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Low-Cut Filtering in the Field (was at3032 LF "growl"

Subject: Low-Cut Filtering in the Field (was at3032 LF "growl"
From: "Rob Danielson" danielson_audio
Date: Sun Mar 2, 2008 11:34 pm ((PST))
At 2:20 AM +0000 3/3/08, Chris Davidson wrote:

>Hi Rob,
>I use the AT3032's in my headrig. I recorded this file,
>Frogs&GreatHornedOwl.mp3  http://cdavidsoniv.googlepages.com/home
>with the mic set to "roll off" (too much aviation noise) then into the
>722. Am I "growling"? I would appreciate you having a listen, thanks
>very much. Chris

Hi Chris--
Owls in the plural!  Would be interesting to see how you have the 
3032's body-mounted.

The owls and coyotes are going strong here in SW Wisconsin. The 
robins have been kicking off the dawn chorus for about 10 days. The 
frogs will start later this month. I heard a very anxious goose 
flying North last night and possibly some ducks tonight.

Are you asking should one use the low Hz cut filter in the field when 
there are loud, low frequency sounds? My short answer is, "No, unless 
the bass content is very, very loud, continuous and constituting 
almost all of the amplitude."

For example, I might use a low-cut filter when the low frequencies 
are so dominant they are forcing me to lower my mic pre gain way-down 
AND, after the low cut filter is on, I can hear higher frequency 
sounds with more clarity, AND I can get more, needed headroom. This 
can happen close to heavy equipment, helicopters-- mostly unnatural 
sources.  A natural situation might be loud steady, rolling thunder 
in order to get less rumble vs "air." I used the low cut filter one 
time when I was interviewing a bee tender and bees were covering the 
mics.

I feel the key factor is the lowest frequencies have to be creating a 
very significant percentage of the whole bandwidth in order for 
filtering in the field to do anything we can't do in post. The lowest 
octaves form the fundamental tones and without them, some recordings 
can quickly turn shrill and fatiguing. In post, I use parametric 
filtering to improve tonal balance and only "High Pass" or "Roll-Off" 
filtering on natural subjects under 30Hz. For "space," field 
recordings rely on spectrum balance more so than any other type of 
recording I know.  I also reason that since most animals hear and 
respond to the full frequency spectrum, the recordings I take home 
should include them.

I'm sure there are some exceptions I've not encountered. What 
advantage(s) have you experienced through attenuating frequencies in 
the field? Rob D.


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