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Basic Error in Sound Calcs?

Basic Error in Sound Calcs?

Basic Error in Sound Calcs?

(OP)
My reference, by noted authorities Don and Carolyn Davis, claim there are two methods to find dB-PWL (sometimes called Lw).  I find the methods differ by 10dB. What's up?
(Ref: "Sound System Engineering", 1st ed, 12th printing 1986, p.40)

a) Lw = 10 log (watts/watts ref)
b) Lw = 10 log (watts) + 120 dB
For:
watts = 1 W and watts ref = 10e-12, I find:
Equation (a) = 110 dB
Equation (b) = 120 dB

I believe my math is correct.  Is this an error by the author?
Thanks for any ideas/suggestions.

RE: Basic Error in Sound Calcs?

(OP)
Oh, I embarrased as I have found my mistake.  I entered 10^-12 watts into Excel as 10e-12.  This is a pitfall I have somehow always had a mental block on, and it is returning to haunt me here.  10^-12 = 1e-12 <> 10e-12.  

Sorry...thanks all for understanding.

RE: Basic Error in Sound Calcs?

I was explaining this distinction to my 6th-grade son just a week ago.
He looked at me as if I were speaking Martian...

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