On Thu, 16 Feb 1995, Sodorff Lori wrote:
> I don't mean to say or to leave the image that it will be a wall!
> more like and accoustical(sp) fence in order to direct the sound back
> into the park rather than into the surrounding neighbor hoods. Not to
> mention that as third and hayes streets are becomeing more and more
> heavily travels perhaps a solution to the noise and protection of
> children should be considered. >
>
Just off the top of my head (and from small experience with sound) I
don't think there could be an economical alternative to a wall of some
kind (if you wanted to 'contain' sound in the park.) Here's why: a fence
without considerable mass would do little to absorb or reflect much of
the sound energy. Most of it, especially the lower frequencies, just
truck on through thin walls. This is one reason that you only hear the
bass coming from cars in which the occupants are listening to the stereo
too loud: it's not that they have an extra fondness for bass, it's just
that while the higher frequencies are absorbed by the car, the lows
pay no attention to the car and just keep on going (to the sidewalk,
through the wall of your bedroom, etc.) If you look at noise fences
around freeways you will see that they are usually made of some kind of
cement block. This provides enough mass to prevent sound waves from
traveling through the fence. I presume the waves are also deflected
upwards. These fences are usually quite tall, c. 10 feet, I think.
Another alternative to absorbtion/deflection for noise abatement is
diffusion. I am thinking of the ceiling in the UI Admin Auditorium:
there are some very specifically engineered baffles up there to prevent
unwanted echoes. Some sort of fence could conceivably be made
incorporating acoustic baffles but--still just writing off the top of my
head--I think such a fence would be quite expensive.
Here is one idea that MAY be feasible (though I am just throwing it in
the ring without much hope: I still think there must be a better solution
than fences or stupid ordinances.) It involves a material that we
already use at the Fair, it provides excellent sonic absorbtivity, it is
cheap and it is temporary: straw bales. Straw bale walls placed
strategically could block a LOT of noise from the surrounding
neighborhood. Before you laugh too much, you should know (if you don't
already) that straw bale construction is becoming very popular in
alternative building circles. I know that an
entire--temporary--children's castle was constructed for an event in
Oregon. I think the work was done by a straw bale building association.
I guess the kids played in and around the castle for a few days, then it
was taken down. Seems that if a castle can be safely erected then a few
walls around the park should not be too much of a problem. Kris Seiss
has done a workshop on bale building, he may be able to provide a few
answers.
Just some thoughts...