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Does dBA add up?
- Thread starter envy
- Start date
- Joined
- Jul 3, 2004
- Location
- Austin
well, you won't hear the fans that our quieter than your loudest fan but i think it does add up to a certain extent...think if you had one tornado and a million vantec stealth fans.....you probably wouldn't hear the tornado
- Joined
- Jul 12, 2004
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- Lake Bodom
Think of it this way, if you had 5 30dBA fans, and it added up to 150dBA which would be like a loud speaker in your face.
- Joined
- Jan 19, 2003
Diggrr said:
yep, it's a logarithmic scale.
- Joined
- Jul 11, 2003
- Location
- Next Door door to Hell
BUT if you had a 40db fan and a 30db fan.............
Would it not be 41.5db?
Would it not be 41.5db?
- Joined
- Jan 19, 2003
squirtle632 said:
I don't think so.
- Joined
- Dec 7, 2003
- Location
- Portland, OR usa
squirtle632 said:
well lets see.
if I recall, bels are log10(sound energy) - that is, a sound 1 bel louder has 10 times the sound energy (and "sounds" about twice as loud.)
40 dB = log10(X), X units of sound energy.
30 dB = log10(X)-1 = log10(X/10), X/10 units of sound energy.
add them you get X * 1.1 units of sound energy.
log10(X*1.1) = log10(X)+log10(1.1) = 40 dB + 0.041 dB = 40.04 dB
so yes the loudest sound very much dominates. Adding a 30 dB sound source to a 40 dB sound source would be completely unnoticeable.
the wesson
- Joined
- Nov 30, 2002
- Location
- California
yep, its like my mom starts yelling with my 100+dba guitar amp on 
Even a vacuum (about 80dba) cannot be heard over my guitar amps
thats a real world situation for ya
i made a proggy a while ago that adds up dbA, cuz logs are hard and annoying (well.. atleast in calculus they are)
http://www.overclockers.com/tips1129/
Even a vacuum (about 80dba) cannot be heard over my guitar amps
thats a real world situation for ya
i made a proggy a while ago that adds up dbA, cuz logs are hard and annoying (well.. atleast in calculus they are)
http://www.overclockers.com/tips1129/
- Joined
- Aug 15, 2004
- Location
- California
well ive been around a system with a vantec tornado rated for 55db and i have a 175mm server fan thats rated for 55db but i can tell you the tornado is way way way more annoying. its high pitched, but the server fan is really deep.
so if im going to listen to something loud then i would rather have it be deep then high pitched
so if im going to listen to something loud then i would rather have it be deep then high pitched
TheWesson already gave a good math description of why it doesn't add up to be that much louder, but I think you will be able to hear it at a greater distance. Now this just may be me making stuff up, because I'm too lazy to look up the physics equations, but... I think the more lets say 30 db sources you have the farther away you will be able to hear them, although they will not sound that much louder than a single source.
Real world example: football stadium; there are 50,000 people cheering after a touchdown; the sound of that is not much louder than if there were just a few people next to you cheering, however you can probobly hear it from a half mile away at the back of the stadium parking lot, whereas if it were just a few people cheering you would not be able to hear it from that far
Real world example: football stadium; there are 50,000 people cheering after a touchdown; the sound of that is not much louder than if there were just a few people next to you cheering, however you can probobly hear it from a half mile away at the back of the stadium parking lot, whereas if it were just a few people cheering you would not be able to hear it from that far
- Joined
- Aug 20, 2002
- Location
- Brooklyn, NY
A decibel is a logarithmic function that is proportional to a power with a base of 10. This means that the higher number represent far more energy than the lower numbers.
Take a look at this:
10^0=1
10^1=10
10^2=100
10^3=1000
10^4=10000
The dbA rating is like the 1,2,3,4 in the above. Using the above example, something with a rating of 2 combined with something else with a rating of 2, will give a total energy level of 200...not 10000. So 2 + 2 would equal 2.3 (the log of 200)
Take a look at this:
10^0=1
10^1=10
10^2=100
10^3=1000
10^4=10000
The dbA rating is like the 1,2,3,4 in the above. Using the above example, something with a rating of 2 combined with something else with a rating of 2, will give a total energy level of 200...not 10000. So 2 + 2 would equal 2.3 (the log of 200)
- Joined
- Apr 7, 2002
- Location
- Norway, the red house, under the bed
But remember that dB value is all about _energy_ of sound. (W/m^2 I think)
Example to prove what I'm trying to say:
Does a room look twice as lit up with a 120w lightbulb than with a 60w ?
The energy might have doubbled, but the fan(s) doesn't sound twice as high.
I've heard that +6 dBA sounds about doubble as loud.
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And also you have dB A, B, C and so on that indicates what range of freq. is messured.
Example to prove what I'm trying to say:
Does a room look twice as lit up with a 120w lightbulb than with a 60w ?
The energy might have doubbled, but the fan(s) doesn't sound twice as high.
I've heard that +6 dBA sounds about doubble as loud.
--------
And also you have dB A, B, C and so on that indicates what range of freq. is messured.
- Joined
- Apr 27, 2002
JohnDoemakt said:
for humans 10db difference is interpreted as twice as loud.
