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 tha=
t
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 caus=
e
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 win=
d
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 wit=
h
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
|