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adding fan noise

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Kasmodean

Registered
Joined
Aug 30, 2002
Location
MA
If i get 4 fans rated at like 36-39 dB each and run them altogether how loud would it be? Also since I have no idea what the low dB sounds sound like and you compare it to something? I am doing this for a amp rack in my car and don't want to hear the fan noise from the hatch.
 

Cjwinnit

B&
Joined
Feb 1, 2003
Location
UK
Kasmodean said:
If i get 4 fans rated at like 36-39 dB each and run them altogether how loud would it be? Also since I have no idea what the low dB sounds sound like and you compare it to something? I am doing this for a amp rack in my car and don't want to hear the fan noise from the hatch.

It's logarithmic.

With 4 similar noise sources, add 6 Decibels to the noise.
 

Zerileous

Senior Member
Joined
Jun 21, 2002
I HATE LOGARITHMS THEY ARE EVIL! MAYBEE THEY WOULD BE OK IF MY ALGEBRAII TEACHER HAD EXPLAINED THEM INSTEAD OF JUST SHOWING US HOW TO PRESS BUTTONS ON A CALCULATOR!

ok sorry bout the rant-its nice to know that its lograrithmic despite the ammount of hate i have for logs. Im assuming its figured in log 10 (cursory calculations agree with this)
 

DarkJediSleikas

Member
Joined
Aug 17, 2002
Location
Milwaukee School of Engineering
Here is a place where you can get some sample recordings of various fans at different sound intensities:

http://www.sidewindercomputers.com/tecar.html

It is important to note that the manufacters' specified sound intensity is going to be lower than those shown in the above link. I would assume that your fans are about 40-45 dB on their scale.

I will spare you the details of how multiple sound sources interfere (constructive/destructive interference). It is often assumed that two sources with the same intensity will result in doubling the effective sound intensity. Thus, doubling the sound instensity will increase the intensity by 10*log(2) dB, or about 3dB. The formula is

Increase in dB = 10*log(X)

where X = the ratio of the new intensity over the old intensity

In your case,

Increase in dB = 10*log(4/1) = 6dB
 

ryuen

Member
Joined
Mar 25, 2003
Location
at home
then again, you cant always trust the manufacturers dba rating. so its not really exact. sidewindercomputers is a good place to compare fans noise wise
 

macklin01

Computational Oncologist / Biomathematician / Mode
Joined
Apr 3, 2002
Location
Bloomington, IN
I definitely agree with you there. ;) No matter what the topic, you'll often find that at some point, you run up against a lack of information. (Or in some cases, an information disparity.) You just have to do the best you can with the limited information you have. -- Paul
 

arabarabian

Member
Joined
Feb 17, 2002
Location
Sterling,MA
It would be very lound. It has the effect of many people talking in the same room. So if you plan wisely you will get an overall suitable fan noise level.


Thank You,
Daniel