Exponents and decibels

Phoebert

New member
Joined
Nov 22, 2013
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2
So here is a problem I am having trouble with:

Under certain conditions, I=10^(D/10) where D is the number of decibels and I is its intensity. If he shouts with 30 more decibels than she talks with, what is the ratio of his intensity to hers?

This is the way I was thinking:
Her Intensity I: I(hers) = 10^(D/10)
His Intensity I: I(his) = 10^[(D+30)/10] = 10^[(D/10)+(30/10)] = 10^(D/10) * 10^3

So the ratio would be I(his)/I(hers) = [10^(D/10) * 10^3] / 10^(D/10) = 10^3
... which would be 1000:1

But the answer is really 3:1
Can someone tell me where I went wrong?
 
So here is a problem I am having trouble with:

Under certain conditions, I=10^(D/10) where D is the number of decibels and I is its intensity. If he shouts with 30 more decibels than she talks with, what is the ratio of his intensity to hers?

This is the way I was thinking:
Her Intensity I: I(hers) = 10^(D/10)
His Intensity I: I(his) = 10^[(D+30)/10] = 10^[(D/10)+(30/10)] = 10^(D/10) * 10^3

So the ratio would be I(his)/I(hers) = [10^(D/10) * 10^3] / 10^(D/10) = 10^3
... which would be 1000:1

But the answer is really 3:1
Can someone tell me where I went wrong?
+30 db is a factor of 1000.
 
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