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Re: comparing 20 portable digital recorders

Subject: Re: comparing 20 portable digital recorders
From: "Rob Danielson" danielson_audio
Date: Tue Nov 10, 2009 7:00 pm ((PST))
At 9:30 PM +0000 11/10/09, Robin wrote:
>
>Shotgun mics may or may not be appropriate for you. They do gain 
>isolation of source from environment, but that depends on usage. For 
>film work they are properly held angled towards the ground above the 
>speaker(s). Unless there's a lot of wind (or noisy snakes!) in the 
>grass, the only thing on axis is then the subjects you're trying to 
>capture. Even with a boom [shotgun mic], you won't be doing this 
>from too far away.

Right. Getting close is key with any mic in noisy settings. Here's a 
calculator one can use to compute the significant reduction in 
background sound levels with shorter mic to subject distances. 
http://www.sengpielaudio.com/calculator-distance.htm

The level of the background drone for a bird mic'd at distance of 15 
feet with an omni-drectional mic should be at least 12dB less than 
that for the bird mic'd at 80 feet with a "shotgun" mic.  This means 
that the level of the background drones would be around 400% louder 
with the shotgun mic if the sound level of the bird songs was matched 
in both recordings.

It seems like a strategy creating bird to mic distances in the ball 
park of 10-15 feet should produce very workable separation. To 
produce the same foreground/background separation with a shotgun mic, 
one needs to mic within 18 to 24 feet. This is why I like the odds of 
placing the H2's, leaving and letting the birds come to the mics. 
There's also more nuance in the recording with closer positioning.

Here a QuickTime movie comparison of three omni-directional mic to 
catbird distances in a rural setting:
http://tinyurl.com/yfrq2hs The ratio between the foreground birds and 
the background traffic would be considerably lower in urban settings 
so there would be more audible background in all of the examples. Rob 
D.


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