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Decibel Question (adding I think)

  1. Apr 10, 2005 #1
    Question at hand, A noisy machine in a factory produces a decibel rating of 80 dB. How many identical machines could you add to the factory without exceeding the 90 dB limit set by federal regulations?


    I just did a bunch of other problems regarding h/z and m/s and they were all right :biggrin: , so I don't understand why this program is on webassign. Anyway, 1 machine is producing 80db and I need to figure out how many more machines they can add without going over 90db.

    I'd love to know where to start....
     
  2. jcsd
  3. Apr 10, 2005 #2

    dextercioby

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    What is the connection between Bells and Watts...?

    Daniel.
     
  4. Apr 11, 2005 #3

    BobG

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    Decibels are measured using common logarithms (except, with a "deci-" prefix, you're actually measuring tenths of a Bel).

    The common log of 2 is approximately .301, or, very approximately, .3. That's not a very appealing number, so, by using decibels (tenths of a Bel), we get 3 decibels.

    The common log of 10 is 1.0, the common log of 100 is 2.0, the common log of 1000 is 3.0, etc. In decibels, the above would be 10, 20, 30, etc.
     
  5. Apr 11, 2005 #4

    dextercioby

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    Isn't it from A.G.Bell?As Watt from J.Watt?:confused:


    Daniel.
     
  6. Apr 11, 2005 #5

    BobG

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    Yes, but it's stilled spelled with just one 'l'.

    Why, I'm not quite sure. I know a few coorporations donated some vowels to a Eastern European relief effort, due to the scarcity of vowels in the names of Eastern European people. Maybe Bell Telephone Labs made a similar effort to seed the Finnish-Czechoslavakian consonant-vowel trade agreement.
     
  7. Apr 11, 2005 #6

    FredGarvin

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    An increase of 10 dB means that the power ratio in the definition of the dB has to increase by 10. Can you calculate what the power ratio with one machine running is? Do you know what the reference power is?
     
  8. Apr 11, 2005 #7

    Cliff_J

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    Or you could simply do the math so its applicable to any level increase.

    n * 10^8 = 10^9

    This would be in bels (divide by 10 to convert decibels to bels)

    Or to show what BobG looks like as a simple bit of math:

    2 * 10^8 = 10^8.3

    Or you could just do an antilog on the difference too. Like for the number of machiens to result in a 6db increase we have 10^0.6 = 4 times the initial number of machines.
     
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