Thanks all for the advice on wind noise filtering. I now have a
better idea of what to expect and what is not realistic to expect.
Bob
Sonoma, CA
On Dec 25, 2006, at 9:14 PM, Syd Curtis wrote:
>
> As Walter has pointed out concerning the use of various filters:
>
> > This won't stop the sound of the wind in the environment,
> > which you just have to live with.
>
> I'd like to add to that.
>
> I do most of my recording in subtropical rainforest (roughly half
> way up on
> the eastern side of the Australian continent). The rainforest has a
> closed
> canopy. As wind speed increases, the noise of the wind in the treetops
> makes recording useless well before there's enough wind movement at
> ground
> level to cause significant environmental noise. Furthermore, the
> birds that
> are my interest sing very little or not at all, if the wind is very
> strong -
> no point in singing if noise in the background is so loud your
> intended
> audience can't hear you.
>
> (Any air movement at all over, for example, a naked Rode NT4 mic,
> will cause
> cause problems but that's a different aspect of the situation).
>
> But what I sometimes finish up with, is a recording where the bird
> song is
> reasonably clear, but there's an annoying dull background roar from
> the wind
> blowing over the forest canopy. Sometimes I can minimise this wind
> roar in
> the field by getting into a position where I am aiming my mic down
> towards a
> gully; but sometimes I can't avoid pointing the mic upwards towards
> the
> distant canopy - with resultant maximum roar.
>
> Because low frequency sound attenuates much less with distance than
> high
> frequency sound, most of this wind roar is at a lower frequency
> than bird
> song, and any 'brick-wall' filter can be set to remove all sound
> below any
> desired frequency. Find the lowest frequency bird notes and
> experiment with
> the filter setting to find what seems best.
>
> Now that is good for my purposes of studying the detail of the bird
> song,
> but a recording with no sound below say 500Hz certainly doesn't sound
> natural. Vicki Powys, who posts to this list, and who is tape
> editor for
> the Australian Wildlife Sound Recording Group, gave me a tip on how to
> improve this.
>
> Find a section of the unfiltered recording where there is
> negligible noise,
> and copy a part with no bird song. By repeated copying, extend this
> until
> you have the same length as the recording you have filtered. Mix
> the two
> together.
>
> I haven't tried, but it seems to me that it would be feasible to
> copy any
> quiet recording you have from the same location, then filter out
> all sound
> above the frequency you fixed on to remove the low frequency noise,
> and mix
> the two. Not acceptable for scientific purposes, but OK for just
> getting
> the best possible result for pleasant listening?
>
> Syd
>
>
>
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