In article , Arny Krueger
wrote:

"Jim Lesurf" wrote in message
...
[snip]

http://www.shure.com/pdf/specsheets/...dmics/sm57.pdf page 2.

says:

"Sensitivity (at 1,000 Hz)

"Open Circuit Voltage: -54.5 dBV/Pa* (1.9 mV)

"*(1 Pa = 94 dB SPL)

Seems pretty clear and usable, as far as it goes right?

Yes. Much more useful to quote dBV/Pa as this gives a better idea of the
reference level as a transducer sensitivity.

Note that 0 dB is 0.02 mPa or 2 1/100ths of a milliPascal. Milli is
worth 60 dB, 1/100 is worth 40 dB, and 2 is worth 6 dB. Add it all up
and you have a 94 dB difference. So, the *books* may lie, but they all
tell the same lie. In this case its a generally-understood and accepted
convention so its no lie at all!

;-)

I get the impression that this is an area where the books may give
differing explanations which end up much the same, The reason being they
are all starting from the same definition, but some of the book-authors may
not fully understand it. If so, no suprise. I've encountered the same sort
of 'diversity' many times in books on EM, and IT. :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html