boundary layer microphones have a slightly different set of rules.=A0this i=
ncludes the crown sass/=A0there was a very good article on the crown websit=
e many years ago, but briefly stated, the longest wavelength suppported by =
a boundary plate is six times the longest dimension of the plate. and at th=
is transition frequency, the omni mic mounted on the boundary gets a more a=
nd more omnidirection directivity pattern=A0 ( i think roughly 6 db/octave)
=A0
the net result is the noise gain of the microphone is independent of freque=
ncy, though the directivity pattern and front gain, rises till it reaches c=
ut off frequency and then stays flat.
=A0
one array i had built myself consisted of two six inch square acrylic plate=
s hinged together. each plate contained five six mm omni capsules glued flu=
sh to the surface in an irregular cross, the capsules were paralleled. this=
gave me a microphone with surprising directivity and gain, and the two hin=
ged plates gave me a stereo pair with adjustable angle between the micropho=
nes
=A0
i got some nice results with both nature recordings and music with this arr=
ay about 20 years ago.
=A0
umashankar
=A0
=A0
i have published my poems. you can read (or buy) at http://stores.lulu.com/=
umashankar
From: Avocet <>
>To:
>Sent: Tuesday, August 30, 2011 6:20 PM
>Subject: Re: [Nature Recordists] Lightweight array suggestions
>
>> I would like to make an array that is as light & transportable as
>> possible, yet won't be easily damaged.
>
>Marc,
>
>There is a golden rule with most arrays if you are interested in
>medium to low frequencies as heard in forests, and that is the size of
>any baffle or boundary should be comparable to the wavelength. At
>500Hz the wavelength is 680mm. (27")
>
>An exception to this rule is with an M-S mic or a double cardioid pair
>which will give you a good stereo image with a wide frequency response
>and - importantly - is easy to carry and deploy and shield from wind,
>rain and insects with standard windgags.
>
>David
>
>David Brinicombe
>North Devon, UK
>Cogito cogito ergo cogito sum - Ambrose Bierce
>
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