correctthemisbegotten
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- Joined
- Jul 11, 2025
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When people talk about fans, they always talk about the extremes. Which is quietest, which moves the most air, which has the highest pressure. etc. This is because people have misconceptions about fan designs that don't coincide with reality.
First and foremost you must understand that any given fan shape, size, thickness, will have a single speed at which it is most efficient.
It might be 892 RPM or it might be 2,446 RPM.
Efficiency means that a fan is producing the most airflow relative to its noise and power draw.
Now, the surprising thing about efficiency is that it means there are no fans that are better than others in a general sense.
Some fans are more efficient at lower RPM, some better at higher RPM, some better somewhere in between.
The physics of fans basically means that yes, they will almost always push more air the faster they are spun until the air behind the fan cavitates.
But, there will be a huge drop off in efficiency for most fans the faster they are spun.
The sad reality is that 99% of reviews that I see always look at the maximum performance and not the maximum efficiency.
Most home computer builders really want efficiency over performance because they value their hearing or being able to hear something other than the humongous whine of fans spinning at 5,000 RPM.
Since sound is additive it becomes louder when sound sources are added. However, it's not that simple to calculate. The basic rule is that if the sound is coherent the increase is an exact doubling (6db) and if it is incoherent it is 3db.
Since fans can as much as double their volume each time a fan is added to the mix anything above 40db is going to be an annoyingly loud since most cases have 3-5 fans in them.
The simple way of understanding this is to find out the advertised loudness of your fan, say, it's 35db. Now, you need to multiply the number of fans by 3 as your minimum SPL increase. So, if you plan on having 5 - 35db fans that means you will be adding at least 15db to the starting loudness of 35db which equals 50db in total. But, its likely that certain frequencies will often be coherent so some frequencies may increase as much as 30db.
Anyway, it would be great if online reviewers would focus less on the maximums and more on the efficiency since that wil actually be the problem that most of us would like to have solved.
Thaaaaanks...
First and foremost you must understand that any given fan shape, size, thickness, will have a single speed at which it is most efficient.
It might be 892 RPM or it might be 2,446 RPM.
Efficiency means that a fan is producing the most airflow relative to its noise and power draw.
Now, the surprising thing about efficiency is that it means there are no fans that are better than others in a general sense.
Some fans are more efficient at lower RPM, some better at higher RPM, some better somewhere in between.
The physics of fans basically means that yes, they will almost always push more air the faster they are spun until the air behind the fan cavitates.
But, there will be a huge drop off in efficiency for most fans the faster they are spun.
The sad reality is that 99% of reviews that I see always look at the maximum performance and not the maximum efficiency.
Most home computer builders really want efficiency over performance because they value their hearing or being able to hear something other than the humongous whine of fans spinning at 5,000 RPM.
Since sound is additive it becomes louder when sound sources are added. However, it's not that simple to calculate. The basic rule is that if the sound is coherent the increase is an exact doubling (6db) and if it is incoherent it is 3db.
Since fans can as much as double their volume each time a fan is added to the mix anything above 40db is going to be an annoyingly loud since most cases have 3-5 fans in them.
The simple way of understanding this is to find out the advertised loudness of your fan, say, it's 35db. Now, you need to multiply the number of fans by 3 as your minimum SPL increase. So, if you plan on having 5 - 35db fans that means you will be adding at least 15db to the starting loudness of 35db which equals 50db in total. But, its likely that certain frequencies will often be coherent so some frequencies may increase as much as 30db.
Anyway, it would be great if online reviewers would focus less on the maximums and more on the efficiency since that wil actually be the problem that most of us would like to have solved.
Thaaaaanks...
