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.