Is it all about the decibals

nmmnp · 11-04-2002, 02:53 PM

Tried to search this out, but didn't see anything. Sorry if this has been covered before but I've seen a lot of discussion on fans and something still confuses me when the subject turns to quiet fans. I know that different bearings can make a difference, but when comparing the same style fans (i.e. ball bearing) is it all about the decibals? I have an 92m Enermax adjustable speed fan (supposedly 41-52 cfm @ 18-32 db but I've been told these specs are off). Should this be quieter than any other ball bearing fan with a higher db rating, or are there other factors I'm missing?

Thanks

g.l.amour · 11-04-2002, 03:21 PM

well, if those specs are off, then there is no way in telling, is there?

anyway, only a minority is running these large fans at the 12V they are supposed to be running at. so to continue... if there was some efficiency difference at full speed (eg different fans @ 12V, same cfm, unequal dba rating) i guess that difference would become very very very small once they are both running in the 5 - 7V range most of us are running those fans.

the easiest way i have been able to tax a fan is to look at the amperage rating

e.g for 120's
smaller than 0.4A rating : +/- low noise
larger than 0.4A rating : +/- delta style

the enermax 120's are +/- 0.3A

e.g for 80's
smaller than 0.15A: +/- low noise
....

e.g for 90's
smaller than 0.20A: +/- low noise
....

gogo · 11-15-2002, 09:31 PM

Personally I wouldn't say it was all about decibles. Esp. since it can be hard to judge volume levels reported by different manufacturers. They (fans) are generally tested in ideal conditions by themselves. and given a dB rating.

I take many things into consideration mostly.

My cat.
I've had a few fans (mostly sunon) that at 5 or 7 volts must have put out some high pitched elec. noise cause they drove him nuts. I thought he was going insane until I happened to shut the computer down once while he was in the room.

My wife.
theres a tiny buzzing sound from the 90mm zalman at 5v or 7v.
I can't hear it unless I'm right next to it, but my wife spent half a day tracing it out. She swore up and down it was moving around the house and mostly near the fridge. That was fun.

Me.
I'm sick of noise. I don't even like the sound of air moving against things. I had a fanless computer far a day, but my nerves got to me and I put the fans back in at 5v and 7v.

bigben2k · 11-16-2002, 09:18 AM

I'll chime in on this one.

First of all, the noise comes from the fan blades striking the air, mostly. Some time back we had this discussion, and someone (dared to?!) tell me that I was wrong, until someone was kind enough to experiment with a fan. He recorded the noise, then clipped the fan blades and recorded it again. The noise was (mostly) gone.

Now, the noise is going to depend a lot on the fan blade geometry: too pitched, and they'll be noisier than hell, too flat, and they won't move enough air.

Someone understood this, and charted (from specs) all the fans he could find, into a nice cfm to noise ratio. The highest ratio unit is the most desirable, regardless of how much noise it makes at 12V, because it can be undervolted to an acceptable noise level, while delivering the highest airflow.

That being said... this chart only included axial fans. There are other types of fans, like the squirrel cage blower, which are (theoretically) much quieter than any axial fan...

bdunosk · 11-16-2002, 01:19 PM

Not to post-crap, but if you chop the blades off a fan, haven't you just removed a huge load on the fan's motor?

I personally can tell the difference between the motor noise and the noise from air turbulence on my 7-volted 120mm Panaflo H1A. The motor noise is usually a lot louder than the turbulence (usually, yes... I don't know why it sounds louder some times than others).

Alchemy · 11-16-2002, 05:15 PM

Quote:

Originally posted by bigben2k
Someone understood this, and charted (from specs) all the fans he could find, into a nice cfm to noise ratio. The highest ratio unit is the most desirable, regardless of how much noise it makes at 12V, because it can be undervolted to an acceptable noise level, while delivering the highest airflow.

Link, please?

Alchemy

bdunosk · 11-16-2002, 08:42 PM

Sounds like Gizzo's fan page. It's true that the highest CFM:dBa ratio is best, but the top fans don't move enough air for most applications. *shrug*

airspirit · 11-22-2002, 04:54 PM

Didn't somebody sand their fan blades and get quieter performance? I thought I read that somewhere, and Ben commented on it ....

MadDogMe · 11-23-2002, 05:09 AM

Yeah can you dig out a link BB please?...

I read where somedude put tape around the inner circle of the fan housing to increase CFM/static~pressure(SP mostly I think), made it so there was less of a gap between the blades and housing. he claimed an improvement :shrug: ...

Anyone found a source/price for those Papst 'Diagonal' fans with the huge S/P?...

jtroutma · 11-23-2002, 11:11 AM

I had great success sanding down my fan blades. I have a Sunon 120mm that is rated at 42dbls and I sanded both sides of the fins with 600 then 1500grit paper. ONLY useing the "ear" test, I would say that it droped to 40dbls, MAYBE 39 from just the sanding. It did make a NOTICEABLE difference for me.

Side rant:
Now if I could just get this damn Sedra to shut up I would be able to enjoy the extra silence of doing all that work!

gmat · 12-02-2002, 06:10 AM

Quote:

Originally posted by Alchemy
Link, please?

Alchemy

http://www.silentpcreview.com/module...rtid=25&page=1

utabintarbo · 12-02-2002, 07:43 AM

Quote:

Originally posted by MadDogMe
Yeah can you dig out a link BB please?...

I read where somedude put tape around the inner circle of the fan housing to increase CFM/static~pressure(SP mostly I think), made it so there was less of a gap between the blades and housing. he claimed an improvement :shrug: ...

...

Look HERE.

bigben2k · 12-02-2002, 09:38 AM

Hey, thanks guys, I've been looking for that thing for ever!

Puzzdre · 12-03-2002, 03:49 PM

I sanded my 120 mm (LOUD!!!) Sunon, and gained nice results, but did anybody try to disassemble the fan and spray lacquer the impeller and insides of the fan housing? Two or more thin lacquer layers would also give the smooth blade surfaces with IMO less effort than sanding...

Anybody?

g.l.amour · 02-25-2003, 09:48 AM

i have one time disassembled a fan. not good. there is some sort of rubber band in a casing. once u disassemble it is nearly impossible to put the rubber band back in place.

TerraMex · 02-25-2003, 10:52 AM

Not true, i've desassembled most of my fans and put them back together with no major incidents.

The problem was that i took the impeller out and painted it. Big mistake in two points. One , some were evenly painted but it adds weight to the fan, so the engine has extra work to move. And another was not evenly painted (althou the color is even) , so there is a bit more paint on a side than another, and that causes the fan not to be balanced... and it vibrates alot, and added noise. Grrr. They do look good thou.

Now i avoid to paint any, and if i need one, i get those transparent ones with leds. Looks alot better . I've got 2 Sunon. Damn. They're like turbines or something, i bet if they could they'd take off.

My two cents are... sand the fins a little with a high grit , oil the rotor shaft , and ... use a rheobus (like me). No worrys. Dont use varnish or anything that adds a considerable weight to the fan. You'd have to make a uniform layer to keep it from vibrating and causing noise, and the weight will drop the performance of the fan.

PS :some painted fans here.

jtroutma · 02-25-2003, 04:40 PM

I seem to be having a slight problem that relates to this thread. My Sunon 120mm fan works fine and is quiet but it is starting to make a noise that is a bit on the irritating side. As my fiancee use to say, "it sounds like your computer is breathing..."

It purrs alont nicely then gives this "wurrring" sound then goes away. Comes back frequently. I have cleaned the unit and have blown out dust from inside the housing. Would oiling inside the housing prossibly get rid of that or is it just time to get a new fan?

TerraMex · 02-25-2003, 05:39 PM

Try to oil it. If it doesnt help, try to use some rubber pads on it. It might be some vibration that can be eliminated. If that fails, take it apart, clean it, oil it with one of those sprays that you can buy in autoshops, re-assemble it, and pray to your local deity . Else, get a new one. Cant say what it could be, i've got a few 10 year old 80mm fans from 386, 486 psu's and they are in almost perfect working order. Two of them are the painted ones (see above). Cant say they're very expensive (120mm fans), a got a couple 120mm for 8 bucks each (its cheap for Portugal, trust me).

gogo · 02-25-2003, 05:46 PM

I use sewing machine oil.

JSimmons · 04-22-2003, 12:21 PM

Do you have to disassemble the fans to oil them?

bigben2k · 04-22-2003, 12:24 PM

No, just peel off the label.

Boli · 05-27-2003, 06:54 PM

I have found the worst case of noise from fans was from turbulence… e.g. my PSU fan was making a terrible racket so I hacked off the grill at the back leaving the fan with a clear path venting the air out of my case… and you know what; nearly all of the noise vanished. OK it didn’t look the best but whose to notice if it is at the BACK of my case anyway.

gogo · 05-27-2003, 07:04 PM

I did that with all my PSU's.

Then I got a cat.

11-04-2002, 02:53 PM	#1
nmmnp Cooling Neophyte Join Date: Nov 2002 Location: West Bloomfield, MI Posts: 3	Is it all about the decibals Tried to search this out, but didn't see anything. Sorry if this has been covered before but I've seen a lot of discussion on fans and something still confuses me when the subject turns to quiet fans. I know that different bearings can make a difference, but when comparing the same style fans (i.e. ball bearing) is it all about the decibals? I have an 92m Enermax adjustable speed fan (supposedly 41-52 cfm @ 18-32 db but I've been told these specs are off). Should this be quieter than any other ball bearing fan with a higher db rating, or are there other factors I'm missing? Thanks

11-15-2002, 09:31 PM	#3
gogo Cooling Savant Join Date: Apr 2002 Location: AK Posts: 246	Personally I wouldn't say it was all about decibles. Esp. since it can be hard to judge volume levels reported by different manufacturers. They (fans) are generally tested in ideal conditions by themselves. and given a dB rating. I take many things into consideration mostly. My cat. I've had a few fans (mostly sunon) that at 5 or 7 volts must have put out some high pitched elec. noise cause they drove him nuts. I thought he was going insane until I happened to shut the computer down once while he was in the room. My wife. theres a tiny buzzing sound from the 90mm zalman at 5v or 7v. I can't hear it unless I'm right next to it, but my wife spent half a day tracing it out. She swore up and down it was moving around the house and mostly near the fridge. That was fun. Me. I'm sick of noise. I don't even like the sound of air moving against things. I had a fanless computer far a day, but my nerves got to me and I put the fans back in at 5v and 7v. __________________ Now, with Retsyn®

11-16-2002, 09:18 AM	#4
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	I'll chime in on this one. First of all, the noise comes from the fan blades striking the air, mostly. Some time back we had this discussion, and someone (dared to?!) tell me that I was wrong, until someone was kind enough to experiment with a fan. He recorded the noise, then clipped the fan blades and recorded it again. The noise was (mostly) gone. Now, the noise is going to depend a lot on the fan blade geometry: too pitched, and they'll be noisier than hell, too flat, and they won't move enough air. Someone understood this, and charted (from specs) all the fans he could find, into a nice cfm to noise ratio. The highest ratio unit is the most desirable, regardless of how much noise it makes at 12V, because it can be undervolted to an acceptable noise level, while delivering the highest airflow. That being said... this chart only included axial fans. There are other types of fans, like the squirrel cage blower, which are (theoretically) much quieter than any axial fan... __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

11-22-2002, 04:54 PM	#8
airspirit Been /.'d... have you? Join Date: Jul 2002 Location: Moscow, ID Posts: 1,986	Didn't somebody sand their fan blades and get quieter performance? I thought I read that somewhere, and Ben commented on it .... __________________ #!/bin/sh {who;} {last;} {pause;} {grep;} {touch;} {unzip;} mount /dev/girl -t {wet;} {fsck;} {fsck;} {fsck;} {fsck;} echo yes yes yes {yes;} umount {/dev/girl;zip;} rm -rf {wet.spot;} {sleep;} finger: permission denied

11-23-2002, 11:11 AM	#10
jtroutma Cooling Savant Join Date: Aug 2001 Location: SLO, CA Posts: 837	I had great success sanding down my fan blades. I have a Sunon 120mm that is rated at 42dbls and I sanded both sides of the fins with 600 then 1500grit paper. ONLY useing the "ear" test, I would say that it droped to 40dbls, MAYBE 39 from just the sanding. It did make a NOTICEABLE difference for me. Side rant: Now if I could just get this damn Sedra to shut up I would be able to enjoy the extra silence of doing all that work! __________________ Athlon64 X2 4200+ @ 2.5Ghz (250FSB x 10) OCZ VX 1GB 4000 @ 250FSB (6-2-2-2 timmings) DFI LANParty nForce4 Ultra-D SCSI Raid 5 x (3) Cheetah 15K HDDs LSI Express 500 (128MB cache) OCZ PowerStream 520W PSU ATI X850XT PE (Stock) DTEK WhiteWater + DTEK Custom Radiator Eheim 1250

11-04-2002, 03:21 PM	#2
g.l.amour Cooling Savant Join Date: Mar 2002 Location: on da case Posts: 933	well, if those specs are off, then there is no way in telling, is there? anyway, only a minority is running these large fans at the 12V they are supposed to be running at. so to continue... if there was some efficiency difference at full speed (eg different fans @ 12V, same cfm, unequal dba rating) i guess that difference would become very very very small once they are both running in the 5 - 7V range most of us are running those fans. the easiest way i have been able to tax a fan is to look at the amperage rating e.g for 120's smaller than 0.4A rating : +/- low noise larger than 0.4A rating : +/- delta style the enermax 120's are +/- 0.3A e.g for 80's smaller than 0.15A: +/- low noise .... e.g for 90's smaller than 0.20A: +/- low noise ....

11-16-2002, 01:19 PM	#5
bdunosk Cooling Neophyte Join Date: May 2001 Location: Cincinnati, OH Posts: 93	Not to post-crap, but if you chop the blades off a fan, haven't you just removed a huge load on the fan's motor? I personally can tell the difference between the motor noise and the noise from air turbulence on my 7-volted 120mm Panaflo H1A. The motor noise is usually a lot louder than the turbulence (usually, yes... I don't know why it sounds louder some times than others).

11-16-2002, 08:42 PM	#7
bdunosk Cooling Neophyte Join Date: May 2001 Location: Cincinnati, OH Posts: 93	Sounds like Gizzo's fan page. It's true that the highest CFM:dBa ratio is best, but the top fans don't move enough air for most applications. shrug

11-23-2002, 05:09 AM	#9
MadDogMe Thermophile Join Date: Aug 2002 Location: Just shut up ;) ... Posts: 1,068	Yeah can you dig out a link BB please?... I read where somedude put tape around the inner circle of the fan housing to increase CFM/static~pressure(SP mostly I think), made it so there was less of a gap between the blades and housing. he claimed an improvement :shrug: ... Anyone found a source/price for those Papst 'Diagonal' fans with the huge S/P?...

12-02-2002, 09:38 AM	#13
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	Hey, thanks guys, I've been looking for that thing for ever! __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

12-03-2002, 03:49 PM	#14
Puzzdre Cooling Savant Join Date: Aug 2002 Location: Croatia Posts: 969	I sanded my 120 mm (LOUD!!!) Sunon, and gained nice results, but did anybody try to disassemble the fan and spray lacquer the impeller and insides of the fan housing? Two or more thin lacquer layers would also give the smooth blade surfaces with IMO less effort than sanding... Anybody? __________________ 'Out of cheese error... ...please reboot the universe (press the GBL to continue)'

02-25-2003, 09:48 AM	#15
g.l.amour Cooling Savant Join Date: Mar 2002 Location: on da case Posts: 933	i have one time disassembled a fan. not good. there is some sort of rubber band in a casing. once u disassemble it is nearly impossible to put the rubber band back in place. __________________ yo soy un tiburón

02-25-2003, 10:52 AM	#16
TerraMex Cooling Savant Join Date: Nov 2002 Location: Portugal, Europe Posts: 870	Not true, i've desassembled most of my fans and put them back together with no major incidents. The problem was that i took the impeller out and painted it. Big mistake in two points. One , some were evenly painted but it adds weight to the fan, so the engine has extra work to move. And another was not evenly painted (althou the color is even) , so there is a bit more paint on a side than another, and that causes the fan not to be balanced... and it vibrates alot, and added noise. Grrr. They do look good thou. Now i avoid to paint any, and if i need one, i get those transparent ones with leds. Looks alot better . I've got 2 Sunon. Damn. They're like turbines or something, i bet if they could they'd take off. My two cents are... sand the fins a little with a high grit , oil the rotor shaft , and ... use a rheobus (like me). No worrys. Dont use varnish or anything that adds a considerable weight to the fan. You'd have to make a uniform layer to keep it from vibrating and causing noise, and the weight will drop the performance of the fan. PS :some painted fans here. __________________ "we need more cowbell." Last edited by TerraMex; 02-25-2003 at 03:18 PM.

02-25-2003, 04:40 PM	#17
jtroutma Cooling Savant Join Date: Aug 2001 Location: SLO, CA Posts: 837	I seem to be having a slight problem that relates to this thread. My Sunon 120mm fan works fine and is quiet but it is starting to make a noise that is a bit on the irritating side. As my fiancee use to say, "it sounds like your computer is breathing..." It purrs alont nicely then gives this "wurrring" sound then goes away. Comes back frequently. I have cleaned the unit and have blown out dust from inside the housing. Would oiling inside the housing prossibly get rid of that or is it just time to get a new fan? __________________ Athlon64 X2 4200+ @ 2.5Ghz (250FSB x 10) OCZ VX 1GB 4000 @ 250FSB (6-2-2-2 timmings) DFI LANParty nForce4 Ultra-D SCSI Raid 5 x (3) Cheetah 15K HDDs LSI Express 500 (128MB cache) OCZ PowerStream 520W PSU ATI X850XT PE (Stock) DTEK WhiteWater + DTEK Custom Radiator Eheim 1250

02-25-2003, 05:39 PM	#18
TerraMex Cooling Savant Join Date: Nov 2002 Location: Portugal, Europe Posts: 870	Try to oil it. If it doesnt help, try to use some rubber pads on it. It might be some vibration that can be eliminated. If that fails, take it apart, clean it, oil it with one of those sprays that you can buy in autoshops, re-assemble it, and pray to your local deity . Else, get a new one. Cant say what it could be, i've got a few 10 year old 80mm fans from 386, 486 psu's and they are in almost perfect working order. Two of them are the painted ones (see above). Cant say they're very expensive (120mm fans), a got a couple 120mm for 8 bucks each (its cheap for Portugal, trust me). __________________ "we need more cowbell."

02-25-2003, 05:46 PM	#19
gogo Cooling Savant Join Date: Apr 2002 Location: AK Posts: 246	I use sewing machine oil. __________________ Now, with Retsyn®

04-22-2003, 12:21 PM	#20
JSimmons Cooling Savant Join Date: Apr 2003 Location: 4-sided room with an exit going east, and an exit going south Posts: 392	Do you have to disassemble the fans to oil them?

04-22-2003, 12:24 PM	#21
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	No, just peel off the label. __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

05-27-2003, 06:54 PM	#22
Boli Cooling Savant Join Date: Apr 2003 Location: Blackburn / Dundee Posts: 451	I have found the worst case of noise from fans was from turbulence… e.g. my PSU fan was making a terrible racket so I hacked off the grill at the back leaving the fan with a clear path venting the air out of my case… and you know what; nearly all of the noise vanished. OK it didn’t look the best but whose to notice if it is at the BACK of my case anyway.

05-27-2003, 07:04 PM	#23
gogo Cooling Savant Join Date: Apr 2002 Location: AK Posts: 246	I did that with all my PSU's. Then I got a cat. __________________ Now, with Retsyn®

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