How loud is 20dB?

Luie · May 25, 2002

I have a 30dB fan in my case. Even when the case covers are closed, there is a very noticable hum. Difficult to sleep with that on. It sounds like people talking's volume from that 30dB.

I was wondering about Vantec's 20dB Stealth fan. How loud would 20dB be comparing with my 30dB Evercool fan? Would it be as quiet as the sound of snow fall when it is in a case with the covers closed?

1Time · May 25, 2002

20dB is pretty quiet. It's not likely to bother you. Of course you always could slow your fan speed down to make it more quiet if you need to.

Luie · May 25, 2002

How do I slow it down?

Tr0LL · May 25, 2002

u can lower it with a fan bus (I think that is what it's called - basically it controls fan speeds)

or if it's a case fan you can hook it up to use the 5v line instead of the normal 12v line... OR u can hook it up so that it usese 7v (red to 12v power, black to 5v power - i THINK, i'm sure u can fine more info about the 7v if u do a search)

It_The_Cow · May 25, 2002

30dB = 3B -> 10^3 = 1000

20dB = 2B -> 10^2 = 100

1000/100 = 10

The 20dB fan would seem to be ten times softer

rlemieux · May 25, 2002

Here is something that I posted a while ago here http://forum.oc-forums.com/vb/showthread.php?s=&threadid=86304&highlight=rumors. It is a gerneral chart on dbs comparing them to everyday noise.

Here is a list of dbs and what they compare to
Jet engine at 3m 140
Threshold of pain 130
Rock concert 120
Accelerating motorcycle at 5m 110
Pneumatic hammer at 2m 100
Noisy factory 90
Vacuum cleaner 80
Busy traffic 70
Quiet restaurant 50
Residential area at night 40
Empty movie house 30
Rustling of leaves 20
Human breathing (at 3m) 10
Threshold of hearing (good ears) 0

takiwa · May 25, 2002

30dB = 3B -> 10^3 = 1000

20dB = 2B -> 10^2 = 100

1000/100 = 10

The 20dB fan would seem to be ten times softer

Actually, it would appear to be half as loud.

3.01dB is the increase in SPL when you double the effective power to the source. So, an increase from 20dB to 23.01dB would mean a doubling of electrical power to the fan. However, human hearing is linear. A doubling of acoustical power (as percieved by our ears) takes approximately 9.03dB. If you heard a 20dB fan, and then a 30dB fan, you would think the 30dB fan was "twice as loud" as the 20dB fan.

Emericana · May 25, 2002

wow i would love to have only 30dba in my case lol. i betcha my case is like 46dba with all the fans put together! (sunon 50cfm 40dba, Panaflow and thermaltake 55cfm 92mm 35dba's, two ADDA 35cfm 35DBA's, One ADDA 30DBA 30DBA, and one loud *** psu ADDA 40CFM 40DBA fan) i betcha that my case is just as loud as a single Delta 68 with no other case fans installed or anything.

takiwa · May 25, 2002

Here is a list of dbs and what they compare to
Jet engine at 3m 140
Threshold of pain 130
Rock concert 120
Accelerating motorcycle at 5m 110
Pneumatic hammer at 2m 100
Noisy factory 90
Vacuum cleaner 80
Busy traffic 70
Quiet restaurant 50
Residential area at night 40
Empty movie house 30
Rustling of leaves 20
Human breathing (at 3m) 10
Threshold of hearing (good ears) 0

The range of human hearing is generally agreed upon to be from 20Hz-20,000Hz, with a few rare exceptions. So, the threshold of human hearing is usually set at 20. There are a few musical instruments that can reach 16Hz, but most of what is being heard is the secondary harmonic distortion being produced (which is higher than 16Hz) and not the 16Hz not itself.

subconcept · May 25, 2002

I wish my computer was that quiet

3 80 mm fans that are 20 dB
1 60mm that is 47 dba!!! (damn delta)
plus the enermax fan on psu
and 6 small 20 mm fans on my hd coolers

my pc is way to loud but i dont know how to keep it quiet

1Time · May 25, 2002

takiwa said:
The range of human hearing is generally agreed upon to be from 20Hz-20,000Hz, with a few rare exceptions. So, the threshold of human hearing is usually set at 20. There are a few musical instruments that can reach 16Hz, but most of what is being heard is the secondary harmonic distortion being produced (which is higher than 16Hz) and not the 16Hz not itself.

The frequency range is different than dB(A). The frequency shows how fast the sound waves are moving and the frequency range shows a human's limits with regard to perceiving high and low sounds. dB(A) refers to how loud the sound is, not how high or low it is.

takiwa · May 25, 2002

The frequency shows how fast the sound waves are moving and the frequency range shows a human's limits with regard to perceiving high and low sounds.

I am familiar with what dBa means. A-weighted sound level measurements are numerically adjusted to reflect the frequency-dependent nature of human hearing at low sound levels only. Since humans are less sensitive to sounds at low frequency, A-weighted sound levels will almost always be lower than flat, overall sound pressure levels reported in terms of decibels. The frequency range of human hearing is based on an A-weighted scale.

I was pointing out that the chart posted above was incorrect, and could not be used as a standard against the relative loudness of sounds in general. The threshold of human hearing is not 0dB, and human breathing (at 3m) may be 10dB, but it would be inaudible to you 3m away.

rlemieux · May 25, 2002

And this chart comes from stanford. I did not just asemble it myself.

Luie · May 25, 2002

btw, the loudness of the noice that my pc is making is actually 2x 30dB fans. (one on the CPU and one in the PSU.) the gfx card and the north bridge's fan is near inaudiable even at close range.

So, 2x 30dB fans sounds like a conversation between me and my friends. So, 2x 30dB = 50dB? or is it 60dB?

How loud would 2x 20dB Vantec's Stealth fans be? 40db?

It_The_Cow · May 25, 2002

takiwa said:
Actually, it would appear to be half as loud.

3.01dB is the increase in SPL when you double the effective power to the source. So, an increase from 20dB to 23.01dB would mean a doubling of electrical power to the fan. However, human hearing is linear. A doubling of acoustical power (as percieved by our ears) takes approximately 9.03dB. If you heard a 20dB fan, and then a 30dB fan, you would think the 30dB fan was "twice as loud" as the 20dB fan.

So exactly what did my math prove? I'm not too familiar enough with all the fields of sound

takiwa · May 25, 2002

How loud would 2x 20dB Vantec's Stealth fans be? 40db?

Close, it would be a little over 36dB.

And this chart comes from stanford. I did not just asemble it myself.

I knew you didn't, rlemieux, just didn't want anyone to be confused. I think they were trying to show a relation of sound pressure levels, rather than the actual dB ratings

So exactly what did my math prove? I'm not too familiar enough with all the fields of sound

You were right, It, you just said it the wrong way

takiwa · May 25, 2002

luie, without getting all crazy with math, here's a simple formula for adding dB's.

Take the first dB rating you have (in your case, 33dB) and divide it by 10.

Take 10 and raise it to the expontential value of your answer (10 to the 3.3 power, which would be 1995 rounded off).

Do that to the other dB rating as well (in this case, 33dB).

Add those to ratios together (1995+1995=3990).

Take the log of your answer (3.6)

Multiply by 10 (36dB)

This is close enough for you to know what the difference would be.

Luie · May 25, 2002

Thanks, Takiwa. You are a genius!

How loud is 20dB?

Luie

Member

1Time

Member

Luie

Member

Tr0LL

Member

It_The_Cow

Senior Member

rlemieux

Cyber Deal King

takiwa

Member

Emericana

Member

takiwa

Member

subconcept

Member

1Time

Member

takiwa

Member

rlemieux

Cyber Deal King

Luie

Member

It_The_Cow

Senior Member

takiwa

Member

takiwa

Member

Luie

Member

Similar threads