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Due to installation of a muffler, the noise level of an engine was reduced from 88 to...

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betpanos | Student | (Level 3) eNoter

Posted March 21, 2013 at 3:00 AM via web

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Due to installation of a muffler, the noise level of an engine was reduced from 88 to 72 decibels. Find the percent decrease in the intensity level of the noise as a result of the installation of the muffler.

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted March 21, 2013 at 3:20 AM (Answer #1)

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The noise level in terms of decibels is given by `10*log(I/I_r)` where `I_r` is a reference intensity.

When the noise level is 88, the corresponding intensity is `I_r*10^8.8` . For a noise level of 72, the corresponding intensity is `I_r*10^7.2`

The percent decrease in intensity is `((I_r*10^8.8 - I_r*10^7.2)*100)/(I_r*10^8.8)`

= `((10^8.8 - 10^7.2)*100)/10^8.8`

`~~ 97.48%`

There is an approximate decrease in noise intensity levels of 97.48% due to the installation of the muffler.

Sources:

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betpanos | Student | (Level 3) eNoter

Posted March 21, 2013 at 12:39 PM (Answer #2)

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The noise level in terms of decibels is given by where is a reference intensity.

When the noise level is 88, the corresponding intensity is . For a noise level of 72, the corresponding intensity is

The percent decrease in intensity is

=

There is an approximate decrease in noise intensity levels of 97.48% due to the installation of the muffler.

How did you find: When the noise level is 88, the corresponding intensity is . For a noise level of 72, the corresponding intensity is ?

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