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Whats a more effective top exhaust blowhole?

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Emericana

Member
Joined
Jan 8, 2002
Location
Boulder CO
If I place 3 80mm fans, all 33cfm on the top for a blowhole, in a triangle position, or one 120mm 80cfm fan at the top. The 80mm fans are all around 30dba so it would be quieter than a 35dba 120mm.
 

JigPu

Inactive Pokémon Moderator
Joined
Jun 20, 2001
Location
Vancouver, WA
deadhead said:
just my opinion, but wouldnt
30+30+30 dba=90dba and that would be louder than the 35 dba
No, sound level is logarithmic so it would add up to a little over 35dBa. The 80mm would be quiter but not by much. So, you can get a little quiter or an extra 19cfm.

JigPu
 

Iron Hawk

Member
Joined
Jan 19, 2002
Location
Groton, CT
does any one know of a simple formula for adding dB? or is it quite complex and requries things like placement of the sound emitting objects etc.?
 

takiwa

Member
Joined
Dec 15, 2001
when acoustical sound doubles, it increases 3.01dB...I could give you the formula, but just add 3.01dB and you'll be fine :D

30dB = 1 fan
33.01dB = 2 fans
36.02dB = 3 fans

The 1dB difference would be non-audible to the human ear, so I would go with the 3 fans for more CFM...IMHO