Re: More cable talk

Brian Running <brunning@xxxxxxxxxxxxxxxxx> writes:

It's an important distinction that the folks stumbling trying to
(wrongly) correct people in this thread aren't absorbing just yet.

Is all this chest-beating and extremely condescending put-downs
necessary, Todd? I'd always thought of you as the most even-keeled,
level-headed poster here.

The chest beating seems necessary because several posters seem lured
into "correcting" things someone supposedly said wrong about dB's and
they in fact were incorrect. Gerry started, and has recognized he
goofed. Then you chimed in on certain things and still seem to think
you're right about it, which doesn't seem like you either.

And by the way, I'd fully expect you to flagellate the equine in a
similar manner if I stumbled into a legal thread swinging my dick
attempting to wrongly tell you what's what about, say, the origin
of various aspects of tort law.

So, is that what this is all about? I'm sorry, I had no idea that
you had an advanced degree in the history of technology, I thought
you had an undergrad degree in electrical engineering.

See, now you're just being an ass. What this is about is:

Todd> dB alone are not units of sound intensity.
Brian> Yes, they are. That's what they were originally for,
Todd> [clarifies with "Bullshit!"]

Just entertain the possibility that EE's who have worked in telecom
and specialized in analog signal processing in their coursework tend
to know a few things about dB's, dBm, dB(SPL), and various flavors
through daily use of the units for a few years in the past.

But since you're an expert in the history of technology,

Ah, inductive reasoning. Worked for Boon in Animal House I suppose.

I'll unquestioningly defer to you in that area from now on. But
just so this discussion is complete, I'll point out that you did not
provide an answer to the question of what Bels were originally
developed for. You asked me to provide some citation of support,
why should I accept your position without your doing the same?

The quote you recruited for your citation said it for me,
actually. Bell labs invented the Bel and decibel to quantify audio
power losses in telephone lines. Measurement of sound pressure levels
or "sound intensity" wasn't an application until later.

If I'm wrong, I'm wrong, but here's what I learned (long ago, not in
a current Wikipedia search, by the way) about the history of the
origin of the unit. The reason that it's a log scale is because it
was adapting to the extreme range of sensitivity of the human ear.
Using a log scale for the measurement of anything is usually
(always?) to make the numbers manageable because they're being used
to describe an observable phenomenon that spans a range of orders of
magnitude.

Yes, many sensory perceptions happen to behave logarithmically.

In the case of the Bel, the range was the sensitivity of the human
ear.

Wherever you learned this tidbit seems to contradict the vast majority
of other accounts. It's pretty widely reported that dB's use in
telephone line power loss (relative measurement, dimensionless, a
power ratio) was the invention point, and only later was adapted for
absolute sound pressure level measurements (db(SPL)).

If it were not, then why would a log scale be used? If it were
simply a ratio, then why was it found convenient to use the log of
the ratio, and not just simply use the ratio? If it was done that
way in order to make the numbers manageable, then what other range
was being used, other than the sensitivity of human hearing? If it
were simply voltages (or any other measurable phenomenon), why use a
log scale? Do you ever, in practical use, see voltages referred to
in more than just a few dBs? Ever see them in amounts of greater
than 120 dB, for instance?

And please, can you answer these questions without all the
chest-beating? It just doesn't seem like you, Todd.

Likewise, it doesn't seem like you to try to be so dogged in holding
to an incorrect belief, or interjecting and muddying a technical
discussion that was on its way to clarity.

To summarize, the dB, strictly, is not a unit of anything until a
reference is explictly stated or implied. And it was not invented as
a measure of sound intensity. That's really all.

If your (new for this volley) point is that its invention and use of
logs was influenced by the logarithmic nature of the human auditory
organ, I'd agree.

--
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.

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