naturerecordists
[Top] [All Lists]

Re: Muriemike and falling snow

Subject: Re: Muriemike and falling snow
From: "Mike Rooke" picnet2
Date: Wed Dec 16, 2009 4:24 am ((PST))
Hi,
     Mics placed around a log spiral can be beam formed this I think is the=
 traditional application for beam forming (log) also for the linear array.=


In the context below I more refer to the effect of the boundary itself on t=
he mics - I experimented with a parallel boundary mic that utilizes log spi=
rals with the mic placed at the center.

The idea originally investigated by the Neumann paper I link to via the blo=
g entry. .It shows the effect of diffraction effects at the edge of a bound=
ary, rectangle, square, circle, triangle and the log spiral. The geometries=
 were investigated and they found the log spiral to give the least influenc=
e caused by diffraction effects in fact it boosted key frequencies by 6 dB.=
 The distance from the mic to the edge is always different thus pressure bu=
ild up leading to peaks or nulls in the response are avoided. Neumann went =
on to develop the concept further using computer analysis to come up with t=
he triangle boundary layer mic, the GFM132.

The first rig included an area to place the recorder:
http://www.urlme.net/blog/?p=3D1150

The second was investigating the boundary without a center structure - in t=
his regard the rice crispies box comment was related to using cardboard rat=
her than the plastic or acrylic plates. The second mic used corrugated plas=
tic and a tube between the mics.

http://www.urlme.net/blog/?p=3D1166

Perhaps the best examples there would be the "urban din" and papa walking p=
ast the rig.
Ive not had much time to get out down to the local river where I normally t=
est rigs.

For more processing Im working on a dipole mic:  Which is proving to be an =
interesting contraption considering the mics are next to each other

http://www.urlme.net/blog/?p=3D1175

The last mp3 player has a very crude test, imaging is so so and needs furth=
er work to EQ the capsules response. I was glad to see reference to the Ozo=
ne 4 mastering plugin which may help tremendously with that effort.

Kind Regards,
Mike.


--- In  "gmo_dunes2" <> wro=
te:
>
> Mike:
>
> Could you please explain what a "log spiral array" is? Is it an array of =
microphones with processing to do beamforming or two mikes, one on each sid=
e of a large conch shell? How do you make it out of a box of rice crispies =
(do you HAVE to eat those dry little bits first in order to make it work?)?
>
> Inquiring minds want to know!
>
> Thanks!
>
> -Greg
>
> --- In  "Mike Rooke" <yg@> wrote:
> >
> > Hi,
> >     I think the snow recording is in a very diffuse environment - i che=
cked the cross correlation and there wasnt much to conclude besides the dif=
fuseness :) - Previous recordings Ive heard had a decent center. Ive found =
a log spiral array to give the best center and also gives a boost to the cr=
ispyness. You could even make it from a box of rice crispies :)
> >
> > Using matrixing to adjust parallel boundary arrays is shifting the phas=
ing around which I think is as intended but it may require quite a processi=
ng chain, preeq & mic response balance, matrix, m/s eq, matrix / post eq & =
secret sauce. - Ideal setup is to ensure the mics are matched and placed so=
 the effects of phase are minimal, which means exactly at the same position=
 either side of the rig, thats also shaped exactly the same.
> >
> > I can assist you testing the mic Klas using my mad science if it helps.=
 Im enjoying the development and the small changes that are made. Muriemike=
 has a lot of potential.
> >
> > BR
> > Mike
> >
> >
>








<Prev in Thread] Current Thread [Next in Thread>
Admin

The University of NSW School of Computer and Engineering takes no responsibility for the contents of this archive. It is purely a compilation of material sent by many people to the naturerecordists mailing list. It has not been checked for accuracy nor its content verified in any way. If you wish to get material removed from the archive or have other queries about the archive e-mail Andrew Taylor at this address: andrewt@cse.unsw.EDU.AU