52792

神经网络昆斯林的新闻组分类2006

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From: [e-mail] 
Subject: Re: What is Zero dB????
Date: Tue, 6 Apr 1993 17:25:32 GMT
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In article <[e-mail]>
      [e-mail] (John Thomson) writes:

 >Joseph Chiu ([e-mail]) wrote:
 >
 >: Thus, a deciBell (deci-, l., tenth of + Bell) is a fractional part of the
 >: original Bell.  For example, SouthWestern Bell is a deciBell.
 >
 >Out of what hat did you pull this one?  dB is a ratio not an RBOC!
 >
 >: And the measure of current, Amp, is actually named after both the AMP company
 >: and the Amphenol company.  Both companies revolutionized electronics by
 >: simulatenously realizing that the performance of connectors and sockets
 >: were affected by the amount of current running through the wires.
 >
 >Sorry.  The unit for current is the AMPERE which is the name of a french-man
 >named AMPERE who studied electrical current.  The term AMP is just an abbreviation
 >of it.  The company AMP came after the AMPERE unit was already in use.
 >
 >: The Ohmite company was the first to characterize resistances by numbers,
 >: thus our use of the Ohms...
 >
 >I don't know about this one, but it doesn't sound right.
 >
 >:
 >: Alexander Graham Bell, actually, is where Bell came from...
 >Well you got one thing right!
 >:

Actually, I think J. Chiu knows the score and is just being
silly. However, "decibel" is in fact 1/10th of a bel. He is
right on that one, but I don't know if it was accidental or not.

Strictly defined, a bel is the ratio of the log of two power levels,
and a decibel is 1/10th of a bel so you have 10X decibels for every bel,
hence bel=log(P2/P1) and decibel=10Xlog(P2/P1).

The bel, ohm, volt, farad, ampere, watt, hertz, henry, etc. are
all named for pioneers in the field. It's a traditional and fine
way to honor researchers who discover new knowledge in a new field.
Hertz was one of the most important of the early electronics explorers,
but had been left out in having a term or unit named after him
until recently, (1960's, prior to that what is now a hertz was a cps.)
All the other units were defined many decades earlier.


 


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