[Boatanchors] [ARC5] mike current

[Richard Knoppow]

----- Original Message ----- 
From: "mac" <w7qho at aol.com>
To: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
Cc: <milsurplus at mailman.qth.net>; "ARC-5 List" 
<arc5 at mailman.qth.net>; "Boat Anchors List" 
<boatanchors at mailman.qth.net>
Sent: Wednesday, September 07, 2011 7:17 PM
Subject: Re: [Boatanchors] [ARC5] mike current


> Richard,
>
> Bell System Technical Journal, that makes sense.  Seem to 
> be available  on line.
>
> Thanks.
>
> Dennis D.  W7QHO
> Glendale, CA

     I wrote too fast and didn't proof. I meant to indicate 
that it was available on-line. All issues. While most of the 
BSTJ is dedicated to subjects of interest to the phone 
company Bell Labs did a lot of fundamental research into 
sound transmission and recording in the mid-1920's on. 
According to an old friend, now SK, who was a Labs 
scientist, one of the main reasons for publishing the 
Journal was to sell ideas that were beyond exploitation by 
Ma Bell.
     It was a well respected journal but the "real" 
scientific journals had much more in the way of basic rather 
than applied research. Many BSTJ papers were also published 
in these journals. A list would be long. The BSTJ and the 
Bell Labs Record, a less technical periodical, are of 
particular interest for devices widely used in the telephone 
service such as carbon microphones and magnetic sound 
reproducers. Because such items were produced by the tens of 
millions for telephone service there was both the money and 
justfification for spending it for thorough research and 
development. Because they were often developed for 
completely in-house application the motivation for keeping 
certain knowledge proprietary did not exist, at least not to 
the extent it did where a commercial product for sale was 
involved. Thus the research papers found in the BSTJ and 
from Bell Labs people published elsewhere are likely to be 
pretty complete. But, they are limited because the interests 
of the phone company were limited in many ways.
     If you are interested in microphones and loudspeakers 
you might want to get a copy of: _Electroacoustics: The 
analysis of Transduction, and its Historical Background_ 
Fredrick V. Hunt, The American Instute of Physics for The 
Acoustical Society of America 1954, reprinted 1982. 
Currently in print.
     Transduction is simply the translation of energy in one 
form into another, such as electrical to mechanical and 
mechanical to acoustical, the transduction done by a 
loudspeaker or head phone, and the opposite as done by a 
microphone.
     About a third or more of the book is historical and 
covers related areas such as the history of the telegraph 
and telephone and the discovery of magnetism. Some of it is 
highly technical but much is plain language and very lucidly 
written. Its avaiable from Amazon and is not expensive. Hunt 
has perhaps the clearest exposition of mechanical and 
acoustical analogies, that is the presentation of mechanical 
and acoustical devices in terms of electrical circuits. This 
is important because the analysis of electrical circuits is 
exceptionally well developed so being able to calculate 
other types of energy carying devices in electrical terms is 
very powerful.  Those who would like a good understanding of 
things like resonances and damping in mechanical or 
acoustical devices will find this book very helpful.

     Its too hot in Los Angeles...


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com