Software questions MiniMens

[William R. Brohinsky]

3dB is a factor of 2 for power. (note power is expressed in watts, 
joules or some such, and as such cannot be negative. The components of 
power, for instance, in electronics, voltage and current, are a 
different unit, and in fact 6dB is a doubling of voltage.)

It is nice to remember in here that dB is a ratio only, and 'absolute' 
dB values have an implied reference. Good usage states the reference, so 
dBm is 'referenced to 1mw (one milliwatt, 1/1000 Watt), and dbV is 
referenced to 1volt. Sound pressure levels have their references, and 
weightings (different curves which are applied to 'correct' readings to 
match the sensitivity of things like ears).

By the way, while most of the quoted numbers are right for sound power 
(a less vague term than 'loudness'), the total of 3+3+3+1.5=10.5, and 
that is an increase by a factor of  11.22; dB is log-base-10, so  a 
magnitude (factor of 10) is 10dB.

A handy reference(?):
1dB = x1.25
2dB = x1.58
3dB = x2
4dB = x2.51
5dB = x3.16
6dB = x3.98
7dB = x5
8dB = x6.3
9dB = x7.94
10dB =x10
11dB=12.5 (note, this is 1dB x 10, or 1dB +10dB: adding dB multiplies 
the factors like adding exponents!)
20dB=x100
30dB=x1000
(ie, decades of dB are powers of 10. Thus, 30dBm is 1dBW, because 1mw x 
1000 = 1 W)

The useful ones to remember are
1dB = x 1-1/4
3dB = x 2
5dB = x 3
7dB = x 5
10dB = x10
Y0dB = 10^Y

and, if you're familiar with logarithms, you probably have divined (or 
remember) that
dB=10(log(factor))
and
factor=(invlog(dB)/10)

With calculators (and all the OS's in use have scientific calculators 
built-in) it's not hard to deal with dB.

raybro

Robin Hufford wrote:

>Actually, I believe 3 Db is about a doubling of  "loudness".  3 is a
>doubling plus 3 more makes a quadrupling plus 3 more makes eightfold at
>9 Db.  Then 1.5 Db makes approximately tenfold or an order of magnitude.
>
>Regards, Robin Hufford
>
>Bernhard Stopper wrote:
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