Ignoramus13187 wrote:
On Fri, 21 Jan 2005 16:43:55 GMT, Jerry Martes wrote:


I read most of your RCM posts, and consider you to be a bright guy
with an interest in learning. I respect that.


Thanks.


I dont offer any advice so that it might diminish your plans. I do
suspect that the noise from an air cooled diesel generator will be
so extreme that there will be no way to quiet it to a level you will
be satisfied with. I'm considering that this sound absorbing is
done with a limited budget.


I have a sound level meter. The noise level from an un-enclosed
generator running in the open, at 10 feet, is 85 dB. I believe that it
is not so bad.


I think you have already considered the wide bandwidth of the noise
spectrum produced by the generator. The highs are something you can absorb
in alot of affordable materials. The lows are going to be real difficult
to diminish to a level you'll accept (I think).


This is an excellent point. The question is, from the standpoint of
not ****ing off neighbors too much, is 70 db of 125 Hz noise just as
annoying as 70db of 1000 Hz noise. I think that the answer is that
lower frequencies might be less annoying.



Remember, 5DB and even 10 DB wont hardly make any difference when the
level is so high to begin with. I assume you know about "3 DB" as being
the least amount of power level change thats agreed to have been adjusted.
And, less noise is still too much noise when the noise is so great at the
source.


Well, if I quiet it down from 85 unshielded to say 75 or even (maybe I
am dreaming) 70 db, that would be a very big improvement.

I know that I generally do not mind people running a lawnmower in
their yard, and those would produce noise comparable to my unshielded
generator. Google for lawnmower decibel, the most common number cited
is 90 dB for a lawnmower. My unshielded genset is 85. If my generator
produces even 80 decibel shielded, I would be basically fine.

I used to have an awful, disgusting 3600 RPM diesel generator that was
much, much noisier than my current Onan. Fortunately, I sold that POS
and the buyer is apparently satisfied (he left me good feedback).

So, perhaps you are thinking about such very noisy units, but my Onan
is a bit better.



The quieter it gets, the more your ears adjust and seem to hear better.
I think Alexander Graham Bell had that figured out 'way back when'.
I am not qualified to calculate the DB level you'll be trying to acheive.
I suspect you are better qualified in than calculation department than I am.
I do have some experience with trying to reduce noise levels from noisy
machinery and generators. It seems that the the quieter you get it, the
more 'quietness' you want. I wouldnt be surprised to learn that you will
want to diminish the noise level by 50DB or more when that generator is
producing power.


This is an excellent point, yes.


All that said, my advice would be to not spend alot of money on materials
till you are convinced you will ever achieve your acceptable goal within
your budget.


Thanks Jerry. The lead purchase was kind of a big leap for me. A big
(relatively) expense that is a real gamble. The reason for accepting
this gamble is that lead is the best material, and also that other
than this, there are no unknowns. The generator runs, and does so
quite well.

If I fail, I can always sell this lead on ebay for at least a fraction
of my original price.

i

But the buyer better be able to pick it up himself. G

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"