I published data I created with methods I’m happy with. My intent is to provide data that answers the question, what fan pushes the most air for the least amount of noise? I have begun to answer that question. Following is the graph from the bench for the Corsair ML210 and the Nidec Servo Gentle Typhoon.
Consider the blue, vertical line. The higher a fan is at 40 db(A), the more efficient it is. That is to say, it moves more air given the same noise level. In this case, the Corsair ML120 is superior.
Now consider the green, horizontal line. The farther to the right a fan is at 40 m^3/h, the less efficient it is. That is to say, it creates more noise to move the same amount of air.
The line segments also reflect the fan’s effective minimum and maximum airflow and noise. The ML120’s minimum airflow is slightly higher than the Gentle Typhoon, but it creates the airflow with much less noise. On the other hand, the ML120’s maximum airflow is much higher than the Gentle Typhoon’s, but it also creates much more noise. Furthermore, the ML120 is much more versatile, as its ranges both in noise and airflow are much greater than the Gentle Typhoon’s.
The lines aren’t perfect, but they are a decent general guide for how good a fan is. The following shows the actual data points used to create the line using least squares regression as implemented by Apache Commons Math. Each point is the average of three sound level measurements and about ten seconds of airflow.
Does this mean that the Gentle Typhoon is an inferior fan in every way? Not necessarily. At maximum load, it uses 22% less power than the ML120: 0.14 Amperes instead of 0.18. One fan might be more reliable than the other, or have benefits in a particular application due to its design.
Lastly, my measurements do not predict if a fan will behave poorly with the surface you are going to attach it to. One fan might have excellent efficiency according to my measurements and then have a terrible resonance with your PC case, whereas a fan that was worse for me might not cause the same resonance for you. For instance, the ML120 feels less balanced than the Gentle Typhoon. My working surface resonated with the ML120 very strongly compared to other fans. It motivated me to greatly increase the amount of foam and cloth I used between my sound meter and working surface. I don’t want to bias my results in favor of fans that just happen to not resonate for the table I’m working on.
Back to my original question. Of the four fans I currently have data for, which is the most efficient? Interestingly, it’s the Gentle Typhoon. It provides 1.51 m^3/h/db(A). The Noctua NF-A12x25 is close at
1.49 1.41 m^3/h/db(A). Given the limitations of my measurements, they’re the same. What sets them apart however isn’t the efficiency but the baseline amount of airflow. For the same amount of noise, the NF-A12x25 pushes 16% more air.
If you know what these fans look like you might predict they would behave similarly.
This leads to more questions, but I’m going to leave them unanswered:
- Is this fin style the most efficient for airflow per db(A)?
- Is fin design the most important factor in such efficiency?
- What is the difference between these two fans that makes their baseline airflows different?