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> In an earlier note I presented the definition of a Just Noticeable Difference.
> KK1L, Ron, notes that, while my definition is OK, the fact is that 1 dB is a
> jnd,
> and he is correct.
> I checked it out in S. S. Stevens's old Handbook of Experimental Psychology,
> and,
> although a single person's jnd varies with initial loudness level and with
> frequency, along with who is doing the perceiving, data from Reisz in 1928
> determined that the averagejnd for a 30 dB above absolute threshold, 1000 Hz
> tone, was 1 dB.
Here is how Ron put it:
> 1dB just perceptable
> 3dB doubling of power
> 6dB sorta, kinda and S-unit...whatever that is today.
>
Jan, KX2A
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Subject: Re: [Fwd: Re: [TowerTalk] C-3 & TH7 comparison - a revision]
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Date: Thu, 30 Apr 1998 16:01:29 -0400
From: Ronald D Rossi <rrossi@btv.ibm.com>
>>>Jan Ladd Ditzian said:
>
>
> K7LXC wrote:
>
> > In a message dated 98-04-29 21:46:46 EDT, you write:
> >
> > << As to 2 db, I was taught in the old days that a 3db *difference* was the
> > smallest difference discernible by the human ear. That came from some
> > ne'er-do-well outfit called Bell Labs. >>
> >
> > Actually that's the definition of 1 dB - the smallest difference
> > discernible by the human ear.
> >
> > Cheers, Steve K7LXC
> >
>
> Steve,
>
> I think that you are incorrect in saying that 1 dB is the smallest difference
> discernible by the human ear. ...
This is the origin of the unit.
> ...The "just noticeable difference," or "jnd"
> defines the smallest difference discernible. The dB is an engineering unit
> that is the log of the ratio of two intensities.
Yep.
> I think that 3 dB turns out
> to be close to the jnd,
Nope. It's three just discernable units.
> but even this number varies throughout the range of
> loudness. The jnd is not an exact number, varying with people, situation,
> time, and a million other variables.
Yep.
>
> The jnd concept was first propounded by Fechner, around 1860, whose original
> attempt to relate human perception directly to physics has not withstood the
> test of time, but who propounded some very useful ideas. Some theories of
> perception, such as signal detection theory, dispense with the concept of the
> jnd.
Could be.
1dB just perceptable
3dB doubling of power
6dB sorta, kinda and S-unit...whatever that is today.
--
73 de KK1L...ron (rrossi@btv.ibm.com) <><
QTH: Swanton, Vermont
My page: http://www.together.net/~larossi/kk1l.html
My wife's page: http://www.together.net/~larossi
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