> JND is measured in dB, that's all.

True enough, which is back to my original point that if your attenuation
nob is notched according to ratio reductions in power, then a linear
fadeout in terms of clicks (notches) per second should be reasonable,
i.e., sound right. Which means it's not all that complicated.

> Not necessarily.  It's just that JND has to specify the conditions.  You
> can blow those conditions right out of the water with a strategic small

Yeah, no argument there. Standard conditions are documented tho... 1kHz
tone blah blah blah. 

> change in environment.  In any case, decibels just simply are never
> *defined* in terms of JND, JND is measured in dB.  There are lot's of
> books to look at for confirmation.

Yeah, I was originally suggesting that the definition of dB relied on
JND. However, my amendment was that psychophysical research had discovered
the ratio to be meaningful in terms of the perceptual apparatus. I.e., JND
comes out to be pretty close to 1 dB (but yeah, under certain conditions). 

> > > but you could just as easily say that Joe who
> > > makes $20k/year earns 6dB$ less than Sue who makes $40k/year.  
> > 
> > I think I disagree. First, I think it has to refer to power.  
> 
> Nope.  Can refer to whatever you want.  Power is the most common use,
> however.  

I still think such usage is a distortion; still meaningful, maybe, but
really ouside of the scope of the formal definition.  In other words, by
definition, the number of bels is defined as the common logarithm of the
ratio of two powers. Since you have references, see if the definition
specifies powers.

> > Um... Remember that power is proportional to (voltage)^2, so using 6dB
> > would be appropriate if you were talking about voltage instead of power --
> > a doubling of voltage is a 6dB increase or a power ratio of 4. 
> 
> You have a lot of the right pieces, but you're trying to force a voltage
> situation into power.  I was. :)

I think that's all the more reason that the definition relies on power. If
you're talking about the metric of change to be voltage, you need to say
so, otherwise it's not clear whether you double the stuff with 3 or with 6
dB. So what's the right relationship to use for your salary example?


> Yeah, but you're used to inverse squared power losses in location bat
> recording.  Audio inside electric boxes should make you think 20log
> ratios, and digital should make you think dBFS as one of the major
> idioms. Analog signals should make you think voltage as dBV (0dB = 1V
> RMS into 600 ohms), dBu(pure voltage, ref level 1V, IIRC), or the most
> popular, dBm (*voltage* referenced to 1mW of power through 600 ohms.)

Well, any person will likely be versed with a subset of the idioms. I
*should* have been able to think in terms of bits for the digital sampling
environment for .wav files, but you had to remind me. As mentioned, it's
not obvious what to do with dB$. Or I'm still missing something (Highly
likely). 

> Correctly!  I'll bring a book the next time we get together.  It's a
> little bit confusing until you sort out all the different dB scales.

They're gonna send us to a different table. Or a different bar. 

Andy