They are vented too, of course, otherwise you couldn't bring them into an
airplane luggage compartment, but there is a delay before the pressure
inside is the same as outside, which is much longer than any sound waveleng=
th.
Klas.
At 05:22 2005-02-24, you wrote:
>From: Klas Strandberg <>
>
> >
> > Sorry, I'm sending the wrong postings to the wrong people here.
> >
> > An omni is a closed cylindrical can with a membrane as one of it's side=
s.
> > The pressure inside of it tends to be constant, and tend to keep the
> > membrane still, not so much affected by wind. (Or movement - handling
> > noise). The membrane moves because the pressure inside the can is compa=
red
> > to the pressure outside of it.
> >
> > A directional mic is a tube, with a membrane as the only one side. Both
> > sides of the membrane will get affected by wind, and there is no "const=
ant
> > pressure" tending to hold the membrane still.
> > Therefore a directional mic need a much better wind protection than an=
> omni
> > and is also more sensitive to handling noise.
> >
> > Imagine a tin-can where you have removed one side and replaced it with =
a
> > piece of balloon-rubber. Imagine you blow on the rubber. It will not go=
so
> > much inwards, as the pressure inside the can will hold it where it is.
> > Imagine you move it. The same thing will happen. The membrane will not=
> move
> > much.
> >
> > Now imagine that you take a tube and place the same rubber over it and =
try
> > the same experiments.
>
>If you do so, put the closed one out in a snowbank, then after a while
>observe the rubber, now bring it in and set it next to the fire, observe
>the rubber again. Did you notice the change in this closed system? What
>would happen to a mic capsule that behaved like this?
>
>Omnis are not closed cans, they are vented too. Just not the same kind
>of venting as directional.
>
> > If both have excellent suspension and wind protection, you will not fin=
d
> > much difference.
>
>And if they don't have excellent suspension and wind protection then you
>won't be able to do much nature recording. Or at least be severely
>limited as to when you can record.
>
>Walt
>
>
>
>
>
>"Microphones are not ears,
>Loudspeakers are not birds,
>A listening room is not nature."
>Klas Strandberg
>Yahoo! Groups Links
>
>
>
>
Telinga Microphones, Botarbo,
S-748 96 Tobo, Sweden.
Phone & fax int + 295 310 01
email:
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