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Re: comb filtering and boundary mics

Subject: Re: comb filtering and boundary mics
From: "Dan Dugan" dandugan_1999
Date: Tue Jul 27, 2010 9:58 am ((PDT))
>>>> I suggest that boundary array experimenters set up their rigs
>>>> outdoors, listen to just one channel on both ears,
>>>
>>> ? Can you clarify this part?
>>
>> Listen to just the left or right mic with both ears, to put stereo
>> effects out of the picture.
>>
>> -Dan
>>
> Here's a blind comparison movie created from the results of a moving
> pink noise test that is hopefully very similar to what Dan suggested.
> The (3mb .zip) download link is at the bottom of the blog post here:
> http://tinyurl.com/2egg33s Play it with QuickTime or a
> QuickTime-compatible player on your computer.

Very nice, thank you, Rob.

I've posted a Spectrafoo sonogram of the MP3 at:

http://www.dandugan.com/downloads/Miscellany/20100726_BoundaryCombFiltering=
.png

and another with higher gain trying to show the highest frequencies better

http://www.dandugan.com/downloads/Miscellany/20100726_BoundaryCombFiltering=
_2.png

The most audible effects I hear are a descending tonal effect in the mid-ra=
nge and the directivity of the mics at high frequencies (HF comes up as pan=
 comes on axis). Both happen on all three mountings. I don't understand the=
 source of the mid-range effect.

Comb filtering effects at the top end that were my concern when I proposed =
the test are more subtle than I expected. I found it useful to high-pass th=
e playback way up like 5k-8K to eliminate the distractions of the lower eff=
ects.

-Dan








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