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From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Sat, 13 May 2000 09:28:52 +0300
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Steve

Gobble-de-gook, codswallop or BS it is, IMHO. There is NO way by adding sound to a
noisy environment can you reduce the sound level. If the before sound level is such
that comfort/health is compromised and you add sufficient white noise to mask it, then
the after sound level would be a good 10 dB higher, possibly sufficient to bust your
eardrums.

In any case, air flowing out through a non-resonant nozzle will produce what? White
noise! (OK, for air knives, there will also be some cyclic noise, as well, generated by
the ventilator blades, and you may have some minor resonances.)

What your guy may be thinking of is noise-cancelling, but this is also irrelevant here.
This consists of adding a cancelling variation of air pressure to those produced by the
noise source. It does not work well with white noise as it is impossible to predict, by
definition, when the next high or low pressure will take place. It is also very
positionally sensitive in three dimensions, depending on the frequency, spacing between
the primary and secondary sources, position of the pick-up microphone, etc.

Forget all this and buy those insulation panels.

Brian

"Stephen R. Gregory" wrote:

> Hi ya'll!!
>
> This post may be a little strange, but I'll ask anyway. We're getting ready
> to put a used Electrovert H-500 out on our floor. We currently have a old
> Hollis Poly-clean. When you look at the blowers on a Poly-Clean compared to
> the blowers on the H-500, the H-500's blowers look about twice as big...and
> the Hollis is kinda' loud...but people don't complain too much when it's
> running...I don't know about the H-500 though.
>
> The sound suppresion foam on the inside of the H-500 needs replacing, it's
> deteriorated quite a bit. But there's a person here that is suggesting that
> instead of replacing the foam, look into "white noise" generators. This
> person says that when they were in a machine shop environment, "white noise
> generators" were amazing as far as lowering the decible level of the machines.
>
> I have to plead ignorance on this subject. Do any of you have any knowledge
> about this? Or have any first hand experience with "white noise generators"?
>
> Myself, I think we should just replace the sound suppression foam, but this
> person swears that "white noise generators" is the way to go (but they can't
> tell me where I can find this stuff)...if that is true, where do I go to get
> these generators (speakers and certain frequency sources I assume)? Is there
> such equipment? I've searched the web, but can't find anybody that sells this
> stuff (makes me more confidant that I should just replace the sound
> suppresion foam).
>
> Is this just a bunch of gobble-dee-gook or what?
>
> -Steve Gregory-
>
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