Acoustic Samples: Listen to this Heatsink!
When the Zalman CNPS9500 AT heatsink powers up to its full speed of 2650RPM after about 5 seconds of running in its quietest mode, noise levels become audible (53.5 dBA) but not exceedingly loud. The 4-pin PWM fan will do this whenever it is connected to a 3-pin motherboard fan header. When a motherboard with a PWM CPU fan header is used, the BIOS takes control of the fans' speed and scales it as temperatures in the CPU rise.
Nothing quite compares to listening to the actual noise created by a heatsink in operation. To do that, click on the little headphones icon below and play the sample MP3 files for the heatsink running with its fan at full speed.
Sound Level Measurements: Which Heatsink is Quietest?
Listening to the actual noise a heatsink makes allows you to hear what pure numbers alone cannot get across. To further emphasize FrostyTech's reliance on cold hard facts when evaluating a heatsink, we also take noise level measurements with a sound level meter.
With its 92mm fan spinning at the full 2650RPM, the Zalman CNPS9500 AT heatsink produces about 53.5 dBA noise. When it is connected to a PWM compatible motherboard, noise levels are reduced to as low as ~35 dBA. Frostytech was unable to produce results consistent with a fan speed of 1300RPM by reducing fan voltage (standard 3-pin fan speed controller), so the low speed fan measurements have been omitted from the official results. By way of comparison, other CNPS9500-class heatsinks generally make as little as 36 dBA when running at 1300RPM. Our attempts to adjust the PWM fan speed down resulted in noise levels of 27.5 dBA - indicating fan speed below minimum design criteria.
Surface Finish and Flatness
Surface finish is an important factor that we all look for when holding a new heatsink. Flipping a cooler over to see how well the base has been machined is a quick way to judge the attention to detail that was put into making it. The following test involves the use of a Surface Roughness Comparator, which offers a concise cross section common machine surface finishes.
The Zalman CNPS9500 AT heatsink has a surface roughness of approximately 12 microinches, which is considered very good. Next, let's see how this heatsink handles the heat compared to a selection of other heatsinks!
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