Adding dB - Cannot figure out logs!

  • Thread starter RedPhoenix
  • Start date
  • #1
26
0

Homework Statement



A family ice show is held at an enclosed arena. The skaters perform to music with level 80.0 dB. This is too loud for your baby, who yells at 75.0 dB.

(a) What total sound intensity engulfs you?
(b) What is the combined sound level?


Homework Equations



dB = 10log(I/1E-12)

The Attempt at a Solution



I am trying to convert back, but I have never been great with logs, and I cannot figure out how to get I.

80=10log(I/1E-12)
75=10log(I/1E-12)







EDIT - it just clicked - anti-derivatives
A)
75db = 10^7.5/1E12 = I(b)
80db = 10^8/1E12 = I(m)
add them for total = 1.316E-4

B)
10log(1.316E-4/1E-12)
81.19dB
 
Last edited:

Answers and Replies

  • #2
76
0
A hint: Use the fact that 10^log x = x
 

Related Threads on Adding dB - Cannot figure out logs!

  • Last Post
Replies
15
Views
9K
Replies
5
Views
2K
Replies
6
Views
2K
Replies
8
Views
157
Replies
2
Views
1K
Replies
4
Views
2K
  • Last Post
Replies
2
Views
3K
Top