Precalculus
posted by jh .
I have posted this question earlier as well but was unable to receive an answer. I don't know how to do this question at all, so PLEASE help me with this question and also show me the steps, so that I can learn. I would appreciate it a lot.
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
You 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
No unfortunately this is not the correct answer :(, is there any other way of doing this question?

Precalculus 
Reiny
Does the formula use natural logs perhaps (ln) ?
Was there a formula or relation given?
By how much is our answer off ? 
Precalculus 
jh
This 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
Ok 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
Yes, 1 is the answer. Thanks a lot for your help Reiny :)
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