> But anyway, I have never been satisfied. Wind noise is always
> audible, even in small wind and when mics are close to the ground.
Magnus,
Windshield design is quite complex. If you place the best windshield
in turbulent air it will create noise from the energy in the
turbulence. There is often less turbulence low down - and in general
lower windspeeds as well - but behind an object like a tree or other
obstacle, the air can be quite turbulent.
Turbulent air has vortices - like smoke rings - which are fairly
stable and don't produce noise on their own. When a vortex meets a
fixed object, its enregy is released as LF noise.
The windshield itself must produce minimum turbulence by having as
rounded a shape as possible all over, not just it front of the mic.
Avoid all sharp corners or sharp curves. Make sure a stand or support
is not producing turbulence.
The outer cover should be a thin as possible to preserve high
frequencies. For the same reason there should be only one wind
barrier. This outer layer acts as a high pass filter, giving a bass
roll-off, including zero frequency. Test materials by trying to blow
through them - there should be some resistance to ait passing through.
False fur is fairly transparent to sound but it can affect the
frequency response, but helps to minimise secondary turbulence.
Using a foam gag inside a larger windshield does little to help
because, in there, the wind has already been converted to noise, and
it can spoil a frequency response which cost a lot of money.
With a mic with an extended LF response, it is worth using a bass
roll-off to avoid LF overloading. There is no point in recording
frequencies you don't use later. With digital recording, you can put
back LF without losing quality.
The other source of rumble is the windshield itself which is a matter
of design. It is important to avoid resonances in the shield and
mount.
If you want to record wind, that is one of the most difficult things
to record. We hear wind turbulence caused by our ears and head, but
good results can be had from wind in trees or blowing through a bush.
David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
|