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Re: Noise Pollution (was Digest Number 506)

Subject: Re: Noise Pollution (was Digest Number 506)
From: Lang Elliott <>
Date: Mon, 11 Feb 2002 08:43:31 -0500
Yes, I made a special "wind box" for my SASS unit. It is cubical in shape
and measures about 20" on each side. The base is a piece of plywood with a
tripod ball-head mounted in the center to receive the SASS setup. This
plywood base is covered with acoustical foam.

The four "sides" and "top" are wooden frames (each made from four 1/2" X
3/4" pieces of wood joined at the corners with metal "L" braces available at
hardware stores) with appropriate fabric stretched over the inside of each
frame and stapled in place. The sides and top frames are joined using velcro
placed along the appropriate edges. There is also velcro on the plywood
base. Once I've covered the SASS with the wind box, I use two bungee cords
to hold the box securely to the base. Each of these two cords pass from one
edge of the base over the top of the box and then down to the other side of
the base.

In addition to the stretch fabric on the inside of each frame, which I found
at JoAnn's Fabric, the outside of each frame is covered with black "air
conditioning" or "heater" filters that I found at a hardware store. These
filters are very porous and they're about 1/2" thick. They further reduce
the effect of wind and also act as an absorber if it starts to sprinkle.

I carry a number of extra "filters" for recording in rainstorms. When a
storm is blowing in, I put the wind box together as usual, then I pile a
bunch of the filters on top the box, giving me 6" or more of absorbant
material on top to receive rain. When rain hits the filters, it makes very
little noise, and this is desirable. I only begin to hear "splashing noises"
when the filters on top begin to get saturated with water. When that
happens, I run over to the setup, pick up the the pile of filters, shake
them vigorously, and then place them back on top the box. Later in the
studio I edit out that portion, which lasts only a few seconds. I may have
to repeat this "shake out" procedure several times during a storm.

This technique works really well and has few drawbacks. One drawback for the
wind box is that it is designed to sit on the ground, or on some other
stable base. Thus the "acoustics" are somewhat changed in comparison to
placing the SASS on a tripod, well off the ground. Nonetheless, the result
sounds very good. Another drawback when recording in the rain is that the
filters on top will interfere with sound pickup from the top as they become
saturated with water. But this is a minor problem because the SASS still
receives good sound from all four sides.

I really believe in the "wind box" concept. It allows for recording in high
winds without the need for a steep low cut filter, and without using thick,
hairy fabrics that really cut down the high end. The key factor in
constructing a wind box is to make it big enough to create a large interior
space around the mike setup, which will help dampen sudden changes in
pressure due to the wind. The bigger the space, the better.

For rainstorm recording, a primary concern is that you record in a way that
you avoid raindrops hitting the mike setup itself, creating thumping or
splatting sounds that are annoying. Another thing to avoid is the use of an
overhead cover (such as an umbrella or a tent), where the rain likewise
produces loud splats quite different from the sound of rain hitting objects
in the natural surroundings.

Lang

> Back some time ago Lang Elliot suggested using a foam material as a rain
> shield. The soft spongy material will absorb the sound of the raindrops and
> keep them off the parabola. The foam could be that which is used for
> evaporative cooling pads. It is an open cell material similar to that used
> in household sponges. The support of the material would be determined buy
> the recordists resourcefulness and particular situation. Draping it over an
> umbrella could work.
> 
> Eventually you might need to shake the water out of the material.
> 
> Now I have never used this method but feel confident that it could work.
> 
> My best rain recording is of Wood Ducks at the Rio Grande Nature Center. It
> was made while standing under a concrete overhang. Concrete seems to do a
> good job of dampening the sound of raindrops. This resulted in a very
> natural and pleasing rain sound.
> 
> Jim Morgan
> 
> 
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