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Author Topic: Generator Db level  (Read 16233 times)
steve5B
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« on: February 26, 2009, 09:27:24 AM »


   Hey guys!

   Stopped by the local feed store where I buy my horse feed and they have there own labled Diesel generators.

   These are 8000watt and have certified 70Db.   What is the normal sound level?  For the price I'm going to pick

  up one for a back up this afternoon.

   
  Steve  5B........
 
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cody
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« Reply #1 on: February 26, 2009, 09:34:29 AM »

One thing that bears mentioning is that all genrators are loud, then you can concider how to quiet them down, most build quiet boxes and bring the sound levels down conciderably, what is the RPM on it, my honda is rated at 49 to 58DB, 70DB is very loud and would bring the wrath of every popup, 5th wheel, or travel trailer down with a vengencewithin a half mile but with some work and thought, the sound levels can probably be brought down to reasonable levels.  Generally campgrounds kinda cringe at anything over 60 to 62 DB
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Len Silva
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« Reply #2 on: February 26, 2009, 09:41:40 AM »

Keep in mind that db ratings are logarithmic.  An increase of 3 db is twice as loud.  70db is 10 times louder than 60 db.  There is a good explanation here:  http://www.newton.dep.anl.gov/askasci/eng99/eng99325.htm
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« Reply #3 on: February 26, 2009, 09:46:27 AM »

One to keep in mind is how many feet from the generator the DB reading was taken from most around the 20 ft range setting on top of a 70 DB is going to be a little loud  my generator is 23 at 20 ft   good luck
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buddydawg
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« Reply #4 on: February 26, 2009, 11:16:31 AM »

 3 dB = twice as much power, noticeably louder
 6 dB = 4 times as much power, significantly louder
 6 dB = twice the amplitude
 9 dB = 8 times the power, nearly twice as loud
10 dB = 10 times the power, twice as loud

Decibels provide a relative measure of sound intensity. The unit is based on powers of 10 to give a manageable range of numbers to encompass the wide range of the human hearing response, from the standard threshold of hearing at 1000 Hz to the threshold of pain at some ten trillion times that intensity.

The rule of thumb for loudness: it takes about 10 times the intensity to sound twice as loud.
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steve5B
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« Reply #5 on: February 26, 2009, 11:31:38 AM »



     Thanks guys,


    Some good info to say the least!


    Lin,

    Real good article to read, thanks.


     Steve 5B.....
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WEC4104
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« Reply #6 on: February 26, 2009, 12:03:06 PM »

To expand on Luvrbus' comments, you do need to pay close attention to the way a manufacturer quotes their sound levels, especially the distance.

I have seen Onan quote their specs based on a distance of 10 feet.
I have seen Honda quote their specs based on a distance of 23 feet.
The National Park Service set their noise level restrictions based on a distance of 50 feet.

It makes it tough to compare apples to apples. To help with the conversion, the following website has a sound level conversion tool:   http://www.mcsquared.com/dbframe.htm
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Sean
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« Reply #7 on: February 26, 2009, 02:05:42 PM »

... certified 70Db.   What is the normal sound level?  ...


Just saying "70 dB" without providing the filtering scale, measurement distance, and generator load at measurement makes it hard to know what they are talking about.

I'm going to guess this is the A scale, so they meant 70 dB(A) (probably the most common scale for these sorts of measurements).  But you really want to find out if this is a no-load, half-load, or full-load measurement, and what the distance was.

FWIW, the NPS limit is 60 dB(A) at 50 feet.  Here's a site that discusses measurements for two of the more popular "quiet" sets:
http://www.klenger.net/RV_General/Electrical_Generator_Noise/index.html

And here is a site that discusses acoustical sound levels and explains how deciBels work:
http://www.phys.unsw.edu.au/jw/dB.html

Really high-quality genny installations can achieve 60 dB(A) at 20 feet or less -- you can have a normal conversation right next to it.

Of more concern to me when buying a cheap no-name unit is whether it is a 3600rpm or 1800rpm unit.  I would stay away from the former.

-Sean
http://OurOdyssey.BlogSpot.com
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TomC
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« Reply #8 on: February 26, 2009, 03:25:16 PM »

My rule of thumb is- there is no such thing as a too quiet generator.  Also-you'll never get a complaint about a quiet generator either.  Good Luck, TomC
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« Reply #9 on: February 26, 2009, 06:08:02 PM »

Sean,

I have to disagree about the RPM thing. I've read this over and over on the board but have never seen any proof of this.

My own experience going from an air cooled Onan to a liquid cooled Honda is that the Honda is probably 1/4 as noisy and far smoother.

We're comparing apples to oranges because there are so many variables and with rpm comparisons we're getting into frequencies. Some people are sensitive to high and some to low. After many years in airplanes I can no longer hear very high frequencies so they bother me less.

Higher rpms also usually mean less sensed vibration.

In short, it all depends!
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WEC4104
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« Reply #10 on: February 26, 2009, 08:31:39 PM »

This thread brought back a memory from several years ago and made me chuckle.  Back when I first purchased my bus, there was a friend of mine that was heavily into NASCAR.  Partially inspired by my bus, he went out and bought a travel trailer to take to the races. Realizing he would be parked in the infield with no electrical hook up, he purchased a cheap contractor generator.

As he tells the story, he takes his rig to his first race and ends up parked next to a nice bus conversion (obviously much nicer than mine).  My friend fires up the generator and the thing starts making one hell of a racket.  Twenty minutes later there is a knock on his camper door.  It's the guy with the bus conversion. He says "Look Pal, I'll make you a deal. If you shut off that noisemaker I'll let you plug your camper into my buddy plug for the rest of the weekend."   He shut it down. End of story.
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Sean
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« Reply #11 on: February 26, 2009, 09:03:04 PM »

I have to disagree about the RPM thing. I've read this over and over on the board but have never seen any proof of this.

My own experience going from an air cooled Onan to a liquid cooled Honda is that the Honda is probably 1/4 as noisy and far smoother.

We're comparing apples to oranges ...



Yes, you are comparing apples and oranges.  My comment pertained strictly to fixed-rpm, diesel generators, which is what the OP asked about.  The Honda you are talking about is likely a variable-rpm (inverter-type) gasoline generator.  Two different animals and not really comparable at all (although sound pressure, in dB, can, of course, be compared).  Also, it should go without saying that a liquid-cooled engine will be quieter than an air-cooled engine of similar horsepower, so, here again, it's apples to oranges.

Also, my concern does not pertain to sound level alone, but to all facets of operation.  (That said, the noise alone is reason enough to skip them, IMO.  More than once I've been tempted to take my cutters to the fuel lines of such generators when some inconsiderate boor has set one up a few yards away from us.)

An 1800-rpm unit will run quieter and last longer than a similarly-constructed 3600-rpm unit of the same wattage.

-Sean
http://OurOdyssey.BlogSpot.com
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cody
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« Reply #12 on: February 27, 2009, 06:23:22 AM »

I had one guy ask me to fire up my inverter honda so he could hear how loud or quiet it was, he was standing right outside the bay it was parked in, the bay door was closed and it was running.
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luvrbus
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« Reply #13 on: February 27, 2009, 06:44:47 AM »

Cody, you set the bar high with that one is going to be hard to top LOL How is Libby doing
« Last Edit: February 27, 2009, 07:40:27 AM by luvrbus » Logged

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cody
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« Reply #14 on: February 27, 2009, 07:26:36 AM »

Clifford, I'm afraid it's going to be a long haul for libby, she has some problems that are going to be difficult for a long time, her lungs have been damaged, she has one kidney that is pretty much gone and the other is only working at a fraction of what it should, just enough at this point to keep away from dialysis, she is apparently having small strokes regularily and her heart is damaged, she has a long uphill battle ahead of her but I'm hopefull.  Emotionally she has her ups and downs but she is starting to realize that it will just take time. My bus had a 23.5K generator before I bought it, in order to make it affordable I let the PO keep the generator since it was new, the bay that it sat in was soundproofed  accordingly, thats the bay I had my little honda sitting in when the guy asked me if he could hear it run lol.  My little honda likes to sit there and hum just to keep itself company lol.
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