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Re: How high do you put your mic?

Subject: Re: How high do you put your mic?
From: "Rob Danielson" danielson_audio
Date: Wed Aug 5, 2009 5:49 am ((PDT))
At 4:40 PM -0500 8/4/09, Curt Olson wrote:
>Rob Danielson wrote:
>
>  > Curt, are you using that height with your array with the 2nd
>>  boundary on the bottom?
>
>Yea, but let's not go into that here. ; )

Could be a pretty big factor though as the hard boundaries that are 
fairly parallel to the ground in that array reflect more "above the 
horizon" sound. I would expect it to respond to height changes very 
differently from free air rigs and and arrays that have vertical 
boundaries like SASS and the other boundary arrays you developed.

>  > Over all types of surfaces?
>
>To my ear, both near and distant sounds seem to stand out somewhat
>more distinctly in the small zone I referred to as the "sweet spot." I
>suspect one reason might be that, as Greg noted, certain types of
>background noise such as traffic noise, might be slightly reduced. If
>that's the case, then I would further suspect that it might have
>something to do with the happy accident of desirable phase
>cancellation that might occur at certain distances above the surface,
>and to which certain microphones or types of arrays respond in a way
>that some of us find to be pleasant.

If there is advantageous phase cancellation or other ways the low 
frequencies become attenuated, you should be able to detect the 
nature of these changes, dynamically, with some fully-enclosed 
headphones and hand-holding the rig as you lower it from head-height 
to the ground. Would be instructive to do this over different ground 
types such as short grass, large smooth slabs, patches of bare 
ground, tall grass, brushy undergrowth, etc.

When the ground is absorbing sound waves, I think it is accepted 
theory that lowest frequency sound sources are less affected than the 
higher frequencies that are often more helpful in creating spatial 
clarity.  The ratio of sound waves coming directly from distant 
sources compared to those influenced by the ground is also smaller 
with near to ground placement. However, considering the larger scale, 
we're only discussing a ~4 change in height with subject to mic 
distances being much larger. If you and Greg are producing recordings 
where any technique is improving spatial clarity, its definitely 
worth looking at the specifics and trying to figure out how its 
happening.  We might need some field tests to get the the bottom of 
it. Rob D.

>Curt Olson


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