Re: Directional Mic - using only aural tubes

"Canyonland" <[EMAIL PROTECTED]> wrote

> On my factory floor we use a [speaking tube] to speak to the office

> Our proplem is that as our machinery is
> getting louder, the office staff are finding it too noisy when
> listening on the tubes.
> 
> My question is-  How can I modify the tubes so as to eliminate
> background noise as much as possible and still allow the voice of the
> tube holder to come through to the office ?

Hmmm, like most problems I think this one has been solved.  Speaking
tubes were used for communications on ships (heck may still be) -
including engine room -> bridge.

IIRC [from old movies & newsreels] the tubes were 2-3" across
and flared at the ends.  The speaker put his mouth up against
the flared end to speak.

Google "speaking tube" for a whole lot of references, including
some pics.

If you need to block inside/outside air flow a rubber diaphragm
somewhere along the length of the tube will do the trick.

--
Nicholas O. Lindan, Cleveland, Ohio [EMAIL PROTECTED]
Consulting Engineer:  Electronics; Informatics; Photonics.