[GreenKeys] Telephone equipment factory question

[Chris Elmquist]

On Sunday (10/26/2008 at 10:43AM -0000), Alf Fisher wrote:
> Hi Greenkeyers,
>
> Has anyone ever heard of sound levels being measured in mm?
> Could this be millimetres or some other quantity?
>
> In America in the 1920's, a noisy factory was making telephone relays for 
> Western Union.
> They had 470 coil winding machines running and the sound level was recorded 
> as 0.85mm.
>
> Does anyone know how this would equate to the dB sound levels we use today?
>
> Regards,
> Alf Fisher
> G3WSD
> Bedfordshire
> UK

I'm no expert by any means...  but measuring sound level _is_ a
measurement of pressure.  The standard SI unit for sound pressure is
the Pascal and you can convert Pascals to height of mercury measured in
inches or mm.

Assuming your .85mm is a measure of mercury, that's equivalent to 113 Pa--
which on chart down this page on wikipedia,

http://en.wikipedia.org/wiki/Sound_pressure_level

says is above the threshold of pain and somewhere in the range of loudness
of a jet at 100m (6 to 200 Pa, or 110 to 140 dB).

I'm guessing it was pretty loud in the factory :-)

Chris
 
-- 
Chris Elmquist
mailto:chrise at pobox.com