Acoustics Comment on PPI Prep Manual  log10
I'm using PPI's Prep Manual 5.0 to prepare for PPD. The section on acoustics sound intensity level has been confusing me (pages 1913 & 1914) because the way PPI writes the Common Log as used in Equation 19.6 for Addition of Decibels of Uncorrelated Sound is not clear. Common Log is log base 10; however their equation also uses 10 as a multiplier...which is confusing. To clarify in the hopes this is useful to others:
 PPI writes "10logn" as part of the equation.
 This part of the equation actually means "10 x the common log of n"
 In other words, take the number of sources and multiply it by log base 10; then multiply that by 10; then go on with the rest of the equation.
I'm not good as math so this has been confusing to me and taken a solid hour+ to figure out. I hope this helpful to others.

Seth,
When I was studying for PPD I ran into this equation in Ballast as well. I skipped over it and was happy I did. In my opinion, I would focus more on understanding the questions the exam provides you. This extraneous information is good to have a general understanding of but if I were a betting man I couldn't imagine them asking you to any equations that would require memorizing this formula.
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