× Didn't find what you were looking for? Ask a question
Top Posters
Since Sunday
7
n
3
j
3
o
2
x
2
c
2
2
p
2
n
2
3
2
C
2
z
2
Home Q & A Board Science-Related Homework Help Physics
New Topic  
$abood$ $abood$
wrote...
Posts: 114
Rep: 0 0
11 years ago
I have two problems but I can't find the equations to solve them, the first is "a sound system produces 90dBSPL at 4 feet with 1 watt of input. How much power will be needed to produce 105dBSPL at 75 feet?"

And the second problem is "A sound system produces 90dBSPL at 4 feet with 1 watt of input. At 5,000 watts, what will the sound level be at 100 feet?"

I would be thankful for any help.
Read 463 times
1 Reply

Related Topics

Replies
wrote...
#1
11 years ago
I would use this equation:

Lp = Lw-20*log(r)-0.5

where:
Lp = sound pressure level (dB)
Lw = sound power level where Lw = 10*log(W/Wreference) where Wreference = 10^-12 watts
r = distance from the source in feet

and all of these logs are base-10 logs.

One thing I'm not sure of is whether sound power level can be equated to the input power in the problem statement (both are in watts)
New Topic      
Quick Reply
Explore
Post your homework questions and get free online help from our incredible volunteers
  944 People Browsing
Start New Topic Take the Tour CoursesNew Study Tools Topics Trending Browse by Textbook
Related Images
  
 1150
  
 155
  
 1049
Your Opinion
What's your favorite funny biology word?
Votes: 329
Previous poll results: What's your favorite math subject?