Peter
I agree that in the limited form of earmuffs, this is a possibility, because the
three-dimensional aspect is negligible, with respect to the wavelength of an audible
sound. But who the heck wants to wear earmuffs because a machine is badly insulated? I
wear earmuffs while using a strimmer in the garden and, after a couple of hours, I'm
really glad to take them off. When I wrote what I did, I was thinking of cancellation
throughout the workshop, which is, of course, impossible, rather than in the locality
of someone's lug-'oles.
Brian.
peter blokhuis wrote:
> I agree that adding white noise to the room is
> useless.
>
> In recent years, noise cancellation technology has
> made great progress, and I believe the airline
> industry uses active noise-cancelling 'earmuffs' now
> for the ground crews.
>
> However, the foam panels would be cheaper.
>
> --- Brian Ellis <[log in to unmask]> wrote:
> > 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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