> My goal is to enhance my kit for recording in windier
situation. I realise that a side effect of wind noise
reduction is frequency attenuation. Yet manufacturers say
little about this, likely because the effect is not
significant for ENG work, compared with the dramatic
improvements of reducing wind noise.
Robin,
Oh dear, just whe I was trying not to write like a geek, you
come up with one of my favourite subjects.
I can write a lot on windgags, but I won't here. My claim to
fame is having done quite a lot of experimenting before
Rycote happened, and invented a sock (The Brinisock) to go
over their first garden mesh blimps. This was also an
anti-rain sock which nobody has copied, but I was happy to
stop selling mine to the BBC Film Unit after 100 or so and
let Rycote make something similar.
Parameters:
1) Size. A small increase in windgag diameter gives a big increase in
tolerable windspeed. There are equations for this but worth ignoring -
just that the bigger of any radius of curvature the better, including
edges and the mount.
2) Cover: What any cover does is to provide a smooth
interface to the wind to reduce turbulence. You don't need a
cover fixed to the blimp cage provided it doesn't flap. The cover
material should stop zero frequency (air movement) and attenuate the
bass, acting as a high pass filter. You should be able to blow through
it with a bit of resistance. Listen through it to see what it absorbs.
3) HF Attenuation. Having taken care of the LF attenuation,
you want minimum HF attenuation. The principle cause of this
is the thickness of the layer or combined layers compared
with the highest frequency wavelength. 16KHz is 21 mm and
inversely pro rata. Perfection is thickness at 1/10 of the
wavelength (including diagonal angles), but false fur still
lets a lot of HF through and greatly reduces turbulence. The last
thing you want is HF boosting if you have quiet locations not far
above mic hiss.
4) Frequency response. An effective gag material will cause
reflections and a layer each side will create standing
waves. You won't notice these as much on-axis but to the
side they can be quite audible. You won't find any side
angle response curves of directional mics as they are often
very lumpy and get worse with a cylindrical windgag.
I'm experimenting with a large spherical windgag over two
gunmics but haven't worked out the mounting arrangement yet.
I'm hoping it will cope with high winds.
Almost forgot - try putting the windgag on the ground. It
often sounds OK and there's a lot less wind down there. If it dosn't
work at least you've tried it. :-)
David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
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