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How to compare decibels?

How many times greater is the intensity of a sound of 110 dB than the intensity of a sound of 90 dB?

Please show me how to do this, I'm not just looking for a free pass on my homework.

1 Answer

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  • 1 decade ago
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    The relationship between the intensity of sound and its dB measurement is given by the equation in

    http://hyperphysics.phy-astr.gsu.edu/hbase/sound/i...

    dB = 10 log(I/Io) <the log is to base 10>

    Dividing by 10 and then taking 10 to the power of both sides,

    I/Io = 10^(dB/10), si

    I = lo*10^(dB/10).

    Therefore the intensity of a 110 dB sound is

    Io * 10^(110/10) = 10^11 Io.

    And the intensity of a 90 dB sound is

    Io * 10^(90/10) = 10^9 Io.

    So to find the number of times greater the intensity of a 110 dB is, just divide them. The 110 dB intensity is

    (10^11 Io)/(10^9 Io)

    = 10^11/10^9 <Io's cancel>

    = 10^2 = 100.

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