• Support PF! Buy your school textbooks, materials and every day products Here!

Fireworks Sound level at difference distances

  • Thread starter norcal36
  • Start date
8
0

Homework Statement:

A firework goes off high above you, a distance d1=500m from your head, and you hear an acoustic pressure of 10Pa. Your sister is a distance d2=4.00x10^3 at the same time. If air absorbs 7.00 db/km in sound energy what sound level does your sister hear? Density of air=1.2kg/m^3....Speed of sound=343m/s.

Homework Equations:

I=pmax^2/2*density*velocity
I=power/Area
10log(I/I0)
This is the work I've done so far......

I=p^2/2dv........I=(10)^2/2(1.2)(343)=.12112

I(A)=P.........(.12112)(4pi(500)^2)=380522.366

I=P/A........380522.366/4pi(4000)^2=.0018925

10log(I/I0).......10log(.0018925/10^-12)=92.77db

92.77-7(4)=64.77db

I am winging it and that's the closest I can get to the right answer which is 68.3db....

Any Guidance would be greatly appreciated!!!!
 

Answers and Replies

33,564
9,295
The 10 Pa at your place already had 3.5 dB absorption from the air in the first 0.5 km. You only need to consider 3.5 km more, that increases the sound level by 3.5 dB relative to your calculation and produces a perfect match.
 

Related Threads for: Fireworks Sound level at difference distances

Replies
3
Views
5K
  • Last Post
Replies
0
Views
3K
  • Last Post
Replies
5
Views
3K
Replies
7
Views
6K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
5
Views
1K
  • Last Post
Replies
1
Views
2K
Replies
1
Views
5K
Top