Volkswagen Passat Forum banner

1 - 6 of 6 Posts

·
Registered
Joined
·
4,407 Posts
Discussion Starter #1
hey guys,

So math isn't my strong suit. Im taking a Science class, and we did an experiment. basically I have a bunch of Decibel readings (taken with a sound meter) And I need to average them. All my teacher would tell me is that Decibels are Logrithmic, and so I can't just add them up and divide by the total.

and example is

66.1
65.6
66.3

-Nick
 

·
Retired PassatWorld Staff
Joined
·
6,165 Posts
You need to convert them back to their non-log forms. Decibles use a log(10) base not natural (ln), so you jsut need to use an inverse log function on your calc for each #

so,

(inv)log 66.1 = (really big friggin' #)
(inv)log 65.6 = (not as big)
....

average the really big #'s, and take the log of the average.
 

·
Registered
Joined
·
428 Posts
What pass-variant said.

Since dB = 10 log (ratio of power levels), averaging the decibel readings will actually give you a logarithmic mean. Following the steps pass-variant outlined will get you the arithmetic mean, which is what I think you want.
The arithmetic mean should be > logarithmic mean; for your example readings, the difference between the two will be slight, since the readings are fairly close to each other.
 

·
Registered
Joined
·
25,996 Posts
Just don't ask the guys who do it for the airport. They average the 20 seconds
a plane passes over into a 24hr day. It's a real suprise they say it does not violate
noise regs.
 
1 - 6 of 6 Posts
About this Discussion
5 Replies
5 Participants
PZ
Volkswagen Passat Forum
Passatworld is a forum dedicated to Volkswagen Passat enthusiasts to discuss mods, Quattro, Turbo Diesel, reviews and more!
Full Forum Listing
Top