Overclock.net › Forums › Specialty Builds › Silent Computing › 2x 30dba fans=60dba of total noise???
New Posts  All Forums:Forum Nav:

2x 30dba fans=60dba of total noise???

post #1 of 9
Thread Starter 
hi,
i want to buy tons of fans for my radiators.i also want the best cooling possible without too much noise...
so my question is,would 2 fans rated 30 dba cause 60 dba noise when operating together?
this question might not make any sense..i am a noob...please help

thanks in advance
abdulla
post #2 of 9
Here's how you can calculate it.

dB1 + dB2 = 10 log (10^(dB1/10) + 10^(dB2/10))
I like turtles ^^
(15 items)
 
  
CPUMotherboardGraphicsRAM
i7 980x Gigabyte X58A-OC HIS Radeon HD 6970 2 GB Turbo 16GB Kingston HyperX 
Hard DriveHard DriveCoolingOS
WD Caviar Blue 640 GB + WD Caviar Blue 320 GB Silicon Power SSD V30 60Gb Antec Khuler 620 Windows 8 professional 64bits 
MonitorKeyboardPowerCase
22" LG + 17" LG Razer Blackwidow Ultimate Be Quiet Pure Power L8-CM-530W Antec 900 
MouseMouse Pad
Logitech G400 Roccat Taito 
  hide details  
Reply
I like turtles ^^
(15 items)
 
  
CPUMotherboardGraphicsRAM
i7 980x Gigabyte X58A-OC HIS Radeon HD 6970 2 GB Turbo 16GB Kingston HyperX 
Hard DriveHard DriveCoolingOS
WD Caviar Blue 640 GB + WD Caviar Blue 320 GB Silicon Power SSD V30 60Gb Antec Khuler 620 Windows 8 professional 64bits 
MonitorKeyboardPowerCase
22" LG + 17" LG Razer Blackwidow Ultimate Be Quiet Pure Power L8-CM-530W Antec 900 
MouseMouse Pad
Logitech G400 Roccat Taito 
  hide details  
Reply
post #3 of 9
No, but they'd be slightly louder than a single fan at 30 dBA.
M1XN
(18 items)
 
Study Zenbook
(5 items)
 
 
CPUMotherboardGraphicsRAM
i7 4770K @ 4.2 GHz ASUS Maximus VI Impact MSI GTX 970 Gaming 4G 2x8 GB Kingston HyperX DDR3 @ 2400 MHz 
Hard DriveHard DriveHard DriveOptical Drive
Crucial M4 64 GB Crucial M4 128 GB SAMSUNG Spinpoint M9T 2 TB LiteOn DL-8ATSH 
CoolingOSMonitorKeyboard
Noctua NH-C14 Windows 10 64-bit ViewSonic VP2770 Vortex Pok3r 
PowerCaseMouseMouse Pad
Corsair SF600 NCASE M1 V2.5 Logitech G502 SteelSeries QcK+ 
AudioOther
HiFiMan HE-400 Logitech C920 
CPUGraphicsRAMHard Drive
i5-3317 GT 620M 2 GB soldered + 8 GB Corsair OCZ Vertex 3 120 
OS
Windows 7 Home Premium 64-bit 
  hide details  
Reply
M1XN
(18 items)
 
Study Zenbook
(5 items)
 
 
CPUMotherboardGraphicsRAM
i7 4770K @ 4.2 GHz ASUS Maximus VI Impact MSI GTX 970 Gaming 4G 2x8 GB Kingston HyperX DDR3 @ 2400 MHz 
Hard DriveHard DriveHard DriveOptical Drive
Crucial M4 64 GB Crucial M4 128 GB SAMSUNG Spinpoint M9T 2 TB LiteOn DL-8ATSH 
CoolingOSMonitorKeyboard
Noctua NH-C14 Windows 10 64-bit ViewSonic VP2770 Vortex Pok3r 
PowerCaseMouseMouse Pad
Corsair SF600 NCASE M1 V2.5 Logitech G502 SteelSeries QcK+ 
AudioOther
HiFiMan HE-400 Logitech C920 
CPUGraphicsRAMHard Drive
i5-3317 GT 620M 2 GB soldered + 8 GB Corsair OCZ Vertex 3 120 
OS
Windows 7 Home Premium 64-bit 
  hide details  
Reply
post #4 of 9
The unit Bel, usually talked about as one tenths of Bels, with the prefix deci- (because one Bel would be an enormous unit, we use decibels, abbreviated dB) is a logarithmically scaling unit.

Doubling the sound pressure raises the sound pressure level with 6 dB, here's some info on it.

So you'd be looking at 36dB when you do an addition of 30dB + 30dB.

This is an even better website that also talks about the relation of voltage, power and perceived loudness:
http://www.gcaudio.com/resources/howtos/voltageloudness.html
Edited by seepra - 11/8/12 at 6:25pm
Lenovo Y500
(5 items)
 
Byte
(13 items)
 
 
CPUGraphicsRAMOS
Intel i7 3630QM NVIDIA Geforce GT 650M SLI 16GB SO-DIMM DDR3 Windows 8 
Audio
AKG K 272 HD 
CPUMotherboardGraphicsRAM
Intel i5 3570K Asus P8H77-I GTX 580 Phantom Kingston HyperX blu 1600MHz 
Hard DriveCoolingOSPower
Samsung 840 120GB Thermalright HR-02 Macho Linux Ubuntu Studio 12.04 Super Flower 550W Golden King 
CaseAudioAudioAudio
Bitfenix Prodigy (white) M-Audio Fast Track Pro M-Audio BX5a D2 AKG K 272 HD 
Audio
Behringer B3031A 
  hide details  
Reply
Lenovo Y500
(5 items)
 
Byte
(13 items)
 
 
CPUGraphicsRAMOS
Intel i7 3630QM NVIDIA Geforce GT 650M SLI 16GB SO-DIMM DDR3 Windows 8 
Audio
AKG K 272 HD 
CPUMotherboardGraphicsRAM
Intel i5 3570K Asus P8H77-I GTX 580 Phantom Kingston HyperX blu 1600MHz 
Hard DriveCoolingOSPower
Samsung 840 120GB Thermalright HR-02 Macho Linux Ubuntu Studio 12.04 Super Flower 550W Golden King 
CaseAudioAudioAudio
Bitfenix Prodigy (white) M-Audio Fast Track Pro M-Audio BX5a D2 AKG K 272 HD 
Audio
Behringer B3031A 
  hide details  
Reply
post #5 of 9
Quote:
Originally Posted by seepra View Post

The unit Bel, usually talked about as one tenths of Bels, with the prefix deci- (because one Bel would be an enormous unit, we use decibels, abbreviated dB) is a logarithmically scaling unit.
Doubling the sound pressure raises the sound pressure level with 6 dB, here's some info on it.
So you'd be looking at 36dB when you do an addition of 30dB + 30dB.
This is an even better website that also talks about the relation of voltage, power and perceived loudness:
http://www.gcaudio.com/resources/howtos/voltageloudness.html

Doesn't that only apply as long as the sounds are close in power?
post #6 of 9
Quote:
Originally Posted by OwnedINC View Post

Doesn't that only apply as long as the sounds are close in power?
Well, when you double something, you take the same number twice, no? tongue.gif

Or if you're talking about actual power as in Watts, then adding 6dB to SPL takes double the wattage to produce.

EDIT: In addition to this for the OP
Understanding how sound pressure level works (ie: doubling every 6dB) will help you read reviews and comparisons of different fans, but you shouldn't ever try mixing different values from different batches of measurement, like different manufacturers stating whatever SPL levels for their fans at whatever RPM, or different reviews to other reviews. They rarely specify how are they measured and in which conditions, so you can't really directly compare them. (This is also because of different ambient noise, different other possibly noisy PC components, and very likely way different ambient temperatures). You should rather look at one of those huge fan "round-ups" where they take many fans and measure them in similar conditions. There you will see a better picture of how fans perform against each other. Just throwing this out there in case it's not obvious in the first place.

Here's one 2012 fan round-up for you

Also, if you ever want to find out your real SPL the fans and components are churning out after you've built the computer, you should rather get a SPL meter than try calculating different components and their reported/reviewed sound pressure levels together, they are unlikely to match and things like resonance, case and it's dampening properties will all affect the output somehow.
Edited by seepra - 11/8/12 at 6:45pm
Lenovo Y500
(5 items)
 
Byte
(13 items)
 
 
CPUGraphicsRAMOS
Intel i7 3630QM NVIDIA Geforce GT 650M SLI 16GB SO-DIMM DDR3 Windows 8 
Audio
AKG K 272 HD 
CPUMotherboardGraphicsRAM
Intel i5 3570K Asus P8H77-I GTX 580 Phantom Kingston HyperX blu 1600MHz 
Hard DriveCoolingOSPower
Samsung 840 120GB Thermalright HR-02 Macho Linux Ubuntu Studio 12.04 Super Flower 550W Golden King 
CaseAudioAudioAudio
Bitfenix Prodigy (white) M-Audio Fast Track Pro M-Audio BX5a D2 AKG K 272 HD 
Audio
Behringer B3031A 
  hide details  
Reply
Lenovo Y500
(5 items)
 
Byte
(13 items)
 
 
CPUGraphicsRAMOS
Intel i7 3630QM NVIDIA Geforce GT 650M SLI 16GB SO-DIMM DDR3 Windows 8 
Audio
AKG K 272 HD 
CPUMotherboardGraphicsRAM
Intel i5 3570K Asus P8H77-I GTX 580 Phantom Kingston HyperX blu 1600MHz 
Hard DriveCoolingOSPower
Samsung 840 120GB Thermalright HR-02 Macho Linux Ubuntu Studio 12.04 Super Flower 550W Golden King 
CaseAudioAudioAudio
Bitfenix Prodigy (white) M-Audio Fast Track Pro M-Audio BX5a D2 AKG K 272 HD 
Audio
Behringer B3031A 
  hide details  
Reply
post #7 of 9
Nah, when you have two noise sources, generally the sound waves produced should be uncorrelated with each other. You don't have them adding constructively. Thus with two equal SPL sources, you get +3 dB, not +6 dB (no A-weighting or anything like that).

In practice, I'm not sure that's what people measure. Often they come up with lower figures than +3 dB at lower SPL, maybe because of measurement inaccuracy? If this is wrong, do you have an example of results where two fans are tested to have same SPL each and then when run together (not like push-pull where characteristics would change) increase the SPL by something like 6 dB?


This should be correct in theory:
Quote:
Originally Posted by MrDucktape View Post

Here's how you can calculate it.

dB1 + dB2 = 10 log (10^(dB1/10) + 10^(dB2/10))

which gives +3 dB for equal dB1 and dB2.
post #8 of 9
Quote:
Originally Posted by mikeaj View Post

Nah, when you have two noise sources, generally the sound waves produced should be uncorrelated with each other. You don't have them adding constructively. Thus with two equal SPL sources, you get +3 dB, not +6 dB (no A-weighting or anything like that).
In practice, I'm not sure that's what people measure. Often they come up with lower figures than +3 dB at lower SPL, maybe because of measurement inaccuracy? If this is wrong, do you have an example of results where two fans are tested to have same SPL each and then when run together (not like push-pull where characteristics would change) increase the SPL by something like 6 dB?
This should be correct in theory:
which gives +3 dB for equal dB1 and dB2.
Ah you're right, it's a while since I fiddled with sound pressure levels sorry.

That is true, for non-coherent separate sources it's +3dB every time you add a similar fan, assuming identical fans with no flaws.

Could someone still confirm the increase in dB of the perceived loudness, because that's what we're most likely caring the most about ITT?
EDIT: found it, for perceived loudness to double, the amount of dB increased is 10dB. So adding two similar fans is not going to double the perceived loudness, that's struck me a bit weird at first but I guess it makes sense.
Edited by seepra - 11/9/12 at 4:40am
Lenovo Y500
(5 items)
 
Byte
(13 items)
 
 
CPUGraphicsRAMOS
Intel i7 3630QM NVIDIA Geforce GT 650M SLI 16GB SO-DIMM DDR3 Windows 8 
Audio
AKG K 272 HD 
CPUMotherboardGraphicsRAM
Intel i5 3570K Asus P8H77-I GTX 580 Phantom Kingston HyperX blu 1600MHz 
Hard DriveCoolingOSPower
Samsung 840 120GB Thermalright HR-02 Macho Linux Ubuntu Studio 12.04 Super Flower 550W Golden King 
CaseAudioAudioAudio
Bitfenix Prodigy (white) M-Audio Fast Track Pro M-Audio BX5a D2 AKG K 272 HD 
Audio
Behringer B3031A 
  hide details  
Reply
Lenovo Y500
(5 items)
 
Byte
(13 items)
 
 
CPUGraphicsRAMOS
Intel i7 3630QM NVIDIA Geforce GT 650M SLI 16GB SO-DIMM DDR3 Windows 8 
Audio
AKG K 272 HD 
CPUMotherboardGraphicsRAM
Intel i5 3570K Asus P8H77-I GTX 580 Phantom Kingston HyperX blu 1600MHz 
Hard DriveCoolingOSPower
Samsung 840 120GB Thermalright HR-02 Macho Linux Ubuntu Studio 12.04 Super Flower 550W Golden King 
CaseAudioAudioAudio
Bitfenix Prodigy (white) M-Audio Fast Track Pro M-Audio BX5a D2 AKG K 272 HD 
Audio
Behringer B3031A 
  hide details  
Reply
post #9 of 9
Thread Starter 
thanks for all the replies and help everyone...biggrin.gif
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Silent Computing
Overclock.net › Forums › Specialty Builds › Silent Computing › 2x 30dba fans=60dba of total noise???