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January 28, 2015

January 28, 2015

Posted by **jh** on Tuesday, March 9, 2010 at 8:33am.

A high sound level of 120 dB is regarded as the threshold of pain for the average listener. If the threshold of hearing is 10^−12 watts/m^2, then the intensity of the sound corresponding to 120 dB is

_________ watts/m^2.

- Precalculus -
**Reiny**, Tuesday, March 9, 2010 at 8:45amYou must be referring to

http://www.jiskha.com/display.cgi?id=1268004723

Using bobpursley's formul, he is very seldom wrong,

and my 10 digit display calculator, I got

10log(120/10^-12) as

130.79 or 131 decibels.

- Precalculus -
**jh**, Tuesday, March 9, 2010 at 8:59amNo unfortunately this is not the correct answer :(, is there any other way of doing this question?

- Precalculus -
**Reiny**, Tuesday, March 9, 2010 at 9:13amDoes the formula use natural logs perhaps (ln) ?

Was there a formula or relation given?

By how much is our answer off ?

- Precalculus -
**jh**, Tuesday, March 9, 2010 at 9:24amThis is an online assignment, we write the answer and the computer system recognizes whether the answer is right or wrong, but doesn't give any hint.

See if this helps:

The instructor gave us the formula 10log E/E0 and this

question told us what EO is so we just plugged it in then

we got rid of the 10 in front of the log by making it equal

to 12 instead of 120.....Someone already gave the equation

to solve earlier in the discussion Consider log(E/10^-12)=12

just solve for E we know that 10^12 = (E/10^-12) as this is

a log of common base ten then from here you solve for E

we also know that 10^-12 is also 1/10^12

hope these hints help

- Precalculus -
**Reiny**, Tuesday, March 9, 2010 at 9:39amOk then, if we are just solving

120 = 10log(E/10^-12) then it is easy

divide both sides by 10

12 = log(E(10^12))

which means e(10^12) = 10^12

E = 1

try that

- Precalculus -
**jh**, Tuesday, March 9, 2010 at 9:42amYes, 1 is the answer. Thanks a lot for your help Reiny :)

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